Research On High Light Elimination Method For Structured Light Measurement Of Three-dimensional Fringes On Highly Reflected Surface

Structured light three-dimensional measurement technology has become a representative technology in the field of optical three-dimensional measurement because of its high accuracy,non-contact,fast and other advantages.For many objects(metals,ceramics,etc.)with strong reflective surface in industrial detection,the specular reflection on the surface of the object produces high light,which results in the over-exposure of the images collected by the camera,resulting in the lack of fringe information in the strong reflective area and the error of three-dimensional reconstruction.Based on the induction of relevant theories,this paper focuses on the three-dimensional measurement of specular reflectors,which mainly includes the following contents:(1)Two kinds of high-light elimination strategies in three-dimensional measurement of Structured Light with Strong Reflective Surface Stripes are studied.1.Firstly,a series of fringe images with different exposure times are taken,and the camera response function is estimated to obtain the mapping relationship between the pixel value and the exposure amount.Then,the images with different exposure amounts are fused into a high dynamic range(HDR)image.Experiments show that the high dynamic range method can effectively reduce the adverse effects of high light on three-dimensional measurement.2.The three-dimensional measurement method based on adaptive fringe pattern projection is improved.Aiming at the problem of too sparse pixels in solving projector mask,a method of solving pixel boundary by Canny operator and filling pixels is proposed.The projector mask is perfected and adapted to the local reflectivity of the measured object surface,which avoids the over-saturation of the image of the strongly reflective surface and maintains the intensity modulation of the whole strongly reflective surface.This method can obtain clear fringe images in high-light region,and has the advantages of high accuracy and simple operation.(2)A three-dimensional measurement method of strongly reflective surface based on two-color reflection model and image restoration is proposed.The two-color reflection model and intensity logarithmic differential theory are used to determine the specular reflection pixels,and then the high-light pixels are selected to adjust the chromaticity peak of the specular reflection component in the maximum chromaticity intensity space,so that it approaches the chromaticity peak of the diffuse reflection component and achieves the purpose of separating the diffuse reflection component from the specular reflection component in the image.However,there is a problem that the chromaticity value after separation is too low to form a void in the experiment.The theory of image restoration based on improved Criminisi algorithm can make up for the shortcomings of reflection separation method,and the combination of the two methods can achieve the purpose of restoring fringes in high-light region.The experimental results show that the saturated pixels in the strong reflective region are basically eliminated and the number of specular reflective pixels is reduced to about 1%.The requirement of precise measurement of the surface of a strong reflective object by a single three-dimensional sensor is realized.