PURPOSE:To detect the recognition parameter with higher accuracy than the resolution of an input image at the time of generalized Hough transform. CONSTITUTION:With respect to a gradation image, a distance (rj) of a feature point and a reference point and an azimuth phij are stored in an address position of a reference table and from the gradation value data (rj) and the phij value of each picture element (x, y) of the gradation image, signals (x), (y) of an address generator 2, a signal theta of an angle generator 10, and a signal (s) of a size fluctuation correction rate generator 11, the address transform of x+ sXrjocos(theta+phij) and y+sXrjsin(theta+phij) is executed by an address transform part 5. A reciprocal ratio of a distance between a candidate point (xG', yG', thetas) and the corresponding point of an adjacent address is accumulated in an adjacent address position on a parameter accumulation memory 8 by an accumulation arithmetic part 7, a temporary maximum point being above a prescribed threshold is determined from accumulated data, the accumulated data of an adjacent address in the periphery of the maximum point is inputted, an interpolating operation is executed and a position of the maximum point is determined by a parameter determining part 12.
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