| 摘要 |
In a first embodiment of a material detection system according to the invention, a security document is disposed in an optical path between an infrared light source and image sensor so that the imaging system comprising the infrared light source, image sensor and associated controller determines characteristics of material compositions of a document based on transmissivity characteristics of a document. In a second embodiment, a radiation wavelength sensitive additive which emits energy in a second band of wavelengths when radiated in a first band of wavelengths is incorporated in a security document and detected for by an imaging system which detects for emitted radiant energy in the second band of wavelengths. In a third embodiment of a material detection system, the manufacturing of documents of various styles is controlled so that the various styles of documents exhibit similar reflectance characteristics under illumination by a predetermined narrow band source despite exhibiting dissimilar reflectance characteristics under white light.
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