3D Vision Measurement Method Combining Of Gray Code With Analog Code

Traditional vision maps three-dimensional scenes into two-dimensional images,which can't reflect a truly three-dimensional objective world because of the loss of depth information.Hence,the research and application of three-dimensional vision is concerned greatly nowadays.Three-dimensional computer vision acquires and processes information in the form of images,which is closer to human vision.Since the three-dimensional measurement has the advantages of non-contact,high resolution and fast speed,so it has made great progress in development and commercialization.The 3D vision measurement method combining of Gray code with analog code is a typical method.Theoretically,this method can get larger range of 3D measurement and maintain higher resolution and measurement accuracy,but it often appears coarse measurement error of integer multiple fringe periods in the actual measurement process,resulting in a sharp drop in the measurement accuracy,and the measurement results are difficult to use.The three-dimensional measurement method combining of Gray code with analog code was studied in this paper.Through theoretical analysis and measurement experiments,the phenomenon of period jump error and its production mechanism during analog code expansion are explained.Then in order to reduce the error of analog code expansion,new three-dimensional visual measurement methods combining of Gray code with analog code are proposed and implemented.1.A method of three-dimensional computer vision measurement based on unequal period combination of Gray code and analog code is proposed.This method uses residual error expression and takes measures in projected pattern design.One is that the fringe period of lowest bit in the gray code projection pattern is not equal to the fringe period in the analog code projection pattern;the other is that the initial phases of both the gray code and the analog code projection patterns are not equal.Using this projection pattern,an absolute analog code without period jump error can be obtained by direct operation,and then the three-dimensional shape of the surface of the measured object can be mapped.2.A method of three-dimensional computer vision measurement based on equal period combination of Gray code and dual-frequency analog code is proposed.This method additionally projects a set of low frequency analog code stripe patterns,and then takes steps to improve the analog code expansion algorithm.According to the low frequency analog code stripe pattern parameters,the low frequency absolute analog code can be solved,and According to the high frequency analog code stripe pattern parameters,the absolute analog code that can eliminate the period jump error can be solved.And then the three-dimensional shape of the surface can be got.3.A method of three-dimensional computer vision measurement based on unequal period combination of Gray code and dual-frequency analog code is proposed.This method projects a set of high-frequency and a set of low-frequency non-equal-period combination patterns of Gray codes and analog code.Meanwhile,two steps are adopted.One step is the design of non-equal-period combined projection pattern,and the other is dual-frequency analog code expansion algorithm.High-frequency and low-frequency absolute analog code measurement values are obtained respectively by the non-equal-period combination method.According to the difference between the two measurement values,the high-frequency absolute analog codes are corrected.There is no period jump error in the three-dimensional shape of the surface obtained from the corrected high-frequency absolute analog code.4.The theorys of the proposed methods were analyzed,the measurement models and applicable conditions were established,a simulation system and an experimental device were designed,measurement experiments were performed,and qualitative and quantitative evaluations were performed.The results of theoretical analysis and measurement experiment show that these proposed methods can eliminate period jump errors under the applicable conditions,and the measurement error contains only the remaining analog code error,which can realize the higher measurement accuracy of the complex scene surface of threedimensional visual measurement,they also have advantages of large range,high sampling density as well as high resolution.