Research On The System Of Grating Projection Three-dimensional Profilometry

For the past few years, the technique of three-dimensional profilometry has been widely utilized into reverse engineering, quality control, automatic on-line detection, medical diagnosis, digitization of cultural relics, anthropological measuring, and other fields. In the1980s, foreign countries had began to research the technology of structured light3D profilometry. At present, this technology has been developed maturely in foreign countries. However, the domestic research on the technology of structured light3D profilometry is still in the stage of growth.The measurement systems designed by domestic organizations have a long distance with foreign advanced products in the aspects of measurement accuracy, speed and stability.The grating projection three-dimensional profilometry measurement projects a sine grating stripe onto the surface of measured thing by a digital projection equipment. The image of distorted grating stripe modulated by the measured things surface hight is collected by the image sensor. The computer calculates the hight of the measured things through the differences of each pixel s gray value. In this way, the point cloud of the measured things surface can be got by the computer.Based on the deep understanding of the background and the present research status of structured light3D profilometry, a deep study of the key technology of grating projection three-dimensional profilomery had been developed. A system of grating projection three-dimensional profilometry has been preliminary set up, which is applied in the experimental measurement and has moderate price.In the early period to set up the system, the key technology of this measurement technology, such as photogrammetry, optics, gray coding ets had been seriously studied. In the process to achive the system’s3D measurement function, each encountered technical problems such as camera calibration, corner detection, phase calculation, Image preprocessing etc had been solved. And the construction of the measurement system had been completed. After the completion of the measurement system, the accuracy of this system found didn t reach the desired effect by the experiment. Therefore, various factors which maybe influence the accuracy of the measurement system had been analyzed. Finally, the nonlinearof the system was decided to modify to imorove its precision through changing the number of phase shift frame and the mode of projector s input light.The modified mothed proposed above were proved effective by the experimental data. Ultimately, the accuracy of the3D measurement system had been successfully improved to0.1mm.