GB668854A - Improvements in or relating to image intensifiers - Google Patents

Abstract

668,854. Electron image tubes. WESTING- HOUSE ELECTRIC INTERNATIONAL CO. April 13, 1949 [May 8, 1948], No. 10020/49. Class 39 (i). [Also in Group XX] An image intensifier for use with X-rays comprises a first fluorescent screen 3 on which an image, e.g. an X-ray image, is produced, a photo-electric layer 8 for producing an electron image from this optical image, the photoelectric layer and the first fluorescent layer being disposed in close relationship and being carried on a transparent support member, and means for accelerating the electrons to a second fluorescent screen 9 the surface of which facing the photo-electric layer is coated with a layer 12 of material opaque to light but transparent to electrons of energy exceeding a predetermined value. The first fluorescent screen 3' may be of zinc sulphide with about 0.01 per cent of an activator and about 20 per cent of an alkali halide flux such as sodium chloride; it may be mounted on the glass end wall of the tube, the inner surface of which may have a transparent coating 5A of gold or silver on which the photo-electric layer 8 is deposited. The opaque layer 12 may be of aluminium, silver, or platinum which is preferably made non-reflecting for light on its free surface as by sulphiding it; alternatively the layer may be of carbon or colloidal graphite. The layer may have a thickness between 10<SP>-4</SP> and 10<SP>-5</SP> cm. Magnetic focusing coils 15, 16 may be provided. Reference has been directed by the Comptroller to Specification 652,451.