| Summary: | 碩士 === 元智大學 === 工業工程研究所 === 88 === In this research, we propose a blur measurement for inspection applications of CRT focus and print quality. The amount of blurring is evaluated by the ratio of object region is as image. A focused object has sharp edges and results in small area ratio, whereas a defocused version of the same object has blurred and spreading edges and yields large area ratio.
In CRT focus inspection, the monitor displays a predetermined line pattern to a machine vision system, the area ratio of the lines in the patterned image is then calculated using the moment-preserving method. The vest focus of a monitor under inspection is adjusted so that the area ratio is a minimum. Since the ideal area ratio of a given line pattern can be determined theoretically, the proposed quantitative representation of blur can be used as an absolute measure of the comparison of focus quality between different monitors.
In print quality inspection, the number of characters in a printing matter varies from images to images. The image pattern to be inspected cannot be predetermined. Therefore, the amount of blurring is measured by the edges of characters rather than by the whole region of characters in the image. For each edge pixel with high gradient magnitude, the area ration within a mask of the size equal to the line width of characters is calculated using the moment-preserving method. The mean area ratio of all high gradient pixels is then used as the quantitative measure of print quality. Experimental results have shown that the proposed blur measure is effective and stable for the inspection of CRT focus and print quality.
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