| 摘要 |
PURPOSE:To always set picture quality optimum by changing a DC voltage for controlling picture quality in accordance with the brightness of a screen and setting the picture quality sharper as the screen is darker. CONSTITUTION:A DC-reproduced picture signal being a luminance signal is added to a variable resistor 1 for controlling picture quality, whereby the volt age for controlling picture quality is changed in accordance with the picture signal. In the picture signal on the black screen, the voltage of an input terminal for controlling picture quality in a video chroma circuit 2 rises, and picture quality is controlled sharp. In the picture signal on the white screen, the voltage for controlling picture quality drops and picture qulaity becomes soft. When the screen is bright, picture quality is set soft, whereby a blooming can be prevented, and the easy-to-see and sharp picture can be reproduced. When the screen is dark, picture quality is set sharp, whereby the easy-to-see picture can be reproduced, which can precisely be seen even if the screen is dark.
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