Patent GB-1268694-A (GB)
Title: Improvements relating to photographic cameras
Inventor: LAND EDWIN HERBERT
IPC: G03B17/52
Filed: 1969-07-30
Abstract: 1,268,694. Self-processing cameras. POLAROID CORP. July 30, 1969, No.38335/69. Heading G2A. In a self-processing camera for exposing and processing a film unit including a rupturable container of processing liquid, the film unit is passed between rollers in a first direction during the exposure stage, and then passed back again in the reverse direction during the processing stage. The unit is of the type Fig. 8 (not shown) having an opaque support carrying a photo-sensitive sheet (120) and a transparent image-receiving transfer sheet (122), with a rupturable container (126) of processing liquid. The camera is of the type disclosed in Specification 1, 170, 855, in which the light path is folded by mirrors so as to produce a very compact construction. Light entering the objective lens system 26, 28 is reflected by a 45 degree prism 44 and mirrors 48, 50, 52 to a slit-aperture 42 in a plate 40 behind which the film unit passes. Plate 40 forms with another plate 38 a guiding passage for the film unit. The units are contained in a pack 138 which is housed adjacent one end wall 22 of the camera. The rollers 160, 162 and the optical system are at the other end of the camera, and between them lie the motor 170 and batteries 172. A film unit is moved out of the pack towards the rollers by a lever system whose end 152 is engaged by a member 210 coupled to a cam 206 and button 208. Thus moving button 208 to the right feeds a unit forward to engage between the rollers. At the same time the cam engages a stud 204 on a rotary switch 196 which rotates so as to energise the motor and drive the rollers. The film unit is now driven by the rollers to pass between guides 38, 40 and past slit 42 where the exposure is made. A mirror 32 on a shaft 34 is mounted at 45 degrees to the optical axis just behind the exposure window (30), Fig. 1 (not shown). The image formed by the objective lens is moved relative to the slit 42, so as to remain stationary with respect to the moving film, by pivoting mirror 32 on shaft 34 in synchronism with the film movement, the mirror being driven from roller 162. Since the section of the camera housing to the right of the rollers is shorter than the film unit, when the unit has been advanced completely it extends beyond the housing, projecting from the camera through a slot 184. In order to contain the unit in this extended position, a thin flat compartment 186 is pivoted to the end wall 20. In its inoperative position it is pivoted upwards to lie along the top of the camera housing, as shown in Fig. 6. In use it is pivoted downwards into the position shown in broken lines, so that the film unit passes out through slot 184 into the compartment 186 which now acts as a temporary extension of the camera housing. After the film unit has been moved into the exposure position, a lost-motion device is set in operation which eventually acts on the rotary switch 196 to reverse the motor and so draw the film unit back in the opposite direction. Roller 162 is mounted on arms 164 which pivot on a shaft 166 and are biased by a spring 168 in such a way that when the film unit passes between the rollers into the exposure position, the pressure between the rollers is not sufficient to rupture the container 126. During the reverse movement, however, the pressure becomes sufficient to rupture the container, the liberated liquid then being spread between the film sheets in the usual way. The exposure is controlled by means of a variable stop between the lens elements. This is formed by a flexible strip 54 having superimposed end sections 56, 58, with respective rectangular or diamond-shaped apertures 60, 62 therein. When these apertures are aligned on the optical axis, the stop is fully open. The middle part 64 of strip 54 passes round a shaft 66 and is secured thereto. Thus rotation of shaft 66, by means of a knob 68, causes end sections 56, 58 to move in opposite directions, with corresponding movement of apertures 60, 62 so that the size of the stop is varied. The camera includes a viewfinder 86 and a comparison photo-meter 73. The photo-meter comprises a window 80 and a light-integrating element 82, light from which is reflected by a mirror 84 to a light-transmitting target 74 which is also illuminated from its other side by a lamp 76, whose intensity is controlled by the same knob 68 which controls the aperture stop. A pair of mirrors 83, 81 enable the target 74 to be seen in the viewfinder. The viewfinder has a front lens 88 having silvered portions 96, and a rear lens 90 with a frame marking 98, so that an observer looking through the viewing window 94 can see the frame 98 by reflection. Light entering an additional window (100), Fig. 1 (not shown) is reflected to form a circular reflecting surface 104 in the viewfinder, so that the scene is viewed by light transmitted along the paths separated by the spacing between the window (100) and the viewfinder. A pair of optical wedge elements 106 are provided behind the window, for focusing, which is carried out by rotating the wedge and comparing what is seen in reflecting surface 104 with what is seen directly through the viewfinder. Wedge 106 is rotated by means of a linkage with a sliding plate 110 which is operated by a knob 112, and which also moves the front lens element 26 axially. As the film unit moves past the exposure slot 42, and between the viewfinder elements 90, 94 into the compartment 186, it would be subjected to further light transmitted through the viewfinder. (It would not be affected by light passing through window 94 since the photo-sensitive layer is on an opaque backing.) In order to prevent any further exposure from light entering through the viewfinder, an opaque flexible curtain 188 is provided, coiled up on a shaft 190. As the film unit leaves the guides 38, 40, its forward end engages with a member 192 attached to the end of curtain 188. As the unit moves across into compartment 186 the curtain is unrolled and shields the unit against light entering through the viewfinder. When the unit moves back in the opposite direction, the curtain is rolled up again by a spring. In order to prevent further exposure as the film unit re-passes exposure slot 42 in the reverse direction, a capping blade 232, pivotally mounted between the lens elements 26, 28, is linked by a lost-motion device with the movement of the film unit, so that it pivots into the light path through the lens system, blocking off the said path during the return motion of the film unit.