1. An image processing method, which is able to enhance resolution of images taken by an imaging instrument, comprising steps of: a) separating the input multi-spectral image into monochrome images; b) estimating point spread function (PSF) for each monochrome image; c) generating neighboring pixel correlation coefficients (NPCC) from the PST for each monochrome image; d) applying Discrete Fourier transform (FT) for each of the monochrome images; e) calculating Fourier components for each pixel of the monochrome image; f) generating a neighboring-pixel-optical-transfer-function (NPOTF) using the NPCCs and periodical boundary conditions for each Fourier component; g) setting a threshold for the NPOTF; h) modifying the NPOTF with the threshold; i) generating new Fourier components by dividing each of the old Fourier components by the modified NPOTF respectively; j) generating new monochrome images by performing reversed Fourier transform using the new Fourier components; k) repeating steps from b) to i) with different NPCCs and different threshold until the image becomes sharpest with lowest noise; l) adjusting brightness of each monochrome images; and m) combining the new monochrome images into a new output multi-spectral image.