Research On3D Measurement Method Of Analog Coding Structured Light Based On Chinese Remainder Theorem

Non-contact three-dimensional (3D) automatic measurement method is widelyconcerned and used, and also has the broad application prospect in industrialproduction. And the temporal coding pattern structured light3D measurementmethod has become the most important development direction, especially analogcoding method has become one of the most practical and potential method owing toits outstanding advantages, such as the dense sampling, high resolution, the quickmeasuring speed. However, wrapped phase error and wrapped phase unwrapping aretwo key problems restricted the development and application of this method.Therefore, for this problem, this paper focus on coding structured light3Dmeasurement, and proposes an analog coding structured light3D measurementmethod based on Chinese Remainder Theorem (CRT). It includes the convenientlyquick phase unwrapping and the significant wrapped phase corrected methods, inorder to realize the complex scene surface measurement of3D shape.Among these existing methods of phase unwrapping, CRT possesses largestunwrapping range, and becomes the most important phase unwrapping method. Butthis method has the disadvantages of anti-interference ability, slow operation, and itis difficult to directly apply to analog3D engineering measurement area. For thisproblem, under the premise of definition of real numbers remaining measurementerror tolerance, we propose Chinese Remainder Theorem Engineering Algorithm(CRTEA) based on remaining fractional real difference criterion. Simulationexperiment verifies this method from qualitative and quantitative aspects throughlarge data and different types of residual measurement error.Combining with the Cosine phase shift, triangle phase shift and trapezoidalphase shift pattern,3D measurement method of analog coding structured light basedon the CRTEA is propose in this paper.3D scene surface information is obtained according to the mathematical model of measurement apparatus. By analyzing thewrapped phase error caused by random noise of fringe image, we confirm the rangeof coding pitch and gray modulation of patterns and complete pattern design.Simulation experiments of measuring plane and spherical verify the validity of thismethod, and comparative experiments with the multi-frequency heterodyneunwrapping method and CRT searching method are given.After obtaining camera-projector gray response experimental curve, counter thewrapped phase error owing to apparatus gamma nonlinear response, this paperpropose and realize a fast whole-range wrapped phase error correction method.Combining with the pattern pre-coding and wrapped phase Iteration compensation,the method achieve wrapped measuring error correcting in the measurementwhole-range. Theoretical analysis and verification experimental using the phase errorcorrection method is carried on.The3D measurement apparatus constructed based on the proposed method isproposed in this paper, and the unconstrained nonlinear mapping mathematicalmodel of the apparatus is built. The measurement apparatus calibration method isdesigned, and the calibration experiment is completed.3D measurement experimentsare carried, which are using the proposed3D measurement method and theconstructed3D measurement apparatus in this pape. These experiments include themeasurement apparatus mathematical model verification experiment, CRTEAverification experiment, the3D measurement methods verification experiment,measurement accuracy experiment and complex surface measurement, contrastexperiment of the effect of phase error correction methods, contrast experiment ofheterodyne method compared with proposed methods in this paper, and so on.According to the experimental results， evaluating the measurement methods andapparatus in this paper.The research of this paper provide high accuracy and wide measurement rangebasis of encoding and decoding methods, theoretical and experimental method,which is important to promote the development of structured light measurementtechnology and its engineering applications.