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Applied Optics

Applied Optics


  • Vol. 39, Iss. 16 — Jun. 1, 2000
  • pp: 2569–2576

Edge location by use of optical phase variation

Weidong Zhou and Lilong Cai  »View Author Affiliations

Applied Optics, Vol. 39, Issue 16, pp. 2569-2576 (2000)

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Traditional optical methods for locating an edge are based on light intensity variation with respect to a reference triggering level. Since the intensity variation is subject to stray light, the intensity variation of the light source, and the triggering level variation, the exact position of the edge cannot be determined. We describe a method for edge location that uses a phase variation in a modified differential interferometer. The maximal point of the slope of the phase variation across an edge is determined exactly by the relative position between the focused beam spot and the detected edge if the initial intensity ratio of the two single-frequency interference beams is kept unchanged. Therefore the phase variation can be used to locate the edge with high resolution and accuracy. To make practical use of the phase variation, the second derivative of the phase was used as a monotonic zero-crossing signal across the edge. The theoretical and the experimental verification have been conducted in detail. The results of the experiment show the feasibility of edge location when phase variation is used. The scheme is not affected by stray light and the intensity variation of the light source.

© 2000 Optical Society of America

OCIS Codes
(120.3180) Instrumentation, measurement, and metrology : Interferometry
(120.3940) Instrumentation, measurement, and metrology : Metrology
(120.5060) Instrumentation, measurement, and metrology : Phase modulation
(180.3170) Microscopy : Interference microscopy
(260.3160) Physical optics : Interference
(260.5430) Physical optics : Polarization

Original Manuscript: July 1, 1999
Revised Manuscript: December 21, 1999
Published: June 1, 2000

Weidong Zhou and Lilong Cai, "Edge location by use of optical phase variation," Appl. Opt. 39, 2569-2576 (2000)

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