| 摘要 |
PURPOSE:To synthesize an easy-to-see picture by comparing an analog image signal with a prescribed level, generating binary information in accordance with the magnitude and controlling a polarity at the time of synthesizing a digital video signal into an analog image signal by said bonary information. CONSTITUTION:An image signal 1000 is supplied to a comparator circuit 1 and compared with a reference voltage VS from a reference voltage circuit. The comparator circuit 1 is constituted of an operational amplifier 1000', and a reference voltage circuit 2 is constituted of a constant-voltage Zener diode 21 and resistance 22. The sgnal 1000 is compared with the reference voltage VS from the diode 21 by the amplifier 1000'. Binary information instructing that an output 1001 of the comparator 1 is set to high level if an instantaneous voltage of the signal 1000 at the point is higher than the voltage VS, and if the former is lower than the latter, the output 1001 of the comparator 1 is set to a low level, is supplied to a synthesization control circuit 3. When digital video signal 3000 is synthesized with the signal 1000 by the binary information, a picture with a controlled polarity can be obtained on a CRT4. |
