JP2002510102A - Method and apparatus for inspecting articles - Google Patents

Abstract

(57) Abstract: A method and apparatus for inspecting an article to determine the presence of a property indicating authenticity. The method includes irradiating the article with radiation in at least first and second wavebands, and detecting a first radiation generated by the article in response to irradiating in the first waveband, the method comprising: The first waveband is selected such that the first radiation varies in accordance with the presence or absence of the characteristic indicating authenticity and further in response to the presence of obscuring material on the article. And detecting. A second radiation generated by the article in response to irradiation in the second waveband is detected, and the second radiation generated by the article varies depending on the degree of obscuring material on the article. However, the second waveband is selected so that it is substantially independent of the presence of the authenticity feature. The detected radiation is compared to determine if a characteristic indicating authenticity is present.

Description

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to a method and an apparatus for inspecting articles, for example valuable documents such as banknotes.

[0002] The principles of using reflectance measurements to verify the authenticity of security documents are well known. The properties of security paper are such that in some ranges of the spectrum (UV, visible and IR) the reflectance is different from that of many non-security papers used to create fake documents. Things.

For example, a simple authenticity verification system can be made by illuminating a document with a UV light and measuring the reflection intensity. If this intensity exceeds a predetermined threshold level, the document is considered authentic (but note that in certain circumstances, fake documents may have higher reflectivity). Measurements with the natural UV excitation fluorescence of the paper can be performed at the same time, ie the most secure paper has a low level of natural fluorescence. This "UV emission" measurement technique is also well known.

[0004] The simple technique outlined above has several drawbacks in any practical application. The two most important are shown below. The intensity of the reflection from any given document is also dependent on the characteristics of the measurement system, some of which vary significantly. For example,
The output intensity of most UV sources varies with temperature and also with the age of the source. The characteristics of the optical components used (filters, windows, lenses, etc.) also change with their age. In use, dirt and dust formed on optical surfaces reduces the measured intensity. -The reflection intensity depends on the stain on the document. The more dirty the document, the lower the reflectance.

[0005] Changes in the sensitivity of the measurement system may be reduced by an automatic calibration system that continuously monitors the signal level measured on the reference surface, but to provide a continuously clean reference surface. Is difficult and expensive. Such systems, of course, cannot compensate for any dirt on the document.

[0006] The combined effects reduce the discriminating power of the sensing system. If the detection threshold is set high enough to detect the cleanest fake with the new clean (high sensitivity) system, a relatively large portion of the genuine dirty notes will be mistaken. Will be considered as counterfeit, i.e. this part will increase as the detection system increases in age or becomes dirty. If only a small part of a real note is mistakenly considered a fake by an old dirty (low sensitivity) system,
If the threshold is lowered, an unacceptably large portion of the fake will be considered authentic by the clean system.

[0007] US-A-4723072 discloses an apparatus for measuring the soiling of banknotes using one or more sensors operating in the same optical waveband (frequency band). The invention does not relate to the measurement of dirt.

US-A-3679314 illuminates a selected portion of a note portion continuously using light beams having different spectral distributions, and then transmits or transmits light through the illuminated portion. An apparatus for optically testing the authenticity of a banknote by detecting light affected by the banknote is disclosed. The problem with this study is that in order to control the irradiation of the bill, it is necessary to scan a pair of filters that mechanically cross the irradiation beam.

In accordance with one aspect of the present invention, a method of inspecting an article to determine the presence of a signature indicating authenticity includes irradiating the article with radiation in at least first and second wave bands; The first generated by the article in response to the irradiation in the band
Detecting the radiation of the first wave, such that the first radiation generated varies in accordance with the presence or absence of the characteristic indicating authenticity and further in response to the presence of the obscuring material on the article. Detecting a first radiation in which a band is selected and detecting a second radiation generated by the article in response to the illumination in the second waveband, wherein the second radiation generated by the article is Detecting a second radiation, wherein the second waveband is selected so as to vary with the degree of obscuring material on the article, but substantially independent of the presence of the authentic characteristic And comparing the detected first and second radiations to determine if there is a characteristic indicating authenticity.

In accordance with a second aspect of the present invention, an apparatus for inspecting an article for determining the presence of a property indicating authenticity includes at least one apparatus for irradiating the article with radiation in at least first and second wavebands. Two sources and a first detector for detecting a first radiation generated by the article in response to the irradiation in the first waveband, wherein the first radiation generated identifies the real radiation. A first detector in which the first waveband is selected to vary in response to the presence or absence of the indicated property and further in response to the presence of the obscuring material on the article; A second detector for detecting a second radiation generated by the article in response to the irradiation of the article, wherein the second radiation generated by the article is characterized by a degree of obscuring material on the article. Varies, but A second detector from which the second waveband is selected, and to determine whether a genuine indicator is present, such that it is substantially independent of the presence of the genuine indicator. Comparing means for comparing the detected first and second radiations.

By irradiating the article with at least two different wavebands having the properties defined above, it is possible to distinguish between genuine and non-genuine articles, even with obscuring substances such as dirt. We have found that

Generally, the first waveband is outside the visible wavelength range, for example, in the ultraviolet or infrared range. In essence, the illumination is somewhere in the electromagnetic spectrum. This is often important because real properties are generally not visible in the visible wavelength range due to their hidden features. However, the second waveband is often in the visible wavelength range, because in the visible wavelength range it is substantially unaffected by the authentic properties. In some cases, however, both wavebands may be within or outside the visible wavelength band.

[0013] Assuming that the first and second wavebands are close together, dirt has substantially the same effect on radiation in the two wavebands. Thus, the relationship between the first and second detected radiations is substantially similarly unrelated to the degree of contamination (
At least up to certain limits). This then provides a very convenient way of discriminating between genuine and counterfeit banknotes, for example, in which case the relationship between the first and the second radiation is subject to authenticity. Depending on the amount of contamination.

Although separate sources can be used, in a particularly advantageous form of the invention, a single source that produces radiation in both or all wavebands can be used. For example, some conventional UV sources produce radiation in the UV waveband, and even in the visible region. Although the use of UV radiation is described below for simplicity, it should be understood that other wavelengths or wavelengths could alternatively be used.

[0015] Illumination and selective detection in all wavebands avoids the need for mechanical scanning (scanning), rather than illumination in selected wavebands, and provides side-by-side light. To reduce the susceptibility to data processing and further simplify processing. Advantageously, this can be achieved by placing a filter in front of the detector.

Although it has been found that usually two first wavebands are sufficient, irradiation with more than one waveband can be performed. In some cases, this can determine the authenticity more accurately.

For example, in an embodiment where illumination is used in three wavebands,
Two of the three wavebands are divided into regions where the generated radiation varies due to the presence or absence of one of each of the two authentic characteristics, and regions which vary according to the degree of obscuring material. Is usually selected to be present. The third waveband is in a region where the generated radiation varies with the degree of material obscuring, but the waveband does not change substantially due to the presence or absence of the two authentic features. .

Generally, the first and second detected radiation generated by the article comprises reflected radiation, the wavelength of the reflected radiation being characteristic of the article (print, paper, etc.). Depends on. In some cases, the irradiation also causes the print or paper on the article to glow. By properly adjusting the illumination in a known manner, it would be possible to distinguish between fluorescence and phosphorescence. The adjustment can also be used to eliminate the effects of environmental light.

[0019] The first and second detected radiations are generally in first and second wavebands, respectively. However, in some cases, one or both of the first and second detected emissions may be offset in wavelength from the corresponding illumination.

The relationship between the first and second detected emissions can be determined in various ways. In one consideration, a ratio of the intensity of the first and second detected radiation is determined. The ratio is then compared to a predetermined threshold to determine if the article is genuine. In another alternative, many different properties of the first and second detected emissions can be determined, from which the measurement vector can be determined to include one or more corresponding real and / or known counterfeit articles. It is produced for comparison with the measurement vector of.

An important application of the present invention is in the inspection of valuable documents such as banknotes, but the present invention is also directed to other types of articles, particularly inks that correspond to both visible and non-visible wavebands. It is recognized that the present invention is applicable to inspection of what is printed. Some examples of the method and apparatus according to the invention are described below with reference to the accompanying figures.

The device shown in FIG. 1 comprises a pair of UV lamps 1, 2, which are installed at an angle so that the radiation produced by the lamps is directed to region 3. Area 3
Is installed in a passage (path) of the banknote 4 that is conveyed through the area 3 on the moving conveyor 5 such as a belt. Each lamp typically produces a wavelength range as shown in FIG. In particular, the relatively high intensity radiation is in the first waveband (frequency band),
The V band (wavelength below about 380 nm) and the second wave band, ie, the visible range (
It can be seen that it is generated within a wavelength of about 380 to 700 nm). As a first approximation, the overall shape of this spectrum will change even if the overall integrated output changes.
It does not change significantly with temperature or age of the lamp.

The radiation generated by the lamps 1, 2 is being reflected by the banknote, and the (first and second) wavelengths of the reflected radiation depend on the paper of the banknote and the ink on the banknote. UV reflected
The intensity of the radiation corresponds to the authenticity of the paper of the ink or banknote and the degree of soiling. The intensity of the reflected visible radiation depends substantially solely on the degree of soiling. The radiation may also stimulate the ink on the banknote 4 to emit light. The reflected radiation and emission are received by a focusing and sensing system 6. The system 6 comprises a tubular housing 7 with an infrared stop filter 8 and a focusing at the top of the housing.
5.) A lens 9 is provided, which focuses the incident radiation on a UV pass filter 10 and a visible pass filter 11, the characteristics of which are shown in FIG. Each sensor 12, 13 is located behind a filter 10, 11.
Sensor 12 thus displays the output of the intensity of the incident UV light, while sensor 13 displays the output of the intensity of the incident visible light.

In one preferred consideration, the intensity of the detected radiation is simply compared, for example by taking their ratio, and this ratio is then determined in advance to determine whether the bill is genuine. It is compared to the determined threshold. For example, genuine banknotes have a U.S.A.
It may have a visible reflection that is higher than the V reflection. If the ratio exceeds the threshold, this indicates a real note, ie there is a relatively large difference in reflection intensity in the two wavebands.

As mentioned above, certain inks can emit light upon irradiation in one or both wavebands. In addition, the sensor may receive and respond to ambient light. In a preferred design, the lamps 1, 2 are thus adjusted so that it is possible to distinguish between the light of one environment and the light received in response to the illumination of the other, which is a fundamental part of the invention. is not.

FIG. 2 shows a simple circuit for regulating the lamp output, which comprises a time generator 20 connected to a lamp control circuit 21, which in turn comprises a lamp 1, Connect to 2.

Each of the sensors 12 and 13 is connected to an amplifier 30. The outputs of the two amplifiers are output to respective signal processing circuits 31 and 32. These process the signal to generate multiple signal measurements, the quantities being related to different characteristics of the amplifier output. The signal processing circuit may include a low (low frequency band) pass filter, a high (high frequency band) pass filter, a demodulator (demodulator), an integrator (integrator), and other techniques well known to those skilled in the art. The measurements include differentially filtered versions of the amplifier output, etc., and combinations thereof (sum, difference, quotient, etc.).
In general, these signal processing circuits do not have storage capacity and the measurement changes when the amplifier output changes, apart from the relatively short delay inherent in processing. Such signal processing may be implemented using analog or digital electronic hardware 33 or using software techniques, depending on convenience.

General information that can be obtained from the sensors 12, 13 includes: (A) Modulation level of detected UV light (light) (b) Average or DC, level of detected UV light (c) Modulation level of detected visible light (d) Detected visible Light average, or DC, level These can be used to get some kind of measurement.

The most important measurement is often the ratio (a) :( c), but (b) and (d)
) Can also provide some useful information. Since the UV channel is sensitive to a range of wavelengths, the output (b) can include contributions from any "long" UV wavelength phosphorescence caused by "short" UV wavelength illumination. This "UV phosphorescence" measurement is given by the difference between output (b) and output (a). Similarly, the difference between outputs (d) and (c) is a measure of any visible phosphorescence.

The measurements are output to the measurement and analysis electronics 33, which may also have other external signal inputs (threshold levels, position information from the document transport system, etc.). This circuit processes the measurements individually or in combination to generate one output signal indicating whether the bill is genuine.

The process may be relatively simple and comprises a comparison of the signal level with the threshold level and a comparison of the measurements representative of the reflections in the two second wavebands, as described above. In some cases, processing several measurements together to define the properties of real and known fake notes, treating them as a single measurement vector rather than as independent measurements, Multidimensional clustering (
It has been found that more complex techniques, such as those using clustering techniques, can identify a high percentage of fakes. Such processing is commonly performed using standard mathematical and software techniques, and involves the use of artificial neural nets.

These measurements may be performed at one location on the document as it passes the detector through the transport system, or at many locations. Such techniques are well-known to those skilled in the art.

The response of the UV pass filter 10 is chosen such that the measurement is performed in the part of the UV spectrum where the difference between the reflectance of the real and fake documents is greatest. The response of the visible pass filter 11 is selected so that the measurement is performed in a region where there is significant visible output.

In the above example, two frequency bands were used. FIG. 6 shows an apparatus for detecting radiation from a document in three wavebands. The circuit shown in FIG. 6 is very similar to that shown in FIGS. 2 and 3, and this circuit is used in an arrangement similar to that shown in FIG. In this case, the pair of lamps 101, 102 is generally in the form of a discharge lamp containing a gas such as neon and is used to irradiate a document. Each lamp produces radiation in a number of narrow peaks at wavelengths below 330 nm to above 800 nm, despite the availability of another broad band source. The lamp is controlled by a lamp control circuit 103 connected to a clock 104. The radiation from the document is
The light passes through 110 to three photodiodes 105 to 107. The passbands of these filters are shown in FIG. 7, where it can be seen that these passbands do not overlap. The passband for filter 108 is shown at 111, the passband for filter 109 is shown at 112, and the passband for filter 110 is shown at 113.

Output signals from the photodiodes 105 to 107 are output to respective amplifiers 114.
, And are passed to the respective signal processing electric circuits 117 to 119. The signal is then applied to the analysis circuit 12 similar to the circuit 33 shown in FIG.
Pass through to zero.

If the illumination is measured in three (or more) wavebands, the simplest form of processing involves calculating the ratio of the intensities of each waveband 111-113, where the waveband The generated radiation is genuine relative to the intensity in the waveband, which varies with the degree of material that the generated radiation obscures, but does not substantially change by the presence or absence of the characteristic that indicates it. Varies by the presence or absence of the indicated property. These ratios are then compared to a predetermined threshold to determine if the article is authentic. However, it is usually more convenient in this case to use a technique in which the measurement vector is made from several different properties of the detected radiation, after which the measurement vector can be transferred to real and / or fake articles. It is compared with one or more corresponding measurement vectors.

The present invention provides many different forms of article inspection systems, including document sorters and acceptors, as well as counters, sorters, dispensers, receivers, and the like. Applicable to cash handling equipment.
The invention is particularly suitable for checking banknotes.

[Brief description of the drawings]

FIG. 1 is a schematic drawing of a first example of the device.

FIG. 2 is a block circuit diagram showing a lamp control circuit.

FIG. 3 is a block diagram illustrating a processing circuit.

FIG. 4 graphically illustrates a typical output spectrum of an unfiltered UV source.

FIG. 5 graphically illustrates the properties of a pair of optical filters that can be used to characterize two second wavebands. (It should be recognized that this particular pair of filters is provided as an example only and that another pair or multiple filters may be more suitable for some applications.)

FIG. 6 is a schematic block diagram of a second example of the device.

FIG. 7 illustrates the wavebands used in the apparatus of FIG.

──────────────────────────────────────────────────続 き Continuation of front page (81) Designated country EP (AT, BE, CH, CY, DE, DK, ES, FI, FR, GB, GR, IE, IT, LU, MC, NL, PT, SE ), OA (BF, BJ, CF, CG, CI, CM, GA, GN, GW, ML, MR, NE, SN, TD, TG), AP (GH, GM, KE, LS, MW, SD, SL, SZ, UG, ZW), EA (AM, AZ, BY, KG, KZ, MD, RU, TJ, TM), AE, AL, AM, AT, AU, AZ, BA, BB, BG, BR , BY, CA, CH, CN, CU, CZ, DE, DK, EE, ES, FI, GB, GD, GE, GH, GM, HR, HU, ID, IL, IN, IS , JP, KE, KG, KP, KR, KZ, LC, LK, LR, LS, LT, LU, LV, MD, MG, MK, MN, MW, MX, NO, NZ, PL, PT, RO, RU, SD, SE, SG, SI, SK, SL, TJ, TM, TR, TT, UA, UG, US, UZ, VN, YU, ZA, ZW (72) Inventor Reeves, David Charles United Kingdom, Hampshire P.O. 8 BG, Waterlooville, Goodwood Close 27 F-term (reference) 3E041 AA03 BB03

Claims (19)

[Claims] 1. A method of inspecting an article for determining the presence of a property indicative of authenticity, the method comprising: irradiating the article with radiation in at least first and second wavebands. Detecting the first radiation generated by the article in response to the irradiation in the first waveband, wherein the first radiation generated further comprises: The first waveband is selected to be varied in response to the presence of the obscuring material, and is generated by the article in response to detecting the first radiation and irradiating with the second waveband. The detection of a second radiation, wherein the second radiation produced by the article depends on the degree of the obscuring material on the article, but the presence of a property indicating authenticity Detecting the second radiation such that the second waveband is selected to be substantially independent, and further detecting the first and second sensed first and second signals to determine if there is a characteristic indicating authenticity; A method for inspecting an article comprising: 2. The method according to claim 1, wherein the first waveband is outside the visible wavelength range.
The method described in. 3. The method according to claim 1, wherein the second waveband is in the visible wavelength range. 4. The method of claim 1, wherein the first detected radiation is outside the visible wavelength range.
The method according to any one of claims 1 to 3. 5. The method according to claim 1, wherein the second waveband is in the visible wavelength band. 6. The method according to claim 1, wherein the first radiation falls substantially within the first wavelength band. 7. The method according to claim 1, wherein the second radiation falls substantially within the second wavelength band. 8. The method of claim 1, wherein radiation in at least one of the first and second wavebands is reflected by the article and comprises at least a portion of the first and second detected radiation, respectively. A method according to any one of the preceding claims. 9. The method according to claim 1, wherein the detected radiation comprises luminescence. 10. The method according to claim 1, further comprising adjusting the emitted radiation and detecting the radiation received in a substantially unadjusted state and / or in a similar adjusted state. Method. 11. The method according to claim 1, wherein the step of comparing comprises determining a ratio between the intensity of the first and second detected radiation. 12. The method according to claim 1, further comprising determining a relationship of a result of the comparison procedure with an expected relationship corresponding to a condition of acceptance. 13. The method according to claim 12, wherein, if dependent on claim 11, the relation determination procedure comprises comparing the ratio with a threshold value. 14. The method according to claim 1, wherein the irradiation is generated from a single source. 15. The method according to claim 1, wherein radiation in at least three wavebands is detected. 16. A method according to any one of the preceding claims, wherein the article comprises a sheet, such as a valuable document, such as a banknote. 17. An apparatus for inspecting an article for determining the presence of a genuinely indicative characteristic, the apparatus comprising at least one generator for irradiating the article with radiation in at least first and second wavebands. A source and a first detector for detecting a first radiation generated by the article in response to the irradiation in the first waveband, wherein the generated first radiation is authentic. A first detector in which the first waveband is selected to vary according to the presence or absence of the property and further in response to the presence of the obscuring material on the article; and illumination in the second waveband. A second detector for detecting a second radiation produced by the article in response to the second radiation, wherein the second radiation produced by the article varies according to the degree of obscuring material on the article. Do, but The second waveband is selected such that it is substantially independent of the presence of the authenticity feature.
An apparatus for inspecting an article, comprising: a detector of claim 1; and comparing means for comparing the detected first and second radiations to determine whether a genuine property is present. 18. The apparatus according to claim 17, wherein the first and second sources are formed by a common source. 19. Apparatus according to claim 17 or 18, adapted to carry out the method according to any one of claims 1 to 16.