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Optics Express

Optics Express

  • Editor: C. Martijn de Sterke
  • Vol. 16, Iss. 8 — Apr. 14, 2008
  • pp: 5516–5526

Simultaneous measurement of refractive index and thickness by combining low-coherence interferometry and confocal optics

Seokhan Kim, Jihoon Na, Myoung Jin Kim, and Byeong Ha Lee  »View Author Affiliations

Optics Express, Vol. 16, Issue 8, pp. 5516-5526 (2008)

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We propose and demonstrate novel methods that enable simultaneous measurements of the phase index, the group index, and the geometrical thickness of an optically transparent object by combining optical low-coherence interferometer and confocal optics. The lowcoherence interferometer gives information relating the group index with the thickness, while the confocal optics allows access to the phase index related with the thickness of the sample. To relate these, two novel methods were devised. In the first method, the dispersion-induced broadening of the low-coherence envelop signal was utilized, and in the second method the frequency derivative of the phase index was directly obtained by taking the confocal measurements at several wavelengths. The measurements were made with eight different samples; B270, CaF2, two of BK7, two of fused silica, cover glass, and cigarette cover film. The average measurement errors of the first and the second methods were 0.123 % and 0.061 % in the geometrical thickness, 0.133 % and 0.066 % in the phase index, and 0.106 % and 0.057 % in the group index, respectively.

© 2008 Optical Society of America

OCIS Codes
(030.1640) Coherence and statistical optics : Coherence
(120.3180) Instrumentation, measurement, and metrology : Interferometry
(120.5710) Instrumentation, measurement, and metrology : Refraction
(180.1790) Microscopy : Confocal microscopy
(260.2030) Physical optics : Dispersion

ToC Category:
Instrumentation, Measurement, and Metrology

Original Manuscript: January 29, 2008
Revised Manuscript: March 12, 2008
Manuscript Accepted: March 28, 2008
Published: April 4, 2008

Virtual Issues
Vol. 3, Iss. 5 Virtual Journal for Biomedical Optics

Seokhan Kim, Jihoon Na, Myoung Jin Kim, and Byeong Ha Lee, "Simultaneous measurement of refractive index and thickness by combining low-coherence interferometry and confocal optics," Opt. Express 16, 5516-5526 (2008)

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