Collimation testing and calibration using a heterodyne Moiré method

This study proposes a simple, rapid, and highly accurate method to achieve the collimation testing and calibration of laser light beams. By applying a relative constant velocity to two gratings, every pixel of a CMOS camera can receive a series of heterodyne moiré signals. Based on the least squares sine fitting algorithm, the phase of the optimized sinusoidal wave can be obtained. Consequently, the phase slope along the direction perpendicular to the grating lines can be estimated and then used to judge the degree of collimation. Furthermore, by measuring only two phase slopes at two positions of the collimating lens, the calibration of the light beam collimation can also be achieved. The experiment validated the proposed method, and the positioning error of the light beam collimation was approximately 7 μm.