The relative motion between a camera and the scene will lead images to blur. By appealing to traveling wave equations, not only the restoration of motion-blurred images can be achieved, but also a criterion of objective quality assessment can be obtained for these restored versions even without any a priori knowledge of the original image. And most significantly, this criterion actually applies to any categories of image restoration methods as long as the image blur is caused by linear uniform motion, and with good sensitivity and consistency.