Closed-loop phase-shifting homodyne interferometry using heterodyne phase detection.
A phase-shifting homodyne interferometer with feedback control by heterodyne phase detection is developed. The backreflected beam from a reference flat with a small wedge angle and an internal heterodyne detection system are utilized to obtain heterodyne beat signals for the feedback error signal. Using a digital high-speed lock-in amplifier, interference fringe stabilization, and accurate pi/2 phase shifts when micrometer-order vibrations are applied have been successfully demonstrated with a general nonpolarizing homodyne interferometer configuration.
Bitou
Youichi
Y
National Institute of Advanced Industrial Science and Technology, AIST Tsukuba Central 3, Tsukuba, Ibaraki, Japan. y-bitou@aist.go.jp