GB1142350A - Display system - Google Patents

Abstract

1,142,350. Display apparatus; indicating device. BARR & STROUD Ltd. 14 Dec., 1967 [21 Dec., 1966], No. 57100/66. Headings G4F and G5C. Display apparatus, more particularly intended in an aeroplane in conjunction with an automatic landing system, consists of light sources 10 illuminating a screen 11 through a baffle 12, polarizing filters 13, 14, baffles 15, a compensating plate 16 and signal sheets 17, 18. Signal sheets 17, 18 are made from materials polarized in directions at right angles to each other and carry five signals of interest to a pilot during landing approach, the first four defined separately on sheet 17 and the last signal is defined on sheet 18. The light sources 10 consist of four individual light bulbs 19, 20, 21, 22 each acting as a separate light source for one of the first four signals, and four bulbs 23 together acting as a light source for the fifth signal: baffle 12 isolates optically the five light sources. Polarizing filter 13 passes light from bulbs 19-22 only, whereas filter 14 passes light from bulbs 23 only; the two filters are polarized at right angles to each other, filter 13 having the same axis of polarization as sheet 18. The signals may be defined on sheets 17, 18 by being cut out or bleached by chemical or physical means; the compensating plate 16 ensures uniform illumination by providing attenuating patches in register with the overlapping portions of the signals. Screen 11 is lenticular on its rear surface (Fig. 2, not shown) and slightly diffusing on its front surface to give two clearly defined viewing areas.