| 摘要 |
PURPOSE:To make it possible to measure color purity with high accuracy on phosphor dots as an object by measuring the gap direction and quantity to the phosphor dots based on the position of the part of an outline point row relating to brightness less than the average brightness and the rate occupying in the whole outline. CONSTITUTION:Phosphor dots on a color display tube 14 picked-up in an enlarged state by a camera 13 are taken-in by a picture memory 5 while the outlines of the phosphor dots are extracted and average brightness near the outlines is calculated every outline point along the extracted outlines simultaneously in parallel or after its end. Having said average brightness as a peripheral part brightness distribution, and subsequently a mediunfiltering treatment is performed in order to remove a noize of the dot peripheral part brightness distribution followed by calculation of average value of the dot peripheral part brightness distribution. In an outline point having brightness under the average value of the dot peripheral part brightness distribution found in this way, an electron beam is not properly radiated on a phosphor dot so that gap direction and a quantity to the phosphor dots of the electron beam, namely color purity can be calculated by the position and quantity of 'lack' detected.
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