1. An pose estimation system for performing object pose estimation by comparing an input image with a three-dimensional object model, the pose estimation system comprising: an pose candidate decision unit for generating at least one pose candidate; a comparison image generation unit for generating, according to the generated pose candidate, a plurality of comparison images close to the input image, while projecting the three-dimensional object model to a two-dimensional image; a first sharpness extraction unit for extracting a first sharpness amount reflecting the sharpness from each of the plurality of comparison images; a weighted difference calculator for calculating a plurality of weighted differences by weighting the first sharpness amount to the difference between the input image and each of the comparison images; and a determination unit for selecting a comparison image having the smallest weighted difference among the plurality of weighted differences and estimating an optimal pose based on the selected comparison image.