Radiant energy – Photocells; circuits and apparatus – Photocell controls its own optical systems
Patent
1994-02-25
1995-11-28
Westin, Edward P.
Radiant energy
Photocells; circuits and apparatus
Photocell controls its own optical systems
2502014, 354409, 354406, G03B 1336
Patent
active
054710464
ABSTRACT:
Apparatus for use with an imaging optical system, to indicate both the direction and magnitude of focus adjustment, includes a diffractive optical element exposed to a broad spectrum of radiation. The element filters out a narrow spectrum of the radiation and directs it into a path centered on detectors in a circuit that indicates the required focus adjustment. According to one feature of the invention, two detectors are used, and the focusing adjustment signal is determined by the difference in signal between the two detectors, eliminating absolute intensity and reflectivity from the focusing determination. Still another feature employs a holographic diffractive element transparent to most of the broad spectrum, but reflective in a narrow spectrum corresponding to detector sensitivity. This permits positioning of the holographic element between the optical system and its focal plane without significantly degrading the focused image. The focusing element can remain in position during imaging. The invention has particular utility when used in a camera having a visible designator.
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Eastman Kodak Company
Howley David A.
Lee John R.
Westin Edward P.
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