Detection of structured laser beam centroid and its use for alignment

A Structured Laser Beam (SLB) [1] is a pseudo-non- diffractive optical beam. Its transverse profile is similar to a Bessel Beam (BB), hence its bright central core is sur- rounded by concentric circles. SLB can propagate with very low divergence over long distances. Propagation over 200 m has been tested with a divergence under 0.01 mrad. Therefore, the central core can still fit on the camera chip and its centroid position can be accurately detected, which is not the case for well-known Gaussian beams (GB). These properties make the SLB a promising candidate for long- distance alignment applications because it could be used as a reference line. The alignment accuracy is affected by the algorithms for centroid detection. In this work, different algorithms for centroid position detection are evaluated and com- pared on simulated data, namely the best fitting of a well- parameterized Bessel function and different alternations of the center of gravity methods. In addition to simulations, real data are obtained during experiments using a high- precision motorized stage to induce a known translation of a sensor resulting in misalignment. This misalignment is compared with the misalignment detected by an SLB sensor. Therefore, the potential of SLB for long-distance alignment is explored.