Fringe counting method for synthetic phase with frequency-modulated laser diodes.
Fringe counting method with laser diodes (LDs) for displacement measurement has been constructed. Two LDs are frequency modulated by mutually inverted sawtooth currents on an unbalanced two-beam interferometer. The mutually inverted sawtooth-current modulation of LDs produces interference fringe signals with opposite signs for respective wavelengths. The two fringe signals are fed to an electronic mixer to produce a synthetic fringe signal with a reduced sensitivity to the synthetic wavelength. Synthetic fringe pulses derived from the synthetic fringe signal make a fringe counting system possible for faster movement of the tested mirror.
Onodera
Ribun
R
Department of Electronics, University of Industrial Technology, 4-1-1 Hashimotodai, Sagamihara, Kanagawa 229-1196, Japan. onodera@uitec.ac.jp
Sakuyama
Munechika
M
Ishii
Yukihiro
Y