Radiant energy – Luminophor irradiation
Reexamination Certificate
1999-12-09
2002-04-30
Hannaher, Constantine (Department: 2878)
Radiant energy
Luminophor irradiation
C250S459100, C250S461100
Reexamination Certificate
active
06380547
ABSTRACT:
TECHNICAL FIELD
This invention relates to the use of chemical tags to convey embedded information.
BACKGROUND ART
It can be very useful to be able to determine the source of articles in commerce. For example, governmental entities would often like to be able to determine whether currency is counterfeit, and to produce currency which is difficult to counterfeit. Law enforcement organizations would like to be able to undetectably mark currency used in a ransom, for example, to be able to trace the currency back to a person who placed the marked currency in commerce. Investigators, for example, would like to be able to determine from bomb residue where the materials used entered commerce, so as to be able to determine the purchaser of the components used in the bomb.
Business entities have a need to determine whether goods which are identified with them are authentic. In order to accomplish this, such entities have a need to mark their goods in a manner which is difficult to detect, and difficult to surreptitiously replicate. A solution is especially needed for easily replicated goods, such as those in printed or digital form.
Both business and government have a need to mark materials which they have placed in commerce in a machine readable form to provide a basis for taking future action. For example, currency and many consumer products have a limited life. Machine readable date information would provide a mechanism for removing such goods from commerce at a desirable time in a cost effective manner. Business also have a need from time to time to remove defective goods from commerce. A technique for uniquely labeling goods in a machine readable form would facilitate such removal.
In various aspects, the invention is intended to address these needs.
DISCLOSURE OF INVENTION
In one embodiment of the invention, there is provided a process for marking an article in a manner which is optically invisible and difficult to detect. The process is carried out by selecting a laser luminophore which fluoresces in a predetermined portion of the spectrum when exposed to an excitation light of predetermined wavelength and applying the laser luminophore to the article in an amount which is optically invisible when the article is exposed to electromagnetic radiation but which is sufficient for machine detection when the article is exposed to the excitation light of predetermined wavelength.
In another embodiment of the invention, there is provided a process for placing a chemical “signature” on an article. The process is carried out by selecting a plurality of laser luminophores which fluoresce at different wavelengths in a predetermined portion of the spectrum when exposed to an excitation light of predetermined wavelength and applying the plurality of laser luminophores to a representative article in an amount which is optically invisible when the representative article is exposed to electromagnetic radiation but which is sufficient for machine detection when the representative article is exposed to the excitation light of predetermined wavelength.
The combination of laser luminophores is easily selected to yield a unique fluorescence spectral signature. The location of the peaks can be varied by taggant selection. It also varies depending on the wavelength of the excitation light, and, to some extent, on the carrier media The intensity of the peaks can be varied by taggant concentration. The identity of the taggants can be confirmed by evaluating the spectral signature at different times t after termination of the laser excitation, as well as by chromatograph/mass spec technique. Because the spectral signature obtained will change as the fluorescence decays, the primary spectral analysis should therefore be performed at a predetermined time t after laser excitation is terminated. Unless a counterfeiter has knowledge of the exact laser luminophores utilized, the wavelength of the excitation light employed in the analysis, and the time t at which is primary analysis is performed, replication of the signature would be extremely difficult. If the counterfeiter had knowledge of the time t at which the analysis was to be performed, an attempt could be made to match the signature with other chemicals by varying concentrations. This is easily countered, however, by performing a secondary spectral analysis at a different time t′ and comparing to a standard to confirm whether the same laser luminophores were utilized, or alternatively, performing a GC/mass spec analysis. If desired, laser luminophores having rapid decay can also be employed to mask the detection of laser luminophores having slow decay.
In another embodiment of the invention there is provided a method for recording information in machine readable form. The method is carried out by selecting a desired region of the electromagnetic spectrum and dividing it into a plurality of subregions. An information class is assigned to each of the plurality of subregions. Each information class comprises a plurality of information items. A sufficient number of discrete laser luminophores which luminescence in each of the subregions are selected to encrypt the plurality of information items contained within each information class. An encryption code is assigned to each of the information items. The code is selected from nil, one selected laser luminophore, and more than one laser luminophore. An information item is selected from each of at least a portion of the information classes. A multiplicity of laser luminophores which correspond to the selected information items according to the assigned encryption code are then selected and placed in a location from they can be subsequently accessed for exposure to luminescence inducing radiation.
The encryption easily carried out by associating a predetermined information meaning with peak locations in the luminescence spectrum. For convenience, the spectrum can be separated into regions and predetermined information meanings assigned to peaks appearing in the regions. For example, a great many laser luminophores display fluorescence in the region of 300-1000 nm. This spectral region can be divided into portions and each portion used to carry a different information item. Ten laser luminophores which display distinguishable fluorescence peaks in the range of 300-450 nm can be used to designate different years. Twelve laser luminophores which display distinguishable fluorescence peaks in the range 800-1000 nm can be used to designate different months. Thirty laser luminophores which display distinguishable fluorescence peaks in the range 450-550 nm can be used to designate different companies. Thirty laser luminophores which display distinguishable fluorescence peaks in the range of 550-650 nm can be used to designate thirty manufacturing or distribution plants. Thirty one laser luminophores which display distinguishable fluorescence peaks in the range of 650-800 nm can be used to designate days in months. Peaks may be distinguishable by lambda(max), by intensity, by shape, and/or by decay characteristics.
Combinations of laser luminophores which display fluorescence in the desired region may also be used, and this greatly reduces the number of luminophores which display fluorescence in the desired region and the resolution capabilities needed to carry out this aspect of the invention. For example, a luminophore A which display fluoresce at 580 nm, a luminophore B which displays fluorescence at 580 nm, a luminophore C which displays fluorescence at 600 nm, a luminophore D which displays fluorescence at 620 nm and a luminophore E which displays fluorescence at 640 nm can be used in varying combinations and subcombinations to yield 30 spectral signatures (A, B, C, D, E, AB, AC, AD, AE, BC, BD, BE, CD, CE, DE, ABC, ABD, ABE, ACD, ACE, ADE, BCD, BDE, CDE, ABCD, ABCE, ABDE, ACDE, BCDE, ABCDE) in the region of 550-650 nm.
Bar codes typically contain 10 digits, typically integers of from 0 to 9. Four luminophores are required to encrypt 10 information units. For example, luminophores A, B, C and D, each displayi
Archuleta Jacobo
Goeller Roy
Gonzalez Manuel E.
Spall Dale
Casperson John R
Hannaher Constantine
Israel Andrew
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