Method and apparatus for detection, analysis and identification

Details Method and apparatus for detection, analysis and identification Method and apparatus for detection, analysis and identification

1994-09-01

1996-05-07

Pham, Hoa Q.

Optics: measuring and testing

By particle light scattering

With photocell detection

356339, 356369, G01N 2100

Patent

active

055151639

ABSTRACT:
A method and an apparatus for the analysis of particles contained in a material, such as particles in a fluid or on a surface, such as the surface of a semiconductor, by two orthogonally polarized, intensity and phase modulated laser beams, wherein the detected scattered light is synchronously demodulated. The apparatus comprises a laser source producing a polarized laser beam, a state of polarization modulator, and a photoreceiver for detecting light scattered by particles at an angle to the incident light. A synchronous demodulator, such as a dual channel lock-in amplifier, separates the intensity and phase modulated portions of the scattered signals. A reference unit for detecting a non-scattered light produced by the sample to provide a reference is preferably provided, as well. The size, index of refraction and identity, of the particles, for example, can be determined.

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