Focus detecting device

Radiant energy – Ionic separation or analysis – Static field-type ion path-bending selecting means

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Details

2502018, G03B 1336, G02B 728, G01J 120

Patent

active

052298078

ABSTRACT:
A focus detecting device which comprises an objective lens for forming an image of an object, a condenser lens, located behind a predetermined focal plane of the objective lens, for converging the light passed through the objective lens, a pair of image re-forming lenses, located behind the condenser lens, for re-forming a pair of secondary images of the image formed by the objective lens on an off-axial region of the objective lens located at a position far from the optical axis thereof, a light direction changing device, located nearby the condenser lens, for changing the direction along which light bundles forming the secondary images passes towards the optical axis, and a light receiving device for receiving the pair of the secondary images formed by the secondary image forming device to produce a light intensity distribution signal representing the light intensity distribution of the secondary images, a focus condition calculating device for calculating a focus condition of the objective lens by means of detecting the positions of the pair of the secondary images in accordance with the light intensity distribution signal.

REFERENCES:
patent: 4857718 (1989-08-01), Karasaki et al.
patent: 4949116 (1990-08-01), Karasaki et al.
patent: 4978988 (1990-12-01), Karasaki
patent: 4992818 (1991-02-01), Karasaki et al.
patent: 5005041 (1991-04-01), Suda et al.
patent: 5017005 (1991-05-01), Shindo

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