US3576370A - Exposure time control system for photographic apparatus - Google Patents

Exposure time control system for photographic apparatus Download PDF

Info

Publication number
US3576370A
US3576370A US769868A US3576370DA US3576370A US 3576370 A US3576370 A US 3576370A US 769868 A US769868 A US 769868A US 3576370D A US3576370D A US 3576370DA US 3576370 A US3576370 A US 3576370A
Authority
US
United States
Prior art keywords
color
voltage
colors
set forth
exposure control
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 - Lifetime
Application number
US769868A
Other languages
English (en)
Inventor
Gerhard Kuhn
Wolfgang Zahn
Walter Knapp
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Agfa Gevaert AG
Original Assignee
Agfa Gevaert AG
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Priority claimed from DE19671597078 external-priority patent/DE1597078A1/de
Application filed by Agfa Gevaert AG filed Critical Agfa Gevaert AG
Application granted granted Critical
Publication of US3576370A publication Critical patent/US3576370A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

Classifications

    • 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
    • G03B27/73—Controlling exposure by variation of spectral composition, e.g. multicolor printers
    • G03B27/735—Controlling exposure by variation of spectral composition, e.g. multicolor printers in dependence upon automatic analysis of the original

Definitions

  • Each relay has a first set of contacts for terminating the illumination in the corresponding color and a second set of contacts for shorting out part of a resistance connected in series between the supply voltage terminal and a transformer supplying voltage to the secondary electron multiplier corresponding to the other colors. This increases the sensitivity of the other electron multipliers, increasing the charging rate of the capacitor, and thus decreasing the exposure time in the other colors.
  • This invention relates to a system for controlling the exposure time for different colors in photographic color copying equipment. In particular, it relates to control of exposure time in such a manner that undercorrection may be effected. In particular, it relates to such exposure control systems wherein photoelectric transducing means are used to evaluate the quantity of light falling on photosensitive material in each of three colors and wherein the illumination in each color is individually terminated when the corresponding quantity of light has reached a predetermined value.
  • the quantity of light falling on the photosensitive material in each color is so selected that the amount of light falling on the material for an even distribution over the surface of the material would cause a neutral gray to result after development.
  • This so-called neutral gray compensation has the advantage that in the case of pictures lacking a very dominant color, a correct reproduction of the photographic scene results independent of possible color deviations in either the negative material or the photosensitive material. Furthermore, a color distribution whose sum results in a substantially neutral gray is particularly pleasing to the eye. To a certain extent a color copy may be considered adequate even if one color predominates slightly in the photograph scene, even though this color is not correctly reproduced. Only when a strong color dominant exists in the scene to be reproduced, that is when large surface areas of the scenehave the same color, do unsatisfactory color copies result from neutral gray compensation,
  • This invention comprises an exposure control arrangement having illuminating means for illuminating photosensitive material through an original in each of a predetermined plurality of colors, the illumination in a given color starting at an illumination starting time. It further comprises a plurality of measuring means corresponding in number to said plurality of colors, each for furnishing a color measurement signal corresponding to the total amount of light received by said photosensitive material in a corresponding color since the corresponding illumination starting time. Terminating means are 7 supplied for individually tenninating the exposure in said colors when the corresponding color measurement signal has reached a predetermined value. Further, exposure time changing means are provided for changing the exposure time for at least one color still being illuminated upon termination of the illumination in at least one other color.
  • reference numeral 1 denotes a supply voltage arrangement for secondary electron multipliers which serves to limit the usual sinusoidal supply voltage in both a positive and negative direction so that a substantially rectangular wave form is generated.
  • the primary windings of three transformers which serve as a means for furnishing an applied voltage are connected to the voltage supply means 1 via a number of adjustment, compensation and calibration resistors. These primary windings arc the primary windings of transformers 2, 3, and 4, respectively.
  • the corresponding secondary windings are each connected to photoelectric transducing means, here electron multipliers 5, 6 and 7.
  • each secondary winding is connected between a cathode and one dynode of the corresponding secondary electron multipliers, while the anodes of all secondary electron multipliers are connected together to a source of positive potential, in this case stage 27.
  • resistance means Directly connected to the means for furnishing a supply voltage, namely stage I, are resistance means denoted by reference numerals 8, 9 and 10.
  • resistance means comprise potentiometers. Potentiometers 8, 9 and 10 are each individually connected in parallel with normally open contacts 11a, 12a, 13a of relays ll, 12 and 13 to be described below.
  • a voltage divider Connected in parallel to supply voltage source 1 is a voltage divider comprising a potentiometer l4 and a fixed resistor 15.
  • the wiper arm of potentiometer 14 is connected to the series combination of three variable resistors l6, l7 and 18. These serve for density compensation.
  • resistors l6, l7 and 18 are coupled to further adjustable resistors 20 in each of the color channels in such a manner that a change in one color channel does not result in a change in total density of the copy.
  • the operation of these resistors is disclosed in US. Pat. No. 3,355,984.
  • Three series resistance combinations each comprising a fixed resistor 21 and a potentiometer 19 as well as resistor 20 are connected between the other terminal of the series combination of resistors l6, l7 and 18 and the other supply voltage line.
  • the primary of each transformer 2, 3, and 4 is connected to the variable arms of potentiometers 19 further adjustable resistor 20 in said series combination.
  • a resistance 22 is connected in series to each primary winding.
  • the circuit associated with secondary electron multiplier 5 will now be discussed.
  • the circuits for secondary electron multipliers 6 and 7 are analogous.
  • the secondary electron multipliers with their associated circuits each comprise a color channel in which the light passing through the original and illuminating the photosensitive material in each of three prima ry colors is evaluated.
  • the light for the secondary electron multipliers can be derived in a conventional fashion through a mirror arrangement in the path of the light and color separation by means of filters or, alternatively by means of dicroic mirrors. In either case, the light impinging on each secondary electron multiplier corresponds to light in one of three primary colors.
  • a capacitor 23 is connected to the dynode 9 of the secondary electron multiplier 5.
  • the other terminal of the capacitor is connected to the secondary winding of transformer 2. This part of the secondary winding is also connected to ground via line 24.
  • a normally open relay contact 33 is controlled by a relay which is not shown. These contacts serve to discharge the capacitor at the end of a copying operation.
  • the common point of dynode 9 and capacitor 23 is connected to the gate of an amplifier tube 25 which, in
  • amplifier tube 26 present a high input impedance to the voltage on capacitor 23 and further, in conjunction with relay 11 serves as terminating means for this channel.
  • the cathode of amplifier tube 25 is connected to means for furnishing reference voltage, namely stage 27 via resistors 29, 30, and 31.
  • Stage 27 furnishes a reference voltage in accordance with the teachings of the German Pat. No. l,046,497, in which the exposure time and Schwarzschild effect of the photosensitive material are taken into consideration.
  • Amplifier tube 26 allows current to flow through relay 11 via a direct current supply source 28. This relay in turn activates a normally open contact 11a which when closed short circuits the above-mentioned resistance 8.
  • these contacts may interrupt the current in a lamp or alternatively may serve to activate an electromagnet which pulls a subtractive filter into the path of the illumination, thus causing the illumination in the corresponding color to be terminated.
  • the increase in voltage of the capacitors is a function not only of the light intensity at the photo cathode of the secondary electron multiplier, but also depends on the voltage in the circuit of the primary winding of each of the transformers 2, 3, and 4. Potentiometers 8, 9 and effect all three of these voltages simultaneously as do potentiometers 16, 17 and 18.
  • the operation of these potentiometers or variable resistors is as follows: The wiper arms of the potentiometers 16, 17 and 18 are so coupled with the wiper arms of variable resistors 20 which effect each applied voltage separately in such a manner that a change in the sensitivity in the color channel comprising secondary electron multiplier 5 causes no change in the total density of the copy since the sensitivity of the other two channels is changed in the opposite direction. Potentiometers 19 and 22 serve for individual adjustment of each color channel, for example potentiometer 19 may be used for calibration of the equipment, while potentiometer 22 may be adjusted to compensate for the particular characteristics of the corresponding secondary electron multiplier.
  • the voltage on capacitor 23 thus increases in correspondence to the voltage applied to the photosensitive transducing means, that is the voltage across the secondary winding of each transfer which in turn is determined by the voltage on the primary winding of each transformer. It is further, of course, a function of the illumination reaching the corresponding secondary electron multiplier 5, 6 and 7.
  • Amplifier tubes 25 and 26 serves to compare this capacitor voltage to a reference voltage supplied by stage 27. This reference voltage has a value which takes into consideration the Schwarzschild effect and other characteristics of photosensitive material.
  • this may be accomplished by inserting a subtractive filter into the path of the illumination.
  • it might be accomplished by opening normally closed contacts in a lamp. The latter method is appropriate when the photographic apparatus has a different lamp serving as a source of illumination for each color.
  • Energization of the relay also causes a closing of normally open contact pair 11a which short circuits potentiometer 8.
  • the resistance in the primary circuit of transformers 3 and 4 is decreased causing the voltage applied to secondary electron multipliers 6 and 7 to be increased, which in turn causes an increase in the rate of change of voltage on the corresponding capacitors.
  • resistance means 8, 9 and 10 shown in the FIG. comprise potentiometers, the possibility exists to effect a separate undercorrection for each color.
  • other means are available for such a separate undercorrection and it is therefore desirable to mechanically intercouple all three variable arms on a single shaft. Then a single adjustment may be made for the desired degree of undercor' rection.
  • an exposure control arrangement comprising in combination, illuminating means for illuminating said photosensitive material through said original in each of a predetermined plurality of colors, the illumination in a color starting at a corresponding illumination starting time; a plurality of measuring means corresponding in number to said plurality of colors, each for furnishing, subsequent to the corresponding illumination starting time, a color measurement signal corresponding to the total amount of light having illuminated said photosensitive material in the corresponding color since the corresponding illumination starting time; terminating means for individually terminating the exposure in each of said colors when the corresponding color measurement signal has reached a predetermined value; and exposure time changing means for changing the exposure time for at least one color still being illuminated upon termination of the illumination in at least one other color.
  • said exposure time changing means comprise means for shortening the exposure time for at least one color still being illuminated upon termination of the illumination in at least one other color.
  • measuring means comprise photoelectric transducing means for generating three electrical signals, each varying as a function of the amount of light illuminating said photosensitive material in a corresponding one of said colors; and electrical integrator means for integrating each of said electrical signals thus furnishing said color measurement signals.
  • said photoelectric transducing means comprise a plurality of photoelectric transducing means, one for each of said colors; wherein said charging currents also vary as a function of voltage applied to the corresponding photoelectric transducing means; and wherein said exposure time changing means comprise means for changing said applied voltage of at least one other of said photoelectric transducing means upon termination of illumination in any one color.
  • said terminating means comprise a plurality of relay means, one for each of said colors; and energizing means, one for each of said relay means, for energizing the corresponding relay means when the voltage on the corresponding capacitor has reached a predetermined value.
  • An exposure control arrangement as set forth in claim 7 further comprising means for furnishing a reference voltage; and wherein said energizing means comprise electronic switching means connected to said means for furnishing a reference voltage, to the corresponding capacitor, and to the corresponding relay means in such a manner that said relay means are energized when the corresponding capacitor voltage has reached a predetermined relationship to said reference voltage.
  • An exposure control system as set forth in claim 8 further comprising voltage supply means to furnish a supply voltage; and resistance means, sen'es connected between said voltage supply means and said photoelectric transducing means; and wherein said means for changing said applied voltage comprise means for short circuiting a predetermined corresponding part of said resistance means upon termination of the illumination in each of said color.
  • said means for short circuiting a predetermined part of said resistance means comprise three pairs of normally opened relay contacts, one pair associated with each of said relay means.
  • each of said predetermined parts of said resistance means comprises a fixed resistor; further comprising additional resistors for each of said parts; and means for selecting difi'erent ones of said additional resistors to constitute said of undercorrection.

Landscapes

  • Physics & Mathematics (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • General Physics & Mathematics (AREA)
  • Control Of Exposure In Printing And Copying (AREA)
US769868A 1967-10-27 1968-10-23 Exposure time control system for photographic apparatus Expired - Lifetime US3576370A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
DE19671597078 DE1597078A1 (de) 1967-10-27 1967-10-27 Fotografisches Farbkopiergeraet

Publications (1)

Publication Number Publication Date
US3576370A true US3576370A (en) 1971-04-27

Family

ID=5680547

Family Applications (1)

Application Number Title Priority Date Filing Date
US769868A Expired - Lifetime US3576370A (en) 1967-10-27 1968-10-23 Exposure time control system for photographic apparatus

Country Status (3)

Country Link
US (1) US3576370A (enrdf_load_stackoverflow)
FR (1) FR1585580A (enrdf_load_stackoverflow)
GB (1) GB1244495A (enrdf_load_stackoverflow)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3752577A (en) * 1970-12-16 1973-08-14 Debrie Andre Ets Light-correction system for printers of colour cinematographic films
US3873200A (en) * 1973-09-06 1975-03-25 Crete Charles A Photographic color enlarging system
US4792829A (en) * 1986-04-03 1988-12-20 Firmani Alexander D Light-exposure control unit

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4848762A (en) * 1988-03-16 1989-07-18 The Mead Corporation Sheet feeder with articulated feed pads

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3100419A (en) * 1959-01-30 1963-08-13 Pako Corp Photographic printer
US3293033A (en) * 1960-01-18 1966-12-20 Pako Corp Method for controlling explosure in a photographic color printer

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3100419A (en) * 1959-01-30 1963-08-13 Pako Corp Photographic printer
US3293033A (en) * 1960-01-18 1966-12-20 Pako Corp Method for controlling explosure in a photographic color printer

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3752577A (en) * 1970-12-16 1973-08-14 Debrie Andre Ets Light-correction system for printers of colour cinematographic films
US3873200A (en) * 1973-09-06 1975-03-25 Crete Charles A Photographic color enlarging system
US4792829A (en) * 1986-04-03 1988-12-20 Firmani Alexander D Light-exposure control unit

Also Published As

Publication number Publication date
FR1585580A (enrdf_load_stackoverflow) 1970-01-23
GB1244495A (en) 1971-09-02

Similar Documents

Publication Publication Date Title
US4101217A (en) Automatic color printing apparatus
US3229569A (en) Process and apparatus for producing photographic color reproductions
US4192605A (en) Method and apparatus for making color prints
US3653759A (en) Automatic control of color correction of photographic printers
US3521952A (en) Light exposure control unit
US3697174A (en) Automatic color subject failure correction with illuminant discrimination for photographic printers
US4236817A (en) Photographic copying machine with exchangeable format masks
US3813158A (en) Color printer using light flash tubes
US3619055A (en) Exposure control device
US2853921A (en) Apparatus for photographic printing
US3576370A (en) Exposure time control system for photographic apparatus
US3743405A (en) Automatic exposure control in electrophotography
US2952780A (en) Photographic printing apparatus
US3020801A (en) Device for the optical copying of photographic negatives
US3076378A (en) Photographic printing system and method
US3575508A (en) Exposure time control arrangement
US2258994A (en) Photographic printing apparatus
US3924121A (en) Process and apparatus for undercompensating photographic color printing
US3523728A (en) Color printing apparatus
US3873199A (en) Method and arrangement for adjustment of photographic copying apparatus
US2847903A (en) Multicontrast printer control units
US3650624A (en) Photographic printer with automatic exposure control
US4110039A (en) Microfilm enlarging apparatus
US4792829A (en) Light-exposure control unit
US3069971A (en) Exposure control apparatus for making color prints