Patent ID: 7421109

Claim:
A pattern inspection apparatus comprising: imaging optics which forms an optical image of a pattern formed on a plate to be inspected based on designed pattern data; a detected pattern data generator which detects the optical image to generate detected pattern data; a reference pattern data generator which generates first reference pattern data from the designed pattern data, the first reference pattern data being a reference data corresponding to the detected pattern data; a first comparator which compares the detected pattern data with the first reference pattern data to detect a defect of the pattern formed on the plate; a first memory which, when there are a plurality of repeated pattern areas on the plate, stores pattern data obtained by detecting an inspection area, which is one of the plurality of repeated pattern areas, as second reference pattern data; a second comparator which compares the detected pattern data with the second reference pattern data to detect the defect of the pattern formed on the plate; and a computer which reads an arrangement, a number, a dimension and a repeated pitch of the plurality of repeated pattern areas from the designed pattern data, and stores the inspection area as a basis of the second reference pattern data.