Error reduction method for singularity point detection using Shack-Hartmann wavefront sensor

A new framework is proposed for realizing high-spatial-resolution detection of singularity points in optical vortex beams using a Shack-Hartmann wavefront sensor (SHWS). The method uses a Shack-Hartmann wavefront sensor (SHWS) to record a Hartmanngram. A map of evaluation values related to phase slope is then calculated from the Hartmanngram. We first determined the singularity's position precisely by calculating the centroid of the circulation of 3×3 crosspoints. After that, we analyzed the error distribution of it, and proposed hybrid centroiding framework for reducing its error. Optical experiments were carried out to verify the method. Good linearity was showed in detecting positions of the singularity points, and it was indicated that the accuracy of detection the position of OV was improved. The average root mean square (RMS) error over various measurements was better than correlation matching method, which we proposed before. The method not only shows higher accuracy, but also consumes much less time than our former work.