GB1249427A - Cathode ray tube - Google Patents

Abstract

1,249,427. Colour television tubes. SONY CORP. 23 Dec., 1969 [7 March, 1969], No. 62733/69. Heading H1D. In a colour television tube wherein three coplanar beams pass through the centre of a common main focusing lens L M , Fig. 6, the source of the centre beam is located further from the lens than the sources of the outer beams to compensate for the different focusing effect of the lens on the beams so that all beams may be focused correctly at a common point on the screen. In Fig. 6 the centre cathode K G is further away from the lens L M , and the grids G 1 and G 2 are shaped to provide the same cathodegrid spacings for the three beams. The protruding part of grid G 2 forms an auxiliary lens 13 for the centre beam and provides additional focusing for the centre beam, so reducing the distance by which the centre cathode must be displaced. The three beams are converged at the centre of lens L M by an auxiliary lens formed by grids G 2 and G 3 . In modifications, Figs. 7 and 8 (not shown), the cathodes are directed towards the intersection point instead of lying parallel to the axis, and each cathode is surrounded by an individual cylindrical control grid G 1 . In these modifications the end surface of grid G 3 adjacent the grid G 2 may be shaped to be perpendicular to the axis (Fig. 8) or perpendicular to each of the three beams (Fig. 7).