| 摘要 |
PURPOSE:To let the focus controlling by the change of the contrast of an image be accurately done by one lens system by vibrating the focus position detecting element comprising constituting two sets of photodetecting part groups in grating form on the same substrate by a vibrating device. CONSTITUTION:If an image having random illuminance distributions is projected to a focus position detecting element 1 by way of a lens and the element 1 is vibrated by a vibrating device 3 and if the lens is moved from e.g. infinity toward the short distance direction at this same instant, the illuminance distributions for respective photodetecting parts 61-62n change periodically depending upon the position of the element 1 and the photocurrent corresponding to this is output from the electrodes 7 and 8. The changes in this photocurrent are detected respectively by the photodetecting part groups of the odd number place and even number place and the outputs thereof are detected by a differential amplifier 12, by which only the change components of the contrast of the image are fetched and the peak values thereof are detected with a peak value detecting circuit 13. Further, in a peak value is detected, whereby the focus positions is detected. |
