Research On Structured Light Binocular Stereo Vision Technology For Large Dimension Parts

With the rapid development of China’s large-scale equipment manufacturing industry,the measurement of the geometric quantities of large size parts is needed in the fields of aerospace,shipbuilding and road traffic.However,most of the existing measurement methods adopt contact measurement,which can not be directly used to effectively detect large size parts with complex shapes.The contradiction between the existing large size measuring level and the measuring equipment and the large size complicated shape surface parts is increasingly prominent,which has become the bottleneck restricting the rapid development of China’s large size equipment manufacturing industry.This paper proposes a structured light stereo vision measurement method based on the combination of anamorphic lens and binocular stereo vision for the characteristics of large size parts with large overall dimensions and a certain aspect ratio.First,the structure and basic working principle of the measurement system are introduced.According to the imaging characteristics of the measured object and the measurement requirements of the system,the selection of the light source,camera,lens,anamorphic accessories,projector and calibration object is given.On this basis,an experimental platform for measuring large-size parts was built.Then,based on the ordinary perspective lens and wide-angle lens,the imaging mathematical model of the anamorphic lens is studied.According to the anamorphic imaging model,a camera calibration method based on the anamorphic imaging model is proposed,which includes researching the calibration scheme,developing the calibration target,and determining the calibration process.The research results show that the anamorphic imaging model is more suitable for the calibration of anamorphic lenses than the pinhole imaging model,and the calibration accuracy has been greatly improved.Secondly,for the problem of three-dimensional matching,by projecting a binary-coded checkerboard pattern onto the large-sized part under test,the encoded image is decoded to find matching points in the left and right image planes.In the decoding process,the coded image is thresholded to extract the feature points of the feature area,and the corresponding code value of the point in each coded image is obtained.The point that meets the same code value is the matching point.Finally,for the problem of camera calibration in a large field of view,a method of constructing a three-dimensional calibration target using a planar calibration plate is proposed.A 2×1.5m~2 large 3D calibration target was constructed,and experiments verified that the constructed large 3D target can achieve accurate camera calibration.After completing the work of camera calibration,image processing,stereo matching,etc.,using the built experimental platform,large-scale parts were tested to verify the accuracy of the theory and method proposed in this paper.