Centering method for non-diffracting spot images based on correlation-coefficient

In order to realize fast and precise centering with non-diffracting spot as straight-line datum under complex background noises, a centering method for non-diffracting images based on correlation-coefficient was proposed. In this algorithm, firstly the approximate position of the beam spot center is calculated based on the theory of light intensity gravity; then the image is converted to the grayscale image in polar coordinates, which generates the discrete-cycle sinusoidal signal with the same angular frequency as the spatial frequency of the spot image, and the phase angle is calculated and the average variance is evaluated for the phase information of each diameter; finally the correlation-coefficient is established in polar coordinate system for ideal beam center and actual beam center, which realizes centering the non-diffracting spot image. In the simulated noise environment, result shows that the proposed algorithm has strong ability of anti-noise interference, less time-consuming in comparison with other common algorithms, which realizes sub-pixel level accuracy.