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3D Measurement Method Research Based On The Phase Coding Fringe And Phase-shift

Posted on:2017-05-19Degree:MasterType:Thesis
Country:ChinaCandidate:B LiFull Text:PDF
GTID:2308330503460360Subject:Optical Engineering
Abstract/Summary:PDF Full Text Request
Three-dimensional measurement is a new-type measurement technology which depends on a computer vision, information optics, mechanical control and electrical systems. It has the advantages of non-contact, high precision, real time, adaptability, more information and so on. With the rapid advancement and low cost of related hardware and software performance, the advantages of three-dimensional measurement technology gradually get into full play. It has the wide application in all aspects, especially in life, production, scientific research and military. Three-dimensional measurement technology based on fringe projection profilometry is one of the most common and most effective technology. However, the measurement speed and accuracy are still the main problem which need to discuss and research.Compared with Gary plus phase shift method, Gray code embed the codeword into intensity, which is more sensitive to the ambient light, camera noise and the surfaces reflectivity of measured object. That will affect the result of reconstructing three dimension with complex shape. While, the phase has better robustness and less interference with the above mentioned factors. When the phase unwrapped, the fringe order can be accurately obtained, which can be measured the surfaces of object with different contrast. This paper will study three-dimensional measurement method with fast speed, high resolution based on phase encoding fringe plus phase shift.The main contents and work are as follows: 1. The three-dimensional measurement method is proposed based on phase coding fringes period correction. Most fringe projection profilometry are used by DLP obliquely projection intersecting axis measurement system, fringe period on the reference plane will be broaden, and CCD vertically collects the non-uniform fringe on the captured image plane. After reconstruction, the measurement accuracy will be significantly reduced. The fringe period broaden rule has been researched, the periodic non-uniform sinusoidal fringe is generated. In accordance with non-uniform sinusoidal fringe, the corresponding period non-uniform phase coding fringe can be obtained, which regard as projected fringes. Experimental results show that a non-uniform sinusoidal fringe and phase coding fringe are projected, the accurate phase unwrapping can be achieved. Then the phase error is reduced, at the same time improving measurement accuracy. 2. Three-dimensional measurement method based on color phase coding fringe combining with phase shift is proposed. Gray fringe measurement technique based on single channel has been difficult to meet fast-speed, high-precision measurement trend. Therefore, the study embedded the phase coding fringe into three channels to form color fringe. By increasing the number of channels, the number of projection fringe can be reduced, thereby increasing the measurement speed. However, color fringe exists crosstalk between each channel, while the measurement accuracy is also affected by nonlinear effects. Using a software algorithm to compensate channel crosstalk, intensity imbalance and nonlinear systems, measurement error will be reduced. A new fringe order correction method to reduce the error of phase unwrapping is also proposed. Experimental results show that the color phase encoding combining with phase shift measurement method can improve the measurement speed, measurement accuracy is also improved.
Keywords/Search Tags:three-dimensional measurement, phase coding fringe, phase-shift method, fast speed, high precision
PDF Full Text Request
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