PRINTING SUBSTRATE INSPECTION SYSTEM

PURPOSE:To prevent a defective inspecting error by using a photomask original plate itself as a reference. CONSTITUTION:On a base board 1, a photomask original plate 2a and an inspected printing substrate 2b as a reference are mounted, and scanned respectively corresponding to optical sensors 3a and 3b. For a detecting signal, in respective Amps 4a and 4b, a level is adjusted, digitized by A/D-converters 5a and 5b and next, comes to be a pulse (bit) column by binarization circuit 6a and 6b. In noise removals 7a and 7b, the bit in the adjoining constant scope is all '0,' or is a decimal of a constant value or below, and then, this is removed as a noise. Noise removed data are the inspection data. Next, for the inspection data to the photomask original plate, a degenerating quantity DELTA1 is subtracted in a data degenerating processing 8 and the reference data are obtained. Next, to the reference data and the inspecting data of the inspected printing substrate, characteristic extractions 9a and 9b are executed, both are compared 10 and at the time of the disagreement, a defective signal is outputted 11.