Telephoto structured laser autocollimation based on common-path compensation method and ellipse fitting algorithm

A telephoto structure-based laser autocollimation with common-path compensation method is proposed to compensate laser beam drift of laser autocollimator. According to the analysis, the measurement beam and the reference beam propagate alongside nearly the same path with approximately identical amounts of drift. Moreover, the ellipses fitting algorithm based on least square approach ensures the accuracy of extracting centroid of the beam while the only photodetector (CCD) with the telephoto objective and several reflectors guarantees the compaction and effectiveness of the system. Simulations and experiments demonstrate a significant beam drift compensation result up to 86.5%. In other words, the stability of the laser beam in the process of measurement is improved.