GB519015A - Improvements in and relating to electron tubes - Google Patents

Abstract

519,015. Cathode-ray tubes. BRITISH THOMSON-HOUSTON CO., Ltd. July 11, 1938, No. 20500. Convention date, July 10, 1937. [Class 39 (i)] In cathode-ray tubes and electron microscopes using an electron-optical lens for controlling the electron flow, the lens includes a silver or other metal foil F<1> permeable to electrons having a velocity corresponding to less than 50 volts, the accelerating voltage at the electrode being restricted to less than this voltage. The foil is straight or it is curved to form a convergent lens with the Cylinder E1 ; a second foil F2 may be placed across the aperture in the second.cylinder E2. In a further arrangement the foil F, Fig. 3, is carried by the middle of three electrodes forming a divergent lens which with the convergent lens formed by the cylinders E1, E2, gives chromatic correction. The foil may divide the tube into two separate chambers, one with the electron gun having a gaseous filling, the other with deflecting plates and luminous screen being highly evacuated ; a further foil may separate the two pairs of deflecting plates. The foil may be supported by a foraminated carrier which may be spherical. The Specification as open to inspection under Sect. 91 also describes a photo cell wherein the cathode is a coating on the envelope wall and a foil is used to cover the cathode or to form a septum separating the cathode from the anode. This matter does not appear in the Specification as accepted.