DE102009025061A1 - Method for generating e.g. barcode of paper to identify object, involves combining signatures with object, storing signatures in specific form in radio-frequency identification-chip and comparing signatures with reference signatures - Google Patents

Abstract

The method involves scanning two regions (7) of an object and receiving sampling signals, which represent respective parts of surface structures (1) of the object within respective regions. Two signatures are generated from the sampling signals. The signatures are combined with the object and stored in a specific form in a radio-frequency identification-chip. The signatures are compared with reference signatures. Information about authenticity and/or identity of the object is generated based on the comparison result. An independent claim is also included for a sensor for scanning a surface.

Description

object The present invention is a method for identification and / or authentication of items based on theirs Surface finish. Subject of the present invention is also a sensor for scanning a surface.

The Surface texture of objects plays in many technical products and processes play an important role, 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 Bekk's method of determining the roughness of a paper or board sample by measuring an airflow passing between a baffle and the sample surface (see FIG. ISO 5627 ).

at The direct methods can be tactile and optical methods be differentiated. With tactile processes become surfaces scanned point by point with mechanical buttons. The button 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 together lying surface profiles are obtained the areal Scanning the topography. Similar methods, the contactless are scanning electron or atomic force microscopy (im so-called non-contact mode).

One Example of an optical method for topography determination is dynamic laser focusing (see, for example, Wochenblatt for Papermaking, ISSN0043-7131, Volume 117, April 1989, No. 7; Pages 271 to 274). For dynamic laser focusing a laser is focused on the surface by means of a lens. The lens can by means of a servomotor perpendicular to the surface (in the z direction) are moved. A sensor determines the respective z position of the lens in a focused position and thus provides the topography information during the sample through a xy table is moved under the lens.

Farther can provide topographic information of a surface also for example with an acoustic or a chromatic Near field sensor, with an eddy current sensor or a phase white light interferometer be won.

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 common to those recorded by direct methods Data sets for surface topography on a few key figures to condense. The compression of data volumes to a few key figures allows a classification of objects. By the compression However, the data volumes on a few key figures are individual of the individual object lost because of the key figures leaves only on material classes close, but not on individual objects.

The Detecting and recognizing objects, however, plays for example in product tracking and in connection with counterfeit products an important role.

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 for determination z. B. the price. she However, they do not provide protection against counterfeiting, as they are light copy and transfer to other objects.

ID cards, Banknotes, products, etc. are now forgery protection provided with elements that only with specialized knowledge and / or high technical Effort can be imitated. Such elements will be referred to here as security elements. The authenticity of an object can be checked for the existence of one or more security elements become.

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 ).

One Much of today commercially available However, security elements do not allow individualization, i. H. many objects carry the same security element. The objects, which carry the same security element, can not be based on the Differentiate security elements.

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.

To In the prior art are also methods for identification and Authentication known in which no further characteristics than those used to provide 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.

outgoing The described prior art thus sets itself the task of to provide a method with which a variety of different Identified and / or authenticated objects can. The sought process should distinguish the like Allow objects to do so Procedures without expensive tools, such as individualized holograms or the like, based on the individualization of similar objects according to the prior art done can. The process sought should be inexpensive, be intuitive and easy to execute, flexible to use and be extensible, reproducible and transferable Deliver results and be suitable for mass production.

Surprised was found to identify objects based on their surface texture and can be authenticated. It has the surface of objects over individual characteristics relevant to the particular item are characteristic. These features allow the distinction of similar objects.

Under similar objects become such objects understood, which are evidently the same, but not identical, such as B. the individual sheets of a pile of paper or individual components from a series production.

The individual surface finish is surprisingly not limited to types of objects or materials, but in principle applies to all objects. So you can surprisingly even with polished mirrors, at which one of a smooth surface without significant Surface structure would speak, in the atomic Area 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. If an object is sensitive to light, the determination of the surface condition could be with a tactile method. If an object should be sensitive to pressure, so the determination of the surface condition could be contactless z. B. by means of an optical process.

Under An object is understood as 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, Figure 2 ). Topography and surface profile are collectively referred to as surface structure.

Under Identification is a process that is unique Recognition of an object serves.

Under Authentication becomes the process of verification (Verification) of an alleged identity. The authentication of objects is the finding that these are authentic - so they are unchanged, not copied and / or not forged originals.

Method for generating a Signature of an object

One The first object of the present invention is a method for Generation of a signature of an object.

• 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 item. It contains information about characteristic features of the object. This results in the characteristic features the unique surface texture of each Object.

The Scanning a first area of a surface of a Item according to step A1 can with any Procedures are carried out with a surface structure an item can be determined, for B. with a tactile or optical methods. Here are already commercial devices in the market that can be used. To be favoured Method used a surface structure contactless to capture. Particular preference is given to using optical methods.

The The result of the sampling is a scanning signal representing the surface structure represented within the first area.

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 2 . 3 and 5 the following publication: Wochenblatt für Papierfabrikation, ISSN0043-7131, Volume 117, April 1989, No. 7; Pages 271 to 274. Each 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 des Sensors 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 Ge The piece is moved sideways (perpendicular to the direction in which the button was moved to the object) and the button is moved 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 stage performs a uniform motion at a constant speed, it will always travel the same distance between taking two readings from the sensor. 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 carried out 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 created a signature from the scanning signal. The signature is according to the invention used the item at a later date too identify and / or authenticate. Of every object, which is identified at a later date and / or must first be a signature to be created. This process in which the signature of an object is determined for the first time, is also here as first registration designated. If the signature of an object is present, this can get saved. At a later date on which the item is recaptured, d. H. his signature again is determined, the stored signature as a reference for comparison purposes be used.

The Signature is thus a storable and machine processable Information obtained from the scanning signal and for the purpose of Identification and / or authentication can be used. Under storable is understood that the signature to a later Time taken up for example for comparison purposes again can be. By machine processing is meant that the signature read by machine and with a machine different Arithmetic and / or memory operations can be subjected.

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 ).

As well it is conceivable, the sampling signal or a filtered sampling signal undergo a mathematical transformation to get a record generate better for the purpose of identification and / or Authentication, as the sample signal or a filtered one Sampling signal itself. As an example of such a transformation is called a Fourier transform, which is a location independent Representation of the sampling signal generated.

Farther it is conceivable to use characteristic patterns from the scanning signal extract and use this extracted data as a signature (Data reduction).

In step A3 of the inventive method for generating a signature, the Signa linked to the object. 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). It is also conceivable to associate the article with a sticker that 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 conceivable.

at For example, a virtual shortcut becomes a unique one Number assigned to the respective item (ID number, Batch number or the like) in a database with the signature connected. The signature can be, for example, this number contained in a so-called header (metadata at the beginning of a file). The link ensures that a clear and unambiguous Assignment between signature and object exists. Based on the signature can be clearly attributed to the associated object shut down.

In Step A4 of the method according to the invention takes place storing the signature in a form in which it is used for later comparison purposes is available.

The Storage can, for example, on an electronic storage medium (Semiconductor memory), an optical storage medium (eg 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 article itself or as Hologram.

After this the signature is generated and stored for the first time, is the respective one Subject is recorded and may be at a later date identified and / or authenticated by its signature. The stored signature is also referred to here as a reference signature.

• 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.

Method for Identifying and / or Authenticating an Item A second subject of the present invention is a method for identifying and / or authenticating an item, 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.

The Inventive method for identification and / or authentication of an item is timed to the invention Downstream of a method for generating a signature.

For Steps B1 and B2 apply to steps A1 and A2, respectively described, d. H. These steps are largely done in the same Wise.

In However, step A1 is a first area of a surface called during step B1 cm second area of a Called surface.

In order to a later identification and / or authentication at all possible, the area must be in the identification and / or authentication is scanned (the second area) at least partially overlap with the area at the first reading has been sampled (the first area). ever the larger the overlap, the higher is the security with which an item is identified and / or can be authenticated.

In a preferred embodiment of the invention Methods are the first area (from step A1) and the second one Area (from step B1) identical or at least substantially identical. Under "largely identical "is understood that at a later Sampling the surface is trying the same area to be sampled, which was also sampled at the initial reading. Ideally, the first and the second area are identical - but In practice, it can be difficult to change the field of Initial detection to be found exactly in a later acquisition or exactly to "meet". This is a matter of Positioning accuracy: how exactly succeeds an object opposite a device for scanning the surface of the object to position, leaving a defined area of the surface can be sampled?

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. However, if the extent of the area in that direction is 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.

A However, enlargement of the range is common also with an increased time spent on the scan and with a larger amount of data for the scanning signal and the signature are connected so that the area can not be chosen arbitrarily large.

A Another possibility, the requirements for positioning accuracy To reduce, lies in the use of a so-called position sensor. A position transmitter is understood to mean a range Finally mark a surface. Under a final marking of a surface area It is understood that an area of the surface of an object so highlighted and over other surface areas is delimited so that this surface area is unique is distinguishable from all other surface areas and that there is no surface area for which one Uncertainty exists as to whether he marked Surface area belongs or not. A position transmitter For example, may be a label with a recess that with the object is connected. Within the recess is the area to be scanned. If the area is optically scanned, so is the surface of the locator, which is around the recess is arranged, preferably designed so that when irradiated with electromagnetic radiation shows a different behavior than the characterized surface area of the article. is the article, for example, a paper-like object with a high scattering power, the surface of the position sensor For example, designed mirroring. With a tactile scan the surface area of the article has a label with a recess as a position transmitter the advantage of having edges are present around the surface area of the article, the in a tactile scan a defined and well recognizable Provide a sampling signal indicating where the surface area is of the object begins and where it ends. A position sensor helps that is, the area that was scanned at first reading, at each later scan for the purpose of identification and / or authentication "to find again".

It has already been pointed out that it can be beneficial make the area for scanning as small as possible. The smaller the area, the faster a scan can be take place, the lower the amount of data, as a sampling signal or signature incurred and the lower the computing time for the comparison of a current signature with one or more reference signatures. It would have advantages if the surface of the Object would only have to be scanned along a single line, to create a signature. However, it has already been explained that a reduction of the area with an increase the requirements for the positioning accuracy goes hand in hand. is the signature is a surface profile, i. H. the height information a surface along a line on the surface, so it may be difficult to follow this line at a later time Find again.

Surprised It has been found that this problem of increasing demands to the positioning accuracy as the area for scanning is reduced It can be solved by making the second area smaller as the first area and the second area within the first area Area lies.

A preferred embodiment of the invention Method for identification and / or authentication is accordingly characterized in that the second region is smaller than the first one Area is and lies within this first area.

to Fulfilling a sufficient positioning accuracy in Step B1, the object must be in relation to the scanning device so be positioned so that the scanning area (second area) within a defined larger area (first area). The requirements for the positioning accuracy increases accordingly with increasing size of the first area and decreases with decreasing size of the second area. As the second area decreases in size of course, the amount of data, which for a Comparison is available. Generally, that is one Statement about the identity and / or authenticity an object with higher security can, the larger the amount of data that the Identity of each item describes. Here must So a meaningful balance between simplified positioning and security in identification and / or authentication to be hit.

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. In concrete terms, this could be the case that, during initial recording, a first area of the upper is scanned along a plurality of closely spaced lines and so the topography of this first area is determined and stored 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 invention Method for identifying and / or authenticating a An article wherein the second area is smaller than the first one Range, can be used advantageously where sufficient Time to initial capture exists while the time for identification and / or authentication in comparison thereto is.

When Examples are art objects or jewelry called. These are often created by hand. The manual production needed compared to mechanical manufacturing process more time. Therefore, it does not matter when creating the reference signature is operated a corresponding amount of time, by scanning a large (first) area. The later identification and / or authentication z. B. for routine inspection on the basis of a smaller one Area can be done faster.

Surprised it was found that the first and second area also designed this way that can make the second area bigger than the first area is and this first area is complete includes.

A further preferred embodiment of the invention Method for identifying and / or authenticating a Subject is therefore characterized in that the second area is larger than the first area and this first Area completely covered.

at the initial detection is thus generated a reference signature, the results in a comparatively small scanning range. At a later generation of a signature for the purpose of identification and / or authentication becomes a correspondingly larger Scanned area, generates a signature and examined in step B3, to what extent a reference signature is present in the current signature.

By this preferred embodiment, the same result Advantages in terms of positioning accuracy and reduced data volumes as in the case where the second area is within the first Area is located (see above). Such an embodiment is advantageous if the initial assessment compared to the later Identification and / or authentication is time critical. This may be the case in a machine manufacturing, for example where the manufactured items in large numbers accumulate and on a conveyor belt at great speed be transported. Here it is advantageous, only a small one Scanning area of each item in a very short time (Step A1) to capture the respective object for the first time and to generate a corresponding reference signature. At the later Identification and / or authentication fall the objects possibly in small numbers and there is more time, one scan larger area in step B1 to ensure that the first area comprises (from step A1) becomes.

In Step B3 of the method according to the invention for Identification and / or authentication of an object takes place, As already mentioned, the comparison of the currently generated signature with one or more reference signatures. Here can between a so-called 1: 1 comparison and a so-called 1: n comparison. In a 1: 1 comparison, only the comparison of two takes place Signatures. This is the case, for example, if there is already information to the alleged identity of the object, which are still to be checked (authentication). For example, it is conceivable that the item is a barcode which points to the identity of the object. On the basis of the supposed identity, the reference signature determined, which is assigned to the respective object. This is then compared with the currently generated signature.

If the identity is unknown and should be determined based on the currently generated signature, the currently generated signature will be marked with a Number n of candidate reference signatures compared (1: n comparison) to find the reference signature that matches the currently generated signature (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 pattern matching techniques may be used to search for similarities between data sets (see, eg, 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. For example, the degree of agreement between the compared signatures, then becomes in step B4 a user of a corresponding device in the form of a visual or audible message (monitor, printer, Speakers, etc.).

After this the method according to the invention has been presented are now closer to specific embodiments be received, but without limiting the invention thereto.

It demonstrate:

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

4 : Scanning signal of 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 called photodetector). Preferably As a radiation source a laser is used, the electromagnetic Can generate radiation with a high intensity. laser radiation can also be bundled well, so the dimensions of the focused laser beam in the focal plane correspondingly low can be kept. The smaller the dimensions of the scanning beam in the focal plane, the higher the accuracy with which the surface is scanned can.

The Cross-sectional profile of the scanning beam in the focal plane should be at the scans according to steps A1 and B1 as far as possible be the same, so in the later comparison of signatures not too big differences according to step B3 between the signatures due to different resolutions present during the scan. Under the cross-sectional profile is the two-dimensional intensity distribution of the radiation in the focal plane understood.

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.

At It is also conceivable to use the large number of individual detectors a correspondingly large detector (CCD, CMOS camera) use. In contrast to dynamic laser focusing (see above) it is not necessary to have a mechanically adjustable lens use. Surprisingly, it was found that it was enough when the scanning beam is at a point on the surface is focused. The movement between object and arrangement from radiation source and detectors then takes place at a constant distance between object and arrangement. Due to the height differences on the surface are not all the points in which the Scanning beam hits the surface, in the focal plane. Surprisingly Nevertheless, a topography can be derived from the scanning signal.

Irradiation (scanning) of the surface can take place at any angle from almost 0 ° (if reflection still occurs) 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 components 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 much faster than with a device for dynamic laser focusing, since no mechanical adjustment of a lens is required.

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 preferred not coherent to disturbing interference phenomena excluded. Preferably, as a radiation source a Laser used. As known to those skilled in the art, the coherence length of different commercially available lasers. Preferably a laser is used whose coherence length for technical reasons already so low that at the scanning no longer coherent radiation on the surface arrives. It is also conceivable the path length of the laser beam until reaching the surface by suitable measures correspondingly long so that no coherent Radiation reaches the surface more. Also suitable Means for reducing the coherence length conceivable.

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 the extension of the beam profile in the direction transverse to the direction of movement the problem of positioning is solved. Instead of a thin line (with a width that is the extension of the punctiform Beam profile corresponds) is a wide range (with a width, that of the longer extension of the linear Beam profile corresponds) scanned. This wide range can recovered in a later scan corresponding easier become.

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 also be generated from this averaging over a wide range with which an object can be identified and / or authenticated.

A scanning signal resulting from scanning with a linear beam profile is included playfully in 4 shown. The ordinate shows the voltage signal (in arbitrary units) of the photodetector used, which is proportional to the intensity of the incoming radiation. The abscissa represents the distance traveled in the scan along a single line in cm. The scanning signal was measured with a sensor according to 3 added. It was a single photodetector in the second implementation ( 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 scanning signal in 4 has a variety of features that can be used to generate a signature for the purpose of identification and / or authentication. The scanning signal could still be reproduced very well even after a long time.

One Line beam profile is defined here as follows: Usually is the intensity in the cross-sectional center of the radiation highest and decreases from the outside. The intensity can decrease evenly in all directions - in In this case, there is a round cross-sectional profile. In all others Cases, there is at least one direction in which the intensity gradient is greatest and at least one direction, in the intensity gradient is the smallest. Hereinafter is under the beam width that distance from the center of the cross-sectional profile understood in the direction of the smallest intensity gradient, where the intensity is at half its value has sunk in the center. Furthermore, under the beam thickness of the one Distance from the center of the cross section profile in the direction of the highest Intensity gradient understood in which the intensity has fallen to half of its value in the center. Under a linear beam profile becomes a beam profile in which the beam width is increased by a factor of more than 10 is greater than the beam thickness. Is preferred the beam width by a factor of more than 50 larger as 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 ).

the A specialist in optics is known, such as a corresponding beam profile can be generated by means of optical elements. Optical elements serve for beam shaping and focusing. As optical elements In particular, lenses, diaphragms, diffractive optical elements and the like.

at a scan, the scanner and the object whose surface is to be scanned, in constant Distance moved relative to each other. When using a linear Beam profile for scanning a surface area is located the beam width transverse to the direction of movement. The angle between Movement direction and 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 opposite to both a movement of the scanning device the object as well as a movement of the object the scanning conceivable.

The Movement can be continuous with constant speed, accelerating or decelerating, or discontinuous, d. H. z. B. gradually. Preferably, the movement is carried out with the same 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 for a third subject of the present invention Invention, a sensor that is advantageously used for scanning can be:

Sensor for sampling a surface

One third object of the present invention is a sensor for Scanning a surface of an object.

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

The Amounts of the angles α and β are in the Range from 5 ° to 90 °, preferably in the range 20 ° to 80 °, particularly preferably in the range 30 ° to 70 °, completely particularly 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 laser in the sensor according to the invention. With regard to a compact and cost-effective design of the sensor according to the invention laser diodes are preferred. Laser diodes are well known; They are semiconductor devices in which a pn junction is operated with high doping at high current densities. The choice of semiconductor material determines the emitted wavelength. Preferably, laser diodes are used which emit visible radiation. Particular preference is given to using class 1 or 2 lasers. Under classes, the laser protection classes according to the Standard DIN EN 60825-1 understood: lasers are classified in classes of dangerousness to eyes and skin. Class 1 includes lasers whose irradiation values are below the maximum permissible irradiation values, even during continuous irradiation. Class 1 lasers are not hazardous and do not require any additional protective measures other than the corresponding marking on the device. Class 2 includes lasers in the visible range, for which radiation of less than 0.25 ms is harmless to the eye (the duration of 0.25 ms corresponds to a blinking reflex which can automatically protect the eye against prolonged irradiation). In a particularly preferred embodiment, class 2 laser diodes having a wavelength between 600 nm and 780 nm are used.

Prefers be in the inventive sensor 1 to 6 Photo detectors, particularly preferably 1 to 3 photodetectors used.

When Photodetectors can in the invention Sensor basically all electronic components are used convert the electromagnetic radiation into an electrical signal. With regard to a compact and cost-effective design The sensor according to the invention become photodiodes or phototransistors preferred. Photodiodes are semiconductor diodes, the electromagnetic radiation at a p-n junction or pin transition through the inner photo effect into one convert electricity. A phototransistor is a bipolar transistor with pnp or npn layer sequence whose pn junction of the Base-collector barrier for electromagnetic radiation is accessible. It resembles a photodiode with connected amplifier transistor.

Of the Sensor according to the invention has optical Elements which produce a linear beam profile.

The line-shaped beam profile of the invention Sensor is characterized in that the beam width to a Many times larger than the beam thickness. Prefers the beam width is at least 50 times the beam thickness, more preferably, it is at least 100 times and most preferably at least 150 times.

The Beam width is in the range of 2 mm to 7 mm, preferably in the range from 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 Beam thickness is in the range of 5 microns to 35 microns, preferably in the range of 10 microns to 30 microns, especially preferably in the range of 15 microns to 30 microns, completely more preferably in the range of 20 microns to 27 microns.

Of the Sensor according to the invention is characterized that the beam width is transverse to the direction in which the inventive Sensor for scanning over the surface of a Subject is led.

With decreasing size of the laser beam cross section profile in the focal point, the signal-to-noise ratio increases since the intensity is distributed over a smaller area becomes. Empirically, it was found to be decreasing in size the laser beam cross-sectional profile in the focal point increasingly difficult is to achieve reproducible signals. Apparently this is Remember that the surface of the object to be authenticated no longer sufficiently accurate with respect to the diminishing Laser beam cross section profile can be positioned. Apparently It becomes increasingly difficult to re-authenticate the area to meet with sufficient accuracy.

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

Of the The sensor according to the invention optionally has Means for connecting multiple sensors or for connecting a Sensor with a holder. These funds can be at the Block or on a housing into which the block introduced be appropriate.

These Means allow two or more sensors in predetermined Way to connect with each other. Preferably, the block has or the case on one side over positive Connecting means and on the opposite side over negative connecting means, leaving a sensor on both sides of the block / housing with a holder and / or a another sensor can be connected in a defined manner, wherein the other sensors in turn on the still free sides with turn other sensors can be connected. This modular Principle allows the connection of a variety of sensors in a predefined way. As a positive connection means come for example Protrusions into recesses as negative Connecting means can be inserted. More One skilled in the art connection means such as Einführschienen or the like are conceivable. Several sensors are connected to each other, that the beam widths of all sensors are arranged along a line are.

The Connection of two or more sensors is reversible, d. H. it is solvable. The connecting means can also be used to the inventive Attach sensor to a bracket.

3 shows by way of example a preferred embodiment of a sensor according to the invention without laser 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 preferable equal.

The Amounts of the angles γ and δ are in Range from 5 ° to 90 °, preferably in the range 20 ° to 80 °, particularly preferably in the range 30 ° to 70 °, completely particularly 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 feedthroughs lie in one plane to form a compact one To allow design of the sensor.

The Use of a block with two to four feedthroughs for receiving a laser and one or more photodetectors offers the advantage that the optical components are simple though nevertheless be arranged in a defined manner to each other can. Preferably is in the implementation a stop for the laser. Against this attack will the laser of the sensor is pushed into the bushing, so that it has a predetermined fixed position with respect to the block and the photodetectors occupies. Does the laser already have this connected optical elements for beam shaping and focusing, which, for example, in the commercially available today Laser beam sources is common, so is due to the fixation of Lasers at the same time clearly the focus point of the laser. The others Feedthroughs for receiving photodetectors can also be provided with a stop, the position the photodetectors must be less accurate than the position of the Laser.

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, for example, the block of aluminum or to mill 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.

Of the Sensor can have a housing, in which the block is inserted. In the housing of the sensor are preferably introduced further components, for. B. the control electronics for the laser, signal preprocessing electronics, complete evaluation electronics and similar. The housing is preferably also the anchoring of a connecting cable with which the inventive Sensor with a control unit and / or a data acquisition unit for controlling the sensor and / or for detecting and processing the characteristic reflection pattern can be connected.

Of the Sensor can optionally have a window, placed in front, behind or in the outer surface is and the optical components from damage and Pollution protects. Preferably, the window forms the Outer surface of the sensor. The window is at least for the wavelength of the laser 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 simultaneously the focal point of the laser and lies at a distance of 2 to 10 mm from the outer surface.

to Scanning the surface of an article is the inventive Sensor accordingly at a distance above this object guided so that the focal point and intersection of the central axes lying on the surface of the object.

at the mentioned distance range of 2 to 10 mm is the positioning the surface of an object to be scanned the laser and the photodetectors simple and sufficiently accurate. With an increasing distance between sensor and object must the angle of the sensor to the surface of the object are increasingly accurately adhered to a predetermined Area of the surface to capture, so that the positioning requirements increase.

Farther takes the radiation intensity with increasing distance from the radiation source, so that at an increasing distance between the sensor and the object which accordingly reduced the object incoming radiation intensity due to a higher Power of the radiation source would have to be compensated. However, the sensor according to the invention is preferred equipped with a class 1 or 2 laser to the sensor to be able to operate without extensive protective measures. This is especially true since the sensor is "open" (i.e. H. the laser beam leaves the sensor unhindered). The means that the power of the radiation source is not arbitrary can be increased. In this respect, a short invention is according to the invention Distance advantageous.

Of the Sensor according to the invention can be in a Cost-effective mass production on an industrial scale finished, has a compact design, is intuitive and easy to handle, is flexible and can be used expandable and delivers reproducible and transferable Results.

1

surface

2

source for electromagnetic radiation

3

scanning beam

4

reflected beam

5

photodetector

6

line-shaped beam profile

7

sampled Area

10

block

11

first Implementation for receiving a radiation source

12

second Implementation 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 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

• - 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]

Cited non-patent literature

• - ISO 5627 [0003]
• - 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, Figure 2 [0025]
• - DIN EN ISO 4287: 1998 [0037]
• - DIN EN ISO 4287: 1998 [0038]
• 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. [0068]
• - DIN EN ISO 4287: 1998 [0093]
• - Standard DIN EN 60825-1 [0104]

Claims (14)

Method for generating a signature of an object at least comprising the following steps: A1: sampling a first portion of a surface of the article and receiving a scanning signal, the at least a part of the surface structure represented 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 the signature in a form in which it is for later Comparative purpose is available. Method of identification and / or authentication of an article at least comprising the following steps: B1: Scanning a second area of a surface of the object and receiving a scanning signal, the at least a part of the surface structure represented 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 a reference signature, B4: generation of a message via the identity and / or authenticity of the item depending on the result of the comparison in step B3. Method according to claim 2, characterized in that that the second area is smaller than the first area of claim 1 and is within this first range. Method according to claim 2, characterized in that that the second area is larger than the first area from claim 1, this first area is completely covered. Method according to claim 2, characterized in that that the second area identical or at least largely identical with the first area of claim 1. Method according to one of claims 1 to 5, characterized in that the scan is optically non-coherent Radiation takes place. Method according to one of claims 1 to 6, characterized in that for scanning the object and a device for scanning the article in a constant Distance apart are moved and the scan along a single Line done. Method according to claim 7, characterized in that that sampling with a linear beam profile takes place, the longer extension transverse to the direction of movement lies. Method according to claim 8, characterized that the beam width of the linear beam profile by a factor of more than 50 is greater than the beam thickness. Method according to claim 7 or 8, characterized that the beam thickness of the linear beam profile in Range of the mean groove width of the present surface lies. Sensor for scanning a surface, at least comprehensive A block with an outer surface, a first implementation, which at an angle γ in Reference to the normal of the outer surface on the outer surface and a second implementation, in an angle δ with respect to the normal of the outer surface on the outer surface, wherein the Amounts of the angles γ and δ are the same - one Laser, which is arranged in the first implementation and a laser beam towards the outer surface can send - optical elements for forming a linear beam profile, - a photodetector, which is arranged in the second passage and in the direction the outer surface is directed. Sensor according to claim 11, characterized in that that the beam width in the range of 3 mm to 6.5 mm, preferably in the range of 4 mm to 6 mm, more 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 is up to 27 microns. Sensor according to one of claims 11 or 12, characterized in that the amounts of the angles γ and δ in Range from 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 °. Sensor according to one of claims 11 to 13, further comprising two further feedthroughs for 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 °.