Abstract: A Time Delay Integration technique is applied to an image sensor of this invention. A sensor part is constructed in such a way that diagonally-arranged photo-sensors are arranged periodically lengthwise and widthwise. The signal charge read from the photo-sensors of each line is transferred vertically to horizontal CCD shift registers. Each horizontal CCD shift register is provided on each line of the diagonally-arranged photo-sensors, and the horizontal CCD shift register outputs the signal charge to an A/D converter, which converts the signal charge into a digital signal. Thus, one A/D converter processes only a small amount of data, and the object can be scanned at high speed.

Abstract: A Time Delayed Integrator (TDI) sensor obtains images of a plurality of areas with the same pattern of an object of inspection such as a semiconductor wafer, and the obtained images are stored in an image storage part. The plurality of areas are designated in airs, and an image comparison part compares the images of the areas in each pair to detect a suspected pair including at least one possible defective area. A central processing unit (CPU) compares the images of the areas in the suspected pair with images of areas in other pairs to thereby find which area in the suspected pair is defective.