| 摘要 |
PURPOSE:To detect a focus of an optical image whose main body is a low frequency component, and to prevent generation of a pseudo focusing signal in a place where a shift is large, by setting a composite MTF of an MTF characteristic of a filter and an MTF characteristic by a shape of a photodetecting part, to a specified value. CONSTITUTION:A series of photoelectric outputs of image sensors 22A, 22B are sent to corresponding filters 26A, 26B, respectively, and sample holding circuits 27A, 27B sample-hold successively their added outputs I1, I2, I3..., respectively. An operator 28 detects a displacement of an optical image. An MTF characteristic of the first and the second filters 26A, 26B is synthesized with an MTF characteristic X0 determined by a shape of the photodetecting part, a composite MTF characteristic has one peak Ap between frequency zero, namely a DC component and a Nyquist frequency fN=1/2p as shown by a full line Y0, and also an extraction efficiency Ao of the DC component satisfies 0.1Ap<Ao<0.8Ap. According to such a constitution, an influence of various error factors is avoided, no false focusing is generated in a defocused place, a detecting accuracy at a true focused position is raised, and a focus can be detected with respect to an optical iamge whose main body is a low frequency component, as well. |
