Research On Phase-assisted Binocular Vision Measurement Based On Orthogonal Color Fringe Projection

In recent years,optical 3D(three-dimensional)measurement technology is developing rapidly and is widely used in aerospace,industrial manufacturing,reverse engineering,virtual reality,medical engineering and many other fields.As a bionic optical 3D measurement technology,binocular stereo vision becomes the research focus,because of its high efficiency,simple system and low cost.A complete binocular vision system mainly includes the following four steps: image acquisition,camera calibration,stereo matching and 3D reconstruction.In the four steps,stereo matching is the most important part.The stereo matching accuracy will directly affect the accuracy of the final 3D reconstruction.Traditional stereo matching algorithms include intensity-based methods and feature-based methods.But with the wide application of binocular stereo vision technology,there are often some special objects to be measured,such as objects with very few features or with many details.Very high measurement accuracy and efficiency are often required.Therefore,traditional stereo matching method is usually unable to meet the demand.For the limitations of traditional algorithms and the application requirements of high accuracy,a new stereo matching algorithm is proposed in this paper.First of all,color sinusoidal fringes in both horizontal(red fringe)and vertical(blue fringe)are projected on to the object to be measured.Then the wrapped phase and unwrapped phase of each pixel along the two directions are calculated based on four-step phase-shifting algorithm and the optimum fringe numbers selection method.Finally,stereo matching is performed based on the fringe unwrapped phase of the left and right phase maps.In this process,in order to improve the measurement efficiency,the fringe order constraint is used to narrow the search range of the matching point.In order to ensure that each step can minimize the error,the algorithm with higher accuracy is selected through experiments,during the 3D reconstruction process.At last,a 3D measuring system is set up based on the algorithms proposed in this paper.A step artifact,a foam box,and a china cup are measured and reconstructed by the system.The experimental results show that the proposed algorithms are effective for special free-form surface objects measurement and the measurement accuracy is improved significantly compared with the traditional measurement algorithm.