Error correction of glass mediums in high-temperature digital image correlation deformation measurement

In order to correct the measurement error caused by a glass medium in high-temperature deformation measurement, we take a glass medium as a part of the camera calibration model. Based on photogrammetry technology and digital image correlation, a binocular camera calibration method in a complex environment is proposed and applied to high-temperature deformation measurements. Firstly, aiming at the calibration difficulty caused by the poor image quality in complex environments, the camera imaging model with distortion correction is adopted to achieve binocular camera calibration by bundle adjustment camera calibration method, which improves the success rate and stability of calibration. Secondly, to solve the problem of low calibration accuracy of binocular cameras in complex environments, the influence of lens focal length, ambient light interference and the distance between glass and camera on the calibration results are analyzed, and the optimal calibration parameters are given, so that the calibration reprojection error is reduced from 0.832 pixels to 0.132 pixels. Finally, the measurement error of the calibration method with and without glass is compared by using the measurement environment with a glass medium, which proves that this method can greatly reduce the measurement error. The test results show that this method can effectively reduce the measurement error of a displacement field caused by glass medium in a high-temperature environment. The maximum decrease of measurement error of the displacement field in the X, Y and Z axes is 70.16%, 76.51% and 40.05%, respectively. The method in this paper can achieve high-precision camera calibration in complex environments, and has good calibration stability. It is an effective way of realizing accurate measurement of high-temperature deformation.