A two-wavelength interferometer that uses two separate modulating currents with different phases but the same frequencies to detect a greater degree of object displacement in real time is proposed and demonstrated. The measurement error was 57 nm, roughly 1/80 of the synthetic wavelength. We have confirmed that this modulating technique enables us to equip our prototype interferometer with a simple feedback-control system that eliminates external disturbance.
© 2000 Optical Society of America
(120.3180) Instrumentation, measurement, and metrology : Interferometry
(120.5050) Instrumentation, measurement, and metrology : Phase measurement
(120.5060) Instrumentation, measurement, and metrology : Phase modulation
(140.2020) Lasers and laser optics : Diode lasers
Takamasa Suzuki, Katsuyuki Kobayashi, and Osami Sasaki, "Real-Time Displacement Measurement with a Two-Wavelength Sinusoidal Phase-Modulating Laser Diode Interferometer," Appl. Opt. 39, 2646-2652 (2000)