| 摘要 |
<p>A method is provided for forming a document adapted to have graphical information applied thereto which cannot be detected by the detectors of copying machines having spectral responses in the range of 350 to 600 millimicrons. This information can be detected by human eyes having spectral responses in the range of 425 to 675 millimicrons. A background is produced on a sheet of material and has a reflectance which is substantially 4% over the wavelength range of 325 to 525 millimicrons and increases to 13% at about 575 millimicrons. Thus insufficient reflected energy is available from the background to be detected by the detectors. The reflectance of the graphical information is about 5%. The invention also includes the sheet of material produced by this method.</p> |
