Research On Camera Calibration Technology For Large Field Of View Based On The Large Aviation Components Measurement

With the rapid development of aviation industry in our country,there is an increasing application for CFRP.As core bearing-load components,the production and assembly quality of large CFPR aerospace components decides the service performance of plane directly.In order to guarantee the production and assembly quality with low injury,high precision and high reliability as well as improve the digital production level,high-precision measurement of surface and physical size of large CFPR parts is indispensable,so it's meaningful to research a high-precision and high-efficiency measurement method at the scene of the aerial survey.Binocular stereo vision is a non-contact,high-precision,high-efficiency,high-flexible and convenient measurement method.A vision measurement method is proposed based on laser scanning and absolute tracker to achieve the parameters measurement of the large CFPR parts in this paper.Camera calibration is the first step of binocular stereo vision measurement system,its precision directly affect the final accuracy of measurement.In order to solve the scene problems include large field of view,bad distortion,complex environment,this paper do some research in camera calibration technology for large field of view.The main research content is as follows:1.Do some review and analysis about current camera calibration methods.In this paper,a binocular camera calibration method based on the collinear constraint of four corners for large field of view is proposed.The method is used to separate the measurement space by the idea of parameter separation calibration.Some calibration control points are arranged close to the field of small distortion to solve the initial value of the camera parameters while four collinear constraints are arranged close to the field of bad distortion to solve the initial value of the distortion coefficient.Make a global optimization of calibration parameters to minimize the reprojection error.The method can achieve full field camera calibration of large field of view through a single photo quickly.2.The influence factors of the calibration points distribution on the calibration accuracy are analyzed.A calibration control field is built using the laser tracker and the vision measurement system.The depth of the field,number and spatial distribution of the calibration points are analyzed qualitatively.The results are used to guide the calibration layout and improve the calibration accuracy.3.A portable three-dimensional calibration device suitable for aerial field measurement is designed.The standard ceramic ball is used as the calibration characteristic element,and a automatic fast matching feature recognition method is proposed according to the gray scale distribution of the standard sphere and the differential gradient structure.4.Calibration accuracy experiments was carried out in the laboratory and the scene of the aerial survey based on the calibration method and the calibration device.The results show that the average deviation of the one-dimensional target reconstruction is 0.1147 mm in the laboratory environment,the average deviation of the measured coordinates is 0.13 mm,especially the average deviation in the direction of depth of field is only 0.1156 mm at the scene of the aerial survey while FOV is 2.0m ? 1.5m,which satisfies the accuracy requirement of the aerial field measurement.