More particularly, the invention provides a dedicated, low-cost hand-held optical device which illuminates indicia printed with security ink and measures the spectral absorption thereof at a plurality of discrete wavelengths. The device then compares these results with results to be expected from the scanning of the same defined feature of an authentic banknote. A display or other means, informs the user whether or not the discrepancy between results and pre-stored values is within naturally occurring variations.

The authenticity of banknotes is protected by a variety of security features, which may include security paper, security inks, the inclusion of security threads, foils and planchettes. While many of these features can make the task of criminal counterfeiters very difficult, it must be remembered that counterfeiting is sometimes engaged in by hostile governments (at the time of writing North Korea) as an act of war. Governments often have the resources to produce forged banknotes which are difficult to distinguish from genuine currency.

Because billions of banknotes change hands daily, any method of checking authenticity thereof must be fast and easy to use. Consequently there is a market for validator devices which meet these requirements. Both hand-held and desktop machines are presently in use, while small businesses typically accept banknotes after a cursory visual inspection.

The present state of the art is fairly represented by recent US Patents as follows.

In US Patent no. 5, 152, 607 Crane et al. disclose a device for verifying the presence of an embedded metal thread. In US Patent 5, 308,992 they describe an

apparatus wherein a photodiode and a phototransistor are positioned on opposite sides of the banknote being checked.

Kamagami et al. propose in US Patent no. 5, 199, 543 to scan and read all the printed patterns of a bill. Reference data storage memory is used to check each data block.

Eccles discloses a probabilistic neural network in US Patent No. 5, 619,620 which is intended to be used for banknote authentication.

Tod et al disclose a banknote validator in US Patent No. 5, 657, 847. Banknotes are inserted into a U-shaped path wherein a light source and a light receiving station measures reflected light.

In US Patent No. 6,070, 710 Hutchinson proposes to execute repeated photoelectric measurements of light intensity by measuring the time taken to charge or discharge a capacitor.

A banknote validator which includes an optical sensor, a trapezoidal light guide, filters and a broadband light source is seen in US Patent No. 6,392, 863 to Dunlop et al.

Mechanisms are provided for moving the banknote in and out of the machine.

Small businesses are at greater risk from counterfeiters than large organizations such as banks and supermarkets as those wishing to make use of forged banknotes consider the small business an easier target while at the same time the loss sustained from the acceptance of such"banknotes"has a deeper negative impact on profitability. Large businesses have little difficulty in funding the purchase of multi-purpose desktop machines, for example of the type seen in the Dunlop patent. Small businesses however may not have the room for desktop machines, and are unlikely to purchase devices of any type due to cost considerations. Known handheld devices are expensive because they are produced in moderate quantities to serve a defined user group, for example brand product security personnel, inspectors of government documents, or for preventing the use of forged event entrance tickets. Multi-purpose authenticators require customizing hardware, software or both for use on specific applications, customization being responsible for a substantial share of their high cost.

It is therefore one of the objects of the present invention to obviate the disadvantages of prior art banknote validators and to provide a hand-held device which is dedicated to check a single feature and is thus manufacturable at moderate cost.

It is a further object of the present invention to examine features printed using security ink, which features cannot be examined visually.

The present invention achieves the above objects by providing a single-purpose hand-held banknote validator for banknotes printed at least partly with security ink, comprising; *a housing *a broadband light source and focusing optics for emitting light of different wavelengths, or *a plurality of light sources with narrow spectral outputs and focusing optics positioned proximate to an extremity of said housing; *at least one photo-detector for detecting scattered light intensity at predefined discrete wavelengths, positioned adjacent to said light source; *an electronics package inside said housing including signal processing means, a programmed microprocessor, a power source, and results indicating means; and *a manual activation switch.

In a preferred embodiment of the present invention there is provided a method for the validation of banknotes printed at least partly with security ink, comprising the steps a. providing an instrument similar to that described in claim 1 ; b. programming the microprocessor to recognize acceptable relationships between wavelength and light intensity and to activate the display appropriately when results fall within predefined tolerances; c. switching power on; d. scanning predefined sections of a banknote printed with security ink, resulting in the production of digital representations of the relationship between wavelength and light intensity at pre-defined wavelengths, these received values being compared to acceptable relationships; and e. observing the displayed results.

Yet further embodiments of the invention will be described hereinafter.

The invention utilizes the fact that security inks with spectrally varying absorption are used in some banknotes. Broadband absorption features useful for security are usually found in the infrared. Two features of a banknote may have identical visible coloring yet differ greatly in infrared absorption. The large numerals printed on the 20 Euro denomination are an example thereof. The two digits have identical visible coloring, yet the absorption of infrared light by the 0 is much larger than that of the 2. This feature, illustrated in FIG. 7 and further explained with reference thereto, can be utilized by the device of the present invention for checking banknotes.

Narrow-band absorption features can be found in either the infrared or the ultraviolet. Narrow-band features have absorption spectra which vary sharply over a small wavelength range. An example of such a feature is the seal of the US Federal Reserve System to the left of the portrait of Andrew Jackson in the US $20 denomination, in which such a variation occurs in the near infrared. This feature, illustrated in FIG. 8 and further explained with reference thereto, can be utilized by a further embodiment of the device of the present invention. In any case, the device of the present invention will discriminate between two banknotes, one of which is forged, even though an extended visual examination of the banknotes will yield no clue as to any difference between the two.

The invention will now be described further with reference to the accompanying drawings, which represent by example preferred embodiments of the invention. Structural details are shown only as far as necessary for a fundamental understanding thereof. The described examples, together with the drawings, will make apparent to those skilled in the art how further forms of the invention may be realized.

In the drawings: FIG. 1 is a schematical perspective view of a preferred embodiment of the banknote validator according to the invention;

FIG. 2 is a block diagram illustrating an embodiment of the device FIG. 3 is a block diagram representing a filtered embodiment of the invention; FIG. 4 is a perspective view of an embodiment having a simplified visual display; FIG. 5 is a block diagram of an embodiment having an audible display FIG. 6 is a perspective view of an embodiment operated by a slide switch ; FIG. 7 is a graph showing the near infrared spectrum of light scattered from the large digits 2 and 0 on the 20 Euro denomination; and FIG. 8 is a graph showing the near-infrared spectrum of light scattered from a defined portion of a US $20 denomination.

There is seen in FIG. 1 a single-purpose hand-held banknote validator 10 for banknotes printed at least partly with security ink.

A housing 12, wherein the forward compartment 14 contains the optics, the rear compartment 16 contains the power source such as a battery (ies) 17 FIG 3, which can be rechargeable, and the intermediate compartment 18 the electronics, holds all parts of the device. The housing can be made similar in size and shape to a penlight. The housing shown 12 is basically hollow, and has a small opening 20 adjacent the focus of the light emitter 22. Preferably as many of the components as practically possible are molded together with the housing 12 for purposes of cost reduction. In the shown embodiment the cover 24 of the rear compartment is molded together with the housing and is attached thereto by a"living"hinge 26.

The light emitter 22 comprises a broadband light source and focusing optics for emitting light of different wavelengths, and is disposed proximate to a first extremity 28 of the housing 12.

A plurality of photo-detectors 30 for detecting reflected light intensity at predefined discrete wavelengths are positioned adjacent to the light source.

The electronics package (31, FIG. 3) inside the intermediate compartment 18 includes signal processing means, a pre-programmed microprocessor and results display means 32. In the present embodiment the results display means 32 comprises a digital display, which can be used for purposes additional to the essential"ok"message. For example,

the display can carry a"low battery"warning. Such means could also be audio means of different sounds.

The electronics are factory programmed to check a single or multiple pre-defined feature of a banknote, and no customization is carried out.

The manual activation switch is a push button 34 which connects the power source to the electronics. The power source could be a battery or direct connection to the mains.

With reference to the rest of the figures, similar reference numerals have been used to identify similar parts.

Referring now to FIG. 2, which diagramatically illustrates an embodiment wherein the required measurements are carried out at predetermined wavelengths selected by means of narrow-band light sources, e. g., LED's. The light sources are activated sequentially. Such an arrangement is beneficial as it permits the use of a single photodetector.

FIG. 3 diagrammatically illustrates an embodiment 44 wherein the required measurements are carried out at predefined wavelengths selected by means of filters 46, 48,50. Such an arrangement is beneficial because it opens the possibility of using several identical broad-band light detectors 52 instead of several detectors each arranged to be sensitive to light at different wavelengths.

Seen in FIG. 4 is an embodiment of the banknote validator 54, wherein the results display means comprises a red and a green LED 56,58. The two LEDS save the expense of the digital display, and provide the basic information needed by the user. In a further embodiment, not shown, a single LED is used which changes color in accordance with results calculated by the microprocessor.

Referring now to FIG. 5, there is represented a further embodiment of the banknote validator, wherein the results display means comprises an audio output 60. A

suitable arrangement is to provide a buzz activated when a valid banknote is scanned. No visual display is needed.

FIG. 6 shows an embodiment wherein the switch is a slide switch 66, which is more convenient than the push-button switch 34 seen in FIG. 1 for extended use. In order to prevent battery rundown when the device is not in use, the electronics package includes an automatic off switch (not seen) activated when the validator has been left with power on but has not been used for scanning for about one minute.

The present invention further includes a method for the validation of banknotes printed at least partly with security ink.

The method includes the following steps.

STEP A. Providing an instrument similar to that described with reference to FIG. 1.

STEPB. Programming the microprocessor to recognize acceptable relationships between wavelength and light intensity and to activate the display appropriately when results fall within or outside predefined tolerances. Programming relates to the following: * The banknote and the specific feature to be examined.

* The number of absorption measurements required, and the wavelength of each.

* The expected natural variations when examining genuine banknotes.

STEP C. Switching power on.

STEP D. Scanning predefined sections of a banknote printed with security ink, resulting in the production of digital representations of the relationship between wavelength and light intensity at pre-defined wavelengths, these received values being compared to the acceptable relationships. Scanning is carried out with the head of the instrument very close to or in contact with the banknote.

STEP E. Observing the displayed results.

It should be noted that steps A and B are carried out by the manufacturer while all others are performed by the user.

Turning now to FIG. 7, the graph presents the near infrared spectrum of light scattered from the large digits 2 and 0 on the 20 Euro denomination, as measured by an Ocean Optics S2000 spectrometer. Absorption of light within the 800-1000 nanometer range is much larger for the 0 than for the 2. Comparisons of light scattered at wavelengths such as 700,800, 900 and 1000 nanometers for each of the two digits is the preferred basis for authentication for this note.

Referring now to FIG. 8, there is seen a further graph which presents the near- infrared spectrum of light scattered from the black ink of the seal of the US Federal Reserve System to the left of the portrait of Andrew Jackson in the US $20 denomination.

Measurements were taken again using the Ocean Optics S2000 spectrometer. There is an absorption feature with maximum absorption at approximately 820 nanometeres.

Checking absorption in this region can be used to verify the presence of security ink. The $20 note can thus be satisfactorily checked when measured at some or all of the wavelengths 700,770, 820 and 900 nanometers.

Generally, narrow-band features have absorption spectra which vary sharply over a small wavelength range, as in the $20 banknote, and typically these useful features are found in the near infrared.

The scope of the described invention is intended to include all embodiments coming within the meaning of the following claims. The foregoing examples illustrate useful forms of the invention, but are not to be considered as limiting its scope, as those skilled in the art will readily be aware that additional variants and modifications of the invention can be formulated without departing from the meaning of the following claims.