WO2003084767A2

WO2003084767A2 - Verify security documents by means of polarised light

Info

Publication number: WO2003084767A2
Application number: PCT/IT2003/000202
Authority: WO
Inventors: Valentino Soramae'
Original assignee: Numerouno Gruppo Di Comunicazione, S.R.L.
Priority date: 2002-04-05
Filing date: 2003-04-03
Publication date: 2003-10-16
Also published as: ITVR20020031A1; EP1503904A2; AU2003230197A8; ITVR20020031A0; AU2003230197A1; WO2003084767A3

Abstract

A process for the recognition of elements marked with OVItm (Optical Variable Ink) comprising the following steps: - production of a ray of polarised light by the use of a first polarising filter (13) on a source of light; - exposure of the part of the document or banknote marked with OVItm type inks to the ray of polarised light; - additional filtering of the light reflected by the document or the banknote by means of a second polarising filter (14) placed at an appropriate reciprocal angle with respect to the degree of polarisation of the incident light; - detection of the variation in luminescence.

Description

"PROCESS TO VERIFY SECURITY DOCUMENT MARKED WITH OVI™ (OPTICAL VARIABLE INKS) BY MEANS OF POLARISED LIGHT, AND DEVICE FOR SAID VERIFICATION"

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TECHNICAL FIELD

This invention concerns a process and the relative device for the recognition of documents marked with OVI™ (Optical Variable Inks) through the use of polarised light.

More particularly, this invention refers to a device which uses polarised light for the recognition of banknotes.

BACKGROUND ART It is known that the problems relative to the fight against counterfeiting require constant updating of the methods used to distinguish original products or documents from copies .

As far as printed documents are concerned and banknotes in particular, the sector is constantly in search of new methods which ensure the originality of the documents, make them difficult to reproduce and capable of standing up to considerable wear and tear; as a discouragement to counterfeiters, these methods are usually expensive. In general the methods used in distinguishing such documents can be grouped together on the basis of their recognition and in particular as features for primary recognition, i.e. recognition which does not require the use of devices, and for secondary recognition in which particular systems are required.

Primary recognition is based on physical elements such as the consistency and type of support material and optical elements such as colours, inks and type of printing.

Some of the optical elements most commonly used to distinguish documents, and banknotes in particular, are the watermark, the metal security strip and sometimes holographic bands, in which the first two, can be clearly seen by holding the banknote against the light while by varying the inclination of the banknote the holographic bands show both an image and, for example, the value of the note.

Other methods for distinguishing banknotes use particular printing methods and special inks, reproducing for example particular printing patterns such as pyramids or extra-fine lines which would not be reproduced by normal photocopiers or scanners, while as far as special inks are concerned fluorescent metallic inks, easy to see under ultraviolet light, are often used. There are also magnetic inks, usually used to form the characters of the serial numbers of the notes and which can be read by a special detector.

With reference to this invention, the most recently issued banknotes use the so-called OVI™ (Optical Variable Inks), which because of their particularly high cost are used for small portions only on the higher denomination notes, such as for example the 50, 100, 200 and 500 Euro in the figures on one of the two sides of the banknote.

The OVI™ consist of miniscule platelets of special film positioned parallel to each other during printing, providing excellent optical properties and in particular a colour change according to the angle of observation.

More specifically these inks are produced with pigments that react to the different, degree of incidence of the light with different metallic colouring. This feature is due to the phenomena of interference, absorption and reflection of the visible light in multilayered pigmented systems . 5 The OVI™ comprise a combination of low-refraction transparent layers and high-reflection absorbent materials.

These pigments show a reflection of violet, gold, green or red shades depending on the angle of incidence of the light. This laminar arrangement of the pigments and its

10 thickness in the range of the wavelength of visible light creates interference phenomena with the colouring linked to the metallic material of the pigments .

The particular materials described above often allow not only the so-called primary recognition but also, thanks to

15 their special features, the use of systems and devices for secondary recognition.

The background art includes numerous examples of devices for authenticating documents and banknotes; for example the document EP-A-0748466 presents a device comprising scanning

20. means designed to detect the presence of particles with electromagnetic properties that are substantially different from those of the basic material and which are present in at least a part of the document to be analysed.

Another example relative to a device used for

25 recognising the authenticity of documents is described in WO-A-99/27502 and is based on a microwave system that can detect the difference between the microwaves emitted by the device on the document to be checked and those received from the document, thus verifying the authenticity.

30 The document WO-A-01/60924 describes pigments with optically variable luminescence, methods for obtaining them and their use as a security element in inks, coatings and articles. The document also describes a device comprising for example a UV lamp or a small device for photoelectric luminescence detection. Another authentication method is described in the document WO-A-02/01512 and refers to a system for the local or remote verification of a document, in which the document exhibits a characteristic physical reaction to a certain source of energy such as for example electromagnetic radiation and/or magnetic or electrical fields.

A viewer and a method for simultaneously ascertaining the optical features of colorimetric variation of a device with variable optical features is described in the patent US-A-5596402. This viewer exploits the essential chromatic variation features of OVI™ type inks with the variation in the angle of light incidence. In fact an image obtained with OVI™ type inks shows a significant change in colour when viewed from two different angles that differ for example by at least 40° and up to around 70°. The angle of reflection of a ray of light from the image is generally the same as the angle of incidence of the ray of light illuminating the image; this principle is in fact exploited in the device described in the patent US-A- 5596402. The methods described above require systems and features that are not easy to implement and which affect their production, the costs and consequently on the affordability of these products for the public.

DESCRIPTION OF THE INVENTION

The present invention aims to overcome the drawbacks present in the background art and to provide, therefore, a system for the recognition of documents, in particular of banknotes, which is secure, reliable, economic and easy to use. In particular, the present invention aims to provide a process for the recognition of documents marked with OVI™ type inks (Optical Variable Inks) through the use of polarised light.

This is achieved by implementing a process with the features described in the main claim.

The dependent claims describe advantageous embodiments of the process according to this invention.

According to another aspect, the present invention proposes to provide a device for the recognition of documents marked with OVI™ type inks.

This is achieved by means of a device with the features described in claims 5 to 10.

The process according to the invention comprises the following steps : - production of a ray of polarised light through the use of a first polarising filter on a source of white or monochromatic light; exposure of the part of the document or banknote marked with OVI™ type inks to the ray of polarised light; - additional filtering of the light reflected by the document or the banknote by means of a second polarising filter placed at an appropriate reciprocal angle with respect to the degree of polarisation of the incident light; - direct or automated detection of the variation in luminescence. According to a particularly advantageous form of embodiment of the invention, the second polarising filter is preferably placed in opposition with respect to the degree of polarisation of the incident light obtained from the first polarising filter.

This makes it possible to almost totally cancel the reflection and the surface of the analysed document treated with OVI™ inks will appear completely black.

Any substitute for these OVI™ reacts in a completely different way to the application of the polarised light according to this invention, maintaining a threshold of colour and luminosity, thus making it possible to recognise it by comparison.

In fact, the effect advantageously exploited by this invention refers to the particular physical phenomenon or reflection and refraction of the light, a feature of OVI™ when struck by a ray of polarised light.

The device for the recognition of documents marked with OVI™ type inks according to this invention comprises: - a source of light; a first polarising filter positioned between the light source and an element marked with OVI™ ink to be recognised; a second polarising filter, placed at an appropriate reciprocal angle with respect to the degree of polarisation of the incident light, designed to filter and repolarise the light reflected by the marked element and placed between this element and a subject or an automatic recognition system. The device according to this invention is particularly useful for recognising and checking the authenticity of documents marked with OVI™, in particular for banknotes, including the Euro, the Dollar, the British Pound and the Swiss Franc.

DESCRIPTION OF THE DRAWINGS

Other features and advantages of the invention will become evident on reading the following description of some forms of embodiment of the invention, given as non-binding examples, with the help of the enclosed drawings, in which: - figure 1 is a block diagram representing the recognition process and the basic components of a subjective analysis recognition device for OVI™ type inks according to the present invention; figure 2 is a block diagram representing the recognition process and the basic components of an automatic analysis recognition device for OVI™ type inks according to the present invention; figure 3 is a cross-section side view of a particular form of embodiment , of the device according to the present invention.

DESCRIPTION OF SOME FORMS OF EMBODIMENT

The process for recognising and determining the authenticity of documents marked with OVI™ according to the present invention comprises the following steps :

- production of a ray of polarised light through the use of a first polarising filter on a source of white or monochromatic light;

- exposure of the part of the document or banknote marked with OVI™ type inks to the ray of polarised light;

- additional filtering of the light reflected by the document or the banknote by means of a second polarising filter placed at an appropriate reciprocal angle with respect to the degree of polarisation of the incident light; - direct or automated detection of the variation in luminescence.

Figure 1 is a block diagram of a subjective analysis OVI™ recognition device to determine the authenticity of documents or banknotes according to the present invention.

In particular block "A" represents the observer receiving the rays of reflected light bipolarised (straight line arrow) and polarised only once (wavy line arrow) coming from the document or the banknote being checked and represented by block "D" .

The polarising optical unit is represented by block "C" which according to a particularly advantageous form of embodiment comprises a source of white or monochromatic artificial light polarised by a first polarising filter which illuminates the element "D".

The ray reflected by this element "D" is captured by a second polarising filter, placed at an appropriate reciprocal angle with respect to the first filter.

According to a particular form of embodiment, the block "B" can consist of an optical viewer equipped for example with a Fresnel lens which makes it possible to focus both the luminous ray bipolarised by the polarising optical unit "C" and the non-repolarised ray, both reflected by the document or banknote "D" .

According to this particular form of embodiment, the observer can make an immediate comparison between the surface portions with and without bipolarisation which, in the case of an original document, will appear substantially different and in particular the part reflecting the bipolarised light will appear completely black while the other part will maintain the usual changing colour look.

In a counterfeit document not marked with OVI™ type inks, all the analysed part will present the same optical features.

Figure 2 shows a block diagram of a particular embodiment of this invention relative to an automatic analysis OVI™ recognition device. As in the previous diagram, there is a polarising optical unit represented by the block "C" which, according to a particularly advantageous form of embodiment, comprises a source of white or monochromatic artificial light polarised by a first polarising filter which illuminates the element "D" . The ray reflected by this element "D" is captured by a second polarising filter, placed at an appropriate reciprocal angle with respect to the first filter.

The rays of reflected light bipolarised and polarised only once are represented respectively by a straight line arrow and by a wavy line arrow.

The blocks "El" and "E2" represent photoelectric cells in which "El" captures the bipolarised light and "E2" captures the reflected light polarised only once. According to an advantageous form of embodiment of the invention, the signal obtained by the two photoelectric units is sent to an analyser system represented by the block "F" which performs the comparison, sending the resulting information to an indicator represented by the block "G" . According to a particular form of embodiment, the analyser circuit "F" can be connected to a mechanism for the automatic infeed of documents or banknotes, represented by the block "H".

Figure 3 shows a particularly advantageous form of embodiment of a device for the recognition of documents marked with OVI™ and identified with the reference number 10.

This device 10 comprises a transformer 11 connected to a lamp 12 which emits a white or monochromatic light that is filtered through a first polarising unit 13. According to the present invention, the beam of polarised light emitted along the axis x strikes the OVI™ marked document or banknote which reflects the polarised light along the axis z. According to a particularly advantageous form of embodiment of the invention, the beam of reflected light is divided in two and one of the two luminous beams is filtered by a second polarising unit 14; these two beams of reflected light pass through a magnifying lens 15 so that the image on the upper display 16 is enlarged. The result obtained consists of an image of the part printed with OVI™ divided in two, one part of which, the one whose reflected light was filtered by the second polarising unit, is black or opaque while the other maintains its real colours. On the contrary, a counterfeit document, therefore not marked with OVI™, will present a homogeneous and completely coloured image when analysed with the device according to the invention and described in the previous example.

The invention is described above with reference to preferred forms of embodiment.

It is nevertheless clear that the invention is susceptible to variations which are within the framework of technical equivalents .

Claims

1. Process for the recognition of elements marked with OVI™ (Optical Variable Ink) type ink characterised by the following steps: - production of a ray of polarised light by the use of a first polarising filter on a source of light; exposure of the part of the document or banknote marked with OVI™ type inks to the ray of polarised light; - additional filtering of the light reflected by the document or the banknote by means of a second polarising filter placed at an appropriate reciprocal angle with respect to the degree of polarisation of the incident light; - detection of the variation in luminescence.

2. Process according to claim 1 characterised in that a white or monochromatic light is used.

3. Process according to claim 1 characterised in that the authenticity of the document marked with OVI™ is detected by means of a comparison between a ray of bipolarised light and ray of light polarised only once or not polarised.

4. Process according to any one of the claims from 1 to 3 characterised in that the luminescence detection takes place automatically.

5. Device for the recognition of elements marked with OVI™ (Optically Variable Inks) characterised in that it comprises: a source of light; - a first polarising filter positioned between the light source and an element marked with OVI™ ink to be recognised; a second polarising filter, placed at an appropriate reciprocal angle with respect to the degree of polarisation of the incident light, designed to filter and repolarise_. the light reflected by the marked element to be recognised.

6. Device according to claim 5 characterised in that the source of light consists of an incandescent lamp.

7. Device according to any one of the claims from 5 to 6 characterised in that it is connected to an automatic recognition system.

8. Device according to claims 5 to 7 characterised in that the automatic recognition system comprises at least one photoelectric cell.

9. Device according to any one of the claims from 5 to 8 characterised in that the second polarising filter is placed in opposition with respect to the degree of polarisation of the incident light.

10. The use of a device according to any one of the claims from 5 to 9 for the recognition of banknotes, documents and in the anti-counterfeiting sector in general.