Foreign substance inspecting apparatus

Optics: measuring and testing – Inspection of flaws or impurities – Having predetermined light transmission regions

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Details

356239, 250563, 250572, G01N 2188

Patent

active

046105417

ABSTRACT:
An inspecting apparatus for precisely detecting foreign substances or scars present on a translucent planar article such as a photomask at a high speed with a laser beam entering from face of the article, comprises first photoelectric means for receiving the scattered light generated in a space on a face of the photomask, second photoelectric means for receiving the scattered light generated in a space on the other face of the photomask, comparator means for comparing the photoelectrically converted signals from the first and second photoelectric means to identify one of predetermined plural magnitude relationships to which the magnitudes of the signals belong, and inspecting means for generating, in response to the detection output signal of the comparator means, a detection signal allowing to identify the approximate difference in the shape of the foreign substance, for example either a tall foreign substance or a short one.

REFERENCES:
patent: 3814946 (1974-06-01), Takahashi et al.
patent: 3984189 (1976-10-01), Seki et al.
patent: 4173441 (1979-11-01), Wolf
patent: 4342515 (1982-08-01), Akiba et al.
patent: 4468120 (1984-08-01), Tanimoto et al.

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