Patent GB-1393921-A (GB)
Title: Photographic printer control apparatus and method
IPC: G03B27/72
Filed: 1972-04-13
Abstract: 1393921 Photographic printer control EASTMAN KODAK CO 13 April 1972 [13 April 1971] 17021/72 HeadingG2A As a strip of originals is fed forward to a printing station each original is detected and classified as printable or unprintable, a corresponding signal being fed to the printer; an "unprintable" signal can be over-ridden as required to produce a "print" signal. As shown, the film strip 10, carrying a number of frame images 32, comprises a number of separate strips joined together by splices 46. The strip 10 is passed in the direction 12, below two light sources 18, 16 towards the printing station 14. Below the light sources is a compartmented housing 20 divided into six chambers 22, 24, 26, 28, 30 and 48. The first five of these have a combined dimension equivalent to one frame area 32. Chambers 22, 24, 26, 28 receive light from source 16 passing through the peripheral areas 22a, 24a, 26a, 28a of frame 32, and chamber 30 receives light passing through the central area 30a. Each chamber contains a photo-sensitive device 22b, 24b, 26b, 28b and 30b. Chamber 48, corresponding in shape to a splice 46, contains a photo-sensitive device 48b which receives light from source 18, unless blocked by a splice. A second splice-detecting device 48c is located within chamber 22. Thus as the film strip advances, the splice 46 passes first under source 18 and then source 16, producing two separate signals. The frame area 32 is uniformly illuminated by light source 16, and by dividing up housing 20 into separate chambers, each with its own photo-sensitive device, the transmission of each of the five separate sections of frame area 32 can be measured separately. Thus subjectfailure due to front or back lighting can be readily ascertained by comparing the transmittances of the separate sections of the frame area. The signals from the various photo-sensitive devices are fed in parallel to the anodes of gating diodes 64, 66 and the diodes are connected via transistors 68, 70 to respective amplifiers 80, 100. If a low amount of light is transmitted by the frame image 32 to all the five photo-sensitive devices in housing 20, the output at terminal 90 from amplifier 80 is positive, indicating that the image frame or negative 32 is so dense that it is unprintable. A blank or underexposed negative causes the production of a positive output signal at output terminal 110 from amplifier 100. These two signals are transmitted to a common point 94. A printable negative causes neither output signal. If any one of the five photo-sensitive devices generates a signal indicating some discernable subject matter on the negative frame, neither output signal is generated. The provision of five photo-sensitive devices operating independently in parallel ensures that printable subject failure negatives can be distinguished from unprintable negatives. If a negative is detected as unprintable, any signal received from a splice is cancelled so that it does not produce a "printable" signal. Even if all the negatives are detected as "unprintable", a print of one frame between two consecutive splices must be made, in order to keep each customer's order separate, and this over-riding "print" signal is caused when a second splice is detected. If the negative is determined as unprintable, then the densities of the central and peripheral areas are compared to determine whether there is an unequal distribution indicating subject failure. If so, exposure correction factors are applied.