DE102007008151A1 - Safety feature for authenticity of documents, has alphanumeric characters that are represented by one of its optically distinguished from that corresponding to local change of dielectric constants of document - Google Patents

Abstract

The safety feature has alphanumeric characters that are represented by one of its optically distinguished from that corresponding to a local change of the dielectric constants of the document. The safety feature has electrically conductive material that is aluminum, copper, chrome, Iron or gold or alloy. A substrate is provided that is made form paper, plastic or a combination of these materials. A dielectric carrier (8) is provide that is a polymer foil, copolymer foil or a laminate of polymer foils or copolymer foils. The foil material is polypropylene, polyethylene or polycarbonate. An independent claim is also included for a method for examining an authenticity of documents.

Description

The The invention relates to a security feature for the Authenticity of a document, that in the authenticity check the document is machine readable and at least one alphanumeric Signs, and a method for checking the authenticity a document provided with the security feature.

It is well known documents that serve as evidence of material or intangible assets, access rights or identifications serve to provide a security feature whose imitation or falsification is as difficult as possible.

Examples of such documents include banknotes, checks, credit cards, access badges, passports and the like. One well-known example of such a security feature is the metal thread or strip present in many banknotes which is embedded in the banknote paper and thus can not easily be imitated , A more advanced possibility is to provide the banknote with a transponder chip ( WO 00/07151 ), in which an authenticity information is stored, which is read without contact for authenticity checking. Here, the security against counterfeiting is very high because counterfeiters are the complicated and expensive facilities that are required for chip manufacture and embedding in the banknote paper, are not available. However, the use of chips as a security feature has the problem that the chips can be destroyed, for example by microwave irradiation, and then the problem arises, as can be done with the presentation of such a corrupted document, such as a bill or passport. In addition, the costs of this measure still play a role in equipping the documents with the transponder chips, despite sinking chip travel.

Of the Invention is based on the object, a cost, resistant and highly tamper-proof Security feature for creating documents and a procedure to verify the authenticity of these security features provided documents.

to Solution to this problem becomes a safety feature of the beginning mentioned type designed to the effect that the alphanumeric Character corresponding to one of its visually perceptible shape local change of the dielectric constant of the document.

The Use of at least one, but usually a plurality alphanumeric character meets the common practice the documents to be backed up with alphanumeric information to provide. So usually carries every bill an individual number and / or letter sequence. Further examples are the passport number in passports and the driver's license number in driver's licenses. The appearance of the visually perceptible Form of the alphanumeric character (s) by one of these forms corresponding local change of the dielectric constant The document requires manufacturing methods that are for counterfeiters are not available. In particular, suitable for this purpose the mask techniques known from chip production. So that can the illustration also done on a very small scale. For example, the character size per character less than 1 mm. Even such small representations can with the resolution today available capacitive reader, as for example as Fingerprint readers are well known, are well read.

The local changes detectable by the machine read the dielectric constant can in particular be caused by variation of electrical parameters. For example, can these are induced or permanent changes electric polarization or non-linear field dependent Act polarization changes. Another possibility consists in the variation of shape parameters, such as thickness changes or surface profiles. The changes of the shape parameters For example, by printing with a suitable thickness order be caused. The capacitively readable representation of or Alphanumeric characters can also be visually perceptible Form corresponding local shielding of a permanent polarization obtained become. Another possibility is in one of the optical perceptible shape corresponding to local doping of a substrate, z. B. with metal ions.

generally known is the dielectric constant, which is also called permittivity is called, as a proportionality factor between electrical Displacement and electric field strength defined. Your Size generally depends on the frequency of the applied electric field. In the simplest case will be the machine reading with a capacitive reader, through which a temporally constant electric field is applied, ie the dielectric constant or permittivity is determined at a frequency of 0 Hz. Within the scope of the invention can be the local change of the dielectric constant However, also be realized so that they only in one certain frequency range or specific frequency ranges and the machine reading in this frequency range or this Frequency ranges is performed.

These Capacitive readers form the through the local change represented by the dielectric constant of the document Form of the alphanumeric character over a large Number of individually controllable sensor elements as rasterized bitmap (bitmap) from. The pixel size of this grid can be in the range of 50 microns and below. The sensor elements can be arranged in a row. This is along a Scan direction over the alphanumeric character (s) led away, thereby causing a sequential, line by line Scanning. Alternatively, the capacitive sensor elements in matrix form in one for simultaneous detection of the or alphanumeric characters appropriate field size be arranged. Then there is no relative movement for the scan between the reader and the one or more alphanumeric characters Document required.

in the Difference to the realization of the security feature by a electronic chip is the capacitive recording of the or the alphanumeric characters very durable and practically indestructible, as long as the document is not destroyed altogether.

A expedient embodiment is that the at least one alphanumeric character by a its visually perceptible shape appropriately shaped island a formed on a dielectric support, electrically conductive Material is shown. Through this island or islands are the or the alphanumeric characters in positive form. alternative but it may also be appropriate that the at least one alphanumeric character through one of its optical perceptible shape appropriately shaped recess in one a dielectric carrier formed, electrically conductive Material is shown. In this case, the one or more alphanumeric Character through the recess or the recesses in negative form shown. In both cases, the electrically conductive Material, in particular a metal layer or an electrically conductive Be plastic layer. In all cases, this can be electrical conductive material on the dielectric support have a grid structure. The dielectric carrier is preferably a polymer film, copolymer film or a laminate of polymer films or copolymer films. In particular, it can be in the film material to polypropylene, polyethylene or Polycarbonate act. As electrically conductive material For example, aluminum, copper or gold may be considered.

in the Frame of the invention can also be provided that a the at least one alphanumeric character representing electrical conductive material bearing surface opposite surface of the dielectric carrier with an electrically conductive Cover layer is provided. As the thickness of the dielectric support is preferably very small, in particular less than 100 microns and preferably in the range of 5 to 20 μm the distance between the alphanumeric character or the alphanumeric Character representing electrically conductive material and the on the other side of the dielectric support provided electrically conductive cover layer so small that the capacitive patterns against the background formed by the cover layer by radiation in the visible or shorter wavelength range, For example, X-rays, not recognized and therefore can not be copied in this way.

A especially with regard to the production of appropriate Embodiment is that the document a dielectric substrate having the representation of the at least one alphanumeric character bearing dielectric carrier is provided. This can be the alphanumeric character or the dielectric characters carrying the alphanumeric characters, whose production is particularly demanding, manufactured separately and then with the simpler in comparison Substrate of the document are connected. With regard to a protected Attaching the dielectric support, the representation the one or more alphanumeric characters is advantageous, that this dielectric carrier in the substrate is embedded. The substrates are in particular paper, plastic or a combination of these materials. The embedding of the dielectric support can in this case in the pulp in papermaking or as an intermediate between at least two composite layers of these materials. For example, can the dielectric carrier similar to the ordinary one Metal security thread of banknotes be strip-shaped and similar to the latter embedded in the paper.

One to solve the problem mentioned above suitable method to verify the authenticity of a document that is a security feature has characterized according to the invention characterized from that the at least one alphanumeric character representing local change of the electric capacity read with a capacitive reader.

Each of the capacitive sensing elements of the capacitive reader provides an output signal corresponding to the capacitance detected by the sensor. From the totality of these output signals, therefore, it is possible to obtain a read signal which corresponds to a bitmap image of the one or more alphanumeric characters detected by the sensor elements. From the read signal can therefore be obtained directly a representation of the visually perceptible shape and, for example, on a view display unit are displayed. Alternatively or additionally, from this read signal with a character recognition software, the identity of the character (s) can be determined and a code identifying the character can be generated. This identification is well known in the field of optical character recognition, often abbreviated as OCR (Optical Character Recognition), and may also be used for the present capacitive method. It is based on an evaluation of the bitmap provided by the sensor elements, for example by comparison with the stored character set stored stored dot patterns or by evaluation by means of suitable detection algorithms. The authenticity check of the document is only considered to have passed if the reading result corresponds to predetermined criteria, for example, reproduces a predetermined alphanumeric character string.

Especially can be provided that the at least one alphanumeric Sign on the document also recorded in optically readable form is and the optically readable form with the read signal of the capacitive reader's information is compared. Naturally can thereby the won by the read signal of the capacitive reader Information be more extensive, d. H. a bigger one Number of alphanumeric characters included as the optically readable Recording. In this case, the comparison is limited on the optically readable record corresponding part of capacitively read information.

below the invention will be exemplified with reference to the drawings explained. Show it:

1 Examples of the representation of alphanumeric characters by an arranged in grid structure, electrically conductive material, and

2 a schematic representation of the capacitive detection.

In 1 is on a lying in the plane of the drawing surface of a dielectric support, not shown, the visually perceptible shape of the letters "E", "G" and "F" recognizable. Each of these three letters is in a block 1 . 2 . 3 of every n pixels 4 , where n is 10 in the example shown. In the blocks 1 and 3 representing the letters "E" and "F" are the block boundaries left and right of each represented letter, each by a vertical row of ten pixels each 4 marked. On the other hand, in the block representing the letter "G" 2 no marking of the block boundary provided. It is understood that the illustrated letters "E", "G" and "F" are only examples and in this way all alphanumeric characters, including digits, can be displayed. Also, the illustration is not on the in 1 shown font, but includes all possible fonts.

The pixels 4 in 1 thus form a positive representation of the alphanumeric characters, in which forms their optically perceivable shape islands on the dielectric support. The representation could also take place in negative form, in which the alphanumeric characters form recesses in the electrically conductive material covering the dielectric carrier.

The individual pixels 4 are square with an edge length in the range of a few hundred micrometers and smaller, for example, 200 microns, 100 microns and 50 microns. The grid spacing between immediately adjacent pixels 4 is significantly smaller than the edge length and is for example 10% of this edge length. The pixels 4 consist of an electrically conductive material, such as copper, which has been applied by masking to the surface of the dielectric support.

2 schematically illustrates the interaction between the alphanumeric-marked dielectric carrier and a capacitive reader. The representation consists of three sections, of which the lowest section 5 symbolizes the area of the reader in which its sensor elements are arranged. The illustration shows the special case that the sensor elements along a single line 6 are arranged. An arrow 7 illustrates one to the direction of the line 6 orthogonal scanning direction along which a dielectric carrier provided with the alphanumeric string "ABC 123" 8th from a transport device provided in the reader across the line 6 is transported away. The dielectric carrier carrying the alphanumeric string 8th is normally part of a larger dielectric substrate that forms a document that is in 2 but not shown. When the document is a banknote or badge, the substrate is usually paper and the dielectric carrier 8th preferably embedded in this paper. In the case of money, bank or access cards, the substrate is usually made of plastic and is preferably composed of two layers, between which the dielectric support 8th is included.

The one at the bottom section 5 adjacent middle section 9 of the schema of 2 symbolizes the bit pattern (bitmap) that occurs when scanning the on the dielectric carrier 8th Capacitive recorded alphanumeric string "ABC 123" through the sensor element line 6 arises. This bit pattern represents a direct pixel image of the optically discernible form of the alphanumeric string. The one in the middle section 9 reproduced pixel image represents a snapshot of the case that the letter "A" almost completely over the sensor element line 6 has been transported away.

In In the example shown, the pixel image corresponding Bit pattern processed with a character recognition software. These recognizes for example by comparison with stored bit patterns an entire character set the identity of the scanned alphanumeric characters and specifies the recognized characters Identification codes. The latter are then checked whether they fulfill a given safety criterion. In particular, these identification codes can also be found in an optical display appearing on a display unit The alphanumeric string can be converted to the user the reader's read the string directly to viewing to make accessible. If the alphanumeric string is also recorded in optically readable form on the document, the viewer can immediately find out if there is a match exists with the capacitive recording or whether deviations exist are.

If the reader for an automatic run of documents, For example, the bills is designed, provided an ejector which documents, whose capacitive reading result is the safety criterion not fulfilled, isolated.

1, 2, 3

blocks

4

pixel

5

unterster section

6

row of sensor elements

7

scan

8th

dielectric carrier

9

middle section

10

upper section

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• WO 00/07151 [0003]

Claims (24)

A security feature for the authenticity of a document which is machine readable in the authentication of the document and which has at least one alphanumeric character, characterized in that the alphanumeric character ( 1 . 2 . 3 ) is represented by a local change in the dielectric constant of the document corresponding to its optically perceivable shape. Security feature according to claim 1, characterized that the local change in the dielectric constant on one of the visually perceptible form of the at least one alphanumeric Sign corresponding local thickness change of the document based. Security feature according to claim 1, characterized that the local change in the dielectric constant on one of the visually perceptible form of the at least one alphanumeric Sign corresponding local electrical polarization change based. Security feature according to claim 1, characterized that the local change in the dielectric constant on one of the visually perceptible form of the at least one alphanumeric Sign corresponding local change in material composition based. Security feature according to claim 1, characterized in that the at least one alphanumeric character ( 1 . 2 . 3 ) is formed by a correspondingly shaped island of one on a dielectric support ( 8th ) formed, electrically conductive material is shown. Security feature according to claim 1, characterized in that the at least one alphanumeric character ( 1 . 2 . 3 ) by a correspondingly shaped recess in its on a dielectric support ( 8th ) formed, electrically conductive material is shown. Security feature according to one of the claims 5 or 6, characterized in that the electrically conductive Material has a grid structure. Security feature according to one of Claims 5 to 7, characterized in that one of the surfaces carrying the electrically conductive material bearing the at least one alphanumeric character has the surface of the dielectric support ( 8th ) is provided with an electrically conductive cover layer. Security feature according to one of the claims 5 to 8, characterized in that the electrically conductive Material aluminum, copper, chrome, iron or gold or one of a is alloy containing these elements. Security feature according to one of Claims 5 to 8, characterized in that the document comprises a dielectric substrate which is in line with the dielectric support which carries the representation of the at least one alphanumeric character ( 8th ) is provided. A security feature according to claim 10, characterized in that the dielectric support carrying the representation of the at least one alphanumeric character ( 8th ) is embedded in the substrate. Security feature according to claim 10 or 11, characterized characterized in that the substrate is made of paper, plastic or a combination of these materials. Security feature according to one of Claims 5 to 12, characterized in that the thickness of the dielectric support ( 8th ) in the range of 100 microns and smaller, preferably in the range of 5 to 20 microns, is located. Security feature according to one of Claims 5 to 13, characterized in that the dielectric support ( 8th ) is a polymer film, copolymer film or a laminate of polymer films or copolymer films. Security feature according to claim 14, characterized that the film material polypropylene, polyethylene or polycarbonate is. Security feature according to one of Claims 5 to 15, characterized in that the dielectric support ( 8th ) the at least one alphanumeric character ( 1 . 2 . 3 ) bearing surface is connected to a first dielectric cover layer. Security feature according to one of Claims 5 to 16, characterized in that the dielectric support ( 8th ) at which the at least one alphanumeric character ( 1 . 2 . 3 ) bearing surface opposite surface is connected to a second dielectric cover layer. Security feature according to claim 16 or 17, characterized characterized in that at least one of the cover layers is optically is opaque. Security feature according to Ansprü che 16 to 18, characterized in that on one of the cover layers, the at least one alphanumeric character is recorded in optically readable form. Security feature according to one of the claims 1 to 19, characterized in that the at least one alphanumeric characters on the document also in optically readable Form is recorded. Procedure for checking the authenticity of a A document that is a security feature according to any one of the claims 1 to 20, characterized in that the local change representing at least one alphanumeric character the electrical capacity with a capacitive reader is read. Method according to claim 21, characterized that from the read signal of the capacitive reader a representation the visually perceptible shape of the character is obtained. Method according to claim 21 or 22, characterized that from the read signal of the reader with a character recognition software the identity of the sign is determined. Method according to one of claims 21 to 23, in which the at least one alphanumeric character also in optical readable form is recorded, characterized in that the optically readable form with the by the read signal of the capacitive reader obtained information is compared.