Research On 3D Optics Measurement System Of Close Range Photogrammetry Applied In Reverse Engineering

For recent measurement which involves large volume, complicated structures and free form surfaces targets, the combination of close range photogrammetry and structured light grating projection measuring is the most fast and efficient method. This combination method features with both the high efficiency of structured light method and the elimination of cumulative errors profited from photogrammetry. The photogrammetry establishes a coordinate group of uncoded points which forms the reference set for merging point-clouds acquired by the structured light measurement method.So, the optics measuring system requires two kinds of artificial points to be pasted to the surfaces of the measured objects. One kind of artificial points can be detected by both photogrammetry and structured light method, and there are no fixed code on them, which are called uncoded points and the center positions of uncoded points are need to be specified. The other kind of artificial points have fixed codes and can be detected by photogrammetry only, and their surface patterns are different from each other, which are called coded points. Among them, the function of the uncoded points is the reference of sewing the point-clouds between different images, and the function of the coded points is to match the uncoded points in images and acquire the space information of them.Along with the process of photogrammetry, the range of this research is showed as the following:1. In the part of image processing, this thesis utilizes a series of image processing techniques to turn the original images into binary images with a little interference using MATLAB Image Processing Toolbox (IPT)2. The thesis recognizes coded points by SVM (Support Vector Machine) method with Zernike moments feature vectors extracted from the coded points in images. The method is based on the Hamming distance to determine the dimensions of Zernike moments feature vectors.3. The regulation for deployment uncoded points was prescribed and The Delaunay triangle grid of each image was generated based on the space topology. The matching result is precise based on invariable Delaunay triangle grid. 4. DLT method was used to calculate the projection matrices of images and 3D coordinates of uncoded points. Overdetermined Linear Equations are solved by least squares method.