Automatic focus adjusting device

Details Automatic focus adjusting device Automatic focus adjusting device

1978-07-18

1980-03-04

Nelms, David C.

Radiant energy

Photocells; circuits and apparatus

Photocell controls its own optical systems

250204, 354 25, G03B 310

Patent

active

041918827

ABSTRACT:
An automatic focus adjusting device for use with an optical instrument hag a focusable objective lens which is adjusted by optical and electronic components of the instrument, such components determining the distance of an object by comparing images of separate scanning and reference optical systems. The device of the present invention has a low-reduction filter screen placed across part of each light path of the two optical systems. The filters provide an overriding apparent contrast to low-contrast object fields to cause the system to adopt a pre-set focus distance, but do not interfere with normal automatic focusing where object field contrast is adequate for normal system operation. Manual adjustment of the filter spacing varies the pre-set, low-contrast focus to any desired object distance setting. Five to ten percent light reduction in the screened part of each filter is adequate.

REFERENCES:
patent: 4156563 (1979-05-01), Kato et al.

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