Patent GB-1053553-A (GB)
IPC: G01S1/02
Abstract: 1,053,553. Cathode-ray tube displays. ELLIOTT BROTHERS (LONDON) Ltd. June 24, 1963 [June 22, 1962], No. 24210/62. Heading H4T. In an arrangement in which the display on a cathode-ray tube is viewed in a reflector, an increase in the field of view, otherwise limited by the size of the tube screen, and by the optical system, is produced by moving the reflector and causing the motion of the latter to operate means which varies the position and/or attitude of the display on the tube screen such that the image of the latter seen in the reflector remains stationary. The invention, although not so limited, is particularly described in connection with an arrangement in which symbolic information traced on the screen of a cathode-ray tube is superimposed " at infinity " on the normal field of view of the pilot of an aircraft by reflection at a semireflector. In one embodiment (Fig. 1, not shown) the tube screen is horizontal and the reflector is arranged to pivot about an axis at right angles to the axis of the tube so that when the tube display moves towards either extremity (fore-aft) of the tube screen appropriate movement of the reflector together with a compensating shift of the image on the tube screen maintains the reflected image in a fixed position relative to the field of view of the pilot and further allows additional movement of the image towards the extremities of the tube screen since the effect of the compensating shift is to move the tube display away from the screen extremities towards the centre. In another arrangement (Fig. 3, not shown), concerned with extending laterally the range of movement of the display, the symbolic information comprising a circle 21, with laterally projecting lines 22 is produced by deflecting the beam of tube 31, Fig. 4, under the control of 90 degrees phase displaced sinusoidal waves from respective generators 40, 42, the former producing at spaced intervals one or more complete sine wave cycles and a linear sawtooth voltage whilst generator 42, which produces sine wave when generator 40 is producing sine wave, produces a constant voltage determined by a pitch sensitive device 43 when generator 40 is producing a sawtooth wave. Generator 40 is also controlled by a heading sensitive device 41 so that when the outputs of 40 and 42 are applied to the tube together with bright-up signals from a generator 44 the position and attitude of the displayed symbol is indicative of the flight condition of the aircraft. However, this arrangement does not indicate a banked condition of the aircraft and to produce a beam deflection component indicative of the banked condition the outputs of generators 40, 42 are fed to respective sine-cosine resolvers 45, 46 operated by a drive unit 48 controlled by a roll sensitive device 49 the like-phased resolver outputs then being added in pairs in summing circuits 50, 51 and fed to tube deflection amplifiers 52, 53 via a switched resistance network including switches 56 to 59 and potential dividers 60 to 63. The switches are mechanically linked to the semireflector 34 so that when the latter is rotated about the tube axis operation of switches 56 and 59 introduces shift voltages into the deflection amplifiers to compensate for such rotation so as to produce a stationary image in space whilst the simultaneous operation of switches 57-58 by cross-coupling sine and cosine phased components produces compensation for rotational shift of the display symbol through angle # (Fig. 3, not shown) inherently produced by the optical system. The switches 56 ... 59 may be replaced by potentiometers to allow of continuously variable compensation, Fig. 5 (not shown), and automatic movement of the semireflector in accordance with the displacement of the symbol on the tube screen may be provided by means of an electric motor controlled by the output of the deflection generator, Fig. 6 (not shown).