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Proceedings Paper

Improved second-harmonic two-wavelength interferometer with refractive index correction without effect modulation
Author(s): Bernd Bodermann; Jens Flugge; Karl Meiners-Hagen
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Paper Abstract

Refractive index fluctuations due to changing environmental conditions or due to air turbulence can significantly influence the measurement uncertainty of interferometric length measurements in air ambiance. A two wavelength interferometer is to some extend capable of measuring synchronously a path difference and the integral refractive index along this path difference. The best performance is achieved using two harmonically correlated optical fields like in a second harmonic interferometer. We developed a new type of a second harmonic two wavelength interferometer based on a double heterodyne interferometer with electronic frequency multiplication of one heterodyne frequency. The optical setup of the interferometer uses a measurement and a reference interferometer, both with spatially separated measurement and reference beam to avoid optical nonlinearities and reduce the influence of mechanical vibrations. The phase difference between measurement and reference interferometer is kept constant which reduces possible nonlinearities of the phase analysis. The system is capable of measuring the integral index of refraction without any effect modulation like e.g. a variation of the path difference which makes the design also applicable for absolute measuring interferometry. First experimental results will be presented

Paper Details

Date Published: 20 November 2003
PDF: 8 pages
Proc. SPIE 5190, Recent Developments in Traceable Dimensional Measurements II, (20 November 2003); doi: 10.1117/12.509868
Show Author Affiliations
Bernd Bodermann, Physikalisch-Technische Bundesanstalt (Germany)
Jens Flugge, Physikalisch-Technische Bundesanstalt (Germany)
Karl Meiners-Hagen, Physikalisch-Technische Bundesanstalt (Germany)

Published in SPIE Proceedings Vol. 5190:
Recent Developments in Traceable Dimensional Measurements II
Jennifer E. Decker; Nicholas Brown, Editor(s)

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