Method and apparatus for inspecting foreign matter by examining

Details Method and apparatus for inspecting foreign matter by examining Method and apparatus for inspecting foreign matter by examining

1998-01-28

2000-01-25

Turner, Samuel A.

Optics: measuring and testing

By particle light scattering

With photocell detection

356351, 3562374, G01B 902

Patent

active

060183918

ABSTRACT:
A light beam from a light source is divided by a beam splitter into two branches, thereby providing a probing light having a single linear polarization and a reference light having a linear polarization which has the same polarization axis as that of the probing light. A frequency shifter which is driven in accordance with a modulation signal shifts the frequency of at least one of the probing light and the reference light. The probing light irradiates a specimen to be inspected, and the light reflected from the specimen and the reference light impinge on a photoelectric transducer to be heterodyned to provide a beat signal. A parameter representing the nature of a foreign matter is extracted from the beat signal and the reference signal used as the modulation signal, and the extracted parameter is processed to detect the presence of a foreign matter.

REFERENCES:
patent: 4842408 (1989-06-01), Yoshii et al.
patent: 5343290 (1994-08-01), Batchelder et al.
patent: 5486919 (1996-01-01), Tsuji et al.
patent: 5591985 (1997-01-01), Tsuji et al.

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