EP3221853B1 - Method and device for capturing of emitted light and method for the manufacturing - Google Patents

Description

The invention relates to a device and a method for detecting light emitted by a security document, and a method for producing such a device.

It is known to use an optical system to detect light which is emitted, transmitted, reflected or scattered by a surface of a security document. Depending on the properties of the light detected in this way, an authenticity check can be carried out in particular.

Optical systems which are used to detect the emitted light regularly consist of a number of lenses which image the surface or a partial area of the surface of the security document in a detector plane of an optical sensor.

Since the light intensity, i.e. the amount of light per detector surface, decreases with the square of the measuring distance, which, for example, denotes a distance between an entrance surface of the optical system and the surface to be imaged, optical systems with a large aperture and a small measuring distance are used for weakly luminous surfaces in order to capture as much light as possible. In this case, the aperture designates a diameter of an entry opening of the optical system, in particular the diameter of an entry lens. The entry surface can be the same as the detector surface, in particular if light from the surface hits the detector directly, ie without radiating through further optical elements.

The larger the lens and the smaller the measuring distance, the larger the solid angle from which light can be recorded. However, small measurement distances, in particular measurement distances that are smaller than a focal length of an entry lens of the optical system, lead to light losses in the system due to beam divergence, with the light being able to be absorbed by the housing, for example.

Such systems also lead to an increased dependency of the measurement result both on the measurement distance and on a position of the security document relative to an optical axis of the optical system. Thus, using such an optical system may require high positioning accuracy.

Furthermore, each lens of the optical system causes small reflections and thus light losses. A further disadvantage consists in the high construction costs and the large installation space requirement of these optical systems with lenses.

the DE 27 13 396 A1 discloses a method and apparatus for marking or identifying a body containing or carrying luminescent material.

the EP 2 573 739 A1 discloses a method for authenticating security documents, which method is directed to a simple device and method for authenticating an optically variable unit.

the GB 2 507 575 A discloses an authentication device for authentication of a security feature.

the EP 2 043 058 A2 discloses a bill identification device provided in automatic vending machines and money changing machines.

The technical problem arises of creating a device and a method for detecting emitted light from a security document and a method for producing such a device, which enable a desired amount of light to be detected, but at the same time require space, weight, construction costs and light losses and positioning sensitivity reduce.

The technical problem is solved by the objects with the features of claims 1, 12 and 13. Further advantageous configurations of the invention result from the dependent claims.

A basic idea of the invention is to design a device for detecting light emitted by a security document without a lens. Next, a light channel can be provided with a free-body shape, the free-body shape being chosen such that a surface of the security document to be imaged with a predetermined geometry through the light channel of the device onto an optical Sensor, in particular on its active surface, is imaged with a predetermined geometry. Thus, the light emitted, reflected or scattered by the surface to be imaged can be directed completely or to a large extent through the light channel onto the active surface.

A device for detecting emitted light from a security document is proposed. In this case, the light is emitted from the security document, in particular from the surface of the security document. The emitted light can denote diffusely scattered light, reflected light, transmitted light or emitted light.

Any document that is a physical entity that is protected against unauthorized manufacture and/or tampering can be referred to as a security document protected by security features or elements. Security features are features that at least make falsification and/or duplication more difficult than simple copying. Physical entities that include or form a security feature can be referred to as security elements. A security document can include multiple security features and/or security elements. As defined here, a security document can always represent a security element. Examples of security documents, which also include documents of value that represent value, include, for example, passports, ID cards, driver's licenses, ID cards, access control ID cards, health insurance cards, banknotes, postage stamps, bank cards, credit cards, smart cards, tickets and labels.

In this case, the security document can in particular contain or have light-scattering, photoluminescent/phosphorescent elements or electroluminescent elements, in particular pigments. These enable an authenticity verification depending on emitted photo- or electroluminescent radiation when such a luminescent element is excited, e.g. by light and/or an electric field. In such a case, however, an optical imaging of a partial area of the surface is not absolutely necessary for the authenticity verification, but only the detection of the amount of emitted light.

In this case, the device can in particular be part of a device for checking the authenticity of the security document. Such a device enables the authenticity of the security document to be verified, in particular by evaluating properties of the emitted light.

The device comprises at least one light guide body. As explained in more detail below, the light-guiding body can be designed as a coated glass body or can include such a body. Alternatively, the light-guiding body can be designed as a solid profile with at least one light-guiding channel filled, for example, with air or another transparent material.

The light-guiding body has at least one light channel or forms one. The light channel has an entry opening and at least one first exit opening.

The entry opening and the first exit opening are thus connected by the light channel. In this context, the entry opening designates an opening through which the light emitted by the security document enters the light channel. The exit opening correspondingly designates an opening through which the light that has entered and is radiated through the light channel exits or can exit from the light channel.

Furthermore, the wall surface or wall surfaces enclosing the light channel are designed to be completely reflective. This means that no light can escape from the light channel through the wall surface/s. For example, the wall surface/s can be designed to be reflective.

Furthermore, the light guide body is designed without lenses. This means that the light-guiding body does not include a lens or an element that has an optically equivalent effect. In particular, the light guide body does not include a lens or an optically equivalent element that is used for optical imaging and/or light bundling.

The feature that the light-conducting body is designed without lenses can mean that the light channel is designed in such a way that a direction of the light entering the light channel through the entry opening is changed exclusively by reflection on the wall surfaces. Alternatively or cumulatively, the feature that the light guide body is designed without lenses can mean that a beam refraction, beam focusing and/or beam scattering of the light entering the light channel through the entry opening takes place exclusively through reflection on the wall surfaces. It is therefore not possible to arrange an optical element for changing the beam direction of the light, for beam refraction, for beam bundling and/or for beam scattering in and/or along the light channel.

However, the fact that the light-guiding body is designed without lenses does not necessarily mean that one or more optical elements, e.g. mirrors or beam splitters, are included in the light-guiding body. However, such optical elements are not used for light bundling and/or optical imaging.

In particular, the inlet opening and/or the first outlet opening can be designed without a lens. This means that at the inlet and/or outlet opening there is no change in the beam direction of the light, no beam refraction, no beam bundling and/or no beam scattering, in particular by an optical element, takes place.

The light channel can thus be in direct optical connection with an environment via the entry opening. This can mean that light from the environment can radiate into the light channel without changing properties. Furthermore, the light channel can be in direct optical connection with an environment via the exit opening or with an optical sensor, which will be explained in more detail below. This can mean that light can radiate from the light channel into the environment or onto the optical sensor without changing properties.

In other words, the light-guiding body can be formed without an imaging element, with the light-guiding body not comprising any element for optical imaging. However, this does not preclude the light guide body from guiding the beam to detect light.

Further, a shape and an area of the entrance opening is different from the shape and an area of the exit opening. For example, an inlet opening can be rectangular and an outlet opening can be circular or vice versa. Thus, for example, rays from an emitting strip of the security document can be directed onto a circular active surface without major light losses, in particular due to multiple reflection.

This has the advantage that light emitted by the surface of the security document can be collected and guided through the light channel to an optical sensor, for example. Properties of the light detected by the optical sensor can then be determined and evaluated. In order to determine these properties, no optical imaging of the surface or part of it is required. In particular, optical imaging is not required if only the amount or intensity of the light emitted from areas of the surface of the security document is to be detected.

The proposed device advantageously enables the emitted light to be recorded with as little loss as possible, with construction costs and the need for construction space being minimized because of the lenses that are not required.

In a further embodiment, the light channel is designed as a free-form body. In particular, a design of the free-form body, in particular the design of the entry and exit openings, can be selected as a function of a geometry and position of a radiating surface (surface to be imaged) and as a function of a geometry of an active surface of an optical sensor. In particular, the entrance opening to any geometry and / or position of the radiating Surface and the outlet opening are adapted to the geometry of the active area of a sensor.

The light channel, in particular the geometric shape of the free-form body and the geometry of the entry and exit openings, can be selected in such a way that a surface of the security document to be imaged with a predetermined geometry passes through the light channel of the device onto an optical sensor, in particular on its active surface. is mapped with a predetermined geometry. For example, the area to be imaged can be rectangular, square, circular, or oval. Of course, other geometric shapes are also conceivable. In particular, the active area can be rectangular or square. Other geometric shapes are also conceivable here.

If the device is placed on the security document to be detected or arranged at a predetermined distance above its surface, the light emitted by the surface to be imaged, e.g. emitted, reflected or scattered, or a predetermined percentage, e.g. more than 90 % or more than 95% of which are directed through the light channel onto the active surface.

The shape of the light channel can thus be selected depending on the geometry of the area to be imaged and the active area of the desired optical sensor. In this way, a reliable optical detection of a surface to be imaged with a predetermined geometry and with a desired optical sensor can advantageously take place. If an optical sensor with a predetermined geometry is to be used, the shape of the light channel can advantageously result in good optical detection for different surfaces to be imaged. A flexible adaptation of the optical detection can thus take place.

A free-form body can in particular have an asymmetrical shape or an irregular contour.

In a further embodiment, the device comprises at least one optical sensor, the optical sensor being arranged in or on the first outlet opening. In this case, the optical sensor can comprise or have an active surface, in which case the optical sensor can generate an output signal as a function of the light radiating or incident on this active surface.

The arrangement of the optical sensor on or in the first exit opening can mean that the light guided through the light channel to the first exit opening and/or the light exiting from the first exit opening is completely or at least to a predetermined proportion, e.g. to at least 90% the active surface radiates or falls.

In this case, the active surface can have a predetermined geometry and/or predetermined dimensions. In this case, a geometry of the outlet opening and/or dimensions of the outlet opening can correspond to the geometry or dimensions of the active surface.

The active surface at the exit opening can also be arranged inside the light channel. This can mean, for example, that the light channel encloses the active surface of the optical sensor at its exit opening. In this case, there can be no distance or a predetermined (small) distance between the wall surface of the light channel and the active surface. If there is no distance, the wall surface of the light channel can be arranged flush with the edges of the active surface at the first exit opening. The light channel can thus be in direct optical connection with the active surface of the optical sensor via the exit opening. In this case it can be possible that no light emerges from the first exit opening into an environment. However, the optical sensor, in particular its active surface, can also be arranged outside of the first exit opening.

Overall, however, the advantageous result is that the light losses are reduced.

According to the invention, the light channel has at least one branch into a first partial channel with the first exit opening and at least one further partial channel with a further exit opening. For example, the light channel can comprise a main channel section between the entrance opening and the branch. Furthermore, the light channel can comprise a first partial channel section between the branch and the first exit opening. Correspondingly, the light channel can comprise a further sub-channel section between the branch and the further exit opening. Of course, the light channel, in particular at least one of the sub-channels or the main channel section, can have a further branch.

This has the advantageous result that light radiated into the light channel can be spatially divided in order, as explained in more detail below, to enable spatially separate detection of the light, e.g. by a plurality of optical sensors arranged spatially separately.

In a further embodiment, the device comprises a beam splitter, which splits light, in particular from the main channel section, in a predetermined ratio onto the first sub-channel and the at least one further sub-channel, e.g. deflects or irradiates them. The beam splitter can be arranged at/in front of the branch. For example, the beam splitter can direct light from a main channel section of the light channel into the first sub-channel and into the at least one further sub-channel in a predetermined ratio.

The predetermined ratio may be a light amount ratio or light intensity ratio. The ratio can be determined as a function of the light properties to be detected and/or the sensitivity of optical sensors at the exit openings of the partial channels. Preferably, the predetermined ratio may be 1:1. Of course, however, other conditions are also conceivable.

In this case, the beam splitter designates an optical element by which a beam direction of at least part of the light radiated onto the beam splitter is changed. In particular, a beam direction of a first portion of this light cannot be changed by the beam splitter, with a beam direction of the remaining portion is changed by the beam splitter. Of course, however, the jet directions of both components can also be changed.

This advantageously results in the most reliable possible splitting of the light for forwarding in different sub-channels.

In an alternative embodiment, the branch is designed in such a way that the light at the branch, in particular the light from the main channel section, is divided in a predetermined ratio between the first and the at least one further sub-channel. For example, the branching can be designed in such a way that the light from a main section of the light channel shines in a predetermined ratio into the first sub-channel and into the at least one further sub-channel. This results in an advantageous splitting of the light without a beam splitter. The predetermined ratio can in turn designate a light quantity or light intensity ratio. Preferably the ratio is 1:1. Of course, however, other conditions are also conceivable. For example, the branching can be provided by a suitable design and/or a suitable geometric course of the wall surface(s).

This advantageously results in a simple provision of the light branching.

In a further embodiment, the device comprises at least one further optical sensor, the at least one further optical sensor being arranged in or on the first outlet opening or in or on the at least one further outlet opening.

In a first alternative, the first and the further optical sensor can be arranged in or on the first outlet opening. In this case, the two optical sensors can be used to detect and optionally determine properties of the light that differ from one another.

For example, the first and the further optical sensor can be arranged spatially adjacent to one another in or on the first outlet opening.

The arrangement of the optical sensors on or in the first exit opening can mean that the light guided through the light channel to the first exit opening and/or the light exiting from the first exit opening is completely or at least to a predetermined proportion, e.g. to at least 90% the totality of the active surfaces radiates or falls.

In this case, the active surfaces can be arranged inside or outside the light channel. Preferably there can be no or only a predetermined (small) distance between edges of the active surfaces of the two sensors. The active surfaces can be arranged in such a way that the light directed towards the first exit opening radiates onto the active surfaces in a predetermined ratio, in particular in equal or unequal parts.

As already explained above, a geometry of the outlet opening and/or dimensions of the outlet opening can also correspond in this case to the geometry or dimension of the active areas, for example an envelope of the active areas. This can mean that the light channel encloses the active surfaces of the optical sensors at its first exit opening. There can be no or a predetermined (small) distance between the wall surface of the light channel and the active surfaces. If there is no distance, the wall surface of the light channel can be arranged flush with the active surfaces at the first exit opening. The light channel can thus be in direct optical connection with the active surfaces of the optical sensors via the exit opening.

In the second alternative, the additional optical sensor is spatially separated from the first optical sensor. This advantageously reduces mutual influence of the optical sensors, which can disadvantageously falsify an output signal from the sensors.

According to the explanations regarding the arrangement of the first optical sensor on or in the first exit opening, the further optical sensor can be arranged on or in the further exit opening in such a way that the light guided through the light channel to the further exit opening and/or the light emerging from the further exit opening Light shines or falls completely or at least to a predetermined proportion, for example at least 90%, onto the active surface of the further optical sensor.

In this case, the further optical sensor can be arranged inside or outside the further partial channel. Furthermore, a geometry and/or dimension of the additional exit opening can be adapted to the geometry and/or dimension of the active surface of the additional optical sensor. In this regard, reference is made to the corresponding previous statements.

In a further embodiment, the first optical sensor is a spectral sensor and the at least one further sensor is a light quantity sensor. This advantageously results in properties of the light that are different from one another being detected by sensors that are different from one another. This advantageously results in a more precise detection and determination of these properties.

In a further embodiment, a cross section of the light channel decreases from the entry opening towards the at least one exit opening. In this case, the cross section can designate a cross-sectional area or a diameter, in particular a maximum diameter, of the light channel. Alternatively, the cross section of the light channel increases from the entry opening to the at least one exit opening. In this case, however, it is not ruled out that the light channel has sections with a constant cross section. A size of the cross section can be detected, for example, along a central axis of the light channel. The cross section can change along the light channel, e.g. non-continuously, in particular abruptly, continuously or in a differentiable manner. In particular, a cross section of the inlet opening can be larger or smaller than a cross section of the at least one outlet opening. This advantageously results in a desired concentration or a desired distribution of the light radiated into the light channel.

In a preferred embodiment, at least a section of the light channel, in particular the entire light channel, is designed in the shape of a truncated cone or a truncated pyramid. Alternatively or cumulatively, at least a partial section of the at least one partial channel, in particular the entire partial channel, can be designed in the shape of a truncated cone or a truncated pyramid. This does not rule out that at least one further sub-section of the light channel and/or the at least one sub-channel is designed in the shape of a cylinder or cuboid. This advantageously results in the simplest possible mechanical manufacture of the light guide body.

It is further described that the light channel can be designed in such a way that the light propagates from the entry opening to the at least one exit opening without back reflection.

This can mean that a direction of the light radiated through the entry opening is only changed in the light channel in such a way that the beam direction in each section of the light channel includes a portion that is oriented parallel to a center line or central axis of the light channel and in the direction of the exit opening, is oriented in particular from the inlet opening towards the outlet opening. In this case, however, it is not excluded that the beam direction has a further proportion transverse to this center line or central axis. However, it is essential that the jet direction has no or only a negligibly small proportion in a direction that is oriented parallel to the center line or central axis and in the direction of the entrance opening.

Alternatively, the light channel is designed in such a way that an intensity of the radiation reflected back during the propagation of the light from the entry opening to the at least one exit opening is less than a predetermined threshold value. In particular, the intensity of the back-reflected radiation can be less than or equal to 10% of the intensity of the light radiated in through the entry opening.

This advantageously results in reliable detection.

It is further described that a wall surface inclination and/or a length of the light channel and/or at least one partial channel can be selected as a function of a dimension of the entry opening and a dimension of the exit opening in such a way that back-reflection-free propagation is ensured. In this case, the inlet and outlet opening designates the inlet opening of the respective channel section, ie for example the main channel section or partial channel section explained above.

Here, the dimension of the entry opening depending on a dimension of the surface to be detected of the security document and / or a desired or necessary distance of the entry opening from this surface and a desired angle of incidence of the light emitted by the surface to be detected on the Entry opening to be determined. In this case, the angle of incidence can be an angle relative to a line which is oriented perpendicularly to the entry opening, in particular an angle relative to an optical axis of the entry opening.

The dimension of the exit opening can be dependent on the dimension of the active surface of the optical sensor. In particular, the dimension of the outlet opening can correspond to the dimension of the active surface or be greater than the dimension of the active surface by a predetermined (small) amount.

The wall surface inclination can be relative to a central axis or center line of the light channel. If the (partial) channel has a curve or a kink, the wall surface inclination can be given relative to a tangent to the central axis or center line. However, it is also possible that in this case the wall surface inclination is given relative to the optical axis of the entrance opening of the light channel or an entrance opening of a sub-channel. In this case, the center line of the inlet opening refers to a line oriented perpendicularly to an inlet surface, which intersects the inlet surface at its geometric center.

The panel slope may vary along the light channel, particularly within a predetermined slope interval. This can mean that the wall surface inclination along the light channel and/or the at least one partial channel is greater than or equal to a predetermined minimum inclination and/or smaller than or equal to a maximum inclination. In this case, the wall surface inclination can change along the light channel non-continuously, in particular abruptly, continuously or preferably in a differentiable manner. The inclination can be given in particular by an angle between the central axis or center line and a line of intersection through the wall surface, the line of intersection lying in a plane of intersection spanned by the central axis or center line and a vector perpendicular to the central axis or center line with the vector being oriented from the central axis or center line towards the wall surface. In particular, the angle can be given in this case by the angle between the central axis or center line and a tangent to the line of intersection at the point of intersection of the line of intersection with the vector.

Depending on the geometric design of the light channel, the beam direction of the light radiated into the light channel, in particular in the case of multiple reflection, can change in such a way change in that along the light channel the proportion oriented parallel to the center line or central axis of the light channel and in the direction of the exit opening decreases. Thus, the wall surface inclination and the length of the light channel can be selected in particular in such a way that this proportion along the light channel is greater than zero in each section.

In a further embodiment, the wall surface inclination changes along the light channel and/or along at least one partial channel. This advantageously results in a further minimization of light losses.

In a further embodiment, the light channel is formed by a light-transmitting material. The propagation of the light in the light channel takes place inside the body. In particular, the light channel can be formed by a glass or plastic body. In this case, the glass or plastic body can be coated, with the coating providing completely reflective wall surfaces of the glass or plastic body. Alternatively, there is air in the light channel.

This advantageously enables the light channel to be produced easily with the desired properties.

A method for producing a device for detecting emitted light from a security document is also proposed. In this case, at least one light-guiding body is provided, with at least one light channel being provided in the light-guiding body. The light channel has an entry opening and at least one exit opening, with the wall surface(s) enclosing the light channel being designed to be completely reflective.

According to the invention, the light guide body is designed without lenses.

The method advantageously enables the production of a device for detecting emitted light according to one of the previously explained embodiments. In particular, the method can thus include all method steps that are necessary for the production of a device according to one of the previously explained embodiments.

Also proposed is a method for detecting emitted light, in particular a quantity of intensity, of a security document, wherein a device according to one of the embodiments explained above is arranged relative to a surface of the security document in such a way that light emitted from at least a partial area of the surface passes through the Entrance opening enters the light channel.

This advantageously results in a detection of emitted light that does not require a cost-intensive device that requires installation space.

• Fig. 1 einen schematischen Querschnitt durch eine nicht erfindungsgemäße Vorrichtung,
• Fig. 2 einen schematischen Längsschnitt durch einen Lichtkanal,
• Fig. 3 einen schematischen Längsschnitt durch einen Lichtkanal in einem weiteren nicht erfindungsgemäßen Beispiel,
• Fig. 4 einen schematischen Querschnitt durch eine erfindungsgemäße Vorrichtung in einer weiteren Ausführungsform,
• Fig. 5 eine perspektivische Ansicht einer erfindungsgemäßen Vorrichtung eines weiteren nicht erfindungsgemäßen Beispiels und
• Fig. 6 einen schematischen Querschnitt durch eine erfindungsgemäße Vorrichtung in einer weiteren Ausführungsform.

The invention is explained in more detail using several exemplary embodiments. The figures show:

• 1 a schematic cross section through a device not according to the invention,
• 2 a schematic longitudinal section through a light channel,
• 3 a schematic longitudinal section through a light channel in a further example not according to the invention,
• 4 a schematic cross section through a device according to the invention in a further embodiment,
• figure 5 a perspective view of a device according to the invention of a further example not according to the invention and
• 6 a schematic cross section through a device according to the invention in a further embodiment.

In 1 a schematic cross section through a device 1 for detecting emitted light 2, which is represented by arrows as an example, of a security document 3 is represented. The device 1 comprises an optical fiber 4 and an optical sensor 5, which can be designed, for example, as a photodetector, in particular as a CCD sensor or CMOS sensor. The light guide body 4 has a light channel 6 . The light channel 6 has an entry opening 7 and an exit opening 8 on. It is shown here that the emitted light 2 enters the light channel 6 through the entry opening 7 and is reflected along the light channel 6 by wall surfaces 9 of the light channel 6 and is thus radiated to the exit opening 8 . The light 2 exiting through the exit opening 8 radiates onto an active surface 10 of the optical sensor 5 . The optical sensor 5 is here arranged at the exit opening 8 .

The wall surfaces 9 of the light channel 6 are designed to be completely reflective. Light 2 thus emerges from light channel 6 exclusively via exit opening 8 from light channel 6 .

It is also shown that the light guide body 4, in particular the light channel 6, is designed without lenses. In particular, no lens for beam bundling, beam refraction or beam steering is provided in or on the entrance opening 7, in or on the light channel 6 or in or on the exit opening 8.

In 1 it is shown that the light channel 6 is designed in the shape of a truncated cone. Here, a diameter of the light channel 6 decreases from the entry opening 7 to the exit opening 8.

It is also shown by way of example that the light 2 propagates from the entry opening 7 to the exit opening 8 without back reflection. A central axis z of the light channel 6 is represented by a dashed line, which is oriented orthogonally to a surface of the entry opening 7 and is oriented from the entry opening 7 to the exit opening 8 . In 1 it is shown that light rays 2 before and after a reflection on the wall surface 10 of the light channel 6 have a portion in each section of the light channel 6 which is oriented parallel to the central axis z and towards the exit opening 8 . In particular, the direction before or after a reflection of the light beams 2 does not contain any part that is oriented parallel to the optical axis z towards the entrance opening 7 .

In 2 a light channel 6 is shown in a longitudinal section in a first example not according to the invention. in the in 2 illustrated embodiment, the light channel 6 can be formed, for example, in the shape of a truncated pyramid. It is shown that a first wall surface 9a or a first wall surface section is oriented parallel to the central axis z of the light channel 6 .

in the in 2 In the example shown, the central axis z of the light channel 6 again corresponds to a center line of the entrance opening 7, which is oriented perpendicularly to the surface of the entrance opening 7 and intersects it at a geometric center point. In this case, the central axis z runs along the light channel 6, not in the center of the light channel 6.

The first wall surface 9a is thus not inclined. Also shown is a second wall surface 9b or a second wall surface section which is inclined relative to the central axis z, in particular at an angle of inclination β.

In 2 E denotes a diameter or a width of the entry opening 7. Furthermore, D denotes a diameter or a width of the exit opening 8. L _OB denotes a desired or necessary distance of the entry opening 7 from the surface of the security document 3 to be detected along the central axis z. Also shown is a length L _M of the light channel 6 along the central axis z. By way of example, the reference symbol α designates a minimum angle of incidence of the light 2 onto the first wall surface 9a. In this case, the angle γ designates a detection angle.

Also shown is an exemplary course of a light beam 2, which impinges on the first wall surface 9a at the entry opening 7 with the minimum angle of incidence α. This light beam 2 is reflected on the first wall surface 9a with the angle of incidence, ie the angle α, and is radiated towards the second wall surface 9b. The path of the light beam 2 is shown here for a number of reflections, it being evident that the angle of incidence and reflection decreases along the light channel 6 in the event of a reflection on the wall surfaces 9a, 9b.

und $$\tan \alpha \mathrm{=}\left(2\times {\mathrm{L}}_{\mathrm{OB}}\right)/\mathrm{E}$$

und $$\mathrm{\alpha }\ge \left(\mathrm{N}+1\right)\times \beta$$

for the inside 2 In the example shown, the following relationships apply: $$\tan \beta \mathrm{=}\left(\mathrm{E}-\mathrm{D}\right)/{\mathrm{L}}_{\mathrm{M}}$$

and $$\tan a\mathrm{=}\left(2\times {\mathrm{L}}_{\mathrm{IF}}\right)/\mathrm{E}$$

and $$\mathrm{a}\ge \left(\mathrm{N}+1\right)\times \beta$$

Here N denotes the number of reflections.

The length L _M and/or the size of the entry opening E and/or the angle of inclination β can be adjustable parameters during the manufacture of the fiber-optic element 4 . The relationship between the angle of inclination β, the length of the light channel L _M and the size of the entry and exit openings E, D is given by formula 1. These parameters can be determined, for example, in such a way that the light beams entering through the entry opening 7 are radiated through the light channel 6 in the direction of the entry opening 7 without being reflected back. For example, depending on this relationship, a maximum number of reflections can be determined which the light rays entering through entrance opening 7 can undergo without being reflected back in the direction of entrance opening 7 . They thus determine the minimum angle of incidence for a beam that can reach the exit opening 8 after multiple reflections.

In 2 it is shown that for a ray with an angle of incidence α , after a third reflection from the second wall surface 9b, there is a back reflection in the direction of the entry opening 7.

und $$\tan \gamma \mathrm{=}\left(\mathrm{E}-\mathrm{D}\right)/\left(2\times {\mathrm{L}}_{\mathrm{OB}}\right)$$

undIn 3 an exemplary longitudinal section through a light channel 6 of a further example not according to the invention is shown. In contrast to the in 2 In the illustrated embodiment, the first wall surface 9a or the first wall surface section is also inclined at the angle of inclination β relative to the central axis z. In this embodiment, the following relationships apply: $$\tan \beta \mathrm{=}\left(\mathrm{E}-\mathrm{D}\right)/2\times {\mathrm{L}}_{\mathrm{M}}$$

and $$\tan g\mathrm{=}\left(\mathrm{E}-\mathrm{D}\right)/\left(2\times {\mathrm{L}}_{\mathrm{IF}}\right)$$

and

In 4 a schematic cross section through a device 1 according to the invention is shown in a further embodiment. In contrast to the in 1 In the example shown, the light channel 6 has a branching of the light channel 6 into a first sub-channel 11a and a second sub-channel 11b. The first partial channel 11a has the first outlet opening 8 , the second partial channel 11b having a further outlet opening 12 . The device 1 further comprises a further optical sensor 13 with an active surface 14 of the further optical sensor 13. Also shown is a beam splitter 15, the light from a main channel section 16 of the light channel 6 in a predetermined ratio in the first sub-channel 11a (first sub-channel section) and radiates into the second sub-channel 11b (second sub-channel section).

The additional optical sensor 13 is arranged at the additional exit opening 12 , light 2 emerging from the additional exit opening 12 falling on the active surface 14 of the additional optical sensor 13 .

The optical sensors 5, 13 can be used to detect various properties of the light 2. The optical sensors 5, 13 can also be combined with mutually different optical elements, for example different optical filters, e.g. with mutually different color filters. In this case in particular, the optical sensors 5, 13 can be used to detect different properties of the light 2.

For example, the optical sensor 5 can be designed as a photodetector or as a photodetector combined with a spectral filter. The further optical sensor 13 can be embodied as a color sensor or spectral sensor, for example. The further optical sensor 13 can also be designed as a CCD sensor.

For example, a time profile of the light intensity can be detected by the first optical sensor 5 , a spectral composition, for example a color, of the light 2 being determined by the further optical sensor 13 .

Next is in 4 a central axis z ₁ of the first partial channel 11a is shown, which corresponds to the central axis z of the main channel section 16 of the light channel 6 , the central axis of the main channel section 16 corresponding to a center line of the entry opening 7 . Also shown is an inlet opening 18 of the first partial channel 11a, with the central axis z ₁ corresponding to a center line of the inlet opening 18 of the first partial channel 11a. Wall surfaces of the first sub-channel 11a are inclined relative to the central axis z ₁ of the first sub-channel 11a.

A central axis z ₂ of the second partial channel 11b is also shown. The further central axis z ₂ is oriented orthogonally to an inlet opening 17 of the second partial channel 11b and intersects the surface of the further inlet opening 17 at its geometric center. Wall surfaces of the second sub-channel 11b are inclined relative to the central axis z ₂ of the further sub-channel 11b. Here, the central axis z ₂ of the second partial channel 11b is inclined relative to the central axis z ₁ of the first partial channel section 11a.

In figure 5 a perspective view of a device 1 of a further example not according to the invention is shown. It is shown here that the light channel 6 is in the form of a truncated pyramid. It is also shown that both the first optical sensor 5 and the further optical sensor 13 are arranged next to one another in the exit opening 8 of the light channel 6 . One dimension of the outlet opening 8 is here adapted to a dimension and geometry of the overall arrangement made up of the first optical sensor 5 and the further optical sensor 13 . In particular, the outlet opening 8 encloses the rectangular envelope of the active surfaces 10, 14 (see FIG 4 ) of the two sensors 5, 13.

As previously in relation to 4 already explained, the optical sensors 5, 13 can be designed to detect mutually different properties of the light 2 or be combined with mutually different optical elements, in particular filter elements.

At the in figure 5 Arrangement of the first and the further optical sensor 5, 13 shown are active surfaces 10, 14 (see 4 ) of the optical sensors 5, 13 arranged side by side in one plane. As a result, the light front of the light 2 impinging on the active surfaces can be divided into channels. However, there is no division here the light amplitude. However, when detecting, determining and evaluating properties of the light detected in this way, a homogeneity of the light distribution in the plane of the active surfaces can be taken into account.

In general, a geometry of the light channel 6 and thus a design and/or arrangement of the wall surface(s) 9, 9a, 9b can be freely selected. Ideally, however, the shape and arrangement is adapted to a geometry and/or dimension of the active surface 10, 14 of an optical sensor 5, 13. The design and/or arrangement can also be selected in such a way that there is no back reflection in the light channel 6 .

In 6 a schematic cross section through a device 1 is shown in a further embodiment. It is shown here that the light channel 6 branches at a junction into a first sub-channel 11a and a second sub-channel 11b. The branching is achieved here by the formation of the light channel 6, in particular by a corresponding wall surface course. The branching is designed in such a way that light 2 from a main channel section 16 of the light channel 6 radiates into the first sub-channel 11a and the second sub-channel 11b in a predetermined ratio. An inlet opening 17 of the second partial channel 11b and an inlet opening 18 of the first partial channel 11a are shown. Central axes z ₁ , z ₂ of the first sub-channel 11a and of the second sub-channel 11b are also shown. It is shown here that the central axes z ₁ , z ₂ of the partial channels 11a, 11b are each inclined relative to the central axis z of the main section 16 .

It is also shown that a wall surface inclination of a wall surface of the first partial channel 11a and a wall surface of the second partial channel 11b changes along the first or second partial channel 11a, 11b. The wall surfaces of the first and of the second partial channel 11a, 11b are each curved. How regarding 4 already explained, the first optical sensor 5 is arranged at the first exit opening 8 , the second optical sensor 13 being arranged at the further exit opening 12 .

The proposed device 1 offers several advantages. On the one hand, light losses are reduced since no lenses are used in the device 1. If the exit opening 8, 12 is adapted to the respective optical sensor 5, 13, light losses can also be minimized as a result, in particular if the active surface 10, 14 of the respective sensor 5, 13 completely fills or covers the corresponding outlet opening 8, 12.

Furthermore, the proposed device 1 is less sensitive to a lateral position deviation of the radiation source to be measured (e.g. the emitting, reflecting and/or scattering surface of the security document 3) compared to the lens-based embodiment, the lateral position deviation being a deviation perpendicular to the center line of the entry opening 7 designated. The proposed device 1 is also less sensitive to an inclination of the surface of the security document 3 relative to this center line. This means that the amount of light directed towards the at least one exit opening 8, 12 is not dependent on the lateral position deviation and/or inclination, or only to a small extent. Furthermore, the entry opening 7, in particular its geometry and/or dimension, can be adapted to a geometry and/or dimension of a security feature of the security document 3. Further, the cost and weight of the device 1 can be reduced. Due to the high light efficiency, more economical optical sensors 5, 13 can also be used, which can also be flexibly selected in terms of their shape. It is also easy to adjust and maintain.

Reference List

1

contraption

2

beam of light

3

security document

4

fiber optic body

5

first optical sensor

6

light channel

7

entry opening

8th

exit port

9

wall surface

9a

first wall surface

9b

more wall space

10

active area

11a

first sub-channel

11b

second sub-channel

12

further exit opening

13

another optical sensor

14

active area

15

beam splitter

16

main canal section

17

Entry opening of the second partial channel

18

Entry opening of the first partial channel

e.g

central axis of the light channel/main section

z1

central axis of the first sub-channel

z2

central axis of the further partial channel

E

Diameter/width of the entrance opening

D

Diameter/width of the outlet opening

β

tilt angle

a

minimum angle of incidence

g

detection angle

PRAISE

Distance between the entrance opening and the surface to be measured

LM

Length of the light channel

Claims (13)

1. Apparatus for capturing light (3) emitted by a security document (3), wherein the apparatus (1) comprises at least one light-guide body (4), wherein the light-guide body (4) has or forms at least one light channel (6), wherein the light channel (6) has an entrance opening (7) and at least one first exit opening (8), wherein the wall surface(s) (9, 9a, 9b) enclosing the light channel (6) is/are formed to be completely reflective such that no light can emerge from the light channel (6) through the wall surface (s) (9, 9a, 9b), wherein the light-guide body (4) is designed to be free of lenses, wherein a shape of the entrance opening differs from a shape of the exit opening and an area of the entrance opening differs from the area of the exit opening,
   characterized in that
   the light channel (6) has at least one branching point into a first partial channel (11a) with the first exit opening (8) and into at least one further partial channel (11b) with a further exit opening (12).
2. Apparatus according to Claim 1, characterized in that the light channel (6) is formed as a free-form body such that a direction of the light input through the entrance opening in the light channel is changed only such that the beam direction in every section of the light channel comprises a component that is parallel to a central line or central axis of the light channel and is oriented in the direction towards the exit opening.
3. Apparatus according to Claim 1 or 2, characterized in that the apparatus (1) comprises at least one optical sensor (5), wherein the optical sensor (5) is arranged in or at the first exit opening (8).
4. Apparatus according to one of the preceding claims, characterized in that the apparatus (1) comprises a beam splitter (15) splitting light (2) in a predetermined ratio into the first partial channel (11a) and the at least one further partial channel (11b).
5. Apparatus according to one of the preceding claims, characterized in that the branching point is formed such that the light (2) is split with a predetermined ratio into the first partial channel (11a) and the at least one further partial channel (11b).
6. Apparatus according to one of the preceding claims, characterized in that the apparatus comprises at least one further optical sensor (13), wherein the at least one further optical sensor (13) is arranged in or at the first exit opening (8) or in or at the at least one further exit opening (12).
7. Apparatus according to Claim 6, characterized in that the first optical sensor (5) is a spectral sensor and the at least one further sensor (13) is a light-quantity sensor.
8. Apparatus according to one of Claims 1 to 7, characterized in that a cross section of the light channel (6) decreases from the entrance opening (7) to the at least one exit opening (8), or the cross section of the light channel (6) increases from the entrance opening (7) to the at least one exit opening (8).
9. Apparatus according to one of Claims 1 to 8, characterized in that at least one partial section of the light channel (6) and/or at least one partial section of the at least one partial channel (11a, 11b) is formed in the shape of a truncated cone or a truncated pyramid.
10. Apparatus according to one of Claims 1 to 9, characterized in that a wall surface inclination changes along the light channel (6) and/or along at least one partial channel (11a, 11b), wherein the wall surface inclination along the light channel and/or along the at least one partial channel is greater than or equal to a predetermined minimum inclination and/or less than or equal to a maximum inclination.
11. Apparatus according to one of Claims 1 to 10, characterized in that the light channel (6) is formed by a light-transmissive material or there is air in the light channel (6).
12. Method for producing an apparatus (1) for capturing light (2) emitted by a security document (3), wherein at least one light-guide body (4) is provided, wherein at least one light channel (6) is provided in the light-guide body (4), wherein the light channel (6) has an entrance opening (7) and at least one first exit opening (8), wherein the wall surface(s) (9, 9a, 9b) enclosing the light channel (6) is/are formed to be completely reflective such that no light can emerge from the light channel (6) through the wall surface (s) (9, 9a, 9b), wherein the light-guide body (4) is designed to be free of lenses, wherein a shape of the entrance opening differs from a shape of the exit opening and/or an area of the entrance opening differs from the area of the exit opening,
    characterized in that
    the light channel (6) has at least one branching point into a first partial channel (11a) with the first exit opening (8) and into at least one further partial channel (11b) with a further exit opening (12).
13. Method for capturing light (2) emitted by a security document (3), wherein an apparatus (1) according to one of Claims 1 to 11 is arranged relative to a surface of the security document (3) such that light (2) emitted by at least one partial region of the surface enters the light channel (6) through the entrance opening (7).

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