| 摘要 |
PROBLEM TO BE SOLVED: To measure the fluctuation of color tone under a highly accurate and stable state, without requiring a highly accurate timing required for conven tional repetitive spot detection, by detecting the spectral quantity of a print image region printed on one or both sides of a web print sheet continuously over a specified length of a traveling sheet and making a decision whether a fluctuation of color tone is present or not based on the integrated value of the spectral quantity. SOLUTION: The inventive apparatus comprises means 12 for measuring the length of a traveling web print sheet 1, means S for measuring the spectral quantity a pattern printed on the sheet, means 13 for integrating the spectral quantity measured over a specified traveling length L, means 14 for calculating the difference between the integrated spectral quantity and a reference integrated spectral quantity, and a print color tone GO/NO-GO decision means 15 for making a decision whether a fluctuation of print color tone is present or not based on the calculated difference. |
