GB916029A - Colour television apparatus - Google Patents

Abstract

916,029. Colour television. PYE Ltd. April 21, 1959 [April 21, 1958], No. 12643/58. Class 39 (1). [Also in Group XL (b)] A light filter for a colour television tube comprising transparent imperforate and perforate sheets which are assembled together with light filter material applied over the surface of the perforate sheet is incorporated in the target structure of a pick-up tube. In Fig. 1, 61 is an imperforate glass disc bearing a signal plate 62 and 60 a perforate glass plate carrying a filter layer 63 and a second signal plate 64. The target area is covered with photo-conductive material. In an orthicon type target photo-emissive material is applied as a mosaic on insulating material interposed between the photo-emissive material and the opposing signal plate or the perforate plate may itself constitute the insulating layer between the photo-emissive layer and the signal plate. The perforations may be slots and the signal plate 62 may be composed of interconnected parallel strips. The target of a three-colour tube, Fig. 7, comprises an imperforate glass disc 161, a transparent conducting signal plate 162, a perforated glass plate 160, a minus blue filter 163, a further signal plate 164, a second perforated glass plate 260, whose perforations 266 are in register with but of larger area than the perforations 166 in the plate 160, a minus green or red filter 263 and a third signal plate 264. Photoconductive material 165 is deposited on the parts of plate 162 exposed through perforations 166, 266, on the parts of plate 164 exposed through perforations 266 and on the exposed surface of plate 264. In operation signals corresponding to a black and white image are obtained from original plate 162, to the red and green components from signal plate 164 and to the red component alone from plate 264. The " minus blue " or " red and green " component is phase inverted, Fig. 9, and mixed with the " black and white " signal to give a blue output, and the uninverted " minus blue " is mixed with the phase inverted red signal to give the green output signal. Specifications 888,832 and 888,839 are referred to.