DE102020114980A1 - DEVICE AND SYSTEM FOR INSPECTING AT LEAST ONE DIFFACTIVE OPTICAL ELEMENT OF A DOCUMENT - Google Patents

Abstract

A device for inspecting at least one diffractive optical element, DOE, of a document has: a document carrier device for carrying a document to be inspected; a radiation source for coherent electromagnetic radiation; a deflection unit arranged on a first side of the document carrier device for deflecting radiation emitted by the radiation source onto the document carried by the document carrier device; a screen arranged on a side of the document carrier device opposite the first side for displaying an image projected onto the screen wall by means of transmissive diffractive interaction of the deflected radiation with a DOE provided on or in the document; an image sensor for sensing the image projected on the screen and for providing image data representing the captured image; and an evaluation device for evaluating the image data with regard to at least one inspection criterion. The deflection unit is configured to be adjustable relative to the document carrier device in such a way that, when the device is in operation, it moves the radiation emitted by the radiation source to a corresponding point on the one carried by the document carrier device, depending on the currently set position of the deflector unit inspecting document distracts.

Description

The present invention relates to a device for inspecting at least one diffractive optical element, DOE , a document, in particular a security document, and a document inspection system having such a device.

To increase the security against forgery of documents, in particular of so-called security documents, such as passports, identification cards and many other types of personalized chip cards, such as bank cards, credit cards, identification cards, membership cards, access authorization cards or banknotes or other documents of value, it is known to use such documents with a or to equip several security features. Such security features can be openly visible (“overt”) or concealed (“covered”) so that they can only be recognized or read by means of special equipment, for example under a UV lamp. In particular, optical security features can be used, i.e. security features which influence electromagnetic radiation, in particular in the visible range, the infrared range or the UV range of the electromagnetic spectrum, in any characteristic and detectable manner suitable for distinguishing from forgeries. Examples of such optical security features are holograms or luminescent substances, which show characteristic optical reactions with suitable optical excitation.

Diffractive optical elements (“DOE”) are optical elements for shaping, in particular beam shaping or beam splitting, an electromagnetic beam, often in the form of a laser beam, by means of optical diffraction (also called diffraction) on an optical grating. A well-known application of DOE is the counterfeit protection of plastic banknotes. A so-called “hyal” window is formed in such a bank note, which can be seen as a transparent field on the plastic bank note. The hyalic windows that for a DOE are provided, have an optically milky film. This visible film is a microstructure that can only be deciphered with a laser whose laser beam is projected through the microstructure onto a projection surface, on which a diffractive interaction of the laser beam with the microstructure of the DOE generated characteristic image becomes visible and can be used for the authenticity check.

While the authenticity check of banknotes is often carried out as an individual check of a single banknote or a small amount of banknotes, for example at a point of sale, one or more is used for the production of banknotes DOE The provided documents are generally about producing a large number of such documents in the shortest possible time and, within the framework of quality assurance, the quality of the documents produced in the process or applied to or introduced into the documents DOE to inspect.

In other cases it may also be necessary to inspect a large number of such documents “in the field”, in particular for authentication purposes. In addition, such a mass inspection can in turn be carried out for quality assurance purposes, for example in the context of a personalization following the actual document production and possibly carried out elsewhere, in particular of identification documents, on the basis of prefabricated document blanks DOE .

In addition, the form factor of such documents to be checked as well as the position of one or more DOE on or in such documents to be inspected depending on the document type or even vary individually.

The present invention is based on the object of providing devices or systems with which a high efficiency, in particular a high speed, in the inspection of diffractive optical elements ( DOE ) can be reached from different documents.

The solution to this problem is achieved in accordance with the teaching of the independent claims. Various embodiments and developments of the invention are the subject matter of the subclaims.

A first aspect of the invention relates to a device (hereinafter also referred to as "DOE inspection device") for inspecting at least one diffractive optical element, DOE , a document, in particular a security document. The apparatus comprises: (i) a document carrier device for carrying a with a DOE provided document to be inspected; (ii) a radiation source for coherent electromagnetic radiation, which in particular can be a source for laser light (laser); (iii) a deflection unit arranged on a first side of the document carrier device, in particular a mirror, for deflecting radiation emitted by the radiation source onto the document carried by the document carrier device; (iv) a screen arranged on a side of the document carrier device opposite the first side for displaying a transmissive, diffractive interaction (ie transmissive optical diffraction) of the deflected radiation with one provided on or in the document DOE image projected on the screen; (v) an image sensor for sensing the image projected on the screen and for providing image data representing the captured image; and (vi) an evaluation device for evaluating the image data with regard to at least one inspection criterion. The deflection unit is configured to be adjustable relative to the document carrier device in such a way that, when the device is in operation, it moves the radiation emitted by the radiation source to a corresponding point depending on the currently set position, ie position and / or orientation, of the deflection unit , in particular on a transparent or opaque (especially milky) window area that is permeable to radiation (e.g. a so-called "clear window") in which the DOE is formed, deflects on the document to be inspected carried by the document carrier device.

A “document carrier device” within the meaning of the invention is to be understood in particular as a device which is suitable and provided for carrying a document to be inspected, while holding it in position relative to the beam path of the electromagnetic radiation, and thus for transmissive screening of a document DOE of the document in the beam path.

A “screen” in the sense of the invention is to be understood as meaning, in particular, a device or a part thereof that has a projection surface that can in particular be flat or curved so that a transmissive diffractive interaction of coherent radiation with the DOE generated image can be displayed on the projection surface. "Transmissive" means here that that DOE is penetrated by the radiation, whereby, due to the diffractive interaction, the image projected onto the projection surface, viewed in the direction of radiation, is "behind" the DOE arises.

An “inspection criterion” within the meaning of the invention is to be understood in particular as a predetermined test specification according to which, when applied to the image projected on the screen during operation of the DOE inspection device, it can be checked and determined whether the image causing the image DOE (or the document provided with it) is an original or a forgery in the sense of a forgery check or whether it has an error-free state or at most errors within a predetermined tolerance range in the sense of a required minimum quality.

The terms “comprises,” “includes,” “includes,” “has,” “has,” “with,” or any other variant thereof, as used herein are intended to cover non-exclusive inclusion. For example, a method or apparatus that includes or has a list of elements is not necessarily limited to those elements, but may include other elements that are not expressly listed or that are inherent in such a method or apparatus.

Furthermore, unless expressly stated to the contrary, “or” refers to an inclusive or rather than an exclusive “or”. For example, a condition A or B is met by one of the following conditions: A is true (or present) and B is false (or absent), A is false (or absent) and B is true (or present), and both A and B are true (or present).

The terms “a” or “an”, as they may be used here, are defined in the sense of “one or more”. The terms “another” and “another” as well as every other variant thereof are to be understood in the sense of “at least one further”.

The term “plural”, as it may be used here, is to be understood in the sense of “two or more”.

With the aid of the device, due to the mobility of the deflection unit, a configuration can be made as to which point on a document to be inspected should come to lie in the beam path of the electromagnetic radiation if the document remains in the same position. The device can thus be configured for the inspection of a wide variety of documents, in particular documents that are different in terms of the position of theirs DOE differ from each other, or from documents, each of which is itself several to be inspected DOE in different places in the document. This is even during an inspection run in which such different documents or DOE should be inspected by document is possible. A sufficiently high configuration speed that enables this results in particular from the fact that only the position of the deflection unit has to be adjusted accordingly in terms of a configuration, while the other components of the device, at least with the exception of a transport device for feeding and removing the documents to be inspected can remain stationary. This also allows a correspondingly low complexity of the device, since no movement or movement for the stationary components Tilting devices or the like must be provided in order to enable the device to be configured for the stated purpose.

The device also needs, in addition to the deflection unit and the screen (and of course the one belonging to the document DOE ) no further optically imaging elements in the beam path, so that on the one hand the complexity of the optical imaging can remain low and on the other hand sharpness losses and other imaging errors can be kept low or even avoided.

In the following, preferred embodiments of the device are described which, unless this is expressly excluded or technically impossible, can be combined with one another as desired and with the other described aspects of the invention.

In some embodiments, the deflection unit is configured to execute a translational movement, a rotational movement or a combined translational-rotational movement relative to the document carrier device and independently of the projection screen in one or more spatial dimensions, in order to vary the location of the radiation emitted by the radiation source deflecting the document carried by the document carrier device. In this way, only the deflection unit itself has to be changed in its position with a corresponding movement in order to check a document to be inspected at different positions of a possibly present there DOE to be able to perform. Movement of other components, in particular the screen, the radiation source, the evaluation unit or the document carrier device, is not absolutely necessary for this purpose, although it is nevertheless possible as an option. In this way, on the one hand, the complexity of the device can be kept small or, on the other hand, if desired, a high degree of configurability can be made possible. In addition, above all, a high throughput of the device, ie a high inspection rate, can be achieved, especially if the deflection unit is designed with a low mass and thus also in the case of a strongly accelerated movement, as can occur at high throughput rates at different DOE positions, is only subject to low inertial forces.

In some embodiments, the device also has a signal-controlled drive device, the position of the deflection unit relative to the document carrier device being automatically adjustable by means of the drive device as a function of a position signal that indicates a position of a document to be inspected or of a window area (especially clear window). or DOE represented by it. The position signal can in particular be supplied by a position detection device which is set up to determine the position of the document to be inspected or of its or at least one of its DOE to be detected by sensors and to generate the position signal accordingly. In particular, a correction of the position of the deflection device depending on its position on the document carrier device can take place for each document in order to ensure correct placement of a DOE of the document in the beam path of the deflected radiation.

In some embodiments, the screen is or has a transmitted-light screen that is partially transparent to the radiation, in particular a matt screen. In addition, the image sensor is configured in such a way that it can use sensors to detect the transmitted-light image that occurs when the image is projected onto a front side of the transmitted-light screen on the rear side thereof. This enables in particular a simple arrangement of the image sensor, in which its optical axis can in particular run perpendicular to the transmitted light screen, so that no perspective image distortions occur and may first have to be compensated or otherwise taken into account in the context of the image evaluation.

In some alternative embodiments, on the other hand, the screen is or has a reflection screen and the image sensor is configured such that it can sensorically detect the image that is created when the image is projected onto a front side of the reflection screen by means of reflection on the reflection screen. This makes it possible, in particular, to design the device with a small form factor, since no device components are required that are arranged beyond the screen when viewed in the direction of projection, i.e. "behind" as seen in the direction of the incident radiation.

In some embodiments, the document carrier device has a transport device for transporting the document to be inspected, in particular for the sequential transport of a multiplicity of documents to be inspected in each case, into the beam path of the deflected radiation. According to some of these embodiments, the transport device has a vacuum transport belt for transporting the document to be inspected into the beam path of the deflected radiation. The use of a transport device allows documents to be inspected to be automatically fed in and removed from an inspection area of the device defined by the beam path. In particular, the solution with a conveyor belt also enables a high throughput for the mass inspection of a large number of documents or DOEs.

In some embodiments, the device furthermore has a position detection device for the sensoric detection of a current position of the document, a window area thereof or its DOE itself and for triggering the image sensor, the radiation source or both as a function of this detected position in order to achieve an image sensoric detection of the to effect projected image on the screen when the or a respective DOE of the document is in the path of the deflected radiation. This ensures that the image sensor captures the projected image at the right time and thus a reliable inspection result can be obtained even if the document or DOE moves, especially at high speed or if it only stops for a short period of time in the beam path of the deflected radiation for the purpose of inspection and remains before it is moved out of the beam path again. The position detection device can expediently in particular be the same as that already described above in connection with the generation of a position signal. The device can in particular be designed in such a way that it can be configured to provide both a slower throughput (e.g. 2,000 units (documents) per hour, UPH) and a higher, in particular much higher, throughput (e.g. 30,000 UPH) accomplish. It is also possible to achieve a much higher throughput. The triggering can affect the image sensor, the radiation source or both. In the event that it only affects the image sensor or only the radiation source, the respective other component, i.e. the radiation source or the image sensor, can in particular be in continuous operation, so that no position-dependent triggering is required for this.

In the embodiments with a position detection device, this can be configured to be configurable, in particular programmable, in order to adapt to the type and location of a window area or a DOE or multiple DOEs on or in the document.

In some embodiments, the device furthermore has a speckle reduction device for reducing speckles when imaging the coherent radiation from the radiation source onto the screen. As is customary in laser technology, “speckies” are to be understood as grainy interference phenomena that can be observed with sufficiently coherent illumination of optically rough object surfaces (unevenness in the order of magnitude of the wavelength). In these embodiments, the image quality and, based thereon, the accuracy and reliability of the inspection of the DOEs can be increased, since image disturbances caused by speckle can be reduced or even avoided, which could otherwise lead to incorrect image evaluations. Particularly suitable as speckle reduction devices are devices that use one or more of the following methods for the purpose of speckle reduction, in particular with regard to laser light: (i) illumination from different angles (angle diversity), (ii) use of different optical polarizations (polarization diversity); Use of laser sources whose wavelengths differ only slightly (wavelength diversity). Speckle reduction devices can in particular be integrated into the radiation source or arranged separately therefrom, in particular in the beam path of the radiation source.

In some embodiments, the evaluation device is configured to use the image data to identify at least one virtual object imaged on the screen or to detect a dimension, a line width or an angle or another characteristic in the image and in each case with the at least one inspection criterion to be adjusted in order to determine an inspection result depending on it. The inspection criterion can consequently be defined in particular by an approved line width range, certain object criteria, in particular dimensional ranges or angle ranges for certain dimensions or angles or other characteristics of a virtual object. This allows a variety of different inspection criteria to be defined and used as test criteria, which on the one hand allows the use of a large variety of different DOEs and on the other hand the achievable security level of the document protection by means of DOE increased, as not only different DOE can be used, but it is also made more difficult for a potential attacker to find out which inspection criteria will be used during the inspection in the field, to which an attempt at forgery would have to be aimed.

In some embodiments, the projection screen has a laminate of a plurality of stacked, transparent laminating films that are resistant to diffracted radiation and a film that closes off the stack on one side and is semitransparent and resistant to diffracted radiation. By means of this stacking concept, it is possible to configure the screen flexibly depending on the specific application and design of the device, in particular with regard to the thickness of the screen and its optical imaging properties, and in particular when manufacturing it on starting products that are readily available on the market and easy to manufacture, in particular laminating foils, to be able to fall back if custom-made products would otherwise be required. the Semitransparent film in particular takes on a role as at least the main image area of the stack.

In some of these embodiments, the projection screen is oriented in such a way that the film which closes off the stack on one side and is semitransparent and resistant to the diffracted radiation faces the image sensor. In this way, the image that can be captured by the image sensor is captured with maximum clarity, since no further stacked layers come to lie in the beam path between this film, on which the image is mainly created, and the image sensor.

• (i) Aufnehmen eines mit einem DOE versehenen zu inspizierenden Dokuments (D) durch eine Dokumententrägereinrichtung zum Tragen des Dokuments; (ii) Bestrahlen des Dokuments mit kohärenter elektromagnetischen Strahlung einer Strahlungsquelle für kohärente Strahlung, insbesondere eines Lasers, wobei die Strahlung auf eine auf einer ersten Seite der Dokumententrägereinrichtung angeordnete Ablenkeinheit gestrahlt wird, durch welche die Strahlung auf das durch die Dokumententrägereinrichtung getragene Dokument abgelenkt wird und als abgelenkte Strahlung das Dokument durchstrahlt, und wobei auf einer der ersten Seite gegenüberliegenden Seite der Dokumententrägereinrichtung angeordneten Bildwand ein darauf projiziertes Bild dargestellt wird, dass sich durch transmissive diffraktive Wechselwirkung der abgelenkten Strahlung mit einem auf oder in dem Dokumentvorgesehenen DOE ergibt;
• (iii) bildsensorisches Erfassen des auf die Bildwand projizierten Bilds und Bereitstellen von das erfasste Bild repräsentierenden Bilddaten; und (iv) Auswerten der Bilddaten im Hinblick auf zumindest ein Inspektionskriterium; wobei (v) die Lage der relativ zu der Dokumententrägereinrichtung beweglich konfigurierten Ablenkeinheit derart eingestellt wird, dass sie die von der Strahlungsquelle ausgesandte Strahlung auf das DOE des von der Dokumententrägereinrichtung getragenen, zu inspizierenden Dokuments ablenkt.

A second aspect of the invention relates to a method for inspecting at least one diffractive optical element, DOE , a document, the method comprising:

• (i) Record one with a DOE provided document to be inspected ( D. ) by a document carrier device for carrying the document; (ii) irradiating the document with coherent electromagnetic radiation from a radiation source for coherent radiation, in particular a laser, the radiation being radiated onto a deflection unit arranged on a first side of the document carrier device, by means of which the radiation is deflected onto the document carried by the document carrier device and the document shines through as deflected radiation, and an image projected thereon is displayed on a side of the document carrier device arranged opposite the first side, which image is created by transmissive, diffractive interaction of the deflected radiation with something provided on or in the document DOE results;
• (iii) image sensor acquisition of the image projected onto the screen and provision of image data representing the acquired image; and (iv) evaluating the image data with regard to at least one inspection criterion; wherein (v) the position of the deflection unit configured to be movable relative to the document carrier device is set in such a way that it directs the radiation emitted by the radiation source onto the DOE deflects the document to be inspected carried by the document carrier device.

The method corresponds to the device according to the first aspect, so that what was said there, in particular also with regard to the various embodiments, also applies here accordingly and is therefore not specifically mentioned again here in order to avoid repetition.

A third aspect relates to a document inspection system, having a plurality of modules for the sequential inspection of at least one predetermined property of a document each, with one of the modules being a device according to one of the preceding claims for inspecting at least one diffractive optical element, DOE , of the document. The document inspection system thus enables a wide variety of document inspection methods to be combined within a single system, with the modular design, in particular, enabling a high degree of configurability of the system and individual maintenance or repair of the various modules. In addition to inspection modules, the document inspection system can also have one or more further modules, in particular for handling the documents, such as when loading, turning or outputting and sorting the same as part of the processing by the system. The relative position of the various modules to one another, in particular the order in which the documents pass through the modules, can be configured to be configurable. Depending on the type of documents to be inspected, more or fewer modules, in particular more or fewer different inspection modules, can also be provided in the system, depending on the respective configuration.

According to some embodiments, the document inspection system is set up to inspect the document with regard to its front side and its rear side, the sequence of the modules according to which the document passes through the various modules during its inspection is defined such that: (i) either an inspection first the front side is carried out by appropriately assigned one or more of the modules, then the DOE inspection is carried out by means of the module with a device according to the first aspect of the invention, and then an inspection of the back of the document is carried out by appropriately assigned one or more of the modules; or (ii) in reverse order first the inspection of the back of the document, then the DOE inspection and finally the inspection of the front side of the document.

This represents an optimized solution insofar as the DOE inspection, which is based on a radiography of the DOE of a document is based and can thus inherently affect the front and back of the document, is carried out at a point in the overall process flow, at which the document can expediently be turned over from one of the two sides before or after the DOE inspection subsequently to be able to inspect the second side which has not yet been inspected at this point in time of the process. So if a DOE inspection is also to be carried out in the opposite direction, the same thing or a different one DOE of the document now is penetrated in the opposite direction of the beam with respect to the document than in the previous DOE inspection of the document, this structure of the system enables the two DOE inspections to be carried out at the same point in the process flow, in particular only by turning the document over from one another separated. Accordingly, a transport step between these two DOE inspections can be omitted.

According to some embodiments, the document inspection system further comprises: (i) a sensor device for detecting a position of a document to be inspected on a document carrier device and for generating a position signal representing this position; and (ii) a device according to the first aspect which is configured to receive the position signal and to control the drive device of the device as a function thereof in order to automatically adjust the position of the deflection unit as a function of the received position signal. In particular, a correction of the position of the deflection device depending on its position on the document carrier device can take place for each document in order to ensure correct placement of a DOE of the document in the beam path of the deflected radiation. The sensor device can in particular be given by the aforementioned position detection device of the DOE inspection device itself, or it can be formed separately from it or provided instead. As a rule, it will be sufficient to provide such a sensor device or position detection device as a whole, although solutions with several such sensors are also possible.

According to some of these embodiments, the sensor device can in particular be arranged in an upstream module of the document inspection system according to the first aspect with respect to a sequential inspection process of the device that can be carried out by the document inspection system using several of the modules. In this way, the position of the document can be detected by sensors at an early stage and also usable for other modules upstream of the DOE inspection device and, based on this, an adaptation or configuration of these modules and the DOE inspection device as a function of the the position signal representing the position take place. This can be used to increase the efficiency and reliability of the system, in particular because the position signal can be used for several modules, and thus individual position determinations per module are or will be obsolete.

Further advantages, features and possible applications of the present invention emerge from the following detailed description in connection with the figures.

• 1 schematisch eine Vorrichtung zur Inspektion von DOEs gemäß einer ersten beispielhaften Ausführungsform der DOE-Inspektionsvorrichtung mit Durchlichtbildwand;
• 2 schematisch eine Vorrichtung zur Inspektion von DOEs gemäß einer zweiten beispielhaften Ausführungsform der DOE-Inspektionsvorrichtung mit Reflektionsbildwand;
• 3 schematisch eine beispielhafte Antriebseinrichtung zur Bewegung der Ablenkeinheit der DOE-Inspektionsvorrichtung aus 1 oder 2;
• 4 eine beispielhaftes, bei der Inspektion eines entsprechenden DOE mittels einer der Vorrichtungen aus 1 oder 2 auf der jeweils zugehörigen Bildwand entstehendes Bild, auf dessen Basis eine Auswertung zum Zwecke der Inspektion erfolgen kann;
• 5 eine schematische Darstellung eines Stapelaufbaus einer Bildwand der Vorrichtung gemäß einer beispielhaften Ausführungsform der Erfindung; und
• 6 eine schematische Darstellung der Struktur eines multi-modularen Systems zur Inspektion von Dokumenten gemäß einer beispielhaften Ausführungsform der Erfindung.

It shows:

• 1 schematically, a device for inspecting DOEs according to a first exemplary embodiment of the DOE inspection device with a transmitted light screen;
• 2 schematically, a device for inspecting DOEs according to a second exemplary embodiment of the DOE inspection device with a reflection screen;
• 3 schematically shows an exemplary drive device for moving the deflection unit of the DOE inspection device 1 or 2 ;
• 4th an exemplary one when inspecting a corresponding DOE by means of one of the devices 1 or 2 Image created on the respective associated screen, on the basis of which an evaluation for the purpose of inspection can be carried out;
• 5 a schematic representation of a stack structure of a screen of the device according to an exemplary embodiment of the invention; and
• 6th a schematic representation of the structure of a multi-modular system for the inspection of documents according to an exemplary embodiment of the invention.

In the figures, the same reference symbols are used throughout for the same or corresponding elements of the invention.

In the 1 illustrated device 100 for the inspection of DOEs according to a first exemplary embodiment, a document carrier device 110 in the form of a conveyor belt, which can in particular be designed as a vacuum conveyor belt. The document carrier device 110 is used to document a document to be inspected D. , in particular a security document, or a plurality of such documents sequentially, into an inspection area of the device 100 to transport and to transport from there after the inspection, in particular to a possibly subsequent further inspection module of a higher-level document inspection system, for example a system according to 5 . At the device 100 the inspection area is defined by a space on which the conveyor belt 110 Is guided over pulleys that along the movement path of the document D. at this point one of the document Bridgeable support gap is created so that the conveyor belt 110 facing side of the document D. becomes freely accessible in the area of the gap and thus can be inspected through the gap.

The device 100 also has a radiation source 120 for coherent electromagnetic radiation L1 on. The radiation source 120 can in particular be a laser, the coherent radiation L1 emits in the ultraviolet, visible and / or infrared range of the electromagnetic spectrum and on a deflection unit 130 the device 100 directs. The radiation source preferably has 120 itself, especially in the case of a laser, a speckle reduction device 120a which is suitable and intended to prevent any occurrence of speckles in due to the radiation L1 to reduce or even avoid generated images.

The deflection unit 130 In particular, a mirror can be used to deflect the radiation L1 being. It is located in one through the deflection of the conveyor belt 110 defined cavity is adjacent to said gap, and it is configured to emit radiation L1 through the gap as deflected radiation L2 to a document that may bridge the gap D. distract. If doing the rejected radiation L2 on a diffractive optical element DOE of the document D. hits it during the fluoroscopic examination of the DOE optically bent by this and leaves the DOE as diffracted radiation L3 towards a front of a semi-transparent screen 140 . The screen 140 serves as a projection surface for the diffracted radiation L3 so that there is a projected image B. arises, whose properties are due in particular to the diffraction effect of the DOE are defined.

In addition, the device 100 an image sensor 150 on, which can in particular be a camera, preferably a digital camera. The image sensor 150 is designed and configured from the back of the semi-transparent screen opposite the front 140 her on it from the front of the screen 140 through the radiation L3 capture the projected image by image sensors and generate corresponding image data characterizing the captured image. The device 100 also has an evaluation device 160 to which the image data is transmitted and there with regard to an authenticity or forgery check or quality check with regard to the x-rayed DOE can be evaluated on the basis of at least one defined inspection criterion, as will be described below with reference to 4th will be explained.

The device 100 can also have a position detection device 170 have, for the sensory detection of a current position of the document D. , a window area (e.g. Clear Window) thereof or its DOE itself is set up. It can also use the image sensor as a function of this recorded position 150 trigger or activate, for example immediately or - as in 1 shown - indirectly via the evaluation unit 160 for image sensor detection of the on the screen 140 projected image B. to effect, to effect at the time when the respective DOE of the document D. in the beam path of the deflected radiation L2 is located.

In the 2 illustrated second embodiment 200 a device for inspecting DOEs essentially corresponds to the device 100 out 1 , but with the exception that here instead of the semi-transparent screen 140 , an essentially reflective screen 190 comes into use, whereby the diffracted radiation L3 on the screen 190 reflected and arranged by the image sensor suitable for detecting the reflected radiation 150 can be captured. This design is particularly suitable when small form factors are required or desired, since no additional installation space is required beyond the position of the screen.

Incidentally, according to a variant of this embodiment (not shown), it is also possible for the deflected radiation to first hit the reflective screen instead, without it hitting the document beforehand 190 to direct where it reflects and on that DOE is reflected in the document, so that the optically diffractive effect of the DOE occurs. The resulting diffracted radiation can then be detected by image sensors and evaluated accordingly.

3 schematically illustrates an exemplary drive device 300 to move the deflection unit 130 . Both can, in particular, be part of the respective device 1 or 2 being. The drive device 300 has an axis of rotation 310 on which the deflection unit 130 , in particular a mirror, is attached. The the axis of rotation 310 is in a rack 320 rotatably mounted and can be controlled by a rotary actuator 340 , for example a stepper motor with or without a gearbox, can be rotated around its axis of symmetry. Overall, an orientation (angle α) of the deflection unit can thus be achieved 130 by means of a rotary movement of the axis of rotation 310 set variably. The drive device 300 also has a cross table 330 on which the rack 320 is mounted so that this can be done using the cross table 330 can be moved translationally along two, preferably horizontal, spatial dimensions X and Y, which are via corresponding drives 330a or. 330b feature.

In addition, the drive device has 300 via a control unit 350 that is configured to both the actuator 340 as well as the drives 330a and 330b of the cross table by means of corresponding control signals 360 , 370 or. 380 to control in order to thereby the position, ie the XY position and orientation (angle α) of the deflection unit 130 to be able to adjust. For the sake of simplicity, it is also possible to dispense with up to two of these movement dimensions (X, Y, α), which, however, results in less configurability of the DOE inspection device with regard to the position of a window area or DOE on a document to be inspected.

To the control signals 360 , 370 and 380 to generate is the control unit 350 set up when adjusting the position of the deflection unit 130 a position signal received from it 180 (generated by the DOE inspection device itself) or 180a (generated outside the DOE inspection device) to evaluate the sensor-detected position of a on the document carrier device 110 transported document D. , a window area of it or already one to be inspected DOE represented by it. So can the optimal setting of the position of the deflection unit 130 depending on the detected position of the document, the window area or, in particular, that to be inspected DOE on the document D. take place, whereby in particular any tolerances with regard to the exact position of the document D. , the window area or the DOE or of different arrangements of DOEs on documents to be processed sequentially one after the other D. or even from several window areas and / or DOEs per document D. can be taken into account. The one by the position signal 180 or 180a represented position of the respective document, window area or DOE can in particular with regard to a through the device 100 or. 200 , the drive device 300 or in the case of a far window area or DOE - through the document D. self-defined reference point or coordinate system. If only the position of the document or window area is detected, the device can be configured on the basis of a relative position of the known from corresponding information DOE on or in the document from the position of the document to the position of the DOE close.

4th illustrates an exemplary picture B. as it is on the screen 140 when using a corresponding DOE and that a perspective view of an object 410 shows in the form of a cube in line or framework representation. When the projected image B. as here represents a defined virtual object, then the inspection criterion can be defined in particular with respect to one or more dimensions of the virtual object, for example in the form of specific values for these dimensions including associated tolerance ranges. Are then in the context of an image evaluation of the image B. by the evaluation device 160 the corresponding dimensions in the picture B. determined and if these fall within the tolerance ranges, this will be DOE classified as genuine or faultless, otherwise as fake or faulty. Instead of or in addition to dimensions, other inspection criteria can also be used, for example line widths, object types or shapes (for example cubes or pyramids) or certain angles or other characteristics of the virtual object.

As part of the image evaluation, in 4th several rectangular image areas have been defined and marked, each enclosing an edge or line of the cube structure, so that the corresponding line width can be determined within these image areas and compared with the inspection criterion. There was also an angle 430 identified which corresponds to a tilting of the virtual cube with respect to the vertical, so that this can also be compared with a corresponding inspection criterion in the course of the evaluation. For example, this can DOE the picture B. generated, classified as genuine or error-free, if a virtual object 410 is recognized in the form of a cube shown in perspective, its in the image areas 420 recognized lines have a line width within a predetermined line width range, and at which the angle which is also recognized 430 lies within a predetermined angular range. In total, at least three inspection criteria can be used cumulatively in this example.

One in 5 shown exemplary semi-transparent screen 140 is built up as a stack of several layers. This stack has, in particular, a plurality of the radiation used by the radiation source 120 At least largely transparent laminating foils 505 to 545 which are resistant (with regard to material changes) (in the present example these are nine laminating foils each 100 μm thick). On one side the stack is covered by an additional layer, which is a semi-transparent film 550 , in particular a matt film, is completed. All layers of the stack are laminated with the respective adjacent layers and thus form a laminate as a whole. The semi-transparent film 550 is preferably arranged so that it is the image sensor 150 is facing. If now, as in 1 illustrates the diffracted radiation L3 on the dem DOE closest lamination film 505 to the screen 140 hits, it first traverses the partial stack of transparent laminating foils 505 to 545 until it hits the semi-transparent foil 550 meets and there the picture B. generated as an image (see for example 4th ). As the slide 550 the radiation hitting it partially lets pass, is this picture B. also from the one beyond the slide 550 lying outside of the stack visible and can therefore be from the image sensor 150 are recorded.

With the help of this stack structure it is possible to build the projection screen 140 can be configured individually, in particular with regard to their strength and optical properties, depending on the application. In particular, it is also possible for one or more of the foils 505 to 550 to have an additional imaging function, in particular a filter function, for example to prevent laterally incident interference radiation that is not from the radiation source 120 originates to filter out.

Optionally, on at least one layer within a stack-like or laminate-like structure of the document D. , in particular on one or both surfaces and / or one or more inner layers of the document D. , further, visible security elements, e.g. characters, text or images, congruent or overlapping with the DOE or a that DOE containing pane of the document D. be present, in particular in the form of a suitable print or a laser engraving, which is sufficiently transparent for the deflected radiation, so that the DOE through these additional security features with regard to the radiation remains “visible” and this remains after its diffraction on DOE as diffracted radiation L3 is projected onto the screen.

6th finally shows a schematic representation of the structure of an exemplary multi-modular document inspection system 600 for inspection of documents D. . The document inspection system 600 has a plurality of modules connected one after the other to carry out a sequential inspection process 601 until 620 on, which are provided as part of a with the system 600 executable inspection process a document D. or sequentially a large number of documents to be processed one after the other D. to inspect with regard to various aspects. In particular, is the document inspection system 600 designed to be documents D. , especially card-shaped documents, to be inspected on both sides.

Accordingly, the document inspection system 600 a first process line 630 to inspect a respective front page of the documents D. on. The first line of the process 630 has one or more of the following modules, preferably in the following order: a document feed module (feeder) 601 , a module 602 for laser engraving testing 602 , a module for document alignment and cleaning of the document front 603 , a module for the inspection of a particularly transparent document joint (for book-like documents such as passports), a module 605 for surface inspection of the front of the document, one module 606 for the inspection of printing on the front of the document, a module 607 for inspecting microtext on the front of the document and for carrying out a test of an electronic chip (in particular an RFID chip) that may be present in the document, a module 608 for UV inspection of the document front as well as a module 609 for the inspection of one or more holograms on the front of the document.

After the first process line 630 a module follows 610 for DOE inspection, which is a DOE inspection device, in particular a device 100 according to 1 or a device 200 according to 2 may have. Since the DOE inspection involves an X-raying of the document, more precisely his DOE , takes place, this module is not necessarily assigned to a document-page-specific process line. In the in 6th shown variant of the system 600 is a part of the module 610 preceding module, here for example the immediately preceding module 609 , with a sensor device 609a (in particular position detection device) for detecting the position of a document D. on the document carrier device 110 or a pane or DOE of the document. By means of this sensor device, a position signal 180a can be generated which shows the position of the document D. , the window area or the DOE represents and to the control unit 350 the drive device 300 is transmitted (cf. 3 ). If only the position of the document or window area is detected, the device can be configured on the basis of a relative position of the known from corresponding information DOE on or in the document from the position of the document to the position of the DOE close.

Before then a second process line 640 for the inspection of the back of the document follows, there is another module in the module sequence 611 intended for turning the documents so that the inspection of the back of the documents from the same side of the system 600 here, for example from above, can be done.

The process line 640 has one or more of the following modules, preferably in the following order: a module 612 for document alignment and cleaning the back of the document, a module 613 for surface inspection of the back of the document, a module 614 for inspecting a print on the back of a document, a module 615 for UV inspection of the Document back, a module 616 for hologram inspection of the back of the document, one module 617 for the inspection of microtext on the back of a document, one module 618 for marking scrap documents, a module 619 for key rotation, ie for exchanging or changing a key or code to restrict access to an electronic chip of the document that may be present, and finally an output module 620 , optionally with a sorting function for the inspected documents, in particular for sorting into error-free or genuine documents on the one hand and incorrect or falsified documents on the other.

While at least one exemplary embodiment has been described above, it should be understood that a large number of variations exist therefor. It should also be noted that the exemplary embodiments described represent only non-limiting examples, and it is not intended to restrict the scope, applicability or configuration of the devices and methods described here. Rather, the preceding description will provide the person skilled in the art with instructions for implementing at least one exemplary embodiment, it being understood that various changes in the mode of operation and the arrangement of the elements described in an exemplary embodiment can be made without departing from the claims in the appended claims the subject matter specified in each case and its legal equivalents are deviated from.

List of reference symbols

100

Device for DOE inspection, first embodiment

110

Document carrier device, in particular transport device

120

Radiation source for coherent electromagnetic radiation, in particular laser

120a

Speckle reduction device, here integrated in the radiation source

130

Deflection unit, especially a mirror

140

Screen, in particular semi-transparent screen

150

Image sensor, especially camera

160

Evaluation device

170

Position detection device

180

Position signal

190

Screen, especially reflective screen

200

Device for DOE inspection, second embodiment

300

Drive device for deflection unit

310

Axis of rotation

320

Frame, bearing for axis of rotation

330

Cross table

330a

first drive (X direction) of the cross table

330b

second drive (Y-direction) of the cross table

340

Actuator or drive for mirror rotation

350

Control unit

360

Control signal for the first drive of the cross table

370

Control signal for the second drive of the cross table

380

Control signal for actuator 340

400

Picture on screen

410

virtual object in image 400

420

Lines of the object

430

Orientation angle of the object

500

Image sensor arrangement relative to a screen constructed as a laminate

505-545

transparent laminating foils

550

semi-transparent film, especially matt film

600

Document inspection system for document inspection

601

Document feed module (feeder)

602

Module for laser engraving testing

603

Module for document alignment and cleaning of the document front

604

Module for the inspection of a particularly transparent document hinge

605

Module for surface inspection of the document front

606

Module for the inspection of printing on the front of the document

607

Module for the inspection of microtext with regard to the front of the document and for the chip test

608

Module for UV inspection of the document front

609

Module for the hologram inspection of the document front

609a

Sensor device (in particular position detection device)

610

Module or device for DOE inspection

611

Module for turning the document

612

Module for document alignment and cleaning of the back of the document

613

Module for surface inspection of the back of the document

614

Module for the inspection of printing on the back of the document

615

Module for UV inspection of the back of the document

616

Module for hologram inspection of the back of the document

617

Module for the inspection of microtext on the back of a document

618

Module for marking scrap documents

619

Key rotation module

620

Output module with sorting function

630

Process line for document front inspection

640

Process line for document back inspection

B.

Image displayed on the screen

D.

Document, especially security document

DOE

diffractive optical element, DOE

L1

incident radiation

L2

deflected radiation

L3

diffracted radiation

Claims (18)

Device (100; 200) for inspecting at least one diffractive optical element, DOE, of a document (D), the device (100; 200) having: a document carrier device (110) for carrying a document to be inspected (D) provided with a DOE; a radiation source (120) for coherent electromagnetic radiation; a deflection unit (130) arranged on a first side of the document carrier device (110) for deflecting radiation (L1) emitted by the radiation source (120) onto the document (D) carried by the document carrier device (110); a screen (140; 190) arranged on a side of the document carrier device (110) opposite the first side for displaying a DOE provided on or in the document (D) on the screen (140) by means of a transmissive diffractive interaction of the deflected radiation (L2) with a DOE provided on or in the document (D) ; 190) projected image (B); an image sensor (150) for sensory detection of the image (B) projected on the screen (140; 190) and for providing image data representing the detected image (B); and an evaluation device (160) for evaluating the image data with regard to at least one inspection criterion; wherein the deflection unit (130) is configured to be movable relative to the document carrier device (110) in an adjustable manner in such a way that, when the device (100; 200) is in operation, the radiation (L1) emitted by the radiation source (120) is variable depending on the momentary The set position of the deflection unit (130) deflects to a corresponding point on the document (D) to be inspected and carried by the document carrier device (110). Device (100; 200) according to Claim 1 , wherein the deflection unit (130) is configured relative to the document carrier device (110) and independently of the screen (140; 190) in one or more spatial dimensions (X, Y; α) a translational movement, a rotary movement, or a combined perform a translatory-rotary movement in order to deflect the radiation (L1) emitted by the radiation source (120) in a locally variable manner onto the document (D) carried by the document carrier device (110). Device (100; 200) according to one of the preceding claims, further comprising a signal-controlled drive device, the position of the deflection unit (130) relative to the document carrier device (110) being automatically adjustable by means of the drive device (300) as a function of a position signal (180) which represents a layer of a document to be inspected (D) or a window area or DOE thereof. Device (100; 200) according to one of the preceding claims, wherein the projection screen is or has a transmitted light projection screen (140) which is partially transparent to the radiation and the image sensor (150) is configured such that it does this when the image is projected (B) on a front side of the transparency screen (140; 190) on the rear side of the transparency image (B) produced by sensors. Device (100; 200) according to one of the Claims 1 until 3 , wherein the screen is or has a reflection screen (190) and the image sensor (150) is configured such that it results from the projection of the image (B) onto a front side of the reflection screen (190) by means of reflection on the reflection screen (190) Image (B) can detect by sensors. Device (100; 200) according to one of the preceding claims, wherein the document carrier device (110) has a transport device for transporting the document (D) to be inspected into the beam path of the deflected radiation (L2). Device (100; 200) according to Claim 6 wherein the transport device (110) has a vacuum transport belt for transporting the document to be inspected (D) into the beam path of the deflected radiation (L2) Device (100; 200) according to one of the preceding claims, further comprising a position detection device (170) for sensory detection of a current position of the document (D), a window area thereof or its DOE itself and for triggering the image sensor (150), the radiation source or of both as a function of this detected position in order to effect image sensor detection of the image (B) projected onto the screen (140; 190) when the respective DOE of the document (D) is in the beam path of the deflected radiation ( L2) is located. Device (100; 200) according to Claim 8 wherein the position detection device (170) is configured to be configurable in order to enable adaptation to the type and position of a window area or a DOE or several DOEs on or in the document (D). Device (100; 200) according to one of the preceding claims, further comprising a speckle reduction device (120a) for reducing speckles when imaging the coherent radiation from the radiation source (120) onto the screen (140; 190). Device (100; 200) according to one of the preceding claims, wherein the evaluation device (160) is configured to identify at least one virtual object (410) mapped onto the screen (140; 190) or a dimension, to detect a line width (410) or an angle (430) in the image (B) and to compare it with the at least one inspection criterion in order to determine an inspection result as a function thereof. Device (100; 200) according to one of the preceding claims, wherein the projection screen (140) is a laminate of a plurality of stacked on top of one another with respect to the diffracted radiation (L3) resistant and transparent laminating foils (505 to 545) and one that closes off the stack on one side and faces the having diffracted radiation resistant and semitransparent film (550). Device (100; 200) according to Claim 12 wherein the screen (140; 190) is oriented such that the semi-transparent film (550) which closes the stack on one side and is resistant to the diffracted radiation (L3) faces the image sensor (150). A method for inspecting at least one diffractive optical element, DOE, of a document (D), the method comprising: Receiving a document (D) provided with a DOE to be inspected by a document carrier device (110) for carrying the document; Irradiating the document (D) with coherent electromagnetic radiation (L1) from a radiation source (120) for coherent radiation, the radiation being radiated onto a deflection unit (130) arranged on a first side of the document carrier device (110) through which the radiation (L1 ) is deflected onto the document (D) carried by the document carrier device (110) and shines through the document as deflected radiation (L2), and an image (B) projected thereon is displayed on a side of the document carrier device (110) opposite the first side, which image (B) is projected thereon, which due to the transmissive diffractive interaction of the deflected radiation (L2) with one on or in the document (D) provided DOE results; image-sensory acquisition of the image (B) projected onto the screen (140; 190) and provision of image data representing the acquired image (B); and Evaluating the image data with regard to at least one inspection criterion; wherein the position of the deflection unit (130) configured to be movable relative to the document carrier device (110) is set in such a way that it directs the radiation (L1) emitted by the radiation source (120) onto the DOE of the document to be inspected carried by the document carrier device (110) (D) distracts. Document inspection system (600), comprising a plurality of modules (601 to 620) for sequential inspection of at least one predetermined property of a document (D), one of the modules (610) having a device (100; 200) according to one of the Claims 1 until 13th for the inspection of at least one diffractive optical element, DOE, of the document (D). Document inspection system (600) according to Claim 15 , wherein the document inspection system (600) is set up to inspect the document (D) with regard to its front side and its rear side, the sequence of the modules (601 to 620) according to which the document (D) passes through the various modules during its inspection, is set in such a way that: either an inspection of the front side is carried out first by appropriately assigned one or more of the modules (601 to 609), then the DOE inspection by means of the module (610) with a device (100; 200) according to one of the Claims 1 until 13th takes place, and then an inspection of the rear side of the document (D) is carried out by appropriately assigned one or more of the modules (612 to 620); or in the reverse order first the inspection of the back of the document (D), then the DOE inspection and finally the inspection of the front of the document (D). Document inspection system (600) according to Claim 15 or 16 , comprising: a sensor device (609a) for detecting a position of a document to be inspected (D) on a document carrier device (110) or a window area or a DOE of the document (D) and for generating a position signal (180a) representing this position; and a device (100; 200) according to Claim 3 which is configured to receive the position signal (180a) and to control the drive device (300) as a function thereof in order to automatically set the position of the deflection unit (130) as a function of the received position signal (180a). Document inspection system (600) according to Claim 17 wherein the sensor device (609a) in a sequential inspection process of the device (100; 200) that can be carried out by the document inspection system (600) using a plurality of the modules Claim 3 upstream module (609) of the document inspection system (600) is arranged.

Images