Optical Test System
Original Publication Date: 1989-Jan-01
Included in the Prior Art Database: 2005-Jan-27
A two-stage electro-optical system used for inspection of printed circuit patterns is disclosed. The two-stage test process consists of a full reference test for suspected defective locations followed by a rules test that inspects localized areas around the suspected defects. The second level rules test eliminates up to 90% of the false calls made by the first level data test while confirming all of the real defect locations. An image is scanned into an NxN memory with a number of bits per pixel representing shades of gray. The image is turned into an NxNX1 (binary image) through use of a special thresholding algorithm. The binary image is correlated to a reference data pattern within +/- 1 pixel for the NxN image.