Patent GB-1138989-A (GB)
Title: Information display system
IPC: H04N9/31
Filed: 1967-12-05
Abstract: 1,138,989. Radar; cathode-ray tube circuits. NATIONAL CASH REGISTER CO. 5 Dec., 1967 [10 March, 1967], No. 55211/67. Headings H4D and H4T. [Also in Divisions C4, G2 and H1] In an information display system red, green and blue light beams 58r, 58g and 58b, Fig. 2. are directed via mirrors 64 and diverging lenses 60r, 60g and 60b on to respective screen areas 65r, 65g and 65b, Fig. 5, of a cathode ray tube. Portions e.g. image portions 20g, 20b, 20r and 20k of the screen areas are selectively rendered non-reflective (see later) and lenses 66r, 66g and 66b which overlie the corresponding screen areas receive and converge the light reflected from the screen areas on to diverging lenses 68r, 68g and 68b respectively. The three resulting divergent light beams are then directed via mirror 69, Fig. 2, towards a common lens 70 where the imaged portions 20g(L), 20b (α), 20r(0) and 20k(#) are superimposed i.e. the three coloured light beams combine to make up a white light except in the image portions which appear as green, blue, red and black images respectively (e.g. because the red light beam is imaged with image portions 20g, 20b and 20k and not with 20r and because both the blue and green light beams are imaged with image portion 20r, image portion 20r(0) is exposed to red light only and appears as a red image, "0", against a white background). The combined image is projected via lenses 72, 73 and 75 and mirrors 74 on to a viewing screen, a reference or background image e.g. a map, on a transparency 76 being introduced with the projection system, Fig. 2. So that the beam from diverging lens 60r, 60g and 60b are substantially normal to the respective screen areas the lenses are positioned adjacent a line e.g. 62, Fig. 5, normal to and passing through the centre of the corresponding screen area. Lenses 68 are positioned adjacent lenses 60. The three light beams are derived from a Xenon lamp 50, Fig. 1, by means of mirrors 52, converging lenses 54 and coloured filters 56r, 56g and 56b. The cathode-ray tube, Fig. 3, which is of the type disclosed in Specification 1,031,327, comprises a fibre optic face plate having a concave inner surface and flat outer surface against which a dichroic filter 46 and a photochromic film 48 are placed, the photochromic film being rendered opaque in response to ultra-violet light emitted by the tube phosphor screen 44 which is coated on the inner surface of the tube face plate, the dichroic filter being transmissive to ultraviolet light and reflective to visible light. In operation the electron beam of the tube is arranged to write the information e.g. characters 0, α, L and #, to be displayed on the respective screen areas 65 against which are positioned lenses 66 (preferably rectangular lenses) in sequence. Radar.-The display system may be used to track air traffic in which a computer converts information from radar equipment into three sets of signals i.e. character selection signals, colour selection signals and position selection signals. The information to be displayed may be that a flying object detected by the radar equipment is an unidentified aircraft located at a position represented by the co-ordinates (5, 14) on an established x-y axis, flying at a height of 30,000 ft. The computer thus for example provides character selection signals designating the character α (generated by a character generator) indicating the height of 30,000 ft., colour selection signals indicating by, for example, a blue image that the aircraft is unidentified, and position selection signals designating co-ordinates (5, 14) indicating the particular location of the aircraft. The operation of the cathode-ray tube to display such information is described with reference to Fig. 6, not shown.