Study On 3D Profile Measurement With Fringe Modulation

With the development of complexity of the products and aesthetic need, how to obtain the profile rapidly and precisely and how to optimize the products are research emphases in products design and manufacture. The profile measurement with fringe modulation is widely used because it has advantages of short scanning time, large measurement range and low measurement cost. The paper mainly researches on 3D measurement with fringe projection, and it includes moire measurement technique, phase modulation measurement, point clouds pre-processing, surface reconstruction and error analysis.The same two fringes are projected to the surface of the object, and the equal height lines are formed on the surface. The profile and height of the object can be obtained according to the distribution of the lines. The parameters of the real fringes are unchangeable, and the fringes are expensive. The virtual fringes with adjustable parameters are designed by software, and measurement system is built to realize moire measurement of the body, finally fringe image is optimized.Single fringe is projected to the surface, and fringe will be deformed by the profile of the surface, that is, the phase of the fringe will change. The phase of the deformed fringe is solved out by phase shifting method, and it is transformed to scattered point clouds by Winmoire software.For the holes among the point clouds, the polynomial filling method is used to realize the holes filling. The noise points near the boundary are deleted by circle selection method, and the points which are far from the fitting curve are eliminated. Uniform grid method and global clustering method are combined to realize point clouds simplification. Orderly triangular arrangement is implemented by constructing original triangle and triangle increasing, finally all the triangles are transformed to quadrangles corresponding to the weight factor.For a automobile part, fringe scanning, point clouds transformation, data pre-processing and surface fitting are utilized to perform rapid reverse engineering to implement prototype of the object. The error of surface-point clouds is obtained with Geomagic Studio software, and the method of increasing control points is used to reduce the error to meet the requirement of surface reconstruction.The results of the research can be applied in 3D detecting and rapid model construction of the free surface, and establish mathematical model compatible with current CAD/CAM system according to the measuring data of the existing products.