GB1259698A - Single-gun, plural beam cathode ray tube - Google Patents

Abstract

1,259,698. Colour television tubes. SONY CORP. 22 Dec., 1969 [30 Dec., 1968], No. 62494/69. Heading H1D. In a colour television tube of the type wherein three beams converge at the centre O of a common focusing lens L M , Fig. 3, individual pre-focusing lenses are provided for each of the beams. In Fig. 3 the cathodes are aligned with respective apertures in the closed ends of cupshaped grids G2 and G3 which form the respective pre-focusing lenses L R , L G and L B ; the apertures in grid G2 may be surrounded by cylinders 23, as shown. The powers of the prefocusing lenses may be equal, or alternatively the powers of the outer lenses L R and L B may be greater than that of L G to compensate for the slight aberrations imparted to the outer beams due to their passage through the main lens L M at angles to the axis. In the tube shown, the cathodes are coplanar and the beams are converged on a shadow mask M by magnetic convergence means F, (Fig. 4, not shown); this may be replaced by electrostatis convergence means (Fig. 5 and 6, not shown) or omitted, in which case the signals applied to the cathodes are suitably delayed. Alternatively the cathodes may be disposed at the corner of an equilateral triangle.