A defect inspecting apparatus for inspecting a defect on an object to be inspected on the basis of comparison between a pattern at a first position and a pattern at a second position on the object to be inspected having repeated patterns. The apparatus includes: an imaging optical system having an image pick-up element for picking up an image of a substantially entire region or a divided region of the surface of the object to be inspected; a moving system for relatively moving the imaging optical system with respect to the object to be inspected; a movement controlling system for controlling the moving system such that a positional relationship of the pattern at the first position with respect to pixels of the image pick-up element is made substantially identical to a positional relationship of the pattern at the second position after movement thereof with respect to the pixels of the image pick-up element; and a defect detecting system for detecting a defect on the basis of comparison of data on two images picked up by the image pick-up element before and after the movement.

The present invention provides a method and an apparatus for evaluating the surfaces of substrates for three dimensional defects. The present invention uses low-angled lighting positioned on opposite sides of the substrate. A camera positioned above the substrate captures two images thereof, one using the first light source and one using the second. The first and second images are subtracted from one another to create a third image. Camera data suggestive of three dimensional features is emphasized by subtracting the two images and can be evaluated. A fourth image may be created by selecting the minimum values between the first and second images on a point-by-point basis. The fourth image also provides useful information in evaluating three dimensional defects.