| 摘要 |
PURPOSE:To move a distance measuring visual field to an arbitrary position to detect the focus by using first and second focus detecting systems together. CONSTITUTION:A rectangular aperture part 3a of a visual field mask 3 is so constituted that its length in the arrangement direction of slit aperture parts 2a of a slit member 2 is about integer-number of times as long as the length of one pitch of slit aperture parts. The first focus detecting system functions when the aperture part 3a of the visual field mask 3 is placed in an arbitrary position in the effective part of a field lens 8, especially, on the outside of the optical axis and the aperture part 3a coincides with the slit aperture part 2a of the slit member 2, and the second focus detecting system functions only when an aperture part 2b of the slit member 2 and the aperture part 3a of the visual field mask 3 are placed on the optical axis of an objective lens 1. Thus, a principal object is focused in the center of a picture by the second focus detecting system, and the principal object is tracked and photographed by the first focus detecting system after framing of the principal object to an arbitrary position of the picture. |
