Dynamic Measurement of Large Displacement Using Heterodyne Laser Interferometry

Abstract

Dynamic measurements in the order of nanometer by heterodyne laser interferometry for large displacement! comparing them to the unitscale were studied. Two Wollaston prisms were positioned in the back to back arrangement to expand measurable displacements. Frequency dividers were used to enhance the frequency characteristics of the method effectively. Phase unwrapping which is needed in the phase-shift measurements was carried out by using a personal computer and a kind of package software together with our own. The best figure in the present stage is 70 μm in dynamic range, and 100Hz in frequency range respectively. The method was tested in stochastics and results showed the conservative value of coefficient of variable was 1.0%.