IE20010366A1 - Hand-held anticounterfeiting apparatus vaxed on emission time decay characteristics - Google Patents

Abstract

A new hand-held emission time decay spectrometer based device is provided for identifying and discriminating the presence of labels which provide a characteristic, time dependant intensity response during or following illumination and further include algorithms for the analysis of data from a collected response spectrum and comparing it against previously stored data to determine whether there is a match. <Figure 5>

Description

OPEN TO RVMC 8NSPECBON j UNDER SECTION 23 AND RULE 23 i JNLNn.J^^ QF Uf ! Field This invention relates generally to the field of anti-counterfeiting measures and more particularly relates to hand held, time resolved, photodetector based devices, algorithms for data interpretation and methods of use.

Background Throughout history, as soon as any item has been created comprising value, there have been at least one or more attempts to create a simulacrum intended to fool a prospective purchaser or user of the item of value into purchasing it at full value despite its possessing far less value. This activity, commonly referred to as counterfeiting, has cost manufacturers and ultimately consumers vast sums of money. In addition, it has created entire industries whose purpose has been to detect, frustrate or otherwise countermand such illicit activities.

It is an aspect of the present invention to provide new devices capable of more efficiently permitting the discrimination of counterfeit goods from legitimate goods.

A perfect example of the active employment of anti-counterfeiting measures involves modern currency. While wood nickels are easily detected by most people, modern photocopying techniques have unwittingly created greater opportunities for the less skilled to duplicate currency with greater accuracy. In partial response to this threat, governments have attempted to make the sources of critical raw materials difficult to obtain including, for example, the inks and dyes used in printing and the paper used in formulating the currency. In addition, governments have also employed newer techniques of imbedding within the paper “officiating” aspects including ribbons, colored threads, and the like to make the task of counterfeiting as onerous as possible. Still more advanced techniques incorporate multidimensional holographic images and the like. While all of these measures work to some degree, it is another aspect of the present invention to provide additional levels of protection which are not so readily detected by those without specific equipment and even if detected, difficult to reproduce.

In order to be effective, the detection and discrimination of potentially counterfeit items from legitimate ones must be optimally determinable at the location where such objects are readily available. For example, being able to identify counterfeit clothing such as, for example, jeans from those of a well-known and highly respected trademark source will almost necessitate being able to “test” the jeans in question at their source of availability, the store. To do this effectively, one does not wish to alert the storekeeper who could conceivably be part of the counterfeiting operation and this, of course, prohibits visiting the store with bulky equipment. Purchase of the item and its transportation to some other testing site can overcome this impediment. While this may be acceptable with relatively inexpensive and readily transportable jeans, it becomes more problematic with auto parts, pharmaceuticals or valuable comestibles. It also fails to answer the question of whether the entire inventory is counterfeit or just the selected sample.

It is yet another aspect of the present invention to provide apparatus and methods of detection which do not require the purchase of the items in question and IE0 1 0 3 6 6 more particularly, to provide apparatus and associated detection methods which can be utilized easily in the natural environment of the item.

One manner of tracking objects is to attach thereto a tag or other label which may be detected subsequently by appropriate equipment. Such tags often include fluorescent labels or other dye-like substances which, upon proper illumination, provide a specific time-dependent decay characteristic of light emission. Some of these techniques are used, for example, with currency where a previously imprinted dye is detected with an ultraviolet light, a simple procedure. However, such detection methods are relatively simple to counterfeit in that they qualitatively determine the presence or absence of a label which is itself easily detected. Thus, the counterfeiter can easily determine that currency under UV illumination has one or more areas labelled with a fluorescent dye which he can then paint onto his counterfeit currency to thereby duplicate the effect of the original bill.

It is still another aspect of the present invention to provide apparatus and methods which utilize such labels in a fashion which is not easily duplicated illicitly.

While more complex dyes are available which require specific wavelengths of illumination and which emit or fluoresce with unique emission time decay characteristics, such substances typically require the use of a emission time decay spectrometer to identify their presence. Emission time decay spectrometers have traditionally been large bench top instruments and are not portable in nature.

It is still another aspect of the present invention to provide apparatus and data handling methods which can be used in the testing field with convenient expediency.

There have been some approaches to providing a hand-held emission time decay spectrometer device which have relied upon detecting the presence of particular decay characteristics of emitted light. However, these approaches have been notoriously unreliable in resolution of, and discrimination between emission spectra.

Summary of the Invention The various aspe&ts and principles are addressed with the present invention which provides a hand-held emission time decay spectrometer device capable of providing the necessary illumination to excite one or more light sensitive labels, which upon excitation, emit light with specific decay characteristics. The hand-held device of the present invention includes a power source, an illumination source, a light emission detector, and a central processing unit capable of interacting with data handling instructions including comparing detected signals against preset conditions to provide a quantitative or qualitative readout with respect to the presence or absence of one or more specific label substances. In addition to basic control features, the apparatus of the present invention may optionally include additional readout ports suitable for communicating real or stored values to other data accumulating or handling devices such as computers, modems, printers and the like.

In addition, the present invention provides novel algorithms for handling the data provided by the optical detector whereby false readouts occurring from spurious background illumination, varying distances to the object being tested, ageing or faulty optical detectors and the like are substantially reduced if not eliminated. j£ β 1 Ο 3 6 ® Brief Description of the Drawings These and other aspects of the present invention will be better understood by reference to the figures wherein: Figure 1 provides a block diagram showing the general electronic construction of major compounds of a hand-held emission time decay spectrometer apparatus of the present invention; Figure 2 shows a typical time decay characteristic of a photoemissive dye. Figure 3 shows a typical time response of detected light emission for two different LED 23 drive frequencies.

Figure 4 shows sample and reference tempotime decay spectra divided into a grid of rectangles for ZPX analysis; Figure 5 shows the Algorithm of the entire check routine; Figure 6 shows the Algorithm of the ZPX analysis; and Figure 7 shows the Algorithm of the ZPX program code.

Detailed Description and Best Mode The inventors hereof have surprisingly discovered that it is possible through the present invention to produce a commercially useful, hand-held photometric-based detection device in accordance with the principles, aspects and discoveries of the present invention.

With specific reference to Figure 1, there is shown an electronic block diagram of the instant invention. At the heart of the device is the central processing unit 10 which controls operation of the device in response to switch inputs 16, instructions from external memory 12 as well as data delivered from the analogue to digital (“A-toD”) converter 19 via the amplifier 24. A CPU particularly capable of implementing the algorithms described hereafter is the ATMEGA 603/103 available from Atmel(USA). The ATMEGA103 advantageously has an 8 channel, 10 bit A-to-D converter, 128K of ROM 12 which is useful for storage Of algorithms and other data handling routines. 4K of RAM can be advantageously used for calculations and additionally, there is 4K of EEPROM which can be advantageously used to store results.

Power supply 17 provides power to the ATMEGA 103 and energizes related peripheral devices including the photodetector 20, the illumination LED 23, timers 11, external memory 12, and LCD interface 13. Power supply 17 ideally may comprise any of a number of conventional sources of power and while it may rely on externally supplied “wall” power, the preferred embodiment will utilize a battery supply. Optionally, the battery may be of rechargeable type and the power supply 17 may be configured to provide for recharging ofthe battery given an external power supply or docking station.

Drivers 18 control the photodetector 20 which may be obtained from Famell (Ireland), RS Electronics (Ireland). The photodetector 20 collects the characteristic decay data as shown in Figure 4. The photodetector 20 presents the characteristic decay data as an analogue signal and through A-to-D converter 19 sends the data to CPU 10.

Returning to Figure 1, a sample (not shown) is excited by illumination from a light source such as a light emitting diode (LED) 23 which ideally may be controlled by switch 22 for power saving purposes. LED 23 preferably emits predominantly at wavelengths which are shorter than the wavelengths predominantly emitted by the EO1O366 sample or samples being measured. Selection LEDs with such characteristics more readily permits measurement of the sample’s emission time decay spectrum without undue contributions to the spectrum from the source LED 23. It has been discovered that the physical orientation of LED 23 and photodetector 20 is also important and is ideally manipulated, optionally with a UV filter, so that the amount of light from the LED 23 which is reflected into the photodetector 20 is minimized while permitting the photodetector 20 to be placed as close to the sample as reasonably possible in order to collect a maximal signal.

Switch inputs 16 may be directly connected to CPU 10 which reads their status as a binary eight bit number. This permits distinguishing whether one or more buttons are being pressed. Optionally, switch inputs 16 can be expanded to include an alpha numeric key pad interface which would permit greater operator interaction with CPU 10. Switch inputs 16 can be advantageously used to control a menu of operations to be conducted by CPU 10. A library of operations may be stored on the read only memory (ROM) which can be selected and executed,. For example, the pressing of one button sends a “high” signal to CPU 10 which then scrolls through the functions from the library of stored functions. These functions may be displayed via the LCD interface 13 and the button released when the appropriate function has been displayed. The second button can then initiate the process displayed by that particular function such as initiation of the data analysis algorithm.

Output may be conveniently represented via a liquid crystal display (LCD) through interface 13 which will ideally display, in addition to menu information concerning operation of the device, results of measurement analysis. In order to maintain a convenient size and hand-held dimensions for the present invention, a two line 24 or 16 character LCD may be conveniently used although it is possible for more complex screens to be employed albeit at the expense of size and power consumption.

Additionally, it may be convenient to provide an additional data output method such as, for example, the use of the UART onboard the ATMEL CPU to send/receive information to an RS232 14 port on any suitable device. The RS232 14 port offers substantial levels of flexibility and permits a user the option of exporting data to another computing device for further analysis or storage, or to a printer for providing a hard copy. The RS232 14 port also permits the user to import data to the present invention in order to update the reference data, and/or the library of stored functions.

Figure 2 represents a typical characteristic emission time decay spectrum that is collected by the photodetector 20 from a sample irradiated by LED 23. The decay, comprises predominately, a reflection component from the light source which has been unchanged by the sample. Essentially this return of scattered light contains little or no information and accordingly, is preferably eliminated in order to improve the signalto-noise (S/N) ratio. This discarded region is labeled D in the figure. The region D comprises an emission of light from the sample with a decay time which is different than that of the light illuminating the sample. Accordingly, data collected over the temporal range C is analyzed further.

Since each datapoint already provides information regarding the time, recall that each pixel typically represents a 250 microsecond change in time from the adjacent pixel, only intensity components are collected. This provides an array [yi, y2, y3 ... yn] where n is the number of pixels in the temporal array. While this array may be conveniently subtracted from a stored reference array earlier obtained from a known sample, the result of this processing was not found to be adequately reliable for purposes of commercial practicality. This unreliability arose because as the sample was moved increasing distances from the photodetector 20 (Figure 1), the signal strength would drop precipitously and the substrate or object could be erroneously * rejected as counterfeit.

In order to still further improve analysis, a method involving the measurement of photodetector signal DC offset as a function of LED 23 drive frequency is employed. Figure 3 depicts the detected light emission as a function of 2 different LED 23 drive frequencies. It should be noted that for the higher drive frequency (Figure 3b), the DC offset level of the detected light emission is greater. Alternatively, measurement using this method, generating an array of intensity pixels provides the same sample decay signature information but advantageously eliminates variations arising from differing emission intensities. This array is then advantageously compared to a reference array which may be stored as a temporal array and then processed similarly. While this approach is preferred because it allows for easier upgrades to the data processing algorithm without necessitating replacement of the stored reference values, one could alternatively store as a reference signal data which has been similarly processed by the data processing algorithm. Subtraction results in an array of values which are differences as a function of frequency (and hence time).

Each value in the array [delta], deltas, -.. delta,,-]] is squared to produce a new variance array [deltai2, deltas2,... delatan-i2]. The mean of this array is calculated and this single number called a “match value”. The match value then defines a pass/fail situation which may be compared with a stored match value and may be displayed in a variety of formats including the presentation of the actual numbers, a pass/fail effect or other indicia of acceptability.

The Zero Point Crossing (ZPX) Method for Spectral Comparisons and Other Applications During the course of our development of the present invention for fluorescent security features, we have sought to identify and use a reliable, computationally compact and versatile method for comparing two temporal arrays. For our application, one array (termed a sample) is compared to a representative, averaged array (termed a reference) by the present invention .

.A method previously described by the inventors1 for comparing steady state emission spectra was found to be advantageously efficient for comparing the sample and reference temporal arrays described herein. This method is called (by the inventors) the “Zero Point Crossing” (ZPX) method. Briefly, the ZPX method involves the following steps: 1. Divide the temporal arrays of both a sample and reference into a grid of rectangles remembering to normalise them both to the same scale (see Figure 5). 2. Look at each rectangle in the grid in turn and see if the reference temporal array passes through it. 3. Do the same for the sample temporal array. 1 2000, “Algorithm for use in a Hand-Held spectrophotometric apparatus”, U.S. provisional patent application number 60/212,863.

IE Ο 11B 6 6 4. Every time the reference spectrum passes through a particular rectangle, increment the “reference counter”.

. Whenever the sample and the reference spectra pass through the same rectangle, increment the “agreement counter”. 6. When all of the rectangles have been analysed, divide the agreement counter by the reference counter to obtain a number between 0 and 1. > 7. This number represents a similarity or “match” value by which the two spectra may be compared.

A value close to or equal to 0 represents two entirely dissimilar spectra whilst a value close to or equal to 1 represents two very similar spectra.

Principle Benefits of the ZPX Method 1. Flexibility - the size of the rectangles in the grid may be altered to statistically optimise comparison of sample and reference spectra. 2. Sensitivity - the ZPX method is insensitive to temporal arrays representing fast or slow decay. 3. Computationally efficient - the ZPX method uses a minimal number of floating point operations and is therefore computationally fast, even on slower microprocessors, 4. Cross-comparison - because the ZPX method generates a similarity measure between 0 and 1, no further normalization is required to statistically cross-compare spectra from different materials or readings.

Use of the ZPX Method in the Temporal Array Check Routine Figures 5 and 6 illustrate the entire check routine as used in the present invention. This routine includes several preparation steps prior to ZPX analysis.

The first is a shortening ofthe sample and reference temporal arrays in order to remove irrelevant information. This removes for example, features arising from light source reflections.

The second step involves normalising the sample and reference arrays to integer values say between 0 and 100. The normalised minimum value in both arrays is set to 0 and the maximum to 100. This step eliminates small differences due to signal size etc.

Finally, the ZPX method calculates the similarity between the former and the reference temporal array, generating the match value as its output.

The match value is compared to a cut-off which is statistically predetermined and a “pass” or “fail” is returned depending on the outcome of this comparison.

The ZPX Computational Algorithm The ZPX algorithm as used computationally is depicted in Figure 7. Essentially, the computational algorithm works as follows: 1. The input comprises the sample and reference arrays, shortened to the appropriate (but equal) size. These two arrays are linearly normalised such that the minimum value is 0 and the maximum is say 100. It should also be noted that the array consists of integers, minimizing the memory storage required and also allowing fast computation. (Ε Ο ι ϋ ο β 6 2. A “start step”, “stop step” and “step size” are defined. These parameters control the intensity (y axis) resolution used by the ZPX analysis. For example, if start step is set to 5, stop step to 95 and step size to 10, the analysis will begin 5% up from the bottom of the temporal array and finish at 95%, incrementing upwards in steps of 10%. This essentially defines one dimension of the grid of rectangles used. The other dimension (on the x axis) is controlled in a similar fashion. If for example, we set a start array element of 7 in steps of 4 and set a stop array element of 60, the analysis will begin at the 7th time decay spectrum array element, moving along in steps of 4 up to the 60th array element. The diagram below depicts the first rectangle in the grid for the figures used in the above example: Intensity NOTE: the dimensions of the rectangle on the intensity axis are defined such that the step passes through the center, the height being defined by the step size. 3. The computation begins by setting the intensity (y-axis) start step. In practice, the start step value is subtracted from the entire sample and reference arrays. This has the effect of making the lower values in both arrays negative, leaving the values corresponding to points some way up a peak feature, positive: Decay Spectrum 4. The next step involves moving along the sample and reference arrays pairwise looking for points at which the array elements go from positive to negative or vice versa. The points at which the former occur are referred to as “zero point crossings” (ZPX’s) and represent the grid rectangles through which the sample and or reference spectra pass.

. Every time the reference array produces a ZPX, the reference counter is incremented. At the same time, if a ZPX occurs for the sample array, the agreement counter is also incremented. 6. This process continues until the ends of both the intensity (y axis) step range and the array index (x axis) step range are reached with the entire array index being processes for each step in the intensity range. 7. At this point the step loops are exited, the agreement counter is divided by the reference counter to give the output match value.

ZPX is a new computational method, which has proven to be very effective for comparison of emission time decay spectra. Not only is the method flexible and reliable, but it is also computationally efficient due to the limitation of floating point calculations.

The hand-held emission time decay spectrometer based analysis of time decay spectra from fluorescent labels may be used to detect the presence of one or more of such pigment or dye labels placed upon a sample’s label or other associated surface. It will be readily appreciated that as multiple fluorofors, such as those readily available from DuPont, Riedel de Haen of Honeywell Speciality Chemicals and others, are combined, the decay spectrum resulting from illumination will have increasing degrees of complexity. This complexity will lead to vastly increased difficulty in illegitimate duplication. This means that the time decay spectrum of any material or mixture of materials represents a unique attribute (or analogue code) of the material or mixture.

Thus, known information can be converted into a mixture of luminous materials and stored covertly in a label and can subsequently be decoded by the present invention by use of known protocol or decoding algorithm. This means that rather than identifying a material mixture as merely being present, the material mixture when decoded can provide more details than simply presence. In a manner similar to bar codes, rather than just identifying the presence of black bars on white background as being the sequence looked for, the position and/or thickness may also be used to represent additional data by a known formula.

In addition, the dyes used may be either of organic or inorganic types and will be selected in accordance with the intended object to be labeled, the characteristic decay desired and the dye’s compatibility with other dyes and labels. While such dyes may be applied directly to labels or other containers associated with the item to be tracked, other applications will require application of the label directly to the item to be tested. In such instances, the labels will need to be selected in order to withstand β 1 S · normal handling during the production, transportation, inventory, and sales cycle.

Additionally, the preferred label will be selected to avoid deleterious effects upon the sample item itself.

While a variety of components, connection schemes, data analysis procedures 5 and dye types have been described along with potential uses, those skilled in the art will readily perceive; rihat a great variety of alterations to such components, their connection and use may be made without departing from either the spirit or scope of the present invention.

Claims (3)

Claims What is claimed is:

1. A hand-held device for analyzing the presence or absence of a label; comprising a light source for illuminating the label; a detector for electronically detecting the temporal variation of the intensity of light emitted by said label upon or following illumination and providing data representative of the intensity of light detected; memory storage for providing reference data; a central processing unit communicating with said detector and memoiy storage fox analyzing the dajta provided by the detector and comparing it against said reference data; $pd display means communicating With said central processing unit for displaying the results of said analysis. The device of Claim 1 further comprising a central processing unit control interface for controlling operation of said central processing unit:

2.

3. The device of Claim 2 further comprising a power source selected from the group consisting of batteries, rechargeable batteries and a receptacle for receiving externally supplied conventiOliaf power.