Patent GB-472562-A (GB)
Title: Improvements in or relating to stereoscopic television cinematograph and like systems
Filed: 1936-07-02
Abstract: 472,562. Television. EISLER, P., and PEVNY, F. July 2, 1936, No. 18431. [A Specification was laid open to inspection under Sect. 91 of the Acts, Jan. 4, 1937.] [Classes 39 (i) and 40 (iii)] [Also in Group XX] Relates to a stereoscopic television system in which the right and left (or sectional) pictures are interlineated and viewed through a line screen, so that the left and right eyes see only the strips corresponding to the left and right pictures respectively. According to the invention, the sectional pictures are scanned in adjacent juxtaposed lines and at the receiver, the composite picture is produced by a scanning spot which is smaller than that at the transmitter so that the lines are juxtaposed without the shape of the picture being distorted. The invention is shown by reference to a system in which four sectional pictures are used, so that the received picture is made up of sets I, II, III ..., Fig. 1, of four lines, the first set I being composed of the first four lines of each of the four sectional pictures, the second set II being composed of the second lines 1, 2, 3, 4 of each of the four sectional pictures, and so on. The composite picture is viewed through a grating 6, and the angle 7 of view within which a stereoscopic effect can be observed is increased as compared with a system having only two sectional pictures. The sectional pictures may be recorded separately on four films a, b, c, d, Fig. 2, which are scanned for transmission by discs 8a ... 8d, whose apertures are spaced so that each disc in turn scans a line and are large enough to scan in adjacent juxtaposed paths ; the discs co-operate with separate cells whose outputs are combined for transmission. In a modification, the four sectional pictures A, B, C, D, Fig. 4, are recorded in adjacent frames of a film which is scanned, frame by frame, by a disc 10; at the receiver, an interlaced scanning is employed to produce the composite picture of Fig. 1, by adding a sawtooth component to the framing deflecting oscillation to displace each sectional picture by one line relatively to the preceding one, Fig. 10 (not shown). The sectional pictures are reproduced by a scanning spot small enough to leave a gap of three lines between the consecutive lines of each sectional picture. The deflecting plates 39, 40, Fig. 11, should be set at an angle to the picture lines 1, 2, 3, 4. In a further modification. the scene is viewed by optical systems as shown in Fig. 5, in which cylindrical lenses 14 image the scene as a series of spaced lines, which are projected by a mirror 17 onto an iconoscope screen so as to inter-lineate with other sectional pictures similarly produced. The optical systems are such as to reduce the dimension of the picture along the length of the strips to 1 /nth of the same dimension of the received picture, (n being the number of sectional pictures). If the scene is a " still," the iconoscope screen may be scanned in the usual way; if the scene is moving, the sectional pictures are projected in turn on different iconoscopes, each picture being scanned while another is being projected, Fig. 7 (not shown). The scanning system shown in Fig. 2 may be modified for direct transmission of scenes by projecting the sectional views onto four iconoscopes. It is desirable to have blank spaces 25, Fig. 8, between the sets I, II, III ..., so that a slight instability of the picture does not destroy the stereoscopic effect. These are produced at the receiver, by modifying the saw-tooth frame defecting oscillation. In Fig. 9, it is combined with a stepped-wave form 28 to produce a wave-form 26, the steps producing the blank spaces. Where an interlaced scanning is used, the frame-deflecting oscillation is modified as in Fig. 12 to comprise steps for producing the blank spaces. When instability occurs due to variation of the frame-deflecting oscillation, the viewing-grating may be adjusted in compensation, either manually or automatically by isolating the variations in the framing oscillations and applying them to an electromagnet controlling the viewing-grating. The grating may comprise a screen of cylindrical lenses, and may be removable to allow normal viewing. According to the Specification as open to inspection under Sect. 91, a film suitable for projection and viewing through the line screen is produced by a camera in which two optical systems comprise gratings c<1>, c<2>, Fig. 2, (Cancelled), for producing two images as a series of spaced lines, and these two images are projected onto the sensitive surface e by mirrors d<1>, d<2> so as to be inter-lineated; each system a<1>, b<1>, c<1>, a<2>, b<2>, c<2> should have a suitably graded filter to correct for variations in field illumination of the surface e due to the light traversing paths of different length. An alternative camera has the two views projected on opposite sides of the film e, Fig. 3, (Cancelled) ; a filter h is interposed to correct for the loss of light produced by rays from a1 passing through the film to the sensitive surface. Each observer viewing the projected film may have an individual line screen. For television, the film so produced may be scanned, or the sectional pictures may be produced side by side on a film and scanned as if they were one picture. The line screens may be produced optically. A cathode-ray beam 5, Fig. 7, (Cancelled), may be deflected to traverse a Wilson cloud chamber 4 to produce spaced mist lines through which the image is viewed. Alternatively, a ray of light 5, Fig. 8, (Cancelled), may be traversed over a phosphorus glass plate 4 to cause it to phosphoresce in lines and so vary its transparency. Again, the initial line traced by a cathode-ray beam 2a, Fig. 9, (Cancelled), may fall on a prism 4 having a long after-glow, and this is stated to produce a line screen in the layer 5, which may be curved. Finally, the line screen may be produced by a supplementary cathode-ray beam 6, Fig. 10, (Cancelled), scanning a supplementary fluorescent screen 5 in spaced lines. This subject-matter does not appear in the Specification as accepted.