中文说明： 计算十字叉丝的在不同距离的衍射图像,部分实现了追踪测速迭代松弛算法，包含位置式PID算法、积分分离式PID，关于非线性离散系统辨识，wolf 方法计算李雅普诺夫指数,用于时频分析算法。
English Description：
To calculate the diffractive images of the cross wire at different distances, the iterative relaxation algorithm of tracking velocity measurement is partially realized, including position type PID algorithm and integral separation type PID algorithm. For the identification of nonlinear discrete system, the wolf method is used to calculate the Lyapunov exponent for the time-frequency analysis algorithm.