| 摘要 |
690,155. Cathode ray tubes. RADIO CORPORATION OF AMERICA. May 22, 1951 [May 26, 1950], No. 11977/51. Class 39(i). An electron beam controlling arrangement for a cathode-ray tube comprises beam deflecting means disposed in a region spaced from a target electrode in the tube, means for directing electron beam components into the deflecting region at different angles, and means for energizing the deflecting means to cause all the beam components to scan a raster at the target electrode, and is characterized by the provision of electron optical means which are arranged adjacent to the paths of travel of the electron beam components and which are energizable to effect convergence of all the electron beam components at all points of the raster. The arrangement may be applied to the receiving tube of a colour television system which may be of the type shown in Fig. 4 comprising three electron guns 47, 48, 49 which produce beams 56, 58, 59 which converge on a mesh 53 and excite different fluorescent areas on the screen 51. Normally when the beams are deflected they cease to converge on the mesh 53 and to correct this an auxiliary focusing system is provided which may comprise two elliptical coils suitably energized at the horizontal and vertical scanning frequencies Fig. 3, (not shown). In the modification shown in Fig. 4 synch pulses at the vertical scanning frequency are fed to the wave shaping apparatus 63 which feeds a sawtooth and a parabolic waveform to the vertical control voltage generator 65; similar waveforms at the horizontal scanning frequency are fed to the horizontal convergence control voltage generator 67, and the combined output of the two generators is fed to the focusing anode 55. In a modification Fig. 5, (not shown), using a tube with a single electron gun the beam from which is rotated magnetically to provide effectively several beams, the required waveform derived from the deflection voltages is fed to a convergence coil instead of to a focusing anode, |
