1. A motion vector generation apparatus comprising: an image acquisition unit to capture and hold a plurality of time-series images; a target point determination unit configured to determine a target point at a sub-pixel level in one of the plurality of time-series images held in the image acquisition unit; a corresponding point search unit configured to search for a corresponding point at a sub-pixel level corresponding to the target point, the corresponding point being in an image contained in the plurality of time-series images in the image acquisition unit, the image being different from the one of the plurality of time-series images in which the target point is determined; a motion vector calculation unit coupled to the image acquisition unit and coupled to a central processing unit and memory storage, and configured to calculate a motion vector according to the target point and the corresponding point; wherein, after the corresponding point search unit searches the corresponding point, the target point determination unit determines the corresponding point searched at a sub-pixel level as a new target point in the searched image, and the corresponding point search unit searches for the corresponding point at a sub-pixel level corresponding to the new target point determined at the sub-pixel level, wherein the corresponding point is in a time-series image that is different from a time-series image in which the new target point is determined; and wherein the determining the corresponding point searched at a sub-pixel level as a new target point in the searched image by the target point determination unit, and the searching for the corresponding point at a sub-pixel level corresponding to the new target point determined at the sub-pixel level by the corresponding point search unit are iteratively repeated; and wherein the motion vector calculation unit sequentially calculates motion vectors based on each target point and each searched corresponding point corresponding to the target point in the one of the plurality of time-series images, wherein each target point and each corresponding point is iteratively determined or searched.