GB863080A - Improvements in or relating to multiple electron beam tubes - Google Patents

Abstract

863,080. Cathode-ray tubes. TELEFUNKEN G.m.b.H. July 12, 1957, No. 22087/57. Class 39(1). A multiple beam tube, e.g. for colour television, has an electrostatic lens comprising three or more diaphragms having beam passing apertures corresponding in number to the number of beams, and different potentials are applied to different diaphragms to focus each of the beams at the target of the tube. A large number of diaphragms, for instance twenty-seven, is used to reduce spherical aberration. Astigmatism may be reduced by making the beam passing apertures non- circular, or by merging the apertures in the middle diaphragms, e.g. the middle seven in the twenty-seven diaphragm arrangement, to form slots, or, Fig. 5, by providing the diaphragms 5 with flanges 17. The beams may diverge, Fig. 6, and the diaphragms may be bent, Fig. 7. The electron guns may be arranged delta fashion or in line. In Fig. 1 the gun anodes 3 are secured to the first diaphragm 5 of the diaphragm system 6. The diaphragms are fixed to the insulating rods 6 by projecting members 14, Fig. 3. Indentations or slots are provided at 15 to allow for thermal expansion.