Measurement of the shape of objects by two wavelength interferometry

Pavel Pavlíček; Dinesh N. Naik

doi:10.1117/12.2019001

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22 June 2013 Measurement of the shape of objects by two wavelength interferometry

Pavel Pavlíček, Dinesh N. Naik

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Proceedings Volume 8769, International Conference on Optics in Precision Engineering and Nanotechnology (icOPEN2013); 87690H (2013) https://doi.org/10.1117/12.2019001
Event: International Conference on Optics in Precision Engineering and Nanotechnology (icOPEN2013), 2013, Singapore, Singapore

Abstract

We propose a fast and precise optical 3D measurement method. The principle is similar to that of white-light interferometry. The broad-band light source of white-light interferometry is replaced by two lasers with different wavelengths. The object to be measured is placed into one arm of a Michelson interferometer and moved along the optical axis. The intensity measured at the output of the interferometer is equal to the field autocorrelation. In the case of two wavelengths, the autocorrelation is a periodical function with peaks as a result of their beating. The period can be adjusted by the choice of the wavelength difference. By choosing a short period, a fast and precise measurement is performed in the range of a single beat. However, such a measurement is ambiguous if the object has structures deeper than the beat period. The ambiguity is removed by a fast auxiliary measurement with a long beat period covering the whole depth range of the object. The auxiliary measurement need not be precise and can be completed quickly with a large sampling step.

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Pavel Pavlíček and Dinesh N. Naik "Measurement of the shape of objects by two wavelength interferometry", Proc. SPIE 8769, International Conference on Optics in Precision Engineering and Nanotechnology (icOPEN2013), 87690H (22 June 2013); https://doi.org/10.1117/12.2019001

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