Research on High Precision Locating of Laser Spot Center in Free-Space Laser Communication System

The gray centroid algorithm is usually used as the centroid locating algorithm in the free-space laser communication system. However, the limited spatial resolution of the image detector will produce homogenization effect, which results in gray quantization error. Moreover, the spot information will lost when we detecting the object with threshold. The two problems mentioned above will make the locating accuracy worse when using the conventional algorithm. In this paper, we use the squared weighting centroid with threshold algorithm combined with the hardware optimized interpolation subdivision algorithm to improve the locating accuracy. As the weight of bright pixels increased, and the spot information loss decreased due to subdivision, the locating accuracy improved significantly. The simulation results show that the locating accuracy has improved by at least 50%, and the experiment results confirmed that the tracking error (2.57μrad) using the improved algorithm is less than that (4.11μrad) of the conventional algorithm.