Study And Realization Of Key Technologies In Surface Metrology Systems Based On Grating Projection

Optical 3D profile measurements plays a great role in the field of manufacturing, computer aided medicine, virtual reality, culture relic conservation, computer games and entertainment. Based on deep study of relevant theories and key technologies in the dissertation, a grating projection 3D metrology system is developed. The main contents and achievements are as follows:1. An implicit linear model for the projection system is advanced based on analyzing and researching toward the pin-hole imaging theory and the characteristics of coded structured light methods. And an intact mathematic model for the grating projection measurement system is subsequently founded.2. We have studied the Gray Code and phase shifting methods respectively, analyzed and summarized their advantages and disadvantages, and developed a novel encoding method combined with Gray Code and phase shifting. Measurement systems using this method can not only obtain larger measurement range and higher resolution, but also reduce decoding errors.3. A code revising algorithm is presented to deal with the code error owing to non-sinusoidal characteristic of the phase shifting patterns and image noise during the decoding process, thus the precision of the system is increased and the stability is enhanced.4. Camera and projector calibration techniques have been studied, a method for projector calibration is advanced based on Gray Code-phase shift fringe projection, and a system calibration procedure is presented based on error analysis. An algorithm for fast acquisition and match of calibration data is advanced.5. On these bases we have developed a three-dimensional optical measurement platform, including hardware and software. Finally we have done a large number of test measurements using this system, and applied in the field of reverse engineering, oral and facial measurements. The analysis and research results show that the system has a good performance and precision, point amount of a single view is 1.3 million, measurement range is 450 mm×400 mm, and lateral points distance is 0.5 mm.