| 摘要 |
PROBLEM TO BE SOLVED: To detect a chromaticity value gradient at an actually appropriate cost and a rapid velocity by forming at least one infrared value from a scan signal in a near-infrared region and calculating the chromaticity value gradient from chromaticity coordinates and at least, one infrared value. SOLUTION: When a printing ink black is used together in the case of a chromaticity value gradient is to be detected, an input value calculated can be used for controlling a printer. Consequently, sheets 3 are measured not only in a visible spectrum region of about 400-700 nm, but also at least in a near- ultraviolet region. In the near-ultraviolet region, only the black of printing ink effects absorption in a magnitude of a rating value. Thus it is possible to selectively detect the influence upon a colored print by the printing ink black. The diffuse reflection spectrum of individual print pixels 4 is formed from a diffuse reflection value in the visible spectrum region, typically 16 diffuse reflection value in an interval of 20 nm and a diffuse reflection value in a near-infrared region. |
