Patent ID: 6909798

Claim:
A method of erasing repeated patterns in a dark/light image obtained by image pickup of a subject of inspection, when identifying defects present in a repeated pattern in the subject of inspection, comprising: detecting a reference pixel in the obtained image; assigning a comparison pixel at a predetermined distance from the reference pixel, the distance being determined in accordance with the pattern pitch of the repeated patterns in the dark/light image; obtaining a plurality of density differences between said reference pixel and each of said comparison pixels, wherein when a density of the reference pixel is larger than a density of the comparison pixel, a density difference is positive, and when the density of the reference pixel is smaller than the density of the comparison pixel, the density difference is negative; determining the density difference that is closest to 0 as a specific density difference; and applying said specific density difference to a reference density of the image, thereby erasing the repeated patterns in the dark/light image to identify defects in a pattern-erased image.