GB1332352A - System for recording and playing back colour encoded holograms - Google Patents

Abstract

1332352 Colour coded holograms R C A CORPORATION 23 Sept 1970 [30 Sept 1969 28 Nov 1969] 45308/70 Heading G2J [Also in Division H4] To form a colour encoded hologram information representative of the colour of a scene is encoded into mono-chromatic intensity variations which are then illuminated by a coherent monochromatic light beam to form on a record medium a colour encoded Fraunhofer hologram. In one embodiment a sequence of transparencies 34 Fig.3 are illuminated by a light source 31. A striped spatial colour coding filter assembly 36 is disposed adjacent each transparency as it is illuminated, the image produced being focused on to a black and white film. The film produced may be a strip film 60 Fig.4. This film is then illuminated by a beam 46' of coherent monochromatic light which has passed through a diffuser or two-dimensional phase grating 59 to add redundant information. The holograms are recorded on a rotating disc 64 in a spiral formation. To get synchronized exposure disc 64, film 60 and a shutter 43 are all operated by a motor 66. In another embodiment Fig. 5 the mono-chromatic light beam 46 is divided into three sub-beams each of which illuminates a colour separation negative 73, 79, 82 representing the colours red, blue and green respectively. Negatives 73, 79 have different gratings 74, 80 associated therewith. All three modulated sub-beams are recombined and the combined beam interferes with the reference beam 47' to form the colour encoded hologram on disc 64. The hologram is a phase hologram and may be recorded on any photosensitive, thermoplastic, or photo-resist material. Preferably the hologram is then copied and copies are used in reproducing coloured images. A further embodiment discloses the formation of the colour encoded scene prior to formation of the hologram. The scene may emanate from video signals and consequently a brightness signal is contained within a first range of frequencies and the colour signals which are separated from the combined signal are contained within a second range of frequencies. The colour encoded scene is recorded on black and white film which is used to form the Fraunhofer hologram. For reproduction a coherent beam and lens may form a colour encoded image on a pick-up tube (91), Fig.7 (not shown) the output signals from which are separated into three ranges of frequencies corresponding to a luminance Y, a blue representative signal B-Y and a red representative signal R-Y respectively which are then applied to corresponding video amplifiers in a colour television receiver.