| 摘要 |
1,243,163. Colour telvision tubes. PHILIPS ELECTRONIC & ASSOCIATED INDUSTRIES Ltd. 6 Feb., 1970 [8 Feb., 1969], No. 5806/70. Heading H1D. In a colour television tube of the shadow mask type wherein three co-planar beams pass at different radial positions through a common focusing/converging lens, the pre-focusing effect of electrodes preceding the common lens is weaker for the outer beams than for the centre beam to compensate for the stronger focusing effect of the common lens on the outer beams. In Fig. 3 the three cathodes 6-8 are aligned with respective apertures in the first three grids 9, 30 and 34, and the pre-focusing effect of these electrodes is increased for the centre beam by the bulge in the centre of the second grid 30. In a modification, Fig. 2 (not shown), the second grid (13) is flat and the central aperture in the third grid (17) is smaller than the two outer apertures. The main lens comprises electrodes 24 and 25, and the third grid 34 is provided with an annular bulge 28 having the same diameter as the end portion 26 of the fourth grid. If the three guns have independent electrodes the required differences in pre-focusing may be achieved by using different potentials on the electrodes of the various guns. |
