| 摘要 |
PURPOSE:To perform a high-precision focus detection with a simple constitution, by dividing the optical axis into plural zones and measuring the luminance of each zone by a photodetecting means and defining the zone, where the difference between the output of the corresponding photodetecting means and the output of a reference photodetecting means on the optical axis is smallest, as a focus position. CONSTITUTION:The output of a reference photodetecting means, which consists of a lens L0 having an optical axis coincident with the photographic optical axis and a photodetector P0 for measuring the luminance of an object to be photographed image formed by the lens L0, and outputs of auxiliary photodetecting means, which consists of lenses L1-L4 which have optical axes coincident with the photographic optical axis and are arranged prescribed length distant from the lens L0 and photodetectors P1-P4 for measuring the luminance of the object to be photographed due to these lenses are inputted to comparing circuits 11-14 through preamplifiers 1-5, and outputs of auxiliary photodetectors P1-P4 are compared with the output of the reference photodetector P0. The smallest one of difference outputs V1-V4 is detected to detect a focus zone. Since the device is not affected by the fluctuation of the illumination light, a high- precision focus detection is possible with a simple constitution. |
