| 摘要 |
PURPOSE:To control the luminance and the contrast of an auxiliary picture independent of a main picture by detecting the beam current value of an image receiving tube, controlling the level of a main video signal, detecting the mean luminance level of an auxiliary video signal and controlling the level of the auxiliary video signal. CONSTITUTION:A main screen from a main TV circuit MK is projected on the whole tube surface of the image receiving tube 18, and an auxiliary screen from an auxiliary TV circuit SK is projected in the main screen. A beam current detection circuit 31 detects the current value of a beam current supplied from a deflection/voltage circuit 26 to the image receiving tube 18. The output from the circuit 31 is supplied to a main video/chrominance components circuit 8M, and the level of the main video signal is controlled. A luminance signal Y from a matrix circuit 14 is supplied to a level detection circuit 33, and the mean level is detected. The output from the circuit 33 is supplied to a gain control amplifier 32. Thus, the luminance and the contrast of the auxiliary picture can be controlled independent of the main picture.
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