GB1241018A - Improvements in cathode ray tubes - Google Patents

Abstract

1,241,018. Cathode-ray tubes. RANK ORGANISATION Ltd. 7 May, 1969 [13 May, 1968], No. 22558/68. Heading H1D. In a flat cathode-ray tube wherein an electron beam from a gun 3 is projected parallel to the screen 2 and deflected along the screen by means 12, the angle of attack of the beam on the screen is increased by the provision of an electrostatic field which increases with increasing distance from the means 12. The field may be provided by parallel strips 16 which are connected inside or outside the tube by equal resistances R, the spacing between the strips varying progressively as shown. Alternatively, Fig. 5 (not shown), the strips 16 may be equally spaced but connected by resistances which increase progressively. The strips may be constituted by conductive strips formed on an insulating substrate by printed circuit technique. One end of the resistance chain is connected to beam potential and the other end to near cathode potential; preferably a grid 19 at beam potential is provided near the screen so that an accelerating potential may be connected between the grid 19 and a metal backing layer 20 on the screen, thereby increasing the angle of attack still further and also improving the focus. The screen 2 may be formed on the envelope or on an adjacent transparent substrate. The electron gun 3 may be disposed at one edge of the tube (Fig. 2, not shown) or behind the screen (Fig. 1, not shown) in which case the beam is reflected through 180 degrees before entering the deflection means 12.