HK1056032B - Method, device and security system, all for authenticating a marking - Google Patents

Description

Method, device and security system for authenticating a marking

Technical Field

The present invention is in the field of security markings and documents or products carrying such security markings, which are made using ink or paint components or batch materials. The present invention relates to a novel method of using the properties of certain luminescent pigments contained within the ink, coating composition or product. In particular, the present invention relates to a method and apparatus for using the afterglow luminescent properties of certain luminescent materials and luminescent compounds and proposes a security system for marking and authenticating objects.

Background

The luminescent material is one of the conventional components of security inks or coatings. They convert the energy of excitation radiation of a given wavelength into emission light of another wavelength. The light emission used may be in the UV range (below 400nm), in the visible range (400-700nm) or near the middle of the infrared range (700-2500nm) of the electromagnetic spectrum. A certain luminescent material may emit light of more than one wavelength simultaneously. Most luminescent materials can be excited at more than one wavelength.

If the wavelength of the emitted radiation is longer than the wavelength of the excitation radiation, it is referred to as "stokes" or "down-converted" luminescence. If the wavelength of the emitted radiation is shorter than the wavelength of the excitation radiation, it may be referred to as "anti-stokes" or "up-conversion" luminescence.

There are two types of light emission: fluorescence or phosphorescence. Fluorescence is the instant luminescence that occurs after excitation, while phosphorescence is the delayed luminescence that is observed after excitation ceases. Phosphorescence, also known as afterglow, is characterized by a decay in luminous intensity over time; the corresponding afterglow lifetime varies from nanoseconds to several hours, depending on the material.

The luminescent material may be organic or inorganic. Examples of organic materials are: cyanine molecules, coumarin, rhodamine, and the like. Examples of inorganic materials are: copper or silver doped zinc sulfide, rare earth doped yttrium aluminum garnet or yttrium vanadate, etc. Another luminescent material, such as a silicon phthalocyanine, a rare earth beta diketone, etc., may also be found in the organometallic compound.

In inks or paints, the luminescent material is used either as a pigment or as a soluble material. Recent developments have made it possible to use fluorescent pigments in colloidal form. The specific application also depends on the luminescent polymer obtained by carrying out polymerization, copolymerization or fusion or conjugation of the luminescent molecule into or onto the polymer chain. All these compound types and application forms have been used for safety components and safety applications. Corresponding detection devices can be made to recognize either instant luminescence (fluorescence) or delayed luminescence (phosphorescence).

US3,473,027 relates to the general use of organic and inorganic rare earth compounds as visible and IR luminescent labels in applications such as merchandise identification and identification, personnel identification, identification and recording by vehicles, machine readable information, ZIP codes, invoices, labels, and the like. The patent further describes a "spectroscopic detector" for identifying the luminescence response of the different thin lines.

US3,412,245 adds the decay time characteristic of the luminescence to the coding factor. This allows to distinguish rare earth based luminescence with decay times on the order of milliseconds from more rapidly decaying organic luminescent materials. This distinction is achieved by using sinusoidally modulated or pulsed UV light sources, excitation with variable modulation or pulse frequency, combined with spectral separation of different emission wavelengths.

US3,582,623 and US3,663,813 show the future development of spectroscopic detection devices for light emitting devices.

US3,650,400 describes the use of a pulsating light source in combination with synchronous detection at a pulsating frequency ("synchronous" principle) to suppress the interference of ambient light. With this method, the detector is only sensitive to the normal response of the luminescence. The main drawback of the prior art method, which relies on the determination of the material modulation transfer function, is its inherent slow speed. For these reasons, they cannot generally be used on high-speed authentication machines.

US4,047,033 describes the use of an up-converting luminescent material for security purposes and a corresponding detection device. The detection process relies on excitation with GaAs IR-LEDs emitting light at 950nm wavelength in a continuous or pulsed manner and spectroscopic identification of the optical radiation. For the evaluation of the characteristic rise and decay times of the luminescence response, indirect means are referenced by measuring the phase shift of the pulse. However, this method is very susceptible to variations in luminous intensity, and thus is not easy to implement in practice.

Another prior art method suitable for high speed qualification relies on pulsed excitation of a moving test sample on a conveyor belt. After passing through the UV excitation source, the intensity of the excited light decays according to the intrinsic decay characteristics of the material. One or several light detectors arranged along the conveyor belt at a determined distance from the UV source are used to estimate the specific point of the attenuation characteristic. The main drawback of this approach is that it is limited to phosphorescent materials whose characteristic luminescence decay time is on the order of 50 milliseconds. This limitation is a consequence of mechanical constraints (conveyor belt speed) in the detection process.

The object of the present invention is to provide a method, a device and a security system which overcome the drawbacks of the prior art. In particular, the present invention allows for rapid sampling of luminescence decay characteristics, and is therefore suitable for high speed machine-readable applications. Furthermore, the present invention allows the up-converting phosphor material and the down-converting phosphor material to be selected in the range of decay times from a few tenths of milliseconds to 10 milliseconds or more. Another particular object of the invention is to make the authentication process more reliable by compensating for variations in the luminous intensity that may be caused by variations in the luminous marking itself (ageing, contamination) or in the measuring device.

Disclosure of Invention

The foregoing objects are primarily achieved by a method, apparatus and security system for authenticating luminescent sample tags. The invention is based on the result of comparing the time-dependent light emission function of the detection material with the time-dependent luminescence emission function of the reference material. Thus, according to the invention, instead of using a measured intensity value as an identification property, a curve shape is used as an identification property. The transmit functions are compared in a normalized manner. In doing so, the comparison process is largely independent of intensity variations due to aging, changes, or contamination.

The invention also relies on a direct estimation of the light emission function of the sample marker as a function of time after pulsed excitation. Luminescence can be excited using any of a variety of intense pulsed radiation sources (e.g., light emitting diodes, laser diodes, Q-switched lasers, and light sources obtained using non-linear optics) and X-ray pulsed or ion beams, particularly pulsed electron beams. After excitation with a suitable excitation pulse, preferably a light pulse of a suitable wavelength and pulse width, the luminescent material emits part of the absorbed energy in the form of emission radiation of a second wavelength. In some cases, the emission radiation occurs almost immediately and when excitation ceases, the emission radiation also ceases. In other cases, the emission is time-delayed and the intensity of the emitted radiation either satisfies a simple exponential decay law, or a complex hyperboloid law, or even shows rise and decay characteristics that represent a complex internal energy transfer process and competing decay mechanisms. In all cases, however, the emission intensity as a function of time after cessation of external excitation depends only on the luminescent material itself, and it is therefore used as an identifying property to indicate the presence of the particular material. Even if the absolute luminescence intensity is reduced, for example because of material ageing or contamination, the shape of the emission time function remains unchanged, since it is characteristic of the fluorescent component.

In the present invention, the decay or decay curve represents any particular intensity function of time for the sample and its reference. This intensity time function represents the measured response of the intensity of light emission due to the excitation pulse. The term "excitation source" also applies to electromagnetic sources having a wavelength between 200nm and 2' 500nm, including UV light, visible light, and short-wave (non-thermal) IR light. The definition may also include other methods of excitation using, for example, X-ray or electron beam pulses.

In performing the above method and using the authentication device, the emission intensity of the sample is sampled at appropriate time intervals and stored in analog memory, for example digitized using an analog-to-digital converter (AD) and stored in digital memory.

The light emission reference curve as a function of time, obtained on the reference sample using the same instrument configuration and procedure, is also stored in digital memory and provided for comparison and characterization.

The test specimen is identified by comparing its luminescence decay curve point by point with a stored reference sample decay curve.

The sample and reference transmit functions are compared in normalized form. Normalization means that the intensity values of the two emission functions are scaled in such a way that the highest values of the two attenuation curves are the same.

If the comparison of the sample attenuation curve with the corresponding reference attenuation curve is the same within a determinable tolerance range, a consistent signal is provided to validate the sample. Conversely, it is considered to be non-uniform. The uniform signal or the non-uniform signal may be any of an electrical signal, an optical signal, an acoustic signal, or other signal.

The determinable tolerance may be based on a point-by-point approach, i.e., each sample curve point is compared to its corresponding reference curve point and must be within an absolute range (e.g., +50/-30), a relative range (e.g., ± 20%), or a separately defined range from the reference curve point. On a point-by-point basis, the sample is accepted only if all points are within their respective tolerances.

Alternatively, an overall tolerance criterion may be applied, i.e. a single difference of the respective specimen intensity from the reference intensity, or some convenient function thereof, e.g. a sum of squares or absolute values, etc., is calculated for all points and the resulting sum is checked according to said overall tolerance criterion.

The method of the invention is advantageous in that it can be applied to any type of luminescence decay characteristic, whether exponential or non-exponential. The method is particularly applicable to the identification of mixtures of luminescent materials having the same specific luminescence center in environments with different attenuation characteristics. For example, a mixture of YVO4: Eu and Y202S: E can be identified in this way with its individual components.

The method according to the invention can be carried out in such a way that a "one-shot" measurement, i.e. the application of an excitation light pulse and then the acquisition of the corresponding luminescence response as a function of time for a duration of milliseconds, is sufficient to acquire the entire luminescence decay information of the sample and compare it with reference data. Therefore, high-speed operation of a rapidly moving sample can be ensured.

However, in the case of weak light emission, i.e., in the case where the signal-to-noise ratio (S/N) is not sufficiently high, it is also possible to repeat the measurement several times and calculate the average value of the above-described "impact" results point by point to improve the S/N, thereby obtaining ideal attenuation curve information with higher statistical accuracy.

Another advantage of the method of the invention is that it does not require a model, i.e. the luminescence decay curve itself, rather than using the parameters obtained therefrom as an identification feature. The process of acquiring parameters always depends on the physical model, and without the model, the process of acquiring parameters cannot be applied. Therefore, the method that does not require a model has a larger range of applications than the method that relies on a model.

The method according to the invention can be used in combination with other prior art techniques for luminescence response spectrum identification. In particular, the method may be used in conjunction with spectral filters, wavelength dispersive elements, gratings, or other optical instruments that result in wavelength selection.

To improve the signal-to-noise ratio of the optical detection chain, optical collection optics may also be used.

More than one detection channel is provided for the simultaneous detection of mixed luminescence, or for the simultaneous detection of light emitted at more than one wavelength. The simultaneous detection of light emitted at more than one wavelength is common in the case of rare earth ion based luminescent materials. Thus, the appropriate wavelength selector is provided for the different detection channels, and the corresponding intensity time data is also sampled and stored separately.

In a particular embodiment, the detection channel is a miniature spectrometer unit including a wavelength disperser (e.g., a prism, grating, or linear variable filter) and an array light detector. The array photodetector may be a linear photodiode array or a linear CCD (charge coupled device) array. To ensure high operating speeds, a modified two-dimensional CCD matrix array may be utilized instead of a linear CCD array.

In a CCD matrix array, a photo-induced carrier image frame generated by exposing a silicon chip is shifted "vertically" line by line to the edge of the chip, and then shifted "horizontally" line by line and read out pixel by pixel. This shifting process is done in parallel and a large amount of data can be processed quickly (typical speeds for 256 x 256CCD arrays are up to 40MHz for "horizontal" pixel-to-pixel shifts and up to 4MHz for "vertical" row-to-row shifts).

The modified CCD matrix array is laid out in such a way that the first row of pixels acts as a photodetector array for the wavelength disperser producing the spectrum. Subsequent rows of pixels are prevented from being disturbed by light and are used as intermediate mass storage devices. After the excitation pulse, time-varying spectral information is collected using a fast "vertical" line-to-line shifting process and stored in the obscuration region of the CCD for later readout by the instrument processor.

To obtain hardware flexibility for detecting light with different excitation wavelengths, more than one excitation source may be provided. Light Emitting Diodes (LEDs) are particularly suitable for illuminating a spectral range with a bandwidth of about 50 nm. A set of different LEDs may be provided to cover a larger spectral region of interest. The multiple LED light sources can be controlled by the instrument's microprocessor so that the selection of the excitation wavelength can be performed by programming alone.

Of particular interest is combining the multi-LED light source with the micro-split detector unit to obtain a universal luminescence/decay time detector module.

According to the invention, it is entirely possible to use the same apparatus for defining the reference attenuation curve and for identifying unknown samples. The device may operate in a "learning mode" in which a reference decay curve (reference intensity time-transmit function) is obtained from a reference sample and appropriately processed, and the corresponding data is then stored in memory. The apparatus may also be operated in a "test mode" in which the luminescence decay curve (sample intensity time-emission function) of a sample carrying the marker to be authenticated is acquired, the corresponding data appropriately processed and compared with previously stored reference data to obtain a consistent/inconsistent indication. Thus, the same device may be operated in a "learn mode" to store reference data in memory, and then in a "test mode" to test a sample. The device may also comprise more than one memory segment to provide reference data for authentication of different marks.

However, it is not necessary to implement the "learning mode" and the "testing mode" within the same physical unit or device. In an alternative embodiment, the first device is dedicated to acquiring/defining the reference attenuation curve from the reference sample. The reference data is then transferred to the memory of a similar second device dedicated to the identification of the specimen sample.

The method and apparatus according to the invention can be used to authenticate ink and/or coating compositions comprising suitable luminescent materials as well as articles such as security articles or painted articles obtained with said ink and/or coating compositions.

Furthermore, the method and apparatus may also be used to authenticate suitable luminescent batch materials, such as paper or plastic used to make items such as banknotes, security documents, identification cards, credit cards, security threads, labels and other security articles.

According to the above method, a security system may be realized by providing a set of reference samples comprising luminescent materials and/or luminescent mixtures having similar spectral emission (i.e. emission color), but having different time-varying emission functions. With the method and apparatus according to the invention, one or more reference samples can be identified, for example, by being identified by introducing them into a marker on the object.

Brief Description of Drawings

The invention will be further elucidated with the aid of an embodiment of a security system and an authentication device shown in the drawings described below.

Figure 1 shows the emission spectrum of an up-converting phosphorescent material used in the present invention,

figure 2 shows the luminescence decay curves of 4 different up-converting luminescent phosphorescent materials used for constructing the security system according to the invention,

figure 3 shows a block diagram of a first embodiment of an authentication device according to the invention,

figure 4 shows a typical luminescence intensity/time characteristic for authentication purposes according to the invention,

figure 5 shows a schematic block diagram of an alternative embodiment of the detection device according to the invention,

figure 6 shows a schematic diagram of a more complex embodiment of the detection device according to the invention,

figure 7 shows the energy levels of praseodymium (3+) ions,

figure 8 shows a focusing grating type micro spectrometer mounted on a linear photodiode array,

figure 9a shows the readout principle of a two-dimensional CCD array,

fig. 9b illustrates the data shift principle within a CCD array.

Detailed Description

The security system according to the invention comprises a microprocessor-based authentication device as shown in the schematic diagram shown in fig. 3.

As representative of the class of luminescent compounds within the label, 4 different properties of erbium-based up-converting phosphorescent materials were chosen: gd202S, Er, Yb; Y202S is Er, Yb; BaY2F8 Er, Yb; NaYF4 Er, Yb. After irradiation with 950 or 980nm light sources, they both emitted green light close to 550nm (as shown in fig. 1). However, the lifetime of green color phosphorescence emission is largely different for these 4 materials, as shown in fig. 2.

As shown in FIG. 3, the evaluation device includes, for example, an AduC812 micro-transducer using an analog device^TMA microcontroller or processor 1 is implemented. The AduC812 chip includes: 16MHz 8052 microprocessor (CPU)1a, having 32 digital I/O lines; a 5 μ s 12-bit analog/digital (a/D) converter 1 b; a digital/analog converter; integrated RAM (256 bytes); and an EE/flash memory (Mem) or storage device 1c for storing programs (8k) and storing data (640 bytes). The EE/flash memory (Mem)1c is an electrically erasable permanent memory and can implement a "learning mode". In this example, the memory of the AduC812 chip is mated with 32K of external Random Access Memory (RAM) or storage device 1 d.

The authentication device further comprises: a laser current driver 2 controlled by the AduC 812; a 980nm wavelength pulsed Laser Diode (LD) as an excitation source 3, having collimating optics 3 a; and a photo detection chain based on a commercially available GaAsP Photodiode (PD)4 sensitive to green light, an optional filter 4a, and a corresponding amplifier 5. The optical detection chains 4, 5 are laid out in such a way as to guarantee a sampling rate of 5 μ s corresponding to the AduC812 with a minimum bandwidth of 200 KHz; its output is connected to the a/D converter 1b of the AduC 812. The AduC812 is also connected to the mode converter SLT for selecting the learning/testing mode L/T; also connected to button B for starting a measurement cycle; and to yellow, green and red LEDs 8a, 8b and 8c for indicating On/Off and acknowledge/fail (Yes/No) status. Button B turns on the circuit main power supply Vcc. A processor controlled power hold switch 9 is provided to enable the controller to maintain its own power supply to complete the measurement cycle and to turn itself off in good condition.

In the "learning mode" L, a reference attenuation curve or a reference intensity time-emission function is obtained. The reference sample 7-R is placed below the collimating optics 3a and the filter 4 a. After the SLT switch is set to the "learning mode", the button B is pressed to supply power to the detection unit. Under the control of the processor 1, the laser diode of the excitation source 3 is acted upon by a short current pulse (typically 1A during 200 μ s) from the laser current driver 2. The 980nm laser excitation pulse P is focused by the collimating optics 3a onto the luminescent fiducial mark M-R of the reference sample 7-R. The photodiode 4 detects the corresponding luminescence response (emission radiation E) at 550 nm. The signal from the photodiode enters the amplifier 5, and enters the a/D converter 1b from the amplifier 5. After pulsing the laser diode, the processor 1 initiates a Direct Memory Access (DMA) data acquisition process. In the process, the a/D converter 1b samples the signals of the light detection chains 4, 5 at regular time intervals (e.g., every 5 μ s) and stores them in a subsequent storage location of the external storage device 1D. Based on the previous results, the microprocessor is programmed to preset the sample time and number of samples to be taken. After sampling is completed, the data in the storage device 1d is analyzed, processed, compressed to 64 data points defining the reference values VR1 to VR64 (refer to fig. 4), and stored in the permanent storage device 1c of the micro-converter. The functions represented by the reference values VR1 to VR64 are also normalized, i.e. the reference values VR1 to VR64 are scaled according to the highest value of the function. Therefore, VR1 through VR64 are not related to the overall intensity variations affecting the fluorescence emission. Fig. 4 shows a possible form of this reference curve, which holds a series of reference values (VR1, VR2, VR 3..) at respective points in time (t1, t2, t 3.). The VRn value may optionally be associated with a tolerance (Δ +, Δ -).

The successful termination of the process is confirmed with a green "Yes" indicator 8 b. A few seconds after the successful termination of the process, the microprocessor switches off the detection unit using the power switch 9.

In "test mode" T, the sample attenuation curve is obtained and compared to a previously stored reference curve. According to fig. 3, the specimen sample 7-P including the specimen marker M-P is placed in the correct sampling position. After the SLT switch is set to "test mode" T, the trigger button B is pressed to turn on the authentication apparatus. An operation procedure very similar to the one described for the "learning mode" is performed until the measured light emission attenuation data is processed and compressed into 64 data points. The data VP1 to VP64 thus obtained are also subjected to normalization processing and compared with previously stored reference values VR1 to VR 64. To compare the data representing the attenuation curve of the sample marker M-P with the data representing the attenuation curve of the reference marker M-R, in our example the corresponding data points are subtracted and the absolute value of each difference is added for all 64 data points. If the value of this sum is less than an optional criterion, the test sample is accepted as "good" and the green "Yes" LED 8b is activated. If the value of the sum exceeds the criterion, the test sample is rejected as "bad" and the red "No" LED 8c is activated. After a few seconds after terminating this operation, the microprocessor switches off the detection unit via the power switch 9.

The emission intensity of the reference sample 7-R or the sampled specimen 7-P may vary over a large measurement range. Ageing of the luminescent material, or changes in the surface of the reference mark M-R or sample mark M-P are common causes, for example if the mark is sprayed onto an item 7 such as a banknote or product label, the surface of the banknote or label either becomes dirty or scratched. This may significantly reduce the excitation intensity of the luminescent material and may also reduce the intensity of the emitted radiation of the label. In particular, the absolute value of the emission radiation E of the reference sample 7-R is greater than the absolute value of the emission radiation E of the sample 7-P.

The method according to the invention therefore relies on a comparison in the form of an attenuation curve, rather than on a single absolute intensity value.

After normalizing the two curves according to their highest values between t1 and tn, two identical curves can be obtained for samples containing the same luminescent material even if the luminescent material has different densities. By applying the general principle of comparing normalized curves, the identification process is not affected by various factors that cause intensity or measurement bias.

The number of individual data points VP1 to VPn and VR1 to VPn taken to define the sample curve CP and the reference curve CR may vary widely. Generally the larger the number the more accurately the curve can be defined.

For practical purposes, between 32 and 128, preferably 64, is sufficient.

After obtaining the reference values VR1 to VR in the RAM 1d or the permanent storage device 1c, this data may be transmitted as reference values VR1 to VRn to other authentication devices.

Also, each authentication device has a plurality of memory segments for storing reference values VR1 to VRn of a plurality of different marks M. In general, the reference value VR for making the comparison may be provided in any way, i.e. the electronic data may be provided by an internal or external memory as an encrypted memory or data attachment, a memory card, a wired or wireless transmission, or any other suitable way.

The AduC812 central processing unit 1a is programmed to perform the above-described operation after the button B is pressed. They mainly include the following program function blocks:

by setting the switch 9 on during the measurement period, the power is guaranteed to be autonomous,

the learning/test mode switch SLT is read,

if the learning mode is L, then:

an external memory is prepared for the DMA data acquisition process,

the laser diode is pulsed on with a pulse of,

a predetermined number of samples of the optical response of the DMA mode are collected into the memory device 1d,

the sampled data is post-processed and compressed into an optimized form of 64 data points,

the compressed, normalized data including the compression indicator is stored as a reference into the internal permanent data EE/flash storage device 1c of the AduC812,

if the test mode is T, then:

an external memory is prepared for the DMA data acquisition process,

the laser diode is pulsed on with a pulse of,

a predetermined number of optical response samples of the DMA mode are collected into the memory device 1d,

the sampled data is post-processed and, based on the previously stored compression indicator, compressed into 64 normalized data points,

the compressed, normalized data is compared with the normalized reference data previously stored in the storage device 1c, and a consensus/non-consensus indicator is obtained,

the acceptance/failure indicator LED is set accordingly, to display the result,

after waiting a predetermined length of time, the power is disconnected by the switch 9.

In an alternative embodiment of the authentication apparatus according to the invention shown in fig. 5, two excitation light sources 31 and 32 for emitting excitation pulses P of different wavelengths are provided, with collimating optics 31a and 32a and respective pulse drivers 21 and 22. Two detection units for two different wavelengths are also provided, including collimating optics 41b and 42b, filters 41a and 42a, photodetectors 41 and 42, and amplifiers 51 and 52. The optical elements are arranged in such a way that all optical axes intersect at one observation point on the specimen sample 7-P. The specimen sample 7-P carrying the specimen label M-P is transported through an identification device. Depending on the property to be detected, the processor 1 sends a current pulse to the light source 31 or the light source 32, or to both. Depending on the emission to be detected, a light detector 41 and/or a light detector 42 is used.

For example, the device may be designed to detect erbium-based up-converting materials that emit green light at 550nm when excited with 980nm light by the excitation source 31 and the detector 41 detects green light at 550nm, while the europium luminescent material contained in the sample labels M-P is excited with 370nm light by the light source 32 and light near 610nm emitted by the europium luminescent material is detected by the detector 42. The presence of two luminescent materials is required to confirm the identification process of the sample marker M-P. In other respects, the operating principle of the authentication apparatus according to this particular embodiment is the same as that of the first embodiment.

In another particular embodiment, the authentication device is used to detect a praseodymium-based up-converting material that is simultaneously excited with a first laser light at 1014nm and a second laser light at 850nm, which then emits red light at about 600nm (as shown in FIG. 7). In this embodiment, excitation sources 31 and 32, operating in synchronism, generate excitation pulses P. The photodetector 41 is caused to monitor the emission at 600 nm. There is also praseodymium down-converted emission and the second photodetector 42 is used to monitor the 1310nm praseodymium down-converted emission. Depending on the required complexity and the luminescent properties of the sample marker M-P, even more excitation light sources and/or light detectors may be incorporated.

In yet another more complex embodiment of an authentication device according to the invention, as shown in fig. 6, use is made of: a combination of multiple LED or LD excitation sources; the focusing grating type micro spectrometer 4 a' includes an optical waveguide; a two-dimensional CCD array 4 b' as a photodetector/collection device; and a processor 1 for controlling the data acquisition, storage and calculation processes.

The excitation source 3 preferably comprises a series of light emitting diodes 3.1, 3.2, 3.3, 3.. 3.n, which emit light with wavelengths covering the UV, visible and near infrared portions of the spectrum. In particular, it has been demonstrated that a commercially available set of LEDs emitting at 370nm (UV), 470nm (blue), 525nm (turquoise), 570nm (green), 590nm (yellow), 610nm (yellow-orange), 660nm (red), 700nm (black), 740nm (IR), 770nm (IR), 810nm (IR), 870nm (IR), 905nm (IR) and 950nm (IR) can be used. The LEDs may be located at a convenient location for the user, but are preferably arranged in a circle around the optical waveguide of the micro spectrometer.

The focusing grating type micro spectrometer 4 a' is a device according to fig. 8. The light from the sample process is coupled into the focal plane of the spectrometer using an optical fiber or waveguide that acts as a point source to illuminate the self-focusing reflective grating. The self-focusing reflective grating reflects the light to a linear photodetector array to disperse different wavelength components included in the light to adjacent pixels of the array. The spectrum emitted by the sample process can therefore be obtained by reading out each pixel of the photodetector array.

To quickly collect time-varying spectral information, a two-dimensional charge-coupled device (CCD) array 4 b' is used. Such a CCD array comprises two-dimensional light-sensitive pixel areas which can be read out using the shifting process shown in fig. 9 a: the pixels are first "vertically" shifted row by row to a horizontal register. Here, the individual pixels are "horizontally" shifted pixel by pixel to the preamplifier and further output to its output. Two-dimensional CCD arrays are commonly used for cameras and may comprise 256 to 1K pixels in each dimension. Fig. 9b shows a shifting process of shifting pixel information as stored photo-generated electrons: there are 3 electrodes (electrode 1, electrode 2, electrode 3) for each pixel, which are driven by 3 phase positive clock signals (φ 1, φ 2, φ 3). Electrons always accumulate in the positive potential well represented by the "down" state. For example, to shift the storage electrons of the entire array by one pixel after a clock cycle (t 1-t 6), the upper and lower phases of the clock signal are overlapped, i.e.:

	t1	t2	t3	t4	t5	t6
								φ1：	on the upper part	On the upper part	On the upper part	Lower part	Lower part	Lower part
φ2：	Lower part	Lower part	On the upper part	On the upper part	On the upper part	Lower part
								φ3：	On the upper part	Lower part		Lower part	Lower part	On the upper part	On the upper part

In the present invention, the first row of light sensitive Pixels (PIX) of the two-dimensional CCD array is used as the linear photodetector array of the miniature spectrometer device 4 a'. The remaining CCD pixel rows are not used as photo detectors but to avoid light interference and as a main storage device for time varying spectral information.

The processor 1 and the storage device 1c thereof control the data acquisition and processing process, and execute the following steps: pulsing one or more appropriate diodes of the excitation source 3 to excite the luminescent labels of the corresponding reference sample 7-R and specimen sample 7-P, respectively; after the light pulse is applied, line feed is carried out in the CCD array for proper times so as to store the frequency spectrum response information changing along with time into a protection area of the array as a two-dimensional image frame; reading the time-varying spectral response message from the CCD array and storing it in the storage device 1 c; the time-varying spectral information is post-processed and calculated according to the authentication task to be performed.

The line feed frequency of step b) determines the achievable time resolution. The line feed frequency is up to 4MHz, corresponding to a time step of 250 ns. The process of reading out the accumulated data at step c) may be slower in a manner well known to those skilled in the art. The data available after step c) corresponds to an "image frame" having spectral and temporal dimensions. By dividing the time segments by the appropriate wavelength, a decay time curve can be obtained from the frame; this information is processed and calculated as explained in the one-dimensional embodiment described above. The analysis may also be extended to more than one wavelength or may also be analyzed using a second dimension of the acquired data frame in conjunction with spectral analysis.

Claims (16)

1. A method for identifying luminescent sample labels (M-P), comprising the steps of:

exciting the luminescent sample label (M-P) with at least one excitation pulse (P) of at least one excitation source (3, 31, 32, 3.1 to 3.6),

measuring, in dependence on the at least one excitation pulse (P), a sample intensity value (V) of an emission intensity (I) emitted by the emission radiation (E) of the luminescent sample marking (M-P) at time intervals (t1 to tn)_P1To V_Pn)，

Generating said sample intensity value (V)_P1To V_Pn) The intensity of the sample as a function of time emission,

comparing the sample intensity time-transfer function with at least one reference intensity time-transfer function,

the sample intensity time-emission function and the reference intensity time-emission function are normalized prior to the comparison.

2. Method according to claim 1, characterized in that at least one luminescent specimen marker (M-P) is part of a specimen sample (7-P) to be identified, and in that a specific emission characteristic of the at least one luminescent specimen marker (M-P) is measured, the specific emission characteristic comprising: at least one excitation wavelength of the excitation pulse (P), at least one emission wavelength of the emission radiation (E) and at least one of the emission wavelengths are in a time interval (t)₁To t_n) Sample intensity value (V) of emission intensity (I) of (1)_P1To V_Pn)。

3. The method according to claim 1, characterized in that at least one fluorescent fiducial marker (M-R) is part of a reference sample (7-R), and in that specific emission characteristics of the at least one fluorescent fiducial marker (M-R) are measured, the specific emission characteristics comprising: at least one excitation wavelength of the excitation pulse (P), at least one emission wavelength of the emission radiation (E) and at least one of the emission wavelengths are in a time interval (t)₁To t_n) A reference intensity value (V) of the emission intensity (I)_R1To V_Rn)。

4. Method according to claim 3, characterized in that the reference intensity value (V) is set_R1To V_Rn) And/or at least one reference intensity time-transfer function is stored in at least one memory device (1c, 1 d).

5. The method according to claim 4, characterized in that the at least one reference intensity time-transfer function is stored in normalized form and/or in non-normalized form.

6. Method according to one of claims 1 to 3, characterized in that the luminescent sample marker (M-P) and the reference marker (M-R) are excited separately with at least one excitation pulse (P) emanating from at least one excitation source (3, 31, 32, 3.1 to 3.6) as a laser and/or light emitting diode.

7. Method according to one of claims 1 to 3, characterized in that the luminescent sample marker (M-P) and the reference marker (M-P) are excited separately with at least one electronic excitation pulse (P).

8. An apparatus for identifying luminescent sample labels (M-P), the apparatus comprising:

at least one detector (4, 41, 42, 4 b') for a time interval (t) depending on at least one excitation source (3, 31 to 36)₁To t_n) At least one excitation pulse (P) is generated, and a sample intensity value (V) of the emission intensity (I) of the emission radiation (E) of the luminescent sample marking (M-P) is measured_P1To V_Pn)，

At least one memory (1c, 1d) for at least one wavelength of the emission radiation (E) of the fluorescent fiducial markers (M-R) at time intervals (t)₁To t_n) Storing a reference intensity value (V) of the emission intensity (I)_R1To V_Rn) And/or for storing the slave reference intensity value (V)_R1To V_Rn) At least one reference intensity time-transfer function is formed,

at least one processor (1) for generating said sample intensity values (V)_P1To V_Pn) The intensity of the sample as a function of time emission,

at least one processor (1) for comparing the sample intensity time-transfer function with at least one reference intensity time-transfer function, and

at least one processor (1) normalizes the sample intensity time emission function prior to comparison with a normalized reference sample intensity time emission function.

9. The apparatus according to claim 8, further adapted for identifying fluorescent fiducial markers (M-R), the apparatus comprising:

at least one detector (4, 41, 42, 4 b') for a time interval (t) depending on at least one excitation source (3, 31 to 36)₁To t_n) Generating at least one excitation pulse (P) measuring a reference intensity value (V) of an emission intensity (I) of the emission radiation (E) of the fluorescent fiducial marker (M-R)_R1To V_Rn) And an

At least one processor (1) for generating said reference intensity value (V)_R1To V_Rn) The reference intensity time-transmit function of.

10. The apparatus according to claim 8 or 9, characterized in that it comprises said at least one excitation source (3, 31, 32, 3.1 to 3.6).

11. The apparatus according to claim 8 or 9, characterized in that the at least one detector (4) comprises a wavelength selector (4 a').

12. Apparatus according to claim 8, characterized in that it comprises at least one spectrometer for distinguishing between two or more emission wavelengths, and in that said at least one detector (4, 41, 42, 4 b') is an array photodetector for measuring the emission radiation (E) at two or more emission wavelengths, allowing to simultaneously measure the sample intensity values (V) of the emission radiation (E) of the luminescent sample marks (M-P), respectively_P1To V_Pn) And simultaneously measuring a reference intensity value (V) of the emitted radiation (E) of the luminescent reference mark (M-R)_R1To V_Rn)。

13. The device according to claim 12, wherein the at least one array of photodetectors is a two-dimensional array of charge-coupled devices (4 b'), the first row of photosensitive Pixels (PIX) being used as a light detection array, the remaining rows of pixels being used as a main storage device for spectral information as a function of time during the line feed process.

14. A security system for authenticating luminescent sample markers (M-P), comprising:

the apparatus according to claim 8, wherein,

at least one reference sample (7-R) comprising at least one fluorescent reference marker (M-R) for at least one wavelength of emission radiation (E) of said fluorescent reference marker (M-R) at time intervals (t [)₁To t_n) Measuring a reference intensity value (V) of the emission intensity (I)_R1To V_Rn) And an

At least one specimen sample (7-P) comprising at least one luminescent specimen marker (M-P) for at least one wavelength of the emission radiation (E) of said luminescent specimen marker (M-P) at time intervals (t [)₁To t_n) Measuring the intensity value (V) of the sample of the emission intensity (I)_P1To V_Pn)。

15. A safety system according to claim 14, wherein at least one of said coupon samples (7-P) is part of an ink and/or paint component of an article (7) to be authenticated.

16. A safety system according to claim 14, wherein at least one of said coupon samples (7-P) is contained within a bulk material of the article (7) to be authenticated.