| 摘要 |
A dollar bill (1) to be tested is illuminated by a pencil of rays (9) of ultraviolet light having an angle of 45 DEG . A first part PHI 1 of the light reflected by the bill and having a wavelength lambda < 400 nm is detected in a photodetecting device (10). A second part PHI 2 of the light passing through the bill and having a wavelength lambda = 340 nm, approximately, is detected in a photodetecting device (13), and a third part PHI 3 of the light emitted from the bill by the effect of fluorescence and having a wavelength in the range 426 < lambda < 446 nm is detected in a photodetecting device (16). The three parts of light PHI 1, PHI 2, and PHI 3 are compared in an electric circuit to predetermined values referring to a genuine bill. If disagreement exists between at least one of the measured values and the predetermined values, a signal is emitted indicating that the bill is forged. The possible organic differences in the manufacturing material between a tested bill and a genuine bill may be proved with certainty, and thus whether the tested bill is genuine or forged.
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