The operating characteristics of a novel phase-shifting interferometer are presented. Interference arises by reflecting the light from a sample back into the cavity of a cw He–Ne laser. Changes in phase and fringe visibility are calculated from an overdetermined set of phase-shifted intensity measurements with the phase shifts being introduced with an electro-optic modulator. The interferometer is sensitive enough to measure displacements below 1 Hz with a rms error of approximately 1 nm from a sample that reflects only 3% of the 28 μW that is incident on its surface. The interferometer is applied to the determination of cantilever bending of a piezoelectric bimorph.
© 1999 Optical Society of America
(110.0180) Imaging systems : Microscopy
(110.6880) Imaging systems : Three-dimensional image acquisition
(120.3180) Instrumentation, measurement, and metrology : Interferometry
(120.5050) Instrumentation, measurement, and metrology : Phase measurement
(180.3170) Microscopy : Interference microscopy
Ben Ovryn and James H. Andrews, "Measurement of Changes in Optical Path Length and Reflectivity with Phase-Shifting Laser Feedback Interferometry," Appl. Opt. 38, 1959-1967 (1999)