CA1068146A - Exposure control device for photographic copier - Google Patents
Exposure control device for photographic copierInfo
- Publication number
- CA1068146A CA1068146A CA255,767A CA255767A CA1068146A CA 1068146 A CA1068146 A CA 1068146A CA 255767 A CA255767 A CA 255767A CA 1068146 A CA1068146 A CA 1068146A
- Authority
- CA
- Canada
- Prior art keywords
- exposure
- output
- variable
- steps
- control device
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
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- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
- G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
- G03F7/20—Exposure; Apparatus therefor
- G03F7/2002—Exposure; Apparatus therefor with visible light or UV light, through an original having an opaque pattern on a transparent support, e.g. film printing, projection printing; by reflection of visible or UV light from an original such as a printed image
- G03F7/2014—Contact or film exposure of light sensitive plates such as lithographic plates or circuit boards, e.g. in a vacuum frame
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- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03B—APPARATUS OR ARRANGEMENTS FOR TAKING PHOTOGRAPHS OR FOR PROJECTING OR VIEWING THEM; APPARATUS OR ARRANGEMENTS EMPLOYING ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ACCESSORIES THEREFOR
- G03B27/00—Photographic printing apparatus
- G03B27/72—Controlling or varying light intensity, spectral composition, or exposure time in photographic printing apparatus
- G03B27/80—Controlling or varying light intensity, spectral composition, or exposure time in photographic printing apparatus in dependence upon automatic analysis of the original
Abstract
Abstract of the Disclosure This invention relates to a control device, suitable for use to control the exposure of a light-sensitive material in a copying appara-tus for the preparation of a printing plate, which comprises program store means for predetermining a basic exposure, input line means for connection to a photocell for measuring the luminous intensity of a light source in the copying apparatus, comparator means having its input connected to an output of the program store means and connected by a transmission path means to the input line means, the output of the com-parator means being connectable to a control switch for the light source, and the transmission characteristics of the path being variable in steps, adjacent pairs of which have transmissivities in the ratio
Description
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` \ ~068146 K-2399 CONTROL DEVICE AND COPIER
This mvention relates to a control device, especially a device for controlling the exposure of light-sensitive materials.
The invention provides a device for controlllng the amount of light for exposing light-sensitive material in copying apparatus for the preparation of printing blocks, which material is exposed to a light source (copying lamp~ through a copy original, the device having at least one program store, which is adjustable in particular in uniform gradation in accordance with the amount of light, for predetermining a basic exposure time which may be varied to take into account the lumi- ;~
nous intensity value, with an electric photoreceiver or photocell mea-suring the luminous intensity value and with an integrating comparator which, for the comparison of a value stored in the program store with the integrated lumlnous intensity value, is connected on the one hand ; ~ to the program store and on the other hand to the photorecelver, and the output of this lntegrating comparator is connected to a regulating unit or on-off switch for the light source.
An arrangement of this type has been proposed in an exposure control apparatus and comprises a program store with four channels. In each channel a desired exposure time can be set manually by a digital transmitter. To take into account the brightness of the copying lamp, ; varying, for example, in accordance with main voltage, an electric photoreceiver is provided which is directed at the copying lamp and mea-sures a portion of the light flux leaving the lamp as a luminous inten~
sity value. The electric output signal of the photoreceiver is converted ; into a corresponding pulse frequency and supplied to a counter preset with the digital transmitter until this counter reaches zero. The counter therefore serves to compare the digital reference value that has been ;~
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read in with the integrated actual value of the luminous intensity.
The times set with the transmitters and the termina~ion of the exposure time are indicated on setting elements or on a digital scale.
In such an exposure control apparatus various exposure times can be set and stored for example, for different types of plates or -~
for exposure times diiferentiated for proof copies or for continuous printing runs in *he case of the same types of plates. Differentiated ; expos~re times for proofs and separate prints are desirable in many cases since in production printing machines an increase in the tone value occurs in comparison with the printed image produced with a flat bed proof press. This increase in tone value can be substanti-ally compensated by controlled prolongation of exposure.
In order to assess the alterations of exposure on the print-ing plate necessary for this or for other purposes, a transparent-grey scale according to German Industrial Standard No. 16,545 is normally copied as well. The effect of the exposure time is assessed by means of this gray scale depending upon the last step of the grey scale still remaining fully covered on the plate, variations in exposure being assessed from step to step of the grey scale.
- 20 The alteration to a basic exposure time necessary for particular - grey scale steps which are to be covered have previously been deter-mined empirically. The required alterations of the basic exposure time were estimated or calculated by the operating personnel and introduced into one of the e.g., four channels of the program store which can be selectively introduced into the circuit. The program store may be so constructed that an exposure time selected from any of 999 uni-form steps may be fed into each channel, so that in particular the sensi-tivity of the printing plate to be exposed can be accurately taken into
` \ ~068146 K-2399 CONTROL DEVICE AND COPIER
This mvention relates to a control device, especially a device for controlling the exposure of light-sensitive materials.
The invention provides a device for controlllng the amount of light for exposing light-sensitive material in copying apparatus for the preparation of printing blocks, which material is exposed to a light source (copying lamp~ through a copy original, the device having at least one program store, which is adjustable in particular in uniform gradation in accordance with the amount of light, for predetermining a basic exposure time which may be varied to take into account the lumi- ;~
nous intensity value, with an electric photoreceiver or photocell mea-suring the luminous intensity value and with an integrating comparator which, for the comparison of a value stored in the program store with the integrated lumlnous intensity value, is connected on the one hand ; ~ to the program store and on the other hand to the photorecelver, and the output of this lntegrating comparator is connected to a regulating unit or on-off switch for the light source.
An arrangement of this type has been proposed in an exposure control apparatus and comprises a program store with four channels. In each channel a desired exposure time can be set manually by a digital transmitter. To take into account the brightness of the copying lamp, ; varying, for example, in accordance with main voltage, an electric photoreceiver is provided which is directed at the copying lamp and mea-sures a portion of the light flux leaving the lamp as a luminous inten~
sity value. The electric output signal of the photoreceiver is converted ; into a corresponding pulse frequency and supplied to a counter preset with the digital transmitter until this counter reaches zero. The counter therefore serves to compare the digital reference value that has been ;~
: ~ . . . ~ , , . . ................ , .. , ., . . . :
,,, ,', ,.:, , . .. ! . ~ ~ . .
-~ 6 ~ .
read in with the integrated actual value of the luminous intensity.
The times set with the transmitters and the termina~ion of the exposure time are indicated on setting elements or on a digital scale.
In such an exposure control apparatus various exposure times can be set and stored for example, for different types of plates or -~
for exposure times diiferentiated for proof copies or for continuous printing runs in *he case of the same types of plates. Differentiated ; expos~re times for proofs and separate prints are desirable in many cases since in production printing machines an increase in the tone value occurs in comparison with the printed image produced with a flat bed proof press. This increase in tone value can be substanti-ally compensated by controlled prolongation of exposure.
In order to assess the alterations of exposure on the print-ing plate necessary for this or for other purposes, a transparent-grey scale according to German Industrial Standard No. 16,545 is normally copied as well. The effect of the exposure time is assessed by means of this gray scale depending upon the last step of the grey scale still remaining fully covered on the plate, variations in exposure being assessed from step to step of the grey scale.
- 20 The alteration to a basic exposure time necessary for particular - grey scale steps which are to be covered have previously been deter-mined empirically. The required alterations of the basic exposure time were estimated or calculated by the operating personnel and introduced into one of the e.g., four channels of the program store which can be selectively introduced into the circuit. The program store may be so constructed that an exposure time selected from any of 999 uni-form steps may be fed into each channel, so that in particular the sensi-tivity of the printing plate to be exposed can be accurately taken into
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10~;814~ K-2399 account. To each step there corresponds in the transmitter one pulse of the pulse sequence, which is produced with a frequency depending upon the brightness of the copying lamp. 1l A disadvantage in these exposure control apparatuses is that necessary changes of the basic e~posure time, when they are to be carried out in a controlled manner, must first of all be determined by operating personnel, and the changes are generally carried out in accordance with experimental values or by time consuming and expen-sive preliminary tests. Calculation of any exposure time that is differ-ent from the basic exposure time, is, if it has to be done by operating personnel, both time consuming and susceptible to error. These dis- ¦
advantages of the calculation occur in particular when the exposure must be altered in accordance with a grey wed~e step, which corre-sponds to a calculating operation with the value ~r2. The transmission of the result of the calculation into the transmitter of the program store ,, . :
- introduces a further possibility of error. In addition to this, the cal-culated values cannot be easily reproduced quickly and reliably.
It would be desirable to provide a circuit arrangement suitable, jJ
.' I , .
; lnter alia, for controlling the exposure time of light-sensitive material in copying apparatus for the production of printing forms, avoiding the above-mentioned disadvantages, and in which the exposure time can be adapted quickly and reliably to the particular conditions involved with-out changing the basic setting of the program store, which conditions, may, for example, reside in the different intended use of the printing plates produced or in the exposure of colored films associated with different colors. Time consuming and error causing calculations by the operating personnel should be avoided, and it should be possible to vary the basic exposure time quickly, clearly and inaneasily reproduc-ible manner, with minimum expenditure.
:: .
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10~;814~ K-2399 account. To each step there corresponds in the transmitter one pulse of the pulse sequence, which is produced with a frequency depending upon the brightness of the copying lamp. 1l A disadvantage in these exposure control apparatuses is that necessary changes of the basic e~posure time, when they are to be carried out in a controlled manner, must first of all be determined by operating personnel, and the changes are generally carried out in accordance with experimental values or by time consuming and expen-sive preliminary tests. Calculation of any exposure time that is differ-ent from the basic exposure time, is, if it has to be done by operating personnel, both time consuming and susceptible to error. These dis- ¦
advantages of the calculation occur in particular when the exposure must be altered in accordance with a grey wed~e step, which corre-sponds to a calculating operation with the value ~r2. The transmission of the result of the calculation into the transmitter of the program store ,, . :
- introduces a further possibility of error. In addition to this, the cal-culated values cannot be easily reproduced quickly and reliably.
It would be desirable to provide a circuit arrangement suitable, jJ
.' I , .
; lnter alia, for controlling the exposure time of light-sensitive material in copying apparatus for the production of printing forms, avoiding the above-mentioned disadvantages, and in which the exposure time can be adapted quickly and reliably to the particular conditions involved with-out changing the basic setting of the program store, which conditions, may, for example, reside in the different intended use of the printing plates produced or in the exposure of colored films associated with different colors. Time consuming and error causing calculations by the operating personnel should be avoided, and it should be possible to vary the basic exposure time quickly, clearly and inaneasily reproduc-ible manner, with minimum expenditure.
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- 3 -~ K-~399 `` 10~8146 The present invention provides a control device suitable for use, for example, with apparatus for making printing forms from light-sensitive materials by exposure to a light source, in which control sys-tem there is provided a transmission path ior a signal having a property dependent upon the strength of the light source to a control device for the duration of exposure, the transmission behavior of the signal trans-mission path being variable in a series of steps; preferably the steps are such that, for a given originating signal, adjacent steps vary the signal to the control device by ratios of ~r2.
The invention also provides a copying appara-tus having the con-trol device of the invention, whereby the exposure of an original and a Iight-sensitive material may be step-wise varied, adjacent steps giving exposures in a ratio of ~
Independently-of the setting of the program store, the apparatus , allows a change of the set exposure time in a simple predetermlned wayby a varlable transmission member arranged between the photoreceiver and the comparator. By this means the exposure time can be varied beginning from any set basic exposure time in accordance with steps predetermined initially and thus quickly adjustable and reproducible.
Time consuming preliminary tests which involve expenditure and com-plicated calculations causing errors are avoidable.
When a multivalue digital program store is used, the transmis-sion member variable in predetermined steps is advantageously arranged between the photoreceiver and the comparator.
If the program store does not have several digital positions, the arrangement of the type initially mentioned is alternatively formed in accordance with the invention also in the manner that, to change the basic exposure time by one of several predetermined factors, at least
The invention also provides a copying appara-tus having the con-trol device of the invention, whereby the exposure of an original and a Iight-sensitive material may be step-wise varied, adjacent steps giving exposures in a ratio of ~
Independently-of the setting of the program store, the apparatus , allows a change of the set exposure time in a simple predetermlned wayby a varlable transmission member arranged between the photoreceiver and the comparator. By this means the exposure time can be varied beginning from any set basic exposure time in accordance with steps predetermined initially and thus quickly adjustable and reproducible.
Time consuming preliminary tests which involve expenditure and com-plicated calculations causing errors are avoidable.
When a multivalue digital program store is used, the transmis-sion member variable in predetermined steps is advantageously arranged between the photoreceiver and the comparator.
If the program store does not have several digital positions, the arrangement of the type initially mentioned is alternatively formed in accordance with the invention also in the manner that, to change the basic exposure time by one of several predetermined factors, at least
- 4 ~
~ ` 10~i~3146 one transmission member is arranged in the transmission path between the program store and the comparatorJ the transmission behavior of which member is variable in predetermined steps. The circuit arrange-- ment is especially advantageous when the program transmitter delivers a signal of magnitude depending on the desired basic exposure time, in particular a voltage of adjustable level.
It is particularly advantageous in the arrangements of the two aforementioned constructional variations if the variable transmission member is such that the change in the amount of light for each step corresponds to the adjacent stage of a grey scale ~according to German Industrial Standard No. 16,545).
As a result the set basic exposure time can be varied quickly, simply and without error and a previously determined effect can be con-sistently achieved. In order to lengthen or shorten the exposure time by one grey scale step respectively, the "basic" exposure time does not have to be altered. If, for example, the basic exposure time is ad-justed to step 5 of a 20-step grey scale ~according to German Industrial Standard No. 16,545) wi~h the appropriate grey scale step covered by turning a switch to one particular position, by turning the switch in a given direction from the basic position, the grey scale step 4 appears covered.
It has proved adequate, and in view of the cost of the arrange-ment particularly advantageous, to design the variable transmission member with fours steps for lengthening the exposure time and four steps for shortening the exposure time, from a basic central position.
Preferably, the transmission member, which can be changed over, is designed so that the transmission characteristic can be changed over in the steps ~ 1; (2 ~ ) 1; 2 1, ~2 1; 1; ~2; 2; 2 ~ ;
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106~3~4~ K-2399 With these ratios, another grey scale step is covered for each step of the variable transmission member.
For an arrangement which is provided with a digital program store, the arrangement is advantageously so designed that a voltage *equency converter is arranged in the transmission path between the photoreceiver and the comparator, and that an adjustable frequency divider is arranged after the voltage frequency converter in the direction of flow of the signal. With the adjustable frequency divider, the desired transmission behavior can be achieved very accurately with relatively low expenditure. The frequency divider, advantageously, comprises one chain of trigger stages connected in series. The input of the first trigger stage of the series is fed with a pulse sequence from the voltage *equency converter. The trigger stage is basically a frequency halver, i.e. a reduction of the pulse frequency by a factor of 2 occurs between the input and output of this trigger stage. The output from each trigger stage, except the last, is connected to the input of the next, and each output is also connected to a pole of a multiposition switch. The basic exposure time is set when the switch is switched to the output of a particular trigger stage which in the direction of flow of the signal in the series of trigger stages itself follows a number of trigger stages, and to which, in turn, a number of trigger stages are connected. If the switch is switched to a trigger stage Iying before the determined trigger stage in the direction of flow of the signal, then there is a multiplica-tion of the pulse frequency, which corresponds to a shortening of the exposure time. Conversely, when the changeover switch is switched to one of the trigger stages after the determined trigger stage in the direction of flow of the signal, a reduction of the pulse repetition fre-quency occurs and similarly there is a prolongation of the exposure ~ ~1~i8~46 time. With this arrangement alternate steps of a 20-step grey scale could be achieved simply and reliably.
Change of the exposure time to any grey scale step lying between those provided by the above system, by which the exposure time may be varied :-: at a ratio ofv~~, is advantageously achieved in another manner:
For this purpose there is arranged in the direction of flow of thesignal before the voltage frequency converter, a variable voltage divider, with which, for example, three positions are provided having a series of ratios of v~~; l; or ~ -1.
The multiplication of the signal delivered by the photo-receiver by a factor which is not a whole number or by a factor which is not a fraction of a whole number is thus achieved by particularly low expenditure by alter-ing the voltage but not by altering the pulse frequency corresponding to it.
Here a voltage which has not been reduced can correspond to the factor v'~, a correspondingly lower value to the factor 1 and a lower value again to the factorv~
To monitor the precise method of operation of the arrangement under different conditions, advantageously the apparatus is provided with a voltage indicator in the circuit before the voltage divider in the direction of flow of the signal.
Independently of the change-over position of the transmission member which can be changed-over, it is possible to determine whether following the voltage indicator in the direction of flow of the signal all switching groups and switching elements are operating in the linear transmission range.
In accordance with this invention there is provided an exposure con-trol device, suitable for use to control the exposure of a light-sensitive material in a photographic copier apparatus for the preparation of a printing plate, which comprises program store means for predetermining a basic exposure, ~ input line means connected to a photocell for measuring the luminous intensity - 30 of a light source in the copier apparatus, comparator means having its input - connected to an output of the program store means and connected by a trans-mission path means to the input line means, the output of the comparator means .
. , : : . :
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. being connected to a control switch for the light source, and means for varying the transmission characteristics of the path in steps, adjacent pairs of which have transmissivities in the ratio v~
In accordance with another aspect of this invention there is provided a control device, suitable for use to control the exposure of a light-sen-. sitive material in a copying apparatus for the preparation of a printing plate, which comprises program store means for predetermining a basic exposure, . input line means connected to a photocell for measuring the luminous intensity :...................................................................... .
` of a light source in the copying apparatus, comparator means having its input connected to an output of the program store means by a transmission path ., means and connected to the input line means, the output of the comparator means being connected to a control switch for the light source controlling the exposure of the light-sensitive material imagewise exposed by the light source and the transmission characteri~.tics of the path being variable in steps by i switching means provided in the transmission path means adjacent steps of which switching means have transmissivities in the ratio ~-:1.
~ne form of apparatus constructed in accordance with the invention ... .
will now be described by way of example, with reference to the accompanying drawings, in which :, .' '. " .
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~ - 7a -., 10~i8146 Fig. 1 shows the apparatus in the form of a schema~ic block diagram, and - Fig. 2 shows the variable voltage divider and the variable ~e-quency converter which form an important part of the apparatus, also in a schematic circuit diagram.
In Fig. 1, in addition to the block diagram of the control appara- -tus, a copying apparatus 10, in which the exposure is to be controlled, is also shown schematically. The copying apparatus comprises a copy-lng frame 11, on which light-sensitive material 12, for example a print-ing plate, and a transparent original 13 are arranged. A copying lamp 14 is used to illuminate the light-sensitive material through the copy 1 ;original. The copying lamp 14 is in electrical contact with a regulating unit 15. The luminous intensity produced by the copying lamp 14 in the exposure plane is measured by an electric photoreceiver (photocell) 16.
, These parts belong to the copying apparatus. The electric elements and structural groups described below are part of a control apparatus, and may be arranged in a housing which is spatially separate from the copy-ing apparatus.
The control arrangement is in electrical contact with the photo-cell 16 and with the regulating unit (switch) 15. The output of the photo-cell 16 is connected to an amplifier 17. The amplified output voltage may be measured by a vGltage indicator 17a. After the amplifier 17 in the direction of flow of the signal are a variable voltage divider 18, a voltage frequency converter (e.g. a voltage-controlled oscillator) 19 and a variable frequency reducer 20. Control elements 18a and 20a of the voltage divider and of the frequency divider are, as indicated by a broken line 21, ganged and are adjustable by a single control knob, not shown in the drawing. The constructions of the voltage divider 18 and 1(~6~3146 K -2 3 9 9 .
the frequency divider 20 are described in greater detail below with reference to Fig. 2.
!' The output of the adjustable frequency reducer 20, which is a signal composed of a series of pulses, is connected to an integrating comparator which is basically a pulse counter. The counter can be preset by way of a program store having a numerical setting member 23.
With the latter the counter can be set to values between 0 and 999 .:.
` pulses. When the output of the frequency divider 20, i.e., pulses corresponding to the luminous intensity measured by the photoreceiver 16 and in accordance with the switch positions of elements 18a and 20a, reaches the counter 22, it is reset by one step for each pulse, ; until it reaches the value 0. The value reached in the counter is shown by a digital indicator 24. When the zero value is reached, an appro-prlate signal passes to the control device 25, positioned downstream in the direction of flow of the signal, which is an order to the switch 15 to switch off the copying lamp.
Also connected to the control device is a starting means 26 whlch is actuated when an exposure operation is to begin~ In this case the switch 15 is closed so that the copying lamp 14 lights up. A portion of the light flux issuing from the copying lamp 14 is received by the photoreceiver 16 which delivers an electrical signal, corresponding to the luminous intensity, to the amplifier 17. This signal is indicated by ; the voltage indicator 17a. By this means the operating personnel can check whether the luminous intensity lies within those limits which are to be observed for the operation of the circuit arrangement in a desired characteristic curve range.
Referring now more especially to Fig. 2, the output from the am-plifier passes into the va~iable voltage divider 18, and from there, 4~ K-2399 possibly attenuated according to the position of the switch element 18a, into a voltage frequency converter which produces a pulse at a frequency corresponding to the voltage. The output of the voltage fr,equency con-verter 19 is connected to the variable frequency divider 20 which com-prises four trigger stages 27 to 30 and a switch element 20a. The switch element 20a has nine schematically illustrated contacts beside which the variation factors from the basic exposure time are indicated on Fig.
2. The pulses fed into the variable frequency divider pass into the input of the first trigger stage 27. Each of the trigger stages 27, 28, 29 and 30 is a frequency halver and hence the signal output from each is one pulse for every two input pulses. Accordingly there is a reduction by a factor of 2 at each of the trigger stages 27, 28, 29 and 30. The entire clrcuit arrangement is so designed that the basic exposure time is associated wLth a pulse frequency which appears at the output of the trigger stage 28, since a numerical unit of the number introduced with the numerical setting member 23 corresponds to each pulse at the output of the trigger stage 28. If the pulse frequency is taken at the output of the trigger stage 27 by the chosen position of the switching element 20a, the pulse frequency is twice as high as that at the output of the trigger stage 28; this results in a halving of the basic exposure time.
The pulse frequency at the input of the trigger stage 27 is four times as high as the pulse frequency at the output of the trigger stage 28. By setting the switching element 20a to the input of the trigger stage 27, a fourfold pulse frequency is therefore conveyed to the line coming off the change-over element 20a, which corresponds to a quarter of the basic exposure time.
Conversely, there occurs at the output of the trigger stage 29 a halving of the pulse frequency in comparison with the output of the ,. . . . . . . . .
1061~4tii K-2399 .-' trigger stage 28, so that by appropriate adjustment of the change-over element 20a a halved pulse frequency appears which results in a doubl-ing of the basic exposure time. By setting the change-over element to the contact marked 4, only every fourth pulse released from the output of the trigger stage 28 appears; the result is an exposure time that is four times as long.
With the adjustable frequency reducer 20 it is possible, there-fore, with low expenditure, to produce very accurate pulse freqllencies which are complete even-numbered multiples of a pulse frequency or of its reciprocal values. For the steps Iying inbetween, which are formed by the factor~ or its reciprocal value, the variable voltage divider 18 is used. This voltage divider is so designed that at a middle tapping 31 the input voltage is reduced by the factor \r2 1. The voltage output from this tapping corrésponds, according to the basic design of the appa-;; ! ratus, to a variation factor 1 of the basic exposure tlme, i.e. the normal basic exposure time. The undivided voltage, which is fed into the variable voltage divider which can be changed over, is thus greater by the factor ~ than the voltage at the tapping 31. This corresponds to an exposure time reduced by the factor ~r2 1. Conversely, when vol-tage is taken at a lower tapping 32, the voltage is reduced by the value \/~ 1 in comparison with the middle tapping 31. The result is an e~po-sure time longer by the factor ~
It may be seen from Fig. 2 that the change-over elements 18a and 20a are so coupled with one another that there is associated with the variation factors formed with even numbers the middle tapping 31 of the variable voltage divider, and associated with the variation factors formed with the factor ~ the lower tapping 32, and with the variation factors formed with the factor ~r2 finally the complete input signal at the variable voltage divider.
In the following, a table shows the connections which can be achieved with the arrangement between the positions of the ganged, switching elements 18a and 20a, and the variation factors achieved thereby, and an example of the resulting grey scale steps and the corre-sponding blackenings.
change-over -4 -3 -2 -1 0 +1 ~2 +3 +4 position variation factors 4 1 (2~r2) 1 2 1 ~2 1 1 ~/2 2 2~ 4 of the basic ex-posure time grey scale step 5 6 7 8 9 10 11 12 13 blackening 0 . 75 0 . 9 1. 05 1 . 2 1. 351. 5 1 . 65 1. 8 1. 95 Withthe described arrangement, exposure can be carried out, for example, in the following manner:
For a printing plate 12 which is to be exposed, it may be assum-~ ed that the manufacturer has indicated a basic exposure time of 100 units ; which are set with the numerical setting member 23 of the program store.
; If the basic exposure time is not altered, the grey scale step 9 would thus stand covered on the printing plate. With such a printing plate ;
there are to be produced from an original a proof plate, which is to be used in a flat bed proof press, and a machine plate which is to be intro-i:, " , 20 duced into a production machine. It has been ascertained internally that the proof plates produce optimum results at step 6 and machine plates at step 11 covered. To obtain these results with the arrangement, the ganged switching elements 18a and 20a need for the proof plate merely .i.
to be set to the switch position -3, and for the machine plate to the switch position +2. Without altering the setting member 23 the copy result will turn out as desired for both intended purposes of the printing . . .
plates .
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~l0~ 4~ K-2399 A further example of the application of the control device is in the exposure of different color films of an original. In this case, let it be assumed that at a basic exposure time of 85 pulses set in the program store 23, a color film RED is correctly exposed. For a color film YELLOW, on the other hand, double the exposure time is necessary according to the operating instructions. Without altering the setting member 23, this can be achieved simply by setting the switching ele-ments 18a and 20a to position +2. On the other hand a color film BLUE
requires an exposure time shorter by the factor ~r2 1, Without having to calculate in a complicated manner quotient of 85 pulses by ~/ 2, the optimum exposure time will occur by changing the elements 18a and 20a to the position -1.
It will be obvious to those skilled in the art that many modifi-cations may be made within the scope of the present invention without departing from the spirit thereof, and the invention lncludes all such modifications.
.~ , , .'~ ' i
~ ` 10~i~3146 one transmission member is arranged in the transmission path between the program store and the comparatorJ the transmission behavior of which member is variable in predetermined steps. The circuit arrange-- ment is especially advantageous when the program transmitter delivers a signal of magnitude depending on the desired basic exposure time, in particular a voltage of adjustable level.
It is particularly advantageous in the arrangements of the two aforementioned constructional variations if the variable transmission member is such that the change in the amount of light for each step corresponds to the adjacent stage of a grey scale ~according to German Industrial Standard No. 16,545).
As a result the set basic exposure time can be varied quickly, simply and without error and a previously determined effect can be con-sistently achieved. In order to lengthen or shorten the exposure time by one grey scale step respectively, the "basic" exposure time does not have to be altered. If, for example, the basic exposure time is ad-justed to step 5 of a 20-step grey scale ~according to German Industrial Standard No. 16,545) wi~h the appropriate grey scale step covered by turning a switch to one particular position, by turning the switch in a given direction from the basic position, the grey scale step 4 appears covered.
It has proved adequate, and in view of the cost of the arrange-ment particularly advantageous, to design the variable transmission member with fours steps for lengthening the exposure time and four steps for shortening the exposure time, from a basic central position.
Preferably, the transmission member, which can be changed over, is designed so that the transmission characteristic can be changed over in the steps ~ 1; (2 ~ ) 1; 2 1, ~2 1; 1; ~2; 2; 2 ~ ;
.
.
106~3~4~ K-2399 With these ratios, another grey scale step is covered for each step of the variable transmission member.
For an arrangement which is provided with a digital program store, the arrangement is advantageously so designed that a voltage *equency converter is arranged in the transmission path between the photoreceiver and the comparator, and that an adjustable frequency divider is arranged after the voltage frequency converter in the direction of flow of the signal. With the adjustable frequency divider, the desired transmission behavior can be achieved very accurately with relatively low expenditure. The frequency divider, advantageously, comprises one chain of trigger stages connected in series. The input of the first trigger stage of the series is fed with a pulse sequence from the voltage *equency converter. The trigger stage is basically a frequency halver, i.e. a reduction of the pulse frequency by a factor of 2 occurs between the input and output of this trigger stage. The output from each trigger stage, except the last, is connected to the input of the next, and each output is also connected to a pole of a multiposition switch. The basic exposure time is set when the switch is switched to the output of a particular trigger stage which in the direction of flow of the signal in the series of trigger stages itself follows a number of trigger stages, and to which, in turn, a number of trigger stages are connected. If the switch is switched to a trigger stage Iying before the determined trigger stage in the direction of flow of the signal, then there is a multiplica-tion of the pulse frequency, which corresponds to a shortening of the exposure time. Conversely, when the changeover switch is switched to one of the trigger stages after the determined trigger stage in the direction of flow of the signal, a reduction of the pulse repetition fre-quency occurs and similarly there is a prolongation of the exposure ~ ~1~i8~46 time. With this arrangement alternate steps of a 20-step grey scale could be achieved simply and reliably.
Change of the exposure time to any grey scale step lying between those provided by the above system, by which the exposure time may be varied :-: at a ratio ofv~~, is advantageously achieved in another manner:
For this purpose there is arranged in the direction of flow of thesignal before the voltage frequency converter, a variable voltage divider, with which, for example, three positions are provided having a series of ratios of v~~; l; or ~ -1.
The multiplication of the signal delivered by the photo-receiver by a factor which is not a whole number or by a factor which is not a fraction of a whole number is thus achieved by particularly low expenditure by alter-ing the voltage but not by altering the pulse frequency corresponding to it.
Here a voltage which has not been reduced can correspond to the factor v'~, a correspondingly lower value to the factor 1 and a lower value again to the factorv~
To monitor the precise method of operation of the arrangement under different conditions, advantageously the apparatus is provided with a voltage indicator in the circuit before the voltage divider in the direction of flow of the signal.
Independently of the change-over position of the transmission member which can be changed-over, it is possible to determine whether following the voltage indicator in the direction of flow of the signal all switching groups and switching elements are operating in the linear transmission range.
In accordance with this invention there is provided an exposure con-trol device, suitable for use to control the exposure of a light-sensitive material in a photographic copier apparatus for the preparation of a printing plate, which comprises program store means for predetermining a basic exposure, ~ input line means connected to a photocell for measuring the luminous intensity - 30 of a light source in the copier apparatus, comparator means having its input - connected to an output of the program store means and connected by a trans-mission path means to the input line means, the output of the comparator means .
. , : : . :
~14 "
. being connected to a control switch for the light source, and means for varying the transmission characteristics of the path in steps, adjacent pairs of which have transmissivities in the ratio v~
In accordance with another aspect of this invention there is provided a control device, suitable for use to control the exposure of a light-sen-. sitive material in a copying apparatus for the preparation of a printing plate, which comprises program store means for predetermining a basic exposure, . input line means connected to a photocell for measuring the luminous intensity :...................................................................... .
` of a light source in the copying apparatus, comparator means having its input connected to an output of the program store means by a transmission path ., means and connected to the input line means, the output of the comparator means being connected to a control switch for the light source controlling the exposure of the light-sensitive material imagewise exposed by the light source and the transmission characteri~.tics of the path being variable in steps by i switching means provided in the transmission path means adjacent steps of which switching means have transmissivities in the ratio ~-:1.
~ne form of apparatus constructed in accordance with the invention ... .
will now be described by way of example, with reference to the accompanying drawings, in which :, .' '. " .
' :
''~ '~' ." .~.
;
~ - 7a -., 10~i8146 Fig. 1 shows the apparatus in the form of a schema~ic block diagram, and - Fig. 2 shows the variable voltage divider and the variable ~e-quency converter which form an important part of the apparatus, also in a schematic circuit diagram.
In Fig. 1, in addition to the block diagram of the control appara- -tus, a copying apparatus 10, in which the exposure is to be controlled, is also shown schematically. The copying apparatus comprises a copy-lng frame 11, on which light-sensitive material 12, for example a print-ing plate, and a transparent original 13 are arranged. A copying lamp 14 is used to illuminate the light-sensitive material through the copy 1 ;original. The copying lamp 14 is in electrical contact with a regulating unit 15. The luminous intensity produced by the copying lamp 14 in the exposure plane is measured by an electric photoreceiver (photocell) 16.
, These parts belong to the copying apparatus. The electric elements and structural groups described below are part of a control apparatus, and may be arranged in a housing which is spatially separate from the copy-ing apparatus.
The control arrangement is in electrical contact with the photo-cell 16 and with the regulating unit (switch) 15. The output of the photo-cell 16 is connected to an amplifier 17. The amplified output voltage may be measured by a vGltage indicator 17a. After the amplifier 17 in the direction of flow of the signal are a variable voltage divider 18, a voltage frequency converter (e.g. a voltage-controlled oscillator) 19 and a variable frequency reducer 20. Control elements 18a and 20a of the voltage divider and of the frequency divider are, as indicated by a broken line 21, ganged and are adjustable by a single control knob, not shown in the drawing. The constructions of the voltage divider 18 and 1(~6~3146 K -2 3 9 9 .
the frequency divider 20 are described in greater detail below with reference to Fig. 2.
!' The output of the adjustable frequency reducer 20, which is a signal composed of a series of pulses, is connected to an integrating comparator which is basically a pulse counter. The counter can be preset by way of a program store having a numerical setting member 23.
With the latter the counter can be set to values between 0 and 999 .:.
` pulses. When the output of the frequency divider 20, i.e., pulses corresponding to the luminous intensity measured by the photoreceiver 16 and in accordance with the switch positions of elements 18a and 20a, reaches the counter 22, it is reset by one step for each pulse, ; until it reaches the value 0. The value reached in the counter is shown by a digital indicator 24. When the zero value is reached, an appro-prlate signal passes to the control device 25, positioned downstream in the direction of flow of the signal, which is an order to the switch 15 to switch off the copying lamp.
Also connected to the control device is a starting means 26 whlch is actuated when an exposure operation is to begin~ In this case the switch 15 is closed so that the copying lamp 14 lights up. A portion of the light flux issuing from the copying lamp 14 is received by the photoreceiver 16 which delivers an electrical signal, corresponding to the luminous intensity, to the amplifier 17. This signal is indicated by ; the voltage indicator 17a. By this means the operating personnel can check whether the luminous intensity lies within those limits which are to be observed for the operation of the circuit arrangement in a desired characteristic curve range.
Referring now more especially to Fig. 2, the output from the am-plifier passes into the va~iable voltage divider 18, and from there, 4~ K-2399 possibly attenuated according to the position of the switch element 18a, into a voltage frequency converter which produces a pulse at a frequency corresponding to the voltage. The output of the voltage fr,equency con-verter 19 is connected to the variable frequency divider 20 which com-prises four trigger stages 27 to 30 and a switch element 20a. The switch element 20a has nine schematically illustrated contacts beside which the variation factors from the basic exposure time are indicated on Fig.
2. The pulses fed into the variable frequency divider pass into the input of the first trigger stage 27. Each of the trigger stages 27, 28, 29 and 30 is a frequency halver and hence the signal output from each is one pulse for every two input pulses. Accordingly there is a reduction by a factor of 2 at each of the trigger stages 27, 28, 29 and 30. The entire clrcuit arrangement is so designed that the basic exposure time is associated wLth a pulse frequency which appears at the output of the trigger stage 28, since a numerical unit of the number introduced with the numerical setting member 23 corresponds to each pulse at the output of the trigger stage 28. If the pulse frequency is taken at the output of the trigger stage 27 by the chosen position of the switching element 20a, the pulse frequency is twice as high as that at the output of the trigger stage 28; this results in a halving of the basic exposure time.
The pulse frequency at the input of the trigger stage 27 is four times as high as the pulse frequency at the output of the trigger stage 28. By setting the switching element 20a to the input of the trigger stage 27, a fourfold pulse frequency is therefore conveyed to the line coming off the change-over element 20a, which corresponds to a quarter of the basic exposure time.
Conversely, there occurs at the output of the trigger stage 29 a halving of the pulse frequency in comparison with the output of the ,. . . . . . . . .
1061~4tii K-2399 .-' trigger stage 28, so that by appropriate adjustment of the change-over element 20a a halved pulse frequency appears which results in a doubl-ing of the basic exposure time. By setting the change-over element to the contact marked 4, only every fourth pulse released from the output of the trigger stage 28 appears; the result is an exposure time that is four times as long.
With the adjustable frequency reducer 20 it is possible, there-fore, with low expenditure, to produce very accurate pulse freqllencies which are complete even-numbered multiples of a pulse frequency or of its reciprocal values. For the steps Iying inbetween, which are formed by the factor~ or its reciprocal value, the variable voltage divider 18 is used. This voltage divider is so designed that at a middle tapping 31 the input voltage is reduced by the factor \r2 1. The voltage output from this tapping corrésponds, according to the basic design of the appa-;; ! ratus, to a variation factor 1 of the basic exposure tlme, i.e. the normal basic exposure time. The undivided voltage, which is fed into the variable voltage divider which can be changed over, is thus greater by the factor ~ than the voltage at the tapping 31. This corresponds to an exposure time reduced by the factor ~r2 1. Conversely, when vol-tage is taken at a lower tapping 32, the voltage is reduced by the value \/~ 1 in comparison with the middle tapping 31. The result is an e~po-sure time longer by the factor ~
It may be seen from Fig. 2 that the change-over elements 18a and 20a are so coupled with one another that there is associated with the variation factors formed with even numbers the middle tapping 31 of the variable voltage divider, and associated with the variation factors formed with the factor ~ the lower tapping 32, and with the variation factors formed with the factor ~r2 finally the complete input signal at the variable voltage divider.
In the following, a table shows the connections which can be achieved with the arrangement between the positions of the ganged, switching elements 18a and 20a, and the variation factors achieved thereby, and an example of the resulting grey scale steps and the corre-sponding blackenings.
change-over -4 -3 -2 -1 0 +1 ~2 +3 +4 position variation factors 4 1 (2~r2) 1 2 1 ~2 1 1 ~/2 2 2~ 4 of the basic ex-posure time grey scale step 5 6 7 8 9 10 11 12 13 blackening 0 . 75 0 . 9 1. 05 1 . 2 1. 351. 5 1 . 65 1. 8 1. 95 Withthe described arrangement, exposure can be carried out, for example, in the following manner:
For a printing plate 12 which is to be exposed, it may be assum-~ ed that the manufacturer has indicated a basic exposure time of 100 units ; which are set with the numerical setting member 23 of the program store.
; If the basic exposure time is not altered, the grey scale step 9 would thus stand covered on the printing plate. With such a printing plate ;
there are to be produced from an original a proof plate, which is to be used in a flat bed proof press, and a machine plate which is to be intro-i:, " , 20 duced into a production machine. It has been ascertained internally that the proof plates produce optimum results at step 6 and machine plates at step 11 covered. To obtain these results with the arrangement, the ganged switching elements 18a and 20a need for the proof plate merely .i.
to be set to the switch position -3, and for the machine plate to the switch position +2. Without altering the setting member 23 the copy result will turn out as desired for both intended purposes of the printing . . .
plates .
, .
,. . :
: .. ,, ~ - :.' , . . ..
~l0~ 4~ K-2399 A further example of the application of the control device is in the exposure of different color films of an original. In this case, let it be assumed that at a basic exposure time of 85 pulses set in the program store 23, a color film RED is correctly exposed. For a color film YELLOW, on the other hand, double the exposure time is necessary according to the operating instructions. Without altering the setting member 23, this can be achieved simply by setting the switching ele-ments 18a and 20a to position +2. On the other hand a color film BLUE
requires an exposure time shorter by the factor ~r2 1, Without having to calculate in a complicated manner quotient of 85 pulses by ~/ 2, the optimum exposure time will occur by changing the elements 18a and 20a to the position -1.
It will be obvious to those skilled in the art that many modifi-cations may be made within the scope of the present invention without departing from the spirit thereof, and the invention lncludes all such modifications.
.~ , , .'~ ' i
Claims (8)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. An exposure control device, suitable for use to control the exposure of a light-sensitive material in a photographic copier apparatus for the pre-paration of a printing plate, which comprises program store means for prede-termining a basic exposure, input line means connected to a photocell for measuring the luminous intensity of a light source in the copier apparatus, comparator means having its input connected to an output of the program store means and connected by a transmission path means to the input line means, the output of the comparator means being connected to a control switch for the light source, and means for varying the transmission characteristics of the path in steps, adjacent pairs of which have transmissivities in the ratio .
2. A device as claimed in claim 1 wherein the transmission path means is variable in nine steps, giving values of 4, , 2, , 1, , 2-1 and 4-1.
3. A device as claimed in claim 1 wherein the program store means has an output variable in linear uniform steps.
4. A control device as claimed in claim 1 wherein the output of the pro-gram store means is connected to an input of the comparator means by a variable transmission path, the transmission characteristics being variable in steps, adjacent pairs of which have transmissivities in the ratio .
5. A control device as claimed in claim 1 wherein the transmission path comprises, in the direction followed by the signal from the input line, a variable voltage divider, having switching positions giving outputs in the ratios , 1:1; and , a voltage to frequency converter, and a vari-able frequency divider having switching positions giving frequencies in the ratios 4:1; 2:1; 1:1; 1:2 and 1:4.
6. A control device as claimed in claim 5 including coupled switching means for the voltage divider and the frequency divider.
7. A control device, suitable for use to control the exposure of a light-sensitive material in a copying apparatus for the preparation of a printing plate, which comprises program store means for predetermining a basic exposure, input line means connected to a photocell for measuring the luminous intensity of a light source in the copying apparatus, comparator means having its input connected to an output of the program store means by a transmission path means and connected to the input line means, the output of the comparator means being connected to a control switch for the light source controlling the exposure of the light-sensitive material imagewise exposed by the light source and the transmission characteristics of the path being variable in steps by switching means provided in the transmission path means adjacent steps of which switching means have transmissivities in the ratio .
8. A device as claimed in claim 7 wherein the transmission path means is variable in nine steps, giving values of 4, 2,, 1, , 2-1, and 4-1.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE2528659A DE2528659C3 (en) | 1975-06-27 | 1975-06-27 | Arrangement for controlling the amount of light for the exposure of photosensitive material in copiers for printing form preparation |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1068146A true CA1068146A (en) | 1979-12-18 |
Family
ID=5950056
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA255,767A Expired CA1068146A (en) | 1975-06-27 | 1976-06-25 | Exposure control device for photographic copier |
Country Status (12)
| Country | Link |
|---|---|
| US (1) | US4143968A (en) |
| AT (1) | AT349887B (en) |
| BE (1) | BE843455A (en) |
| CA (1) | CA1068146A (en) |
| DE (1) | DE2528659C3 (en) |
| ES (1) | ES221915Y (en) |
| FR (1) | FR2315830A7 (en) |
| GB (1) | GB1552674A (en) |
| IT (1) | IT1061583B (en) |
| NL (1) | NL7606902A (en) |
| SE (1) | SE427700B (en) |
| ZA (1) | ZA763801B (en) |
Families Citing this family (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4526463A (en) * | 1982-07-30 | 1985-07-02 | CH2 M Hill, Inc. | Apparatus for exposing photosensitive media |
| US4644165A (en) * | 1983-02-22 | 1987-02-17 | Colight, Inc. | Integrating photometer |
| FR2584504B1 (en) * | 1985-07-04 | 1989-03-17 | Thomson Cgr | METHOD FOR AUTOMATICALLY DETERMINING THE EXPOSURE OF A RADIOGRAPHIC FILM, AND AUTOMATIC EXPOSURE DEVICE FOR RADIODIAGNOSTIC INSTALLATION IMPLEMENTING SAID METHOD |
| US4707124A (en) * | 1985-09-03 | 1987-11-17 | CH2 M Hill, Inc. | Apparatus for exposing photosensitive media |
| US5214274A (en) * | 1992-07-24 | 1993-05-25 | President And Fellows Of Harvard College | Image sensor array with threshold voltage detectors and charged storage capacitors |
| DE19746331A1 (en) * | 1997-10-21 | 1999-04-29 | Gerhard Theimer | Method for testing exposure value of photographic printer |
| US7691550B2 (en) * | 2007-06-20 | 2010-04-06 | E.I. Du Pont De Nemours And Company | Method for making a relief printing form |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5243365B2 (en) * | 1971-09-22 | 1977-10-29 | ||
| US3795444A (en) * | 1972-10-05 | 1974-03-05 | Eastman Kodak Co | Exposure control apparatus |
-
1975
- 1975-06-27 DE DE2528659A patent/DE2528659C3/en not_active Expired
-
1976
- 1976-06-23 US US05/699,086 patent/US4143968A/en not_active Expired - Lifetime
- 1976-06-23 SE SE7607235A patent/SE427700B/en unknown
- 1976-06-24 FR FR7619184A patent/FR2315830A7/en not_active Expired
- 1976-06-24 NL NL7606902A patent/NL7606902A/en not_active Application Discontinuation
- 1976-06-25 IT IT50135/76A patent/IT1061583B/en active
- 1976-06-25 BE BE168357A patent/BE843455A/en unknown
- 1976-06-25 CA CA255,767A patent/CA1068146A/en not_active Expired
- 1976-06-25 ES ES1976221915U patent/ES221915Y/en not_active Expired
- 1976-06-25 AT AT464476A patent/AT349887B/en not_active IP Right Cessation
- 1976-06-25 GB GB26565/76A patent/GB1552674A/en not_active Expired
- 1976-06-25 ZA ZA763801A patent/ZA763801B/en unknown
Also Published As
| Publication number | Publication date |
|---|---|
| US4143968A (en) | 1979-03-13 |
| AT349887B (en) | 1979-04-25 |
| ZA763801B (en) | 1977-05-25 |
| GB1552674A (en) | 1979-09-19 |
| ATA464476A (en) | 1978-09-15 |
| FR2315830A7 (en) | 1977-01-21 |
| DE2528659C3 (en) | 1978-11-30 |
| NL7606902A (en) | 1976-12-29 |
| SE427700B (en) | 1983-04-25 |
| DE2528659B2 (en) | 1978-02-02 |
| IT1061583B (en) | 1983-04-30 |
| DE2528659A1 (en) | 1976-12-30 |
| SE7607235L (en) | 1976-12-28 |
| ES221915U (en) | 1977-03-01 |
| BE843455A (en) | 1976-12-27 |
| ES221915Y (en) | 1977-06-16 |
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