Optics: measuring and testing – By alignment in lateral direction
Patent
1997-09-25
1999-05-11
Kim, Robert
Optics: measuring and testing
By alignment in lateral direction
356400, 250548, G01B9/02
Patent
active
059033568
ABSTRACT:
Illuminating light at a pupil plane of an illumination optical system for illuminating a position detection mark on a substrate is limited to an annular area centered at an optical axis, and a member substantially blocks an image-forming light beam distributed over an area on a pupil plane of an image-forming optical system for forming an image of the position detection mark on an imaging device by receiving light generated from the mark, the area being in image-forming relation to the annular area on the pupil plane of the illumination optical system. Alternatively, the image-forming light beam distributed over the area which is in image-forming relation to the annular area on the pupil plane of the illumination optical system and the image-forming light beam distributed over the area other than that area. The outer radius r.sub.o and inner radius r.sub.i of the annular area on the pupil plane of the illumination optical system are determined so as to satisfy the following conditions: ##EQU1## where .lambda.1 is the shortest wavelength in the wave band of illuminating light contributing to the formation of an image signal, .lambda.2 is the longest wavelength in the wave band, and P is the period of the position detection mark.
REFERENCES:
patent: 5140366 (1992-08-01), Shiozawa et al.
Kim Robert
Lee Andrew H.
Nikon Corporation
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