| 摘要 |
PURPOSE:To improve the precision of automatic focusing by providing a projection optical system or photodetection optical system with a neutral density (ND) filter which is associated operatively with a focusing drive member for a photographic lens. CONSTITUTION:Light for automatic focusing from a light source 1 is passed through a projection lens 2, guided to the photographic lens in a focus ring 5 by mirrors 3 and 4, and projected on a subject S. Reflected light from the subject S is passed through a photodetection lens 6 and transmitted through the ND filter 7 to reach a photodetecting element 8. The photodetecting element 8 consists of two upper and lower elements and is slanted by a cam together with the photodetection lens 6 according to the rotation of the focus ring 5. Then, a focusing state is obtained while the focus ring 5 slants the elements so that their output difference is zero. |
