1. An image processing system for generating an interpolation frame to be inserted between one frame and another frame, comprising: a motion vector candidate selection unit that selects predetermined motion vector candidates one after another; a differential image generation unit that calculates a difference between a pixel in said one frame and a pixel in said another frame specified by a pixel in an interpolation frame and a motion vector candidate selected by the motion vector candidate selection unit, and generates a differential image where the difference is assigned to a pixel at the same coordinates as the pixel in the interpolation frame; a binary image generation unit that generates a binary image where the differential image is binarized; an area image generation unit that generates an area image where a pixel value of a pixel applicable to non-difference in the binary image is set to an area of a region where the pixel is linked and a pixel value of a pixel applicable to difference in the binary image is set to a given value; a motion vector identifying unit that identifies a motion vector candidate with which a pixel value of a corresponding pixel in the area image is the largest as a motion vector with respect to each pixel in the interpolation frame; and a pixel value determination unit that determines a pixel value based on a pixel in said one frame and a pixel in said another frame specified by a motion vector identified by the motion vector identifying unit with respect to each pixel in the interpolation frame, wherein the motion vector identifying unit determines, when an area image is generated, whether a largest value of a pixel value is updated or not with respect to each pixel of the area image, and, when the pixel value is updated, updates a motion vector of a pixel in the interpolation frame by setting a motion vector candidate selected during generating the area image as a motion vector of a pixel in the interpolation frame at the same coordinates as a pixel in the area image whose pixel value is updated.