中文说明：通过重心法确定光斑图像的中心。根据个像素的灰度值和所在的位置乘积和总面值作比，进而求得重心。
English Description：
The center of the spot image is determined by the barycenter method. The center of gravity can be obtained by comparing the product of gray value and position of each pixel with the total face value.