GB1142091A - High sensitivity beam-index target screens and cathode ray tubes embodying same - Google Patents

Abstract

1,142,091. Light guides. D.M. GOODMAN. Feb.15, 1966, No.6540/66. Heading G2J. [Also in Division H1] In a cathode-ray tube in which electromagnetic radiation is picked up from the screen end of the tube as indexing signals in a multi-colour television tube, the radiation is picked up by a light guide constituted by arrays of optical fibres 88, Fig.4, which are incorporated in the tube screen as indexing strips, one associated with each colour triplet R, G, B. The fibres emerge from the top and bottom of the screen 72, Fig. 1, in two arrays 74, 76 which are led along the inside of the envelope wall 80 to the gun end of the tube where they emerge in clusters 78 or possibly in four clusters, Fig.3 (not shown). The fibres may be round or rectangular, single strand or multi-filament. The indexing optical fibres may carry dimples or recesses 94, Fig.4, coated with phosphor material or they may be formed of electron sensitive scintillating glass and the fibres may be placed directly on the tube faceplate, Fig.6 (not shown), or on top of the screen phosphors, Fig.7 (not shown). The fibres may be in two interlaced arrays to pick-up separate indexing signals, Fig.5 (not shown), the fibres being linked together by the rods so that all the fibres may be pre-formed into a single subassembly which is deposited on the screen after the deposition of the colour phosphors. In a further embodiment the indexing optical fibres are in contact with the tube faceplate and the tube envelope constitutes a light guide which leads the optical indexing signals to the gun end of the tube, Figs.8-10 (not shown). In this arrangement the tube neck projects beyond the glass seal containing the pin connections. The indexing optical fibres may be constituted by glass powder material embedded in the faceplate. The strips may be in the same plane as the colour phosphors or they may extend through the phosphor layers or they may be covered with the phosphor layers. Reference is also made to the use of a scanning light beam, e.g. an ultraviolet beam, instead of an electron beam.