| 摘要 |
A photographic copying apparatus wherein a composite mask is installed between the plane of photographic paper and a variable-focus optical unit which images a light source or an original into the plane of photographic paper. The movable sections of the mask carry pairs of photodiodes. A control unit adjusts the optical unit when the latter projects light onto both photodiodes of each pair in a direction to reduce the projected image and in the opposite direction when none of the photodiodes are illuminated. The adjustment is terminated when the size of the projected image is such that only one diode of each pair is illuminated.
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