Detection of Shadow Mask Defects Using Periodic Hole Placement

This paper presents an efficient image analysis methodology which can detect the very small hole defects reliably and rapidly from shadow mask. In fact, shadow mask line image data can be adjusted to be periodical with the period of an integer number. The inspection method mainly depends on the fact that a small defect can be significantly emphasized in terms of the comparison between image pixels departed by the period. In this paper, this comparison is implemented as FIR digital filtering algorithm, which can be rapidly processed by DSP chip. In terms of high speed line image sensing and fast algorithm by DSP, the whole inspection scheme sufficiently supports real time shadow mask handing. From the experimental results, this scheme shows a reliable inspection capability for all types of individual hole defects.