1. A fast method of super-resolution processing for speeding up a super-resolution processing that estimates a high-resolution image from multiple low-resolution images with displacements, the method comprising: registering pixels of the multiple low-resolution images to pixels in the high-resolution image; determining a mean observed image by calculating a mean pixel value of a plurality of pixels from among the pixels of the multiple low-resolution images registered to the pixels in the high-resolution image; determining a weighted image using pixels of the multiple low-resolution images that are registered to the pixels in the high-resolution image; determining a PSF using a point spread function; estimating said high-resolution image by using an evaluation function obtained by adding a constraint term based on prior information about said high-resolution image to a weighted sum of squares of a difference between a result of a convolution integral of said high-resolution image and said PSF image and said mean observed image and a differential of said evaluation function with respect to said high-resolution image; and calculating said weighted sum of squares based on said weighted image, wherein said fast method of super-resolution processing is performed by a processor.