WAVELENGTH-SHIFT INTERFEROMETRY FOR DISTANCE MEASUREMENTS USING THE FOURIER-TRANSFORM TECHNIQUE FOR FRINGE ANALYSIS

The Fourier transform technique, originally developed for spatial fringe pattern analysis, has been applied to the analysis of a temporal fringe signal obtained by a wavelength-shift interferometer used for absolute distance measurements. It has been shown that the error caused by the nonlinear and time-varying current-wavelength characteristic of the laser diode can be removed by combining the Fourier transform technique with the reference technique. A novel technique for distance measurement based on multiple-beam interferometry has been proposed, and an experimental demonstration is given for a three-beam interferometer that includes a reference reflector as an integral part of the system. Error sources and the limitation of the technique are discussed.