RAPID PATTERN INSPECTION OF SHADOW MASKS BY MACHINE VISION INTEGRATEDWITH FOURIER OPTICS

We present a machine vision inspection method that is specially devise d to detect defects on shadow masks. This method incorporates Fourier optics to capture only irregular defects in real time by blocking out the periodically repetitive pattern of normal mask holes using a pinho le type spatial filter under coherent illumination. In addition, a fas t defect-detection image processing algorithm efficiently suppresses u ndesirable background noisy images. Experimental results prove that th is method provides a detection capability of 500 mu m(2) for the least defect size. (C) 1997 Society of Photo-Optical Instrumentation Engine ers.