High-precision Solar Image Registration Using Normalized Cross-correlation and Intensity

Many solar physical studies strongly rely on co-temporal and co-spacial images. Due to the observed images are usually taken by different telescopes, they have different scales and rotations. Therefore, it is important to accurately align the images of different observations. But, the traditional method with cross-correlation has several limitations and causes the registration accuracy is fairly low. In this paper, we proposed a novel coarse-to-fine solar image registration method in combination with normalized cross-correlation and intensity-based methods. Firstly, we use the maximum coefficient of the normalized cross-correlation to locate the position of the different resolution images for coarse registration. Then, fine registration parameters, i.e., scale, rotation, and shift, are calculated through an intensity-based method. Finally, the low-resolution image is aligned to the high-resolution image according to the parameters obtained by the intensity-based method. We first completed a simulation experiment to demonstrate the accuracy of the method. Two pairs of images with different scales and rotations taken by the different instruments are selected to further evaluate the robustness of the method. The registration results demonstrate that the proposed method holds a high registration accuracy.