Patent ID: 7305664

Claim:
A method of generating a dictionary for detecting a specified mark, comprising the steps of: inputting a dictionary image; generating a coordinate conversion table containing a list of corresponding coordinates between a predetermined XY coordinate and a predetermined polar coordinate for converting the inputted dictionary image into polar coordinates, the polar coordinates being expressed by a central distance to a predetermined center and a central angle, the coordinate conversion table further including a pair of F and D values corresponding to the XY coordinate, the F value being an integer by counting fractions equal to or over 0.5 as defined in an equation F=θ/U, where U=2π/Θ, the θ being the central angle in the polar coordinates, the Θ being a number of pixels in a Θ direction, the D value being assigned an integer from 0 to a predetermined number for the central distance in the polar coordinates; generating a polar coordinate image for the dictionary from the dictionary image based upon the coordinate conversion table; storing the coordinate conversion table and the polar coordinate image in the dictionary; rotating to reconstruct an image based upon the coordinate conversion table; and comparing the reconstructed image and specified mark candidates to determine the specified mark to identify a match.