Patent ID: 6595427
Filing Date: 2003-07-22
Classification: G06K

Abstract:
A method of retrieving information encoded as a function of a surface dimension and thickness of at least one of a plurality of materials, said materials being capable of mildly absorbing radiation over a range of infrared wavelengths and substantially non-absorbing in the visible wavelengths, deposited on a medium or intertextured with a base medium, comprising the steps of:scanning at least one of a plurality of sources of radiation over the medium and material disposed thereon, wherein said sources emit infrared radiation over a range of wavelengths and wherein a portion of said radiation is reflected or transmitted from the medium and material disposed thereon, said reflected or transmitted portion having a variable intensity over the scan, a variation of said intensity being a function of infrared radiation absorption or transmission characteristics of the medium and material and the thickness and surface dimensions of the material disposed on the medium; collecting the reflected or transmitted portion of the radiation at each of a plurality of select wavelengths, from the range of wavelengths emitted by the at least one of a plurality of sources of radiation; converting said collected radiation at each of the plurality of select wavelengths into a plurality of electrical signals; determining, from the plurality of electrical signals, a reflectance or transmittance at a plurality of select wavelengths, for each of a plurality of spaced apart locations on the medium and material disposed thereon, the placement of said locations being along the scan; identifying, from the reflectance or transmittance at the plurality of select wavelengths at each of the plurality of spaced apart locations on the medium and material disposed thereon, the thickness and presence of the material at each of the plurality of spaced apart locations; deducing the surface dimensions of the material from presence of the material at each of the plurality of spaced apart locations; and decoding the information encoded in the thickness and surface dimension of the material.