Optical Inspection System
Original Publication Date: 1984-May-01
Included in the Prior Art Database: 2005-Feb-04
The system serves to automatically detect defects on a photomask, a printed-circuit board or the like which has printed patterns thereon. In this system, the defects on the printed patterns are detected by the fact that the printed patterns have regular outlines and the defects have irregular outlines. This system has two or three linear image sensor arrays which scan the patterns. A logical exclusive OR of the outputs of two of the arrays is taken. The signal widths of the exclusive OR represent the edges of the patterns and of the defects. The signal widths of the exclusive OR caused by the patterns have predetermined values. On the contrary, the signal widths of the exclusive OR caused by the defects are not equal to the predetermined values.