Research On The Key Technology Of Phase Measurement Based On Multifrequency Heterodyne Principle

Reverse Engineering (RE) as a new designing method can do a lot of things in the absorption domestic and international advanced technique, shortening the product's development period and lowering the production cost. Non-contact optical measurement technique is a key technique of data acquiring in Reverse Engineering (RE). Recently,binocular CCD fringe projection structured light measurement method is developed; it can get high-density data point cloud of a piece of surface once. Compared with traditional measurement techniques, the advantages of technique are quick and exact. In practice, it is applied more and more widely, and its function is more and more important in national economy. However, the research of the technique is just started in our country at present.The key techniques of the measurement method are systemically investigated in the thesis.Firstly, This paper puts forward a 3D measurement technology based on heterodyne principle. The technology consists of phase shifting,multifrequency heterodyne principle and stereo vision. Combination of phase shifting and heterodyne principle can make automatic phase unwrapping, stereo vision can accomplish stereo matching and points reconstruction automatically according to phase map after unwrapping. We have established a high-accurate 3D measurement system using heterodyne technology and stereo vision principle. The experimental results show that the system can accomplish complex free-form surface measurement and the data is complete and reliable.Secondly,3D visual Principle and Camera Calibration are discussed emphatically. On the basis of Zhang's plane calibration method, we conducted a series of experiments. Experiments show that the method is a high-precision camera calibration method.Finally filter process in grating measurement system is researched. We must pretreat images to remove noise after images are acquired, so that the effects of the noise on the entire system of measurement accuracy reduce to the minimum. This paper compares some of the methods between the spatial domain and frequency domain, finally adopts the two-dimensional Fourier transform(DFT) method for de-noising filter, and achieved good results.