A Three-dimensional Contour Testing Technique For Specular Objects Based On Binocular Stereo Vision

The function of optical system is directly affected by optical mirror surface precision.With the improvement of optical design,manufacturing technology and the increase of the actual demand,free from surfaces with high degree of aspherical or non-rotational symmetry are more and more used in the optical systems.But traditional optical measurement techniques is difficult to test this kind of asphere with complex surface,so free from surface measuring technique faces bottleneck.As a result,a testing method with flexibility,high accuracy and efficiency is pressing needed.This paper introduces the mirror object 3D profile measurement technology based on binocular stereo vision and focuses on the study of system calibration,global phase unwrapping and surface recovery algorithm based on gradient.Firstly,using checker board to calibrate the intrinsic and extrinsic parameters of two cameras and calculate the transformation relationships between them.In the study of global phase unwrapping technique,it comes to a conclusion that dual-frequency phase unwrapping technique method works best under the environment of simulating random noise and defocusing error.Besides,we plug gradients into Zernike polynomials algorithm or Fourier transform algorithm to calculate surface profile,the results show that Fourier transform algorithm is more suitable to rebuild free form surface because of its little limitation of shape or gradient.Finally,we build the mirror object 3D profile measurement system based on binocular stereo vision,and recover a rearview mirror surface.Comparing with classical test method to analyze recovery result and verify accuracy of system reaches micron scale.