3D Measurement System Based On Encoding Structured Light With Sub-stripe Resolution

With the continuous development of science technology and the eagerness of mankind to know the world, optics non-contact measuring technology is regarded as one of important methods to obtain 3D information of the objects. With high measuring precision and resolution, structure light encoding method carried out easily is becoming the hot plot of the 3D measuring field.Among these encoding methods, the plot of the measured space, which is plotted by Gray encoding method belonging to time encoding method, is discrete, so the resolution is restricted to the width of single stripe. To solve the problem, a new space-encoding method is designed which combines Gray code and phase shift after comparing a lot of kinds of encoding methods. In theory, combining the two methods can continuously subdivide the measured space and improve the resolution.According the above encoding methods, this thesis establishes the mathematical model, emulate and physical system, which complete the measuring experiment of the system. The important works are studied as followed:1.A kind of improved phase shift projecting pattern applicable for measuring system based on structured light is designed, which could ensure that phase of sampling points vary in (π, -π] periodically. Combining phase with Gray code corresponded by sampling points, absolute phase is acquired. So the corresponding relationship of the points on CCD and DMD respectively is confirmed.2. After completing the image processing in the decoding process, the emphases is the exact binary algorithm of the Gray code image based on the method of dynamic threshold value. The period dislocation between Gray code and phase-shift could be corrected by judging the consistency between Gray code value increasing and phase mutation of alternate pixels.3. Using CCD camera and DLP projector established measurement system. The system is calibrated by using the method of flat calibration. Then the measuring experiments are carried on by making use of the calibrated system.As the experiment results indicate, the simulation calibration parameters relative error is smaller than 0.3%; the simulation system measuring error is smaller than 0.3mm; the actual system plane measurement error is less than 0.4mm. A good visual effect to typical complex 3D superficial restructuring is obtained.