| 摘要 |
<p>PURPOSE:To improve resolution in the digitization of a video signal, by setting a voltage at a value corresponding to the maximum and the minimum values of the video signal in the periods of a burst signal and the video signal, and setting the voltage at the value corresponding to the maximum and the minimum values of a color video signal in the period of a synchronizing signal. CONSTITUTION:The video signal inputted from an input terminal l is A/D-converted at an A/D converter 2, then being inputted to a synchronizing signal detection circuit 3. At such a time, the voltage of VRT-VRB1 is impressed from a synchronizing signal period reference voltage generation circuit 5 as the reference voltages 100A and 100B of the A/D converter 2. The circuit 5 is separated from the converter 2 at the completing time of the synchronizing signal, and a burst signal/ video signal period reference voltage generation circuit 6 is connected to the converter 2, and the reference voltages 100A and 100B are switched to a VRT-VRB2. At the completing time of the video signal period, the reference voltages 100a and 100B are switched again to the VRT-VRB1. Hereinafter, the same operation is repeated. Thus, since thc reference voltage of the A/D converter 2 becomes a difference between the maximum value and the minimum value, the resolution of the A/D converter can be utilized over all area.</p> |
