Measurement Techniques, Based On The Visual Coordinates Of The Grid Marked

After systematic researches on computer vision coordinate measurement techniques, this paper proposed a Four-eyed Vision Coordinate Measurement Model (FVCMM) based on Rectangular Grid Mark. A Four-eyed Vision Coordinate Measurement System (FVCMS) was constructed based on this model. It was firstly applied to strain measurement during the process of metal plate deformation and gained some success.In the FVCMM proposed in this paper, a special designed rectangular grid mark is required to be attached to the surface of the object. The grid nodes on the surface are treated as measurement marks. The 3-Dimensional coordinates of these grid nodes are calculated through processing the grid images which captured by four cameras.This paper paid most efforts on the algorithms of image processing and stereo corresponding of the grid nodes concerning the special objects - grid images. Some applicable algorithms are proposed or improved. The FVCMS employed four cameras as image acquisition source. This paper built a theoretical model of this kind of measuring method and designed coordinate calculation algorithm.In summary, the research result described in this paper includes four parts.1. Camera calibration and 3-Dimensional coordinates' calculation. Regarding the precision requirement of the system, a simple linear camera model is selected and a calibration method based on grid image is proposed. Based on linear camera model, this paper constructed a stereo vision model and designed an algorithm for 3-Dimensional coordinates' calculation through four cameras.2. Image acquisition and processing. A hardware independent image acquisition interface is designed. Aimed at grid images, a reasonable image processing procedure is employed, including segmentation, binarization, close, thinning and sub-pixel image processing technique based on B-spline interpolation. The algorithms employed in this paper are redesigned or improved for grid images. For example, an adaptable moving window gray scale threshold image segmentation method is proposed originally, a parallel template matching thinning algorithm is improved greatly, a sub-pixel image processing algorithm based on B-spline interpolation is present independently.3. Grid nodes extraction and corresponding. Based on former researcher's works, an algorithm for grid nodes extraction from thinned grid image is present. A brand new method of grid nodes corresponding is proposed based on 2-Dimensional Neighbor Node Table.4. Coordinate data visualization. A general 3-Dimensional coordinate data visualization model and a general post-processing data interface are designed for extension of the system's function.