Radiant energy – Invisible radiation responsive nonelectric signalling – Luminescent device
Patent
1988-10-12
1990-07-03
Howell, Janice A.
Radiant energy
Invisible radiation responsive nonelectric signalling
Luminescent device
250337, G01N 2300
Patent
active
049393723
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a process for marking any objects by means of memory micro-crystals for recognizing and subsequently authenticating said object in any circumstances by indentification of a specific signature contained in the micro-crystals and introduced during marking operations.
SUMMARY OF THE INVENTION
The aim of the invention is to provide a reliable means for marking an object capable of keeping a signature or information specific to the object for a very long time despite natural risks and attempts of all kinds to suppress or alter the signature, for subsequently authenticating the object bearing the marker by reading said signature and comparing it with a reference signature which is the image of the signature introduced into the marker incorporated in the authentic object and kept in a safe place.
For this, the invention provides a process for marking objects by memory micro-crystals, characterized in that it consists in choosing, from crystals having a guarantee of stability of the crystal under the conditions of introduction and reading of a signature or information specific to the object, one or more micro-crystals in the form of a powder of very small sized crystals, in doping each micro-crystal, if it is not done naturally, by any one of the rare earths and transition metals, at the rate of about 100 to 1000 ppm by weight with respect to the micro-crystal, in emptying the trap centres present in the micro-crystal or micro-crystals by heating, in irradiating the micro-crystal or micro-crystals with high energy rays or particles, according to a predetermined dosage so as to trap the charge carriers released by ionization of the atoms, in a number proportional to the dose, while in their energetically metastable state, the choice of the micro-crystal or micro-crystals and the doping and irradiation conditions determining said signature or information specific to the object, in applying in at least one given position of the object a given amount of the micro-crystal or micro-crystals thus irradiated and in keeping in a safe place, for subsequent comparisons, the characteristics, the implantation and doping and irradiation conditions of the micro-crystal or micro-crystals.
Thus, if authentication of such a marked object is one day required, it will be sufficient to collect a part of the micro-crystal or micro-crystals applied to the object, read the contents of the signature carried by the marker formed by said micro-crystal or micro-crystals and to compare this data with that kept at the time of marking the authentic object. Such work of authentication will of course be carried out by a competent and approved laboratory which will therefore have access to said data kept in a safe place and will know how to go about recovering the micro-crystals.
Reading consists in locating said charge carriers trapped in the specific defects of the micro-crystal or micro-crystals by using in a way known per se the physical phenomena induced by radiation, for example the modification of optical absorption, of photoconductivity, of the paramagnetic electronic resonance, of the photoluminescence or the thermoluminescence.
The marker of the present invention, which is the material carrier of the signature or information specific to to object to be marked, is a crystal or a glass splinter of very small dimensions, generally less than 50 micrometers. It may be synthetic or natural. In all cases it contains, by voluntary doping (synthetic carrier) or spontaneous doping (natural carrier) the structural defects which make it able to receive and store said signature. As carriers there may be mentioned, among others, fluorines of type CaF.sub.2, Lif, sulphates of type Ca, Ba, SrSO.sub.4, aluminas or aluminates of the type Al.sub.2 O.sub.3, certain silicates, borates, carbonates, the quartzes, the feldspaths.
The above carriers are quite particularly suitable but, generally, all clear coloured or transparent crystals are likely to present the required characteristics, namely a good
REFERENCES:
patent: 3657085 (1972-04-01), Hoffmeister et al.
"Effect of a Low-Frequency Magnetic Field on NMR and Dynamic Nuclear Polarization of Nuclei in Al.sub.2 O.sub.3 :Cr.sup.3+ and CaF.sub.2 :Tm"; S. A. Kazanskii et al., Sov. Phys. JETP 57 (6), Jun. 1983, pp. 1345-1350.
Sazed et al, "Y and N Dosimetry Based on Elec. Conduct. of TL Photphors", Nucl. Instrum. & Meth., No. 2 (Feb. 1987).
Sutton et al, "TL Dating Using Zircon Grains from Archaeol. Ceramic", Archaemetry 18, 2(1976), pp. 125-134.
Ney Claude
Schvoerer Max
Hanig Richard
Howell Janice A.
Koch Robert J.
Microtrace International
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