GB476338A - Improvements in image transforming electron discharge tubes - Google Patents

Abstract

476,338. Image intensifiers. BRITISH THOMSON-HOUSTON CO., Ltd. June 8, 1936, No. 16000. Convention date, June 8, 1935. [Class 39 (i)] In an image intensifier the photo-electric cathode 4 is formed on a re-entrant stem 2, Fig. 1, or on the end wall 16, Fig. 4, of the envelope ; caesium vapour to coat the cathode is admitted by the nozzle 8 and a heater may be admitted through an orifice 9. To prevent the caesium vapour spoiling the insulation provided between this cathode and a fluorescent screen 5, a metal tube 6 or a metallized surface 18 is provided near the cathode and extended towards the screen 7. The tube may form part of the envelope. The accelerating anode 7 may be a cylinder mounted on a re-entrant stem 3 carrying the screen 5, and is at screen potential ; in one form the anode is carried by an insulating ring within the tube 6. As shown in Fig. 4, the anode may be a coating 19 on a tube 15 extending from the screen end of the envelope or the tube 15 may be metal up to the point 23 and serve as the anode. Shielding coatings such as 20 may be provided on the outside of the envelope except where the cathode and screen are formed. Where the envelope is of ceramic material, suitable windows-which may be optical lenses-are used for the cathode and screen. When used with infra-red images the windows are of material, which permits passage of the rays. Magnetic focusing may be used with the anode 7. The ends of the anode 7 and tube 6 are rolled over as shown.