| 摘要 |
1,056,437. Colour television receivers. SONY CORPORATION. Oct. 11, 1963 [Oct. 13, 1962], No. 40214/63. Heading H4F. The invention relates to a colour television receiver, Fig. 5, which utilizes a chromatron cathode-ray tube 6, a received N.T.S.C. signal comprising a luminance component Y and a chrominance sub-carrier component Cs being applied to the tube gun 5 to modulate the beam intensity whilst a sinusoidal potential S at the sub-carrier frequency is applied between the switching grids 4a, 4b. Operation proceeds as shown in Fig. 4 with the beam deflected cyclically over the red, green and blue phosphor strips 3R, 3G and 3B so as to reproduce the colours at the places marked by a O in phase with their representation by the chrominance signal Cs. With the object of improving the accuracy of colour reproduction a further signal P at three times the sub-carrier frequency is also applied to the tube gun so as to reduce the beam intensity at the places marked by an X. In accordance with the invention the amplitude of signal P is modulated in accordance with the amplitude of the sub-carrier signal except at low amplitudes. In carrying out the invention the signal P, which is derived by means of a frequency multiplier 14 from a signal of subcarrier frequency obtained from an oscillator 12 synchronized by the sub-carrier " bursts," is applied to the tube gun 5 via an amplitude modulator 15 which is controlled by the output of a detector circuit 16 responsive to the chrominance signal Cs. Furthermore the detector incorporates a bias source 20 which prevents the detector producing an output from lowamplitude (i.e. low saturation) sub-carrier signals. In practice stages 14 and 15 are combined into a single stage comprising a non-linear amplifier with a resonant anode circuit tuned to three times sub-carrier frequency. Fig. 7 shows one arrangement based on the use of a triode 26. A second circuit, Fig. 8 (not shown), uses a pentode. |
