Defect inspection system.

摘要

A defect inspection system for scanning a surface of an inspected material to pick up image signals, followed by processing the signals to detect any defects. In order to eliminate noises due to background pattern of the inspected material, signals are processed through a density converter so that the densities within a certain range containing the center density corresponding to the density of the background field are converted to have a constant level. In order to clarify the outline of the signal portion showing a defect, spatial-filtering is effected by using a differentiation filter. The direction along which differentiation is effected, and the mask size of the differentiation filter may be changed to effect optimum spatial-filtering for the particular texture of the inspected material. A threshold may be used not to detect defects within an area (joint area or marginal portion) from which any defect are to be detected. Plural data sets may be stored in a memory to select a proper data set for processing the signal under an appropriate condition, each data set including the density convertion table, the directivity and size of the differentiation filter, and other parameters including the threshold.