Research And Implement Of Interferential Moiré Based On The Technology Of Digital Image Processing

Moire interferometry is an optical measurement which is noncontact and has big measuring range, wonderful fringe quality, real-time whole field measurement and high sensitivity, so it can measure the physical quantities about the tiny displacement and strain field of the surface of specimen accurately and effectively.In recent years,one of the most remarkable characteristics of the development in moire interferometry recently is the application of the digital image process. This thesis studied the whole process about it and posts own solutions through the comparements and analysis of the common methods in each process, then programed a system software which has the functions of image grabbing and saving, fringe processing, displacement field and strain field calculating, results displaying, and so on. Whether the specimen meets the performances of the product can be judged by the result of the strain field.This thesis expounded the structure of the system, the flow of its hardware and software. According to the study of the characteristics of the moire and the analyse of each method of existing image filters, the most useful one is choosed. As the existing method in image segment is not so good in moire process, so a new area filling method is adopted. In order to improving the quality of the thinned fringe, the traditional method in fringe thinning is improved. Then a new algorithm of branch cutting is proposed, then the fringe is continuous and branchless. To make the result more accurate, the endpoints should be connected to the edge of the image, and each fringe should be different. For the purpose of having more data of the fringe orders, a new interpolation is used. And the curve fitting is mentioned to make the results more practical. To make the results more visually, the 3D(three dimensions) and 2D(two dimensions) are made to show the data of the displacement field and the strain field, so that the correspondence relationship between the pixel's coordinates and its fringe order can be observed more intuitively. Then it can be judged whether it satisfies the performance of it through the maximum and minimum of its strain field. The result indicates that the software made by the above methods can calculate its strain field quickly and effictively, so that it can supervise its production, save its cost and improve its quality. This system has simple operation, nice interface, convenient maintenance and practical value.