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Proceedings Paper

Multipoint gap measurement by low coherence tandem interferometry
Author(s): Sheng-Hua Lu; Chi-Ying Chang; Ching-Fen Kao
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Paper Abstract

Gap uniformity between two plates is an important parameter in many optical devices or instruments. The proposed method combines low coherence tandem interferometry and the concept of distributed fiber sensors for in-situ multipoint gap measurement. No gratins or special marks are required on the surfaces of the plates. A superluminescent diode (SLD) is used as the light source because of its low temporal coherence, high spatial coherence, and high optical power. Therefore, the proposed technique can also be easily implemented in free space. A collimated light beam from the SLD first passes through a scanning Michelson interferometer. The output of the interferometer is split into several separate beams, and then each beam is normally incident to the test sample at different positions. Gap distribution measurement is performed by sequentially opening the shutter behind each incident beam. A detector is employed to receive the reflected lights from the sample. The interferometric signal is recorded as a function of the arm-length difference of the scanning interferometer. The gap is eventually derived from the separation of the two side fringe packets, whose peak positions are determined by the centroid algorithm. Preliminary experimental results validate the feasibility of the presented method.

Paper Details

Date Published: 2 August 2010
PDF: 6 pages
Proc. SPIE 7791, Interferometry XV: Applications, 77910L (2 August 2010); doi: 10.1117/12.858851
Show Author Affiliations
Sheng-Hua Lu, Feng Chia Univ. (Taiwan)
Chi-Ying Chang, Feng Chia Univ. (Taiwan)
Ching-Fen Kao, MingDao Univ. (Taiwan)

Published in SPIE Proceedings Vol. 7791:
Interferometry XV: Applications
Cosme Furlong; Christophe Gorecki; Erik L. Novak, Editor(s)

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