GB481430A - Improvements in or relating to cathode ray tubes - Google Patents

Abstract

481,430. Cathode ray tubes. RADIOAKT.-GES. D. S. LOEWE. July 6, 1936, No. 18720. Convention date, July 6, 1935. [Class 39 (i)] A cathode-ray tube is provided with an electron-optical system comprising first and second lens systems having an apertured diaphragm therebetween, the first lens system being so adjusted that in the absence of the second system a maximum constriction of the cathode ray beam would occur in the region in which are positioned the second lens system and the deflecting elements, and the second lens system being so adjusted that there is produced on the image screen of the tube a reproduction of the aperture in the diaphragm. The cathode 2 of the tube is provided with a Wehnelt cylinder 4 having a diaphragm 4<1> and provided with a rim 4<11> of a width of the order of the radius of the cylinder 4, and serving to produce a weak preliminary concentration of the beam, the rays of which are thus rendered approximately parallel. The electrons are accelerated by a first anode 5, and the voltage applied to a cylindrical member 6 forming the first lens is adjusted to give a narrow beam in the neighbourhood of the main anode 9 and the deflecting plates 10, 12. A cylindrical member 8 which screens the beam between the parts 6, 9 from interfering fields is provided with a diaphragm at its end remote from the cathode and cooperates with the anode 9 to form the second lens by means of which an aperture in a diaphragm 7 is reproduced on the screen. The diaphragm 7 may be operated at a potential between that of the anodes 5, 9 or may be connected directly with the anode 9. The potentials of the cylinders 6, 8 may be positive or negative relatively to the cathode ray traversing them and relatively to the apertured diaphragms 5, 7. The distance between a pair of deflecting plates is preferably somewhat larger than twice the diameter of the ray in that region and the deflecting potentials applied to the plates are in reverse phase. Dimension and operating potentials are given in the Specification. Specifications 440,087, 452,650, 456,717, and 470,496 are referred to.