摘要
A flexible calibration method based on a front-coated flat mirror is proposed for a laser light-sectioning three-dimensional(3D)measurement system. Since the calibration target and its mirror image are spatially separated and can be recorded in an image by a camera,the proposed method requires only a single composite image that contains a non-planar checkerboard pattern,a laser strip projected on the target and their mirror images to complete the calibration of the camera and the laser plane in one step. Levenberg-Marquardt(LM)algorithm is used to optimize the system parameters,and the measurement accuracy and speed are improved to enable online 3D inspection. Static and dynamic online 3D measurements are carried out on a cup and a triple stepped shaft,respectively,to validate the proposed method. The shaft has two steps with the depth of(0.5±0.01)mm and(2±0.01)mm to be measured online when the shaft is rotated and translated at the same time. The measurement results can be output at a frequency of 7 to 11 readings per second with standard deviations of 0.040 mm and 0.051 mm. The experimental results verify the effectiveness and flexibility of the proposed method.
针对激光光切三维测量系统提出了一种基于前涂层平面镜的灵活标定方法。由于标定物和其镜像在空间上是分离的,并且可以由摄像机记录在一幅图像中,因此该方法只需要一幅包含非平面棋盘格图案和投影在标定物上的激光条及其镜像,就可以一步完成摄像机和激光平面的标定。采用Levenberg-Marquardt(LM)算法对系统参数进行优化,测量精度和速度得到提高,从而实现在线3D检测。为了验证方法的有效性,分别对一个水杯和一个三阶梯轴进行了在线静态和动态三维测量。阶梯轴有两个深度分别为(0.5±0.01)mm和(2±0.01)mm的台阶,当轴同时旋转和平移时对两个台阶进行在线测量。测量结果可以以每秒7到11个读数的频率同时输出,标准偏差分别为0.040 mm和0.051 mm。实验结果验证了本文方法的有效性和灵活性。
基金
supported in part by the National Natural Science Foundation of China (No. 11802132)
the Natural Science Foundation of Jiangsu Province(No.BK20180446)。
作者简介
Corresponding author:Dr.LIU Cong received his B.S.degree in engineering me⁃chanics from Southeast University,China,in 2011 and his Ph.D.degree in solid mechanics from Southeast University,China,in 2017.He is currently a lecturer in Nanjing Univer⁃sity of Science and Technology.From 2013 to 2014,he was a research assistant at Singapore University of Technology and Design,Singapore.His research interests include experi⁃mental solid mechanics,optical measurement methodology,image processing and camera calibration.E⁃mail address:LiuC@njust.edu.cn;Prof.KANG Xin received her B.S.degree in me⁃chanical engineering from Dalian Jiaotong University,Chi⁃na,in 1989,her M.S.degree in fluid mechanics from Nan⁃jing University of Science and Technology,China,in 1992,and her Ph.D.degree in engineering mechanics from South⁃east University,China,in 2003.From 2001 to 2002 and from 2006 to 2007,she was a research engineer and a re⁃search fellow in the Department of Mechanical Engineering,National University of Singapore,Singapore,respectively.From 2009 to 2010 and from 2016 to 2017,she was a visit⁃ing scholar in University of California,Davis,USA and Oakland University,USA.From 2003 to 2014,she has been with School of Science,Nanjing University of Science and Technology.She is currently a professor of Putian Uni⁃versity and an adjunct professor of Nanjing University of Sci⁃ence and Technology.Her research interests include optical measurement,nondestructive testing and digital image corre⁃lation techniques.
