Small-angle measurement in laser autocollimation based on a common-path compensation method

In this study, a common-path compensation method is proposed for the laser beam drift resulting from the air parameters to enhance the stability of small-angle measurement in laser autocollimation. The measuring and reference beams generated with this method can propagate along approximately the same route such that the drifts in the two beams are nearly equal. Therefore, the angular drift of the measuring beam can be adequately compensated by that of the reference beam. The compensation principle was analyzed, and the experimental results revealed that, with three types of air parameter disturbances, the static measurement stability was better than 0.193 arcsec in 100 min after compensation, and the compensation rate was higher than 86.6%. Additionally, the dynamic measurement stability was 0.227 arcsec in 50 s after compensation, and the compensation rate was 53.6%. It is confirmed that the proposed method is effective for laser autocollimation.