| 摘要 |
PURPOSE:To detect whether a lens is in a focused state or not, with high accuracy by a simple constitution, by placing a pair of photodetectors provided with transparent members whose optical path lengths are different from each other, on the photodetecting face, at a minute interval on both sides running along an optical path of a position which becomes conjugate with the image forming face. CONSTITUTION:On the upper and lower parts of a slightly separated opening part 4 in a position 3 being conjugate with the image forming face on an optical axis 2 of an image forming lens 1, photodetectors 6A, 6B are provided so that photodetecting faces 5A, 5B become vertical to the optical axis 2. On the reverse side of the photodetecting face, light shielding plates 7A, 7B are provided, and on the optical axis 2 in the rear of the opening part 4, a light source 8 is provided. The optical path length of the side of an object to be photographed 9, which reaches the photodetecting faces 5A, 5B becomes equal, but as for one photodetector 6A, on the front of the photodetecting face 5A, a transparent member 10 such as optical glass, etc. is stick-provided, and the optical path length of the photodetector 6A side is made a little larger. A signal is inputted to a focusing detecting circuit 12, and in case of defocusing, it is moved by a driving device 13, and in case of focusing, it is displayed by a circuit 14. |
