| 摘要 |
The apparatus has an illuminating device for illuminating sheet material with clocked excitation light. Both during the light phase of clocked excitation light and during the dark phase of clocked excitation light a sensor detects an intensity of the light emitted by the sheet material in each case. In an evaluation device an intensity of fluorescently emitted light and an intensity of phosphorescently emitted light are derived from the intensities detected in the light phase and in the dark phase of clocked excitation light. In order to ensure long preillumination with high intensity, the sensor preferably detects the intensities of emitted light within, and toward the end (in the transport direction) of, the area of the sheet material illuminated by the illuminating device. Additionally the illuminated area of the sheet material is selected to be so great that it is a multiple of the desired resolution. |
