采用立体视觉实现子孔径拼接测量的工件定位

为了实现大口径光学元件的子孔径拼接干涉测量,提出了采用立体视觉进行光学元件位姿测量的方法,建立了基于双目视觉的子孔径拼接测量系统。介绍了圆形子孔径拼接干涉测量的原理,基于齐次坐标变换分析了其对工件定位的要求;引入了立体视觉辅助测量系统,建立了通用测量模型,利用双目视觉获取不同子孔径测量时与工件刚性连接的特征点的三维全局坐标,在完成全部子孔径测量后利用四元数法求取各子孔径相对于全局坐标系的转换矩阵,然后利用优化拼接算法将各子孔径数据统一到全局坐标系下,完成大口径光学元件的全局测量。最后利用该系统实现了对口径为150mm平面和100mm球面的检测。实验结果证明,在本系统中,立体视觉系统平移定位精度优于0.1mm,转动测量精度优于0.01°,可为优化拼接算法提供一个有效的初始值,该方法能够快速给出各子孔径间的相对坐标变换且不产生误差累积方法简单且可靠。

Work-piece localization in sub-aperture stitching test based on stereo vision

In order to realize sub-aperture stitching measurement of a large-aperture optics, a work-piece localization method based on stereo vision is introduced,and a measurement system is set up. Firstly, the measuring principle of a sub-aperture stitching test is given, and its requirement for the work-piece localization is analyzed. Then, the stereo vision measurement system is introduced and its measuring model is established. After that, the marked points' 3D coordinates which are rigidly connected with the optics under test are obtained and the transformation matrix is solved out by the quaternion method. Then, the full-aperture phase map is synthesized by mathematically minimizing the mismatch among the overlapping areas of all sub-apertures. Finally, a 150 mm flat and a 100 mm convex sphere are tested using this method. Experimental results indicate that the translation precision and rotation precision of the system are better than 0.1 mm and 0.01°, respectively,which can provide an effective initial value for the stitching algorithm.Furthermore,the measurement error of the system does not accumulate with the motion in its view field,and can satisfy the system's precision requirements.