Method and apparatus for inspecting foreign substance

Details Method and apparatus for inspecting foreign substance Method and apparatus for inspecting foreign substance

1997-12-01

2000-11-07

Rosenberger, Richard A.

Optics: measuring and testing

Inspection of flaws or impurities

Surface condition

3562398, G01N 2194

Patent

active

061444464

ABSTRACT:
An inspecting method for inspecting foreign substances, comprising projecting beams from an illumination system arranged above a light-permeable body to be inspected with an angle of incidence of a first elevation angle onto an upper face of the body, and receiving a reflecting light and a scattering light generated by the beams with a photodetecting angle of a second elevation angle by a photodetecting system. The method further comprising, before the beams are projected, setting a width of the beams of the illumination system to be not larger than w calculated according to an expression w<2* sin .alpha.*t{tan[sin.sup.-1 {sin(90.degree.-.alpha.)
}]-tan[sin.sup.-1 {sin(.theta.-90.degree.)
}]} from the angle of incidence .alpha., the photodetecting angle .theta., a thickness t of the body and a refractive index n of the body to a substance over the body.

REFERENCES:
patent: 5017798 (1991-05-01), Murakami et al.
patent: 5712701 (1998-01-01), Clementi

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