| 摘要 |
Disclosed is an optical sensing system for use in focusing the objective of a reflex camera in which light from the exit pupil of the camera objective is projected onto a pair of spaced sensors such that each sensor receives light from a different portion of the exit pupil. Each sensor thus generates a signal which is a function of the light projected from its respective region of the exit pupil, the relative equality of which gives an indication of the correctness of the focus. This feature is achieved by positioning a fully reflecting projection mirror on the back side of a reflex mirror which is positioned behind the camera objective at an angle thereto and has a central region of partial reflectivity. The projection mirror projects the exit pupil of the objective onto an auxiliary plane, located above the reflecting surface of the reflecting mirror when the sensing system is in its normal viewing position, in which two auxiliary objectives are arranged side-by-side, each of which projects light from a different section of the exit pupil onto different sensors.
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