GB1323691A - Cathode ray tube arrangements - Google Patents

Abstract

1323691 Cathode ray tubes EMI Ltd 10 Aug 1970 [22 Aug 1969] 41888/69 Heading H1D A deflecting/focusing system for a cathode ray tube comprises a first electrode 5, Fig. 2, which co-operates with a first pair of electrostatic deflection plates 6 to form a cylinder lens, a second electrode 9 which co-operates with a second pair of electrostatic deflection plates 8 to form a second cylinder lens, and a postdeflection acceleration system comprising cylinders 10-12 of increasing diameter adapted to accelerate the beam to a charge storage or display screen 13. The electrode 5 may comprise a pair of parallel plates extending from a final anode (not shown). Mesh electrodes 7 and 9 co-operate with their respective deflection plates 6 and 8 to produce electric fields which tend to compensate for image curvature produced by the deflection plates, and the electrode 7 also serves as an electrostatic screen between the two sets of deflection plates. The distances between the grids 7 and 9 and the respective deflection plates 6 and 8 are calculated to give optimum curvature correction for given grid potentials, which may be equal to those of the plates or slightly lower so that secondary emission from the grids is collected by the plates. A modified arrangement, Figs. 3 and 4 (not shown), comprises in order: a cylindrical electrode (24) attached to the final anode and operated at 1500 V; a decelerating cylindrical electrode (25) at 1200 V; a mesh (26) at 800 V followed by first deflection plates (27) at 400 V; a second mesh (28) at 400 V followed by second deflection plates (29) at 200 V; a mesh (30) at 180 V; accelerating electrodes (31, 32) at 500 V and 5 KV or higher, and a screen at 5 KV or possibly up to 20 KV.