| 摘要 |
In an image pick-up device including an image forming lens, a focal condition of the image forming lens is detected by means of a focus detecting optical system including a condenser lens arranged near a predetermined focal plane of the image forming lens, a plurality of aperture stops which divides a light flux emanating from an object into a plurality of light fluxes, a plurality of image reforming lenses each corresponding to respective aperture stops and a plurality of light receiving element arrays each corresponding to respective image reforming lenses. Output characteristics of the light receiving element arrays are are expressed as three dimensional information, while an image position is expressed on X axis, a pupil position through which a light flux is transmitted is expressed on Y axis, and an intensity of light is expressed on Z axis. The three dimensional image is distorted on X-Z plane in accordance with defocus. A direction and an amount of defocus can be detected by detecting a direction and an amount of the distortion. The output characteristics of the light receiving element arrays are subjected to shift and sum operations to derive distributions of light intensity of parallax image summation. Then, operation for deriving a contrast is performed and a direction and an amount defocus are detected.
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