Determination of geometric stability of glass substrates using machine vision

The stability of glass substrates is an important concern for the flat panel display industry. High-resolution displays have very tight geometrical requirements and alignment of the various display components is critical if good performance is to be obtained. Prior to development of manufacturing processes for these displays, it is necessary to determine how glass substrates change during the various processing steps. This paper describes a system to measure electrode patterns before and after critical processing steps for color plasma panels. The electrode patterns, which are made of thin-film gold, are a series of parallel electrodes. In order to measure electrode locations, a vision system consisting of an X-Y stage, a video camera, a frame grabber, and PC-compatible computer was used. Images captured with this setup were processed to minimize the effects of noise and improve accuracy. A gray-scale interpolation technique in which the centroids of the electrodes are calculated was used to enhance measurement resolution.