基于Brox光流估计的物体面形测量新方法

New Method for Surface Shape Measurement Based on Brox Optical Flow Algorithm

提出了一种利用光流场原理测量物体面形的新方法。测量系统由投影仪、被测物体以及CCD摄像机组成。将光栅条纹以小角度投影到参考平面上,分别采集被测物体加入前后的两幅条纹图像。对测量系统的空间几何结构进行分析,以参考面为参照系,建立了投影仪、摄像机、观测点三者的位移与物面高度的空间关系,其中,观测点的位移是基于Brox光流算法通过估计两帧图像间的光流分布得到的。针对测量系统导致的测量结果与实际形状不一致的问题,结合球冠几何模型的数值模拟结果,分析了误差产生的原因,提出了修正方法。理论模拟结果和实际测量结果验证了所提方法的可行性。与傅里叶变换法进行了比较,证实了所提方法仅用两帧图像即可精确地恢复物体的高度信息,实验过程简单,有效缩短了测量时间,且适用于动态测量。

A new technique for surface shape measurement is proposed,which is based on the Brox optical flow algorithm.The measurement system consists of a projector,a CCD camera and the measured object.First,one fringe pattern is projected onto a reference plane at a small angle and then two fringe images are recorded using the CCD camera before and after the measured object is added,respectively.Based on the analysis of the spatial geometry of the measurement system,the spatial relationship between the height of the object plane and the displacements of the observing point,the projector and the camera is established,in which the displacement of the observing point is obtained by estimating the optical flow distribution between two images based on the Brox optical flow algorithm.Aiming at the problem caused by the measurement system that the measurement result is not consistent with the actual shape,we analyze the cause of the error through the numerical simulation with the spherical crown geometrical model and propose a modified method.The theoretical simulation and the actual measurement verify the feasibility of the proposed method.By comparing with the Fourier transform method,it is proved that the proposed method can accurately restore the height information of the object with only two frames of images.The experimental process is simple,the measurement time is effectively shortened,and it is suitable for a dynamic measurement.