Optics: measuring and testing – Inspection of flaws or impurities – Transparent or translucent material
Patent
1983-12-12
1986-05-13
Kittle, John E.
Optics: measuring and testing
Inspection of flaws or impurities
Transparent or translucent material
356 71, G06K 908, G01N 2116
Patent
active
045882932
ABSTRACT:
The present invention is directed to an improved method and apparatus for detecting defects in photomasks containing features with different arbitrary orientations, said apparatus including in one form therof a detector for detecting orientations of the features so that the optical signals from the features may be suppressed by suitable apparatus such as spatial filtering. The spatial filtering is adjusted electronically based on the determined orientation of the mask features. In one form of the invention the spatial filtering is effected by accepting photodetected signals from only a selected number of photodetectors in a photodetector array, the selection being determined by the orientation of the mask features.
REFERENCES:
patent: 3658420 (1972-04-01), Axelrod
patent: 3738752 (1973-06-01), Heinz et al.
patent: 3743423 (1973-07-01), Heinz et al.
patent: 4377324 (1983-03-01), Durand et al.
"Spatial Filtering for Detection of Signals Submerged in Noise" by Kozma et al. Apr. 1985, vol. 4, No. 4, Applied Optics, pp. 387-392.
"Computor Generated Spatial Filters for Coherent Optical Data Processing" by Lohmann et al, Apr. 1968, vol. 7, No. 4, Applied Optics, pp. 651-655.
Grimes Edwin T.
Kittle John E.
Murphy Thomas P.
The Perkin-Elmer Corporation
Wilder Richard C.
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