GB1377364A - Electron discharge devices - Google Patents

Abstract

1377364 Cathode-ray tubes EMI Ltd 13 Jan 1972 [16 Jan 1971] 2197/71 Heading H1D An electron discharge device comprises a first section including an hermetically sealed first envelope having an electrode or screen carried on the inner surface of a closure member which carries on its other surface an electrode of a second section enclosed within an envelope which is hermetically sealed to the first envelope. In Fig. 1 the first section 1 is an image intensifier including a phosphor layer 7 on a 4 micron thick mica sheet 6 sealed across an aperture in a plate 5 which is sealed to an annular member 4 of channel-shaped cross-section. When this section is evacuated the sheet 6 bows inwardly (Fig. 2, not shown) and it is operated and tested, taking account of this bowing; a photo-conductive layer 8 is then deposited on the sheet 6, and after it has been inspected for blemishes, a vidicon section 2 is sealed to the first section at 11 by argon arc welding or by an indium seal. If a fault develops in the second section, the seal 11 may be opened and a new second section joined on. In another example, Fig. 3 (not shown), both sections are image intensifiers, the first section being sensitive to infra-red. Owing to the isolation provided by the mica sheet, the two photo-cathodes may be processed under different conditions. In a further example, Fig. 4 (not shown), the first section is an oscilloscope tube of small diameter operated at low voltage to achieve high writing speed, and the screen is therefore not aluminized; normal viewing size and brightness is restored by the second section which is a magnifying image intensifier.