To stabilize the phase-shifting Fizeau-type interferometer against environmental disturbances (namely, vibration and temperature variations), the feedback scheme that uses the current-induced frequency modulation of a laser diode (λ = 633 nm) and the two-frequency optical heterodyne method has been investigated, with particular attention to improvement of the achievable stabilization. It is demonstrated that introduction of the proportional-integral control into the feedback system improves stabilization against the proportional control case; e.g., stabilization is improved 5 times for 100-nm<sub>p−p</sub> vibration at the frequency range at 30 Hz. The surface profile measurement for a sample mirror was conducted with a reproducibility of 6.8 nm in the root mean square under the subwavelength-amplitude vibration at 100 Hz.
© 2003 Optical Society of America
(100.2650) Image processing : Fringe analysis
(120.3180) Instrumentation, measurement, and metrology : Interferometry
(120.6660) Instrumentation, measurement, and metrology : Surface measurements, roughness
(260.3160) Physical optics : Interference
Masayuki Yokota, Atsuyoshi Asaka, and Toshihiko Yoshino, "Stabilization Improvements of Laser-Diode Closed-Loop Heterodyne Phase-Shifting Interferometer for Surface Profile Measurement," Appl. Opt. 42, 1805-1808 (2003)