GB1106891A - Improvements in or relating to electron-optical image converter tubes - Google Patents

Abstract

1,106,891. Semi-conductor image converters; cathode-ray tubes. LABORATOIRES D'ELECTRONIQUE ET DE PHYSIQUE APPLIQUEES, LEP. 10 May, 1962 [10 May, 1961], No. 18105/62. Headings H1D and H1K. A picture transforming tube comprises two systems, one of which is adapted to receive a primary pattern of a first radiation and to derive therefrom an emission-stimulating quantity, the other being capable of emitting a second radiation when stimulated to reproduce a similar secondary pattern; each system comprises a diode mosaic with one electrode in the form of a multiplicity of discrete elements and the other electrode in the form of a continuous surface, the discrete elements of the two systems being juxtaposed so that the elements of one system stimulate emission from the other system to induce secondary pattern reproduction on the continuous surface of the other system. Figure 1 shows a photo-sensitive and photo-emissive target comprising a plate M of a P-type semiconductor material, such as germanium doped with gallium, which is flat on one side and has a mosaic of projections on the other; each of the projections is covered with an N-type semiconductor, such as germanium doped with antimony, and each of these is coated with a photo-emissive layer Ph, of a material such as caesium. A layer of antimony may be provided between the N-type semi-conductor and the photo-emissive layer, Fig. 1a (not shown). The target is shown in Fig. 2 arranged in a tube so that the target can be cooled, for example by liquid nitrogen flowing in a jacket (not shown) surrounding the tube or by application of solid carbon dioxide. The mosaic side of the target is illuminated by a source S, for example of monochromatic ultra-violet radiation, and the source may be situated at an angle, as shown, to reduce any resultant photo-electric effect on the PN junctions. An alternative way of reducing the latter effect is by putting opaque insulating material, e.g. a " glass " comprising 40% As 20% I and 40% S, in the gaps between the mosaic projections (Fig. 1a, not shown), and in this case the source S may be normal to the target. In operation an infra-red image is focused on the target and electrons emitted from the target are accelerated through a screen grid G on to a fluorescent screen E; the accelerating potential should not be high enough to impair the efficiency of the junctions and may be about 10 volts.