非固定相机旋转图像的数字散斑相关计算研究

Study on image rotation of digital image correlation measurement with unfixed camera

非固定相机数字散斑相关方法拍摄待测物体表面的目标图像时,所拍摄的目标散斑图像相对于参考散斑图像可能产生位置移动及图像旋转。通过辅助定位的相机标定方法可以计算出被测物体表面与相机的相对位置,但无法获得散斑图像在平面内的旋转角度。数字散斑相关方法对图像旋转较为敏感,随着旋转角度的增加,目标子窗口与参考子窗口的相关性迅速降低。研究图像旋转角度对数字散斑相关方法计算精度的影响,分析相关性随旋转角度降低的原因。对相关搜索方法进行相应的改进,在搜索目标子窗口时增加对子窗口旋转角度搜索,在计算参考图像中子窗口位移量的过程中,同时计算了其旋转角度,从而降低图像旋转的影响,提高数字散斑相关方法的计算精度。

The target speckle image may produce position movement and image rotation relative to the reference speckle image when the images of the surface are captured with non-fixed camera for digital image correlation method.The camera calibration method can be used to calculate the relative position of the object surface and the camera,but the rotation angle of the speckle image in the plane cannot be obtained.Digital image correlation method is sensitive to image rotation.The correlation between target subset and Reference subset is reduced rapidly with the increase of rotation angle.The effect of image rotation on the calculation precision of digital speckle correlation method is studied and the reason of correlation decreases with rotation angle is analyzed.The rotation angle and the displacements are calculated at the same time in order to improve the accuracy of the method.