Patent GB-905244-A (GB)
Title: Cinematographic method and apparatus
Inventor: LAND EDWIN HERBERT
IPC: G03B15/08
Filed: 1960-07-26
Abstract: 905,244. Kinematographic methods. INTERNATIONAL POLAROID CORPORATION. July 26, 1960, No. 25985/60. Classes 97 (1) and 98 (2). In the method of recording a short kinematographic sequence of images on a single frame (see Specification 421,120), whereby the image field is divided, by means of a juxtaposed lenticular screen, into discrete areas each of which contains a composite image of a corresponding portion of the object field, throughout the time interval, in the form of a series of elemental images arranged in a time-sequential pattern within the lenticule area, the spatial displacements of these elemental images are effected by an aperture which is imaged by each lenticule on a small portion of its associated area on the photo-sensitive surface and which is moved, relatively to the lenticular screen, in a continuous, or broken, generally inwardly spiralling path during exposure of the sequence. The elemental images underlying each lenticule are thus arranged in a spiral pattern, the areas of the photo-sensitive material scanned by the aperture during successive exposures being kept substantially of the same shape by varying the dimensions ot the aperture as its linear velocity changes, or by varying its angular velocity to increase with decreasing radial co-ordinate of the aperture, or both by varying the aperture dimensions and the angular velocity. As shown in Fig. 1, a lenticulated screen 22 supports a photo-sensitive film 28 and a transparent image-receiving layer 28 between which migratory diffusion transfer occurs under the action of developing liquid in a containing sac 32 which may be squeezed out while in situ in the camera with the help of a backing-plate 30. Each of the lenticulations 24 forms on the underlying region of the film 28 an image of an aperture defined by the intersection (see Figs. 3 and 4) of slot 64 on a disc 50 with one of the concentric arcuate slots 56, 58, 60 and 62 in a second disc 48. The totality of all such elemental images is the image formed by the objective lens, and as discs 50 and 48 rotate relatively to each other, all of the image elements will be displaced by the lens action of the lenticulations and will follow a locus corresponding to that of the exposed aperture area. A third slotted disc rotating coaxially with discs 48 and 50 acts as a shutter, and the film under each lenticulation will thus carry a generally spirally-arranged time-sequence of separate images of its corresponding portion of the object field. In order that all the elemental images have substantially the same area, the arcuate slots in disc 48 have widths varying inversely as their radial distance to compensate the wedge-shaped formation of slot 64. Instead of a series of discrete stepped stops, a single spiral slot may be used having a similar radial variation of width. Alternatively, as in Fig. 7, if slot 64 is of the same width in different zonal regions, the slots in disc 48 may have equal widths and, by means of a suitably geared drive, the angular velocity of disc 48 is varied so as to increase as the effective aperture moves towards the centre so that overlap of the elemental images will be avoided. For colour pictures, red, green and blue filters may be arranged in concentric strips to fill each slot in disc 48 (Fig. 8), or these strips may be located in the single slot of disc 50 (Fig. 9). An alternative arrangement to a system of apertured discs is to have a fixed aperture 90 (Fig. 12) and to produce effective radial displacement of it by varying the separation between prisms 92 and 93, rotation of these prisms about the optical axis of lens 91 causing circular movement of the emergent light beam. In the above methods, only a part of the objective lens aperture is used and when, by a similar procedure, the film is projected, only that part of the lens which is being used instantaneously is illuminated by the condenser system, the latter being arranged for movement in synchronism with the scanning motion of the aperture. To avoid the wastage of aperture in the use of a large lens, Fig. 13 shows a small aperture lens 120 which comprises the scanning aperture and is mounted for radial movement in a slot in a disc 122 rotatable by gear 148, rotation of disc 122 producing, via gear 166 and the hypoid gears 164 on shafts 156, radial movement of the lens. These movements may be simultaneous or, alternate and intermittent, the shutter opening to expose the film while the lens is stationary. To compensate for the general image shift caused by the variation in position of the objective lens 120, a second lens is provided moving oppositely to the former, the overlap relationship of the two lenses being such as to maintain the image field stationary. A second mechanism similar to that of Fig. 13 may be provided for this purpose. Since the relative counter-rotation of the two lenses would bring them into overlapping relationship only once per revolution, in order to produce a higher frequency of overlap and hence also shutter exposure several auxiliary lenses may be provided. If there is a fair amount of tolerance on the resolution of the image, radial motion of the auxiliary lenses may be dispensed with. A prism arrangement similar to that of Fig. 12 may also be used for the compensation of image shift. If the objective lens is rotated with uniform angular velocity, provision for varying its aperture is included in the drive mechanism. Otherwise, if its aperture is constant, the angular velocity is varied. Coloured filters may be arranged in the exposure aperture for colour films. In projection, the lenticules are arranged to face the condensing lens, and a second lenticular screen is placed in close proximity to the first screen, between it and the projection lens, with its lenticules towards the projection lens and in perfect registration with the lenticules of the first screen, in order to efficiently collect light scattered in widely divergent directions by the first lenticular screen. Specification 730,722 also is referred to.