WO1996025878A1

WO1996025878A1 - An identification system

Info

Publication number: WO1996025878A1
Application number: PCT/GB1995/000373
Authority: WO
Inventors: Theunis Christiaan Verster; Albertus Jacobus Kemp
Original assignee: Csir (Department Of Microelectronics & Communications Technology); Whalley, Kevin
Priority date: 1995-02-23
Filing date: 1995-02-23
Publication date: 1996-08-29
Also published as: AU1713895A

Abstract

An identification system (10) includes a referencing device (12) on which a person's hand is receivable. A signal injecting means (18) is carried by the referencing device (12) for injecting a measuring signal into the person's hand. A measuring arrangement (24) is carried by the referencing device (12) for measuring predetermined parameters of the person's hand by measuring the strength of the measuring signal at predetermined positions on the referencing device (12) and for generating a measured signal representative of said measured parameters. A signal processing means processes said measured signal to provide an output signal indicative of the identity of the person.

Description

AN IDENTIFICATION SYSTEM

THIS INVENTION relates to an identification system. More particularly, the invention relates to an identification system for identifying a person and to a method of identifying a person.

According to a first aspect of the invention, there is provided an identification system for identifying a person, the identification system including a referencing device on which a predetermined part of a person's body is receivable; a signal injecting means carried by the referencing device for injecting a measuring signal into said part of the person's body; a measuring arrangement carried by the referencing device for measuring predetermined parameters of the part of the person's body by measuring the strength of the measuring signal at predetermined positions on the referencing device and for generating a measured signal representative of said measured parameters; and a signal processing means for processing said measured signal to provide an output signal indicative of the identity of the person.

In a preferred embodiment of the invention, the measured parameters or biometric data to be used n identifying the person relate to pnysical dimensions of that person such as hand or finger length dimensions Preferably, the invention relates to measuring lengths of a person's fingers and using sucn data for identifying the person. It will be appreciated that, by measuring the lengths of a person's fingers, a predetermined hand profile can be obtained This hand profile can be electronically stored to serve the purpose of biometric identification of the person. The hand profile is hereinafter referred to as a fingertip contour.

The term "fingertip contour" as related to the invention, is to be understood as the length of each finger as well as the relationship between the lengths of the fingers of the person's hand.

The referencing device may be of a non- conductive material and the signal injecting means may then be an element of a conductive material arranged on a surface of the referencing device. The signal injecting means may include a signal generating device, in the form of an oscillator connected to the element. It will be appreciated that, to cater for various sizes of hands and to ensure adequate signal transfer, the pad must be sufficiently large to cater for a wide range of hand sizes.

The measuring arrangement may include a plurality of strips of electrically conductive material, the strips being arranged on the referencing device and being electrically isolated from one another and from the element.

Each strip may comprise a plurality of discrete pads, the pads being electrically isolated from one another. The spacing and size of the finger pads will be dependent on the required level of security of the system, and the speed required of the system and the cost associated therewith. A strip may be provided for each of at least certain fingers, including a thumb, of a hand of a person for measuring the lengths of said fingers. A strip may, preferably, be associated with each finger of the person's hand. Additional strips may be provided for measuring a width of the hand.

It will be appreciated that the more coarse the spacing or pitch of the pads, the lower the accuracy - H - but the higher the speed and the lower the cost of the system will be. Conversely, the smaller or finer the pitch is, the higher the accuracy will be.

In use, the lower limit of the coarseness of the pitch will be bound by the repeatability of results obtained for the same person.

The measuring arrangement may include a signal strength detector for detecting a signal strength in respect of each pad of the measuring arrangement.

In use, each finger pad may be sequentially addressed by circuitry of the measuring arrangement to obtain a complete fingertip contour measurement.

The measuring arrangement may include control circuitry for controlling operation of the measuring arrangement, the control circuitry including a microprocessor for generating logic control signals for addressing each pad of the measuring arrangement as well as for processing the signal strength read from each of said pads via the detector and an appropriate analogue/digital conversion means.

The measuring arrangement may also include a communications link for communicating with the signal processing means. The signal processing means may be operable to improve the accuracy of the measured signal output by the measuring arrangement. Thus, the signal processing means may include software which includes an interpolation algorithm for processing the measured signal to improve the accuracy of the measured signal.

By means of the interpolation algorithm, the "resolution" of the finger pads is improved thereby improving the accuracy of the system.

The software may further include a rotation algorithm for compensating for placement of the person's hand on the referencing device. By means of the rotation algorithm, rotation of the person's hand around a locating means of the referencing device is taken into account thereby compensating for positional placement of the person's hand on the referencing device.

It will be appreciated that, instead of a separate computer, the control circuitry could include the necessary interpolation and rotation algorithms.

The referencing device may include the locating means for ensuring that the person's hand is correctly placed on the measuring arrangement. The locating means may, for example, comprise at least one stop member arranged on the upper surface of the referencing device against which a part of the person's hand abuts. Thus, for example, the stop member may be received between an index finger and a middle finger of a person's hand such that a web of the hand between these fingers abuts against the stop member.

In another embodiment of the invention, the arrangement of the strips of pads on the referencing device may be symmetrical about the centremost strip so that either a person's left hand or right hand can be placed on the referencing device. In that case, if no stop member is provided, the system may be utilised only for measuring the shape of the fingertip contour as opposed to the position and shape. It will be appreciated that, in such a case, the system will be used where a high level of security is not required.

In one embodiment of the invention the referencing device may be a plate on which the person's hand is receivable.

In another embodiment of the invention, the referencing device may comprise a cylinder about which the person's hand is placed.

The diameter of the cylinder may be such that when a person's hand is placed about the cylinder the tips of the person's fingers and thumb do not touch. In this embodiment of the invention, the locating means may comprise stop members arranged on the cylinder against which the tip of the thumb and at least the tip of one finger abut. That stop member against which the tip of the thumb abuts may be fixed while the, or each, other stop member may be slidably arranged on the outer surface of the cylinder.

The measuring arrangement in this embodiment may be operable also to measure the width of the hand.

According to a second aspect of the invention, there is provided a method of identifying a person which includes injecting a signal into a predetermined part of a person's body,- measuring the strength of the signal at predetermined locations relative to said parts of the person's body to provide a measured signal representative of measured parameters of the part of the body; and processing said measured signal to provide an output signal indicative of the identity of the person.

The method may include injecting the signal, at a predetermined frequency into a hand of the person and measuring the signal at various positions in respect of at least certain of the fingers of the hand to obtain data relating to the lengths of said fingers. The method may include, additionally, measuring the width of the hand.

Further, the method may include processing the measured signal by carrying out an interpolation operation on the signal to improve the accuracy of the measured signal. The method may then also include utilizing a rotational algorithm on the measured signal to compensate for placement of said part of the person's body on a measuring arrangement which obtains said measured parameters of the person's body.

The invention is now described, by way of example, with reference to the accompanying diagrammatic drawings.

In the drawings,

Figure 1 shows a plan view of an identification system, in accordance with one embodiment of the invention;

Figure 2 shows a block diagram of circuitry of a measuring arrangement of the identification system;

Figure 3 shows a schematic side view of part of a measuring arrangement of the identification system;

Figure 4 shows a flow chart of an interpolation algorithm used in the system,-

Figure 5 shows a flow chart of a rotation algorithm used in the system;

Figure 6 shows a three dimensional view of an identification system, in accordance with a second embodiment of the system; and

Figure 7 shows an end view of the system of Figure 6.

Referring firstly to Figures 1 to 5 of the drawings, an identification system, in accordance with the invention, is illustrated and is designated generally by the reference numeral 10. The identification system 10 is intended particularly for use in obtaining predetermined biometric data of a person for the purposes of identifying that person. More specifically, the identification system 10 is intended for use in obtaining predetermined measurements of a person's hand for use in identifying that person.

The identification system 10 includes a referencing device in the form of a plate 12 of a non- conductive material on which a person's hand 14 (Figure 3) is receivable. To ensure repeatability of measurements, the referencing device 12 includes a locating means in the form of a stop member 16 mounted on the plate 12. As illustrated in Figure 1 of the drawings, the stop member 16 is mounted in such a position on the plate 12 that, for a person's right hand, it is received between the index finger and middle finger of the hand such that a web of the hand between the index finger and middle finger abuts against the stop member 16.

The identification system 10 further includes a signal injecting means 18 for injecting a measuring signal into the hand 14 of the person. The signal injecting means 18 includes a pad 20 (hereinafter referred to as a palm pad) upon which a palm of the person's hand 14 impinges when placed on the plate 12. The pad 20 is of an electrically conductive material and may be constituted by a part of a printed circuit board. A signal generating device in the form of an oscillator 22 is connected to the palm pad 20 to provide the measuring signal that is injected into the hand 14. It will be appreciated that the measuring signal is a non- lethal signal and is of a very high frequency, typically about 1MHz .

The identification device 10 further includes a measuring arrangement 24 arranged on the plate 12. The measuring arrangement 24 comprises a plurality of strips 26.1, 26.2, 26.3, 26.4 and 26.5. Each strip 26.1 to 26.5 is made up of a plurality of discrete pads 28 (hereinafter referred to as finger pads) .

Each finger pad 28 is also of an electrically conductive material and may also be constituted by part of a printed circuit board.

As illustrated in Figure 1 of the drawings, when the hand 14 is placed on the plate 12, the thumb is received on the strip 26.1, the index finger on the strip 26.2, the middle finger on the strip 26.3, the ring finger on the strip 26.4 and the little finger on the strip 26.5. In so doing, a fingertip contour, as defined, can be obtained for that person's hand 14.

Referring more particularly to Figure 2 of the drawings, it is to be noted that each finger pad 28 is connected to a multiplexer 30. The multiplexer 30 is controlled by control circuitry 32 which is constituted by a microprocessor.

An output from the multiplexer 30 is fed to a detector 34 which detects the presence or absence of a signal on the relevant finger pad 28 and, when a signal is detected on the pad 28, the strength of such signal. The output from the detector 34 is fed to an analogue/digital convertor 36 which is also under the control of the microprocessor 32. The output from the analogue/digital convertor 36 is, in turn, fed to a communications link in the form of an RS 232 link 38. This link 38 connects the circuitry to a signal processing means in the form of a computer 39. The computer 39 effects a comparison between a measured fingertip contour and a stored fingertip contour, as will be described in greater detail below.

Referring now to Figure 3 of the drawings, it is to be noted that each strip 26 comprises a string of a predetermined number of pads. Typically, to cater for various sizes of hands, each strip 26 comprises between about 15 to 2 pads 28. The pitch P between adjacent finger pads 28 is relatively coarse. For example, the pitch between adjacent finger pads 28 is approximately 5mm. The magnitude of the pitch will be dependent on the required level of security, degree of accuracy and cost of the system 10. It will be appreciated that, the coarser the pitch P of the finger pads 28, the lower the accuracy but the higher the speed and the lower the cost of the system will be. Conversely, the smaller or finer the pitch P between adjacent finger pads 28 is, the higher the accuracy will be with resultant lower speed and higher cost.

The disadvantages associated with a coarse pitch P are, to a large extent, obviated by an interpolation algorithm used in the computer 39 in processing the signals measured at the finger pads 28, as will be discussed below.

In use, initially the biometric data relating to the fingertip contour of the hand 14 is obtained and is stored in the computer 39. Instead of storing this date in the computer 39, it may be stored in a portable information-carrying device such as, for example, a magnetic stripe of a card. Then, the data is read from the information-carrying device by the computer prior to commencement of the identification process. Thereafter, when it is desired to identify the person, the person places his hand 14 on the plate 12 such that the fingers are arranged on the strips 26.1 to 26.5 as described above.

The microprocessor 32 activates the oscillator 22 which injects a signal into the person's hand via the palm pad 20. In respect of each strip 26.1 to 26.5, the microprocessor 32 then instructs the multiplexer 30 to sense the signal strength at each finger pad 28 in each strip. This is done sequentially. In other words, firstly, the outermost finger pad 28.1 in the strip 26.1 is measured followed by the remaining pads in the strip 26.1. Thereafter, the outermost finger pad 28.1 in the strip 26.2 is sensed and so on.

Each time the detector 34 senses a signal at a finger pad 28, a measure of the signal's strength is forwarded via the RS 232 link 38 to the computer 39 where data relating to that signal strength are processed. In particular, to effect the required accuracy, the computer includes the interpolation algorithm, a flow chart of which is illustrated in Figure 4 of the drawings. Thus, for example, in respect of the strip illustrated in Figure 3 of the drawing there will be no signal on the outermost pad 28.1 as it is not covered by any part of the finger. If no signal is detected, the next pad is sensed. In other words, the signal at pad 28.2 is measured and is stored as signal

51. Data relating to that finger pad are also stored.

Then, the signal at pad 28.3 is measured. Because pad 28.3 is fully covered by a finger of the hand 14, and being close to the tip of the finger, reasonable pressure is exerted on the pad 28.3 and it can be assumed that maximum signal strength or close to maximum signal strength will be present at pad 28.3. The maximum signal strength varies from person to person and will also be dependent on a number of factors such as, for example, dryness of skin.

Referring again to Figure 3 of the drawings it is noted that the finger only partially covers pad 28.2 and, as a result, a signal of reduced strength will be sensed there. The ratio between the signal strength and the pads 28.2 and 28.3 is an indication of the amount of overlap of the finger on pad 28.2. Thus, once the signal has been sensed at pad 28.3, this signal is stored as

52. Then, by means of an appropriate arithmetic equation, an interpolation is effected between signals SI and S2 to derive finger length. By means of the interpolation algorithm, the accuracy of measuring the finger length is improved in comparison to the accuracy which would be achieved using the pitch P of the finger pads 28 only.

Thus, for example, in respect of a pitch P of about 5mm between the finger pads 28 using the interpolation algorithm illustrated, the "resolution" of the system is improved to about 1.25mm.

It will be appreciated that this interpolation algorithm need only be carried out in respect of the first finger pad 28 in respect of which a signal is detected and the next, inner pad in respect of which it can be assumed that maximum signal strength will be detected.

Although the measurement of the fingertip contour takes place m sequence in respect of each strip and in respect of each finger pad 28 in the strip 26, it will be appreciated that the speed with which this can be done electronically provides a rapid measurement of the fingertip contour.

Once the fingertip contour has been measured, the measured data are rotated and compared with the data which was originally stored in respect of that person. If there is sufficient similarity, a positive identification will result and, conversely, if the difference is more than a set limit, a negative identification will result.

A flow chart of a rotation algorithm included m software of the computer 39 is shown m Figure 5 of the drawings. Thus, firstly, a difference "FACTOR" between the measured thumb length and data relating to the thumb length previously stored m the computer s determined. Because the stop member 16 is located between the index finger and the middle finger, the "FACTOR" applied to the measured thumb length and measured index finger length will be positive or negative as the case may be while the "FACTOR" applied to the remaining measured finger lengths will be of opposite polarity The "FACTOR" applied to each finger is related to a scale factor, Ml to M4, assigned to each finger.

Of importance m the comparator is the algorithm that is used for establishing correspondence between the measured data and the stored data. An available technique s the so-called multivanate "T- test" which is well known in statistical analysis to give a quantified indication of the correspondence achieved. Referring now to Figures 6 and 7 of the drawings, an identification system, in accordance with another embodiment of the invention is illustrated. With reference to the previous drawings, like reference numerals refer to like parts, unless otherwise specified.

In this embodiment of the invention, instead of a plate 12, the referencing device is in the form of a cylinder 40 about which a person's 14 is placed. The cylinder 40 has an outer diameter which is such that, when the person's hand 14 is placed about an outer surface 42 of the cylinder 40, the tips of the person's thumb 14.1 and fingers 14.2 to 14.5 do not touch.

Further, to locate the hand 14 in position on the measuring arrangement 24 (which is arranged on the outer surface 42 of the cylinder 40) , stop members 44 and 46 (Figure 7) are provided on the outer surface 42 of the cylinder 40. The stop member 44 is fixed and the tip of the thumb 14.1 abuts against the stop member 44. The stop member 46 is slidable along the outer surface 42 of the cylinder 40 in the direction of arrows 48 and the tip of one of the fingers 14.2 to 14.5 abuts against the stop member 46.

In this embodiment of the invention, the signal injecting means 18 includes an elongate central strip 50 extending longitudinally along the outer surface 42 of the cylinder 40, three strips 52, 54 and 56 extending from one side of the strip 32 in a circumferential direction about the outer surface 42 of the cylinder 40 and a further strip 58 extending from the other side of the strip 50. The measuring arrangement 24 then comprises the pads 28. Additionally, further strips of pads 60 are provided adjacent the strip 50, at each end thereof. The pads 60 are used for measuring the width of the hand 14 in the same manner as that described above with reference to the measurement of the lengths of the fingers 14.1 to 14.5. It will be appreciated that the pads 60 are also then connected to the multiplexer 30.

The operation of the embodiment of the invention illustrated in Figures 6 and 7 is the same as that described above with reference to Figures 1 to 5 of the drawings.

It is a particular advantage of the invention that an identification system 10 is provided which utilises biometric data without the need for cumbersome optical circuitry. Further, by using the interpolation algorithm, the identification system 10 has the benefit of high speed and low cost while still providing adequate security for most applications. Should additional security be required, the system 10 can be used in conjunction with a further identification code such as a personal identification number or PIN. A further advantage of the system 10 is that slight differences in placement of the hand on the plate 12 or cylinder 40, as the case may be, are compensated for by means of the rotation algorithm thereby reducing the likelihood of false rejections.

Claims

1. An identification system for identifying a person, the identification system including a referencing device on which a predetermined part of a person's body is receivable; a signal injecting means carried by the referencing device for injecting a measuring signal into said part of the person's body; a measuring arrangement carried by the referencing device for measuring predetermined parameters of the part of the person's body by measuring the strength of the measuring signal at predetermined positions on the referencing device and for generating a measured signal representative of said measured parameters,- and a signal processing means for processing said measured signal to provide an output signal indicative of the identity of the person.

2. The system as claimed in Claim 1 in which the referencing device is of a non-conductive material and in which the signal injecting means is an element of a conductive material arranged on a surface of the referencing device.

3. The system as claimed in Claim 2 in which the signal injecting means includes a signal generating device connected to the element.

4. The system as claimed in Claim 2 or Claim 3 in which the measuring arrangement includes a plurality of strips of electrically conductive material, the strips being arranged on the referencing device and being electrically isolated from one another and from the element.

5. The system as claimed in Claim 4 in which each strip comprises a plurality of discrete pads, the pads being electrically isolated from one another.

6. The system as claimed in Claim 4 or Claim 5 in which a strip is provided for each of at least certain fingers, including a thumb, of a hand of a person for measuring the lengths of said fingers.

7. The system as claimed in Claim 6 in which additional strips are provided for measuring a width of the hand.

8. The system as claimed in any one of Claims 5 to 7 inclusive in which the measuring arrangement includes a signal strength detector for detecting a signal strength in respect of each pad of the measuring arrangement .

9. The system as claimed in Claim 8 in which the measuring arrangement includes control circuitry for controlling operation of the measuring arrangement, the control circuitry including a microprocessor for generating logic control signals for addressing each pad of the measuring arrangement as well as for processing the signal strengths read from each of said pads via the detector and an appropriate analogue/digital conversion means.

10. The system as claimed in any one of the preceding claims in which the signal processing means is operable to improve the accuracy of the measured signal output by the measuring arrangement.

11. The system as claimed in Claim 10 in which the signal processing means includes software which includes an interpolation algorithm for processing the measured signal to improve the accuracy of the measured signal.

12. The system as claimed in Claim 11 in which the software further includes a rotation algorithm for compensating for placement of the part of the person's body on the referencing device.

13. The system as claimed in any one of the preceding claims in which the referencing device includes a locating means for ensuring that the part of the person's body is correctly placed on the measuring arrangement.

14. The system as claimed in any one of the preceding claims in which the referencing device is a plate on which the part of the person's body is receivable.

15. The system as claimed in any one of Claims 1 to 13 inclusive in which the referencing device comprises a cylinder about which the part of the person's body is placed.

16. A method of identifying a person which includes injecting a signal into a predetermined part of a person' s body; measuring the strength of the signal at predetermined locations relative to said parts of the person's body to provide a measured signal representative of measured parameters of the part of the body; and processing said measured signal to provide an output signal indicative of the identity of the person.

17. The method as claimed in Claim 16 which includes injecting the signal into a hand of the person and measuring^" the signal at various positions in respect of at least certain of the fingers of the hand to obtain data relating to the lengths of said fingers. - 2H -

18. The method as claimed in Claim 17 which includes, additionally, measuring the width of the hand.

19. The method as claimed in any one of Claims 16 to 18 inclusive which includes processing the measured signal by carrying out an interpolation operation on the signal to improve the accuracy of the measured signal.

20. The method as claimed in any one of Claims 16 to 19 inclusive which includes utilizing a rotational algorithm on the measured signal to compensate for placement of said part of the person's body on a measuring arrangement which obtains said measured parameters of the person's body.