Uncertainty analysis on the absolute thickness of a cavity using acommercial wavelength scanning interferometer

摘要

Wavelength scanning interferometry offers many advantages over traditional phase shifting interferometry, mostsignificantly the elimination of mechanical movement of the part/s for phase modulation by implementing a tunable lightsource. Further, Fourier analysis on the interference time history enables this technique to accurately measure distances,treating the distance between two optical surfaces as an interferometric cavity. We propose to evaluate the uncertainty inthe thickness measurement of a transparent cavity using a commercial Fizeau wavelength scanning interferometer. Thiswork follows the theory and measurement performed in a previous manuscript of measuring absolute distances ofopaque objects using a commercial wavelength scanning interferometer. The limits in measuring a cavity using thecommercial wavelength scanning interferometer depend on many factors such as temperature variations that affect thetest and reference cavity, uncertainty in the reference cavity calibration, tuning rate non-linearities, etc. In addition to ananalytical approach, a simulation is described to better understand the measurement process and the uncertaintyassociated in measuring absolute distances (thickness) of cavities. Preliminary experimental results on the absolutethickness of a transparent cavity are reported along with uncertainty sources.