| 摘要 |
PURPOSE:To adjust quickly focus of a camera, by receiving a focusing signal indicating the focus of an object or a distance signal corresponding to the distance to change the length of the optical path between a photographic lens and the focus position. CONSTITUTION:The image of an object 5 is focused onto an image pickup face 4 through a lens 20, an aperture 21, and a visible rays-transmissive plate 22. The photographic distance is divided to serveral zones, and stepped faces different in thickness whose number corresponds to the number of these zones are formed on the transmissive plate 22. When the distance to an object 5 is changed, the focus position of an optical beam on the surface of a photodetector 19 is moved. An operating circuit 23 calculates the distance to the object on a basis of a ratio of photocurrent signals I1 and I2 and outputs it as a distance signal D. The visible rays-transmissive plate driving device 24 receives this signal D and drives the visible rays-transmissive plate 22 vertically to change in thickness and performs such regulation that the image of the object 5 is focused onto the image pickup face 4 most suitably. |
