| 摘要 |
PURPOSE:To set up the size of a sampling ares to prevent the peak level of an integrated value from sharp variation by deciding the integrated output value, and expanding or contracting the sampling area to adjust the number of sampling data. CONSTITUTION:A focus control circuit in a video camera consists of an A/D converter 3 for digitizing the change of video signal in a sampling area of an image pickup screen, an arithmetic circuit 25 for integrating the output of the conveter 3 and a motor control circuit 29 for controlling the revolution of a focus ring so that the integrated output is maximized. When the operated output exceeds a prescribed range, a decision circuit 30 generates the 1st output O1, and when the output drops from the prescribed range, generates the 2nd output O2. The 1st and 2nd pulse generating circuits 31, 32 inputs (n) and (m) addition/ subtraction pulses to the 3rd and 4th counters 8, 9 respectively to change the sampling area. Therefore, subtraction pulses are generated at the generation of the output O1 to contract the sampling area, and the reverse is formed at the generation of the output O2. |
