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
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