Patent GB-1206387-A (GB)
Title: Improvements relating to photographic cameras
Inventor: LAND EDWIN HERBERT
IPC: G03B17/52
Filed: 1969-05-05
Abstract: 1,206,387. Panoramic cameras. POLAROID CORP. May 5, 1969, No.22860/69. Heading G2A. In a camera in which the image and the film are both moved past a long narrow aperture so that they remain stationary with respect to each other, the light-transmittance of the aperture is varied inversely with the light intensity falling on it, said variation being controlled by photo-reponsive means sensing said light intensity. The camera shown is of the panoramic or scanning type, light entering the objective lens 28 being reflected from a pivoted mirror 30 and through a pentaprism 32 to fall on a photo-sensitive sheet passing behind a slot-like aperture 38 in a plate 36. The sheets are of the self-processing (Registered Trade Mark) "Polaroid" type, housed in a container 56, and moved one by one out through a slot 62 into the exposure position by spring-loaded sliders 64. The sliders are pushed to the right, Fig.1, against springs 66, by projections 90 on endless moving belts 82, to engage and transport the photo-sensitive sheets. The belts are driven by a motor-powered roller 74, which roller also co-operates with a smaller roller 76 to rupture a container holding processing liquid, as the photographic sheets pass beyond the exposure aperture and round roller 74. They are then guided into a processing chamber 27, from where they are removed by opening a door 26 in the camera wall. The same belts 82 also transmit movement to the mirror by means of a gear and cam arrangement, causing it to execute its scanning movement in synchronization with the film movement. The light-transmittance of the aperture 38 is controlled by means of a flexible elastic curtain 108 mounted on plate 36, and whose front edge 110 extends partly over the aperture 38. A spring 118 attached to the curtain normally retains it in a deformed state, so that the amount of aperture 38 uncovered is at a maximum. A tape 122 connects the curtain to a coupling disc 116, and another tape 120, also attached to disc 116, extends in the opposite direction to spring 118. Disc 116 is a magnetic coupling mounted loosely on a constantly rotating (anti-clockwise) shaft 114, but can be energized so that it is coupled to the shaft in such a manner that the torque produced is proportional to the energizing current. Thus as the current, and hence the torque, increases, against spring 118, the curtain 108 is increasingly released from its distorted position and aperture 38 becomes increasingly smaller. Part of the light from the objective 28 which enters the pentaprism 32 is not reflected from surface 126, but passes straight through to fall on a photo-sensitive cell 124, the signal being amplified and used to control the coupling disc 116, so that the width of the aperture 38 is varied inversely with the intensity of the incident light. There are in fact three magnetic coupling discs 116, each with its corresponding spring 118 and photo-cell 124, so that the width of the aperture can be independently set to a different value, if required, at different zones along its length. Fig. 5 (not shown) illustrates another method of varying the aperture width. In this case the aperture is formed by the space between two membranes (140) of conductive material, which are deflected towards or away from each other (so varying the aperture width) by acquiring appropriate electrostatic charges.