GB896544A - Improvements in or relating to signal storage tubes - Google Patents

Abstract

896,544. Cathode-ray storage tubes. ENGLISH ELECTRIC VALVE CO. Ltd. Dec. 13, 1960 [March 21, 1960], No. 9844/60. Class 39(1). In a direct-viewing signal storage tube an additional storage target 4 of relatively low capacitance is provided between the usual storage target 3 and the writing and flood guns 6 and 7. A secondary electron collecting electrode 5 is positioned between the target 4 and the writing and flood guns. In operation the target 4 stores, under bombardment by the writing beam, a positive charge image for a very short time. The dielectric layer of the target 4 is raised to a positive potential of only a few volts thus enabling a very high writing speed. The electrons from the flood beam which pass through the target 4 at the areas bombarded by the writing beam impinge on the fluorescent screen 2 to display an image thereon and also strike the target 3 at corresponding areas, causing these areas to rise in potential by secondary emission to the potential of the metal mesh 31 of the target 3. The bombarded areas of the target 3 are then stabilized at the potential of the metal mesh 31 under the continuing bombardment of the electrons of the flood beam which continue to pass through the target 3 to the fluorescent screen. The stored image may be erased by reducing the potential of the metal mesh 31 to zero. In a storage tube adapted for half-tone operation, e.g. for television display, a further secondary electron collecting electrode is disposed between the storage electrodes 3 and 4. Flood electrons record a positive charge image on the target 3 corresponding to that provided on the target 4 by the writing beam. When the potential of the metal mesh 31 of target 3 is reduced to zero, flood electrons are cut off from the fluorescent screen, except at the positively charged areas of target 3. The fluorescent screen is held at a low potential until the potential applied to the metal mesh 31 is set to zero.