A simple and robust interferometer with a laser diode subject to optical feedback from the interferometer is presented for surface testing of a spherical mirror. The fringe phase can be locked by the optical feedback within less than 0.2π (peak-to-valley value) even when the interferometer is placed on a wooden table. The fringe locking is caused by the change of lasing wavelength that suppresses the net phase change to be much less than 2π. The locked fringe pattern with spatial carriers can be analyzed by a fringe analyzer at a video rate, and the measurement results of the spherical mirror showed the same result as on an optical bench.
[Optical Society of America ]
(120.3180) Instrumentation, measurement, and metrology : Interferometry
(120.6660) Instrumentation, measurement, and metrology : Surface measurements, roughness
(140.2020) Lasers and laser optics : Diode lasers
Jiyuan Liu and Ichirou Yamaguchi, "Surface profilometry with laser-diode optical feedback interferometer outside optical benches," Appl. Opt. 39, 104-107 (2000)