Focus detecting optical system

Details Focus detecting optical system Focus detecting optical system

1989-06-19

1990-03-13

Nelms, David C.

Radiant energy

Photocells; circuits and apparatus

Photocell controls its own optical systems

354408, G01J 120

Patent

active

049085042

ABSTRACT:
A focus detecting optical system is disclosed which includes an objective lens for forming an image of an object, a plurality of focus detecting blocks, and a focus condition calculating device for calculating a focus condition of the objective lens in accordance with the light intensity distribution signals produced by the plurality of the focus detecting blocks. Each of the focus detecting blocks includes a condenser lens located nearby a predetermined focal plane of the objective lens, a pair of image re-forming lenses located behind the condenser lens for reforming a pair of secondary images of the image formed by the objective lens, a mask plate having a pair of apertures through which light fluxes forming the secondary images pass and a light receiving unit for receiving the pair of the secondary images formed by the pair of image re-forming lenses to produce a light intensity distribution signal representative of the light intensity distribution of the secondary images. The apertures in the mask plate of at least one specified focus detecting block has a configuration different from that of the other focus detecting blocks.

REFERENCES:
patent: 4370551 (1983-01-01), Fukuhara et al.
patent: 4766302 (1988-08-01), Ishida et al.
patent: 4774539 (1988-09-01), Suda et al.
patent: 4808808 (1989-02-01), Karasaki et al.

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