WO2004013817A2 - Device and document for processing security documents - Google Patents

Abstract

The invention relates to a device and method for processing security documents, consisting of a verification of a security element of said security document, especially a verification of the manner and/or authenticity and/or negotiability of a security document with an optically variable effect. Said security elements can be verified in a particularly simple and reliable manner by virtue of the fact that the light emitted from an illuminated area of the security element is machine captured in one or several directions which do not correspond to the direction of reflection and the illuminated area is image captured.

Description

 Device and method for processing documents of value

The invention relates to a device and a method for processing documents of value, with a test device for checking a security element of the document of value, in particular for checking the type and / or authenticity and / or fitness of security elements which have an optically variable effect, in which the security element generates different visual impressions from different viewing angles. The invention further relates to documents of value with special security elements, the security elements themselves and an intaglio printing plate for producing such documents of value or security elements.

Such security elements can be a component of value documents, such as banknotes, credit cards, personal documents or also product protection labels for identifying the authenticity of different goods. Although the present invention is not limited to this, the following section deals primarily with the testing of security elements with an optically variable effect on banknotes.

On the one hand, in the case of banknotes as such security elements, diffraction-optical structures, such as Holograms, especially surface holograms, or Kinegrarnrne also uses intaglio profiles.

However, it is also possible to use all other optically variable elements which give a different visual impression at least at two different viewing angles. For example, optically variable inks are used as printing inks, optically variable thin-film films or iriodin prints or polymeric liquid crystal inks, which differ from one another at different viewing angles Convey color impression. This is also known as the color change effect. So-called “latent images” can also be used. Such security elements are described by way of example in EP 0 863 815 AI and EP 0 827457 AI.

Various test methods exist for the machine testing of banknotes with such security elements. WO 98/55963 describes, for example, a method for recognizing diffraction structures on banknotes. The banknote to be checked is irradiated vertically over a large area with parallel light. The entire illuminated area corresponding to the different diffraction directions is focused on separate sensors or alternatively on different sensor areas of a single sensor. By comparing the measured signals with predetermined reference values corresponding to the expected diffraction phenomena of a particular diffraction structure is closed to the ^'presence.

This known system has the disadvantage that the position or shape of the diffraction structures on the banknote cannot be exactly determined due to the large-area illumination and subsequent point-like focusing of the illuminated areas.

Proceeding from this, it is the object of the present invention to provide a device and a method for the machine check of documents of value, which allow a simple and secure machine check, in particular of security elements with an optically variable effect.

This task is solved by the subordinate claims. The dependent claims describe preferred configurations. One aspect of the present invention is therefore based on the examination, in particular the examination of the type and / or authenticity and / or fitness for circulation of a security element of a value document with an optically variable effect, by machine detection of the one emanating from an illuminated area of the security element in one or more different directions Light that does not correspond to the direction of reflection in combination with image acquisition of the illuminated area.

It should be noted that the direction of reflection in the sense of the present invention is understood to mean the direction of a non-diffuse and directional reflection, in which the angle of incidence corresponds to the angle of reflection of the light radiation. In addition, image acquisition is understood to represent an illuminated area of the banknotes on a sensor surface of a sensor, in order to thereby obtain a two-dimensional image of at least one area of the banknote, which e.g. with known methods of pattern recognition automatically with predetermined reference images, e.g. corresponding to real banknotes.

This procedure allows you to easily and reliably determine the exact position and shape, such as the outline and displayed information of each individual security element on each banknote, not only by means of image capture, but also by combining it with the capture of light that is not in the Direction of reflection from the banknote to be checked also suggests the presence of, for example, diffractive structures. The possibility of checking the type of security element is understood to mean that a distinction can also be made between different security elements, for example bank notes of different denominations. When checking for the presence of security elements with an optically variable color effect, such as, for example, banknotes with printed optically variable ink, it is also possible to compare light coming from the non-reflection direction with light coming from any other direction, preferably also by comparing it with predefined ones Reference values corresponding to, for example, real banknotes, can be concluded that there is a suitable directional dependency. For this purpose, for example, a color comparison or a comparison of the signal strength for a specific color can be carried out in the two measuring directions.

In contrast, according to WO 98/55963, it is only determined whether any security elements with suitable diffraction characteristics are present anywhere on the banknote. A more precise check with regard to the number, shape and distribution of the security elements in the illuminated area of the banknote is not possible.

According to a preferred embodiment of the present invention, the image acquisition is carried out by means of a separate sensor. However, particularly preferred is the image acquisition by at least one of the sensors which are used to detect the light not emanating from the bank note to be checked in the reflection direction. This has the advantage that the test device can not only be constructed more cheaply, but also more compactly.

It has been found that there are a number of influencing variables when testing security elements, in particular those with an optically variable effect, which are described below by way of example using preferred embodiments. Particular attention is paid to the testing of diffraction structures, such as holograms and / or kinegrams. men, which can be inserted or applied in a banknote paper. Special features of the testing of security elements with a color change effect are pointed out separately.

Banknotes to be checked usually have, depending on their denomination, security elements with an optically variable effect, which have different properties. So you can e.g. display different information in the diffraction pattern and / or bend in different diffraction directions or angles.

The directionality of the diffraction phenomena proves to be an essential property in banknotes in order to verify the existence of diffractive structures with a high degree of certainty. For example, by detecting light that does not emanate from a directionally irradiated bank note in the direction of reflection, by means of sensors that are arranged in the diffraction direction or directions to be expected, a distinction can be made between non-diffractive, counterfeit bank notes, such as e.g. to photocopies, be done safely.

The diffraction angles are wavelength-dependent, so that there are color-dependent signals in at least one illumination with several colors in a predetermined direction of diffraction. When using illuminating light or corresponding sensor color filters of different wavelengths or wavelength ranges, there are different diffraction characteristics (diffraction directions, diffraction intensity in these directions), which in turn have the authenticity of such security elements checked particularly reliably when detected by assigned sensors. If at least one sensor is installed to detect light emanating from the bank note in a fixed solid angle range, it can be installed consequently, by choosing or varying the illumination color, a higher signal intensity is measured for real banknotes than for other colors for a certain color that is specific for the diffraction structure to be checked. As a result, a distinction can therefore be made between several different diffraction structures.

If banknotes of different denominations under the same lighting conditions, i.e. especially in the case of illumination in the same direction and with the same wavelength, if all the diffractions point in at least one common direction, the detection of diffraction light in only this one direction can be sufficient to carry out a test for different denominations with a simple sensor with little effort perform. For example, all current EURO banknotes show diffraction in one direction parallel to the short edge of the banknotes. Therefore e.g. in this case, a single sensor is sufficient for testing, which detects this light coming out parallel to the short bank note edge.

Another relevant variable is the amount of the measurement signals from the sensors. If measurements are taken in the direction of diffraction, the signals for associated real banknotes are significantly larger than e.g. for photocopies that only scatter diffusely in the non-reflection direction. In order to improve the measurement accuracy, in particular to better distinguish it from light that is only diffusely scattered, it is therefore preferable to standardize the intensity of the measurement signals compared to the intensity of the illuminating light.

The signal strength can also be used to obtain a criterion for the production quality of newly manufactured banknotes and / or for the degree of wear of circulating banknotes. In the event of deviations from a specified threshold len value or acceptance range, can be concluded, for example, the poor manufacturing quality of the respective security elements. Furthermore, for banknotes already in circulation, lower signal strengths given given lighting and measurement conditions are a sign of signs of wear and tear, which can be used as a criterion for separating out such banknotes.

The polarization behavior of the security elements can also serve as an additional or alternative test criterion. It has been shown that when diffraction of linearly polarized light ari security elements with an optically variable effect, the polarization is at least partially retained. This applies not only to diffraction phenomena, but also to reflections on security elements with a color change effect, e.g. on prints with iriodin or optically variable inks, and even on intaglio profiles that show no optically variable effect. In contrast, this effect has not been shown with scattering on the banknote paper itself and with offset printing elements. The light incident on such areas is reflected essentially diffusely. Only when there is a very large, almost grazing incidence is the light reflected in larger proportions, whereby the polarization is clearly retained. Therefore, in this case of a polarization test, illumination with a small angle to the perpendicular of the illuminated area is particularly advantageous. The angle of incidence should be at least less than 40 degrees, preferably less than 20 degrees, a vertical incidence of light in which the angle of incidence is zero is particularly preferred.

Intaglio printing is usually characterized in that linear depressions are introduced into the printing plates in order to produce a printed image. The ink-transferring areas of the printing plate are thus present as depressions in the printing plate surface. This deepening Formations are created using a suitable engraving tool or using etching. In the mechanically manufactured printing plate for intaglio printing, a wider line is created with increasing engraving depth due to the usually tapered engraving tools. In addition, the color absorption capacity of the engraved line and thus the opacity of the printed line increases with increasing stitch depth.

When etching intaglio printing plates, the non-printing areas of the printing plate are covered with a chemically inert lacquer. The engraving is produced in the exposed plate surface by subsequent etching, the depth of the engraving lines depending in particular on the etching time. Color of pasty consistency is applied to the engraved printing plate from the actual printing process, and the excess printing ink is removed from the surface of the printing plate by means of a doctor blade or a wiping cylinder, so that the ink only remains in the depressions. Subsequently, a substrate, usually paper, is pressed against the printing plate and pulled off again, the color being pulled out of the depressions in the printing plate, adhering to the surface of the substrate and forming a printed image there. If glazing colors are used, the thickness of the paint application determines the color tone. This gives a light color tint when printing on a white data carrier with thin layers of ink, and darker tones when printing with thick layers of ink. The thickness of the ink layer depends on the engraving depth to a certain extent.

The line intaglio printing technique allows a relatively thick color application on a data carrier in comparison to other printing techniques, such as offset printing. The comparatively thick ink layer produced using the line intaglio printing process is together with the partial deformation the paper surface, which is created by pressing the paper into the engraving of the printing plate, can easily be felt manually even by the layman and thus easily recognizable as an authenticity feature based on its tactility. The tactility cannot be imitated with a copier, so that the line intaglio printing technique offers high-quality protection against counterfeiting.

With special additional effort, these printed images can even be printed over the entire area. According to the invention, this color layer applied to the paper by intaglio printing can have a symmetrical, but preferably an asymmetrical profile (in the following intaglio printing profile). The asymmetrical profile has the additional advantage that it can preferably not be distinguished from a symmetrical profile with the naked eye, but can be easily detected with the device according to the invention, since the reflection of the irradiated polarized light is targeted in one direction by means of the asymmetrical profile can be directed. A machine-readable authenticity feature can be generated purely in terms of printing technology.

Using the asymmetrical intaglio printing profiles, a large number of different codings can also be incorporated into the security element according to the invention, for example by specifically controlling the asymmetry of the color layers or by having different asymmetrical profiles in different areas of a security element. It is also conceivable to assign specific colors to the printing ink to specific geometric profiles or to combine them with other security features in the printing inks, such as fluorescent substances, magnetic or conductive pigments. Unsymmetrical profiles are generated in the security element with the intaglio printing plates according to the invention. In order to achieve the asymmetry in the printed profile, an asymmetrical engraving line, for example, is milled in the printing plate at the corresponding point. This asymmetrical engraving is realized, for example, with the help of two milling tools that have different flank angles.

The intaglio printing plates according to the invention are preferably produced by engraving with a rapidly rotating, tapering stylus, for example according to a method described in WO 97/48555.

If directly adjacent color layers are desired in the security element, so-called “separating cards” according to WO 00 / 2O216 and WO 20217 are integrated into the printing plate between the adjacent surfaces.

Furthermore, the determination of the position and / or the outline of the bank note in relation to the test device is also advantageous, in order to thereby reduce the measurement window, i.e. the area in which the measurement or the measurement signals are evaluated can also be limited, depending on the position or the outline, optionally in a piece-specific manner, which can result in data reduction and thus faster evaluation.

Taking into account the aforementioned factors, the components of the test facility can preferably have one or more of the following properties: In addition to coherent laser diodes, non-coherent light sources such as incandescent lamps, LEDs or fluorescent lamps can also be used for lighting. The lighting should have a defined divergence and direction so that the contrast against diffuse scatter from the banknote paper to be checked is large enough. However, a minimum aperture is necessary to compensate for changes in direction of the paper.

The spectrum of the light source can be selected differently. For example, be illuminated with white light. This has the advantage that there is simultaneously a wide band of diffraction directions for different colors, since the sine of the diffraction angle is essentially proportional to the wavelength. By choosing sensors for different colors and / or with changing color filters for the sensors and / or a spectral analysis of the measurement signals, e.g. Even with constant lighting with white light, a color-selective analysis and thus detection and differentiation between different diffraction structures can be carried out safely. In this case, however, the intensity of the scattered light from the paper is increased compared to monochromatic lighting.

For this reason, one or more individual colors or color ranges can alternatively be illuminated. In this case too, the presence of diffraction and / or differences in the diffraction characteristics can be inferred from the color information in the case of lower interference signals due to diffuse light scattering ,

When the illumination wavelength is varied, for example, a single sensor can also be sufficient to test different diffraction structures, which in themselves are used when using only a single illumination tion wavelength may not all bend in the solid angle range detectable by the sensor.

In the case of single-color or white lighting, the light can preferably be emitted in a stationary manner, with multi-color lighting time-division lighting is advantageous. Alternatively, in this case of multi-colored lighting, there may also be a plurality of sensors arranged one behind the other or next to one another, each of which is sensitive to another of the lighting colors. With a sensor line e.g. also give different 'color filters for neighboring pixels, corresponding to individual lighting colors. This means that lighting that is stationary over time is also possible.

Particularly preferred refinements also result when individual banknotes are guided past or through a sensor for measurement by means of a transport device. This usually takes place in devices for sorting and / or counting or for depositing and / or withdrawing banknotes.

In this case, the use of one or more separate line sensors, in particular also in combination with a cell-shaped illumination, proves to be very advantageous, the line sensors or the line-shaped illumination in each case extending transversely, preferably perpendicularly to the transport direction. This has the advantage that the test device can be constructed very compactly using inexpensive components. The arrangement of the sensors and thus the direction of observation will preferably be given by the bank note edges, an additional line sensor at 45 ° being optionally added to this. The line-shaped illumination can be carried out, for example, by using a cell-shaped light source, ie a light source with a line-shaped aperture diaphragm. CCD line sensors, for example, are used as line sensors. The term line sensor can in particular mean that the sensor consists of a single row of sensor fields, ie pixels.

The length of the illuminated surface of the banknote and the light-sensitive measuring surface of at least one of the line sensors preferably corresponds approximately or is greater than or equal to the length of the largest security element to be measured, but particularly preferably corresponds to at least the length of the. largest banknote so that the entire banknote area can be scanned by the line sensor.

Preferably, a line sensor is also close to the light source, e.g. the LED line, arranged to detect light coming out perpendicular to the direction of transport. This line sensor can optionally also be used for image acquisition of the illuminated area according to the invention.

According to another preferred embodiment, a further line sensor for detecting the light emanating in a certain angular range in or against the transport direction will be arranged. Several such further line sensors can be arranged next to one another, each of the further line sensors serving in each case for detecting a different direction, ie a different specific angular range in the light emanating from or against the transport direction. This has the advantage that detection of different security elements, for example with different grating parameters of the diffraction structures that bend in different directions, is easily possible. To test holograms or kinegrams, for example, the banknotes are preferably illuminated vertically and the light emanating from the illuminated banknote in the expected diffraction directions is detected by the aforementioned line sensors. With the same illuminance, the radiation intensity diffracted and detected by a diffraction structure in its first (or also higher) diffraction direction is greater than that which diffusely reflects in such a direction from a non-diffractive structure, such as conventional paper or metal strips becomes. In order to be able to measure this difference, an illumination control or a detection of the intensity of the illuminating radiation is advantageous as a reference for normalizing the measurement signals of the sensors.

It should be noted that the use of line sensors is particularly advantageous in particular in banknote processing devices, although cameras with two-dimensional image acquisition can also be used as an alternative or in addition.

For testing security elements with color changes when viewed in different directions, e.g. banknotes that are printed with optically variable ink, not perpendicular, but oblique lighting proves to be particularly preferred. When using an LED line, the azimuth of the radiation should be oriented perpendicular to the LED line. A lighting control or reference for normalizing the measurement signals is not absolutely necessary in this case.

Instead, it may be sufficient if only a color difference measurement is carried out for the sensors arranged in two different directions in order to determine the characteristic different color properties. to be able to measure. For example, a sensor can preferably be arranged in and a sensor against the oblique direction of illumination, in order to infer differences in the intensity of the colors by means of a comparison, such as a difference between the measurement signals of the two sensors.

In the case of illumination with multiple colors, the signals recorded in parallel in all the sensors are sorted into a value document according to the time-multiplex parameters used, separated according to illumination colors and evaluated separately.The sensors are preferably broadband in the visible spectral range, color selection is not absolutely necessary.

In all of the previously described embodiments, the illumination and / or the detection of the light emanating from the illuminated banknote is preferably carried out by means of self-focusing lenses, so-called SELFOC® lenses. These are cylindrical optical elements made of a material that has a refractive index that decreases from the optical axis of the cylinder to its surface. By using such a lens, for example, a one-to-one mapping of the area to be measured onto the sensor, which is independent of the distance from the bank note to the sensor and is adjustable, is achieved. On around the usual bumps of banknotes in circulation, this property is of great advantage in order to be able to compensate for position fluctuations in the image. Instead of SELFOC lenses, weakly telecentric lenses also prove to be advantageous. The SELFOC lenses can also be used to adjust the aperture angle of the illuminating light source. Another idea of the present invention is the use of prisms for beam deflection. In particular, Fresnel prisms have the advantage that the test device can be designed to be particularly compact. In order to ensure an approximately symmetrical beam path, the flat surface of the Fresnel prism should preferably face the security element.

Yet another idea of the present invention consists in illuminating an area of the security element by at least two light sources arranged at different lighting angles. In contrast to the variants mentioned above, this has the advantage that a single common sensor can already be sufficient to detect the light emitted by the banknote with respect to the illumination angles at different diffraction or reflection angles using the time-division multiplex method. Since light sources are generally cheaper than corresponding sensors and only the measurement signals of a single sensor need to be evaluated, the test device can be manufactured more cost-effectively.

According to a further alternative, at least two images of the illuminated area are generated by means of a symmetrical beam path and detected by associated sensors, each of which corresponds to a different viewing angle. This can ensure that the images have the same image scale, or the same enlargement or reduction, and / or no or the same distortion. This makes it easy to compare the signals according to the two figures, e.g. possible by simple difference formation.

In particular, a single prism, in particular a Fresnel prism, can in turn be used to simultaneously remove the two images. to be able to reproduce different viewing angles on two separate sensor surfaces.

It should be emphasized that the individual features of the dependent claims and / or the exemplary embodiments mentioned in the description can be used advantageously in combination, also completely or at least partly independently of one another and from the subject matter of the main claims.

For example, the solutions described, to use at least two light sources arranged at different illumination angles, or to check the polarization, in particular the direction of polarization, are also advantageous regardless of whether an image acquisition according to the invention is actually carried out.

Further advantages of the present invention result from the exemplary embodiments explained in more detail with reference to the attached drawings.

The show

Figure 1 is a schematic perspective view of a banknote showing the beam paths of the test device according to Figures 2 and 3;

FIG. 2 shows a schematic view from above of part of a bank note processing device with a test device according to a first exemplary embodiment; Figure 3 is a sectional view of the device of Figure 2 along the line II.

FIG. 4 shows a view corresponding to FIG. 3 of part of a bank note processing device with a checking device according to a second exemplary embodiment;

FIG. 5 shows a view corresponding to FIG. 3 of part of a bank note processing device with a checking device according to a third exemplary embodiment;

FIG. 6 shows a view corresponding to FIG. 3 of part of a bank note processing device with a checking device according to a fourth exemplary embodiment;

FIG. 7 shows a view corresponding to FIG. 3 of part of a bank note processing device with a test device according to a fifth exemplary embodiment;

FIG. 8 shows a view corresponding to FIG. 3 of part of a bank note processing device with a checking device according to a sixth exemplary embodiment;

FIG. 9 shows a view corresponding to FIG. 3 of part of a banknote processing device with a checking device according to a seventh exemplary embodiment; and

FIG. 10 shows a view corresponding to FIG. 3 of part of a banknote processing device with a checking device according to an eighth exemplary embodiment, FIG. 11 shows a document of value according to the invention in supervision,

Figure 12 is a cross section along the line A-A in Figure 11 and

Figure 13 shows a cross section through the intaglio printing plate according to the invention.

The bank notes 3 to be checked with the checking devices 2 according to the invention have an embossing hologram 5 as an example as a security element 5. As indicated in FIG. 1, this hologram 5 has i.a. the property that it bends light both in the direction R1 at an angle α and in the direction R2 at an angle β to the direction B in the case of perpendicular irradiation in the direction B and thereby represents different information in these directions. For example, when viewed in the direction of R1, the number "50" and in the perpendicular direction R2 the character "€" can be clearly seen. Banknotes of different denominations have different diffraction properties. The number shown in the direction of R1 can e.g. be chosen according to the denomination. Typical angles α, ß are 15 to 25 degrees at typical illumination wavelengths from 450 nm to approx. 900 nm.

FIGS. 2 and 3 show a first example of an associated checking device 2. This is part of a bank note processing device 1, which can be constructed in a manner known per se and therefore not in the. Detail is shown. The banknotes 3 to be checked are individually transported past the checking device 2 in the X direction with their transverse side ahead by means of a transport device 4, which comprises, for example, a belt and / or roller transport. The checking device 2 can have further components for machine checking of, for example, optical, electrical and / or magnetic bank note features, but is particularly characterized by the components for checking security elements 5 described in more detail below with an optically variable effect.

To detect and test such a security element 5, the test device 2 preferably has a light source 6 and two sensors 7 and 8. The test device 2 is used in particular to test the diffraction phenomena of diffraction structures 5, such as Holograms and / or kinegrams as security element 5, which are inserted or applied in the banknote paper.

The light source 6 is an LED row 6 with a single row of LED elements 6a. It is assumed by way of example that the LED line 6 can emit different colors in succession in a predetermined manner. Alternatively, the individual LEDs 6a of the LED row 6 can also continuously emit white light. To limit the aperture, the LED line 6 has a SELFOC lens 9. This aperture limitation serves to illuminate only a narrow strip which extends in the transverse direction of the bank note 3. In order to produce diffraction phenomena, this lighting strip should be larger than the grating constant of the diffraction structure 5, but significantly narrower than the smallest structure of the security elements 5 to be resolved in the imaging. This has the advantage that the undesired influence of diffusely scattering areas of the banknote paper is reduced by the defined narrow illumination during the subsequent detection of the light emanating from the illuminated banknote. The sensors 7 and 8 can be CCD or CMOS line sensors that extend parallel to the LED line 6. Typically, the line sensors 7, 8 have a resolution of 0.2 to 1 mm. In the case of irradiation with colored light in time-division multiplex operation, the sensors 6 only require broadband detection sensitivity in the visible. Since only a single color is emitted and then recorded, color selection is not necessary in this case.

The first sensor 7 serves to detect light emanating from the direction of transport X. In the case of the banknotes according to FIG. 1, this is e.g. the light bent towards R1. The second sensor 8, on the other hand, is used to detect perpendicular to the transport direction X, i.e. light emanating in the transverse direction Y. In the case of the banknotes according to FIG. 1, this is e.g. the light diffracted towards R2. To image these light beams, the sensors 7 and 8 also have SELFOC lenses 9, preferably the same as the LED line 6.

In order to avoid an oblique arrangement of the built-in optics and sensors that is undesirable for the image generation described in more detail below, while at the same time being particularly compact in design, 9 prisms, particularly advantageously Fresnel prisms 10 with a sawtooth-shaped profile 11, are attached to the underside of the lenses. According to the desired deflection, the Fresnel prism 10 of the sensor has 7 steps transverse to the longitudinal direction of the SELFOC lens 9 and the Fresnel prism 10 of the sensor has 8 steps in the longitudinal direction of SELFOC. The flat surface of the Fresnel prism 10 always points to the object to be checked, ie to the bank note 3, since the beam path through the prism 10 is then more symmetrical. The existing dispersion of the prism 10 does not interfere in this case and can be neglected. The sensor 8 with associated imaging optics 9, 10 should be arranged as close as possible to the lighting optics 6, 9. The aperture of the SELFOC lens 9 of the sensor 8 is then selected such that the light emanating directly from the security element 5 through the plane of the LED line 6 perpendicular to the direction of transport X, ie in the direction R2, can also be detected by the sensor. The further sensor 7 is in turn spaced from the LED line 6 to such an extent that it can detect the light emanating at a predetermined angle α to be detected in accordance with an expected direction of diffraction.

Alternatively or additionally, for the detection of diagonal diffraction light, for example, a further sensor line with Fresnel prism can be present on a SELFOC lens with steps at 45 ° to the SELFOC longitudinal direction, the. Distance to the lighting is in turn predetermined by the desired deflection angle to be detected. If the banknotes 3 are alternatively transported with their long sides first, the arrangement of the sensors is rotated accordingly.

The length of the sensor surfaces, ie the measuring surfaces of the sensors 7 and 8, should at least correspond to the length of the structures to be metered, ie the security elements 5. The detector surfaces will preferably have a length corresponding to the maximum banknote length in the transverse direction Y. Although the sensors 7, 8 can be constructed identically, the case in which the second sensor 8 is longer than the first sensor 7 is shown in FIG. This may be necessary because of the deflection in the longitudinal direction of the sensor 7, so that depending on the arrangement of the security elements 5 to be tested, this is perpendicular to the transport direction X, ie. to actually be able to measure light emitted in the longitudinal direction of the sensor over the entire length. The test device 2 described above can be used as an example in the following manner. Banknotes 3 are individually transported past the checking device 2 by means of the transport device 4. In the process, the LED line 6 irradiates the bank note 3 transported beneath it in a row, ie in a strip shape over its entire width in the Y direction, with white light. The sensor line 7 detects light emanating from the bank note 3 at an angle α to the perpendicular direction of radiation B, and the sensor line 8 mounted close to the LED line 6 detects the light emanating from the illuminated bank note strip in its longitudinal direction, ie in the Y direction. The two ^' sensor lines 7, 8 are read out electronically at a frequency which is substantially greater than the rate at which the banknotes 3 are transported past the test device 2. The frequency should be so high that an image of the bank note 3 transported past can be generated by sequential reading of the sensor line 7 and / or 8, in which the structures, for example of the security element 5 to be recognized, can still be sufficiently resolved.

An image of the banknote 3 can thus be generated by computer-based evaluation of the sensor measurement signals from the sensors 7 and / or 8. If a real banknote 3 is present, the image acquisition and evaluation of the sensor line 7 should in particular result in the presence of the hologram 5 with the representation of the number "50" to be expected in the appropriate position and shape. Since in the case of diffraction structures the direction of diffraction depends on the frequency, the sensor lines 7, 8 can optionally also each include a color filter when irradiated with white light, in order to obtain only the image for one of the illumination frequencies or a frequency range. Alternatively, light of a single color can be irradiated and the color filters can be dispensed with. Furthermore, the intensity of the measurement signals of the line sensors 7, 8 can be normalized by a lighting control or by taking into account a variable which characterizes the illuminance of the LED line 6. Since, as has already been mentioned, the light intensity diffracted in the expected diffraction directions at the same illuminance is significantly greater than the intensity which is only diffusely scattered, for example, from normal paper, this standardization can make a difference to non-diffractive structures can also optionally be concluded on the state of wear of the banknote 3. This is possible even if only the signals of a single one of the two sensors 7, 8 arranged in different directions are evaluated.

If not only one, but several different security elements 5 are to be checked by means of the checking device 2, this can be done, for example, by the image acquisition described above, at least if the individual banknotes 3 differ only by the type of diffraction direction R1, R2 differentiate information presented. The use of white light also has the advantage that, by comparing the measured signal strengths with the expected reference values, such diffraction structures 5 can also be detected, the diffraction angles of which are only at least partially in the direction of the sensors 7, 8 for part of the illumination color bend solid angle range, which is predetermined by the aperture size of the SELFOC lenses 9.

Figure 4 shows an alternative embodiment, which differs from that of Figure 1 in that instead of a single line sensor 7 for detecting light diffracted in or against the direction of transport, three identically constructed line sensors 7, 7 ', 7 "are arranged side by side are. For the sake of clarity, the associated SELFOC lenses 9 with Fresnel prism 10 are not shown.

This exemplary embodiment with preferably two to four line sensors 7, 7 ', 7 "arranged next to one another has the advantage that, with a still very compact, simple and inexpensive construction, all line sensors 7, 7', 7" taken together can cover a larger solid angle range and thereby such as "7" with each other, diffraction structures with different diffraction characteristics, ^'can be identified and distinguished, and by comparing the measured values of the individual sensors 7. 7

In such a case in particular, lighting cannot be switched with a single color or a constant frequency spectrum, but with different ones. Colors in time multiplex operation are an advantage. Because of the wavelength dependency of the diffraction, it can be checked particularly reliably and unambiguously by comparing the measurement signals of the sensors 7, 7 ', 7 "for different colors for an expected diffraction characteristic. In this case, the data is recorded in time multiplex for different colors and the data lines then sorted according to the lighting color and evaluated separately.

If the bank note 3 to be checked is illuminated several times at high frequency by the different colors, for example the data lines corresponding to a green color are combined to form an image of the bank note 3 and the data lines corresponding to red illumination are combined to form a further image of the bank note 3 and with each other and / or compared with predetermined reference values or images. For example, by a previous one. Outline measurement of the bank note 3 to be checked, the presumptive position of the security elements 5 to be checked, is preferred only a limited measuring window lying around the security element 5 is evaluated.

A third exemplary embodiment is shown in FIG. 5. It differs from the previous one in that there is not one light source and several sensors for different directions of reflection or diffraction, but two light sources 16, 16 ′ arranged at different illumination angles for illuminating the bank notes 3 to be checked are. The light sources 16, 16 'are preferably constructed identically in order to ensure the most identical lighting conditions possible. The light sources 16, 16 'can be incandescent lamps, which irradiate the bank note in alternating time. Alternatively, LED lines 6 can again be used as light sources 16, 16 'in accordance with the previous exemplary embodiments.

To detect the light emanating from the banknote 3, a single sensor 17, e.g. again a line sensor 1 extending perpendicular to the transport direction X with an upstream SELFOC lens 9 and a deflection prism 10 'is present. The light source 16 'has the same angle to the perpendicular of the banknote plane as the light path to the sensor 17, while the second light source 16 has a larger angle, i.e. is arranged in a non-reflection direction.

In this case, by comparing the signal intensities, security elements 5 with an optically variable effect can again be checked. If the signals from sensor 17 are approximately the same for both lighting directions, ie for both light sources 16, 16 ', it can be concluded that a diffusely scattering area of bank note 3 has just been checked. Is the signal, when irradiated with the light source 16 ' considerably larger than for the light source 16, it can be concluded that there are directionally reflecting banknote areas. In the case of counterfeit banknotes, for example, this can be a ^' metal surface ^' , which is intended to simulate the presence of a hologram or another security element with an optically variable effect. If the two light sources 16, 16 'are now arranged in such a way that a high diffraction intensity of a real security element 5 that is to be recognized is just diffracted in a direction that is detected by the sensor 17 when illuminated by the sensor 17, so in this case When checking a real banknote 3, the signal values of the light source 16 are larger than in the case of a false banknote, and in some circumstances may even be larger than those of the light source 16 '.

One advantage of this embodiment, inter alia, is that only by comparing the signals from the sensor 17 for the illumination with the light source 16 in relation to the illumination with the light source 16 ', e.g. By means of a signal difference formation, statements about the state of the illuminated area can be made. So regardless of the exact location of banknote 3, i.e. even if the illuminated area of a bank note 3 to be checked is not exactly horizontal, but e.g. is slightly arched or kinked, the signal difference in diffusely scattering areas is approximately zero, while larger values of the signal difference indicate diffractive or directionally reflecting areas of the banknote.

FIG. 6 shows an alternative to FIG. 5, in which, in addition to a light source 16 ′ arranged in the direction of reflection in relation to the sensor 17, not only one but a plurality of further light sources 16 are present, which lie in non-reflection directions. The light sources 16, 16 'are preferably adjacent to one another and are all activated one after the other for illumination in accordance with different angles. With this, for example, banknotes 3 can also be distinguished, which bend at different angles. In such a case, sensor 17, for example, will each have a maximum intensity when illuminated with another of the plurality of light sources 16, 16 '.

Some of the possible exemplary embodiments for testing diffraction structures 5 as security elements 5 with an optically variable effect have already been described above. These principles can also be used to test other security elements with an optically variable effect. When testing security elements 5 with a color change effect, the following approaches are particularly preferred.

While the vertical illumination of the banknotes 3 is preferred for the inspection of diffraction structures 5, it has been shown that for the inspection of security elements 5 'with a color change effect, the illumination should take place obliquely to the BN vertical in order to be able to measure a sufficient color contrast. The azimuth of the lighting should e.g. in the case of line-shaped lighting, be oriented perpendicular to the line direction, as is exemplarily indicated in FIG. 7. Preferably, the oblique lighting in direction B 'is by a vertically arranged light source, not shown, such as e.g. an LED line, again arranged perpendicular to the transport direction X, takes place, the radiation of which, after passing through a SELFOC lens, is deflected obliquely by a Fresnel prism in the direction B 'onto the bank note 3 to be checked.

A lighting control or reference for normalizing the measurement signals proves not to be absolutely necessary if, for example, a color difference measurement is carried out for evaluation. To carry out such a measurement, bank note 3 in lighting direction and against the direction of light outgoing light can be detected. Corresponding line sensors can in turn be attached perpendicular to the transport direction X for this purpose. In FIG. 7, however, an alternative arrangement is shown, in which by means of a prism, in particular a 90 degree prism 13, both the light emanating from the bank note 3 in the direction of illumination RB and against the direction of illumination, ie in the direction of RG, through the same Prism 13 can be deflected over two sensor surfaces 15 via SELFOC lenses 14. An oblique installation of the sensors 15 can be avoided by the beam deflection.

In the case of line sensors 15 as sensor surfaces 15, two images of the security element 5 'can be obtained under two different observation directions RB, RG by sequentially reading out the line sensors 15 as the bank note 3 to be checked is transported past. Since the color impressions in the directions RB, RG are different for real banknotes 3, by selecting the appropriate filter or when irradiating with an associated color or white light, by evaluating the difference signals of the two sensors 15, the presence of a security element 5 'with a color change effect can be determined getting closed. High difference values will show up in the difference image in the areas in which the color change effect occurs. The size of the signals or their difference can in turn also serve as a criterion for checking the state of use of the banknotes 3.

Instead of using line-shaped lighting and / or line sensors, banknote 3 can alternatively also be illuminated over a large area and sensors with two-dimensional detector surfaces can be used in order to be able to directly obtain an image of the illuminated area. FIG. 8 shows a further exemplary embodiment, which differs from that of FIG. 7 in that, instead of the 90 degree prism 13 with a triangular cross section, a space-saving Fresnel prism 13 'with a step profile is used, which is designed such that both the direction RG , as well as the light coming out in the direction RB is imaged by a common SELFOC lens 14 'onto a single sensor 15', such as a CCD camera 15 'with a two-dimensional detector surface. This structure is particularly compact and simple.

In the embodiments according to FIGS. 7 and 8, two images are generated by means of a symmetrical beam path of the light rays emanating from the bank note 3, which images are particularly simple, e.g. can be compared by pixel-wise difference formation. The variants with a prism for generating two images corresponding to different viewing angles are preferably also suitable as handheld devices for checking associated security elements, the eyes of the viewer taking over the function of sensors 15, 15 '.

The device can thus comprise a housing with opaque walls, in which the prism and / or the light source are fastened. The housing is preferably provided with an opening for the entry of rays for illuminating the area to be tested and / or an opening for the exit of the rays passing through the prism. Furthermore, the housing can have one or more walls which protrude beyond the prism in order to be able to ensure a predetermined distance from the security element to the prism by placing the housing on a security element to be tested. It should be noted that in the exemplary embodiments in FIGS. 7 and 8, when the light is illuminated with multicolored or white light, a color selection by the sensor 15, 15 'is necessary in different directions due to the color differences to be measured. Illumination with a single color, however, is already sufficient if the security element 5 'with a color change provides a sufficiently large contrast for these under the various detected directions of observation RB, RG.

FIG. 9 shows a seventh exemplary embodiment in which the polarization behavior of security elements 5, 5 'is used to check their authenticity. As was mentioned, the polarization is retained when reflection or diffraction of linearly polarized light on security elements 5, 5 'with ^* optically variable effect and on intaglio profiles, while this is not the case with scattering on paper or with offset printing.

Using a light source 20, a linearly polarized light beam is directed perpendicularly in the direction B onto the surface of the bank note 3. The light emanating from the illuminated banknote 3 is detected obliquely in two symmetrical directions. For this purpose, sensors 21, 21 'of identical construction are arranged at a distance from one another, each of which by means of a

SELFOC lens 9 and a deflecting prism 10 ', light is directed at an angle γ. The first sensor 21 comprises a polarization filter which transmits light which is polarized in the same way as the illuminating light, while the other sensor 21 'only transmits light polarized perpendicular to it. The sensors 21, 21 'are preferably connected to the inputs of a differential amplifier 22, the output signal of which is a measure of the change in polarization. In the presence, for example, of security elements 5, 5 'with an optically variable effect, the signal difference will be particularly high, for example. Finally, FIG. 10 shows a last exemplary embodiment, the lighting and sensor arrangement of which essentially corresponds to that of FIG. 9. However, the test device 2 of FIG. 10 is not designed to test polarization properties. For this reason, the bank notes 3 to be checked are not irradiated with linearly polarized light in this exemplary embodiment, and the sensors likewise do not have a polarization filter for detecting light of a specific polarization direction. In addition, the test device 2 is not used to test security elements 5, 5 'with an optically variable effect, but in particular for the detection of surface profiles 25 of banknotes 3. Such profiles 25, which are shown greatly enlarged in FIG. 10, can be, for example, line patterns or the like which are produced by intaglio printing, with the profiles extending, for example, perpendicular to the direction of transport X. The bank note 3 is illuminated with a light source 30 arranged transversely to the transport direction in the direction B in an area that should be narrower than the cross section of a profile line. Depending on whether the light beam hits a hill or a valley or one of the flanks of the profile 25, the light beam is preferably reflected by the profile 25 in a different direction. The light reflected in two different oblique directions is in turn detected by two sensors 31 and 31 'arranged in different oblique directions with deflection prisms and SELFOC lenses. A difference of the signals is formed in the unit 22. The difference signal then again allows for the shape of the surface profile 25, taking into account the transport speed of the bank note 3 to be checked.

It has been found that a recognition of such intaglio printing profiles by spot lighting and thus the scanning of a individual track of bank note 3 running in the transport direction X is not sufficient. A full-surface detection is necessary for the reliable and precise detection of the shape of such surface profiles. Therefore, the light source 30 and the two sensors 31, 31 'are particularly preferably cellular light sources 30 and sensors 31, 31'. In the example of FIG. 10, these can extend perpendicular to the sheet plane, ie perpendicular to the transport direction X in the direction Y.

For example, the following should be noted in comparison to the detection of diffraction structures. To generate diffraction phenomena, it is imperative that the diffraction structures are illuminated in an area that is significantly larger than their lattice constant. In contrast, the intaglio printing profiles 25 should preferably be illuminated in an area that is smaller than the dimensions of the. structures to be recognized, in particular e.g. is smaller than the line spacing a of the profile 25.

It was described above that the pair of sensors 31, 31 'extends essentially perpendicular to the direction of transport. To identify other profile structures, these or additional sensor pairs 31, 31 'could extend in other directions. Furthermore, not only two, but a plurality of sensors 31, 31 ′ can in turn be arranged in parallel in order to be able to cover a larger solid angle range.

Finally, it should be emphasized again that several of the test devices 2 mentioned above can also be combined, for example by a

Test device 2 above the transport plane of the banknotes 3 for testing diffraction structures 5 located on the top of the banknotes 3 and a further test device 2 below to the transport plane of the Banknotes 3 for checking security elements 5 'located on the underside of the banknotes 3 with a color change effect is arranged.

In Figure 11, a bank note is sketched as data carrier 41. The printed image of a banknote is typically a superimposition of several printed images, each of which is created using different printing methods. The banknote shown shows, for example, a printed image 42 which represents the number 5. This printed image 42 is converted into line intaglio printing technology, which means that different brightnesses are reproduced by line screens with varying line spacing or line width. The lines have a symmetrical profile. There is also a background pattern 43 of fine lines generated in offset printing and a serial number 44 applied in letterpress printing. Furthermore e.g. still partial areas are provided, which are created in screen printing technology.

The imprint 45 according to the invention, which is intended to represent a portrait and has asymmetrical intaglio printing profiles, is provided in a portion of the banknote in the example shown here and is only shown schematically. The exact description of the printed image according to the invention, the printed data carrier and the printing plate used is explained with the aid of the following examples and figures.

FIG. 12 shows the cross section along the line AA through the banknote in FIG. 11. The substrate 46, in this case cotton paper, is slightly deformed by the printing process. In addition to cotton paper, any other suitable substrate, such as paper based on cellulose or synthetic fiber, can be used. The colored areas and / or lines 47 from which the motif is composed can be seen on the paper surface. Because of the depressions in the printing plate, which already have an asymmetrical profile, the color range which can be transferred to the paper itself has an asymmetrical profile according to the invention. It can be clearly seen in FIG. 12 that the flanks of the color peaks 47 have different inclinations, so that, for example, when polarized light is irradiated perpendicularly, it can be reflected in different directions and detected accordingly.

FIG. 13 shows a section of the intaglio printing plate 48 according to the invention in cross section, with which a print image as shown in FIG. 12 is generated. The surface of the printing plate has depressions e.g. in the form of lines milled into the plate with an asymmetrical profile. The original, i.e. the surface before milling was dotted. Line indicated. Depending on the engraving depth, width and milling angle, the reflection effect in the value document can be precisely adjusted to the required requirements.

It should be noted that a relief on the surface of the data carrier does not match the engraving depth of the printing plate. The surface relief shown in FIG. 12 is idealized. The surface relief created by the printing is composed of a compaction of the substrate material and the color layer application. The overall height of the relief is related to the normal, ie unprinted and unprinted, data surface. In practice, the relief created on the substrate and the engraving in the printing plate differ very clearly from one another. The reason for the deviations between engraving depth and relief height is due to the fact that the data carrier is not pressed down to the bottom of the printing plate engraving during the printing process and the color present in the depressions of the printing plate is not completely on the Disk is transferred. Accordingly, the engraving depth of the printing plate for relief-like structures is in the range from approx. 40 μm to 250 μm, preferably in the range from approx. 55 μm to 150 μm. They produce relief structures in the range from approx. 5 μm to around 100 μm, preferably 25 to 80 μm. Whether an engraving depth in the border area on the surface of a data carrier leads to a relief-like or rather flat print depends in individual cases on the steepness of the edge of the engraving, the nature of the substrate to be printed (strength, plastic deformability) and the color properties.

Since, as already mentioned, the relief height achieved in the printing result depends not only on the engraving depth of the printing plate, but also on the properties of the substrate and the printing ink, in extreme cases an engraving depth of 40 μm can already lead to a relief-like print image, while in others material and printing parameters, an engraving depth of 50 μm can still lead to a flat print image. In each specific application, however, the graphics leading to relief-like printed image areas are always deeper than those that produce so-called flat, tactile, imperceptible image areas.

Claims

Patent claims

1. Device (1) for processing value documents (3), with a test device (2) for checking a security element (5, 5 ', 25) of the value document (3), in particular for checking the type and / or Authenticity and / or fitness for circulation of a security element (5, 5 ') with an optically variable effect, characterized by one or more light sources (6, 16, 16', 20, 30) for illuminating the security element, one or more sensors (7, 7 ' , 8, 15, 15 ', 17, 21, 21', 31, 31 ') for detecting the light coming from an illuminated area of the security element in one or more different directions (RB, RG, Rl, R2), which do not correspond to the direction of reflection (B), and a means (7, 7 ', 8, 15, 15', 17, 21, 21 ', 31, 31') for capturing images of the illuminated area, the test depending on signals from the Sensors for detecting light emanating in the non-reflection direction and the means for image acquisition is carried out.

2. Device according to claim 1, characterized in that the means (7, 7 ', 8, 15, 15', 17, 21, 21 ', 31, 31') for image acquisition to generate one or more images of the illuminated area , each of which corresponds to a different viewing angle, and / or the means (7, 7 ', 8, 15, 15', 17, 21, 21 ', 31, 31') is a separate sensor or at least one of the sensors (7 , 7 ', 8, 15, 15', 17, 21, 21 ', 31, 31'), which are used for the detection of light emanating in the non-reflection direction.

3. Device according to at least one of the preceding claims, characterized in that the device further comprises a transport device (4) in order to transport the documents of value (3) to be checked individually past the testing device (2) in a transport direction (X).

4. The device according to at least one of the preceding claims, characterized in that the light sources line-shaped light sources (6, 16, 16 ',

20, 30) for line-shaped illumination of the value document and / or the sensors are line sensors (7, 7 ', 8, 15, 15', 17, 21, 21 ', 31, 31').

5. The device according to at least one of the preceding claims, characterized in that the light source and / or the sensors each extend transversely, in particular perpendicular to the transport direction (X).

6. The device according to at least one of the preceding claims, characterized in that the length of the illuminated surface of the security element (5, 5 ') and / or the length of the measuring surface of the sensors is greater than or equal to the length of the value documents to be measured in the same direction is.

7. The device according to at least one of the preceding claims, characterized in that the light source for the vertical illumination of the security elements, in particular for testing diffraction structures (5) as security elements or for oblique illumination of the security elements, in particular for testing security elements (5 ') with color change effect.

8. The device according to at least one of the preceding claims, characterized in that, in particular in a vertical direction (B) illuminating light source (6), a line sensor (8) close to the light source for detecting perpendicular to the transport direction (X) of the outgoing light is arranged to be checked value document (3).

9. ^' Device according to at least one of the preceding claims, characterized in that a further line sensor (6) for detecting the in a certain angular range (α) from in or against the transport direction (X) light is arranged.

10. The device according to at least one of the preceding claims, characterized in that a plurality of further line sensors (6, 6 ') are arranged side by side, each of the further line sensors each for detecting a different direction (α) from in or against the transport direction ( X) serves outgoing light.

11. The device according to at least one of the preceding claims, characterized in that, in particular in the case of a light source illuminating in the oblique direction (B '), a single sensor (15') or at least two separate sensors (15) for detecting in and of light emanating from the illuminated bank note (3) against the oblique direction of illumination.

12. The device according to at least one of the preceding claims, characterized in that in the test controlled variables and / or measured variables, e.g. the actual illuminance, the light sources for normalizing the measurement signals of the sensors are taken into account.

13. The device according to at least one of the preceding claims, characterized in that the light source and / or the sensors SELFOC lenses (9, 14). for imaging and / or aperture limitation.

14. The device according to at least one of the preceding claims, characterized in that the light source and / or the sensors for beam deflection a prism, in particular a Fresnel prism (10, 13 ') or a prism with a triangular cross section, such as e.g. have a 90 degree prism (10 ').

15. The device according to at least one of the preceding claims, characterized in that a flat surface of the Fresnel prism (10, 13 ') faces the security element to be tested (5, 5', 25)

16. The device according to at least one of the preceding claims, characterized in that the light source is designed for lighting with white light or for lighting with several colors in time-division multiplexing.

17. The device according to at least one of the preceding claims, characterized in that there are a plurality of light sources (16, 16 ') for illuminating the

Security elements in at least two different lighting angles exist.

18. The device according to at least one of the preceding claims, characterized in that the device (1) is a banknote counting and / or sorting and / or deposit and / or payment device.

19. The device according to at least one of the preceding claims, characterized in that the light source and / or the sensors have color filters and / or the evaluation device is designed for spectral analysis in order to be able to determine different color components, for example by forming a color difference, of the sensor signals.

20. The device according to at least one of the preceding claims, characterized in that the light source (20) emits linearly polarized light and the sensors (21, 21 ') are designed for detecting the polarization state of the light emanating from the document of value in order to due to the polarization behavior of the To be able to infer security elements based on their type and / or authenticity and / or condition.

21. The device according to at least one of the preceding claims, characterized in that the device further comprises a device for determining the position and / or the outline of the value document and / or its security element in relation to the test device, thereby thereby the measurement window of the sensors to be able to determine depending on the location or the outline.

22. The device according to at least one of the preceding claims, characterized in that the test device (2) checks the security documents (3) as security elements, in particular surface profiles (25) generated by intaglio printing.

23. The device according to claim 22, characterized in that the surface profile (25) generated by intaglio printing is asymmetrical.

24. Method for processing documents of value (3), with an examination of a security element (5, 5 ', 25) of the document of value, in particular an examination of the type and / or authenticity and / or fitness of a security element (5, 5') with Optically variable effect, characterized in that the test is carried out automatically in one or more different directions (RB, RG, Rl, R2) as a function of a machine detection of the area illuminated by the security element Light which does not correspond to the direction of reflection (B) is carried out in combination with an image capture of the illuminated area.

25. The method according to claim 24, characterized in that the documents of value to be tested are individually transported past a test device (2) and illuminated in the form of lines and by means of line sensors that in the different directions (RB, RG, Rl, R2) outgoing light is detected.

26. The method according to claim 24 and / or 25, characterized in that the documents of value in particular for the inspection of diffraction structures (5) are illuminated vertically and / or for the inspection of security elements (5 ') with a color change effect.

27. The method according to at least one of claims 24 to 26, characterized in that for checking the security element in oblique lighting, in and against the oblique direction of illumination (B ') from the illuminated document of value light is detected.

28. The method according to at least one of claims 24 to 27, characterized in that the documents of value are illuminated with white light or with several colors in time-division multiplexing with one or more light sources (16, 16 ') in at least two different illumination angles.

29. The method according to at least one of claims 24 to 28, characterized in that after illumination of the value documents with linearly polarized light, the polarization state of the light emanating from the value document is measured in order to, on the basis of the polarization behavior of the To be able to infer security elements based on their type and / or authenticity and / or condition.

30. The method according to at least one of claims 24 to 29, characterized in that the test serves to test surface profiles (25) of the value documents (3), which were generated in particular by intaglio printing.

31. The method according to claim 30, characterized in that the surface profile (25) produced by intaglio printing is asymmetrical.

32. document of value with at least one security element produced in intaglio printing, characterized in that the color layer applied in intaglio printing has an asymmetrical surface profile.

33. Printing plate for intaglio printing with at least one engraved area in the printing plate surface, characterized in that it has an asymmetrical profile.

34. Printing plate according to claim 33, characterized in that the engraving flanks have different inclinations with respect to the printing plate surface.

35. A method for producing a value document according to claim 31, comprising the following steps: a) providing a printable substrate b) producing a intaglio printing plate according to at least one of claims 33 or 34 and c) printing the substrate with the printing plate produced in step b).