Method and apparatus for determination of geometric values...

Details Method and apparatus for determination of geometric values... Method and apparatus for determination of geometric values...

2006-11-08

2011-11-01

Lee, Hwa (Department: 2886)

Optics: measuring and testing

By light interference

For dimensional measurement

Reexamination Certificate

active

08049899

ABSTRACT:
A Michelson-interferometer which has two reference arms and a short coherence length is used for the method and apparatus for measurement of geometric values on transparent or diffuse objects (19). The basic optical delay times of the reference arms (11, 12) are chosen in such a manner that they result in an optical delay time difference corresponding to a layer thickness, as a geometric value. The at least two reference arm beams (33a, 35a) are passed to a single rotating path-length variation element (23), with a mutual spatial offset angle (dw). A delay-time change, which is dependent on the rotation angle, of the reference arm beams is produced as a function of a rotation angle caused by rotation, in order to allow a delay-time change caused by the path-length variation element (23) to be applied successively to the basic optical delay times in the reference arms (11, 12). A topography as a further geometric value is obtained by projection of a light-intensity structure onto a surface to be measured, and by measurement of its image.

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