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Applied Optics

Applied Optics


  • Vol. 38, Iss. 13 — May. 1, 1999
  • pp: 2824–2828

Profile measurement taken with liquid-crystal gratings

Satoshi Kakunai, Tohru Sakamoto, and Koichi Iwata  »View Author Affiliations

Applied Optics, Vol. 38, Issue 13, pp. 2824-2828 (1999)

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Profile measurement taken with liquid-crystal gratings and a phase-shifting technique is proposed, and its effectiveness is verified by experiment. The surface profile is obtained by measurement of the phase distributions of the sinusoidal gratings deformed by an object’s surface. The liquid-crystal grating gives an accurate phase shift, an arbitrary projection pitch, and a constant surface brightness compared with conventional gratings such as a laser interference fringe grating and a Ronchi grating. Therefore a flexible measuring system may be developed with it. Two gratings with different pitches are used to measure an object with large steps. A two-color projection system can be used to produce such gratings simultaneously. Locally varying reflectivity on a surface can also be compensated by adjustment of the color component of the projected grating with a liquid-crystal grating. Thus the contrast in the projected grating can be made uniform, and a good profile measurement can be accomplished.

© 1999 Optical Society of America

OCIS Codes
(120.2650) Instrumentation, measurement, and metrology : Fringe analysis
(120.3940) Instrumentation, measurement, and metrology : Metrology
(120.4820) Instrumentation, measurement, and metrology : Optical systems
(120.5050) Instrumentation, measurement, and metrology : Phase measurement
(120.6650) Instrumentation, measurement, and metrology : Surface measurements, figure
(160.3710) Materials : Liquid crystals

Original Manuscript: October 12, 1998
Revised Manuscript: January 12, 1999
Published: May 1, 1999

Satoshi Kakunai, Tohru Sakamoto, and Koichi Iwata, "Profile measurement taken with liquid-crystal gratings," Appl. Opt. 38, 2824-2828 (1999)

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