In a parallel computation of a Hough transform of an array of input data values, the transform space of the Hough transform is partitioned dynamically or statically into a number of sub-spaces. The array substrate reduces the number of masks typically used in the fabrication process so that reliability is enhanced and the cost is reduced over the conventional device and method. After grinding of the whole back surface, a region of the back surface corresponding to the device region on the wafer surface is ground to form a concave portion having a predetermined thickness, so that a ring-like reinforcement portion is formed about a periphery of the concave portion, such that the wafer is easily handled in a subsequent step or in wafer carrying between respective steps. The central case has openings at either end when the lid is closed and grooves inside a portion of the central case near each opening.