| 摘要 |
PURPOSE:To obtain a compact focus detecting circuit which suits to a single-lens reflex camera and is free from the influence of flare and ghost due to reflection between surfaces of a photographic lens in active AF mode by forming images of entrance pupils of secondary image forming lenses for passive AF and active AF at the exit pupil position of the photographic lens. CONSTITUTION:A microcomputer 41 drives a motor 43 by a lens driving circuit 42 by processing the output of a focus detecting circuit 40, and adjusts the focus of the photographic lens 1. A light measuring circuit 45 measures the brightness of a subject and outputs a signal when the brightness is lower a constant level. When this signal is outputted to the microcomputer 41, the microcomputer 41 enters the active AF mode and makes itself ready to turn on an LED. Then when the active AF mode is entered, the microcomputer corrects focus detection by referring to information stored in a ROM 46. In this case, a stop plate 8 passes only marginal light distant from the optical axis of the photographic lens. |
