3D Measuring Method By Gray Code Combined With Phase Shift And Its Simulation

Optics non-contact measuring technology is a kind of important method to obtain object 3D information. Structured light encoding methods with the advantage of high measuring precision and carrying out easily is becoming the research hot plot in field of 3D measuring and machine vision.Among these encoding methods, the discrete space dividing can be obtained by traditional time-encoding method with the disadvantage of low spatial resolution. To solve the problem, an improved space-encoding method is presented to obtain the system projecting angles which combines Gray code and phase shift after comparing all kinds of encoding methods. The advantages of Gray code are optimized encoding step, high stability and reduced error. With phase shift method, measured space local continuous division can be obtained. In theory, combining the two methods can continuously subdivide the whole measured space.Above all, the important works are studied as followed:1. A kind of improved phase shift projecting pattern applicable for measurement system based on structured light was presented, that could ensure that phase of sampling points vary in (Ï€,-Ï€] periodically. Combining phase with Gray code value by sampling points, absolute phase was acquired. The formula from absolute phase space to project angle space is deduced to obtain the project angle of sampling plot.2. In the course of decoding, period dislocation between Gray code and phase-shift occurred, that could be corrected by judging the consistency between Gray code value increasing and phase mutation of alternate pixels.3. 3DS Max was used to simulate the projector, camera, system facility, measured object, measuring condition to cast many stripe images. The grey image is adopted local threshold value binary algorithm to ensure the preciseness of decoding period. 4. Image process program and 3D reconstruct program was compiled by Matlab.Analytic plane, sphere surface, cone and non-resolve complicated surface were reconstructed by simulation experiment, and the experimental results were analyzed.