| 摘要 |
PURPOSE:To move a photographic lens to the focusing position in a very short time, by operating an evaluation value on the basis of outputs of a photodetector array, which receives a part of the object image formed on a predetermined focal plane, and a photodetecting element array which receives the same image in the focusing state. CONSTITUTION:The luminous flux from a photographic lens 21 is led to photodetecting element arrays 25 and 26 to form a blurred image corresponding to the quantity of defocus from the lens 21. The paraxial luminous flux transmitted through a semitransparent mirror 23 is made incident to a photodetecting element array 28 to focus always the almost same image in the focusing state. Exposure of photodetecting element arrays 25, 26, and 28 is started through exposure time controlling circuits 32 and 35 by a central processing unit 31, and their outputs are held in circuits 33, 34, and 36 and are subjected to A/D conversion in an A/D converter 37 and are supplied to an operating circuit 38. Differences between maximum values and minimum values out of outputs due to the converter 37 are used to obtain respective evaluation values of images projected to arrays 25, 26, and 28, and a lens movement length is obtained on the basis of these evaluation values, and these data are supplied to the device 31, and thus, the lens 21 is focused automatically by a driving circuit 39 and a driving device 40 for the lens 21. |
