GB470004A - Improvements in or relating to cathode ray tubes - Google Patents

Abstract

470,004. Cathode-ray tubes. MARCONI'S WIRELESS TELEGRAPH CO., Ltd., and LEVIN, N. Feb. 3, 1936, No. 3269. [Class 39 (i)] A cathode-ray tube for use in television systems has a cathode 1, an apertured control electrode 2, and a first anode 3, the dimensions of the cathode being large compared with the size of the aperture in the control electrode, the beam being focused upon the aperture by a succeeding electron assembly which is so arranged as not to be effected by varying voltages applied to the control electrode, which is placed at a distance of approximately 0À005 inch from the cathode, the first anode being at a distance of 0À02-0À03 inch from the control electrode ; the electron assembly succeeding the first anode may give an electron accelerating or decelerating region. A long cylindrical electrode 4 with a small central aperture in its end faces is arranged between the anode 3 and another apertured anode 5. The potential of the anode 3 may be 1000 volts, the electrode 4, zero and the anode 5, 3000 volts. The rays are projected on a screen 6, which may be also the final anode. The arrangement is such that the scanning image on the screen of the control-electrode aperture changes in intensity but not in size or shape, or does not exceed a certain size. In a modification, a preliminary focus of the aperture in the control electrode is formed in the aperture in the electrode 4 nearest to the anode 5, and diverging rays are stopped by the anode 5. In another tube, Fig. 4, two apertured anodes 3, 3a are arranged between the control electrode 2 and the cylindrical electrode 4, and the anode 5 consists of an apertured plate in a cylinder 5a which may be a screening deposit of metal on the envelope. The anodes 3, 3a form an image of the control-electrode aperture on the first aperture 4a of the electrode 4, and the second aperture 4b in that electrode, with the anode 5, re-forms the image on a screen, not shown.