US Patent 7266232 Apparatus and method for inspecting pattern

An inspection apparatus (1) has an image pickup part (2) for performing an image pickup of a substrate (9), an operation part (4) to which an image signal is inputted from said image pickup part (2) and a computer (5), and the operation part (4) specifies an inspection image and a reference image from an object image acquired by the image pickup part (2). In the operation part (4), a region class to which each pixel of the specified inspection image belongs is specified on the basis of a corresponding pixel value of the reference image. In a comparator circuit of the operation part (4), a differential absolute value between each pixel of the inspection image and a corresponding pixel of the reference image is calculated and the differential absolute value is compared with a defect check threshold value in accordance with the specified region class, to perform defect check. The inspection apparatus (1) can thereby appropriately detect a defect in accordance with the region class to which each pixel belongs.