DE69910550T2 - METHOD AND DEVICE FOR MONITORING ARTICLES - Google Patents

Abstract

A method and apparatus for monitoring articles to determine the presence of an authenticity indicating characteristic. The method comprises irradiating an article with radiation in at least first and second wavebands; detecting first radiation generated by the article in response to irradiation at the first waveband, the first waveband being chosen such that the first radiation generated varies in accordance with the presence or absence of the authenticity indicating characteristic and in response to the presence of obscuring material on the article. Second radiation generated by the article in response to irradiation at the second waveband is detected, the second waveband being chosen such that the second radiation generated by the article varies with the degree of obscuring material on the article but is substantially independent of the presence of the authenticity indicating characteristic. The detected radiations are compared to determine whether or not the authenticity indicating characteristic is present.

Description

The invention relates to a Method and device for monitoring articles, e.g. B. documents of value, such as banknotes.

The principle of using reflection measurements, about authenticity or authenticity of security documents is in itself known. The properties of security paper are chosen so that its reflectivity in some areas of the spectrum (in the UV, visible and IR range) from that of many Unsecured paper deviates from that used to manufacture counterfeited paper Documents are used.

A simple authentication system can for example be designed so that it illuminates a document with UV light and the intensity who measures reflections. If this intensity exceeds a predetermined threshold, the document is considered authentic. (However, it should be noted that it in special cases the fake document is the higher Has reflectivity.) It is also possible, through natural UV light to measure excited fluorescence of the paper at the same time, since the most security papers have low natural fluorescence. The method of measuring "UV brightness" is also known.

• – Die Intensität der Reflektionen eines vorbestimmten Dokuments hängt auch von den Eigenschaften des Meßsystems ab, von denen einige sich erheblich ändern können. Beispielsweise ändert sich die Ausgangsintensität der meisten UV-Quellen mit der Temperatur und mit der Alterung der Quelle. Die Eigenschaften der benutzten optischen Bauteile (Filter, Blenden, Linsen usw.) können sich ebenfalls mit dem Alter ändern. Sich während der Benutzung auf den optischen Oberflächen ansammelnder Schmutz und Staub verringern die gemessene Intensität.
• – Die Intensität der Reflektionen hängt von der Verschmutzung des Dokuments ab: Je schmutziger das Dokument ist, um so geringer ist das Reflektionsvermögen.

The simple methods outlined above have some disadvantages in terms of practical implementation. The two most important are:

• - The intensity of the reflections of a predetermined document also depends on the properties of the measuring system, some of which can change considerably. For example, the output intensity of most UV sources changes with temperature and with the aging of the source. The properties of the optical components used (filters, screens, lenses, etc.) can also change with age. Dirt and dust accumulating on the optical surfaces during use reduce the measured intensity.
• - The intensity of the reflections depends on how dirty the document is: the dirtier the document, the lower the reflectivity.

amendments the sensitivity of the measuring system can be reduced by means of an automatic calibration system which on a reference surface the measured signal level is constantly monitored, however, it is difficult and expensive to maintain a constantly clean reference surface. On such a system can of course do not compensate for contamination of the documents.

The overall effect is a reduction of discernment of the detection system. If the detection threshold is set so high, that this cleanest falsification by means of a new, clean (highly sensitive) Systems is detected or determined, a relatively large proportion dirty, real notes wrongly than fake viewed, this proportion with increasing age or increasing Contamination of the detection system increases. If the threshold is reduced so that only a small proportion of valid ones Notes incorrectly due to an old, dirty system (with low sensitivity) than fake is considered, an unacceptably high proportion of counterfeits through a clean system as valid accepted.

In U.S. Patent 4,723,072 a device for measuring soiled banknotes is described, where one or more sensors are in the same optical wavelength range work. The present invention is not concerned with measurement pollution.

In U.S. Patent 3,679,314 is a device for visually checking the authenticity of banknotes by successively illuminating a selected part of a banknote described with light rays that have different spectral distributions, after which the light transmitted or influenced by the illuminated part is detected. The problem with this solution is that there are two filters be scanned mechanically in the region of the illumination beam have to, to regulate the lighting of the banknote.

One aspect of the present invention is a monitoring process of articles to the presence of a character indicating authenticity determine where an article with one in at least one first and a second wavelength range lying radiation is irradiated; a first radiation that through the article in response to irradiation in the first wavelength range is generated, is detected; the first wavelength range is chosen so that itself the first radiation generated depending on the presence or lack of authenticity indicating character and in response to the presence of a Cover material on the item changes; by the article in response to radiation in the second Wavelength range generated second radiation is detected and the detected first and second radiation are compared to determine if that the authenticity indicating characters are present or not, characterized by that the second wavelength range like this chosen will that the second radiation produced by the article with the extent of the covering material on the article changes however largely independent of the presence of the character indicating authenticity.

A second aspect of the invention is a device for monitoring articles to determine the presence of a character indicating the authenticity of the article, the at least one source for irradiating an article with an egg a radiation lying in at least a first and a second wavelength range; a first detector for detecting a first radiation generated by the article in response to the radiation in the first wavelength range, the first wavelength range being selected so that the generated first radiation is dependent on the presence or absence of authenticity indicative character and in response to the presence of masking material on the article; a second detector for detecting a second radiation generated by the article depending on the radiation in the second wavelength range; and comparison means for comparing the detected first and second radiation to determine whether or not the authenticity sign is present, characterized in that the second wavelength range is selected so that the second radiation generated by the article varies according to the extent of the covering material on the article changes, but is largely independent of the presence of the sign indicating authenticity.

We have found that it is possible to be authentic to be distinguished from non-authentic articles even if they have a covering material, e.g. B. pollution by things are irradiated in at least two different wavelength ranges, which have the properties specified above.

The first wavelength range is preferably outside the visible wavelength range, z. B. in the ultraviolet or infrared range. In principle, the However, radiation is somewhere in the electromagnetic spectrum. This is often important because the authenticity signs generally not visible in the visible wavelength range are because it is a hidden feature. The second Wavelength range often lies however in the visible wavelength range, because it is not essential in this area due to the authenticity mark affected becomes. In some cases, however both wavelength ranges inside or outside of the visible wavelength range lie.

If the first and second wavelength range close to each other has pollution in both wavelength ranges largely the same influence the radiation. The relationship between the first and second detected radiation is therefore independent on the extent of pollution (at least up to a certain limit), largely the same. This allows therefore a largely simple distinction between, for example real and fake Banknotes where the relationship between the first and second Radiation dependent of authenticity and not the extent of Pollution is different.

There can be separate sources can be used, but there is a particularly advantageous aspect of the invention in that one only source can be used, the one in both or all wavelength ranges generates lying radiation. For example, some conventional UV sources produce one in the UV wavelength range and also radiation in the visible range. The simplicity for the sake of reference, the following applies to the use of UV radiation taken, but it goes without saying that other wavelengths, individual or more that can be used instead.

Irradiation in all wavelength ranges and selective detection instead of irradiation in selected wavelength ranges, has the advantage that a mechanical scanning is eliminated, reduced sensitivity to stray light and manufacturing is simplified. Conveniently, this is achieved by the fact that the detectors are arranged filters.

Although it has been shown that normally two first wavelength ranges irradiation in more than two wavelength ranges can also be sufficient respectively. In some cases leads to this a more accurate determination of authenticity.

So in one embodiment, where radiation is applied in three wavelength ranges, normally two or three wavelength ranges chosen to be in Areas in which the radiation generated is present or lack of one or two authenticity marks and changes with the extent of the covering material. The third wavelength range lies in an area in which the generated radiation coincides with the Extent of Cover material changes, but the presence or absence of the two hardly changes authenticity indicating characters (authenticity indicator) changes.

Preferably the first and second detected radiation generated by the article the reflected radiation, the wavelengths of the reflected radiation depend on the properties (print, paper, etc.) of the item. In some cases The radiation also causes the print or the paper of the item lights up. It is possible to switch between fluorescence and phosphorescence by a suitable, known per se Distinguish modulation of radiation. The modulation can also to eliminate a malfunction applied by ambient light.

The first and second detected Radiation is preferably in the first and second wavelength range. In some cases However, the first and / or second detected radiation can be compared to the wavelength the corresponding radiation.

The relationship or relationship between the first and the second detected radiation can be determined in various ways become. In the case of a solution, the ratio of the intensity of the first and the second detected radiation is determined or determined. This ratio can then be compared to a predetermined threshold to determine whether the item is genuine or not. In another solution, a number of different properties of the first and second detected radiation can be determined, from which a measurement vector is formed for comparison with one or more measurement vectors which correspond to a real and / or known counterfeit article.

It should be noted that an important area of application the invention of monitoring Documents of value, e.g. B. banknotes. The invention can also for surveillance other types of articles are used, especially those that are printed with dyes, those that are visible and invisible Address wavelength range.

Exemplary embodiments of method according to the invention and devices described with reference to the accompanying drawings. In it represent:

1 1 shows a schematic view of a first example of the device,

2 1 shows a block diagram of a lamp control circuit,

3 1 shows a block diagram of a processing circuit,

4 a graph of the typical output spectrum of an unfiltered UV source,

5 Characteristic curves of two optical filters that can be used to determine the properties of the two second wavelength ranges (it should be noted that these two filters are only given as an example and other filter pairs or multiple filters may be more suitable in some applications),

6 a block diagram of a second example of the device and

7 that in the device after 4 applied wavelength ranges.

In the 1 The device shown contains two UV lamps 1 . 2 which are arranged at such an angle that their rays are directed to an area 3 are directed. The area 3 lies in the web of banknotes 4 that on a conveyor 5 , e.g. B. a strap through the area 3 to get promoted. Each lamp produces a range of wavelengths, as typically found in 4 are shown. In particular, it should be pointed out that radiation with a relatively high intensity is generated in a first wavelength range, the UV range (wavelengths of less than 380 nm), and a second wavelength range, the visible range (380 to 700 nm). In a first approximation, the overall shape of this spectrum does not change significantly with the temperature or aging of the lamps, even if the entire integrated output changes.

The one from the lamps 1 . 2 generated radiation is reflected by the banknote, the (first and second) wavelengths of the reflected radiation being independent of the dyes on the banknote and the banknote paper. The intensity of the reflected UV radiation depends on the authenticity of the dyes or the banknote paper and the extent of its contamination. The intensity of the reflected visible radiation essentially depends solely on the extent of the pollution. The radiation can also dye on the banknote 4 stimulate to glow. The reflected radiation and luminescence is generated by a focusing and detection system 6 receive. The system 6 has a tubular housing 7 , in the front end of an infrared cut filter 8th and a focusing lens 9 which the incoming radiation onto a UV-permeable filter 10 and a filter that is transparent to visible light 11 focused, whose characteristics in 5 are shown. Behind every filter 10 . 11 is a sensor 12 . 13 arranged. The feeler 12 generates an output signal that indicates the intensity of the incident UV light while the probe 13 generates an output signal that indicates the intensity of the incident visible light.

In a preferred solution the intensities simply compared the detected radiation, e.g. B. through education their relationship, which is then compared to a predetermined threshold to consider, whether the banknote is real or fake. For example, a real one Banknote cause a visible reflection that with the UV reflection is compared, as opposed to a fake, in which the intensities in the the two wavelength ranges are similar.

If the ratio exceeds the threshold, then a real banknote is displayed, e.g. B. a relatively large difference in reflection intensity in the two wavelength ranges.

As already mentioned, dyes can shine in one or both wavelength ranges when irradiated. The sensors can also receive and respond to ambient light. In the preferred solution, therefore, the light from the lamps 1 . 2 modulated so that a distinction can be made between ambient light and the light received in response to the irradiation, although this is not an essential part of the invention.

2 represents a simple circuit for modulating the light emitted by the lamp, the circuit being a clock pulse generator 20 has with a lamp control circuit 21 which in turn is connected to the lamps 1 . 2 connected is.

The feelers 12 . 13 are each with an amplifier 30 connected. The output signals of the two amplifiers are signal processing circuits 31 . 32 fed. These process the signals in such a way that a number of measured signal values are generated, ie quantities which relate to different properties of the amplifier output signals. The signal processing circuits can contain low-pass filters, high-pass filters, demodulators, integrators and other components known to those skilled in the art. The measured values include differently filtered versions of the amplifier output signals etc. and combinations of these signals (sums, differences, quotients etc.). In general, these signal processing circuits have no storage capability and the measurements change like the amplifier output signals, except for the relatively short delays inherent in processing. Signal processing can be done using analog or digital electronic hardware 33 or by means of software technology, which is most suitable in each case.

• a) den Modulationspegel des detektierten UV-Lichts,
• b) den Mittelwert oder gleichbleibenden Pegel des detektierten UV-Lichts,
• c) den Modulationspegel des detektierten sichtbaren Lichts und
• d) den Mittelwert oder gleichbleibenden Pegel des detektierten sichtbaren Lichts.

Typical information from the sensors 12 . 13 delivered include:

• a) the modulation level of the detected UV light,
• b) the mean value or constant level of the detected UV light,
• c) the modulation level of the detected visible light and
• d) the mean or constant level of the detected visible light.

This information can be used for Determination of certain measured values to be used.

Frequently is the most important measurement The relationship from a): c), but can b) and d) are also useful information. Because the UV channel to a range of wavelengths is sensitive, the output signal b) long-wave UV phosphorescence have, which is induced by a short-wave UV lighting. The measured value this UV phosphorescence results from the difference between the output signal b) and the output signal a). More like that Way is the difference between the output signals d) and c) a measure of a visible Phosphorescence.

The measured values are a measured value analysis circuit 33 supplied, which can also be supplied with other external signals (threshold values, position information from the document conveyor, etc.). This circuit arrangement processes the measured values individually or in combination to form a single output signal which indicates whether the banknote is valid or not.

Processing can be relatively easy be, signal levels with threshold values and measured values, the reflections in the two second wavelength ranges represent, compared, as described above. In some cases has been shown to be more complicated Process, e.g. B. processing several measured values together, their treatment as the only measured value vector instead of independent measured values, and the application of multidimensional grouping methods for determination the properties more valid and more famous fake Banknotes identifying a high percentage of counterfeits enable can. Such processing is usually done using of usual mathematical and software processes, including the use of artificial ones neural networks.

These measurements can only be made in one place one document or at several points in the document, while it the detector on a conveyor system happens. Such methods are known per se to the person skilled in the art.

The characteristic curve of the UV-permeable filter 10 is chosen so that the measurements are carried out in a part of the UV spectrum in which the difference in the reflectivity of real and falsified documents is greatest. The characteristic of the visible light-transmitting filter 11 is selected so that the measurements are carried out in an area in which a clearly visible output signal occurs.

In the example described above, two wavelength ranges are used. 6 represents a device in which the radiation emanating from the document is detected in three wavelength ranges. In the 6 circuit shown is in the 2 and 3 shown very similar and is used together with a similar arrangement as in 1 is shown. In this case, two lamps 101 . 102 , preferably in the form of discharge lamps containing gas, e.g. B. neon, used for irradiation or illumination of the document. Each lamp produces radiation with a number of narrow peaks in wavelength ranges from below 330 nm to over 800 nm, although other broadband sources can also be used. The lamps are controlled by a lamp control circuit 103 controlled with a clock pulse generator 104 connected is. The radiation emanating from the document is passed through a filter 108 to 110 fed three photodiodes. The passband of these filters are in 7 from which it can be seen that these passbands do not overlap. The pass band of the filter 108 is at 111 , the pass band of the filter 109 at 112 and the pass band of the filter 110 at 113 shown.

The output signals of the photodiodes 105 to 107 are each through an amplifier 114 to 116 amplified and each have a signal processing circuit 117 to 119 fed. The signals are then an analysis circuit 120 fed which the in 3 shown analysis circuit 33 similar.

If the illumination or radiation is measured in three (or more) wavelength ranges, the simplest way of processing is to calculate the ratios of the intensities in each of the wavelength ranges 111 to 113 , in the If the generated radiation changes with the presence or absence of the authenticity sign, to the ratio in the wavelength range in which the generated radiation changes with the amount of masking material, but not significantly with the presence or absence of the authenticity sign , These ratios are then compared to the predetermined thresholds to determine if the item is genuine. In this case, however, it is normally more advantageous to use a method in which a measured value vector is formed from several different properties of the detected radiation and is then compared with one or more measured value vectors which correspond to real and / or fake articles.

The invention is of many different types of article surveillance systems applicable, including Document sorters and acceptors, as well as cash handling facilities, like counting, Sorting, output and Akzeptiergeräten. The invention is particularly for monitoring Banknotes suitable.

Claims (19)

Article monitoring procedures ( 4 ) to determine the presence of a sign indicating authenticity, in which an article is irradiated with radiation lying in at least a first and a second wavelength range; a first radiation generated by the article in response to the radiation in the first wavelength range is detected; the first wavelength range is selected so that the generated first radiation changes depending on the presence or absence of the authenticity sign and in response to the presence of a masking material on the article; the second radiation generated by the article in response to the irradiation in the second wavelength range is detected and the detected first and second radiation are compared to determine whether or not the authenticity sign is present, characterized in that the second wavelength range is so it is chosen that the second radiation generated by the article changes with the extent of the covering material on the article, but is largely independent of the presence of the sign indicating authenticity. The method of claim 1, wherein the first wavelength range outside of the visible wavelength range lies. The method of claim 1 or claim 2, wherein the second wavelength range in the visible wavelength range lies. Method according to one of the preceding claims, which the first detected radiation outside the visible wavelength range lies. Method according to one of the preceding claims, which is the second wavelength range in the visible wavelength range lies. Method according to one of the preceding claims, which the first radiation largely in the first wavelength range lies. Method according to one of the preceding claims, which the second radiation largely in the second wavelength range lies. Method according to one of the preceding claims, which in at least the first or second wavelength range lying radiation is reflected by the article, respectively at least part of the first and second detected radiation to build. Method according to one of the preceding claims, which the detected radiation includes luminescence. Method according to one of the preceding claims, the furthermore modulating the emitted radiation and detecting a received radiation that has essentially no modulation and / or a similar Has modulation comprises. Method according to one of the preceding claims, which comparing determining the ratio of the intensities of the includes first and second detected radiation. Method according to one of the preceding claims, the further determining the relationship of the result of the comparison with an expected relationship that corresponds to an acceptance condition. The method of claim 12, referring back to claim 11, where determining the relationship comparing the ratio with a threshold value. Method according to one of the preceding claims, where the radiation comes from a single source. Method according to one of the preceding claims, which the radiation is detected in at least three wavelength ranges. Method according to one of the preceding claims, which the article is a sheet, e.g. B. a document of value, e.g. B. a banknote, having. Article monitoring device ( 4 ) to determine the presence of a character indicating the authenticity of the item, the at least one source ( 1 . 2 ) for irradiating an article with radiation lying in at least a first and a second wavelength range; a first detector ( 12 ) for detecting a first radiation generated by the article in response to the radiation in the first wavelength range, the first wavelength range being selected so that the generated first radiation is dependent on the presence or absence of the sign indicating authenticity and changes in response to the presence of a masking material on the article; a second detector ( 13 ) for detecting a second radiation which is generated by the article as a function of the radiation in the second wavelength range; and a comparison means ( 33 ) for comparing the detected first and second radiation to determine whether or not the authenticity-indicating sign is present, characterized in that the second wavelength range is selected so that the second radiation generated by the article is in accordance with the extent of the covering material changes on the article, but is largely independent of the presence of the character indicating authenticity. The apparatus of claim 17, wherein a first and a second source ( 1 . 2 ) are formed by a common source. Apparatus according to claim 17 or claim 18 which to carry out of the method according to one of claims 1 to 16 is suitable.