PURPOSE: To enable the measurement of the pattern area ratio of a panel without providing a measuring reference portion by comparing the quantity of reference reflected light from two reference measuring surfaces which are provided on measuring reference panels and have respective inking portion densities different from each other and the quantity of reflected light in a predetermined region within the pattern region of a panel to be measured.
CONSTITUTION: Measuring reference panels 27 and 28 are prepared apart from a panel 20 to be measured. The whole surfaces of the panels 27 and 28 are made as measuring reference surfaces 29 and 30 and the inking portion densities thereof are set to 0% and 100%, respectively, which are photoengraved. The quantity of light reflected from each of surfaces 29 and 30 are measured by a pattern area ratio measuring instrument and stored. Further, the instrument stores a measuring reference line thus obtained. On the other hand, a panel 20 to be measured that is also a panel for printing is provided with pattern region 21 that represents a pattern by dots of a variety of sizes and a non-pattern region 22 that constitutes a chuck portion to be mounted to a printing roller. The quantity of ink supplied to the panel 20 in printing depends on the pattern area ratios of regions (a)W(e) within region 21. Those pattern area ratios are obtained by the pattern area ratio measuring instrument by irradiating light and detecting a mean quantity of reflected light which is made to correspond to the measuring reference line. Thus, the region 22 can be reduced by removing measuring reference portions from region 22.
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