Analysis about the Technique of Carrier Modulation in Moiré Interferometry
云纹干涉载频调制技术及分析

The technique of carrier modulation in Moiré interferometry is important in displacement measurement of an object. In Moiré interferometry when two symmetrical collimated beams illuminate the specimen grating, diffracted beams travel along the normal direction of the specimen grating and interfere. Changing one incident angle of the symmetrical illuminations can modulate the interference fringe pattern. The changes of optical path lengths are analyzed to demonstrate the principle of carrier pattern. And the relationship between the changes of the incident angle and the frequency of carrier produced is given in the paper. A two-dimensional modulation experiment is completed with typical three-point-bending beam. Some results are offered. The experimental results prove that the technique of carrier modulation is feasible in displacement measurement in moiré interferometry when there are few fringes in the pattern before deformation.