GB360654A - Improvements in and relating to cathode ray tubes - Google Patents

Abstract

360,654. Cathode-ray tubes. CHEVALLIER, P. E. L., 1, Rue Pierre Curie, Paris. Oct. 30, 1930, No. 32635. [Class 39 (i).] To produce a point image on the fluorescent screen of a cathode-ray tube in television, telephotography, &c., a potential difference is applied between the cathode F, Fig. 1, and the walls D, E of a chamber into which the electrons are projected, to assist the electrons towards the screen G of this chamber, and a second potential difference is applied between the cathode and an electrode P along the path of the electrons, the latter potential being one-half to one-quarter of the former. For a ratio of the two potentials within these limits, the electron beam is concentrated to form a bright point image, other ratios giving a linear, or extended image. The potentials may be obtained from a rectifier and potentiometer. The electrode P may comprise two flat or conical diaphragms and two cylinders of different diameter, all coaxial as shown in Fig. 3. The walls of the chamber C around the cathode may be insulated from the walls D, E and given a negative potential to modify the modulation produced by a control electrode J. Coils and plates are provided to deflect the beam. A demountable tube may be formed of metal parts and insulating gaskets, a metallized glass window G carrying a fluorescent screen, and a valve X leading to a vacuum pump. In a modification, the envelope is of glass permanently sealed and coated with metal on its inner surfaces.