1. An image restoration device adapted to receive an image signal, the device comprising: an image filtering unit adapted to filter the image signal and output the filtered image signal; an image mixing unit adapted to receive the image signal and the filtered image signal, to calculate a weighted average of the image signal and the filtered image signal, and to output the weighted average as a restored image signal; and a weighting factor calculating unit, the weighting factor calculating unit being adapted to receive the image signal, to calculate a local variance of pixels in the image signal, to calculate weighting factors for each of the pixels based on the local variance of each of the pixels, and to output the weighting factors to the image mixing unit, wherein the weighting factor calculating unit is adapted to calculate the local variance of each of the pixels according to an equation v ⁡ ( x , y ) = 1 M ⁢ ∑ ( x , y ) ∈ S ⁢ ⁢ ( f ⁡ ( x , y ) - m xy ) 2 where (x, y) corresponds to a coordinate of the respective pixel, v(x, y) corresponds to the local variance of the respective pixel (x, y), S corresponds to a predetermined region to which the respective pixel (x, y) belongs, M corresponds to a number of pixels which belong to the region S, f(x, y) corresponds to an image value of the respective pixel (x, y), and m xy corresponds to a local mean of the region S.