A novel method is presented for of measuring absolute displacement with a synthesized wavelength interferometer. The optical phase of the interferometer is simultaneously modulated with a frequency-modulated laser diode and optical path-length difference. The error signal originating from the intensity modulation of the source is eliminated by a signal processing circuit. In addition, a lock-in technique is used to demodulate the envelope of the interferometric signal. The displacement signal is derived by the self-mixing technique.
© 1999 Optical Society of America
Lih-Wuu Chang, Pie-Yau Chien, and Ching-Ting Lee, "Measurement of Absolute Displacement by a Double-Modulation Technique Based on a Michelson Interferometer," Appl. Opt. 38, 2843-2847 (1999)