CA2063103A1 - Systems for encoding and decoding data in machine readable graphic form - Google Patents
Systems for encoding and decoding data in machine readable graphic formInfo
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- CA2063103A1 CA2063103A1 CA002063103A CA2063103A CA2063103A1 CA 2063103 A1 CA2063103 A1 CA 2063103A1 CA 002063103 A CA002063103 A CA 002063103A CA 2063103 A CA2063103 A CA 2063103A CA 2063103 A1 CA2063103 A1 CA 2063103A1
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Abstract
ABSTRACT
A system for representing and recognizing data in machine readable graphic image form in which data to be encoded is entered into the system and a processor encodes the data into a two-dimensional bar code symbol and generates transfer drive signals representative of the symbol. A transferring device such as a printer transfers an image of the two-dimensional bar code symbol onto a carrier such as a card or paper document in response to the transfer drive signals. A recognition device converts the image on the carrier into electrical signals representative of the symbol by scanning the image. A low-level decoder decodes the signals by decoding each scan line into a vector of codeword values corresponding to the codewords in the two-dimensional bar code symbol, assigning a row number to each of the codeword values, and then filling in a two-dimensional matrix with the codeword values. A high-level decoder further decodes the codeword values into data which can then be output for processing or use.
A system for representing and recognizing data in machine readable graphic image form in which data to be encoded is entered into the system and a processor encodes the data into a two-dimensional bar code symbol and generates transfer drive signals representative of the symbol. A transferring device such as a printer transfers an image of the two-dimensional bar code symbol onto a carrier such as a card or paper document in response to the transfer drive signals. A recognition device converts the image on the carrier into electrical signals representative of the symbol by scanning the image. A low-level decoder decodes the signals by decoding each scan line into a vector of codeword values corresponding to the codewords in the two-dimensional bar code symbol, assigning a row number to each of the codeword values, and then filling in a two-dimensional matrix with the codeword values. A high-level decoder further decodes the codeword values into data which can then be output for processing or use.
Description
- 2~3~ ~3 BACKGROUND OF THE INVENTION
The present invention generally relates to the representation of data in machine xeadable form, and more particularly to a method and apparatus for encoding and decoding data into a two-dimensîonal grapnic image, such as the two-dimensional bar code PDF417, that can be au~omatically machine read to obtain the encoded data in both open and closed systems.
In today's high-technology world, more and more operations are being automatically performed by machines and systems. This ever-increa~ing drive for automation ha~ resulted in a demand for new techniques for encoding data into machine readable form for automatic entry into the various systems and machinery. The data ent7~ may be for such uses as data transmission, operating various machine functions or the identification of persons or items. The various media that carry the data for automatic ent~y include punch cards, magnetic tapes and discs and magnetic stripes on cards such as credit cards and badges. The systems utilizing the above carriers are in "clossd" systems, i.e., the read function is performed within an apparatus or housing and the reading element ' ' ~ ' .
. , .. . . , . -: -' 2~31~3 is in contact or in near-contact with the carrier means during ~he reading operation.
One method for representing data in a machine readable form is ~o encode the data into a pattern of indicia having parts of different light reflectivity, for example, bar code symbols. A
bar code symbol is a pattern comprised of a series of bars of --various widths and spaced apart from one another by spaces of various widths, the bars and spaces ha~ing different light reflective properties. The bars represent strings of binary ones and the spaces represent strings of binary zeros. Generally, the bars and spaces can be no smaller than a specified minimum width which is called a ~'module" or "unit." The bars and spaces are multiples of this module size or minimum width.
~ ar code symbol5 are typically printed directly on the object or on labels that a~e a~tached to the ob~ect. The bar code symbols are read by optical techniques, such as scanning laser beams or CCD cameras, and the resulting electrical signals are decoded into data representative of the symbol for further processing. Bar code reading systams are known as open~' systems in that the carrier while being read is not sealed, but is read from a distance and without being in physical contact with the scanner.
~ he conventional bar code described above is "one-dimensional" in that the info~mation encoded therein is represented by the width of the bars and spaces, which extend in a single dimension. Thus, a bar code of a supermarket item, for example, consists of a string o~ ele~en digits ~hich represent an , . ., . ~ ~ , . . ~ .. . . .... . . . . . .
2~3~03 identifying number, but not a description of the item. The remainder of the relevant information, such as the price, name of the product, manufacturer, weight, inventory data, and expiration date, must be obtained from a database using the identification number. Similarly, data encoded onto o~her mledia such as credit card magnetic stripes is composed of one or more "one dimensional~
tracks of encoded data.
The use of bar code symbols and magnetically encoded data has found wide acceptance in almost ev~ry type of industry. ~owever, the one-dimensional nature of the encoded data limits the amount of information that can be encoded and hence use has been generally restricted to simple digital representations.
There is an increasing need, however, or a system to encode data in machine readable form that allow~ for an increase in the amount of data encoded into a given space that can be quickly and easily decoded for further processing. In particulax, there is a desire to create ~'portable data files" which provide more than an identification number which is then used as an index to referenc2 a database. The ~portable data fila~l approach is well-suited to applica~ions where it is impractical to store item information in a database or where the database is not readily accessible when and where the bar code is read. For example, information such as the contents of a shipping mani~est or an equipment maintenance history could be carried dixectly on the ob~ect without requiring access to a remote database. Similarly, a hospital could use portable data files to put more~medical information on patient identification bracelets. In a manufacturing environment, . , .. , ~. ~-. ~ ,.. . . - - . . . . . .
2~631~3 portable data files could be used to keep production records or even to provide instructions to con~rol machine operations.
Ideally, such portable data files could contain up to several hundred or more characters in a relatively small area~ but still be read from a distance by a hand-held laser scanner.
One approach or increasing the information in machine-readable symbols i5 ~0 reduce the height of the bar codes and stack the bar codes one on top of each other to create a ~stacked~' or "two-dimensional~ bar code. A major problem in reading two-dimensional symbols, however, is the loss of vertical synchronization. As shown in Figure lA, if the data rows are too short or the scan line intersects the row at a large angle/ the scan lines will not coincide with the horizontal lines of the pattern. The height of the rows can be increased as shown in Figure lB, but this causes an obvious reduction of in~ormation density.
A proposed solution to the vextical synchronization problem is to include both row identifiers and local row discriminators in the two dimensional bar code symbol in order to distinguish between the rows. One such two-dimensional bar code with row identifiers and local row discriminators is PDF417, which was developed by S~mbol Technologies, Inc. A more complete description of PDF417 is contained in U.5. Patent Application Sèrial No. 0~ ~ 1,881r~iled January 5~ 1990, and assigned to the same assignea as the present inven~ion, which is hereby incorporated by reference.
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2~3~33 Even if ~he symbol is constructed so tha~ the rows can be distinguished from one another, however, there xemains the problem of how to decode such a symbol sficiently. In particular, it is no-t enough for a decoding me~hod or apparatus to simply recognize that a scan line crossed a row boundary.
SI~MARY OF_THE INVENTION
Accordingly, the present invention is direGted to a system for representing and recognizing data in machine readable graphic image form having an incrPased capacity for encoded information that can be used in both open and closed systems. The system comprises an encoding means having a means for entering data such as a keyboard or optical character ~canner. In addition, the data may be obtained directly from computer files. Tha data entered into the system may be both textual data and control data. The data is entered into a processing means or encoding the data into a two-dimensional pattern of graphic indicia.
The graphic indicia may, for example, be in the form of a two-dimensional bar code which is comprised of a pattern of vertical bars of pxedetermined lengths that are spaced at various vertical and horizontal intervals. The two-dimensional bar code sym~ol, which may be a PDF417 3~mb01, pxeerably includes a plurality o ordered, ad-jacent rows of codeword~ o bar-coded information from a set of codeword~, the set of codewords being partitioned into at least three mutually exclusive clu~tersj each row in the symbol having at lea~t one row indicator codeword and containing only codewords from a cluster different from the . . . .~, ., ... ~ -- . ; . - . - , ";
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2~3:~3 codewords in an adjacent row. It shoul~ be understood, however, that the graphic indicia representative of the data is not limited to two-dimensional bar codes such as PDF417, but may be in the form of any two-dimensional graphic pattern of indicia suitable for encoding data.
The processing means generates electrical drive signals for transferring the two-dimensional graphic pattern onto a d~ta carrier means, that may be a card or document or the surface of a machine part. The encoding means also includes means for transferring an image of the ~wo-dimensional pattPrn of graphic indicia onto the data carrier means in response to the transfer drive signals. ~he image may for example be printed in the form of a two-dimensional pattern of graphic indicia having different areas of light reflectivity in which the indicia have one level of reflectivity and the spaces have another level of reflectivity.
In this embodiment, the converting means may be a type of optical scanner typically used for scanning one-dimensional bar codes that converts the areas of different light reflectivity into electrical signals representative of the indicia. Scanners employed in the present invention, however, have the added feature of scanning the indicia in two dimansions. For example, in one me~hod a laser light beam is scanned across the indicia in a raster pattern for reading and decoding two-dimensional graphic codes. Optical scanners suitable for reading two-dimensional patterns are disclosed in U.S. Patent Application Serial Nos. 317,433 and 317,533, filed March 1, 1989, assigned to the same assignee as the present invention and incorporated herein by r~ference.
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The system of the present invention further includes recognition means comprising means for converting the image on the carrier means into electrical signals representative of the graphic indicia and means for decoding the electrical signals into output signals representative of the data.
Where the converting means is a hand-held laser scanner, in order to decode the electrical signals representing the graphic indicia efficiently, the decoding means should be able to decode the signal~ even though the scan lines cross a row boundary. In particular, whare ~he graphic indicia is a two-dimensional bar code symbol, such as PDF417, which has both row indicators and local row discriminators, the electrical signals obtained from scanning the symbol may be decoded in such a way that partial scans from different rows can be stitched together. This allows greater scanning angles and lower aspect ratios of the rows, which in turn makss possible hand-held la3er Rcanning of two-dimensional bar code symbols.
Accordingly, the decoding means for decoding the two-dimen ional bar code symbol, in accordance with the invention, compxises: means for scanning the two-dimensional bar code symbol to produce scan lines of data representing the bar-coded information in the codewords of the symbol; means for decoding a scan line of data into a vec~or of codeword values corresponding to the codewords that were scanned, at least one of the values being for a row indicator codeword; means for assigning a row number to each of the codeword values in the vector bassd on the value of th~ row indicator codeword and th2 clus~er of the .' ~
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codeword; and means for filling in a codeword matrix with the codeword values in the vector according to their assigned row numbers.
In a two-dimensional bar code symbol such as PDF417, the row indicator codewords may also contain information regarding the number of rows in the symbol and the number of codewords in each row. Where this is the case, one embodiment of the decoding means includes both means for decoding a scan line of data to obtain a codeword value for a row indicator codeword, and means for determining either ~he number of rows or ~he number of columns from the codeword value corre~ponding to a row indicator codeword.
The two-dimensional bar code symbol may also contain one or more error correction codewords. Another aspect o~ the decoding means o~ the invention therefore includes means or locating in the matrix the codeword values for any codewords that have not been successfully decoded, and means for correcting any erroneous codeword values in the codeword matrix using the error correction codeword.
The decoded output signals are available for further processing and the 3ystem may therefore include means for outputting the decoder output signals. TypicaL output devices may include a liquid cryskal display, a CRT display and a printer.
The outputted signals may also be transmitted to a computer or other system for further processing and use via telephone lines using a modem or via a data bus. The present invention contemplates the outputting of the decoder output signals to a microprocessor for controlling the operation o~ various machines _ g ., ..,,. ~.,, , ~, , .. - -, , :
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such as facsimile, VCR; microwave oven, robotic systems and weight/price label scale devices.
In another embodiment of the invention, the processing means encodes a first set of data into the two-dimensional pa~tern of graphic indicia and generates first transfer dri~e signals for transferring the two-dimensional pattern onto a carrier means.
The processing means also generates a second set of transfer drive signals in response to a second set of data entered into the system intended to be transferred to the carrier means in human readable iorm. Thereafter, the transfer means trans~ers onto ~he carrier means both the image of the two-dimensional graphic pattern of indicia in response to the first ~ransfer drive signals and the second set of data in human readable form in response to the second transfer drive signals. Thus, the system provides means for automatically representing data in both a machine readable foxm and human readabla foxm onto a single carrier means.
In yet another embodiment of the invention, the data is encoded and decoded using a keyed data encryption technique in order to increase the secuxity of the da~a transmission. In this embodiment, only the person haviny the encryption key will ~e able to decode the graphic pattern.
The ~ystem of the present invention maximizes the use of available space or encrypting da~a. In addition to being compact in size, the system provides fox high secuxity in tha transmission of information. Thus, ~he invention pro~ides a highly reliable system for representing da~a in machine readable graphic form having incxeased encoding capaci~y thereby substantially expanding _ 10 --.
, '' 2~3~3 applications for automatic data entry. In adclition, the invention creates a new media for man-machine interfacing.
It is to be understood that both th~ foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention as claimed.
The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate an embodiment of the invention and together with the gen~ral description, serve to explain the principles of the invention.
BRIEF DESCRIPTION OF TH~ DRAWINGS
Figures lA and lB are diagrams illustrating the intersection of scan lines with the rows of a two-dimensional bar code 9ymbol;
Figure 2 is a diagram illustrating one example of a codeword in PDF417;
Figure 3 is a diagram illustrating the overall structure of a PDF417 symbol;
Figure 4 i5 a table listing the number of error correction codewords for a given security level in PDF417;
Figure 5 i5 a block diagram of the ~ystem of the present invention;
Figure 6 is a psrspective view of an encoding means of the system of the present invention;
Figure 7 is a perspective view of a recognition means of the system of the present invention;
', 2~3~3 Figure 8 is a perspective view of a data entry device and reader in which a key may be entered for encrypting and decrypting data;
Figure 9 is a perspective view of a facsimile machine incorporating the recognition means of the present invention;
Figure 10 is a schematic diagram of another em~odimen~ of recognition means for scanning and decoding a two-dimensional bar code symbol;
Figure 11 is a schematic block diagram of an embodiment of the hardware apparatus of a low-level decoder for decoding a two-dimensional bar code symbol;
Figure 12 is a flow diagram of the steps performed by the low-level decoder for decoding a two-dimensional bar code symbol;
Figure 13 i~ a flow diagram of the steps performed by the low-level decoder for de~ermining the dimen~ions and security level of the symbol being scanned;
Figure 14 is a flow diagram of the steps performed by the low-level decoder for searching a scan line of data for a start or a stop pattern;
Figure 15 is a diagram illustrating the various width measurements that are used for the "t-sequence" of a codeword;
Figure 16 is a flow diagram of the steps performed by the low level decoder for decoding a scan line of data into a vector of codeword values and their cluster numbers;
Figures 17A, 17Br and 17C are diagrams showing an example of a codeword vector;
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~3 ~ ~3 Figure 18 is a flow diagram of the steps performed by the low-level decoder for decoding an individual codeword value and its cluster number from the scan line data; and Figures l9A and l9B together are a flow diagram of the steps performed by the low level decoder in order to update the codeword matrix using the codeword vector.
DESCRIP~ION OF_THE PREFERRED EMBODIMENTS
Reference will now be made in detail to the presently preferred embodiments of the invention, examples of which are illustratéd in the accompanying drawings.
Code PDF417 Before di~cussing the method and apparatus of the invention or encoding and decoding data in machine readable graphic form, such a~ the two-dimen~ional bar code PDF417, it i~ important to understand the structure of the two-dimensional bar code symbol itself.
Each PDF417 s~mbol is composed o~ a stack of rows of bar-coded information. ~ach row in the symbol consists of a start pattern, several s~mbol characters called "codewords,l' and a stop pattern. A codeword is the basic unit for encoding a value repre~enting, or associated with, certain numbers, letter~, or other symbols. Collectively, the codewords in each row ~orm data columns.
Both the numbex of rows and the number of data columns of the PDF417 symbol are vaxiable. The s~mbol must have at least three ' ' rows and may have up to ninety rows. Likewise, within each row, the number of codewords or data columns can vary from three to thirty.
Each PDF417 codeword consists of seventeen modules or units.
There are four bars and four spaces in each codeword. Individual bars or spaces can vary in width from one to six modules, but the combined total per cod~word is always seventeen modules. Thus, each codeword can be defined by an eight-digit sequence, which represents the four sets of alternating bar and space widths within the codeword. This is called the "X-sequence" of the codeword and may be represented by the sequence Xo,Xl,...X7. For example, for an X-se~uence of "51111125", the first element is five modules wide, followecl by five elements one module wide, one element two modules wide, and the last element five modules wide.
This example is illustrated in Figure 2.
The set o possible codewords is further partitioned into three mutually exclusive subsets called "clusters." In the PDF417 symbol, each row uses only one of the three clusters to encode data, and each cluster repeats sequentially every third row.
Because any two adjacent rows use different clusters, the decoder is able to discrimina~e between codewords from diferent rows within the same scan line.
The cluster number of a codeword may be detexmined from its X-sequence using the following formula:
cluster number = (XO - X2 ~ X4 - X~) mod 9 - ~ ' ' ' ~3~
where ~mod 9" is the remainder after division by nine. Referring to the codeword in Figure 2, the cluster number is calculated as ~ollows:
cluster number = (5 - 1 + 1 - 2~ mod 9 = 3 To minimize error probabilities, PDF417 uses only three clusters, even though nine are mathematically possible. Thus, each row uses only one of the three clusters 0, 3, or 6, to encode data, with the same cluster repeating sequentially every third row. Row O codewords, for example, use cluster 0, row 1 uses cluster 3, and row 2 uses cluster 6, etc. In general, the cluster number may be determined ~rom the row number as follows:
clu~ter number - ((row number) mod 3) * 3 There are 929 codeword value~ defined in PDF417. These values are O through 928. Each cluster presen~s the 929 available values with distinct bar-space patterns so that one cluster cannot be confused with another.
Figure 3 is a block diagram showing the overall structure of a PDF417 symbol. Each row of the symbol consi~ts of a start pattern, a left row indicator codeword Li, data codewords di or error detection/correction codewords Ci, a right row indicator codeword Ri~ and a stop pattern. The minimum number of codewords in a row is three, including ~ha left row indicator codeword, at lea~t one da~a codeword, and ~he righ~ row indicator codeword.
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2~31~3 The right and left row indicator codewords, which are discussed further below, help synchronize the structure of the symbol.
The start and stop pa~terns identify where each row of the symbol begins and ends. PDF417 uses unique start and stop patterns. The start pattern, or left side of each row, has the unique pattern, or X-sequence, of ~81111113~. The stop pattern, or right side of each row, has the unique X-sequence of "711311121".
Every symbol contains one codeword (the first data codeword in row O) indicating the total number of codewords within the symbol, and at lea~t two error-detection codewords CO and Cl.
These two error-detection codewords together form a checksum which is two codewords long.
A PDF417 s~mbol can also encode data with error correction capability. The level of error correction capability, called the "security level," is selected by the user and ranges from O to 8.
This means, for example, that at level 6, a total of 126 codewords can be eithex missing or destroyed and the entire symbol can be read and decoded. Figure S is a table showing the relationship between the Recurity level of the PDF417 symbol and the number of error correction codewords Ci.
In addition to correcting or missing or destroyed data (known as ~erasures~)t PDF417 can also recover from misdecodes of codewords. Since it requires two codewords to re~over from a misdecods/ one to detect the error and one to correct it, a given security level can support half the number of misdecodas that it can of undecoded codewords.
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- 2~3~3 The row indicator codewords in a PDF417 symbol contain several key componen~s: row number, number of rows, number of data column~, and security level. Not every row indicator contains every component, however. The information is spread over several rows, and the pattern repeats itself every three rows.
The pattern for encoding the infoxmation in ~he row indicator codewords can be illustrated as follows:
Row 0: Lo (row #, # of rows) Ro (row #, # of col~unns3 Row 1: Ll (row ~, security level) Rl (row ~, # of rows) Row 2: L2 (row #, # of columns) R2 (row ~, security level) Row 3: L3 (row #, ~ of rows) R3 (row #, # of COl~LmI15 ) etc.
In other words, the left row indicator codeword Lo for the first row O contains the row number (O) and the total number of rows in the symbol. The right row indicator codeword Ro for row O
contains the row number (O) and the number of data columns in the symbol, and so on.
Encoding data into a PDF417 symbol is ~ypically a two-step proce~s. Fixst, data is converted into codeword values of O to 928, which xepresent the data. This is known as "high-level encoding.ll The values are then physically represented by particular bar-space patterns, which is known as "low-level encoding."
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2~3~3 En_odinq~Decodinq Sy~stem Referring now to Figures 5-7 in the drawings, Figure 5 is a block diagram of the system 10 of the present invention for representing and recognizing data in machine readable graphic image form. System lO includes an encoding means generally indicated by the reference numeral 12 and a recognition means generally indicated by the re~erence numeral 14. Encoding means 12 produces a carrier means 16 containing at least a two~
dimensional pattern of graphic indicia 18. Carrier means 16 may also contain human readable data 20. The two-dimensional pattern of graphic indicia on carrier means 16 is recoqnized by recognition means 14 to produce output signals representative of the data encoded into the pattern 18.
Data to be txansferred onto carrier means 16 is ontered by entering means 22 into the encoding means 12. The dat'~ en~ered by entering means 22 may be both the data to be encoded into the two-dimensional pattern of graphic indicia and the data to appear on carrier means 16 in human readable form. Processing means 24 encodes the set of data to appear in pa~tern 18 into a ~wo-dimensional pattern of graphic indicia and generates transfer drive signals for controlling the transfer of the indicia onko the carrier means 16. Transferring mean~ 26 transfers an image of the two-dimensional pattern of graphic indicia onto carrier means 16 in response to the transfer drive signals. If human readable data is also to be transferred onto carrier 16, the processing means 24 generates a second set of ~ransfer drive signals for controlling the transfer of the human readable data onto carrier 16. A
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' ' ', ~ ' 2~3~3 portion or all of the data to be encoded and the human readable data may be transferred from a storage memory in processing means 24 or other computer files rather than being entered by means 22.
The carrier means 18 shown in Figures 5, 6, and 7 is represented as being in the form of a card approximately the si~e of a credit card. This type of card is illustrative only as the carrier means 18 may be made of any material on which graphic indicia may be transferred to, such as paper, etc.
Recognition means 14 includes converting means 28 that converts the image on carrier means 16 into ~lectrical signals representative of ths graphic indicia. Decoding means 30 decodes the electrical signals into decoder output signals indicated at 32 that are representative of the data encoded into the pattern 18.
Figure 6 is a perspective view o one embodiment of encoding means 12. In ~his embodiment, the entering means 22 of Figure 5 i~ shown in form of a keyboard 32 for entering alphanumeric and graphic data into the encoding means 12. The embodiment of Figur0 6 is illustrative only as entering means 22 may take forms other than a keyboard such as an optical scanning means for scanning data directly from documen~s for entry into the encoding means 12.
Entering means 22 may also be in the form of various card readers in which magnetically encoded inormation i5 scanned and converted into electrical signals representative of the data.
Referring again to Figure 6, the processing means 24 of Figure 5 is shown in the form of a processor and display u~it 34.
The data entered by keyboard 32 is transmitted to the processor and display unit 34 for storage and processing. In addi~ion to 2~31~3 entering data, the keyboard 32 is also used for entering control commands to effect operation of the processor unit 34.
The data entered by keyboard 32 is displayed on display screen 36 and upon entry of a proper control command, is also stored in memory. The data to be encoded into the pattern of graphic indicia is stored in a first memory, in processor 34 and the data, if any, to be transferred in human readable form is stored in a second memory. Alternatively, ~he data may be stored in a separate portion of a single memory. Upon the appropriate control command from keyboard 32, the processor unit 34 encodes the data in the first memory into a two-dimensional pattern of graphLc indicia and generates first transfer drive signals representative o the data stored in the first memory. The processor unit 34 also generates second transfer drive signals representative of the data stored in the second memory.
The processor unit 34 is shown in Figure 6 as being coupled to a printer 38. The printer 38 is one form of the transferring means 26 of Figure 5. Printer 38 transfers an image of the two-dimensional pattern of graphic indicia on carrier means 18 in response to the first transfer drive signals and prints the second set of data in human readable form onto carrier means 18 in response to the second transfer drive signals. In one embodiment, the printer 38 prints the two-dimensional pattern in the form of graphic indicia ha~ing different areas o light raflectivity, such as the two-dimensional bar code described above. Printer 38 may take other forms such as a means for printing the two-dimensional pattern of graphic indicia with magnetic-ink. In such a device, . .
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The present invention generally relates to the representation of data in machine xeadable form, and more particularly to a method and apparatus for encoding and decoding data into a two-dimensîonal grapnic image, such as the two-dimensional bar code PDF417, that can be au~omatically machine read to obtain the encoded data in both open and closed systems.
In today's high-technology world, more and more operations are being automatically performed by machines and systems. This ever-increa~ing drive for automation ha~ resulted in a demand for new techniques for encoding data into machine readable form for automatic entry into the various systems and machinery. The data ent7~ may be for such uses as data transmission, operating various machine functions or the identification of persons or items. The various media that carry the data for automatic ent~y include punch cards, magnetic tapes and discs and magnetic stripes on cards such as credit cards and badges. The systems utilizing the above carriers are in "clossd" systems, i.e., the read function is performed within an apparatus or housing and the reading element ' ' ~ ' .
. , .. . . , . -: -' 2~31~3 is in contact or in near-contact with the carrier means during ~he reading operation.
One method for representing data in a machine readable form is ~o encode the data into a pattern of indicia having parts of different light reflectivity, for example, bar code symbols. A
bar code symbol is a pattern comprised of a series of bars of --various widths and spaced apart from one another by spaces of various widths, the bars and spaces ha~ing different light reflective properties. The bars represent strings of binary ones and the spaces represent strings of binary zeros. Generally, the bars and spaces can be no smaller than a specified minimum width which is called a ~'module" or "unit." The bars and spaces are multiples of this module size or minimum width.
~ ar code symbol5 are typically printed directly on the object or on labels that a~e a~tached to the ob~ect. The bar code symbols are read by optical techniques, such as scanning laser beams or CCD cameras, and the resulting electrical signals are decoded into data representative of the symbol for further processing. Bar code reading systams are known as open~' systems in that the carrier while being read is not sealed, but is read from a distance and without being in physical contact with the scanner.
~ he conventional bar code described above is "one-dimensional" in that the info~mation encoded therein is represented by the width of the bars and spaces, which extend in a single dimension. Thus, a bar code of a supermarket item, for example, consists of a string o~ ele~en digits ~hich represent an , . ., . ~ ~ , . . ~ .. . . .... . . . . . .
2~3~03 identifying number, but not a description of the item. The remainder of the relevant information, such as the price, name of the product, manufacturer, weight, inventory data, and expiration date, must be obtained from a database using the identification number. Similarly, data encoded onto o~her mledia such as credit card magnetic stripes is composed of one or more "one dimensional~
tracks of encoded data.
The use of bar code symbols and magnetically encoded data has found wide acceptance in almost ev~ry type of industry. ~owever, the one-dimensional nature of the encoded data limits the amount of information that can be encoded and hence use has been generally restricted to simple digital representations.
There is an increasing need, however, or a system to encode data in machine readable form that allow~ for an increase in the amount of data encoded into a given space that can be quickly and easily decoded for further processing. In particulax, there is a desire to create ~'portable data files" which provide more than an identification number which is then used as an index to referenc2 a database. The ~portable data fila~l approach is well-suited to applica~ions where it is impractical to store item information in a database or where the database is not readily accessible when and where the bar code is read. For example, information such as the contents of a shipping mani~est or an equipment maintenance history could be carried dixectly on the ob~ect without requiring access to a remote database. Similarly, a hospital could use portable data files to put more~medical information on patient identification bracelets. In a manufacturing environment, . , .. , ~. ~-. ~ ,.. . . - - . . . . . .
2~631~3 portable data files could be used to keep production records or even to provide instructions to con~rol machine operations.
Ideally, such portable data files could contain up to several hundred or more characters in a relatively small area~ but still be read from a distance by a hand-held laser scanner.
One approach or increasing the information in machine-readable symbols i5 ~0 reduce the height of the bar codes and stack the bar codes one on top of each other to create a ~stacked~' or "two-dimensional~ bar code. A major problem in reading two-dimensional symbols, however, is the loss of vertical synchronization. As shown in Figure lA, if the data rows are too short or the scan line intersects the row at a large angle/ the scan lines will not coincide with the horizontal lines of the pattern. The height of the rows can be increased as shown in Figure lB, but this causes an obvious reduction of in~ormation density.
A proposed solution to the vextical synchronization problem is to include both row identifiers and local row discriminators in the two dimensional bar code symbol in order to distinguish between the rows. One such two-dimensional bar code with row identifiers and local row discriminators is PDF417, which was developed by S~mbol Technologies, Inc. A more complete description of PDF417 is contained in U.5. Patent Application Sèrial No. 0~ ~ 1,881r~iled January 5~ 1990, and assigned to the same assignea as the present inven~ion, which is hereby incorporated by reference.
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2~3~33 Even if ~he symbol is constructed so tha~ the rows can be distinguished from one another, however, there xemains the problem of how to decode such a symbol sficiently. In particular, it is no-t enough for a decoding me~hod or apparatus to simply recognize that a scan line crossed a row boundary.
SI~MARY OF_THE INVENTION
Accordingly, the present invention is direGted to a system for representing and recognizing data in machine readable graphic image form having an incrPased capacity for encoded information that can be used in both open and closed systems. The system comprises an encoding means having a means for entering data such as a keyboard or optical character ~canner. In addition, the data may be obtained directly from computer files. Tha data entered into the system may be both textual data and control data. The data is entered into a processing means or encoding the data into a two-dimensional pattern of graphic indicia.
The graphic indicia may, for example, be in the form of a two-dimensional bar code which is comprised of a pattern of vertical bars of pxedetermined lengths that are spaced at various vertical and horizontal intervals. The two-dimensional bar code sym~ol, which may be a PDF417 3~mb01, pxeerably includes a plurality o ordered, ad-jacent rows of codeword~ o bar-coded information from a set of codeword~, the set of codewords being partitioned into at least three mutually exclusive clu~tersj each row in the symbol having at lea~t one row indicator codeword and containing only codewords from a cluster different from the . . . .~, ., ... ~ -- . ; . - . - , ";
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2~3:~3 codewords in an adjacent row. It shoul~ be understood, however, that the graphic indicia representative of the data is not limited to two-dimensional bar codes such as PDF417, but may be in the form of any two-dimensional graphic pattern of indicia suitable for encoding data.
The processing means generates electrical drive signals for transferring the two-dimensional graphic pattern onto a d~ta carrier means, that may be a card or document or the surface of a machine part. The encoding means also includes means for transferring an image of the ~wo-dimensional pattPrn of graphic indicia onto the data carrier means in response to the transfer drive signals. ~he image may for example be printed in the form of a two-dimensional pattern of graphic indicia having different areas of light reflectivity in which the indicia have one level of reflectivity and the spaces have another level of reflectivity.
In this embodiment, the converting means may be a type of optical scanner typically used for scanning one-dimensional bar codes that converts the areas of different light reflectivity into electrical signals representative of the indicia. Scanners employed in the present invention, however, have the added feature of scanning the indicia in two dimansions. For example, in one me~hod a laser light beam is scanned across the indicia in a raster pattern for reading and decoding two-dimensional graphic codes. Optical scanners suitable for reading two-dimensional patterns are disclosed in U.S. Patent Application Serial Nos. 317,433 and 317,533, filed March 1, 1989, assigned to the same assignee as the present invention and incorporated herein by r~ference.
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The system of the present invention further includes recognition means comprising means for converting the image on the carrier means into electrical signals representative of the graphic indicia and means for decoding the electrical signals into output signals representative of the data.
Where the converting means is a hand-held laser scanner, in order to decode the electrical signals representing the graphic indicia efficiently, the decoding means should be able to decode the signal~ even though the scan lines cross a row boundary. In particular, whare ~he graphic indicia is a two-dimensional bar code symbol, such as PDF417, which has both row indicators and local row discriminators, the electrical signals obtained from scanning the symbol may be decoded in such a way that partial scans from different rows can be stitched together. This allows greater scanning angles and lower aspect ratios of the rows, which in turn makss possible hand-held la3er Rcanning of two-dimensional bar code symbols.
Accordingly, the decoding means for decoding the two-dimen ional bar code symbol, in accordance with the invention, compxises: means for scanning the two-dimensional bar code symbol to produce scan lines of data representing the bar-coded information in the codewords of the symbol; means for decoding a scan line of data into a vec~or of codeword values corresponding to the codewords that were scanned, at least one of the values being for a row indicator codeword; means for assigning a row number to each of the codeword values in the vector bassd on the value of th~ row indicator codeword and th2 clus~er of the .' ~
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codeword; and means for filling in a codeword matrix with the codeword values in the vector according to their assigned row numbers.
In a two-dimensional bar code symbol such as PDF417, the row indicator codewords may also contain information regarding the number of rows in the symbol and the number of codewords in each row. Where this is the case, one embodiment of the decoding means includes both means for decoding a scan line of data to obtain a codeword value for a row indicator codeword, and means for determining either ~he number of rows or ~he number of columns from the codeword value corre~ponding to a row indicator codeword.
The two-dimensional bar code symbol may also contain one or more error correction codewords. Another aspect o~ the decoding means o~ the invention therefore includes means or locating in the matrix the codeword values for any codewords that have not been successfully decoded, and means for correcting any erroneous codeword values in the codeword matrix using the error correction codeword.
The decoded output signals are available for further processing and the 3ystem may therefore include means for outputting the decoder output signals. TypicaL output devices may include a liquid cryskal display, a CRT display and a printer.
The outputted signals may also be transmitted to a computer or other system for further processing and use via telephone lines using a modem or via a data bus. The present invention contemplates the outputting of the decoder output signals to a microprocessor for controlling the operation o~ various machines _ g ., ..,,. ~.,, , ~, , .. - -, , :
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such as facsimile, VCR; microwave oven, robotic systems and weight/price label scale devices.
In another embodiment of the invention, the processing means encodes a first set of data into the two-dimensional pa~tern of graphic indicia and generates first transfer dri~e signals for transferring the two-dimensional pattern onto a carrier means.
The processing means also generates a second set of transfer drive signals in response to a second set of data entered into the system intended to be transferred to the carrier means in human readable iorm. Thereafter, the transfer means trans~ers onto ~he carrier means both the image of the two-dimensional graphic pattern of indicia in response to the first ~ransfer drive signals and the second set of data in human readable form in response to the second transfer drive signals. Thus, the system provides means for automatically representing data in both a machine readable foxm and human readabla foxm onto a single carrier means.
In yet another embodiment of the invention, the data is encoded and decoded using a keyed data encryption technique in order to increase the secuxity of the da~a transmission. In this embodiment, only the person haviny the encryption key will ~e able to decode the graphic pattern.
The ~ystem of the present invention maximizes the use of available space or encrypting da~a. In addition to being compact in size, the system provides fox high secuxity in tha transmission of information. Thus, ~he invention pro~ides a highly reliable system for representing da~a in machine readable graphic form having incxeased encoding capaci~y thereby substantially expanding _ 10 --.
, '' 2~3~3 applications for automatic data entry. In adclition, the invention creates a new media for man-machine interfacing.
It is to be understood that both th~ foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention as claimed.
The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate an embodiment of the invention and together with the gen~ral description, serve to explain the principles of the invention.
BRIEF DESCRIPTION OF TH~ DRAWINGS
Figures lA and lB are diagrams illustrating the intersection of scan lines with the rows of a two-dimensional bar code 9ymbol;
Figure 2 is a diagram illustrating one example of a codeword in PDF417;
Figure 3 is a diagram illustrating the overall structure of a PDF417 symbol;
Figure 4 i5 a table listing the number of error correction codewords for a given security level in PDF417;
Figure 5 i5 a block diagram of the ~ystem of the present invention;
Figure 6 is a psrspective view of an encoding means of the system of the present invention;
Figure 7 is a perspective view of a recognition means of the system of the present invention;
', 2~3~3 Figure 8 is a perspective view of a data entry device and reader in which a key may be entered for encrypting and decrypting data;
Figure 9 is a perspective view of a facsimile machine incorporating the recognition means of the present invention;
Figure 10 is a schematic diagram of another em~odimen~ of recognition means for scanning and decoding a two-dimensional bar code symbol;
Figure 11 is a schematic block diagram of an embodiment of the hardware apparatus of a low-level decoder for decoding a two-dimensional bar code symbol;
Figure 12 is a flow diagram of the steps performed by the low-level decoder for decoding a two-dimensional bar code symbol;
Figure 13 i~ a flow diagram of the steps performed by the low-level decoder for de~ermining the dimen~ions and security level of the symbol being scanned;
Figure 14 is a flow diagram of the steps performed by the low-level decoder for searching a scan line of data for a start or a stop pattern;
Figure 15 is a diagram illustrating the various width measurements that are used for the "t-sequence" of a codeword;
Figure 16 is a flow diagram of the steps performed by the low level decoder for decoding a scan line of data into a vector of codeword values and their cluster numbers;
Figures 17A, 17Br and 17C are diagrams showing an example of a codeword vector;
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~3 ~ ~3 Figure 18 is a flow diagram of the steps performed by the low-level decoder for decoding an individual codeword value and its cluster number from the scan line data; and Figures l9A and l9B together are a flow diagram of the steps performed by the low level decoder in order to update the codeword matrix using the codeword vector.
DESCRIP~ION OF_THE PREFERRED EMBODIMENTS
Reference will now be made in detail to the presently preferred embodiments of the invention, examples of which are illustratéd in the accompanying drawings.
Code PDF417 Before di~cussing the method and apparatus of the invention or encoding and decoding data in machine readable graphic form, such a~ the two-dimen~ional bar code PDF417, it i~ important to understand the structure of the two-dimensional bar code symbol itself.
Each PDF417 s~mbol is composed o~ a stack of rows of bar-coded information. ~ach row in the symbol consists of a start pattern, several s~mbol characters called "codewords,l' and a stop pattern. A codeword is the basic unit for encoding a value repre~enting, or associated with, certain numbers, letter~, or other symbols. Collectively, the codewords in each row ~orm data columns.
Both the numbex of rows and the number of data columns of the PDF417 symbol are vaxiable. The s~mbol must have at least three ' ' rows and may have up to ninety rows. Likewise, within each row, the number of codewords or data columns can vary from three to thirty.
Each PDF417 codeword consists of seventeen modules or units.
There are four bars and four spaces in each codeword. Individual bars or spaces can vary in width from one to six modules, but the combined total per cod~word is always seventeen modules. Thus, each codeword can be defined by an eight-digit sequence, which represents the four sets of alternating bar and space widths within the codeword. This is called the "X-sequence" of the codeword and may be represented by the sequence Xo,Xl,...X7. For example, for an X-se~uence of "51111125", the first element is five modules wide, followecl by five elements one module wide, one element two modules wide, and the last element five modules wide.
This example is illustrated in Figure 2.
The set o possible codewords is further partitioned into three mutually exclusive subsets called "clusters." In the PDF417 symbol, each row uses only one of the three clusters to encode data, and each cluster repeats sequentially every third row.
Because any two adjacent rows use different clusters, the decoder is able to discrimina~e between codewords from diferent rows within the same scan line.
The cluster number of a codeword may be detexmined from its X-sequence using the following formula:
cluster number = (XO - X2 ~ X4 - X~) mod 9 - ~ ' ' ' ~3~
where ~mod 9" is the remainder after division by nine. Referring to the codeword in Figure 2, the cluster number is calculated as ~ollows:
cluster number = (5 - 1 + 1 - 2~ mod 9 = 3 To minimize error probabilities, PDF417 uses only three clusters, even though nine are mathematically possible. Thus, each row uses only one of the three clusters 0, 3, or 6, to encode data, with the same cluster repeating sequentially every third row. Row O codewords, for example, use cluster 0, row 1 uses cluster 3, and row 2 uses cluster 6, etc. In general, the cluster number may be determined ~rom the row number as follows:
clu~ter number - ((row number) mod 3) * 3 There are 929 codeword value~ defined in PDF417. These values are O through 928. Each cluster presen~s the 929 available values with distinct bar-space patterns so that one cluster cannot be confused with another.
Figure 3 is a block diagram showing the overall structure of a PDF417 symbol. Each row of the symbol consi~ts of a start pattern, a left row indicator codeword Li, data codewords di or error detection/correction codewords Ci, a right row indicator codeword Ri~ and a stop pattern. The minimum number of codewords in a row is three, including ~ha left row indicator codeword, at lea~t one da~a codeword, and ~he righ~ row indicator codeword.
:
2~31~3 The right and left row indicator codewords, which are discussed further below, help synchronize the structure of the symbol.
The start and stop pa~terns identify where each row of the symbol begins and ends. PDF417 uses unique start and stop patterns. The start pattern, or left side of each row, has the unique pattern, or X-sequence, of ~81111113~. The stop pattern, or right side of each row, has the unique X-sequence of "711311121".
Every symbol contains one codeword (the first data codeword in row O) indicating the total number of codewords within the symbol, and at lea~t two error-detection codewords CO and Cl.
These two error-detection codewords together form a checksum which is two codewords long.
A PDF417 s~mbol can also encode data with error correction capability. The level of error correction capability, called the "security level," is selected by the user and ranges from O to 8.
This means, for example, that at level 6, a total of 126 codewords can be eithex missing or destroyed and the entire symbol can be read and decoded. Figure S is a table showing the relationship between the Recurity level of the PDF417 symbol and the number of error correction codewords Ci.
In addition to correcting or missing or destroyed data (known as ~erasures~)t PDF417 can also recover from misdecodes of codewords. Since it requires two codewords to re~over from a misdecods/ one to detect the error and one to correct it, a given security level can support half the number of misdecodas that it can of undecoded codewords.
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- 2~3~3 The row indicator codewords in a PDF417 symbol contain several key componen~s: row number, number of rows, number of data column~, and security level. Not every row indicator contains every component, however. The information is spread over several rows, and the pattern repeats itself every three rows.
The pattern for encoding the infoxmation in ~he row indicator codewords can be illustrated as follows:
Row 0: Lo (row #, # of rows) Ro (row #, # of col~unns3 Row 1: Ll (row ~, security level) Rl (row ~, # of rows) Row 2: L2 (row #, # of columns) R2 (row ~, security level) Row 3: L3 (row #, ~ of rows) R3 (row #, # of COl~LmI15 ) etc.
In other words, the left row indicator codeword Lo for the first row O contains the row number (O) and the total number of rows in the symbol. The right row indicator codeword Ro for row O
contains the row number (O) and the number of data columns in the symbol, and so on.
Encoding data into a PDF417 symbol is ~ypically a two-step proce~s. Fixst, data is converted into codeword values of O to 928, which xepresent the data. This is known as "high-level encoding.ll The values are then physically represented by particular bar-space patterns, which is known as "low-level encoding."
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2~3~3 En_odinq~Decodinq Sy~stem Referring now to Figures 5-7 in the drawings, Figure 5 is a block diagram of the system 10 of the present invention for representing and recognizing data in machine readable graphic image form. System lO includes an encoding means generally indicated by the reference numeral 12 and a recognition means generally indicated by the re~erence numeral 14. Encoding means 12 produces a carrier means 16 containing at least a two~
dimensional pattern of graphic indicia 18. Carrier means 16 may also contain human readable data 20. The two-dimensional pattern of graphic indicia on carrier means 16 is recoqnized by recognition means 14 to produce output signals representative of the data encoded into the pattern 18.
Data to be txansferred onto carrier means 16 is ontered by entering means 22 into the encoding means 12. The dat'~ en~ered by entering means 22 may be both the data to be encoded into the two-dimensional pattern of graphic indicia and the data to appear on carrier means 16 in human readable form. Processing means 24 encodes the set of data to appear in pa~tern 18 into a ~wo-dimensional pattern of graphic indicia and generates transfer drive signals for controlling the transfer of the indicia onko the carrier means 16. Transferring mean~ 26 transfers an image of the two-dimensional pattern of graphic indicia onto carrier means 16 in response to the transfer drive signals. If human readable data is also to be transferred onto carrier 16, the processing means 24 generates a second set of ~ransfer drive signals for controlling the transfer of the human readable data onto carrier 16. A
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' ' ', ~ ' 2~3~3 portion or all of the data to be encoded and the human readable data may be transferred from a storage memory in processing means 24 or other computer files rather than being entered by means 22.
The carrier means 18 shown in Figures 5, 6, and 7 is represented as being in the form of a card approximately the si~e of a credit card. This type of card is illustrative only as the carrier means 18 may be made of any material on which graphic indicia may be transferred to, such as paper, etc.
Recognition means 14 includes converting means 28 that converts the image on carrier means 16 into ~lectrical signals representative of ths graphic indicia. Decoding means 30 decodes the electrical signals into decoder output signals indicated at 32 that are representative of the data encoded into the pattern 18.
Figure 6 is a perspective view o one embodiment of encoding means 12. In ~his embodiment, the entering means 22 of Figure 5 i~ shown in form of a keyboard 32 for entering alphanumeric and graphic data into the encoding means 12. The embodiment of Figur0 6 is illustrative only as entering means 22 may take forms other than a keyboard such as an optical scanning means for scanning data directly from documen~s for entry into the encoding means 12.
Entering means 22 may also be in the form of various card readers in which magnetically encoded inormation i5 scanned and converted into electrical signals representative of the data.
Referring again to Figure 6, the processing means 24 of Figure 5 is shown in the form of a processor and display u~it 34.
The data entered by keyboard 32 is transmitted to the processor and display unit 34 for storage and processing. In addi~ion to 2~31~3 entering data, the keyboard 32 is also used for entering control commands to effect operation of the processor unit 34.
The data entered by keyboard 32 is displayed on display screen 36 and upon entry of a proper control command, is also stored in memory. The data to be encoded into the pattern of graphic indicia is stored in a first memory, in processor 34 and the data, if any, to be transferred in human readable form is stored in a second memory. Alternatively, ~he data may be stored in a separate portion of a single memory. Upon the appropriate control command from keyboard 32, the processor unit 34 encodes the data in the first memory into a two-dimensional pattern of graphLc indicia and generates first transfer drive signals representative o the data stored in the first memory. The processor unit 34 also generates second transfer drive signals representative of the data stored in the second memory.
The processor unit 34 is shown in Figure 6 as being coupled to a printer 38. The printer 38 is one form of the transferring means 26 of Figure 5. Printer 38 transfers an image of the two-dimensional pattern of graphic indicia on carrier means 18 in response to the first transfer drive signals and prints the second set of data in human readable form onto carrier means 18 in response to the second transfer drive signals. In one embodiment, the printer 38 prints the two-dimensional pattern in the form of graphic indicia ha~ing different areas o light raflectivity, such as the two-dimensional bar code described above. Printer 38 may take other forms such as a means for printing the two-dimensional pattern of graphic indicia with magnetic-ink. In such a device, . .
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3 ~l ~ 3 magnetic indicia are deposited on the carrier material in a two-dimensional pattern that may be recognized by magnetic-ink recognition sensors.
Turning now to Figure 7, the recognition means 14 includes a card reader 40 which contains the converting means 28 and the decoding means 30 of Figure 5. The converting means 28 may be a bar code reader such as those disclosed in U.~. Patent Application Serial Nos. 317,433 and 317,533, assigned to the same assignee as the present invention and incorporated herein by reference. The readers disclosed in the above patent applications are open system devices designed to read an optically encoded two-dimensional bar code and to convert the light reflected from the pattern into electrical signals representative of the graphic indicia.
The card reader 40 ~ay also comprise a magnetic-ink recognition device for reading and decoding magnetically encoded data. These closed ~y~tem de~ices include a magnetic read head that senses ~he change in reluctance associated wi~h the presence of the magnetic-ink. The use of appropriate converting means that corresponds to ~he particular data encoding ~echnology employed is contemplated by the present invention.
The decoding means 30 decodes the electrical signals into output signals representative of the data encoded onto carrier means 18. The decoder output signals are outputted from the recognition unit 40 to various output means 42. Figure 7 depicts two examples of output devices, one being a display unit 44 and the other a printer 46. Display unit 44 may be any suitable display such as liquid crystal display or a C~T. The printer 46 - , . . . ., ~ .. . .. .
2~3~03 may be any print device such as a dot matrix printer, laser printer, etc.
The system of the present invention maximizes the use o~
available space for encrypting data. ~he density of the encoded data is such that for a two-dimensional bar code symbol, a minimum of about 1600 characters can be encoded into a space o~
approximately 5" x lJ2". In addition to being compact in size, the system provides for high security in the transmission of information. For example, a sensitive message may be encoded onto a document also containing non-sensitive material. This document, the same as any document, can be copied, transmitted by facsimile, etc., but only those with a recognition means of the present invention will be able to "read" the sensitive portion. The carrior means, being a single sheek o paper or a plastic credit card type o card, is an inexpensive read-only-memory Ytructure that facilitates data communication.
In another embodiment, the data may be encoded using a keyed --encryption algorithm that may be accessed only by an encryption key. As shown in Figure 8, the data entry means 47 contains the keyed algorithm and upon entry of the key 4g, the data will be encoded into a two-diniensional graphic pattern in a unique coniguration. The unique configuration can only be read by a reader 48 having the algorithm and only upon entry of the key 49 into the reader. Thus, a high degree of security may be provided with the keyed encryption embodiment.
In addition, the recognition unit 40 may al~o transmit the output ~ignals to a central processing unit locally or remotely, - . . . ., ~ . , . . ~ , . ... . .
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2~63 1 03 by ~or example a mcdem, for further use or processing by the CPU.
In this embodiment, the data encoded onto the carrier means 18 may be control data in the form of machine operating instructions for controlling a robotic system or to a security identification system for performing such functions as unlocX:ing doors. In connection with the use of the present invention in a robotic system, it is contemplated that the two-dimensional graphic pattern containing the control data be placed or printed directly onto a machine part or part holder. A scanner coupled to the machine tool reeds the pattern and -transmits the decoded instruction to the control computer which in turn controls the machining of the part in accordance with the control program.
Another example of the use of the present invention includes a microwave food container where the two-dimensional graphic pattern con~ains instructions automatically entering the recommended cooking sequence. A further use may be in connection with placing on roadway signs two-dimensional patterns containing geographic location information tha~ may be read by a scanner in passing vehicles for use with onboard computers.
The present inven~ion further contemplates the use of the system of the present invention to encode control data containing machine operating instructions on~o the carrier means in the form of tnachine readable graphic indicia that may be inserted into the machine to effect operation of the machine. Figure 9 is an example of a facsimile machine 50 in which a document 52 containing human readable data 54 and a ~wo-dimensional pattern of graphic machine readable indicia 56. The document 52 is inserted ,, , ' ' : ~
2~3~3 into the facsimile machine 50 the same as documents are normally inserted for transmission. The machine 50 contains a converting means for converting the two-dimensional image into electrical signals and a decoding means for decoding the signals into output signals operative to actuate the facsimile machine 50. The pattern 56 may contain such information as the phone number of the intended recipient of the memo 54 and the appropriat~ instructions for automatically entering the phone number and actuating the transmission process. Thus, where numerous messages are faxed to a particular recipient, a supply of paper containing the phone number of the recipient encoded in the two-dimensional graphic indicia machine readable format may be maintained by the sender.
The tra~smission of messages to that recipient will be facilitated by placing the message onto the pre-encoded paper and simply inserting the paper into the facsimile machine. In addition to simplifying and speeding the transmission process, the possibility of sending highly sensitive information to an incorrect party will also be eliminated.
, , 2~31~3 Scanninq/Decodin~ AP~aratus Referring now to Figure 10, there is illus~rated a further embodiment of the recognition means 14 for scanning and decoding graphic indicia in machine readable form, where that graphic indicia is in the form of a two-dimensional bar code symbol such as PDF417. As shown in Figure 10, the recogni.tion means 14 includes a host computer 112, which may ~e a personal computer, a low-level decoder 114, and a hand-held laser scanner 116. Scanner 116 uses a laser light beam 118 to scan a two--dimensional bar code symbol 120 in a raster pattern while a trigger 122 is pulled. A
laser scanner suitable for scanning a two-dimensional bar c:ode symbol is disclosed in U.SO Patent Application No. 07/317,433, filed March 1, 1989, and assigned to the same assignee as the present invention, which is hereby incorporated by reference.
Electrical signals from laser scanner 114 are transmitted to low-level decoder 114 where they are decoded into a matrix of codeword values corresponding to the rows and coLumns of the two-dimensional bar code s~ymbol. As explained in further detail below, low-level decoder 114 may be embodied in a computer program operating on a micro-computer separate from the host computer.
The low-level decoder is connected to the host computer by a standard interface, such as an ~S-232 interface, ~or transmitting the codeword values after they are decoded. Alternatively, the low-level decoder 114 may be embodied entirely in hardware, or a combination of a hardware and software, which is physically located in either the ~canner itself or ~he host compu~er.
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2 ~ Q 3 The matrix of codeword values from low-level decoder 114 is decoded into usable data by a high-level decoder, which may be embodied as a separate computer program operating on the host computer 112. For example, PDF417 has three predefined modes and nine reserved modes. The predefined modes are ~inary, EXC, and Numeric. In the Binary mode, each codeword c~ln encode 1.2 bytes.
In the EXC mode, the alphanumeric data can be encoded in double density ~i.e., two characters per code word), and in Numer.ic mode, the numeric data can be packed in almost triple density.
Therefore, the high-level decoder in host computer 112 will further decode the codeword values (0-928) from low-level decoder 114, depending on the mode, to obtain the actual data embodied in the symbol. The decoded data from the high~level decoder may then be used by a user application program also operating o~ the host computer 112.
Low-~evel Decoder Figure 11 is a schematic block diagram of one e~bodiment of the hardware apparatus of low-level decoder 114 shown in Figure 10. In this embodiment, the low-level decoder i8 primarily embodied in a computer program which is executed by a micro-computer separate from the host computer.
As shown in Figure 11, the low-level decoder includes a scanner interface 130 which receives the electrical signals from the scanner. The electrical signals from the scanner may be in the form of a digital signal which corresponds to the light and dark elements of the symbol as it is being scanned. Scanner 2~31~3 interface 130 converts the electrical signals into a sequence of integer v~lues representing the varying widths of the bars and spaces and stores them in a buffer area of a memory 134. In order to accomplish this, scanner interace 130 is connected to a central bus 132 to which the other hardware elements of the low-level decoder are also connected. Scanner interface 130 has direct memory access (DMA) capability which allows it to store the converted scanner data directly in the memory for decoding.
Low-level decoder also includes a central processing unit (CPU) 136 and a second interface 138 for communicating with the host compuker. The inter~ace to the host computer may be one or more standard interfaces such as an RS-232 interface.
Figure 12 is a flow chart showing the sequence of operation o~ the low-level decoder for decoding a two-dimensional bar code s~mbol such as PDE'417 into a matrix o~ codeword values. The various steps in the ~e~uence are embodied in a software computer program which is stored in memoxy 134 and executed by CPU 136 shown in Figure 11.
In the first step 150 in Figure 12, the low-level decoder initializes the scanner in~erface and initiates scanning o the symbol. The actual functions performed in this step will depend on the type of scanner and will involve various scanner dependent routines to initialLze the scanner interface and to sta.rt scanning.
In step 152, the low-level decoder a~tempts to determina ~he dimensions and the security level of ~he symbol being scanned~
SpecificalIy, this step determines the number of rows, the number _ 27 -. ~ ~ . , ,.. . . ~ ..
~31~3 of data columns, and the security level of the symbol from theleft and right row indicator codewords. These dimensions are ~hen used to initialize a two-dimensional codeword matrix and other related parameters for decoding the symbol. Each location in the matrix contains both a codeword value and an associated confidence weight, which are initially se~ to a null or empty value. If the dimens.ions and security level of the s~mbol cannot be det0rmined~
then the scan is abortedO This step will be di~cussed in further detail below in connection w.ith Figure 13.
Continuing in Figure 12, step 154 i~ the first ~tep in a control loop in which the rows of the two-dimensional bar code symbol are repeatedly scanned and the codeword values are filled into the codeword matrix. The steps of the control loop are each repeated until the number o codewords remaining in the matrix which have not been successfully decoded is small enough that rest of the matrix can be determined using the built-in error correction capability of the symbol. Thus, in step 154, if the number of codewords which ha~e not been successfully decoded is less than the error correction capability of the symbol based on the security level (see Figure 4), an attempt is made to correct the matrix using the error-correction codewords. If the attempted error correction is successful, then in step 156, the control loop i8 exited and scanning is terminated in step 158. Otherwi5e, if the attempted error corxection is not successful, then the following steps 160-164 are performed to try to decodQ additional codewords to fill in the matrix.
.
~3~0~
First, step 160 searches a scan line of data obtained from the buffer area of the memory for a start or a stop pattern. If either a start or a stop pattern is found, then in step 162, ~he low-level decoder attempts to decode as many codewords as possible from the scan line. Specifically, the scan line of data is parsed into individual codewords whose values and cluster numbers are placed in a codeword vector ready for incoxporation into the codeword matrix. Both steps 160 and 162 are discussed in further detail below in connection with Figures 14 and 16, respectively.
The codeword vector produced in step 162 is analyzed and then used to update the codeword matrix in step 164. In particular, step 164 assigns a confidence weight to each codeword ~alue depending on whether its nearest neighbors were also decoded. Row numbers are also assigned to each codeword value based on the left or right row indicator codewords and the corresponding cluster number ~or the codeword. If the scan line crosses a row boundary, the cluster numbers of the codewords can be used to determine the correck row number for each individual codeword. For example, if a decoded scan line has a left row indicator with row number 2, and the cluster numbers of the following codewords are 5, 0, O, 3, the codewords are accordingly placed in the following locations:
(row 2, column 1); (row 3, column 2); (row 3, column 3); and (row 4, column 4). In this way, a single scan line o~ data can contain codewords ~rom more than one row, which can then be stitched into the appropriate location in the codeword matrix. This step is discussed in further detail in connection with Figures 19A and 19B
below.
..
2~31~3 Figure 13 is a flow chart showing in greater detail the sequence of steps for determining the dimensions and securi~y level of a symbol as referred to in step 152 of Figure 12 above.
In the first step 170 of Figure 13, the low-level decoder searches a scan li.ne of data obtained from the buffer area of the memory for a start or a stop pattern. This step is t:he same as step 160 in Figure 12 and is discussed in further detai.l in connection with Figure 14 below.
Step 172 then decodes the first codeword immediately adjacent to either the start or stop pattern found in the previous step.
As shown in Figure 3, this codeword wilL be either a left or right row indicator codeword containing the row number and either the number of row~, the nllmber o~ data columns, or the securlty level o~ the symbol. If both a start and a stop pattern are ound, then both the left and the right row indicators are decoded. The sequence of steps for decoding an individual codeword are discussed further below in connection with Figure 18.
Continuing in Figuxe 13, in step 174 the particular dimension or security level encoded in the row indicator is extractecl from the codeword value and the cluster number determined in the previous step 172. For example, for a left row indicator codeword with a cluster number of 0, the number of rows is extractecl from the codeword value.
A confidence weight assigned to each of the dimensions and the security level is initially set ~o 0. Ste~s 176-184 update both the current value and the confidence weight of the dimension or security level extracted in ~hP previous step in the following ..
' , , , . . . , ... ... .. . . ' : '' .: . ' . ' , 2~31 03 way. First, th0 particular parameter, say the number of rows, is compared to the current value of the number of rows obtained from previous decodes. If the current value of the number of rows and the newly decoded value are the same, as determined in step 176, then the confidence weight assigned to the n~ber of rows is increased in step 178. If the current value 2~nd the newly decoded value are different, however, then the confidence weight is decreased in step 180. If the confidence weight assigned to the particular parameter is decreased below zero as determined ln step 182, then the newly decoded value is substituted for the current value and a new minimum weight is assigned to the parameter in step 184.
Step 186 determines whether the confidence weight for all three parameter3, i.e., number of rows, number of data columns, and security level, exceeds a predetermined threshold. If so, then the two-dimensional codeword matrix is initialized in step 188 based on the current values of the number of xows and the number of columns. The number of correctable errors may al90 be determined from the current value of the security level according to the table in Figure 4. If all three confidence weights do not exceed the threshold in step 186, however, then program control raturns to step 170 to begin searching for the start and stop patterns in a new scan line. Steps lrl0-184 are repeated until all three parameters have been successfully decoded with a high degree of confidence.
Figure 14 is a flow chart showing in greater detail the sequence of s~eps for searching a scan line of data for a start or -.
.
.. . . .
: ' . '' ' : .
, 2~3~3 stop pattern as referred to above in step 160 of Figure 12 and skep 170 of Figure 13~ Bxiefly, the search begins a~ the first location of an individual scan line of data obtained from the buffer area of the memory and is repeated at sequential locations until either a match is found or the length of the scan line is exceeded. When a ma~ch is found, an index is set to a location immediately following or preceding the pattern for decoding the adjacent code word.
As shown in Figure 14, the first step 200 sets an index to the location of the data elements in the scan line to "1", indica~ing the first da~a element or integer value of the scan line. This index i5 used to identiy the first element of each sequence o~ eight elements in the scan line for comparison to the start and stop patterns.
Step 202 is the first step of an iterative loop for searching the scan line from left to right for either a star~ or a stop pattern. In this step, if the current index is less than ~he length of the scan line, then the remaining steps are executed and the search continues. Once the index exceeds the length of the scan line, however, then the loop is exited and an indication is returned signifying that the search ~ailed and a start or stop pattern was not found.
Rather than using the X-sequence of codeword, the low-level decoder decodes a symbol by using l~edge to similar edge"
measurements to compensate for ink spreading which occurs when printing the symbols. Thus, in step 2G4, a raw "t-sequence" is obtained from the ~can line by adding pair~ of consecutive integer ' ' :' ' .. ,: '.
.
.
, , '', ' ' 2 ~ 0 3 values beginning at the location specified by the index.
Specifically, the r~w t-sequence, which corresponds to the seven width measurements kl,t~,...t7 shown in Figure 15, is calculated by adding pairs of ~he consecutive integer values Xo,Xl,...X7, representing the widths of the bars and spaces, as follows:
tl = xo + Xl t2 = Xl ~ X2 t3 = x2 + x3 etc.
A width W for the entire codeword is also calculated in step 204 by summing the eight integer values xO + xl + . . . + X7.
For the codeword in Figure 15, for exampl.e, the sequence of integer values ~rom the ~can line, representing the widths of the bars and spaces might be something like: 43, 19, 21, 19, 22, 18, 1~3, 96. The raw t-sequence tl,t2,...t7 would then be 62, 40, 40, 41, 40, 121, l9q, and the width W would be 341.
In step 206 in Figure 14, the raw t-sequence obtained in step 204 is normalized and rounded to integer values. Specifically, a value for the codeword~s ~module~ or l'unit'~ is first established by dividing the width W of the codeword by the total number of units for each codeword. In a PDF417 symbol, each codeword is seventeen units, so that the width W is divided by ~eventeen to obtain the unit of the codeword. Thus t for the example in Figure 15, the unit would be (341/17) = 20Ø Each ~alue of the raw t-sequence is then divided by the unit and rounded to an integer to no~malize the t-sequence. The normalized t-sequence for the codeword in Figure lS is 3~ 2, 2, 2, 2, 6, 10.
\
- 33 - ~
. . . -: . .
.
:
-. .
, . . . : . . :
~0~31~3 The normalized t-sequence i5 then compared to the t-saquences of the start and stop patterns of the code in step 208. If the scanner scans from both left to right and right to left, then the t-sequence must be compared to the start and stop patterns in bo~h their normal and reverse orientations.
If there is a match in step 210, then the index is set in step 214 to a location in the scan line immediately following the pattern if it is a start pattern or i~mediately preceding it if it is a stop pattern. If the curren~ t-sequence does not match either the start or the stop pattern, however, then in step 212, the index is incremented by one and steps 202 through 210 are repeated until either a match is found or the length of the scan line is exceeded.
Figure 16 is a flow chart ~howing in greater detail the se~uence o~ steps for decoding a scan line of data into a vector o~ codewords and their clusters as referxed to in step 162 of Figure 12 above. In decodlng ~he individual codeword values and cluster numbers from the scan line, the low-level decoder begins decoding at the start or stop pattérn and decodes as many codewords possible~ For those codewords that are not successfully decoded, the codeword values in the codeword vector are set to '^ ~AD " .
At the completion of the sequence of steps shown in Figure 16, the codeword vector will contain certain codeword values and cluster numbers in locations corresponding to the appropriate columns of the codewords that were successfully decoded. Figure 17A shows an example of a codeword vector in which the codewords - 3~ -"' ' ' ' ' ' ' " ~ '' ' ' .
2~3~ ~3 in eight of the ten ~olumns were successfully decoded. The codeword values in columns 1 and 10 correspond to the left row indicator codeword in row 2 (L2) and the right row indicator codeword in row 1 (Rl), respectively. The codewords in columns 5 and 7 were not successfully decoded as indicated by the notation "BAD" in ~hose locations of the codeword vector.
Returning to the first step 220 of Figure 16, an upper limit on the number of codewords that may be decoded ("cwlimit") is set equal to the number of column5 in the codeword matrix. If this number of codewords is successfully decoded, then the decoding process for the current scan line ls obviously complete.
Step 2~2 determines the direction of the scan if the scanner scans from both left to right and right to left. If khe particular scan was from left to right as detenmined in step 222, then the column number of the first codeword is set to "1" in step 224 and the amount that it will incremented by ~"incr") each time a subsequent codeword is decoded is set to "+1". If the scan was from right to left, however, then in step ~26, the column number of the first codeword in the scan line will be the last column of the codeword matrix, and the incremental vaLue i9 set to "-l".
Step 228 is the first step of a control loop in which individual codeword values and their cluster numbers are decoded from the scan line of data. In step 228, the codeword limit is tested to see if it is still gre ter than zero. If not, then all of the codewords in the scan line have been decoded and the loop is exited.
, ' ~ ~ ' . . '.:
2~3~3~
Otherwise, step 230 obtain6 the next codeword value and its cluster number from the scan line. This step will be discussed in further detail below in connection with Figure 18.
If the codeword decoded in the previous step is a valid codeword as determined in step 232, then in ~t:ep 234 the codeword value and its cluster number are saved in the codeword vector at a location corresponding to the column of the codeword. The codeword values thus placed in the codeword vector are reacly for incorporation into the codeword matrix.
If the codeword decoded in step 230 is not a valid codeword, however, then the codeword value in the codeword vector corresponding to the current column is se~ to "BAD" in step 236 to indicate tha~ this codeword was not successfully decoded. A ~BAD~
codeword is most likely to occur when the ~can line crosses the boundary between two rows in the middle of the codeword.
Finally, in step 238, the current column number is either incremented or decremented depending on the direction of the scan, and the codeword limit is decremented by one. Steps 228-236 are then repeated until there has been an attempt to decode all of the codewords in the scan line.
Figure 18 is a flow chart diagram showing the sequence of step~ corresponding to step 230 in Figu.re 16 and step 172 in Figure 13 in which an attempt is made to decode an individual codeword value and cluster number from the scan line. In the fixst step 240, a raw t-sequence and the width W are obtained from the scan line. This same step was discussed previously in connection with step 204 in Figure 14.
2~1~3~3 In step 242, the width W of the eight elements presumed to be the next codeword are compared to the width of the pre~iously decoded codeword. If the current width W is not within a range o F
plus or minus a predetermined difference (delta), th~n there is probably a split ~undercount by a multiple of two elements) or a merge (overcount by a multiple of two element:s) error in the current codeword. This codeword is not decoded further, but rather in step 244 its value and cluster numher are both set ~o BAD to indicate that it could not be decoded.
Then in step 246, an attempt is made to resynchronize to the boundary o the next codeword by finding a t-sequence with a corresponding width ~ that falls with.in a given tolerance of the expected width of a codeword, basèd on the wid~h o~ the previous codeword. I~ the current width W i9 significantly greater than the expected width, indicating a po~sible merge error, then the last two integer values are dropped from the t-sequ~nce until it falls within the proper limits. Likewise, if the curxent wldth W
is significantly less than the expected width, indicating a possible split error, the next two integer values in the scan line are added to the t-sequence until it falls within the proper limi~s.
If the current width W is within a certain tolerance of the expected width, as determined in ~tep 242, then an attempt is made to decode the codeword. In step 248, ~he raw t-sequence is normalized as described above in connection with step 206 in Figure 14. Then in step 250, ~he cluster number is determined from the normalized t-~equence. The cluster number may bs .. - ~ .
.
2~31 ~3 determined from the t-sequence (as opposed to th~ X-sequence described above) as follows-cluster number = (Tl - T2 + T5 - T6) mod 9 For codewords in PDF417, valid cluster mImbers are 0, 3, and 6. I~ in step 252 it is determined that the cluster number is not 0, 3, or 6, then the codeword is not valid. Accordingly, in step 254 the cluster number and value are set to ~BAD~ to indicate that the codeword was not successfully decoded.
Otherwise, in step 256, the normalized t-sequence and its cluster number are used to find the corresponding codeword value in a look-up table. If no corresponding codeword val~e is found for th~ t-sequence, then the codeword ~alue i9 ~et to ~'BAD~ to indicate that it was not succe~sfully decoded.
Finally, in step 258 the "last width" value is updated to the current width W of the codeword for use in decoding the next codeword value from the scan line.
Figures 19A and l9B together comprise a flow chart of the sequence of steps executed by the low-level decoder in order to update the codeword matrix using the codeword vector. These figure~ explain in greater detail step 164 in Figure 12 discussed previou~ly.
The first step 260 of Figure l9A checks the first and la~t values in the codeword vector to see i~ either is a valid row indicator. If neither the first nor the last values in the codeword vector are valid row indicatoxs, then in step 262, the ' ~ ., ', , 2~$3~3 program exits the routine and no attempt is made to update the codeword matrix using the codeword vector.
If a valid row indicator is present, howe~er, then in step 264 confidence weights are as~igned to each codeword value in the codeword vector~ Specifically, a confidence weight is assigned to each cod~word depending on whether its nearest neighbors and their cluster were also decoded. For example, as shown in ~igure 17B, the codeword ~alues in columns l, 2, 3, 9, ancl lO are assigned high confidence weights ("H") because their in~ediate neighbors were also successfully decoded and have the same cluster number.
The codeword values for columns 4 and 8 are assigned medium confidence weights ("M") because one of their neighbors was successfully decoded and has the same cluster number but the other neighboring codeword value is ~BAD". The codeword value in column 3 is assigned a very low confidence weight ("L") because neither o~ its neighbors was succe3s~ully decoded. Thus, the confidence weight for a codeword value at column i in the codeword vector is essentially a function of ~he cluster numbers of the codewords at columns i - 1, i, and i + l. This function may be implemented by a look-up table whos0 index is calculated from the cluster numbers of the three codewords.
In step 266, a row number is assigned to each codeword value in the codeword vector based on the row indicator codewords and the cluster numbers. As shown in the example in Figure 17C, the left row indicator codeword L2 indicates that the row number is 2 and the cluster number is 6. The cluster numbers for the codeword values in columns 2-4 are also 6. Therefore, row number 2 is - ~ . , , , " ~. . ..
~.
' 2 ~ 3 assigned to the codeword values in the first four columns of the codeword vector.
Also in the example in Figure 17C, columns six and 8-10 all have a cluster number of 3 and the right row indicator codeword R
indicates that the row number is 1. Therefore, it can be assumed that the scan line crossed the row boundaxy between row 2 and row 1 and the codeword values in columns 6 and 8-10 should be assi~ned to row 1.
Once the confidence weights and row numbers have been hssigned to each of the codeword values in the codewoxd vector, the codeword matrix is updated one codeword at a time. In step 26~, the column number C of both the codeword vector and the codeword mat,rix is set is initially set ~o "1". Step 270 is the first step of an Lterative loop which steps through the codewords in the codeword vector and uses them to update the corresponding codewords and their associated confidence weights in the codeword matrix. When the column number C exceeds the number of columns in step 270, then all of the codewords in the codeword vector have been processed and the routine ands.
For each codeword in the codeword vector, 5t2p 272 sets the row number R o the codeword matrix to ~he row number as~igned in step 266 to the codeword in the codeword vector at the location C.
Thus, for each codeword value in the codeword vec~or, there is a corresponding value in the codeword matrix at location [R,C].
Continuing in Figure l9B, step 274 determines whethex the cuxrent codeword value in location ~R,CI in the codeword matrix is the same a~ the corresponding codeword value in the codeword , .
2~3~3 vector at column C. If the values are the same, then in step 276, the confidence weigh~ assigned to the codeword value in matrix location [R,C] is increased by the confidence weigh~ of the corresponding codeword value in the codeword vector. If not, the confidence weight of the codeword value in the matrix is decreased by the confidence weight of the codeword valule in the vector in step 278.
If the confidence weight was decreased in step 278, then in step 280 that confidence weight is tested to see if it was decreased below zero. If the confidence weight is less than zero, then in step 282 the new codeword value in the codeword vector is substituted for the current codeword value in the corresponding location in the codeword matrix. The confidence weight assigned to the codeword value in ~he matrix is also changed to a positive value in step 284.
Finally, in step 286 the colu~n number C is incremented by 1 for processing the next codeword value in the codeword vector and program control is returned to step 270 for repeating steps 272 through 286 for all of the columns in the vector.
Returnin~ briefly to step 154 in Figure 12, each time after the codeword matrix has been ~illed in with the new vector of codewo.rd values and the confidence weights have been updated, an attempt is made to fill in the rest of the matrix using the built-in error correction capability of the symbol. The number and location of codewords which have not yet been successfully decoded may be determined by comparing the confidence weights assigned to each of the codeword values in the matrix with a predetermined . . , ~' ~ , ' .
2B63~3 threshold. Those values having confidence weights below the threshold are considered to not yet be decoded. If the numbe~ of codewords not yet decoded is less than the error correction capability of the symbol as determined by the security level, then an attempt is made to correct the matrixO
It will be apparen~ to those skilled in the art that various modifications and varia~ions can be made in the decoding me~hod and apparatus without departing from the scope or spirit of the invention. Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specifi.cation and practice of the invention disclosed herein. It is in~ended that the specification and examples bo considered as exemplary only, with a true scope and spiri.t of the invention being indicated by the following claims.
, . .
' ~
.:
Turning now to Figure 7, the recognition means 14 includes a card reader 40 which contains the converting means 28 and the decoding means 30 of Figure 5. The converting means 28 may be a bar code reader such as those disclosed in U.~. Patent Application Serial Nos. 317,433 and 317,533, assigned to the same assignee as the present invention and incorporated herein by reference. The readers disclosed in the above patent applications are open system devices designed to read an optically encoded two-dimensional bar code and to convert the light reflected from the pattern into electrical signals representative of the graphic indicia.
The card reader 40 ~ay also comprise a magnetic-ink recognition device for reading and decoding magnetically encoded data. These closed ~y~tem de~ices include a magnetic read head that senses ~he change in reluctance associated wi~h the presence of the magnetic-ink. The use of appropriate converting means that corresponds to ~he particular data encoding ~echnology employed is contemplated by the present invention.
The decoding means 30 decodes the electrical signals into output signals representative of the data encoded onto carrier means 18. The decoder output signals are outputted from the recognition unit 40 to various output means 42. Figure 7 depicts two examples of output devices, one being a display unit 44 and the other a printer 46. Display unit 44 may be any suitable display such as liquid crystal display or a C~T. The printer 46 - , . . . ., ~ .. . .. .
2~3~03 may be any print device such as a dot matrix printer, laser printer, etc.
The system of the present invention maximizes the use o~
available space for encrypting data. ~he density of the encoded data is such that for a two-dimensional bar code symbol, a minimum of about 1600 characters can be encoded into a space o~
approximately 5" x lJ2". In addition to being compact in size, the system provides for high security in the transmission of information. For example, a sensitive message may be encoded onto a document also containing non-sensitive material. This document, the same as any document, can be copied, transmitted by facsimile, etc., but only those with a recognition means of the present invention will be able to "read" the sensitive portion. The carrior means, being a single sheek o paper or a plastic credit card type o card, is an inexpensive read-only-memory Ytructure that facilitates data communication.
In another embodiment, the data may be encoded using a keyed --encryption algorithm that may be accessed only by an encryption key. As shown in Figure 8, the data entry means 47 contains the keyed algorithm and upon entry of the key 4g, the data will be encoded into a two-diniensional graphic pattern in a unique coniguration. The unique configuration can only be read by a reader 48 having the algorithm and only upon entry of the key 49 into the reader. Thus, a high degree of security may be provided with the keyed encryption embodiment.
In addition, the recognition unit 40 may al~o transmit the output ~ignals to a central processing unit locally or remotely, - . . . ., ~ . , . . ~ , . ... . .
- .
'' : ' , . . ' ' ,' ~
2~63 1 03 by ~or example a mcdem, for further use or processing by the CPU.
In this embodiment, the data encoded onto the carrier means 18 may be control data in the form of machine operating instructions for controlling a robotic system or to a security identification system for performing such functions as unlocX:ing doors. In connection with the use of the present invention in a robotic system, it is contemplated that the two-dimensional graphic pattern containing the control data be placed or printed directly onto a machine part or part holder. A scanner coupled to the machine tool reeds the pattern and -transmits the decoded instruction to the control computer which in turn controls the machining of the part in accordance with the control program.
Another example of the use of the present invention includes a microwave food container where the two-dimensional graphic pattern con~ains instructions automatically entering the recommended cooking sequence. A further use may be in connection with placing on roadway signs two-dimensional patterns containing geographic location information tha~ may be read by a scanner in passing vehicles for use with onboard computers.
The present inven~ion further contemplates the use of the system of the present invention to encode control data containing machine operating instructions on~o the carrier means in the form of tnachine readable graphic indicia that may be inserted into the machine to effect operation of the machine. Figure 9 is an example of a facsimile machine 50 in which a document 52 containing human readable data 54 and a ~wo-dimensional pattern of graphic machine readable indicia 56. The document 52 is inserted ,, , ' ' : ~
2~3~3 into the facsimile machine 50 the same as documents are normally inserted for transmission. The machine 50 contains a converting means for converting the two-dimensional image into electrical signals and a decoding means for decoding the signals into output signals operative to actuate the facsimile machine 50. The pattern 56 may contain such information as the phone number of the intended recipient of the memo 54 and the appropriat~ instructions for automatically entering the phone number and actuating the transmission process. Thus, where numerous messages are faxed to a particular recipient, a supply of paper containing the phone number of the recipient encoded in the two-dimensional graphic indicia machine readable format may be maintained by the sender.
The tra~smission of messages to that recipient will be facilitated by placing the message onto the pre-encoded paper and simply inserting the paper into the facsimile machine. In addition to simplifying and speeding the transmission process, the possibility of sending highly sensitive information to an incorrect party will also be eliminated.
, , 2~31~3 Scanninq/Decodin~ AP~aratus Referring now to Figure 10, there is illus~rated a further embodiment of the recognition means 14 for scanning and decoding graphic indicia in machine readable form, where that graphic indicia is in the form of a two-dimensional bar code symbol such as PDF417. As shown in Figure 10, the recogni.tion means 14 includes a host computer 112, which may ~e a personal computer, a low-level decoder 114, and a hand-held laser scanner 116. Scanner 116 uses a laser light beam 118 to scan a two--dimensional bar code symbol 120 in a raster pattern while a trigger 122 is pulled. A
laser scanner suitable for scanning a two-dimensional bar c:ode symbol is disclosed in U.SO Patent Application No. 07/317,433, filed March 1, 1989, and assigned to the same assignee as the present invention, which is hereby incorporated by reference.
Electrical signals from laser scanner 114 are transmitted to low-level decoder 114 where they are decoded into a matrix of codeword values corresponding to the rows and coLumns of the two-dimensional bar code s~ymbol. As explained in further detail below, low-level decoder 114 may be embodied in a computer program operating on a micro-computer separate from the host computer.
The low-level decoder is connected to the host computer by a standard interface, such as an ~S-232 interface, ~or transmitting the codeword values after they are decoded. Alternatively, the low-level decoder 114 may be embodied entirely in hardware, or a combination of a hardware and software, which is physically located in either the ~canner itself or ~he host compu~er.
. . .
2 ~ Q 3 The matrix of codeword values from low-level decoder 114 is decoded into usable data by a high-level decoder, which may be embodied as a separate computer program operating on the host computer 112. For example, PDF417 has three predefined modes and nine reserved modes. The predefined modes are ~inary, EXC, and Numeric. In the Binary mode, each codeword c~ln encode 1.2 bytes.
In the EXC mode, the alphanumeric data can be encoded in double density ~i.e., two characters per code word), and in Numer.ic mode, the numeric data can be packed in almost triple density.
Therefore, the high-level decoder in host computer 112 will further decode the codeword values (0-928) from low-level decoder 114, depending on the mode, to obtain the actual data embodied in the symbol. The decoded data from the high~level decoder may then be used by a user application program also operating o~ the host computer 112.
Low-~evel Decoder Figure 11 is a schematic block diagram of one e~bodiment of the hardware apparatus of low-level decoder 114 shown in Figure 10. In this embodiment, the low-level decoder i8 primarily embodied in a computer program which is executed by a micro-computer separate from the host computer.
As shown in Figure 11, the low-level decoder includes a scanner interface 130 which receives the electrical signals from the scanner. The electrical signals from the scanner may be in the form of a digital signal which corresponds to the light and dark elements of the symbol as it is being scanned. Scanner 2~31~3 interface 130 converts the electrical signals into a sequence of integer v~lues representing the varying widths of the bars and spaces and stores them in a buffer area of a memory 134. In order to accomplish this, scanner interace 130 is connected to a central bus 132 to which the other hardware elements of the low-level decoder are also connected. Scanner interface 130 has direct memory access (DMA) capability which allows it to store the converted scanner data directly in the memory for decoding.
Low-level decoder also includes a central processing unit (CPU) 136 and a second interface 138 for communicating with the host compuker. The inter~ace to the host computer may be one or more standard interfaces such as an RS-232 interface.
Figure 12 is a flow chart showing the sequence of operation o~ the low-level decoder for decoding a two-dimensional bar code s~mbol such as PDE'417 into a matrix o~ codeword values. The various steps in the ~e~uence are embodied in a software computer program which is stored in memoxy 134 and executed by CPU 136 shown in Figure 11.
In the first step 150 in Figure 12, the low-level decoder initializes the scanner in~erface and initiates scanning o the symbol. The actual functions performed in this step will depend on the type of scanner and will involve various scanner dependent routines to initialLze the scanner interface and to sta.rt scanning.
In step 152, the low-level decoder a~tempts to determina ~he dimensions and the security level of ~he symbol being scanned~
SpecificalIy, this step determines the number of rows, the number _ 27 -. ~ ~ . , ,.. . . ~ ..
~31~3 of data columns, and the security level of the symbol from theleft and right row indicator codewords. These dimensions are ~hen used to initialize a two-dimensional codeword matrix and other related parameters for decoding the symbol. Each location in the matrix contains both a codeword value and an associated confidence weight, which are initially se~ to a null or empty value. If the dimens.ions and security level of the s~mbol cannot be det0rmined~
then the scan is abortedO This step will be di~cussed in further detail below in connection w.ith Figure 13.
Continuing in Figure 12, step 154 i~ the first ~tep in a control loop in which the rows of the two-dimensional bar code symbol are repeatedly scanned and the codeword values are filled into the codeword matrix. The steps of the control loop are each repeated until the number o codewords remaining in the matrix which have not been successfully decoded is small enough that rest of the matrix can be determined using the built-in error correction capability of the symbol. Thus, in step 154, if the number of codewords which ha~e not been successfully decoded is less than the error correction capability of the symbol based on the security level (see Figure 4), an attempt is made to correct the matrix using the error-correction codewords. If the attempted error correction is successful, then in step 156, the control loop i8 exited and scanning is terminated in step 158. Otherwi5e, if the attempted error corxection is not successful, then the following steps 160-164 are performed to try to decodQ additional codewords to fill in the matrix.
.
~3~0~
First, step 160 searches a scan line of data obtained from the buffer area of the memory for a start or a stop pattern. If either a start or a stop pattern is found, then in step 162, ~he low-level decoder attempts to decode as many codewords as possible from the scan line. Specifically, the scan line of data is parsed into individual codewords whose values and cluster numbers are placed in a codeword vector ready for incoxporation into the codeword matrix. Both steps 160 and 162 are discussed in further detail below in connection with Figures 14 and 16, respectively.
The codeword vector produced in step 162 is analyzed and then used to update the codeword matrix in step 164. In particular, step 164 assigns a confidence weight to each codeword ~alue depending on whether its nearest neighbors were also decoded. Row numbers are also assigned to each codeword value based on the left or right row indicator codewords and the corresponding cluster number ~or the codeword. If the scan line crosses a row boundary, the cluster numbers of the codewords can be used to determine the correck row number for each individual codeword. For example, if a decoded scan line has a left row indicator with row number 2, and the cluster numbers of the following codewords are 5, 0, O, 3, the codewords are accordingly placed in the following locations:
(row 2, column 1); (row 3, column 2); (row 3, column 3); and (row 4, column 4). In this way, a single scan line o~ data can contain codewords ~rom more than one row, which can then be stitched into the appropriate location in the codeword matrix. This step is discussed in further detail in connection with Figures 19A and 19B
below.
..
2~31~3 Figure 13 is a flow chart showing in greater detail the sequence of steps for determining the dimensions and securi~y level of a symbol as referred to in step 152 of Figure 12 above.
In the first step 170 of Figure 13, the low-level decoder searches a scan li.ne of data obtained from the buffer area of the memory for a start or a stop pattern. This step is t:he same as step 160 in Figure 12 and is discussed in further detai.l in connection with Figure 14 below.
Step 172 then decodes the first codeword immediately adjacent to either the start or stop pattern found in the previous step.
As shown in Figure 3, this codeword wilL be either a left or right row indicator codeword containing the row number and either the number of row~, the nllmber o~ data columns, or the securlty level o~ the symbol. If both a start and a stop pattern are ound, then both the left and the right row indicators are decoded. The sequence of steps for decoding an individual codeword are discussed further below in connection with Figure 18.
Continuing in Figuxe 13, in step 174 the particular dimension or security level encoded in the row indicator is extractecl from the codeword value and the cluster number determined in the previous step 172. For example, for a left row indicator codeword with a cluster number of 0, the number of rows is extractecl from the codeword value.
A confidence weight assigned to each of the dimensions and the security level is initially set ~o 0. Ste~s 176-184 update both the current value and the confidence weight of the dimension or security level extracted in ~hP previous step in the following ..
' , , , . . . , ... ... .. . . ' : '' .: . ' . ' , 2~31 03 way. First, th0 particular parameter, say the number of rows, is compared to the current value of the number of rows obtained from previous decodes. If the current value of the number of rows and the newly decoded value are the same, as determined in step 176, then the confidence weight assigned to the n~ber of rows is increased in step 178. If the current value 2~nd the newly decoded value are different, however, then the confidence weight is decreased in step 180. If the confidence weight assigned to the particular parameter is decreased below zero as determined ln step 182, then the newly decoded value is substituted for the current value and a new minimum weight is assigned to the parameter in step 184.
Step 186 determines whether the confidence weight for all three parameter3, i.e., number of rows, number of data columns, and security level, exceeds a predetermined threshold. If so, then the two-dimensional codeword matrix is initialized in step 188 based on the current values of the number of xows and the number of columns. The number of correctable errors may al90 be determined from the current value of the security level according to the table in Figure 4. If all three confidence weights do not exceed the threshold in step 186, however, then program control raturns to step 170 to begin searching for the start and stop patterns in a new scan line. Steps lrl0-184 are repeated until all three parameters have been successfully decoded with a high degree of confidence.
Figure 14 is a flow chart showing in greater detail the sequence of s~eps for searching a scan line of data for a start or -.
.
.. . . .
: ' . '' ' : .
, 2~3~3 stop pattern as referred to above in step 160 of Figure 12 and skep 170 of Figure 13~ Bxiefly, the search begins a~ the first location of an individual scan line of data obtained from the buffer area of the memory and is repeated at sequential locations until either a match is found or the length of the scan line is exceeded. When a ma~ch is found, an index is set to a location immediately following or preceding the pattern for decoding the adjacent code word.
As shown in Figure 14, the first step 200 sets an index to the location of the data elements in the scan line to "1", indica~ing the first da~a element or integer value of the scan line. This index i5 used to identiy the first element of each sequence o~ eight elements in the scan line for comparison to the start and stop patterns.
Step 202 is the first step of an iterative loop for searching the scan line from left to right for either a star~ or a stop pattern. In this step, if the current index is less than ~he length of the scan line, then the remaining steps are executed and the search continues. Once the index exceeds the length of the scan line, however, then the loop is exited and an indication is returned signifying that the search ~ailed and a start or stop pattern was not found.
Rather than using the X-sequence of codeword, the low-level decoder decodes a symbol by using l~edge to similar edge"
measurements to compensate for ink spreading which occurs when printing the symbols. Thus, in step 2G4, a raw "t-sequence" is obtained from the ~can line by adding pair~ of consecutive integer ' ' :' ' .. ,: '.
.
.
, , '', ' ' 2 ~ 0 3 values beginning at the location specified by the index.
Specifically, the r~w t-sequence, which corresponds to the seven width measurements kl,t~,...t7 shown in Figure 15, is calculated by adding pairs of ~he consecutive integer values Xo,Xl,...X7, representing the widths of the bars and spaces, as follows:
tl = xo + Xl t2 = Xl ~ X2 t3 = x2 + x3 etc.
A width W for the entire codeword is also calculated in step 204 by summing the eight integer values xO + xl + . . . + X7.
For the codeword in Figure 15, for exampl.e, the sequence of integer values ~rom the ~can line, representing the widths of the bars and spaces might be something like: 43, 19, 21, 19, 22, 18, 1~3, 96. The raw t-sequence tl,t2,...t7 would then be 62, 40, 40, 41, 40, 121, l9q, and the width W would be 341.
In step 206 in Figure 14, the raw t-sequence obtained in step 204 is normalized and rounded to integer values. Specifically, a value for the codeword~s ~module~ or l'unit'~ is first established by dividing the width W of the codeword by the total number of units for each codeword. In a PDF417 symbol, each codeword is seventeen units, so that the width W is divided by ~eventeen to obtain the unit of the codeword. Thus t for the example in Figure 15, the unit would be (341/17) = 20Ø Each ~alue of the raw t-sequence is then divided by the unit and rounded to an integer to no~malize the t-sequence. The normalized t-sequence for the codeword in Figure lS is 3~ 2, 2, 2, 2, 6, 10.
\
- 33 - ~
. . . -: . .
.
:
-. .
, . . . : . . :
~0~31~3 The normalized t-sequence i5 then compared to the t-saquences of the start and stop patterns of the code in step 208. If the scanner scans from both left to right and right to left, then the t-sequence must be compared to the start and stop patterns in bo~h their normal and reverse orientations.
If there is a match in step 210, then the index is set in step 214 to a location in the scan line immediately following the pattern if it is a start pattern or i~mediately preceding it if it is a stop pattern. If the curren~ t-sequence does not match either the start or the stop pattern, however, then in step 212, the index is incremented by one and steps 202 through 210 are repeated until either a match is found or the length of the scan line is exceeded.
Figure 16 is a flow chart ~howing in greater detail the se~uence o~ steps for decoding a scan line of data into a vector o~ codewords and their clusters as referxed to in step 162 of Figure 12 above. In decodlng ~he individual codeword values and cluster numbers from the scan line, the low-level decoder begins decoding at the start or stop pattérn and decodes as many codewords possible~ For those codewords that are not successfully decoded, the codeword values in the codeword vector are set to '^ ~AD " .
At the completion of the sequence of steps shown in Figure 16, the codeword vector will contain certain codeword values and cluster numbers in locations corresponding to the appropriate columns of the codewords that were successfully decoded. Figure 17A shows an example of a codeword vector in which the codewords - 3~ -"' ' ' ' ' ' ' " ~ '' ' ' .
2~3~ ~3 in eight of the ten ~olumns were successfully decoded. The codeword values in columns 1 and 10 correspond to the left row indicator codeword in row 2 (L2) and the right row indicator codeword in row 1 (Rl), respectively. The codewords in columns 5 and 7 were not successfully decoded as indicated by the notation "BAD" in ~hose locations of the codeword vector.
Returning to the first step 220 of Figure 16, an upper limit on the number of codewords that may be decoded ("cwlimit") is set equal to the number of column5 in the codeword matrix. If this number of codewords is successfully decoded, then the decoding process for the current scan line ls obviously complete.
Step 2~2 determines the direction of the scan if the scanner scans from both left to right and right to left. If khe particular scan was from left to right as detenmined in step 222, then the column number of the first codeword is set to "1" in step 224 and the amount that it will incremented by ~"incr") each time a subsequent codeword is decoded is set to "+1". If the scan was from right to left, however, then in step ~26, the column number of the first codeword in the scan line will be the last column of the codeword matrix, and the incremental vaLue i9 set to "-l".
Step 228 is the first step of a control loop in which individual codeword values and their cluster numbers are decoded from the scan line of data. In step 228, the codeword limit is tested to see if it is still gre ter than zero. If not, then all of the codewords in the scan line have been decoded and the loop is exited.
, ' ~ ~ ' . . '.:
2~3~3~
Otherwise, step 230 obtain6 the next codeword value and its cluster number from the scan line. This step will be discussed in further detail below in connection with Figure 18.
If the codeword decoded in the previous step is a valid codeword as determined in step 232, then in ~t:ep 234 the codeword value and its cluster number are saved in the codeword vector at a location corresponding to the column of the codeword. The codeword values thus placed in the codeword vector are reacly for incorporation into the codeword matrix.
If the codeword decoded in step 230 is not a valid codeword, however, then the codeword value in the codeword vector corresponding to the current column is se~ to "BAD" in step 236 to indicate tha~ this codeword was not successfully decoded. A ~BAD~
codeword is most likely to occur when the ~can line crosses the boundary between two rows in the middle of the codeword.
Finally, in step 238, the current column number is either incremented or decremented depending on the direction of the scan, and the codeword limit is decremented by one. Steps 228-236 are then repeated until there has been an attempt to decode all of the codewords in the scan line.
Figure 18 is a flow chart diagram showing the sequence of step~ corresponding to step 230 in Figu.re 16 and step 172 in Figure 13 in which an attempt is made to decode an individual codeword value and cluster number from the scan line. In the fixst step 240, a raw t-sequence and the width W are obtained from the scan line. This same step was discussed previously in connection with step 204 in Figure 14.
2~1~3~3 In step 242, the width W of the eight elements presumed to be the next codeword are compared to the width of the pre~iously decoded codeword. If the current width W is not within a range o F
plus or minus a predetermined difference (delta), th~n there is probably a split ~undercount by a multiple of two elements) or a merge (overcount by a multiple of two element:s) error in the current codeword. This codeword is not decoded further, but rather in step 244 its value and cluster numher are both set ~o BAD to indicate that it could not be decoded.
Then in step 246, an attempt is made to resynchronize to the boundary o the next codeword by finding a t-sequence with a corresponding width ~ that falls with.in a given tolerance of the expected width of a codeword, basèd on the wid~h o~ the previous codeword. I~ the current width W i9 significantly greater than the expected width, indicating a po~sible merge error, then the last two integer values are dropped from the t-sequ~nce until it falls within the proper limits. Likewise, if the curxent wldth W
is significantly less than the expected width, indicating a possible split error, the next two integer values in the scan line are added to the t-sequence until it falls within the proper limi~s.
If the current width W is within a certain tolerance of the expected width, as determined in ~tep 242, then an attempt is made to decode the codeword. In step 248, ~he raw t-sequence is normalized as described above in connection with step 206 in Figure 14. Then in step 250, ~he cluster number is determined from the normalized t-~equence. The cluster number may bs .. - ~ .
.
2~31 ~3 determined from the t-sequence (as opposed to th~ X-sequence described above) as follows-cluster number = (Tl - T2 + T5 - T6) mod 9 For codewords in PDF417, valid cluster mImbers are 0, 3, and 6. I~ in step 252 it is determined that the cluster number is not 0, 3, or 6, then the codeword is not valid. Accordingly, in step 254 the cluster number and value are set to ~BAD~ to indicate that the codeword was not successfully decoded.
Otherwise, in step 256, the normalized t-sequence and its cluster number are used to find the corresponding codeword value in a look-up table. If no corresponding codeword val~e is found for th~ t-sequence, then the codeword ~alue i9 ~et to ~'BAD~ to indicate that it was not succe~sfully decoded.
Finally, in step 258 the "last width" value is updated to the current width W of the codeword for use in decoding the next codeword value from the scan line.
Figures 19A and l9B together comprise a flow chart of the sequence of steps executed by the low-level decoder in order to update the codeword matrix using the codeword vector. These figure~ explain in greater detail step 164 in Figure 12 discussed previou~ly.
The first step 260 of Figure l9A checks the first and la~t values in the codeword vector to see i~ either is a valid row indicator. If neither the first nor the last values in the codeword vector are valid row indicatoxs, then in step 262, the ' ~ ., ', , 2~$3~3 program exits the routine and no attempt is made to update the codeword matrix using the codeword vector.
If a valid row indicator is present, howe~er, then in step 264 confidence weights are as~igned to each codeword value in the codeword vector~ Specifically, a confidence weight is assigned to each cod~word depending on whether its nearest neighbors and their cluster were also decoded. For example, as shown in ~igure 17B, the codeword ~alues in columns l, 2, 3, 9, ancl lO are assigned high confidence weights ("H") because their in~ediate neighbors were also successfully decoded and have the same cluster number.
The codeword values for columns 4 and 8 are assigned medium confidence weights ("M") because one of their neighbors was successfully decoded and has the same cluster number but the other neighboring codeword value is ~BAD". The codeword value in column 3 is assigned a very low confidence weight ("L") because neither o~ its neighbors was succe3s~ully decoded. Thus, the confidence weight for a codeword value at column i in the codeword vector is essentially a function of ~he cluster numbers of the codewords at columns i - 1, i, and i + l. This function may be implemented by a look-up table whos0 index is calculated from the cluster numbers of the three codewords.
In step 266, a row number is assigned to each codeword value in the codeword vector based on the row indicator codewords and the cluster numbers. As shown in the example in Figure 17C, the left row indicator codeword L2 indicates that the row number is 2 and the cluster number is 6. The cluster numbers for the codeword values in columns 2-4 are also 6. Therefore, row number 2 is - ~ . , , , " ~. . ..
~.
' 2 ~ 3 assigned to the codeword values in the first four columns of the codeword vector.
Also in the example in Figure 17C, columns six and 8-10 all have a cluster number of 3 and the right row indicator codeword R
indicates that the row number is 1. Therefore, it can be assumed that the scan line crossed the row boundaxy between row 2 and row 1 and the codeword values in columns 6 and 8-10 should be assi~ned to row 1.
Once the confidence weights and row numbers have been hssigned to each of the codeword values in the codewoxd vector, the codeword matrix is updated one codeword at a time. In step 26~, the column number C of both the codeword vector and the codeword mat,rix is set is initially set ~o "1". Step 270 is the first step of an Lterative loop which steps through the codewords in the codeword vector and uses them to update the corresponding codewords and their associated confidence weights in the codeword matrix. When the column number C exceeds the number of columns in step 270, then all of the codewords in the codeword vector have been processed and the routine ands.
For each codeword in the codeword vector, 5t2p 272 sets the row number R o the codeword matrix to ~he row number as~igned in step 266 to the codeword in the codeword vector at the location C.
Thus, for each codeword value in the codeword vec~or, there is a corresponding value in the codeword matrix at location [R,C].
Continuing in Figure l9B, step 274 determines whethex the cuxrent codeword value in location ~R,CI in the codeword matrix is the same a~ the corresponding codeword value in the codeword , .
2~3~3 vector at column C. If the values are the same, then in step 276, the confidence weigh~ assigned to the codeword value in matrix location [R,C] is increased by the confidence weigh~ of the corresponding codeword value in the codeword vector. If not, the confidence weight of the codeword value in the matrix is decreased by the confidence weight of the codeword valule in the vector in step 278.
If the confidence weight was decreased in step 278, then in step 280 that confidence weight is tested to see if it was decreased below zero. If the confidence weight is less than zero, then in step 282 the new codeword value in the codeword vector is substituted for the current codeword value in the corresponding location in the codeword matrix. The confidence weight assigned to the codeword value in ~he matrix is also changed to a positive value in step 284.
Finally, in step 286 the colu~n number C is incremented by 1 for processing the next codeword value in the codeword vector and program control is returned to step 270 for repeating steps 272 through 286 for all of the columns in the vector.
Returnin~ briefly to step 154 in Figure 12, each time after the codeword matrix has been ~illed in with the new vector of codewo.rd values and the confidence weights have been updated, an attempt is made to fill in the rest of the matrix using the built-in error correction capability of the symbol. The number and location of codewords which have not yet been successfully decoded may be determined by comparing the confidence weights assigned to each of the codeword values in the matrix with a predetermined . . , ~' ~ , ' .
2B63~3 threshold. Those values having confidence weights below the threshold are considered to not yet be decoded. If the numbe~ of codewords not yet decoded is less than the error correction capability of the symbol as determined by the security level, then an attempt is made to correct the matrixO
It will be apparen~ to those skilled in the art that various modifications and varia~ions can be made in the decoding me~hod and apparatus without departing from the scope or spirit of the invention. Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specifi.cation and practice of the invention disclosed herein. It is in~ended that the specification and examples bo considered as exemplary only, with a true scope and spiri.t of the invention being indicated by the following claims.
, . .
' ~
.:
Claims (102)
1. A system for representing and recognizing data on a record carrier in the form of a machine readable two-dimensional bar code structure comprising:
encoding means including:
means for entering data in said encoding means;
processing means for encoding said data into a two-dimensional bar code structure, said bar code structure including a plurality of ordered, adjacent rows of codewords of bar-coded information, each of said codewords representing at least one information-bearing character, and for generating first transfer drive signals;
means for transferring an image of the two-dimensional bar code structure onto a portable record carrier in response to said first transfer drive signals; and recognition means including:
means for scanning the image of the two-dimensional bar code structure and for converting the codewords into electrical signals representative of the information-bearing characters; and means for decoding the electrical signals into output signals representative of said data.
encoding means including:
means for entering data in said encoding means;
processing means for encoding said data into a two-dimensional bar code structure, said bar code structure including a plurality of ordered, adjacent rows of codewords of bar-coded information, each of said codewords representing at least one information-bearing character, and for generating first transfer drive signals;
means for transferring an image of the two-dimensional bar code structure onto a portable record carrier in response to said first transfer drive signals; and recognition means including:
means for scanning the image of the two-dimensional bar code structure and for converting the codewords into electrical signals representative of the information-bearing characters; and means for decoding the electrical signals into output signals representative of said data.
2. The system of claim 1 wherein said recognition means includes an output device for displaying said data in human readable form.
3. The system of claim 2 wherein said output device is a liquid crystal display.
4. The system of claim 2 wherein said output device is a CRT display.
5. The system of claim 2 wherein said output device is a printer.
6. The system of claim 1 wherein said recognition means includes means for transmitting the decoder output signals to a computer.
7. The system of claim 6 wherein said transmitting means includes a modem.
8. The system of claim 1 wherein said recognition means includes means for transmitting the decoder output signals to a microprocessor.
9. The system of claim 8 wherein the microprocessor controls the operation of one of a facsimile machine, a VCR, a microwave oven, a robot and a weight/price label scale, in response to said decoder output signals.
10. The system of claim 1 wherein said entering means includes a keyboard for entering said data.
11. The system of claim 1 wherein said entering means includes means for scanning data from a sheet.
12. The system of claim 1 wherein said processing means includes means for generating second transfer drive signals in response to a second set of data, and wherein said transferring means includes reading means for transferring onto said carrier means both the image of the two-dimensional bar code structure in response to the first transfer drive signals and said second set of data in human readable form in response to said second transfer drive signals.
13. The system of claim 1 wherein the transferring means is a printer.
14. The system of claim 12 wherein said portable record carrier is a single carrier, and wherein said reading means includes signal means for transferring the two-dimensional bar code structure and the second set of data in human readable form onto the portable carrier.
15. A method for representing and recognizing data on a record carrier in the form of a machine readable two-dimensional bar code structure comprising the steps of:
entering said data into an encoding station;
encoding said data into a two-dimensional bar code structure, said bar code structure including a plurality of ordered, adjacent rows of codewords of bar-coded information, each of said codewords representing at least one information-bearing character;
transferring an image of the two-dimensional bar code structure onto a portable record carrier;
scanning the image of the two-dimensional bar code structure in a separate decoding station and converting the codewords into electrical signals representative of the information-bearing characters; and decoding the electrical signals into output signals representing said data.
entering said data into an encoding station;
encoding said data into a two-dimensional bar code structure, said bar code structure including a plurality of ordered, adjacent rows of codewords of bar-coded information, each of said codewords representing at least one information-bearing character;
transferring an image of the two-dimensional bar code structure onto a portable record carrier;
scanning the image of the two-dimensional bar code structure in a separate decoding station and converting the codewords into electrical signals representative of the information-bearing characters; and decoding the electrical signals into output signals representing said data.
16. The method of claim 15 wherein said entering step includes the substep of entering said data on a keyboard.
17. The method of claim 15 wherein said entering step includes the substep of scanning said data from a sheet.
18. The method of claim 15 wherein said transferring step includes the substep of printing the image onto the carrier.
19. The method of claim 15 further comprising the step of displaying the data in human readable form.
20. The method of claim 19 wherein said displaying step includes the substep of displaying the data on a CRT display.
21. The method of claim 19 wherein said displaying step includes the substep of displaying the data on a liquid crystal display.
22. The method of claim 19 wherein said displaying step includes the substep of printing the data on a printer.
23. The method of claim 1 further comprising the step of transmitting the output signals to a computer.
24. The method of claim 23 wherein said transmitting step includes the substep of transmitting the output signals to the computer by a modem.
25. The method of claim 15 further comprising the step of transmitting the output signals to a microprocessor.
26. The method of claim 25 further comprising the step of controlling the operation of one of a facsimile machine, a VCR, a microwave oven, a robot and a weight/price label scale, in response to the output signals.
27. The method of claim 15 further comprising the steps of entering a second set of data into the encoding station; and transferring onto the portable record carrier both the image of the two-dimensional bar code structure and said second set of data in human readable form.
28. A system for secure transmission of data from a first station to a second station comprising:
encoding means in said first station including means for entering data, means for encrypting at least some of said data using an encryption algorithm based upon an encryption key, and means for representing said encrypted data in the form of a two-dimensional bar code structure, said bar code structure including a plurality of ordered, adjacent rows of codewords of bar-coded information, each of said codewords representing at least one information-bearing character; and decoding means in said second station including means for scanning the two-dimensional bar code structure and converting the codewords into output signals representative of said information-bearing characters, and means for decrypting at least some of said information-bearing characters using a decryption algorithm based upon said encryption key.
encoding means in said first station including means for entering data, means for encrypting at least some of said data using an encryption algorithm based upon an encryption key, and means for representing said encrypted data in the form of a two-dimensional bar code structure, said bar code structure including a plurality of ordered, adjacent rows of codewords of bar-coded information, each of said codewords representing at least one information-bearing character; and decoding means in said second station including means for scanning the two-dimensional bar code structure and converting the codewords into output signals representative of said information-bearing characters, and means for decrypting at least some of said information-bearing characters using a decryption algorithm based upon said encryption key.
29. The system of claim 28 wherein said entering means includes a keyboard for entering said data.
30. The system of claim 28 wherein said entering means includes means for scanning said data from a sheet.
31. The system of claim 28 wherein said encoding means further includes means for transferring an image of the two-dimensional bar code structure onto a carrier.
32. The system of claim 31 wherein said transferring means is a printer.
33. The system of claim 28 wherein said decoding means further includes an output device for displaying the decrypted data in human readable form.
34. The system of claim 33 wherein said output device is a CRT display.
35. The system of claim 33 wherein said output device is a liquid crystal display.
36. The system of claim 33 wherein said output device is a printer.
37. An encoding/decoding apparatus for use in a system for secure transmission of data, the apparatus comprising:
encoding means including means for entering data, means for encrypting at least some of said data using an encryption algorithm based upon an encryption key, and means for representing said encrypted data in the form of a two-dimensional bar code structure, said bar code structure including a plurality of ordered, adjacent rows of codewords of bar-coded information, each of said codewords representing at least one information-bearing character; and decoding means including means for scanning the two-dimensional bar code structure and converting the codewords into output signals representative of said information-bearing characters, and means for decrypting at least some of said information-bearing characters using a decryption algorithm based upon said encryption key.
encoding means including means for entering data, means for encrypting at least some of said data using an encryption algorithm based upon an encryption key, and means for representing said encrypted data in the form of a two-dimensional bar code structure, said bar code structure including a plurality of ordered, adjacent rows of codewords of bar-coded information, each of said codewords representing at least one information-bearing character; and decoding means including means for scanning the two-dimensional bar code structure and converting the codewords into output signals representative of said information-bearing characters, and means for decrypting at least some of said information-bearing characters using a decryption algorithm based upon said encryption key.
38. The apparatus of claim 37 wherein said entering means includes a keyboard for entering said data.
39. The apparatus of claim 37 wherein said entering means includes means for scanning said data from a sheet.
40. The apparatus of claim 37 wherein said encoding means further includes means for transferring an image of the two-dimensional bar code structure onto a carrier.
41. The apparatus of claim 37 wherein said transferring means is a printer.
42. The apparatus of claim 37 wherein said decoding means further includes an output device for displaying the decrypted data in human readable form.
43. The apparatus of claim 42 wherein said output device is a CRT display.
44. The apparatus of claim 42 wherein said output device is a liquid crystal display.
45. The apparatus of claim 42 wherein said output device is a printer.
46. An encoding apparatus for use in a system for secure transmission of data, the apparatus comprising:
means for entering data;
means for encrypting at least some of said data using an encryption algorithm based upon an encryption key; and means for representing said encrypted data in the form of a two-dimensional bar code structure, said bar code structure including a plurality of ordered, adjacent rows of codewords of bar-coded information, each of said codewords representing at least one information-bearing character.
means for entering data;
means for encrypting at least some of said data using an encryption algorithm based upon an encryption key; and means for representing said encrypted data in the form of a two-dimensional bar code structure, said bar code structure including a plurality of ordered, adjacent rows of codewords of bar-coded information, each of said codewords representing at least one information-bearing character.
47. The apparatus of claim 46 wherein said entering means includes a keyboard for entering said data.
48. The apparatus of claim 46 wherein said entering means includes means for scanning said data from a sheet.
49. The encoding apparatus of claim 46 further comprising means for transferring an image of the two-dimensional bar code structure onto a carrier.
50. The apparatus of claim 49 wherein said transferring means is a printer.
51. A decoding apparatus for use in a system for secure transmission of data by a two-dimensional bar code structure, said bar code structure including a plurality of ordered, adjacent rows of codewords of bar coded information, each of said codewords representing at least one information-bearing character, the apparatus comprising:
means for scanning the two-dimensional bar code structure and converting the codewords into output signals representative of said information-bearing characters, and means for decrypting at least some of said information-bearing characters using a decryption algorithm based upon an encryption key.
means for scanning the two-dimensional bar code structure and converting the codewords into output signals representative of said information-bearing characters, and means for decrypting at least some of said information-bearing characters using a decryption algorithm based upon an encryption key.
52. The apparatus or claim 51 further comprising an output device for displaying the decrypted data in human readable form.
53. The apparatus of claim 52 wherein said output device is a CRT display.
54. The apparatus of claim 52 wherein said output device is a liquid crystal display.
55. The apparatus of claim 52 wherein said output device is a printer.
56. A method of encoding and decoding data for secure transmission comprising the steps of:
entering said data into an encoding station;
encrypting at least some of said data using an encryption algorithm based upon an encryption key;
representing said encrypted data in the form of a two-dimensional bar code structure, said bar code structure including a plurality of ordered, adjacent rows of codewords of bar-coded information, each of said codewords representing at least one information-bearing character;
scanning the two-dimensional bar code structure in a separate decoding station and converting the codewords into output signals representative of said information-bearing characters; and decrypting at least some of said information-bearing characters using a decryption algorithm based upon said encryption key.
entering said data into an encoding station;
encrypting at least some of said data using an encryption algorithm based upon an encryption key;
representing said encrypted data in the form of a two-dimensional bar code structure, said bar code structure including a plurality of ordered, adjacent rows of codewords of bar-coded information, each of said codewords representing at least one information-bearing character;
scanning the two-dimensional bar code structure in a separate decoding station and converting the codewords into output signals representative of said information-bearing characters; and decrypting at least some of said information-bearing characters using a decryption algorithm based upon said encryption key.
57. The method of claim 56 wherein said entering step includes the substep of entering said data on a keyboard.
58. The method of claim 56 wherein said entering step includes the substep of scanning said data from a sheet.
59. The method of claim 56 further comprises the step of transferring an image of the two-dimensional bar code structure onto a carrier.
60. The method of claim 59 wherein said transferring step includes the substep of printing the image onto the carrier.
61. The method of claim 56 further comprising the step of displaying the decrypted data in human readable form.
62. The method of claim 61 wherein said displaying step includes the substep of displaying the decrypted data on a CRT
display.
display.
63. The method of claim 61 wherein said displaying step includes the substep of displaying the decrypted data on a liquid crystal display.
64. The method of claim 61 wherein said displaying step includes the substep of displaying the decrypted data on a printer.
65. A facsimile communications system for transmitting a document to a destination comprising:
means for entering transmission information including a destination telephone number;
means for converting said transmission information into a two-dimensional bar code representation;
means for affixing said two-dimensional bar code representation of said transmission information, including the destination telephone number, to said document;
means for scanning said document, including said two-dimensional bar code representation fixed thereto, and for producing signals representing said transmission information; and means for transmitting said document to said destination in accordance with said signals representing said transmission information, including the destination telephone number.
means for entering transmission information including a destination telephone number;
means for converting said transmission information into a two-dimensional bar code representation;
means for affixing said two-dimensional bar code representation of said transmission information, including the destination telephone number, to said document;
means for scanning said document, including said two-dimensional bar code representation fixed thereto, and for producing signals representing said transmission information; and means for transmitting said document to said destination in accordance with said signals representing said transmission information, including the destination telephone number.
66. The system of claim 65, wherein said two-dimensional bar code representation includes a plurality of ordered, adjacent rows of codewords of bar coded information, each of said codewords representing at least one information-bearing character.
67. The system of claim 65, wherein said means for affixing said two-dimensional bar code representation to said document includes a printer for printing said two-dimensional bar code representation on said document.
68. A method of operating a facsimile communications system for transmitting a document to a destination, comprising the steps of:
entering transmission information including a destination telephone number on a keyboard;
converting said transmission information into a two-dimensional bar code representation; affixing said two-dimensional bar code representation of said transmission information, including the destination telephone number, to said document;
scanning said document, including said two-dimensional bar code representation affixed thereto, and producing signals representing said transmission information; and transmitting said document to said destination in accordance with said signals representing said transmission information, including the destination telephone number.
entering transmission information including a destination telephone number on a keyboard;
converting said transmission information into a two-dimensional bar code representation; affixing said two-dimensional bar code representation of said transmission information, including the destination telephone number, to said document;
scanning said document, including said two-dimensional bar code representation affixed thereto, and producing signals representing said transmission information; and transmitting said document to said destination in accordance with said signals representing said transmission information, including the destination telephone number.
69. The method of claim 68, wherein said two-dimensional bar code representation includes a plurality of ordered, adjacent rows of codewords of bar-coded information, each of said codewords representing at least one information-bearing character.
70. The method of claim 68, wherein said step of affixing said two-dimensional bar code representation to said document includes the substep of printing said two-dimensional bar code representation on said document.
71. An apparatus for decoding a two-dimensional bar code symbol, the bar code symbol including a plurality of ordered, adjacent rows of codewords of bar-coded information from a set of codewords, the set of codewords being partitioned into at least three mutually exclusive clusters, each row in the symbol having at least one row indicator codeword and containing only codewords from a cluster different from the codewords in an adjacent row, comprising:
means for scanning the two-dimensional bar code symbol to produce scan lines of data representing the bar-coded information in the codewords of the symbol;
means for decoding a scan line of data into a vector of codeword values corresponding to the codewords that were scanned, at least one of the codeword values being for a row indicator codeword;
means for assigning a row number to each of the codeword values in the vector based on the value of the row indicator codeword and the cluster of the codeword; and means for filling in a codeword matrix with the codeword values in the vector according to their assigned row numbers.
means for scanning the two-dimensional bar code symbol to produce scan lines of data representing the bar-coded information in the codewords of the symbol;
means for decoding a scan line of data into a vector of codeword values corresponding to the codewords that were scanned, at least one of the codeword values being for a row indicator codeword;
means for assigning a row number to each of the codeword values in the vector based on the value of the row indicator codeword and the cluster of the codeword; and means for filling in a codeword matrix with the codeword values in the vector according to their assigned row numbers.
72. The apparatus of claim 71, wherein the row indicator codewords contain information regarding the number of rows in the symbol and the number of codewords in each row, and wherein the apparatus further comprises means for decoding a scan line of data to obtain a codeword value for a row indicator codeword, and means for determining one of the number of rows and the number of codewords in each row from the codeword value for the row indicator codeword.
73. The apparatus of claim 72, wherein each row of the symbol contains a start and a stop pattern of bar-coded information, and wherein the means for decoding a scan line of data to obtain a codeword value for a row indicator codeword includes means for locating a sequence of data in the scan line corresponding to one of the start and the stop pattern.
74. The apparatus of claim 71, wherein the symbol contains at least one error correction codeword and the row indicator codewords contain information regarding the number of rows in the symbol, the number of codewords in each row, and the number of error correction codewords, and wherein the apparatus further comprises means for decoding a scan line of data to obtain a codeword value for a row indicator codeword, means for determining a value for one of the number of rows, the number of codewords in each row, and the number of error correction codewords from the codeword value for the row indicator codeword, means for adjusting a confidence weight for a corresponding one of the number of rows, the number of codewords in each row, and the number of error correction codewords based on the value determined in the preceding step and a previous value obtained by decoding a row indicator codeword, and means for initializing the codeword matrix when the confidence weights for the number of rows, the number of codewords in each row, and the number of error correction codewords all exceed a predetermined threshold.
75. The apparatus of claim 74, wherein each row of the symbol contains a start and a stop pattern of bar-coded information, and wherein the means for decoding a scan line of data to obtain a codeword value for a row indicator codeword includes means for locating a sequence of data in the scan line corresponding to one of the start and the stop pattern.
76. The apparatus of claim 71, wherein each row of the symbol contains a start and a stop pattern of bar-coded information, and wherein the means for decoding a scan line of data to obtain a codeword value for a row indicator codeword includes means for locating a sequence of data in the scan line corresponding to one of the start and the stop pattern.
77. The apparatus of claim 71, further comprising means for assigning a confidence weight to each of the codeword values in the vector, and means for adjusting a confidence weight of each of the corresponding codeword values in the matrix based on the codeword value in the vector and a current value of each of the corresponding codeword values in the matrix.
78. The apparatus of claim 71, wherein the symbol contains at least one error correction codeword, and wherein the apparatus further comprises means for locating in the matrix the codeword values for any codewords that have not been successfully decoded, and means for correcting any erroneous codeword values in the codeword matrix using the error correction codeword.
79. A method for decoding a two-dimensional bar code symbol, the bar code symbol including a plurality of ordered, adjacent rows of codewords of bar-coded information from a set of codewords, the set of codewords being partitioned into at least three mutually exclusive clusters, each row in the symbol having at least one row indicator codeword and containing only codewords from a cluster different from the codewords in an adjacent row, comprising the steps of:
scanning the two-dimensional bar code symbol to produce scan lines of data representing the bar-coded information in the codewords of the symbol;
decoding a scan line of data into a vector of codeword values corresponding to the codewords that were scanned, at least one of the codeword values being for a row indicator codeword;
assigning a row number to each of the codeword values in the vector based on the value of the row indicator codeword and the cluster of the codeword; and filling in a codeword matrix with the codeword values in the vector according to their assigned row numbers.
scanning the two-dimensional bar code symbol to produce scan lines of data representing the bar-coded information in the codewords of the symbol;
decoding a scan line of data into a vector of codeword values corresponding to the codewords that were scanned, at least one of the codeword values being for a row indicator codeword;
assigning a row number to each of the codeword values in the vector based on the value of the row indicator codeword and the cluster of the codeword; and filling in a codeword matrix with the codeword values in the vector according to their assigned row numbers.
80. The method of claim 79, wherein the row indicator codewords contain information regarding the number of rows in the symbol and the number of codewords in each row, and wherein the method further comprises the steps of decoding a scan line of data to obtain a codeword value for a row indicator codeword, and determining one of the number of rows and the number of codewords in each row from the codeword value for the row indicator codeword.
81. The method of claim 80, wherein each row of the symbol contains a start and a stop pattern of bar-coded information, and wherein the step of decoding a scan line of data to obtain a codeword value for a row indicator codeword includes the substep of locating a sequence of data in the scan line corresponding to one of the start and the stop pattern.
82. The method of claim 79, wherein the symbol contains at least one error correction codeword and the row indicator codewords contain information regarding the number of rows in the symbol, the number of codewords in each row, and the number of error correction codewords, and wherein the method further comprises the steps of decoding a scan line of data to obtain a codeword value for a row indicator codeword, determining a value for one of the number of rows, the number of codewords in each row, and the number of error correction codewords from the codeword value for the row indicator codeword, adjusting a confidence weight for a corresponding one of the number of rows, the number of codewords in each row, and the number of error correction codewords based on the value determined in the preceding step and a previous value obtained by decoding a row indicator codeword, and initializing the codeword matrix when the confidence weights for the number of rows, the number of codewords in each row, and the number of error correction codewords all exceed a predetermined threshold.
83. The method of claim 79, wherein each row of the symbol contains a start and a stop pattern of bar-coded information, and wherein the step of decoding a scan line of data to obtain a codeword value for a row indicator codeword includes the substep of locating a sequence of data in the scan line corresponding to one of the start and the stop pattern.
84. The method of claim 79, wherein each row of the symbol contains a start and a stop pattern of bar-coded information, and wherein the step of decoding a scan line of data into a vector of codeword values includes the substep of locating a sequence of data in the scan line corresponding to one of the start and the stop pattern.
85. The method of claim 79, further comprising the steps of assigning a confidence weight to each of the codeword values in the vector, adjusting a confidence weight of each of the corresponding codeword values in the matrix based on the codeword value in the vector and a current value of each of the corresponding codeword values in the matrix.
86. The method of claim 79, wherein the symbol contains at least one error correction codeword, and wherein the method further comprises the steps of locating in the matrix the codeword values for any codewords that have not been successfully decoded, and correcting any erroneous codeword values in the codeword matrix using the error correction codeword.
87. A system for representing and recognizing data on a record carrier in the form of a machine readable two-dimensional bar code structure comprising:
encoding means including:
means for entering data in said encoding means, processing means for encoding said data into a two-dimensional bar code structure, the bar code structure including a plurality of ordered, adjacent rows of codewords of bar-coded information from a set of codewords, the set of codewords being partitioned into at least three mutually exclusive clusters, each row in the two-dimensional bar code structure having at least one row indicator codeword and containing only codewords from a cluster different from the codewords in an adjacent row, means for transferring an image of the two-dimensional bar code structure onto a portable record carrier in response to said first transfer drive signals; and recognition means including:
means for scanning the image of two-dimensional bar code structure to produce scan lines of data representing the bar-coded information in the codewords of the two-dimensional bar code structure, means for decoding a scan line of data into a vector of codeword values corresponding to the codewords that were scanned, at least one of the codeword values being for a row indicator codeword, means for assigning a row number to each of the codeword values in the vector based on the value of the row indicator codeword and the cluster of the codeword, and means for filling in a codeword matrix with the codeword values in the vector according to their assigned row numbers.
encoding means including:
means for entering data in said encoding means, processing means for encoding said data into a two-dimensional bar code structure, the bar code structure including a plurality of ordered, adjacent rows of codewords of bar-coded information from a set of codewords, the set of codewords being partitioned into at least three mutually exclusive clusters, each row in the two-dimensional bar code structure having at least one row indicator codeword and containing only codewords from a cluster different from the codewords in an adjacent row, means for transferring an image of the two-dimensional bar code structure onto a portable record carrier in response to said first transfer drive signals; and recognition means including:
means for scanning the image of two-dimensional bar code structure to produce scan lines of data representing the bar-coded information in the codewords of the two-dimensional bar code structure, means for decoding a scan line of data into a vector of codeword values corresponding to the codewords that were scanned, at least one of the codeword values being for a row indicator codeword, means for assigning a row number to each of the codeword values in the vector based on the value of the row indicator codeword and the cluster of the codeword, and means for filling in a codeword matrix with the codeword values in the vector according to their assigned row numbers.
88. The system of claim 87, wherein the row indicator codewords contain information regarding the number of rows in the two-dimensional bar code structure and the number of codewords in each row, and wherein the recognition means further includes means for decoding a scan line of data to obtain a codeword value for a row indicator codeword, and means for determining one of the number of rows and the number of codewords in each row from the codeword value for the row indicator codeword.
89. The system of claim 88, wherein each row of the two-dimensional bar code structure contains a start and a stop pattern of bar-coded information, and wherein the means for decoding a scan line of data to obtain a codeword value for a row indicator codeword includes means for locating a sequence of data in the scan line corresponding to one of the start and the stop pattern.
90. The system of claim 87, wherein the two dimensional bar code structure contains at least one error correction codeword and the row indicator codewords contain information regarding the number of rows in the two-dimensional bar code structure, the number of codewords in each row, and the number of error correction codewords, and wherein the recognition means further includes means for decoding a scan line of data to obtain a codeword value for a row indicator codeword, means for determining a value for one of the number of rows, the number of codewords in each row, and the number of error correction codewords from the codeword value for the row indicator codeword, means for adjusting a confidence weight for a corresponding one of the number of rows, the number of codewords in each row, and the number of error correction codewords based on the value determined in the preceding step and a previous value obtained by decoding a row indicator codeword, and means for initializing the codeword matrix when the confidence weights for the number of rows, the number of codewords in each row, and the number of error correction codewords all exceed a predetermined threshold.
91. The system of claim 90, wherein each row of the two-dimensional bar code structure contains a start and a stop pattern of bar-coded information, and wherein the means for decoding a scan line of data to obtain a codeword value for a row indicator codeword includes means for locating a sequence of data in the scan line corresponding to one of the start and the stop pattern.
92. The system of claim 87, wherein each row of the two-dimensional bar code structure contains a start and a stop pattern of bar-coded information, and wherein the means for decoding a scan line of data to obtain a codeword value for a row indicator codeword includes means for locating a sequence of data in the scan line corresponding to one of the start and the stop pattern.
93. The system of claim 87, wherein the recognition means further includes means for assigning a confidence weight to each of the codeword values in the vector, and means for adjusting a confidence weight of each of the corresponding codeword values in the matrix based on the codeword value in the vector and a current value of each of the corresponding codeword values in the matrix.
94. The system of claim 87, wherein the two-dimensional bar code structure contains at least one error correction codeword, and wherein the recognition means further includes means for locating in the matrix the codeword values for any codewords that have not been successfully decoded, and means for correcting any erroneous codeword values in the codeword matrix using the error correction codeword.
95. A method for representing and recognizing data on a record carrier in the form of a machine readable two-dimensional bar code structure comprising the steps of:
entering said data into an encoding station;
encoding said data into a two-dimensional bar code structure, the two-dimensional bar code structure including a plurality of ordered, adjacent rows of codewords of bar-coded information from a set of codewords, the set of codewords being partitioned into at least three mutually exclusive clusters, each row in the two-dimensional bar code structure having at least one row indicator codeword and containing only codewords from a cluster different from the codewords in an adjacent row, transferring an image of the two-dimensional bar code structure onto a portable record carrier;
scanning the image of the two-dimensional bar code structure to produce scan lines of data representing the bar-coded information in the codewords;
decoding a scan line of data into a vector of codeword values corresponding to the codewords that were scanned, at least one of the codeword values being for a row indicator codeword;
assigning a row number to each of the codeword values in the vector based on the value of the row indicator codeword and the cluster of the codeword; and filling in a codeword matrix with the codeword values in the vector according to their assigned row numbers.
entering said data into an encoding station;
encoding said data into a two-dimensional bar code structure, the two-dimensional bar code structure including a plurality of ordered, adjacent rows of codewords of bar-coded information from a set of codewords, the set of codewords being partitioned into at least three mutually exclusive clusters, each row in the two-dimensional bar code structure having at least one row indicator codeword and containing only codewords from a cluster different from the codewords in an adjacent row, transferring an image of the two-dimensional bar code structure onto a portable record carrier;
scanning the image of the two-dimensional bar code structure to produce scan lines of data representing the bar-coded information in the codewords;
decoding a scan line of data into a vector of codeword values corresponding to the codewords that were scanned, at least one of the codeword values being for a row indicator codeword;
assigning a row number to each of the codeword values in the vector based on the value of the row indicator codeword and the cluster of the codeword; and filling in a codeword matrix with the codeword values in the vector according to their assigned row numbers.
96. The method of claim 95, wherein the row indicator codewords contain information regarding the number of rows in the two-dimensional bar code structure and the number of codewords in each row, and wherein the method further comprises the steps of decoding a scan line of data to obtain a codeword value for a row indicator codeword, and determining one of the number of rows and the number of codewords in each row from the codeword value for the row indicator codeword.
97. The method of claim 96, wherein each row of the two-dimensional bar code structure contains a start and a stop pattern of bar-coded information, and wherein the step of decoding a scan line of data to obtain a codeword value for a row indicator codeword includes the substep of locating a sequence of data in the scan line corresponding to one of the start and the stop pattern.
98. The method of claim 95, wherein the two-dimensional bar code structure contains at least one error correction codeword and the row indicator codewords contain information regarding the number of rows in the two-dimensional bar code structure, the number of codewords in each row, and the number of error correction codewords, and wherein the method further comprises the steps of decoding a scan line of data to obtain a codeword value for a row indicator codeword, determining a value for one of the number of rows, the number of codewords in each row, and the number of error correction codewords from the codeword value for the row indicator codeword, adjusting a confidence weight for a corresponding one of the number of rows, the number of codewords in each row, and the number of error correction codewords based on the value determined in the preceding step and a previous value obtained by decoding a row indicator codeword, and initializing the codeword matrix when the confidence weights for the number of rows, the number of codewords in each row, and the number of error correction codewords all exceed a predetermined threshold.
99. The method of claim 95, wherein each row of the two-dimensional bar code structure contains a start and a stop pattern of bar-coded information, and wherein the step of decoding a scan line of data to obtain a codeword value for a row indicator codeword includes the substep of locating a sequence of data in the scan line corresponding to one of the start and the stop pattern.
100. The method of claim 95, wherein each row of the two-dimensional bar code structure contains a start and a stop pattern of bar-coded information, and wherein the step of decoding a scan line of data into a vector of codeword values includes the substep of locating a sequence of data in the scan line corresponding to one of the start and the stop pattern.
101. The method of claim 95, further comprising the steps of assigning a confidence weight to each of the codeword values in the vector, adjusting a confidence weight of each of the corresponding codeword values in the matrix based on the codeword value in the vector and a current value of each of the corresponding codeword values in the matrix.
102. The method of claim 95, wherein the two-dimensional bar code structure contains at least one error correction codeword, and wherein the method further comprises the steps of locating in the matrix the codeword values for any codewords that have not been successfully decoded, and correcting any erroneous codeword values in the codeword matrix using the error correction codeword.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA002063103A CA2063103A1 (en) | 1992-03-16 | 1992-03-16 | Systems for encoding and decoding data in machine readable graphic form |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA002063103A CA2063103A1 (en) | 1992-03-16 | 1992-03-16 | Systems for encoding and decoding data in machine readable graphic form |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2063103A1 true CA2063103A1 (en) | 1993-09-17 |
Family
ID=4149435
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002063103A Abandoned CA2063103A1 (en) | 1992-03-16 | 1992-03-16 | Systems for encoding and decoding data in machine readable graphic form |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2063103A1 (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5602382A (en) * | 1994-10-31 | 1997-02-11 | Canada Post Corporation | Mail piece bar code having a data content identifier |
| CN110322198A (en) * | 2019-06-28 | 2019-10-11 | 成都诚至诚商务物流有限责任公司 | Be adapted to automation cigarette it is orderly put stacking system and operation method |
| CN112889074A (en) * | 2018-10-29 | 2021-06-01 | 三菱电机株式会社 | Decoding method, computer program product and device |
-
1992
- 1992-03-16 CA CA002063103A patent/CA2063103A1/en not_active Abandoned
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5602382A (en) * | 1994-10-31 | 1997-02-11 | Canada Post Corporation | Mail piece bar code having a data content identifier |
| CN112889074A (en) * | 2018-10-29 | 2021-06-01 | 三菱电机株式会社 | Decoding method, computer program product and device |
| CN110322198A (en) * | 2019-06-28 | 2019-10-11 | 成都诚至诚商务物流有限责任公司 | Be adapted to automation cigarette it is orderly put stacking system and operation method |
| CN110322198B (en) * | 2019-06-28 | 2023-09-22 | 四川省烟草公司成都市公司 | Ordered cigarette stacking system suitable for automation and operation method |
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