Sinusoidal phase modulating interferometer using optical fibers for displacement measurement.

We propose a sinusoidal phase modulating (SPM) interferometer for displacement measurement. The displacement is obtained by processing the detected signal with a microcomputer. The optical configuration of the SPM interferometer is simple because an optical fiber is effectively used to produce sinusoidal phase modulation. The movements of a piezoelectric transducer and the surface profile of a diamond-turned aluminum disk are measured with high accuracy (a few nanometers).