MISREGISTRATION/DISTORTION CORRECTION SCHEME

A registration system for compensating for distortion of a test printed circuit board relative to a stored reference in a printed circuit board inspection system is disclosed. Fiducial marks on the corners of the test board are compared with fiducial marks on the corners of the stored reference to determine relative distortion of the test board with respect to the reference board. This information is utilized to load a memory so that exposure pulses of a scanning CCD camera occur at intervals which compensate for distortion of the test board in the scanning direction x. The fiducial comparison information is also used to generate a gate on the occurrence of each exposure pulse to compensate for distortion of the test board in the y-direction. The exposure pulses are further utilized to generate addresses to a buffer memory storing the reference board to cause patches representative of the reference board to be read out of memory in registration with patches representative of the counterpart surface location of the test board to permit accurate real time comparison of the test board to the stored reference board.