Surface characteristic determining apparatus

Details Surface characteristic determining apparatus Surface characteristic determining apparatus

2007-06-14

2011-12-13

Lee, Hwa (Department: 2886)

Optics: measuring and testing

By light interference

For dimensional measurement

C356S521000

Reexamination Certificate

active

08077324

ABSTRACT:
Light from the first and second different wavelength light sources is combined and supplied to a director that directs zeroth order light to a reference surface and other order, generally first order diffracted light to on a location of the sample surface which is dependent upon wavelength. Light reflected by the sample and reference surfaces interfere. A characteristic of a sample surface is determined from interference light of the first wavelength. Interference light of the second wavelength is used to enable phase-locking by adjusting the path length difference by moving the reference surface or changing the refractive index of a path portion to compensate for phase variation due to environmental effects. Non-mechanical scanning is used to scan the sample surface by using a variable wavelength source and a director providing different first order diffraction angles for different wavelengths or an acousto-optical device that provides a variable pitch acoustic diffraction grating.

REFERENCES:
patent: 5694216 (1997-12-01), Riza
patent: 2005/0083534 (2005-04-01), Riza et al.
patent: WO 92/19930 (1992-11-01), None
International Search Report dated Nov. 7, 2007, International Application No. PCT/GB2007/002249, filed Jun. 14, 2007.

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