Automatic focusing device

Details Automatic focusing device Automatic focusing device

1985-07-03

1986-11-18

Perkey, William B.

Facsimile and static presentation processing

Facsimile

Specific signal processing circuitry

358227, G03B 300

Patent

active

046232370

ABSTRACT:
An automatic focusing device having a light projecting device, a light receiving device arranged to detect a reflection light quantity reflected by an object to be photographed as a result of light projection by the light projecting device and a distance measuring device arranged to measure a distance to the object by the reflection light quantity received by the light receiving device is capable of adequately performing a focusing operation even in cases where the reflection light quantity is at a level too low for the distance measuring device to give any result of distance measurement. This advantage is attained by the following arrangement: (i) the automatic focusing device is provided with a current control device which is arranged to increase the power of a light flux to be emitted from the light projecting device; (ii) a lens driving operation is brought to a stop in the event of an object of a low reflection factor; (iii) the light quantity accumulating time of the light receiving means can be lengthened; or (iv) a comparison level can be lowered.

REFERENCES:
patent: 3836919 (1974-09-01), Matsumoto et al.
patent: 3906389 (1975-09-01), Matsumoto et al.
patent: 4257705 (1981-03-01), Hosoe et al.
patent: 4268137 (1981-05-01), Cocron et al.
patent: 4389106 (1983-06-01), Maruyama
patent: 4429967 (1984-02-01), Tokuda et al.

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