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

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. © 2022 Guangxue Jingmi Gongcheng/Optics and Precision Engineering. All rights reserved.