GB849276A - Improvements relating to cathode ray tubes - Google Patents

Abstract

849,276. Cathode-ray tubes. NATIONAL RESEARCH DEVELOPMENT CORPORATION. Dec. 11, 1956 [Dec. 15, 1955], No. 37796/56. Class 39(1). A " flat " cathode-ray tube, such as described in Specification 739,496, in which the beam 14 from a gun 12 is deflected into any one of a plurality of angularly displaced paths lying in a common plane by conventional deflection plates 16, and out of the plane and into impact with the screen by an array of deflection electrodes 26, has a curved, slotted, accelerating electrode 20 disposed between a low voltage region including the gun and the deflection plates 16 and a high voltage region including the deflection electrodes 26. Electrode 20 may be positioned so that its centre of curvature is at a point between the deflection plates 16 and the electrode 20 in order to increase the angles of deflection. An oppositely curved electrode may be disposed between electrode 20 and the deflection electrodes 26 in order to straighten the beam paths so that a rectangular raster is obtained. The curved electrode 20 and the additional oppositely curved electrode also serve to focus the beam in a plane normal to that of the screen. In a further embodiment for use in a radar display system in which the angular width of the scan remains constant, the deflection electrodes 26 are arcuate segments increasing in length with distance from the gun.