DEVICE AND METHOD FOR TESTING AT LEAST ONE SAFETY ELEMENT OF A SAFETY DOCUMENT

Description

[0001] The invention relates to a device and a method for checking at least one security element of a security document.

[0002] Security documents typically contain multiple security elements, and the authenticity of the security document can be verified based on predetermined properties of these security elements. Common security elements include holograms, watermarks, and security threads.

[0003] When producing security documents with security features, it is necessary to manufacture the security document with the security features in such a way that the security elements exhibit the predetermined properties explained above, in order to subsequently enable reliable verification of authenticity. However, due to undesirable influences during production, the actual properties of a security element may deviate from the predetermined properties. Such a security document would then be classified as counterfeit due to these production errors.

[0004] Of course, the testing of security elements also plays a major role in verifying authenticity, for example, in commercial transactions, i.e., after production. For example, counterfeits may contain security elements that do not fully or completely fulfill the desired properties. It is desirable to be able to reliably identify such counterfeit security documents.

[0005] DE 10 2012 211 076.3 (not yet published) discloses a device for document capture, wherein the device comprises at least one image capture device. Furthermore, a transillumination device is disclosed, wherein the at least one image capture device and the at least one transillumination device are arranged relative to one another in such a way that the at least one image capture device can detect light that is radiated by the at least one transillumination device through the support surface.

[0006] DE 10 2012 219 905.5 (not yet published) discloses a method for checking a security element of a security document. At least a first partial area of ​​the security element is illuminated with white light radiation at a first angle of incidence and with white light radiation at a second angle of incidence, with radiation reflected from the first partial area being detected. At least one device for image capture is also disclosed.

[0007] US 2011 / 164805 A discloses a system and method for detecting an optically variable material. Such a method comprises generating a first image of at least a partial area of ​​a document, wherein the partial area is irradiated with a first electromagnetic radiation from a first radiation direction. The method further comprises generating a second image of at least a partial area of ​​the document, wherein the partial area is irradiated with a second electromagnetic radiation from a second radiation direction.

[0008] WO 2013 / 017738 A1 discloses the production of markings on a mesh. The document further discloses the illumination of a document with two light sources. US Pat. No. 6,473,165 B1 discloses systems and methods for determining the authenticity of objects. It discloses the preamble of claims 1 and 6.

[0009] Modern security documents can also have a varnished surface. However, a varnished surface can make optical detection difficult due to unwanted reflections. Therefore, it is usually necessary to maintain a predetermined angle difference between an illumination direction and an optical detection direction, at which angles reflections are not detected or are only detected to a limited extent. At the same time, however, a security document can also contain other security elements whose optical detection is difficult or even impossible at the angle difference explained above.

[0010] The technical problem therefore arises of creating a method and a device for checking at least one security element of a security document, which enable a reliable optical detection of the at least one security element, preferably of several security elements.

[0011] The solution to the technical problem results from the objects having the features of claims 1 and 6. Further advantageous embodiments of the invention result from the subclaims.

[0012] It is a basic idea of ​​the invention to illuminate a surface of the security document to be checked under at least two different illumination angles, wherein the illumination angles can be defined relative to a surface of the security document to be checked or to a central optical detection direction of an image detection direction.

[0013] A device for checking at least one security element of a security document is proposed. A security document can be defined as any document that is a physical entity protected against unauthorized manufacture and / or falsification by security features or elements.

[0014] Security features are features that make falsification and / or duplication at least more difficult than simple copying. Physical entities that comprise or form a security feature can be referred to as security elements. A security document can comprise multiple security features and / or security elements. Within the meaning of the definition set out here, a security document always represents a security element. Examples of security documents that also include valuable documents that represent value include passports, identity cards, driver's licenses, identity cards, access control badges, health insurance cards, banknotes, postage stamps, bank cards, credit cards, smart cards, tickets, and labels.

[0015] In particular, the security document can have several, i.e. at least two, security elements. Further, in particular, the security document can have a hologram as a first security element. For the purposes of this invention, a hologram is understood to be an element of the security document that can generate a representation by means of holography. The term hologram includes, among other things, transmission holograms, reflection holograms, Denisyuk holograms, image plane holograms, rainbow holograms, multiplex holograms, and computer-generated holograms. However, the term also includes optically variable features. As a further security element, the security document can have a security thread. A security thread can, for example, be a metallized strip that is arranged within a material of the security document, for example paper. It can also be partially exposed, i.e.be arranged on a surface of the security document. Furthermore, the security thread can be additionally provided with an imprint or with other optically detectable or non-optically detectable properties.

[0016] The device has at least one reference plane, wherein the reference plane is oriented parallel to a surface of the security document to be checked. For example, the device can have a receiving volume for receiving the security document to be checked, wherein the security document must be arranged in the receiving volume for checking. The reference plane can comprise a base area of ​​the receiving volume. A support surface of the device for supporting the security document to be checked can also be arranged in the reference plane.

[0017] The device further comprises at least one image capture device, for example a camera, in particular a CMOS camera or CCD camera. The at least one image capture device is arranged and / or configured such that a central optical axis of the image capture device intersects the reference plane at a predetermined reference angle. The central optical axis of the image capture device can, for example, designate a central axis of symmetry of a detection area of ​​the image capture device.

[0018] Furthermore, the predetermined reference angle is 90°.

[0019] The device further comprises a first illumination device, for example a first light source, more particularly a first illumination device embodied as a linear light source. The linear light source can, in particular, have a predetermined length, wherein the length can, in particular, be equal to or greater than a width of the security document to be checked. The illumination device can comprise various light sources for illumination, in particular a light source embodied as an LED.

[0020] The first illumination device is arranged and / or configured such that a central illumination axis of the first illumination device intersects the reference plane at a first illumination angle. In other words, this means that the reference plane, and thus a surface of a security document to be checked, is illuminated by the first illumination device at the first illumination angle.

[0021] The device further comprises at least one further illumination device, for example, a further light source. The further illumination device can also be designed, in particular, as a linear light source, wherein the further linear light source can have a length equal to or greater than the width of the security document to be checked. The further illumination device can also comprise various light sources, in particular a light source designed as an LED.

[0022] The additional illumination device is arranged and / or configured such that a central illumination axis of the additional illumination device intersects the reference plane at a further illumination angle. In other words, this means that the reference plane, and thus also a surface of the security document to be checked, is illuminated by the additional illumination device at the further illumination angle.

[0023] Furthermore, an amount of an angle difference between the predetermined reference angle and the first illumination angle is greater than an amount of an angle difference between the predetermined reference angle and the further illumination angle.

[0024] An intersection angle of the central optical axis and the central illumination axes with the reference plane can be an acute angle or a right angle enclosed by the respective axis with the reference plane. In this case, the predetermined reference angle, the first illumination angle, and the further illumination angle can each assume values ​​from 0° (exclusive) to 90° (inclusive).

[0025] Furthermore, the predetermined reference angle can be either greater than the first illumination angle or greater than the further illumination angle. In this case, the difference between the reference angle and the respective illumination angle can correspond to the difference between the reference angle and the respective illumination angle.

[0026] Thus, it is possible for the reference plane to be illuminated by the first illumination device at a flatter illumination angle than with the additional illumination device, particularly if the predetermined reference angle is 90°. At the same time, the angle between the optical axis of the image capture device, and thus the optical capture direction, and the additional illumination device can be more acute than the angle between the optical capture device and the first illumination direction.

[0027] This advantageously enables the surface of the security document to be checked to be illuminated at different illumination angles. Illumination at the first illumination angle can, for example, ensure optical detectability of a first security element, in particular a hologram, since the flatter illumination prevents unwanted reflections, particularly on painted surfaces of the security document to be checked. Illumination at at least one further illumination angle can ensure the desired optical detectability of a further security element, in particular a security thread, which cannot be optically detected or cannot be sufficiently detected at the flat first illumination angle.

[0028] Due to the relationship thus given between the illumination angles and the detection direction given by the central optical axis, an overall illumination which is sufficiently good for optical detection can be achieved in an advantageous manner, which enables the detection of several security elements in particular without mutual interference.

[0029] This results in an overall advantageous result that an optical detection, in particular of different security elements of a security element, is ensured with a desired detection quality, which facilitates a subsequent image-based determination of optical properties of the security elements and thus enables a more reliable quality check and / or authenticity check.

[0030] Furthermore, the magnitude of the angular difference between the predetermined reference angle and the first illumination angle assumes an angular value from a first angular interval, wherein the first angular interval comprises angles from 15° to 50°. Thus, the reference plane can be illuminated at an angle in the range of 40° to 75°.

[0031] This illumination advantageously enables very good optical detection of a security element in the form of a hologram, especially if a surface of the security document is varnished. Due to the required angle values, reflections, which would make optical detection of the security feature in the form of a hologram difficult, are avoided.

[0032] Further according to the invention, the absolute value of the angular difference between the reference angle and the further illumination angle assumes an angular value from a further angular interval, wherein the further angular interval comprises angles from 5° to 20°. Thus, the reference plane can be illuminated at an angle in the range of 70° to 85°.

[0033] This advantageously enables particularly good optical detection of a security element designed as a security thread, which cannot be optically detected or cannot be optically detected sufficiently well when illuminated at the first illumination angle.

[0034] In a preferred embodiment, the angular difference between the predetermined reference angle and the first illumination angle is 30°. Alternatively or cumulatively, the angular difference between the predetermined reference angle and the further illumination angle is 15°. Tests have shown that particularly good optical detection of a first security element formed as a hologram and a further security element formed as a security thread of the security document is possible at these illumination angles.

[0035] Furthermore, the predetermined reference angle is 90°. This clearly means that a surface of the security document is scanned vertically from above or below. Tests have also shown that particularly good optical detection of security elements is possible in this case.

[0036] In a further embodiment, the first illumination device generates light with a first spectrum, wherein the further illumination device generates light with a further spectrum, wherein the first spectrum is different from the further spectrum. This means that the further spectrum comprises at least one frequency or wavelength or a frequency range or wavelength range, in particular with at least one predetermined intensity, which is not covered by the first spectrum, in particular not with the predetermined intensity. Alternatively or cumulatively, the first spectrum can comprise a frequency or a wavelength or a frequency range or a wavelength range, in particular with a predetermined intensity, which is not covered by the further spectrum, in particular with the predetermined intensity. However, it is not excluded that frequency or wavelength ranges of the two spectra overlap.

[0037] This advantageously results in a further improvement in the optical detectability of various security elements. In particular, the previously explained additional security element, for example, a security thread, can be optically detectable with sufficient quality when illuminated with the additional spectrum, wherein, on the one hand, the illumination with the first spectrum does not influence the optical detection of the additional security element or only influences it to a slight extent, and, on the other hand, the illumination with the additional spectrum does not influence the optical detection of the first security element, for example, the hologram, or only influences it to a slight extent.

[0038] In a preferred embodiment, the first illumination device generates light in the visible range, while the further illumination device generates light in the near-infrared range. The visible range can also be referred to as the VIS range and can, for example, comprise wavelengths from 380 nm to 780 nm, in particular up to 780 nm (exclusive). The near-infrared range can, for example, comprise wavelengths from 780 nm, in particular up to 780 nm (inclusive), to 3 µm.

[0039] However, it is also possible for the first illumination device to generate light in both the visible and near-infrared ranges, or for the first illumination device to generate light exclusively in the visible range. Furthermore, the second illumination device can generate light exclusively in the near-infrared range.

[0040] This advantageously results in illumination which enables very good optical detection of the further security element, in particular the security element designed as a security thread, and at the same time does not adversely affect the optical detection of the first security element, in particular the first security element designed as a hologram.

[0041] The device further comprises at least one further image capture device, wherein the further image capture device is arranged and / or configured such that a central optical axis of the further image capture device, and thus a further optical capture direction, intersects the reference plane at a predetermined further reference angle. According to the invention, the predetermined further reference angle is equal to the first predetermined reference angle.

[0042] In this case, the first image capture device can be configured such that light with the first spectrum can be captured, in particular exclusively, by the first image capture device. Furthermore, the further image capture device can be configured such that light with the further spectrum can be captured, in particular exclusively, by the further image capture device.

[0043] Thus, an optical detection of the previously explained first security element by the first image capture device and an optical detection of the further security element by the further image capture device are advantageously possible.

[0044] In a further embodiment, the device comprises at least one evaluation device, wherein at least one property of the at least one imaged security element can be determined using the evaluation device based on an image and compared with a reference property, wherein a quality and / or authenticity of the at least one security element can be determined depending on the comparison. Image-based here means that the at least one property can be determined depending on an image generated by the first and / or by the at least one further image capture device, in particular based on image data.

[0045] A variety of properties can be considered as a property. In particular, a property can be a position and / or orientation of the security element relative to a coordinate system fixed to the security document. Furthermore, a property can be a reflection property, for example an intensity of the light reflected by the security element, a wavelength of the reflected light, or a phase of the reflected light. Furthermore, a property can be the presence or absence of an image of the security element. Furthermore, a property can be a structure-related property. This means, for example, that it is determined whether an image with at least one predetermined property or a predetermined graphic element was generated. Furthermore, a property can be information encoded by the security element that can be extracted and evaluated based on the image.This information may, for example, be a document number, an image of a person authorized to maintain the security document, or other information.

[0046] Of course, there are further properties of the security elements that can be evaluated by the expert.

[0047] Further proposed is a method for checking at least one security element of a security document. A surface of the security document is illuminated by a first illumination device at a first illumination angle. The surface of the security document is then illuminated by a further illumination device at a further illumination angle. Furthermore, at least one image of the surface of the security document is captured at a predetermined reference angle, wherein an angular difference between the reference angle and the first illumination angle is greater than an angular difference between the reference angle and the further illumination angle.Furthermore, at least one property of the at least one imaged security element is determined on an image-based basis and compared with a reference property, wherein a quality and / or authenticity of the at least one security element is determined depending on the comparison.

[0048] The proposed method can be carried out, in particular, using a device according to one of the previously explained embodiments. At the same time, the proposed device can be designed such that the proposed method can be carried out using the device.

[0049] In particular, the image can be generated at an angle of 90° to the previously explained reference plane and thus to the surface of the security document, wherein the surface is additionally illuminated at a first illumination angle from an angular interval of 45° to 75°, preferably 60°, and at a further illumination angle of 70° to 85°, preferably 75°. In particular, the security document can comprise a hologram as the first security element and a security thread as the further security element.

[0050] The invention is explained in more detail using an exemplary embodiment. The figures show: Fig. 1 is a schematic side view of a device according to the invention, Fig. 2 is a schematic plan view of a device according to the invention, and Fig. 3 is a schematic side view of a further device according to the invention.

[0051] In Fig. 1 1 shows a device 1 according to the invention for testing a security element embodied as a hologram 2 and a security element embodied as a security thread 3 of a security document 4. The device 1 has a reference plane 5, which can, for example, comprise a support surface for the security document 4. Also shown is a receiving volume 6 of the device 1, in which the security document 4 is to be arranged for optical detection. The reference plane 5 can comprise a base area of ​​the receiving volume.

[0052] Also shown is a longitudinal direction x, which can designate a travel direction of the security document 4, wherein the direction is indicated by an arrow. The travel direction designates a direction in which the security document 4 can be transported into and out of the receiving volume 6, for example, by means of a suitable transport device. Also shown is a vertical direction z, which is oriented perpendicular to the reference plane 4 and thus perpendicular to a surface 7 of the security document 7 to be checked.

[0053] The device 1 comprises a first image capture device 8, which is designed as a VIS camera and can capture light in the visible range for image generation. Furthermore, the device 1 comprises a further image capture device 9, which is designed as an NIR camera and can capture light in the near infrared range for image generation.

[0054] The device further comprises a first illumination device 10a and a second illumination device 10b. Central illumination axes 11a, 11b of the illumination devices 10a, 10b are shown schematically, with the illumination directions of these illumination devices 10a, 10b indicated by arrows. The first and second illumination devices 10a, 10b emit light with wavelengths from the visible range, in particular light with wavelengths exclusively from the visible range. However, it is also possible for the first and second illumination devices 10a, 10b to emit light with wavelengths from both the visible range and the near-infrared range.

[0055] The device 1 further comprises a third illumination device 12a and a fourth illumination device 12b, wherein central illumination axes 13a, 13b are also shown and the corresponding illumination direction is indicated by arrows. The third and fourth illumination devices 12a, 12b emit light with wavelengths in the near infrared range, in particular light with wavelengths exclusively in the near infrared range.

[0056] A central optical axis of the image capture devices 8, 9 is oriented parallel to the vertical axis z. Thus, the central optical axis of the image capture devices 8, 9 intersects the reference plane 5 at a reference angle of 90°. Fig. 1 It is shown that an intersection point of the central illumination axes 11a, 11b, 13a, 13b lies in the reference plane 5. However, this intersection point can also lie above or below the reference plane 5.

[0057] The first and second illumination devices 10a, 10b are each arranged and / or configured such that an angular difference (α) between the reference angle and the first illumination angle is greater than an angular difference (β) between the reference angle and the further illumination angle. The first illumination angle can be defined as 90°-α or 90°+(-α) and the further illumination angle as 90°-β or 90°+(-β).

[0058] The angle differences are shown with signs, where a positive sign represents a rotation in the mathematically positive sense, i.e. left-handed, around a lateral axis y, which is in Fig. 1 is oriented from the drawing plane towards a viewer (see Fig. 2 ).

[0059] In particular, the amount of the angular difference (α) between the reference angle and the first illumination angle can be 30°, wherein the amount of the angular difference (β) between the reference angle and the further illumination angle can be 15°.

[0060] In Fig. 1 It is shown that the first illumination device 10a, which illuminates the reference plane 5 and thus the surface of the security document 4 at the first illumination angle, is arranged along the longitudinal direction x in front of a center point of the security document 4 and thus in front of a center point of the support surface, and the second illumination device 10b is arranged along the longitudinal direction x behind this center point. Accordingly, the third illumination device 12a is arranged along the longitudinal direction x in front of the center point, and the fourth illumination device 12b is arranged behind the center point.

[0061] In Fig. 2 is a schematic plan view of the Fig. 1 The device 1 shown is shown. Also shown are the first image capture device 8 and the further image capture device 9, as well as the first illumination device 10a, the second illumination device 10b, the third illumination device 12a, and the fourth illumination device 12b. Also shown are the security thread 3 and the hologram 2 of the security document 4.

[0062] Also shown is a lateral direction y, which is perpendicular to the longitudinal direction x and the vertical direction z (see Fig. 1 ) is oriented. It is shown here that the illumination devices 10a, 10b, 12a, 12b are each designed as line light sources, wherein a length of the line light sources along the lateral direction y is equal to a width of the security document 4 or the support surface measured along the lateral direction y.

[0063] In Fig. 3 A schematic side view of a further device 1 according to the invention is shown. This device is essentially like the one shown in Fig. 1 shown device 1 is formed, therefore reference is made to the corresponding explanations Fig. 1 referred to.

[0064] In contrast to the Fig. 1 The device 1 shown in Fig. 3 The third illumination device 12a shown is arranged on the first illumination device 10a, in particular mechanically fastened. The fourth illumination device 12b is likewise arranged on the second illumination device 10b, in particular mechanically fastened. The fastening can be effected in such a way that the third and fourth illumination devices 12a, 12b each have a desired orientation, in particular such that an amount of an angular difference (α) between a reference angle and the first illumination angle is greater than an amount of an angular difference (β) between the reference angle and the further illumination angle. Again, the first illumination angle can be determined as 90°-α or 90°+(-α) and the further illumination angle as 90°-β or 90°+(-β).In particular, the arrangement and / or attachment of the illumination devices 10, 10b, 12a, 12b can be such that the angular difference (α) between the reference angle and the first illumination angle is 15°, while the angular difference (β) between the reference angle and the further illumination angle can be 7.5°. This means that central illumination axes 11a, 11b of the first and second illumination devices 10a, 10b intersect at an angle of 30°, while central illumination axes 13a, 13b of the third and fourth illumination devices 12a, 12b intersect at an angle of 15°.

[0065] The third and fourth illumination devices 12a, 12b can be designed as IR LED strips.

[0066] Also shown are lenses 14a, 14b, which are arranged on the first and second illumination devices 10a, 10b for beam guidance and / or beam shaping.

[0067] It is further shown that the first and second illumination devices 10a, 10b are each connected via light guides 15a, 15b, e.g. light guides 15a, 15b designed as fiber optic cables, to a common light source 16, which thus forms part of the illumination devices 10a, 10b. However, it is also possible for the illumination devices 10a, 10b not necessarily to comprise a light source 16, but to be connected to such a light source 16. It is further shown that the light source 16 is connected to the illumination devices 10a, 10b via a filter element 17, in particular an IR filter element 17. Thus, a portion of the light generated by the light source 16 with wavelengths from a specific wavelength range, in particular from the near infrared range, can be filtered out of the light generated by the light source 16. The light source 16 can be a halogen lamp, for example.

[0068] It is further shown that the device 1 comprises only a first image capture device 8, which can, for example, capture both light in the visible range and light in the near infrared range. Of course, however, as in Fig. 1 shown, a first and second image capture device 8, 9 may be present, wherein the first image capture device 8 can capture light in the visible range and the second image capture device 9 can capture light in the near infrared range.

[0069] In Fig. 3 It is shown that an intersection point of the central illumination axes 11a, 11b, 13a, 13b lies in the reference plane 5. List of reference symbols

[0070] 1Device 2Hologram 3Security thread 4Security document 5Reference plane 6Recording volume 7Surface 8First image capture device 9Further image capture device 10aFirst illumination device 10bSecond illumination device 11aIllumination axis 11bIllumination axis 12aThird illumination device 12bFourth illumination device 13aIllumination axis 13bIllumination axis 14aLens 14bLens 15aLight guide 15bLight guide 16Light source 17Filter element α, -αAngle difference β, -βAngle difference xLongitudinal direction yLateral direction zVertical direction

Claims

1. Device for testing at least one security element of a security document (4), wherein the device (1) has at least one reference plane (5), wherein the reference plane (5) is orientated parallel to a surface (7) of the security document (4) to be tested, wherein the device (1) comprises at least one image acquisition device (8), wherein the at least one image acquisition device (8) is arranged and / or constructed in such a way that a central optical axis of the image acquisition device (8) intersects the reference plane (5) at a predetermined reference angle, wherein the device (1) comprises a first illumination device (10a), wherein the first illumination device (10a) is arranged and / or constructed in such a way that a central illumination axis (11a) of the first illumination device (10a) intersects the reference plane (5) at a first illumination angle, wherein the device (1) comprises at least one further illumination device (12a), wherein the further illumination device (12a) is arranged and / or constructed such that a central illumination axis (13a) of the further illumination device (12a) intersects the reference plane (5) at a further illumination angle, wherein an amount of an angular difference (α) between the reference angle and the first illumination angle is greater than an amount of an angular difference (β) between the reference angle and the further illumination angle, wherein the amount of the angular difference (α) between the reference angle and the first illumination angle assumes an angular value from a first angular interval, wherein the first angular interval comprises angles from 15° to 50°, wherein the amount of the angular difference (β) between the reference angle and the further illumination angle assumes an angular value from a further angular interval, wherein the further angular interval comprises angles from 5° to 20°, wherein the reference angle is 90°, wherein the device (1) comprises at least one further image acquisition device (9), wherein the further image acquisition device (9) is arranged and / or constructed such that a central optical axis of the further image acquisition device (9) intersects the reference plane (5) at a predetermined further reference angle, characterised in that the predetermined further reference angle is equal to the first predetermined reference angle.

2. Device according to claim 1, characterised in that the amount of the angular difference (α) between the reference angle and the first illumination angle is 30° and / or the amount of the angular difference (β) between the reference angle and the further illumination angle is 15°.

3. Device according to one of claims 1 to 2, characterised in that the first illumination device (10a) generates light with a first spectrum, wherein the further illumination device (12a) generates light with a further spectrum, wherein the first spectrum is different from the further spectrum.

4. Device according to claim 3, characterised in that the first illumination device (10a) generates light in the visible range, the further illumination device (12a) generating light in the near infrared range.

5. Device according to one of claims 1 to 4, characterised in that the device (1) comprises at least one evaluation device, wherein at least one property of the at least one imaged security element can be determined in an image-based manner by means of the evaluation device and can be compared with a reference property, wherein a quality and / or an authenticity of the at least one security element can be determined as a function of the comparison.

6. Method for testing at least one security element of a security document (4), wherein a surface (7) of the security document (4) is illuminated by means of a first illumination device (10a) at a first illumination angle, wherein the surface (7) of the security document (4) is illuminated by means of a further illumination device (12a) at a further illumination angle, wherein at least one image of the surface (7) of the security document (4) is generated at a predetermined reference angle by an image capture device (8), wherein an amount of an angular difference (α) between the reference angle and the first illumination angle is greater than an amount of an angular difference (β) between the reference angle and the further illumination angle, wherein at least one property of the at least one imaged security element is determined on the basis of an image and compared with a reference property wherein a quality and / or an authenticity of the at least one security element is determined as a function of the comparison, wherein the amount of the angular difference (α) between the reference angle and the first angle of illumination assumes an angular value from a first angular interval, wherein the first angular interval comprises angles of 15° to 50°, wherein the amount of the angular difference (β) between the reference angle and the further angle of illumination assumes an angular value from a further angular interval wherein the further angular interval comprises angles of 5° to 20°, wherein the reference angle is 90°, wherein at least one image of the surface (7) of the security document (4) is produced at a further predetermined reference angle by a further image capture device (9), characterised in that the predetermined further reference angle is equal to the first predetermined reference angle.