Geometrically-desensitized interferometer incorporating an optic

Details Geometrically-desensitized interferometer incorporating an optic Geometrically-desensitized interferometer incorporating an optic

1998-10-30

2000-06-06

Kim, Robert H.

Optics: measuring and testing

By dispersed light spectroscopy

Utilizing a spectrometer

356354, 356359, G01B 902

Patent

active

060725818

ABSTRACT:
The optical assembly of a GDI instrument is configured to deviate or steer stray beams away from the pupil of the instrument's imaging device and/or to suppress stray beams. Stray beam deviation is optimized by selecting particular wedge and/or tilt configurations that achieve the desired stray beam deviation while avoiding or at least minimizing phase offset at the optimum metrology plane. Stray beam suppression can be achieved by providing the diffractive groove profile of the instrument's optical assembly with smooth edges. The resultant profile facilitates effective diffraction order management as well as a reduction in back reflection. The invention is particularly well-suited for use with a GDI instrument in which the optical assembly comprises first and second diffraction gratings. In this case, any average phase offset that remains after setting wedge and/or tilt can be eliminated by inserting a suitable compensating plate between the first and second diffraction gratings or between the second diffraction grating and the object.

REFERENCES:
patent: 3958884 (1976-05-01), Smith
patent: 4594003 (1986-06-01), Sommargren
patent: 4714348 (1987-12-01), MaKosch
patent: 5526116 (1996-06-01), de Groot
patent: 5598265 (1997-01-01), de Groot
patent: 5671050 (1997-09-01), de Groot
Grating Interferometer for Flatness Testing, Peter J. de Groot, Optics Letters, vol. 21, No. 3, Feb. 1996.

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