| 摘要 |
PURPOSE:To detect a body securely in a broad region by picking up an image of a monitoring area through an image pickup tube, then stores and delayes a video signal detected by a scan on the tube surface, and by comparing its level with the level of a following video signal at the same scanning position. CONSTITUTION:Every time a clock pulse (a) is supplied, a binary counter 2 counts up and a D/A converter 3 converts its discrete value into an analog signal successively to generate a saw tooth wave (b) for a horizontal sweep off of 256-stage. Simultaneously, a D/A converter 7 generates a saw tooth wave (d) for a vertical sweep off of a step level which corresponds to the discrete value of the binary counter 6, and a raster scan on a vidicon 1 is taken while horizontal scanning lines driven in 256 stages are successively shifted vertically by four. Then, the result is stored in a storing circuit 12 and a subtracting circuit 16 compares a video signal at an actual time with that preceding it by one scanning period at every scanning point to detect a moving body. |
