Superposition fringes for profiling applications

J. Schwider

doi:10.1117/12.725038

18 June 2007 Superposition fringes for profiling applications

J. Schwider

Proceedings Volume 6616, Optical Measurement Systems for Industrial Inspection V; 661627 (2007) https://doi.org/10.1117/12.725038
Event: Optical Metrology, 2007, Munich, Germany

Abstract

Interferometric profilometers make use of two-beam interferometers with spectral broad band or more general polychromatic illumination either simultaneously or successively on the time axis. Since the criterion for a position of an object point on the z-axis is commonly the condition OPD = 0, the two-beam interferometer should allow for such an adjustment being a typical feature of Michelson- or Mirau-type instruments. However, the very simple Fizeau interferometer does not allow for this adjustment since it is a real wedge instrument. But it is well known that the superposition fringes between two interferometers in a series arrangement enable such an adjustment. In case of two two-beam interferometers in series arrangement a loss in contrast by a factor of at least 2 has to be tolerated. The combination of a multi-beam interferometer as a Fabry-Perot resonator with a Fizeau interferometer will deliver a fringe pattern which has a contrast of R^m where R is the reflectivity of the Fabry-Perot(FP)-plates and m is the ratio of the resonator lengths of the two interferometers in series. The disadvantage of the FP-solution is an intensity loss of the order (1-R)². Here the occurrence of bright broad-band sources with transversal mono-mode character as superlum-diodes or fs-lasers opens up new perspectives. Fine tuning could be obtained either by mirror shifts or tilt of a FP-etalon.

Citation Download Citation

J. Schwider "Superposition fringes for profiling applications", Proc. SPIE 6616, Optical Measurement Systems for Industrial Inspection V, 661627 (18 June 2007); https://doi.org/10.1117/12.725038

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