Patent GB-1261233-A (GB)
Title: Improvements in or relating to holographic image systems
IPC: G03H1/34
Filed: 1969-01-23
Abstract: 1,261,233. Holography. PHILIPS ELECTRONIC AND ASSOCIATED INDUSTRIES Ltd. Jan. 23, 1969 [Jan.26, 1968], No.3935/69. Heading G2J. In a method of image formation by holography in which a reduction in the space-spatial bandwidth is effected, a plurality of substantially identical strip holograms, each having a length substantially greater than its width, is located at a plurality of parallel displaced coplanar locations; alternatively such a strip hologram, or a group of substantially identical parallel strip holograms is moved in the direction of the width of a strip across a twodimensional region; in either case an image is generated therefrom which has substantially no parallax in the direction of the width but has parallax in the direction of the length. The strip hologram may be prepared on a film 26 using a mask, Fig. 6 (not shown) having a slit aperture (29), or by cutting a strip from a larger hologram. The method finds application in the transmission of holographic information and results in a reduction in the bandwidth and/or transmission time of signals. For transmission the film 26 is scanned by means of a flying-spot scanner 30 in conjunction with a demagnification device 31. On account of the elongated shape of the strip it may be preferable for it to be scanned a segment at a time, being moved for this purpose by a stepping motor 34. Instead of a flying-spot scanner a laser and lightdeflection system, e.g. an acoustic light deflector, may be used. Radiation passing through the strip is detected and the resultant signals transmitted, received and then the hologram strip reproduced in conventional manner. An image may be reconstructed from the strip by aligning a plurality of replicas of the strip and then illuminating them in the usual way, it being desirable in so doing to space the strips to avoid the image repeat effect. The illuminating beam may have a slightly cylindrical wavefront to correct vertical distension. Alternatively, Fig. 10, a single strip hologram 60 may be mounted on a plate 61, which may be entirely transparent but is preferably only so behind the strip, and illuminated by means of a laser 62. The plate 61 is attached to a flexible bar 63, mounted on a fixed member 64, and is caused to oscillate vertically by means of a motor 65. In a related embodiment, Fig. 11 (not shown), a strip hologram (70) is mounted on a drum (71), which may be transparent in its entirety or just behind the strip, and which is rotated , the moving strip being illuminated by a laser inside the drum. In each of these embodiments if the position of the strip is repeated with a frequency of at least 20 H 2  then the entire image may be viewed with horizontal, but without vertical, parallax. The system may be used to produce moving images see Fig. 12. Strip holograms 80 corresponding to successive views of a moving object may be attached to or reproduced on a reel of film 81. The film is then illuminated by means of a laser 84 and viewed from a point 85, the desired viewing area being defined by an aperture 86 in a mask.