1. An image patch tracker, including one or more processing devices, the image patch tracker comprising: a scale invariance index (SII) calculating unit including at least one of the one or more processing devices to calculate an SII based on a pixel value change with respect to a scale change for a registered image patch; and a scale characteristic deciding unit including at least one of the one or more processing devices to compare the SII to a threshold and to selectively determine the registered image patch to be one of a scale-invariant image patch, when the SII is less than the threshold, and a scale-variant image patch, when the SII is not less than the threshold.