Focal point detection apparatus

Details Focal point detection apparatus Focal point detection apparatus

2005-10-17

2009-08-25

Chowdhury, Tarifur R. (Department: 2886)

Optics: measuring and testing

Focal position of light source

Reexamination Certificate

active

07580121

ABSTRACT:
A focal point detection apparatus enlarges a pull-in range of an auto-focus operation easily. The apparatus includes: illumination part illuminating an object plane via first visual field stop; first image-forming part forming an intermediate image of the first visual field stop on second visual field stop based on light from object plane, and transmitting intermediate image without blocking it with second visual field stop when object plane within a specified range contains a focused focal plane, and blocking a portion of intermediate image using second visual field stop when object plane is outside specified range, with remaining portion transmitted; second image-forming part dividing into two the final image of first visual field stop based on light from first image-forming part; and generating part detecting a gap between the divided final images and generating a focusing signal responsive to a locational relationship of object plane to focused focal plane.

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