Research On Binocular Vision Measurment Techniques Based On Digital Image Correlation

In recent years,with continuous development of measurement methods,the optical measurement methods are becoming more and more widely used in many fields.Digital image correlation method is one of the optical measurement methods based on correlation calculation of the surface area of object under test,it also has the advantages of non-contact measurement,full field measurement and low requirements on measurement environment and so on.The three-dimensional digital image correlation method completes measurement by using a dual-camera or multi-camera measurement system,it can be used to measure the in-plane and out-of-plane displacements and deformations,reconstruct the three-dimensional topography of the surface of the object under test.Digital image correlation method can be widely used in industry,manufacturing,aerospace,defense and many other fields.The binocular vision measurement system based on digital image correlation method was analyzed,including calibration algorithm of measurement system,the research and improvement of image correlation calculation algorithm,the preparation and experiment of related software.The main research work is as follows:The imaging principle of binocular vision measurement system,the camera imaging model and the mutual conversion relationship between the four coordinate systems mentioned during the imaging process were studied.The basic principle of measurement system calibration was studied,including corner detection,sub-pixel correction algorithm,screening,sorting and the internal and external parameters calculation of measurement system based on the corner coordinates.An improved corner detection algorithm based on Harris algorithm was proposed,so that the problem of traditional algorithm needs to select an appropriate threshold manually is solved,and the automatic detection of corner points is implemented.Several integer pixel and sub-pixel correlation calculation algorithm were experimented,the measurement accuracy and speed were compared.The hill-climbing method was chosen as the basis of improved algorithm,a circular template based on polar coordinates system was used to complete the correlation calculation instead of the traditional rectangular template,which makes the binocular vision measurement system can be used to measure the rotational deformation.A binocular vision measurement system based on digital image correlation method was set up,a set of measurement algorithm software based on the algorithm has been completed.The feasibility of the improved algorithm proposed was verified by three-dimensional topography reconstruction of complex objects experiments,rigid body displacement measurement experiment and speckle pattern rotation measurement experiment.