GB1328677A - Display apparatus - Google Patents

Abstract

1328677 Cathode-ray tube displays; pulse amplitude limiting SPERRY RAND CORP 7 Oct 1970 [8 Oct 1969] 47796/70 Headings H3T and H4T Altitude display apparatus for a mobile craft, specifically an aircraft, comprises means for intensity modulation of a spirally scanned time base on a display cathode-ray tube. The display thus produced comprises a horizon 12 (Fig. 1), runway 13, in a single point perspective and ground plane grid 14, also in perspective. Additionally, during the fly-back intervals of the spiral time base, deflection-modulation of the beam is employed to trace horizontal and vertical flight director bars 15 and 16 respectively together with a centre reference marker 17. Fig. 2, shows the general arrangement of the spiral time base generator (which produces an interlaced scan) the detailed circuit of which is given in Figs. 4a and 4b and Fig. 34 shows the overall scheme employed in the production of the display, the various "blocks" of the latter figure also being given in circuit diagrams. Fig. 3, shows the general form of the voltage controlled symmetrical limiter 21 (Fig. 2) in which the level of the output E OUT derived from the square wave input E IN from generator 20 is limited by the input to amplifier 30 from ramp generator 22 (Fig. 2). The detailed circuit is shown in block 21, Fig. 4b. The horizon 12 is produced by blanking the beam for one half of its period (i.e. 180 degrees) and by varying the phase of the blanking pulse as a function of roll # the horizon, i.e. 50% of the spiral raster, rotates about the centre of the raster. When, however, lateral deviation X and/or pitch # inputs are present, correct perspective is maintained by causing the rotation to occur about the centre of the display (Figs. 26a and 26b). The runway 13 is produced by a bright-up pulse having a width of 15 degrees and consists of a wedge shaped area the "vanishing- point" of which is situated at the centre of the raster and the perspective of which is controlled by the variable parameters a, b, Á and T derived from the aircraft position and altitude relative to the runway as defined by ILS beams and by the aircraft heading. The ground plane grid 14 is produced and its perspective is controlled in a generally similar manner. After fly-back of the beam has occurred a period of about eight cycles of the time base is allowed for the various filters to recover from the retrace transient and during this period the centre cross mark 17 and the flight director bars 15 and 16 are traced by the application of sinusoidal voltages to the X and Y deflection circuits, the position of the bars 15, 16 being determined by input voltages e and g respectively (Figs. 31a and 31b). Pitch motion # and lateral deviation X are displayed by vertical and lateral movement of the raster as a whole only a portion of the raster being visible in a viewing area (Figs. 9 and 10).