Patent Document ID: 20030031356
Application ID: 10216320
Patent Status: 0

Claim One:
1. A pattern inspection apparatus for generating a difference map representing differences between an inspection image and a reference image by comparing the inspection image and the reference image pixel by pixel, and detecting defects in an inspected object based on the difference map, the inspection image being a multivalued image obtained by photographing the inspected object with a specific pattern formed thereon and the reference image being a multivalued image representing the specific pattern as a reference standard, the pattern inspection apparatus comprising: a marginal distribution feature value calculation unit for sequentially focusing on each pixel in the inspection image and a pixel at a corresponding position in the reference image, and calculating a first marginal distribution feature value indicative of spatial variation in pixel values in a neighborhood of the focus pixel in the inspection image, and a second marginal distribution feature value indicative of spatial variation in pixel values in a neighborhood of the focus pixel in the reference image; a selection unit for selecting the inspection image focus pixel or the reference image focus pixel having less spatial variation in neighborhood pixel values as a tolerance pixel based on the first and second marginal distribution feature values, and selecting the other focus pixel as a target pixel; a tolerance range calculation unit for calculating as a tolerance range a range of pixel values to be used as a value of the tolerance pixel allowing error in a coincidence evaluation of the inspection image focus pixel and reference image focus pixel; and a comparison unit for calculating a difference value indicative of a difference between the target pixel and tolerance pixel by comparing the target pixel with the tolerance pixel within the tolerance range, and storing the difference value to a specific memory; the difference map being created by writing the difference values to the specific memory.