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Structured-light Three Dimensional Measurement Method Based On Digital Projector

Posted on:2016-08-14Degree:DoctorType:Dissertation
Country:ChinaCandidate:W Z ZhangFull Text:PDF
GTID:1108330464959476Subject:Optical Engineering
Abstract/Summary:PDF Full Text Request
The world we live in is three dimensional (3D). With the development of the society, the demanding for the 3D information of things is growing. As one of the most important technologies, the structured-light (SL) 3D measurement method based on the digital projector has been a hot for years. However, there are two difficulties in this field, the nonlinear effect of digital projection and the wrapped phase.In order to overcome these two bottlenecks and produce more accurate 3D information, some properties of the SL 3D measurement method are studied in this thesis. What’s more, several novel SL 3D measurement technologies are first presented.1. We analyze the nonlinear property of the SL system based on the reference plane method, and present the phase profile error model. Based on this model, theories about the amplitude and the phase angle of the phase profile error, vanishing points of the phase profile error, the maximum phase profile error points, are first proposed. Through experiments, the theory about the vanishing points of the phase profile error is thoroughly verified.2. The defocusing effect and the binary defocusing patterns are reviewed. Especially, the phase error property of the sinusoidal patterns processing by Floyd-Steiberg Dithering algorithm is first studied. The phase error under different. pitch-widths, different defocusing amounts, and different phase-shifting step numbers, is presented.3. Two new methods to eliminate the nonlinear effect of the SL 3D measurement system are first presented. The first one is the 2-set binary patterns for tri-polar pulse width modulation(PWM) coding method, and the other is the absolute phase error compensation method based on the reference plane SL images filtering. By using these two methods, SL 3D measurement system can achieve the nonlinear error elimination without gamma calibration of the projection,(a) The 2-set binary patterns for tri-polar PWM coding method, can represent a tri-polar PWM pattern by two binary patterns. By this method, the 3D reconstruction accuracy of the tri-polar PWM method can be achieved without gamma calibration of the projection.(b) The absolute phase error compensation method based on the reference plane SL images filtering can get the phase compensation look-up table from the reference plane SL images, and the harmonics of the nonlinear effect have been totally removed. By this method, the 3D reconstruction accuracy of SL system can be greatly improved without gamma calibration of the projection.4. The absolute phase coding methods without nonlinear effect are also studied in this thesis. Two new stair phase coding methods and a new 3D reconstruction method from the absolute phase are presented, and all of them can work without the calibration of the projector gamma.(a) Symmetric and asymmetric binary block areas phase-shifting coding methods are the two new stair phase coding methods we present. Both of them use only several binary patterns, which is simply composed of block areas. And, only traditional N-step phase-shifting algorithm is needed for the phase retrieval. In this way, the field of the view is simply coded into stair phase block areas without gamma calibration of the projection.(b) The 3D reconstruction method from the absolute phase uses two frequencies binary defocusing SL patterns to absolute phase recovery, and it can work well without nonlinear effect. By using the direct phase to three coordinates mapping method, the accuracy of one coordinate would not depend on any other one. And, the coordinate form known plane method makes our calibration method more flexible and large working range can be easily achieved.
Keywords/Search Tags:structured-light three dimensional measurement, nonlinear effect, absolute phase coding, defocusing light projection, binary pattern
PDF Full Text Request
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