Projector Lens Distortion Correction And Measurement Software Development Of Fringe Projection Profilometry

Optical three-dimensional(3D)measurement technology is widely used in industry,medicine,entertainment and scientific research and has achieved remarkable results.As one of the fastest growing and most widely used branches,fringe projection profilometry(FPP)has been greatly recognized in optical 3D measurement.With the development of modern industry and the improvement of people's living standards,3D measurement is required to develop in the direction of high-accuracy and high-speed measurement.As a projection device,a projector is regarded as an inverted camera,but it cannot show the same good distortion correction accuracy as a camera using existing distortion method,especially in wide-area 3D vision measurement.In response to the above problems,combined with epipolar constraint,two simple and effective methods for projector lens distortion correction are proposed,and a human-computer interactive measurement software is built,thus to improve the reconstruction accuracy and measurement speed of fringe projection measurement system.Firstly,based on the post-processing method,a solution to correct projector lens distortion through double epipolar constrained-undistortion is proposed.In the process of stereo matching,the corresponding points of a camera and a projector on the imaging plane can be obtained through both uni-directional fringes and a general single epipolar constrained-distortion.This method proposed in this paper is based on a general single epipolar constraint,the second epipolar constraint is performed on projector pixel points to achieve high-accuracy corresponding points,thus to improve the accuracy of stereo matching.Secondly,based on the pre-processing method,a solution to correct projector lens distortion through pre-distorting projected images is proposed.After the distortion coefficients of a fringe projection system are calibrated,the uni-directional fringe images used for measurement are pre-distorted based on the distortion coefficients and the distortion model,so that the fringes projected by a projector into the object plane are as close as possible to the standard fringes,and there is no undistortion calculation that is required in the posterior data processing stage.Thus to improve the measurement accuracy and measurement speed.Thirdly,a human-computer interactive measurement software was built to achieve projection fringes acquisition and data processing.The hardware control program and image processing program are written on the VS platform to realize the synchronization of a camera and a projector and the data subsequent processing,so that the interface has the functions of hardware parameters adjustment,image acquisition,image saving,image processing,reconstruction result display and so on.Finally,based on the built monocular FPP system,the system is calibrated.The two proposed projector distortion correction methods are verified by simulation and experiments.The results show that RMS reconstruction errors of the double epipolar constrained-undistortion method and the pre-distorting projected images method are0.015 mm and 0.0130 mm,respectively,which are 32.9% and 27.6% of a general single epipolar constrained-undistortion method error.Both methods effectively improve the accuracy of 3D reconstruction.