采用棋盘纸定标，通过过相机捕获到的图片，不断旋转棋盘纸的位置，在4个坐标系之间的的来回转换，最后得到相机的内外参，注意保存在xml文件里(Chessboard calibration is adopted. Through the pictures captured by the camera, the position of chessboard is constantly rotated, and the conversion between the 4 coordinate systems