适用于信标光检测的非对称中值滤波改进算法

在进行星间激光通信时，光斑位置检测的准确性会直接影响捕获、跟踪、瞄准过程。然而由于其采集传输过程中受到干扰或自身器件响应的缺陷，导致出现模糊及噪声，因此在进行光斑定位前应当进行滤波预处理。经典3×3窗口的中值滤波算法对噪声的滤除效果较好，但处理时间过长，因此提出了基于3×4窗口的非对称快速中值滤波的算法。首先对经典方法两个相邻窗口处理时重复利用的6个中间像素值进行排序，再分别与窗口内最左列和最右列中值进行比较，所得中值替换掉原信号中心位置两个像素。经目视观察，两种滤波算法去噪效果相当。对于3×4窗口的改进中值滤波带来的后续光斑定位误差问题，可以通过统一标校进行弥补，误差在可接受范围内。通过程序仿真结果可得，改进的快速中值滤波算法缩短了响应时间。因此，非对称中值滤波改进算法增强了算法的实时性，更适合基于FPGA平台的设计与实现。

An improved asymmetric median filtering algorithm for beacon light detection

When performing inter-satellite laser communication, the accuracy of spot position detection will directly affect the capture, tracking and aiming process. However, due to interference or defects in the response of its own device during the acquisition and transmission process, blur and noise appear, so filtering preprocessing should be performed before spot positioning. The classical median filtering algorithm of 3×3 window had a good filtering effect on noise, but the processing time was too long. Therefore, an asymmetric fast median filtering algorithm based on 3×4 window was proposed. First, the 6 intermediate pixel values reused in the 2 adjacent windows of the classical method were sorted, and then compared with the median values in the left-most column and right-most column of the window respectively. The obtained median values replaced the 2 pixels in the original signal center position. By visual observation, the denoising effects of the 2 filtering algorithms were equivalent. For the spot location error caused by non-improved median filtering of 3×4 window, the unified standard comparison could be used to compensate, and the error was within an acceptable range. The simulation results showed that the improved median filtering algorithm shortened the response time. Therefore, the improved asymmetric median filtering algorithm enhanced the real-time performance of the algorithm and was more suitable for the design and implementation of FPGA-based platforms.