DE102009059054A1 - Method for generating signature for e.g. banknote, involves scanning area of surface of article, receiving scanning signal, generating signature from received scanning signal, and storing signature in form for subsequent comparison purposes - Google Patents

Abstract

The method involves scanning a region (7) of a surface (1) of an article using a line-shaped beam profile (6) of a radiation source e.g. LED. A scanning signal representing a part of the surface structure within the region is received. A signature is generated from the received scanning signal. The signature is linked with the article. The signature is stored in a preset form in an electronic storage medium i.e. semiconductor memory, optical storage medium i.e. compact disk, a magnetic storage medium i.e. hard disk, or radio frequency identification chip, for subsequent comparison purposes. Independent claims are also included for the following: (1) a method for identifying and/or authenticating articles (2) a sensor for scanning a surface of articles.

Description

The subject matter of the present invention is a method for identifying and / or authenticating objects based on their surface condition. The subject of the present invention is also a sensor for scanning a surface.

The surface quality of objects plays an important role in many technical products and processes, for example in mold making and in technical sliding or visible surfaces. For paper, the surface structure is an important quality feature z. B. in connection with the printability.

Accordingly, there are a variety of measurement methods for determining the surface structure and for determining characteristic characteristics for the surface condition. Measurement methods, the result of which is the topography of the surface, are also referred to as direct methods. The indirect methods provide characteristic indicators such. For roughness, without measuring the actual shape of the surface itself. An example of an indirect method is the Bekk method of determining the roughness of a paper or board specimen by measuring an airflow passing between a shutter and the sample surface.

In the direct methods tactile and optical methods can be distinguished. With tactile methods, surfaces are scanned point by point with mechanical probes. The probe deflection is measured electronically or opto-electronically. The result is a height signal recorded over the probe path, the so-called surface profile. By scanning closely adjacent surface profiles one obtains the surface scanning of the topography. Similar methods that operate without contact are scanning electron microscopy or atomic force microscopy (in the so-called non-contact mode).

An example of an optical method for topography determination is dynamic laser focusing (see, for example, US Pat Wochenblatt für Papierfabrikation, ISSN0043-7131, Volume 117, April 1989, No. 7; Pages 271 to 274 ). In the case of dynamic laser focusing, a laser is focused onto the surface by means of a lens. The lens can be moved by means of a servomotor perpendicular to the surface (in the z-direction). A sensor detects the respective z-position of the lens in a focused position and thus provides the topography information while the sample is moved horizontally through an xy-table under the lens.

Furthermore, topographic information of a surface can also be obtained, for example, with an acoustic or a chromatic near field sensor, with an eddy current sensor or a phase white light interferometer.

From the determined topographies, key figures can be determined such as, for example, the average roughness value R _a or the roughness depth R _z (see DIN EN ISO 4287: 1998 ). The parameters mentioned are defined on a single measuring section and are generally calculated as mean values from several individual measuring sections. For roughness parameters, five individual measuring sections are standard ( DIN EN ISO 4288: 1998 ).

It is therefore customary to compress the amounts of data recorded on surface topography by direct methods to a few key figures. The compression of the data sets to a few key figures allows a classification of objects. However, compressing the data volumes to a few key figures destroys the individuality of the individual object, because the key figures only allow to deduce material classes, but not individual objects.

However, capturing and recognizing objects, for example, plays an important role in product tracking and counterfeiting.

The automated detection of objects based on z. B. Barcodes is well known in this context. Barcodes (barcodes) are applied to goods and / or packaging and allow a machine identification of the goods to determine z. B. the price. However, they do not provide protection against counterfeiting, as they are easy to copy and transfer to other objects.

Badges, banknotes, products, etc. are now provided with counterfeit protection elements that can only be imitated with special knowledge and / or high technical effort. Such elements are referred to herein as security elements. The authenticity of an object can be verified by the presence of one or more security elements.

Optical security elements such. Watermarks, specialty inks, guilloche patterns, micro-typefaces and holograms are well established worldwide. An overview of optical security elements, which are particularly suitable but not exclusively for document protection, is the following book: Rudolf L. van Renesse, Optical Document Security, Third Edition, Artech House Boston / London, 2005 (pp. 63-259) ,

However, much of today's commercially available security elements do not allow individualization, ie many objects carry the same security element. The objects bearing the same security element can not be distinguished by the security element.

Often, however, it is desired to be able to unambiguously and reliably identify a single object from a multiplicity of comparable objects. This in PCT / EP / 2009/002809 described security element allows for individualization of individual objects and thus the secure and unambiguous identification. However, it would be advantageous to be able to identify and / or authenticate an object without aids such as security elements.

Also known in the art are methods of identification and authentication that do not use features other than those provided by the object itself.

In WO2005 / 088533 (A1) For example, a method is described that allows objects to be identified and authenticated using coherent radiation. In the method, coherent radiation is focused on the surface of the article and the surface is scanned. Photodetectors detect the radiation reflected by the surface. The detected reflected radiation represents a characteristic reflection pattern that is unique to a variety of different materials and is difficult to imitate because of the randomness of manufacturing and / or processing of the article. The characteristic reflection patterns of individual objects are stored in a database in order to be able to identify and / or authenticate each object at a later time. For this purpose, an object is measured again and the characteristic reflection pattern compared with stored reference data.

In WO2005 / 088533 (A1) it is stated that the detected reflection pattern is a mixture of speckle pattern and scattered radiation. A disadvantage of the in WO2005 / 088533 (A1) described method is that coherent radiation must be used. It is known to those skilled in the art that sources of coherent radiation are significantly more expensive than non-coherent sources of radiation.

Furthermore, this is in WO2005 / 088533 (A1) described method limited to objects that are not damaged by irradiation and reflect a sufficient portion of the irradiated radiation again. Photosensitive articles or articles with a high electromagnetic radiation absorptivity can not be detected and later clearly detected.

On the basis of the prior art described, the task thus arises of providing a method with which a multiplicity of different objects can be identified and / or authenticated. The sought process should allow the distinction of similar objects. In this case, the process sought to get along without expensive tools, such as individualized holograms or the like, based on which an individualization of similar objects according to the prior art. The process sought should be cost-effective, intuitive and easy to implement, flexible in use and extensible, deliver reproducible and transferable results, and be ready for mass production.

Surprisingly, it has been found that objects can be identified and authenticated on the basis of their surface condition. The surface of objects has individual characteristics which are characteristic of the respective object. These features allow the distinction of similar objects.

Under similar objects such objects are understood that are apparently the same, but not identical, such. As the individual sheets of a pile of paper or individual components from a mass production.

The individual surface finish is surprisingly not limited to types of objects or materials, but applies in principle to all objects. Surprisingly, even with polished mirrors, where one would speak of a smooth surface without any appreciable surface structure, one can at the atomic level make up an individual surface finish.

Surprisingly, it has been found that the surface texture of many objects is so robust that it is largely unchanged even after a relatively long time, so that it can be used to identify and / or authenticate the respective article. Since the surface texture can be determined by a variety of different measurement methods, different types of objects can be safely identified and / or authenticated. Should an object be sensitive to light, the determination of the surface condition could be carried out by a tactile method. If an item is sensitive to pressure, the Determination of the surface condition contactless z. B. by means of an optical process.

An object is understood to mean any solid body. The surface of the body separates it from the surrounding medium (mostly air).

Surface texture is the three-dimensional structure of the surface of an object (topography). The terms surface texture and topography are used synonymously here. A surface profile is the profile that results from the (imaginary) intersection of a surface of an object with a given plane (see, for example, FIG. DIN EN ISO 4287: 1998 , Picture 2). Topography and surface profile are collectively referred to as surface structure.

Identification is understood to mean a process that serves to uniquely recognize an object.

Authentication is the process of verifying (verifying) an alleged identity. The authentication of objects is the statement that they are authentic - that is, they are unchanged, not copied and / or not faked originals.

Method for generating a signature of an object

A first subject of the present invention is a method for generating a signature of an article.

• A1: Abtastung eines ersten Bereichs einer Oberfläche des Gegenstandes und Aufnahme eines Abtastsignals, das zumindest einen Teil der Oberflächenstruktur innerhalb dieses ersten Bereichs repräsentiert,
• A2: Generierung einer Signatur aus dem in Schritt A1 ermittelten Abtastsignal,
• A3: Verknüpfung der Signatur mit dem Gegenstand,
• A4: Speicherung der Signatur in einer Form, in der sie für spätere Vergleichszwecke verfügbar ist.

The inventive method for generating a signature of an article comprises at least the following steps.

• A1: scanning a first area of a surface of the object and picking up a scanning signal representing at least a part of the surface structure within this first area,
• A2: generation of a signature from the scanning signal determined in step A1,
• A3: linking the signature with the object,
• A4: storage of the signature in a form in which it is available for later comparison purposes.

The signature is a storable information about an object. It contains information about characteristic features of the object. The characteristic features result from the unique surface texture of the respective object.

The scanning of a first area of a surface of an object according to step A1 can be performed by any method with which a surface structure of an object can be determined, e.g. B. with a tactile or optical method. There are already commercial devices on the market that can be used. Preferably, methods are used which detect a surface structure without contact. Particular preference is given to using optical methods.

The result of the scan is a scan signal representing the surface texture within the first region.

The scanning can be done along a line. In this case, a surface profile can be derived from the scanning signal. Likewise, it is conceivable to make a scan meander-shaped or along several lines, preferably parallel to one another. The parallel lines are preferably so close to each other that can derive from the scanning signals a surface topography. This is exemplary in the . and shown in the following publication: Wochenblatt für Papierfabrikation, ISSN0043-7131, Volume 117, April 1989, No. 7; Pages 271 to 274 , Every single surface profile that results from scanning along a single line is unique in itself. However, adjacent surface profiles have similarities. Thus, there are continuous transitions from a surface profile to an adjacent surface profile. The individual lines along which a scan takes place should therefore be so close together that such a continuous transition is recognizable. This makes it possible to interpolate the areas between adjacent surface profiles and thus to approximate the entire topography from the individual scanned line areas.

• I. Es ist möglich, die Oberflächenstruktur durch punktweises Abtasten der Oberfläche mit einem mechanischen Taster zu ermitteln. Denkbar ist, dass der Taster auf die Oberfläche zubewegt wird, bis er diese berührt. In dem Punkt, wo der Taster die Oberfläche berührt, tritt ein Widerstand auf. Es müsste eine erhöhte Kraft angewendet werden, um den Taster in die vorher eingeschlagene Richtung weiterzubewegen (die Oberfläche steht dem Taster im Weg). Diese Weglänge bis zum Auftreten des Widerstands wird registriert und der Taster wird in seine Ausgangsposition zurückbewegt. Im nächsten Schritt wird der Taster oder der Gegenstand ein Stück zur Seite bewegt (senkrecht zur Richtung, in die der Taster auf den Gegenstand zubewegt wurde) und der Taster wird erneut auf die Oberfläche zubewegt. Auf diese Weise wird Punkt für Punkt die Weglänge ermittelt, bis jeweils ein Widerstand auftritt. Das Abtastsignal umfasst in diesem Fall Werte für die Weglänge als Funktion des Ortes. Hieraus lässt sich in einfacher Weise eine Oberflächenstruktur (Oberflächenprofil oder Topographie) ableiten.
• II. Es ist auch möglich, die Oberfläche mit Hilfe eines fokussierten Laserstrahls abzutasten. Der Laserstrahl wird mittels einer Linse auf die Oberfläche fokussiert. Die Linse kann mittels eines Stellmotors senkrecht zur Oberfläche (in z-Richtung) bewegt werden. Ein Sensor ermittelt die jeweilige z-Position der Linse in fokussierter Stellung und liefert somit die Topographieinformation während die Probe durch einen xy-Tisch unter der Linse bewegt wird. Üblicherweise ist der Sensor getaktet, d. h. er nimmt mit einer konstanten Frequenz Messsignale auf. Das Abtastsignal umfasst in diesem Fall die z-Position der Linse als Funktion der Zeit (Messfrequenz). Führt der xy-Tisch eine gleichförmige Bewegung mit einer konstanten Geschwindigkeit aus, so legt er in der Zeit zwischen der Aufnahme von zwei Messwerten immer denselben Weg zurück. Es liegt also eine bekannte Korrelation zwischen der Zeit und dem Ort vor, so dass sich auch hier aus dem Abtastsignal in einer einfacher Weise die Topographie der Oberfläche ermitteln lässt. Erfolgt die Aufnahme von Messwerten taktweise mit einer gleichbleibenden Frequenz und wird eine Bewegung zwischen Abtastvorrichtung und Gegenstand vorgenommen, die nicht gleichförmig ist, so kann auch ein mechanischer Kodierer (Encoder) verwendet werden, mit dem die Zeitinformation in eine Ortsinformation transformiert werden kann. Solche Encoder sind insbesondere bei optischen Messmethoden hinreichend bekannt. Auch das in WO2005/088533(A1) beschriebene Verfahren setzt einen Encoder zur Korrelation der Zeit- mit der Ortsinformation ein (siehe dort).

The sampling signal recorded during sampling depends on the measurement method used. This will be explained with two examples.

• I. It is possible to determine the surface structure by scanning the surface point by point with a mechanical probe. It is conceivable that the button is moved to the surface until it touches them. At the point where the button touches the surface, a resistance occurs. An increased force would have to be applied to move the button in the previously chosen direction (the surface is in the way of the button). This path length until the resistance occurs is registered and the button is moved back to its original position. In the next step, the button or the Move the object sideways (perpendicular to the direction the button was moved towards the object) and the button will move to the surface again. In this way, the path length is determined point by point until a resistance occurs in each case. The sample signal in this case includes values for the path length as a function of the location. From this, a surface structure (surface profile or topography) can be derived in a simple manner.
• II. It is also possible to scan the surface by means of a focused laser beam. The laser beam is focused on the surface by means of a lens. The lens can be moved by means of a servomotor perpendicular to the surface (in the z-direction). A sensor detects the respective z-position of the lens in a focused position and thus provides the topography information while the sample is moved through an xy-table under the lens. The sensor is usually clocked, ie it picks up measurement signals at a constant frequency. The scanning signal in this case comprises the z position of the lens as a function of time (measuring frequency). If the xy table performs a uniform motion at a constant speed, it will always travel the same way between taking two readings. Thus, there is a known correlation between the time and the location, so that the topography of the surface can also be determined here from the scanning signal in a simple manner. If the recording of measured values takes place cyclically with a constant frequency and if a movement between scanning device and object is made which is not uniform, then a mechanical encoder (encoder) can also be used, with which the time information can be transformed into a location information. Such encoders are well known, in particular in optical measurement methods. Also in WO2005 / 088533 (A1) described method uses an encoder to correlate the time with the location information (see there).

In step A2 of the method according to the invention, a signature is created from the scanning signal. The signature is used according to the invention to identify the object at a later time and / or to authenticate. For each item to be identified and / or authenticated at a later time, a signature must first be created. This process, in which the signature of an item is first determined, is also referred to herein as initial capture or registration. If the signature of an item is present, it can be saved. At a later date, when the item is recaptured, d. H. its signature is determined again, the stored signature can be used as a reference for comparison purposes.

The signature is thus a storable and machine processable information that can be obtained from the scanning signal and used for the purpose of identification and / or authentication. The term "storable" is understood to mean that the signature can be picked up again at a later time, for example for comparison purposes. Machine processing is understood to mean that the signature can be machine read and subjected to various computational and / or memory operations with a machine.

The signature contains information about features that uniquely identify an item. The signature may be the scanning signal itself. The signature may also be a surface topography derived from the scanning signal, ie, a collection of height information of a surface area as a function of the respective surface locations. It is also conceivable for a signature to have a surface profile as defined DIN EN ISO 4287: 1998 is.

As a rule, the signature is generated from the scanning signal by various mathematical methods such as filtering and / or background subtraction. These mathematical methods eliminate as far as possible random or systematic fluctuations resulting from individual measurements. For paper-like objects z. B. a ripple in a surface profile occur, which has arisen due to use of the object. This can be annoying in an identification and / or authentication, since it emerged only in the course of time and thus is not included in the original signature. Such a ripple can be eliminated (eliminated) by suitable filters from the sampling signal (see eg DIN EN ISO 4287: 1998 ).

It is also conceivable to mathematically transform the sample signal or a filtered sample signal to generate a data set that is better suited for identification and / or authentication purposes than the sample signal or a filtered sample signal itself. As an example of such a transformation Let us call a Fourier transformation which generates a location-independent representation of the scanning signal.

Furthermore, it is conceivable to extract characteristic patterns from the scanning signal and to use these extracted data as a signature (data reduction).

In step A3 of the method according to the invention for generating a signature, the Signature linked to the item. This linkage can be physical or virtual. In the case of a physical link, the signature can be printed on the object or scratched into the object, for example in the form of an optical code (barcode, matrix code, OCR text or the like). Likewise, it is conceivable to associate the object with a sticker which contains the signature stored. The attachment of an electronic data carrier such as an RFID chip, on which the signature is stored, to the object is also conceivable.

In the case of a virtual link, for example, a unique number assigned to the respective object (ID number, batch number or the like) is linked to the signature in a database. For example, the signature may contain this number in a header (metadata at the beginning of a file). The link ensures that there is a clear and unambiguous association between the signature and the object. The signature clearly indicates the associated item.

In step A4 of the method according to the invention, the signature is stored in a form in which it is available for later comparison purposes.

The storage can take place, for example, on an electronic storage medium (semiconductor memory), an optical storage medium (eg compact disk), a magnetic storage medium (eg hard disk) or another medium for storing information. It is also conceivable to store the signature as an optical code (barcode, matrix code) on a paper or the object itself or as a hologram.

After the signature has been generated and stored for the first time, the respective object is registered and can be identified and / or authenticated at a later time on the basis of its signature. The stored signature is also referred to here as a reference signature.

Method for identifying and / or authenticating an item

• B1: Abtastung eines zweiten Bereichs einer Oberfläche des Gegenstandes und Aufnahme eines Abtastsignals, das zumindest einen Teil der Oberflächenstruktur innerhalb dieses zweiten Bereichs repräsentiert,
• B2: Generierung einer Signatur aus dem in Schritt B1 ermittelten Abtastsignal,
• B3: Vergleich der im Schritt B2 ermittelten Signatur mit mindestens einer Referenzsignatur,
• B4: Generierung einer Mitteilung über die Identität und/oder Authentizität des Gegenstands in Abhängigkeit des Ergebnisses des Vergleichs in Schritt B3.

A second subject of the present invention is a method for identifying and / or authenticating an article, at least comprising the following steps:

• B1: scanning a second area of a surface of the object and picking up a scanning signal representing at least a part of the surface structure within this second area,
• B2: generation of a signature from the sampling signal determined in step B1,
• B3: comparison of the signature determined in step B2 with at least one reference signature,
• B4: generation of a notification of the identity and / or authenticity of the object depending on the result of the comparison in step B3.

The method according to the invention for identifying and / or authenticating an object is temporally downstream of the inventive method for generating a signature.

For steps B1 and B2, the steps described at steps A1 and A2 respectively, d. H. These steps are largely done in the same way.

In step A1, however, a first area is called a surface while in step B1 a second area of a surface is called.

In order for subsequent identification and / or authentication to be possible at all, the area which is scanned in the identification and / or authentication (the second area) must at least partially overlap with the area which was scanned during the initial detection (the first area). , The greater the overlap, the higher the security with which an item can be identified and / or authenticated.

In a preferred embodiment of the method according to the invention, the first region (from step A1) and the second region (from step B1) are identical or at least substantially identical. By "substantially identical" is meant that in a later scan of the surface it is attempted to scan the same area as was sampled during the initial detection. In the ideal case, the first and the second area are therefore identical - but in practice, it can be difficult to exactly find the area of the initial detection in a later acquisition or exactly "hit". This is a question of positioning accuracy: how exactly is it possible to position an object with respect to a device for scanning the surface of the object so that a defined area of the surface can be scanned?

One way to reduce the positioning accuracy requirements is to maximize the range for scanning. For example, if the absolute accuracy of the positioning is ± 1 mm in one direction and the area in that direction is 1 mm, the accuracy with which it can be positioned is insufficient; there is a risk that the first area and the second area will not match at all. Is the extent of the Range in the direction mentioned but 10 mm, so a sufficiently accurate positioning is very likely given; the first area and the second area deviate from one another by a maximum of 10% in the named direction.

However, an increase in the range is usually associated with an increased sampling time and a larger amount of data for the sampling signal and the signature, so that the range can not be chosen arbitrarily large.

Another way to reduce the requirements for the positioning accuracy, lies in the use of a so-called position encoder. A position transmitter is understood to mean means which conclusively mark a region of a surface. A final labeling of a surface area means that one area of the surface of an object is so highlighted and delimited from other surface areas that this surface area is clearly distinguishable from all other surface areas and that there is no surface area for which there is a lack of clarity; whether it belongs to the designated surface area or not. For example, a locator may be a label having a recess that connects to the article. Within the recess is the area to be scanned. If the region is scanned optically, then the surface of the position sensor, which is arranged around the recess, is preferably designed so that it behaves differently when irradiated with electromagnetic radiation than the marked surface region of the article. If, for example, the object is a paper-like object with a high scattering power, the surface of the position sensor is made, for example, mirror-like. In a tactile scan of the surface area of the article, a label having a recess as a position sensor has the advantage of having edges around the surface area of the article which, in a tactile scan, provide a defined and well-recognizable scanning signal indicating where the surface area of the article starts and where it ends. A positioner thus helps to "find" the area scanned in the initial detection at each later scan for identification and / or authentication purposes.

It has already been pointed out that it can be advantageous to make the area for scanning as small as possible. The smaller the range, the faster a scan can be made, the lower the amount of data that accumulates as a sample signal or signature and the lower the computation time for comparing a current signature to one or more reference signatures. It would therefore be advantageous if the surface of the object would only have to be scanned along a single line to produce a signature. However, it has already been explained that a reduction of the range is accompanied by an increase of the positioning accuracy requirements. If the signature is a surface profile, i. H. the height information of a surface along a single line on the surface, it may be difficult to retrieve that one line in a later acquisition.

Surprisingly, it has been found that this problem of increasing positioning accuracy requirements can be solved by reducing the area for scanning by virtue of the fact that the second area is smaller than the first area and the second area lies within the first area.

A preferred embodiment of the method according to the invention for identification and / or authentication is accordingly characterized in that the second area is smaller than the first area and lies within this first area.

To satisfy sufficient positioning accuracy in step B1, the object must be positioned with respect to the scanning device so that the scanning area (second area) is within a defined larger area (first area). The positioning accuracy requirements decrease accordingly with increasing size of the first area and decreasing size of the second area. As the size of the second area decreases, so does the amount of data available for comparison. In general, a statement about the identity and / or authenticity of an object can be made with greater certainty, the larger the amount of data that describes the identity of the respective item. Here, therefore, a sensible balance must be made between simplified positioning and security in the identification and / or authentication.

The signature resulting from the scanning of the first, larger area and stored as a reference signature is correspondingly larger than any signature that is generated in a later detection for the purpose of identification and / or authentication when scanning the second, smaller area. In step B3 of the inventive method for identification and / or authentication, it is accordingly checked whether the current signature is present within the reference signature. Specifically, this could look like that in the first detection, a first area of the surface is scanned along a plurality of closely spaced lines to determine the topography of that first area and store it as a reference signature. For example, in the identification and / or authentication, only the height profile along a single line (surface profile) located within the first region will be recorded at a later time. In step B3 it is checked whether the surface topography of the first region has a corresponding surface profile at any point. It is not necessary that the line along which a scan was made in the identification and / or authentication is also exactly one of the lines that was used in the determination of the topography in the context of the initial sampling. As already stated above, the individual lines are preferably so close together in determining the topography that a continuous transition is recognizable between them. It is therefore sufficient that the single line lies within the range of the plurality of lines. For corresponding reasons, it is also not necessary for the individual line to run exactly parallel to the multiplicity of lines. Through the continuous transition of the individual surface profiles, which form the topography, the entire topography can be approximated with known mathematical methods and thus any surface profile within the topography can be calculated.

The preferred embodiment of the method according to the invention for identifying and / or authenticating an item in which the second area is smaller than the first area can be advantageously used where there is sufficient time for initial capture while the time for identification and / or authentication in the Comparison is limited.

Examples include works of art or jewelry. These are often created by hand. Hand manufacturing takes more time compared to mechanical manufacturing processes. Therefore, it does not matter if a sufficient amount of time is spent to generate the reference signature by scanning a large (first) range. The later identification and / or authentication z. B. for routine inspection based on a smaller area can be done accordingly faster.

Surprisingly, it has been found that the first and second regions can also be designed such that the second region is larger than the first region and completely encompasses this first region.

A further preferred embodiment of the method according to the invention for identifying and / or authenticating an object is therefore characterized in that the second area is larger than the first area and completely encompasses this first area.

In the first detection, therefore, a reference signature is generated which results from a comparatively small scanning range. In a later generation of a signature for the purpose of identification and / or authentication, a correspondingly larger area is scanned, a signature is generated, and in step B3 it is examined to what extent a reference signature is present in the current signature.

This preferred embodiment provides the same advantages in terms of positioning accuracy and reduced data volumes as in the case where the second range is within the first range (see above). Such an embodiment is advantageous if the initial detection is time-critical in comparison to later identification and / or authentication. This can be the case, for example, in a mechanical production, where the manufactured articles are produced in large numbers and are transported on a conveyor belt at high speed. Here, it is advantageous to scan only a small area of the respective object in a very short time (step A1) in order to detect the respective object for the first time and to generate a corresponding reference signature. In the event of subsequent identification and / or authentication, the items may be incurred in small numbers, and there is more time to scan a larger area in step B1 to ensure that the first area (from step A1) is included.

In step B3 of the inventive method for identifying and / or authenticating an object, as already mentioned, the comparison of the currently generated signature with one or more reference signatures takes place. Here, a distinction can be made between a so-called 1: 1 adjustment and a so-called 1: n comparison. In a 1: 1 comparison, only the comparison of two signatures takes place. This is the case, for example, if there is already information on the supposed identity of the object that is still to be verified (authentication). For example, it is conceivable that the item bears a bar code which indicates the identity of the item. On the basis of the supposed identity, the reference signature can be determined, which is assigned to the respective object. This is then compared with the currently generated signature.

If the identity is not known and should be determined on the basis of the currently generated signature, the currently generated signature is compared with a number n of candidate reference signatures (1: n matching) in order to find the reference signature that matches the current signature generated signature matches (identification).

The comparison itself can be done with mathematical methods that are well known to those skilled in the art. It can z. For example, known methods of pattern matching may be used in which similarities between data sets are searched for (see, for example, US Pat. Image Analysis and Processing: 8th International Conference, ICIAP '95, San Remo, Italy, September 13-15, 1995 , Proceedings (Lecture Notes in Computer Science), WO 2005088533 (A1) . WO2006016114 (A1) . C. Demant, B. Streicher-Abel, P. Waszkewitz, Industrial Image Processing, Springer-Verlag, 1998, p. 133 ff . J. Rosenbaum, Barcode, Verlag Technik Berlin, 2000, p. 84 ff . US 7333641 B2 . DE10260642 A1 . DE10260638 A1 . EP1435586B1 ). Also optical correlation methods are conceivable.

The result of the comparison, z. The degree of correspondence between the compared signatures is then output in step B4 to a user of a corresponding device in the form of a visual or audible message (monitor, printer, speaker, or the like).

After the methods according to the invention have been presented in a general form, reference will now be made to concrete embodiments without, however, limiting the invention thereto.

Show it:

1 (a) , (b): Schematic representation for the optical scanning of a surface

2 : Schematic representation for the optical scanning of a surface with a linear beam profile

3 : Schematic representation of a sensor according to the invention for scanning surfaces

4a - 4c : Scanning signals from a surface

The scanning of a surface area is preferably carried out optically, that is, using a source of electromagnetic radiation and at least one detector for electromagnetic radiation (also referred to as a photodetector). Preferably, a source is used as the radiation source, which can generate electromagnetic radiation with a high intensity. For example, as is known, laser radiation has a high power density and can be bundled well, so that the dimensions of the focused laser beam in the focal plane can be kept correspondingly low. The smaller the dimensions of the scanning beam in the focal plane, the higher the accuracy with which the surface can be scanned.

The cross-sectional profile of the scanning beam in the focal plane should be largely the same for the samples according to steps A1 and B1, so that in the later comparison of signatures according to step B3, there are no too large differences between the signatures due to different resolutions in the scan. The cross-sectional profile is understood to mean the two-dimensional intensity distribution of the radiation in the focal plane.

In 1 is shown schematically how the scanning of a surface area can be accomplished by means of a scanning beam.

The figure shows the surface 1 an article and an assembly comprising a source of electromagnetic radiation 2 and a variety of detectors 5 for electromagnetic radiation. The surface 1 is for better clarity in comparison to the radiation source 2 and the detectors 5 shown greatly enlarged.

From the radiation source, a scanning beam 3 on the surface 1 of the subject. The object is moved relative to the array of radiation source and detectors (indicated by the thick black arrow). The scanning beam passes over the surface. The scanning beam is reflected by the surface in accordance with the law of reflection. Depending on the curvature of the surface reaches the reflected radiation 4 into one of the detectors. In this way, the surface can be scanned and a scanning signal recorded. The surface structure can be determined from the scanning signal.

Instead of the large number of individual detectors, it is also conceivable to use a correspondingly large detector (CCD, CMOS camera). In contrast to dynamic laser focusing (see above), the method described here does not require the use of a mechanically adjustable lens. Surprisingly, it has been found that it is sufficient if the scanning beam is focused on a point on the surface. The movement between object and arrangement of radiation source and detectors then takes place with a constant distance between the object and the arrangement. Due to the height differences on the Surface are not all points in which the scanning beam hits the surface, exactly in the focal plane. Surprisingly, nevertheless, a topography can be derived from the scanning signal. Preferably, therefore, beam sources are used which have a large depth of focus.

The irradiation (scanning) of the surface can take place at an arbitrary angle of almost 0 ° (if reflection still occurs) up to 90 ° relative to the mean surface level. The detection of the reflected radiation can also be carried out at an arbitrary angle of almost 0 ° to 90 ° relative to the mean surface level.

The use of a device according to 1 has the advantage that, in contrast to the known devices for dynamic laser focusing no mechanically adjustable lenses are necessary. Accordingly, an apparatus according to 1 less complex and thus less expensive and less error-prone. In addition, with a device according to 1 the scanning is much faster than with a device for dynamic laser focusing, since no time is required for the mechanical adjustment of a lens.

Furthermore, it was surprisingly found that the determination of a signature does not have to cover the complete surface structure during the scan. The surface texture of many objects is so rich in features that a fraction of it suffices for identification and / or authentication. That means that in the arrangement in 1 in principle, a single sufficient instead of the large number of detectors. This one detector then no longer detects any curvature of the surface but only the signals that are sent from the surface towards the detector. Surprisingly, however, the scanning signal detected by the detector is sufficient to generate a signature for the purpose of identification and / or authentication.

The radiation sent to the surface is preferably not coherent in order to exclude interfering interference phenomena. Coherent radiation falling on a rough surface is known to produce speckle patterns. The speckle patterns are u. a. depending on the angle of incidence and the distance between the radiation source and the surface. Therefore, the speckle patterns are usually difficult to reproduce. The speckle patterns superimpose the reproducible scanning signals due to the direct surface structure and result in a reduction of the signal-to-noise ratio.

Although laser beams are highly intense and can be bundled very well, they are coherent and lead to the unwanted speckle patterns.

Preferably, therefore, a so-called speckle-reduced laser or a non-coherent radiation source such as an LED (LED = light emitting diode) is used as the radiation source. Methods for reducing speckle emissions in the case of coherent radiation are known to the person skilled in the art (see, for example, US Pat. DE102004062418B4 ). Particularly preferred is a so-called high power LED is used. It is also conceivable to use LED arrays, ie an arrangement of several LEDs.

In a preferred embodiment, in step A1 and / or in step B1, the scanning is performed only along one line. Particularly preferably, both in step A1 and in step B1 the scanning is performed only along one line. This means that in the case of using a scanning beam according to 1 it is guided only once in one direction (along a single line) over the surface of an object to pick up a scanning signal. Scanning along a single line can be much faster than scanning along multiple lines, for example, parallel to each other. If both step A1 and step B1 scan along a single line, the time required is minimal.

However, as explained above, as the size of the scan area decreases, it becomes increasingly difficult to retrieve the area detected in the first scan on a later scan. According to the invention this problem is solved in that a linear beam profile is used for scanning. Surprisingly, it has been found that even then a scanning signal and a signature for the purpose of identifying and / or authenticating an object can be determined if the beam profile is extended transversely to the direction of movement. This is schematically in 2 shown. An area 7 a surface 1 an object is by means of a source of electromagnetic radiation 2 irradiated. Part of the reflected radiation 4 is picked up by a detector to pick up a sample signal. The object is moved relative to the radiation source and detector assembly (represented by the thick black arrow). In the surface plane is a line-shaped beam profile, the longer extension is transverse to the direction of movement.

By extending the beam profile in the direction transverse to the direction of movement, the problem of positioning is solved. Instead of a thin line (having a width corresponding to the extension of the dot-shaped beam profile) becomes scanned wide area (with a width corresponding to the longer extension of the linear beam profile). This wide range can be found correspondingly easier in a later scan.

The scanning with a linear beam profile according to 2 is more like an averaging over a plurality of scanning signals resulting from scanning with a point beam profile along a plurality of closely spaced and parallel lines. It is surprising that a signature can be generated from this averaging over a wide range, with which an object can be identified and / or authenticated.

A linear beam profile is defined here as follows: Usually, the intensity in the cross-sectional center of the radiation is highest and decreases toward the outside. The intensity can decrease evenly in all directions - in this case there is a round cross-sectional profile. In all other cases there is at least one direction in which the intensity gradient is greatest and at least one direction in which the intensity gradient is smallest. In the following, the beam width is understood to mean the distance from the center of the cross-sectional profile in the direction of the smallest intensity gradient, at which the intensity has dropped to half of its value in the center. Furthermore, the beam thickness is understood to be the distance from the center of the cross-sectional profile in the direction of the highest intensity gradient, at which the intensity has dropped to half of its value in the center. A linear beam profile refers to a beam profile in which the beam width is greater than the beam thickness by a factor of more than 10. Preferably, the beam width is larger by a factor of more than 50 than the beam thickness, more preferably by a factor of more than 100, and most preferably by a factor of more than 150.

Preferably, the beam thickness is in the range of the mean groove width of the present surface (for definition of the mean groove width, see DIN EN ISO 4287: 1998 ).

For a variety of articles, especially articles of paper, the following beam thicknesses and widths have been found to be suitable:
Beam widths in the range of 2 mm to 7 mm, preferably in the range of 3 mm to 6.5 mm, more preferably in the range 4 mm to 6 mm and most preferably in the range 4.5 mm to 5.5 mm.
Beam thicknesses in the range of 5 microns to 35 microns, preferably in the range of 10 microns to 30 microns, more preferably in the range of 15 microns to 30 microns, most preferably in the range of 20 microns to 27 microns.

It is known to the expert in optics how a corresponding beam profile can be generated by means of optical elements. Optical elements are used for beam shaping and focusing. In particular, lenses, diaphragms, diffractive optical elements and the like are referred to as optical elements.

As the cross-sectional profile of the scanning beam at the focal point decreases in size, the signal-to-noise ratio increases because the intensity is distributed over a smaller area. Empirically, it has been found that with decreasing size of the cross-sectional profile at the focal point, it becomes increasingly difficult to obtain reproducible signals. Apparently, this is because the surface of the object to be authenticated can no longer be positioned sufficiently accurately with respect to the decreasing cross-sectional profile. Apparently, it becomes increasingly difficult to make the area sufficiently accurate on re-authentication.

Surprisingly, it has been found that the abovementioned ranges for the beam thickness and the beam width are very well suited for achieving the positioning that is sufficiently accurate for reproducibility on the one hand, and for a sufficiently accurate authentication on the other hand. To achieve noise ratio.

In one scan, the scanner and the object whose surface is to be scanned are moved at a constant distance relative to each other. When using a linear beam profile for scanning a surface area, the beam width is transverse to the direction of movement. The angle between the direction of movement and the direction of the beam width is preferably between 10 ° and 90 °, more preferably between 45 ° and 90 °, most preferably between 70 ° and 90 °.

It is conceivable both a movement of the scanning device relative to the object and a movement of the object relative to the scanning device.

The movement may be continuous at a constant rate, accelerating or decelerating, or discontinuous; d. H. z. B. gradually. Preferably, the movement is carried out at a constant speed.

When using a scanning beam for scanning a surface according to 1 or 2 the radiation intensity incident on at least one detector is detected as a function of time. Usually, measuring signals are recorded and updated at a constant measuring frequency. If the relative movement between the surface and the detector takes place at a constant speed, then the time between two consecutively recorded measurement signals corresponds to a defined and constant distance. In this case, it is easily possible to transform the measurement signals acquired as a function of time into a function of the location. When speed fluctuations occur, a mechanical encoder (encoder) is preferably used, which is known to those skilled in signal technology.

The preferred scanning of the surface with a linear beam profile leads to a third object of the present invention, a sensor which can be advantageously used for scanning:

Sensor for scanning a surface

A third object of the present invention is a sensor for scanning a surface of an article.

• – eine Quelle für elektromagnetische Strahlung, die so angeordnet ist, dass elektromagnetische Strahlung in einem Winkel α in Bezug zur Oberflächennormalen des Gegenstands auf den Gegenstand gesandt werden kann,
• – mindestens einen Fotodetektor zur Aufnahme reflektierter Strahlung, der so angeordnet ist, dass die von dem Gegenstand unter einem Winkel β in Bezug zur Oberflächennormalen des Gegenstands reflektierte Strahlung erfasst wird.

The sensor according to the invention comprises at least

• A source of electromagnetic radiation arranged so that electromagnetic radiation can be transmitted to the object at an angle α with respect to the surface normal of the object,
• At least one photodetector for receiving reflected radiation arranged to detect the radiation reflected from the object at an angle β with respect to the surface normal of the object.

It is conceivable that the angles α and β are equal. It is also conceivable that the angles α and β are different. Preferably, the amounts of the angles α and β are equal to (| α | = | β |).

The amounts of the angles α and β are in the range of 5 ° to 90 °, preferably in the range 20 ° to 80 °, more preferably in the range 30 ° to 70 °, most preferably in the range 40 ° to 60 °.

In principle, all sources of electromagnetic radiation which emit radiation which is at least partially reflected by the surface of the object to be scanned can be used as the source of electromagnetic radiation in the sensor according to the invention. With regard to a compact and cost-effective design of the sensor according to the invention, LEDs or (preferably speckle-reduced) laser diodes are preferred. Preferably, radiation sources are used which emit monochromatic or largely monochromatic radiation visible to human radiation; Particularly preferably, a radiation source with a wavelength between 600 nm and 780 nm is used.

1 to 6 photodetectors, more preferably 1 to 3 photodetectors are preferably used in the sensor according to the invention.

In principle, all electronic components which convert electromagnetic radiation into an electrical signal can be used as photodetectors in the sensor according to the invention. With regard to a compact and cost-effective design of the sensor according to the invention, photodiodes or phototransistors are preferred. Photodiodes are semiconductor diodes that convert electromagnetic radiation at a p-n junction or pin transition through the internal photoelectric effect into an electrical current. A phototransistor is a bipolar transistor with a pnp or npn layer sequence whose pn junction is accessible to the base-collector barrier layer for electromagnetic radiation. It resembles a photodiode with connected amplifier transistor.

The sensor according to the invention has optical elements which generate a linear beam profile.

The linear beam profile of the sensor according to the invention is characterized in that the beam width is greater by a multiple than the beam thickness. Preferably, the beam width is at least 50 times the beam thickness, more preferably at least 100 times and most preferably at least 150 times.

The jet width is in the range of 2 mm to 7 mm, preferably in the range of 3 mm to 6.5 mm, more preferably in the range 4 mm to 6 mm and most preferably in the range 4.5 mm to 5.5 mm.

The jet thickness is in the range of 5 μm to 35 μm, preferably in the range of 10 μm to 30 μm, particularly preferably in the range of 15 μm to 30 μm, very particularly preferably in the range of 20 μm to 27 μm.

The sensor according to the invention is characterized in that the beam width is transverse to the direction in which the sensor according to the invention for scanning over the surface of an object is guided.

The sensor according to the invention optionally has means for connecting a plurality of sensors or for connecting a sensor to a holder. These means make it possible to connect two or more sensors in a predetermined manner. The connection of two or more sensors is reversible, ie it is solvable.

The connecting means can also be used to attach the sensor according to the invention to a holder.

3 shows by way of example a preferred embodiment of a sensor according to the invention without radiation source and photodetectors in cross-section from the side. The sensor includes a block 10 with a designated outer surface 15 , This designated outer surface - hereafter referred to as outer surface - is directed at the scanning of the surface of the corresponding object.

The block 10 serves to accommodate all optical components of the sensor according to the invention. He has at least two bushings 11 . 12 , which converge toward the designated outer surface.

The first implementation 11 runs at an angle γ with respect to the normal 16 the outer surface (short outer surface normal) and serves to accommodate the source of electromagnetic radiation.

A second implementation 12 is at an angle δ with respect to the outer surface normal 16 and serves to receive a photodetector.

The amounts of the angles γ and δ are preferably the same.

The amounts of the angles γ and δ are in the range of 5 ° to 90 °, preferably in the range 20 ° to 80 °, more preferably in the range 30 ° to 70 °, most preferably in the range 40 ° to 60 °.

In a preferred embodiment of the sensor according to the invention are one or two further feedthroughs 13 . 14 present, which serve to receive one or two other photodetectors. These are at an angle ε ₁ and / or ε ₂ for the second implementation 12 arranged. The size of the angle ε ₁ and / or ε ₂ is 1 ° to 20 °, preferably 5 ° to 15 °.

Preferably, all bushings are in one plane to allow a compact design of the sensor.

The use of a block with two to four feedthroughs for receiving a radiation source and one or more photodetectors offers the advantage that the optical components can be arranged in a simple manner but nevertheless in a defined manner relative to one another. Preferably, there is a stop in the passage for the radiation source. Against this stop, the radiation source of the sensor is pushed into the bushing, so that it assumes a predetermined fixed position with respect to the block and the photodetectors. If the radiation source already has optical elements for beam shaping and focusing connected to it, which is customary, for example, in many radiation sources commercially available today, the focus point of the radiation source is at the same time clearly fixed due to the fixation of the radiation source. The further feedthroughs for receiving photodetectors can also be provided with a stop, wherein the position of the photodetectors must be less accurate than the position of the radiation source.

The block can be easily z. B. by injection molding of plastic one or two pieces are made. By means of injection molding, components can be produced with high accuracy in large quantities and in a short time. This allows cost-effective mass production of sufficiently precise components. The passages may already be provided in the injection molding tool or in the block subsequently by means of z. B. holes are introduced. Preferably, all components of the block are already manufactured by injection molding in one step. It is also conceivable to mill the block, for example made of aluminum or plastic and the bushings z. B. to realize by means of holes. Further methods known to the person skilled in the art for producing a block with defined passages are conceivable.

The sensor may have a housing into which the block is inserted. In the housing of the sensor preferably further components are introduced, for. B. the control electronics for the radiation source, signal preprocessing electronics, complete evaluation and the like. The housing preferably also serves to anchor a connection cable with which the sensor according to the invention can be connected to a control unit and / or a data acquisition unit for controlling the sensor and / or for detecting and further processing the characteristic reflection patterns.

Optionally, the sensor may have a window located in front of, behind or in the outer surface protecting the optical components from damage and contamination. Preferably, the window forms the outer surface of the sensor. The window is at least for the wavelength the radiation source used at least partially transparent.

The inventive sensor in 3 is further characterized by the fact that the central axes of the bushings are in one point 18 cut outside the block. Surprisingly, it has been found that it is advantageous for the identification and / or authentication according to the invention if the point of intersection of the central axes is at the same time the focal point of the radiation source and lies at a distance of 2 to 10 mm from the outer surface.

For scanning the surface of an object, the sensor according to the invention is correspondingly guided at a distance above this object, so that the focal point and intersection of the central axes lie on the surface of the object.

In the mentioned distance range of 2 to 10 mm, the positioning of the surface to be scanned of an object with respect to the radiation source and the photodetectors is simple and sufficiently accurate. As the distance between the sensor and the object increases, the angle of the sensor with respect to the surface of the object must be increasingly accurately maintained in order to be able to detect a predetermined area of the surface so that the positioning requirements increase.

Furthermore, the radiation intensity decreases with increasing distance from the radiation source, so that with an increasing distance between sensor and object the correspondingly reduced radiation intensity arriving at the object would have to be compensated by a higher power of the radiation source.

The sensor according to the invention can be manufactured inexpensively in mass production on an industrial scale, has a compact design, is intuitive and easy to handle, can be flexibly used and expanded and provides reproducible and transferable results.

4a . 4b and 4c show scanning signals resulting from the scanning of an object with a linear beam profile. The scanning signal was in each case with a sensor according to 3 added. The ordinate in each case shows the voltage signal I (in arbitrary units) of the photodetector used, which is proportional to the intensity of the incident radiation. The abscissa shows the distance X traveled in the scan along a single line in cm. In all cases, a single photodetector in the second feedthrough ( 12 ) used. The scanned article was a composite consisting of the special paper 7110 from 3M (3M 7110 litho paper, white) and a laminated protective film PET Overlam RP35 from UPM Raflatac. The radiation source used was a speckle-reduced laser diode (Flexpoint line module FP-HOM-SLD, Laser Components GmbH). The beam profile was linear, with a beam width of 5 mm and a beam thickness of 25 μm.

In the case of 4a and 4b the same area was scanned. The signals are very similar. In the case of 4c was another area than in the cases of 4a and 4b sampled. The signal of 4c is clearly different from the signals of the 4a and 4b , A comparison of the signals from the 4a and 4b yielded a correlation coefficient of 0.98, while comparing the signals from the 4a and 4c brought a correlation coefficient of 0.6. The scanning signals could still be reproduced very well even after a long time.

The scanning signals in the 4a . 4b and 4c have a variety of characteristics that can be used to generate a signature for the purpose of identification and / or authentication. It is thus possible to distinguish between different objects as well as later to recognize identical objects.

An analogous experiment with a high-power LED array from the company Blau Optoelectronics GmbH (FP-65 / 0.5LF-LED, beam width 10 mm, beam thickness 60 μm) produced a similar result, whereby the signal-to-noise ratio was lower ,

LIST OF REFERENCE NUMBERS

1

surface

2

Source of electromagnetic radiation

3

scanning beam

4

reflected beam

5

photodetector

6

linear beam profile

7

scanned area

10

block

11

first implementation for receiving a radiation source

12

second passage for receiving a photodetector

13

further implementation for receiving a photodetector

14

further implementation for receiving a photodetector

15

outer surface

16

Outer surface normal

18

focus point

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• EP 2009/002809 [0014]
• WO 2005/088533 (A1) [0016, 0017, 0017, 0018, 0034]
• WO 2005088533 (A1) [0068]
• WO 2006016114 A1 [0068]
• US 7333641 B2 [0068]
• DE 10260642 A1 [0068]
• DE 10260638 A1 [0068]
• EP 1435586 B1 [0068]
• DE 102004062418 B4 [0087]

Cited non-patent literature

• Wochenblatt für Papierfabrikation, ISSN0043-7131, Volume 117, April 1989, No. 7; Pages 271 to 274 [0005]
• DIN EN ISO 4287: 1998 [0007]
• DIN EN ISO 4288: 1998 [0007]
• Rudolf L. van Renesse, Optical Document Security, Third Edition, Artech House Boston / London, 2005 (pp 63-259) [0012]
• DIN EN ISO 4287: 1998 [0025]
• Wochenblatt für Papierfabrikation, ISSN0043-7131, Volume 117, April 1989, No. 7; Pages 271 to 274 [0033]
• DIN EN ISO 4287: 1998 [0037]
• DIN EN ISO 4287: 1998 [0038]
• Image Analysis and Processing: 8th International Conference, ICIAP '95, San Remo, Italy, September 13-15, 1995 [0068]
• C. Demant, B. Streicher-Abel, P. Waszkewitz, Industrial Image Processing, Springer-Verlag, 1998, p. 133 ff. [0068]
• J. Rosenbaum, Barcode, Verlag Technik Berlin, 2000, p. 84 ff. [0068]
• DIN EN ISO 4287: 1998 [0093]

Claims (14)

A method of generating a signature of an article at least comprising the following steps: A1: scanning a first area of a surface of the object and picking up a scanning signal representing at least a part of the surface structure within this first area, A2: generation of a signature from the scanning signal determined in step A1, A3: linking the signature with the object, A4: storage of the signature in a form in which it is available for later comparison purposes. Method for identifying and / or authenticating an article, comprising at least the following steps: B1: scanning a second area of a surface of the object and picking up a scanning signal representing at least a part of the surface structure within this second area, B2: generation of a signature from the sampling signal determined in step B1, B3: comparison of the signature determined in step B2 with at least one reference signature, B4: generation of a notification of the identity and / or authenticity of the object depending on the result of the comparison in step B3. A method according to claim 2, characterized in that the second region is smaller than the first region of claim 1 and lies within this first region. A method according to claim 2, characterized in that the second region is larger than the first region of claim 1 and completely comprises this first region. A method according to claim 2, characterized in that the second region is identical or at least substantially identical to the first region of claim 1. Method according to one of claims 1 to 5, characterized in that the scanning is carried out optically with non-coherent radiation. Method according to one of claims 1 to 6, characterized in that for scanning the object and a device for scanning the object are moved at a constant distance from each other and the scanning is carried out along a single line. A method according to claim 7, characterized in that the scanning is carried out with a linear beam profile whose longer extension is transverse to the direction of movement. A method according to claim 8, characterized in that the beam width of the linear beam profile by a factor of more than 50 is greater than the beam thickness. A method according to claim 7 or 8, characterized in that the beam thickness of the linear beam profile is in the range of the mean groove width of the present surface. Sensor for scanning a surface, at least comprising A block having an outer surface, a first passage tapering toward the outer surface at an angle relative to the normal of the outer surface, and a second passage tapering toward the outer surface at an angle δ relative to the normal of the outer surface, the amounts the angles γ and δ are equal, A radiation source, which is arranged in the first passage and can send a scanning beam in the direction of the outer surface, Optical elements for forming a linear beam profile, - A photodetector, which is arranged in the second passage and directed towards the outer surface. Sensor according to claim 11, characterized in that the beam width in the range of 3 mm to 6.5 mm, preferably in the range of 4 mm to 6 mm, particularly preferably in the range of 4.5 mm to 5.5 mm, and the beam thickness in the range of 10 microns to 30 microns, preferably in the range of 15 microns to 30 microns, more preferably in the range of 20 microns to 27 microns. Sensor according to one of claims 11 or 12, characterized in that the amounts of the angles γ and δ in the range of 5 ° to 90 °, preferably in the range 20 ° to 80 °, particularly preferably in the range 30 ° to 70 °, especially preferably in the range 40 ° to 60 °. Sensor according to one of claims 11 to 13, further comprising two further feedthroughs for receiving photodetectors, which are arranged at an angle of ε ₁ and ε ₂ to the second feedthrough, wherein the size of the angle ε ₁ and ε ₂ 1 ° to 20 °, preferably 5 ° to 15 °.

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