Patent ID: 7142708

Claim:
A defect detection method comprising the steps of: picking up a sample as a target to be inspected to obtain an image of the sample; comparing the image obtained from the picked-up sample with a stored reference image to calculate the quantity of displacement of the sample image relative to the reference image; using information about the calculated displacement to determine a difference between the sample image and the reference image by comparing the images; and detecting a defect of the sample judging from the determined difference; wherein in the step of detecting, the defect is detected by changing sensitivity according to contrast of the sample image or that of the reference image and comprises the steps of: according to a contrast between the sample image and the reference image, correcting brightness so that brightness of at least the sample image or the reference image is adjusted to that of the other; determining a difference image between the images, the brightness of which has been corrected; and detecting a defect judging from the difference image.