基于投影栅相位法和多曝光图像融合技术的强反射表面轮廓检测

High reflection surface topography measurement based on fringe projection phase method and multi-exposure image fusion technology

光栅投影三维测量技术因其非接触式、分辨率高和精度高等优点,已成为应用最为广泛的三维测量技术之一,但对于具有强反射表面的被测物,所采集的图像会出现局部过明或过暗的现象,导致测量的点云缺失,影响测量精度。为了实现强反射表面物体三维轮廓的精确测量,提出一种改进的多曝光图像融合技术。利用白光投射下不同曝光时长的图像制作掩模,分别与光栅投射下相应曝光时长的条纹图像相乘,将所得图像进行线性变换后叠加,再对其灰度值归一化后进行伽马变换和灰度值还原,最后利用所得条纹图像解相并计算被测物体表面三维点云数据。实验表明,该方法在一定程度上克服了因物体局部高光而导致的点云缺失,对于法兰片、标准块和U型卡三种具有强反射表面的被测物,分别能计算出99.8%、99.1%和99.3%的点云数据,实现了强反射金属表面较为完整的三维轮廓检测。

Grating projection three-dimensional measurement technology has become one of the most widely used three-dimensional measurement technologies owing to its noncontact,high resolution,and high accuracy advantages.However,for objects with highly reflective surfaces,the collected image appears partially too bright or dark,which results in point cloud measurement loss,thereby further affecting the measurement accuracy.To accurately measure the three-dimensional contour of objects on high reflective surfaces,an improved multi-exposure image fusion technique is proposed.Images of different exposure durations under white light were used to create masks,and the corresponding exposure duration under grating projection were multiplied using stripe images.After a linear transformation,the obtained images were superimposed and then subjected to a gamma transformation.Finally,the obtained stripe images were used to solve the phase and calculate the three-dimensional point cloud data of the measured object surface.Experiments show that this method can overcome the lack of point cloud data caused by the local highlight of the object to an extent.For the three tested objects with high reflection surface of flange,standard block,and U-card,more than 99.8%,98.1%,and 99.3%point cloud data can be calculated,respectively.Consequently,a more complete three-dimensional contour detection of high reflection metal surface can be realized.