| 摘要 |
A method and device for use in detecting a precise focussing point, which comprises the steps of: placing a photoelectric element on an optical path or optical axis of a lens of a camera; converting the information of the precise focussing point for a photographic object into a frequency variation of an A. C. signal; feeding said signal having varying frequency to a highly sensitive frequency detector such as a resonance circuit, a tuned amplifier, or frequency-amplitude convertor having acute frequency characteristics; and detecting the precise focussing point with high sensitivity by means of the output thus obtained; whereby the aforesaid functions may be satisfactorily performed, irrespective of the variation in the luminance of the object and whereby the focus of the lens may be brought into precise conformity to the predetermined plane (i.e., the position corresponding to a film). According to another aspect of the invention, there is provided an automatic focus adjusting means utilizing the differential outputs thus obtained.
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