| 摘要 |
PURPOSE:To precisely focus a camera in a short time by weighting and adding plural HPFs different from cut-off frequencies and the outputs of the HPFs so as to detect a focusing signal. CONSTITUTION:In terms of a video signal from a buffer 12, its high frequency component is taken out by plural HPFs 231-23n, and its peak value is detected by peak holding circuits 251-25n. Then an addition coefficient device 26 multiplies the outputs of the HPFs 231-23n by a coefficient so as to add, and obtains a desired output voltage characteristic. In terms of the output of the addition coefficient device 26, sample holding circuits 271-27n sample-hold only a scan line set by a microcomputer 22 at every san line, and an adder 28 takes their sum, which is held by a sample holding circuit 29 and converted into a digital value by an AD converter 30. The microcomputer 22 controls a control circuit 21, the AD converter 30, etc., with the aid of the output signal of a field detecting circuit 18, fetches data from the AD converter 30 and focuses the camera 11. |
