Radiant energy – Photocells; circuits and apparatus – Photocell controls its own optical systems
Patent
1997-08-06
1999-03-09
Le, Que T.
Radiant energy
Photocells; circuits and apparatus
Photocell controls its own optical systems
250216, 359556, 396 82, G01J 120
Patent
active
058804552
ABSTRACT:
This invention relates to a focal position detection apparatus for detecting a positional shift between the imaging position of an object image formed by a predetermined objective optical system and the detection surface of the object image. This apparatus includes a beam splitter for extracting part of a light beam from the objective optical system, splitting the light beam into at least three light beams, and guiding the split light beams to the light-receiving surface of a photo-sensing device arranged at a predetermined position. This beam splitter guides at least the three split light beams to a standard optical path and a pair of reference optical path and forms a standard image at a predetermined position in the standard optical path and a pair of reference images at predetermined positions in the pair of optical paths, respectively. The imaging positions of the pair of reference images are shifted from each other in opposite direction with respect to the imaging surface on which the standard image is formed. The apparatus detects a positional shift by using the optically symmetry of at least one pair of reference images in a focusing state with respect to the standard image.
REFERENCES:
patent: 4831276 (1989-05-01), Hyakumura
patent: 4912496 (1990-03-01), Tamada et al.
patent: 5783818 (1998-07-01), Manabe et al.
Matsuno Jun
Otaki Tatsuro
Le Que T.
Nikon Corporation
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