基于FPGA的实时线结构光传感器激光条纹中心提取方法  

A real-time laser stripe center extraction method for line-structured light system based on FPGA

作　　者：苏中元 康杰虎 冯橹源 李泓彤 张振 孙泽峰 吴斌[1] SU Zhongyuan;KANG Jiehu;FENG Luyuan;LI Hongtong;ZHANG Zhen;SUN Zefeng;WU Bin(State Key Laboratory of Precision Measuring Technology and Instruments,Tianjin University,Tianjin 300072,China)

机构地区：[1]天津大学精密测试技术及仪器国家重点实验室,天津300072

出　　处：《Journal of Measurement Science and Instrumentation》2023年第4期452-462,共11页测试科学与仪器（英文版）

基　　金：National Natural Science Foundation of China(No.62071325);Open Foundation of Beijing Laboratory of Optical Fiber Sensing and System(No.GXKF2022001)。

摘　　要：激光条纹提取方法是线结构光传感系统中的一项重要技术,其准确度和速度直接影响系统的测量性能。然而,传统Hessian矩阵法可能会产生多余中心点和缺失中心点,限制了其准确度和鲁棒性。此外,传统Hessian矩阵法计算复杂,难以应用于实时测量场景。为此,提出了一种适合在FPGA中实现的激光条纹中心提取改进方法。首先,设计了一个新的判断函数来代替最大特征值来选取显著中心点,以增加真实中心和其他区域之间的数值差异,并通过修改中心判断标准,采用非最大值抑制的方法处理多余中心点和缺失中心点。其次,将所提出的方法在FPGA中进行实现。在不降低精度的前提下,对计算进行了合理优化,减少了FPGA的资源利用率和延迟时间。在准确度对比试验中,在噪声水平分别为0,0.01,0.02和0.03时,平均绝对误差分别为0.0039像素,0.0373像素,0.0520像素和0.0646像素,均方根误差分别为0.0068像素,0.0469像素,0.0654像素和0.0811像素;在FPGA中实现时,运行时间和延迟时间分别为14.89 ms和216.42μs。实验结果证明,所提出的方法准确度高、鲁棒性好,能够进行实时中心提取。Laser stripe extraction serves to be a crucial technique in the line-structured light system,and its accuracy and speed are directly related to the measurement performance.However,the traditional Hessian matrix method may produce redundant centers and missing centers,which will limit its accuracy and robustness.Besides,the complex calculation of the method makes it difficult to be applied in real-time measurement.In order to overcome these issues and achieve real-time center extraction,an improved FPGA-friendly laser stripe center extraction method is proposed.A novel judgment function is designed to replace the maximum eigenvalue,and the numerical difference between the centers and the other domains is more salient.The center judgment criteria are modified and the non-maximum suppression is used to deal with the redundant and missing centers.Furthermore,the proposed method is implemented in FPGA to achieve real-time processing.The calculations are rationally optimized to reduce resource utilization and delay time without reducing the accuracy.The mean absolute errors are 0.0039 pixel,0.0373 pixel,0.0520 pixel,and 0.0646 pixel,and the root mean square deviations are 0.0068 pixel,0.0469 pixel,0.0654 pixel,and 0.0811 pixel,respectively,in the accuracy experiment with the noise deviations of 0,0.01,0.02,and 0.03.The running and delay time of the proposed method in FPGA are 14.89 ms and 216.42μs.The experimental results verify that the proposed method is highly accurate,robust,and time-efficient.

关 键 词：激光条纹中心提取方法 Hessian矩阵法 多余中心点和缺失中心点 现场可编程门阵列(FPGA) 线结构光传感测量系统 

分 类 号：TN929.1[电子电信—通信与信息系统] TP212[电子电信—信息与通信工程] TN791[自动化与计算机技术—检测技术与自动化装置]