1. An inspection system comprising: a light source; a stage mounting an objected to be inspected; an optical system capable of changing a distribution of reflected or diffracted light component from the object; and a one- or two-dimensional optoelectric conversion image sensor to image the object through the optical system; wherein the stage and the image sensor are scanned relative to each other to obtain an image of the object and, based on the image, the object is inspected for defects, said inspection system further comprising a sensor output correction unit to correct a contrast in a viewing field of the image sensor.