Patent GB-1422051-A (GB)
Title: Reducing interference voltages between a gauze-electrode and a target in a television camera tube
IPC: H01J31/38
Filed: 1973-01-25
Abstract: 1422051 Image pick-up tubes PHILIPS ELECTRONIC & ASSOCIATED INDUS-  TRIES Ltd 25 Jan 1973 [28 Jan 1972] 3835/73 Heading HID A TV camera tube assembly comprises an e.m. scanning system with an elongate TV camera tube including a target, adjacent gauze electrode 5 and an elongate gauze electrode connection conductor 37 extending along the inside of the scanning system, the conductor being included in use in an electrical connection loop for applying a direct voltage between gauze and target, the length direction of at least part of the connection conductor within the scanning system having at least a component around the tube axis so that in operation the interference voltage between gauze and target by energization of the scanning system will be reduced or eliminated. Wire 37 has a step 38 (perspective view, Fig. 3, not shown) and inhibits two-pole field interference for any angular position of the tube, but is sensitive to axial displacement. The latter can be an advantage since slight displacement may correct wire 37 asymmetry. A doubled conductor arrangement (Fig. 4, not shown) produces insensitivity to axial displacement. Symmetrical 4-pole field interference effects may be suppressed by wires (41), (42) with 180 degree steps displaced 90 degrees (Fig. 5, not shown), small currents flowing in the wires due to the 4-pole field interference suppression but none due to that of a two-pole field. The former induction currents may be eliminated by the Fig. 6 (not shown) arrangement with single wire (43) with a 90 degree step, but does not suppress two-pole field interference. A doubled arrangement with two wires (43) at 90 degrees produces insensitivity to axial displacement. All interference signals from 2-pole, 4-pole, 8-pole fields &c. may be suppressed by a single wire with a 120 degree step at one third and at two thirds of its length. Axial sensitivity may be suppressed by two of these wires at 180 degrees which also suppresses interference from 6- pole fields and higher harmonics. Asymmetrical 4-pole fields may be considered as a symmetrical 4-pole field on a symmetrical 8-pole field, the latter being compensated by four wires at 45 degrees each with a 180 degree step, similarly nth order poles may be supppressed by ¢n wires. 2-Pole and 4-pole interference maybe suppressed by a wire with three 90 degree step at , ¢ and ¥ length positions (Fig. 7, not shown). 8-Pole interference may be suppressed with a seven step wire (315 degrees total angular displacement) and for nth order fields where n##, a one turn helix is required (Fig. 8, not shown). The latter corrects all order fields, and the wire may be against the inner wall of the envelope. Axial sensitivity may be removed by a similar diametrically opposed wire, but preferably by continuation beyond both ends the deflection field (Fig. 9, not shown). The pitch may be 96 mms. The pitch may be a sub-multiple (Fig. 10, not shown) and deviations in pitch compensated by an identical wire at 180 degrees. If pitch is not exactly adapted to field length, 2 helical wires turning in opposite senses may be used, or a plurality of pairs of such wires (e.g. two diametrically arranged pairs). The gauze may include sleeve (50), (Fig. 11, not shown), connected to wire (49) with sleeve (51) encircling the gun with electrodes (52-55). One or more wires (49) may be used, and may have one or more turns. Sleeves (50), (51), extend over the stray ends of the field, and, acting as wire coincident with the axis, suppress stray field irregularity effects. Differences in field due to different coil systems have no adverse effect. General tube details are as in the Divisional Specification.