CN111684243A - Spectrometer, method for making a spectrometer and method for operating a spectrometer - Google Patents

Abstract

The invention relates to a spectrometer (100) having: an optical filter (102) for filtering out a wavelength range to be analyzed from the electromagnetic radiation; and a detector (104) having at least one, in particular a plurality of, angle-sensitive pixels (106) for detecting an intensity of transmitted radiation transmitted from the optical filter (102) depending on an angle of incidence of the transmitted radiation.

Description

Spectrometer, method for making a spectrometer and method for operating a spectrometer

technical field

The starting point of the invention is a device or a method according to the preambles of the independent claims. The subject of the invention is also a computer program.

Background technique

Spectrometers are used, for example, to examine the material composition of substances or objects. In this way, for example, electromagnetic radiation, such as visible light or infrared light, which interacts with the object can be broken down into its wavelength components, which are absorbed differently depending on the material. A spectrum is obtained whose shape is characteristic for a particular substance or mixture of substances. The so-called Fabry-Perot spectrometer, which at its heart contains the Fabry-Perot interferometer, also known as the etalon ( Etalon).

Here, the incident light beam enters a Fabry-Perot interferometer, which consists of two opposing plane-parallel mirrors, on which the light is reflected multiple times. At each reflection, a portion of the light is transmitted. After the Fabry-Perot interferometer, a beam is formed with coherent partial beams that can interfere with each other. If d is the spacing between the mirrors, the condition for constructive interference is 2d*cosα = mλ, where α is the angle between the incident beam and the optical axis and m is a natural number (spectral order). If only light of the first order and incident parallel to the optical axis is considered, only light of wavelength λ (and higher orders) is transmitted. By changing the spacing d, the transmission wavelength of the Fabry-Perot interferometer can be changed. Thus, a tunable filter is obtained, with which the spectra can be recorded sequentially using corresponding detectors. If the light is not exactly parallel to the optical axis, other (blue-shifted) wavelengths may also be transmitted depending on the angle of incidence α. Without additional measures, light of different wavelengths strikes the detector superimposed. To separate these wavelengths, a lens or generally focusing optics can be placed behind the Fabry-Perot interferometer. As a result, the different transmitted wavelengths that are transmitted at the distance d are mapped onto concentric rings in the detection plane, the radius of which depends on the angle of incidence α and the focal length of the lens. By using a lens, the spectral resolution can be increased and, in the static case, that is to say with a fixed distance d, a spectrum for a limited spectral range can be obtained with a corresponding distribution of angles of incidence.

A miniaturized Talbot spectrometer is described in US 2002/0126279 A1. With the aid of the periodic structure, Talbot images are generated with different spacings of the periodic structure, which are detected by the detectors. The pitch-dependent intensity distribution is Fourier transformed in order to determine the light spectrum.

A spectroscopic device is described in DE 10121499 A1. The Talbot effect is exploited here in order to select a mode or modes of arrival at the detector.

SUMMARY OF THE INVENTION

Against this background, with the solution proposed here, a spectrometer, a method for manufacturing a spectrometer, a method for operating a spectrometer, a device using the method according to the independent claims are proposed and a corresponding computer program. By means of the measures mentioned in the dependent claims, advantageous modifications and improvements of the devices specified in the independent claims are possible.

Fabry-Perot spectrometers can be miniaturized very well due to their flat structure type. Here, structure heights of less than one millimeter can easily be achieved. The problem with miniaturization, however, is the optional lens described above, since the lens requires a certain focal length or numerical aperture in order to have sufficient focusing quality. Thus, in the case of an aperture diameter of 1 mm, a focal length of 1 mm is practical. If one wants to increase the area of the optical filter of the spectrometer in order to collect more light, the aperture and thereby the focal length of the lens should also be correspondingly increased. This could increase the thickness of the entire spectrometer to the order of a few millimeters, whereby the module has become unattractive for some applications, such as integration into smartphones. The solution described here solves this problem by omitting the focusing element and transferring the angular selectivity into a correspondingly configured detector. The advantage of the approach described here is that by using such an angle-sensitive detector and the associated omission of lenses or other focusing elements between the detector and the optical filter, the spectrometer can be built much smaller .

A spectrometer is proposed, which has the following characteristics:

Optical filters for filtering out the wavelength range to be analyzed from electromagnetic radiation; and

A detector having at least one angle-sensitive pixel, in particular a plurality of angle-sensitive pixels, for detecting the intensity of the transmitted radiation transmitted through the optical filter as a function of its angle of incidence.

A spectrometer can be understood as an instrument used to measure or present the electromagnetic spectrum. An optical filter can be understood to mean, for example, an optical resonator, in particular a static or tunable Fabry-Perot interferometer, a Bragg filter, a bandpass filter or at least one of the optical filters mentioned. A combination of two optical filters. A detector can be understood to be, for example, a photodiode, a phototransistor, a CMOS or CCD sensor or an arrangement consisting of a plurality of such photosensitive devices. An angle-sensitive pixel, also called an angle-sensitive pixel (ASP), can be understood as a detector element of a detector having at least one diffraction grating. The angle-sensitive pixels can be configured to detect the intensity of the light beams as a function of their respective angle of incidence with respect to the pixel surface, taking advantage of the so-called Talbot effect. Transmitted radiation can be understood as the radiation portion of electromagnetic radiation that is filtered out by an optical filter. The detector can be implemented, for example, as an array of a plurality of such angle-sensitive pixels. The optical filter and the detector can, for example, overlap each other flat. In particular, the optical filter and the detector can be connected to one another in a compact layer complex.

According to one embodiment, the pixels can be configured to detect the intensity as a sine function of the angle of incidence. As a result, the intensity can be determined computationally inexpensively as a function of the angle of incidence.

In addition, the pixel may have: a diffraction grating for generating an intensity pattern with a phase that depends on the angle of incidence when using transmitted radiation; and a sensing element for generating, using the intensity pattern, representing the intensity pattern strength signal. A diffraction grating, also known as diffraction grating, can be understood as a cover layer or intermediate layer of a pixel that is structured with a plurality of through-holes arranged at a predetermined distance from one another. A sensing element can be understood as a photosensitive device downstream of the diffraction grating, such as a photodiode or a CMOS sensor. The sensor element can be arranged opposite the diffraction grating. An intensity pattern can be understood as an interference pattern, especially a near-field interference pattern, due to the diffraction of a light beam on a diffraction grating, also known as the Talbot effect. The intensity pattern can be sinusoidal, for example. With this embodiment, the pixel can be implemented particularly compactly.

Advantageously, the pixel has at least one intermediate grating arranged between the sensor element and the diffraction grating for generating an additional intensity pattern using this intensity pattern. In this case, the sensor element can be designed to generate an intensity signal using this additional intensity pattern. The intermediate grating can be understood as another diffraction grating of the pixel. The intermediate grating, also called analyzer grating, can be arranged at a predetermined distance from the diffraction grating. For example, the intermediate gratings may be arranged at a spacing from the diffraction grating corresponding to the so-called Talbot depth. The intermediate grating may have the same or similar structure as the diffraction grating or may also have a different structure than the diffraction grating. With this embodiment, the measurement accuracy of the spectrometer can be improved.

The intermediate grating can be configured as an analysis grating for determining the phase shift of the intensity pattern. Thereby, the phase shift between the intensity pattern at normal incidence of the transmitted radiation and the intensity pattern at oblique incidence of the transmitted radiation can be determined.

According to a further embodiment, the detector may have a detector matrix with the pixel and at least one other angle-sensitive pixel for detecting the intensity as a function of the angle of incidence. In this case, the further pixel can have: a different diffraction grating than the diffraction grating for generating another intensity pattern with a phase dependent on the angle of incidence when using transmitted radiation; and a further sensing element, for generating another intensity signal representative of the other intensity pattern using the other intensity pattern. A detector matrix can be understood as an array of at least two angle-sensitive pixels. Thereby, a unique correlation between angle of incidence and intensity can be guaranteed.

It is also advantageous if the optical filter is implemented as an optical resonator. The optical resonator may be, for example, a tunable Fabry-Perot interferometer. As a result, the optical filter can be provided in a compact design and at low cost.

The optical filter and the detector can advantageously be combined with one another to form a layer composite. As a result, the spectrometer can be produced particularly compact.

The proposed scheme also provides a method for manufacturing a spectrometer, wherein the method comprises the steps of:

An optical filter for filtering out the wavelength range to be analyzed from electromagnetic radiation is combined with a detector having at least one angle-sensitive pixel, in particular a plurality of angle-sensitive pixels, in order to use this pixel and/or these pixels according to the The intensity of the transmitted radiation is detected by the incident angle of the transmitted radiation transmitted by the optical filter.

The solution proposed here also provides a method for operating a spectrometer according to one of the above embodiments, wherein the method comprises the steps of:

operating optical filters to filter out the wavelength range to be analyzed from electromagnetic radiation; and

In response to the manipulation, an intensity signal representing an intensity pattern with a phase dependent on the angle of incidence generated using the pixel and/or the diffraction grating of the pixels is analyzed in order to determine the spectrum from the intensity pattern.

The method can be implemented, for example, in software or hardware or in a mixture of software and hardware, for example in a control device.

The solution presented here also provides an apparatus which is designed to carry out, control or implement the steps of the variants of the method proposed here in a corresponding device. The tasks on which the invention is based can also be solved quickly and efficiently by means of these implementation variants of the invention in the form of devices.

For this purpose, the device can have: at least one computing unit for processing signals or data; at least one memory unit for storing signals or data; at least one interface with sensors or actuators for reading in sensor signals from the sensors Or for outputting data signals or control signals to the actuator; and/or at least one communication interface for reading in or outputting data embedded in the communication protocol. The computing unit may be, for example, a signal processor, a microcontroller or the like, wherein the storage unit may be a flash memory, an EPROM or a magnetic storage unit. The communication interface can be designed to read in or output data wirelessly and/or wiredly, wherein the communication interface that can read in or output wired data can, for example, read in the data electrically or optically from a corresponding data transmission line or These data can be output into corresponding data transmission lines, for example, electrically or optically.

In the present context, a device can be understood as an electrical device which processes sensor signals and outputs control and/or data signals in accordance therewith. The device can have an interface, which can be configured in hardware and/or software. In a hardware-based configuration, the interface can, for example, be part of a so-called system ASIC, which contains the various functions of the device. However, it is also possible that these interfaces are dedicated integrated circuits or at least partly consist of discrete components. In a software-based configuration, these interfaces can be software modules, which are present alongside other software modules, for example on a microcontroller.

Also advantageous is a computer program product or computer program with a program code which can be stored on a machine-readable carrier or a storage medium such as a semiconductor memory, hard disk memory or optical memory and in particular when the program product is Or the program, when implemented on a computer or device, is used to carry out, implement and/or manipulate the steps of the method according to one of the above-mentioned embodiments.

Description of drawings

Embodiments of the invention are illustrated in the drawings and are further explained in the description that follows. in:

Figure 1 shows a schematic diagram of a spectrometer according to an embodiment;

Figure 2 shows a schematic diagram of a spectrometer according to an embodiment;

FIG. 3 shows a schematic diagram of the angle-sensitive pixel of FIGS. 1 and 2;

Figure 4 shows a graph for presenting the intensity pattern produced by an angle-sensitive pixel according to an embodiment at normal incidence of light;

5 shows a graph for presenting intensity patterns produced by angle-sensitive pixels according to embodiments at oblique incidence of light;

6 shows a schematic diagram of an angle-sensitive pixel according to an embodiment when light is at normal incidence;

FIG. 7 shows a schematic diagram of the angle-sensitive pixel of FIG. 6 when light is obliquely incident;

8 shows a graph for presenting intensity patterns produced by angle-sensitive pixels according to embodiments at different angles of incidence and at different grating parameters;

Figure 9 shows a schematic diagram of an apparatus for operating a spectrometer according to an embodiment;

10 shows a flowchart of a method for operating a spectrometer in accordance with an embodiment; and

FIG. 11 shows a flowchart of a method for manufacturing a spectrometer according to an embodiment.

In the subsequent description of advantageous embodiments of the invention, the same or similar reference numerals are used for elements that are shown in different figures and serve a similar function, wherein a repeated description of these elements is omitted.

Detailed ways

FIG. 1 shows a schematic diagram of a spectrometer 100 according to an embodiment. The spectrometer 100, such as a microscopic spectrometer, includes an optical filter 102 for filtering out the wavelength range to be analyzed from the electromagnetic radiation. By way of example, the optical filter 102 according to the embodiment shown in FIG. 1 is implemented as a tunable Fabry-Perot interferometer. The optical filter 102 is connected to an angle-sensitive detector 104 having at least one angle-sensitive pixel 106 . According to this embodiment, the optical filter 102 and the detector 104 are combined with each other into a layer composite, wherein the optical filter 102 is applied directly to the surface of the detector 104 and the angle-sensitive pixel 106 is opposite the optical filter 102 . The pixels 106 are designed to detect the intensity of the transmitted radiation transmitted from the optical filter 102 as a function of the angle of incidence of the transmitted radiation on the pixels 106 . By using the angle sensitive detector 104, additional lenses downstream of the optical filter 102 can be omitted. As a result, the spectrometer 100 can be produced particularly compact.

As can be seen from FIG. 1 , the size of the optical filter 102 and thereby the collection area is determined only by the detector 104 . The detector 104 has, for example, an extension of a few millimeters.

Optionally, a further filter 108 is arranged on the optical filter 102 for suppressing undesired wavelengths, eg higher transmission levels. The also optional optical diffuser 110 ensures that the incident light has a certain angular distribution. The optical diffuser 110 is upstream of the further filter 108 and is eg coated directly onto the further filter.

The transmission characteristic of the Fabry-Perot interferometer, that is to say the transmission wavelength as a function of the angle of incidence at a specific mirror spacing d, is assumed to be known and can be simulated or measured. Since the detector 104 performs a correlation of the transmitted light intensity to the angle of incidence, the entire system can perform a wavelength or angle of incidence to intensity correlation, ie for all angles of incidence with a set mirror spacing for light The spectrum is calculated for the part that is both transmitted. For this, neither focusing elements nor angle limiting elements are required. The optional diffuser 110 ensures that there is a sufficiently large angular distribution of the light beam on the Fabry-Perot interferometer, eg in the case of specular reflection or collimated incidence in the Fabry-Perot There is a sufficiently large angular distribution of the beam on the interferometer.

FIG. 2 shows a schematic diagram of a spectrometer 100 according to an embodiment. Similar to the spectrometer shown in FIG. 1 , the spectrometer 100 shown in FIG. 2 is constructed in several layers, with the difference that the optical filter 102 according to this embodiment is not embodied as a tunable Fabry-Perth Bragg interferometer, but implemented as a matrix of different optical filters, such as static Fabry-Perot interferometers or Bragg filters, which serve as angle-dependent bands pass filter and cover multiple smaller wavelength ranges. Other filters, such as linearly variable filter elements, are also possible. The transmission spectra of these individual filters are either disjoint or partially overlap each other. As in FIG. 1 , the spectrometer 100 according to FIG. 2 has an optional further filter 108 and an optional optical diffuser 110 .

FIG. 3 shows a schematic diagram of an angle-sensitive pixel 106 according to an embodiment. The pixel described above with reference to FIG. 1 is shown by way of example in an enlarged view. According to this embodiment, the pixel 106 has a layered structure with: a diffraction grating 300 as a cover layer; a sensor element 302 , here by way of example a photodiode; Another diffraction grating in between is used as the intermediate grating 304 . The two diffraction gratings 300 , 304 are arranged relative to each other at a predetermined vertical grating spacing z and each have a plurality of through holes 306 for transmitting or diffracting the transmitted radiation. These through holes 306 are arranged with a grating pitch d relative to each other. Depending on the embodiment, the grating spacing d is chosen to be the same or different for the two diffraction gratings 300 , 304 . The phase and orientation of these diffraction gratings may also vary. The through holes 306 of the two diffraction gratings 300 , 304 are, for example, horizontally offset from each other. Alternatively, each of the through holes 306 of the diffraction grating 300 is opposed to each of the through holes 306 of the intermediate grating 304 .

Diffraction grating 300 is designed to diffract incident transmitted radiation differently depending on the angle of incidence, and thus to generate, for example, a sinusoidal intensity pattern with a phase that is dependent on the respective angle of incidence. The sensor element 302 is designed to convert the intensity pattern into a corresponding electrical intensity signal 306 , which is further processed, eg for recording a spectrum.

Here, the intermediate grating 304 serves as an analysis grating in order to detect the phase shift of the intensity pattern produced at oblique incidence of light relative to the intensity pattern produced at normal incidence of light.

FIG. 3 shows a schematic design of the angle-sensitive pixel 106 . Here, the diffraction grating 300, also known as diffraction grating, is used to generate a near field interference pattern, also known as the Talbot effect. At a certain spacing, the so-called Talbot depth, this periodic pattern has the same spatial frequency as the generator grating and changes the phase at oblique incidence of light in a corresponding manner. The intermediate grating 304 is used as an analysis grating, also called analyzergrating, in order to detect the angle of incidence of the light.

The spectrometer 100 is implemented, for example, as a Fabry-Perot etalon or a combination of an optical filter and an angle-sensitive detector 104 serving a similar function. Such detectors may also be referred to as lensless imagers or planar fourier capture arrays. The detector possesses one or more angle-sensitive pixels 106 whose sensitivity describes a sine function of the angle of incidence. In this case a system is involved which allows to deduce the propagation direction of the incident beam without the use of lenses or similar focusing elements.

Diffraction grating 300 produces an angle-dependent near-field diffraction pattern. Under the Talbot effect, the intensity distribution has the same frequency as the diffraction grating 300, is sinusoidal and is shifted as the angle of incidence changes. To measure the resulting phase shift, an analysis grid is used such that an angle-dependent fluctuation of the total intensity is caused on the sensing element 302 as shown in FIGS. 6 , 7 and 8 .

If light strikes such a pixel 106 at different angles of incidence, the intensity-angle-of-incidence correlation may not be unique. To overcome this, the pixels are grouped with differently shaped gratings into a detector matrix. The final correlation of incident direction and intensity is achieved by numerical post-processing.

The detector 104 can be produced, for example, in a conventional CMOS process and is therefore well suited for series production. A particular advantage of this combination of angle-sensitive detectors and Fabry-Perot interferometers is the omission of optics for selecting the angle of incidence or wavelength, which enables a substantial reduction in the height of the structure. The entire system can also be fabricated in a semiconductor process, which brings cost and robustness advantages, since additional assembly optics are eliminated.

FIG. 4 shows a graph 400 for presenting an intensity pattern produced by an angle-sensitive pixel 106 according to an embodiment, such as by the pixel described above with respect to FIGS. 1 to 3 , at normal incidence of light. Here, a plane wave 402 incident at an angle of incidence of 0 degrees produces a sinusoidal intensity pattern with a phase that depends on the angle of incidence.

FIG. 5 shows a graph 500 for presenting the intensity pattern produced by the angle-sensitive pixel 106 according to an embodiment at oblique incidence of light. A wave 402 incident here at an angle of incidence other than 0 degrees produces an intensity pattern that is phase shifted compared to the intensity pattern at normal incidence of the light.

FIG. 6 shows a schematic diagram of the angle-sensitive pixel 106 at normal incidence of light. Unlike Figures 4 and 5, the pixel 106 according to this embodiment has an intermediate grating 304 that acts as an analysis grating.

FIG. 7 shows a schematic diagram of the angle-sensitive pixel 106 of FIG. 6 at oblique incidence of light, here exemplarily at an angle of incidence of 10 degrees.

It can be seen from Figures 6 and 7 that due to the addition of the second grating, a total intensity modulation depending on the angle of incidence occurs on the pixel 106.

FIG. 8 shows a graph for presenting the intensity patterns produced by four angle-sensitive pixels according to an embodiment in which the diffraction grating 300 and the intermediate grating 304 have different angles of incidence different phases from each other. The graph 800 exemplarily shows four intensity patterns for incident angles between -20° and 20°, the four intensity patterns and the four phase angles α = between the diffraction grating 300 and the intermediate grating 304 0, α = π/2, α = π, α = 3π/2 are associated with one phase angle each.

FIG. 9 shows a schematic diagram of an apparatus 900 for operating a spectrometer according to an embodiment, such as the spectrometer described above with reference to FIGS. 1 to 8 . The device 900 comprises a control unit 910 for providing a control signal 912 for the control of the optical filter, that is to say for setting the wavelength range to be analyzed by means of the spectrometer. The analysis unit 920 analyzes the intensity signal 306 using the manipulation signal 912 in order to record the spectrum according to the intensity pattern represented by the intensity signal. Here, the analysis unit 920 generates an analysis result 922 representing the spectrum.

FIG. 10 shows a flowchart of a method 1000 for operating a spectrometer according to an embodiment, such as the spectrometer described above with reference to FIGS. 1 to 9 . Here, in step 1010, the optical filter is manipulated in order to set the wavelength range to be analyzed on the optical filter. In the next step 1020, the intensity signal is analyzed to record a spectrum according to the intensity pattern represented by the intensity signal.

FIG. 11 shows a flowchart of a method 1100 for manufacturing a spectrometer according to an embodiment, such as the spectrometer described above with reference to FIGS. 1 to 10 . Here, in an optional preparation step 1110, optical filters and detectors are fabricated, eg, in a semiconductor process. In the next step 1120, the optical filter and detector are combined with each other into a spectrometer. Here, for example, the optical filter is applied directly to the detector. For example, in step 1110, an optical filter may be fabricated by coating onto a detector or conversely a detector may be fabricated by coating an optical filter, such that fabrication of the layer complex accompanies this fabrication of the spectrometer. Fabrication of at least one of the two components.

If an embodiment includes an "and/or" logical relationship between a first feature and a second feature, then this is understood such that the embodiment, according to one embodiment, has not only the first but also the second feature, but not according to Another embodiment has either only the first feature or only the second feature.

Claims (13)

1. A spectrometer (100) having the following features:

an optical filter (102) for filtering out a wavelength range to be analyzed from the electromagnetic radiation; and

a detector (104) having at least one, in particular a plurality of, angle-sensitive pixels (106) for detecting an intensity of transmitted radiation (402) transmitted from the optical filter (102) depending on an angle of incidence of the transmitted radiation (402).

2. The spectrometer (100) of claim 1, wherein the pixel (106) is configured to detect intensity as a sinusoidal function of the angle of incidence.

3. The spectrometer (100) of one of the preceding claims, wherein the pixel (106) has: a diffraction grating (300) for generating an intensity pattern with a phase depending on the angle of incidence, using the transmitted radiation (402); and a sensor element (302) for generating an intensity signal (306) representing the intensity pattern if the intensity pattern is used.

4. The spectrometer (100) of claim 3, wherein the pixel (106) has at least one intermediate grating (304) arranged between the sensor element (302) and the diffraction grating (300) for generating an additional intensity pattern if the intensity pattern is used, wherein the sensor element (302) is configured for generating the intensity signal (306) if the additional intensity pattern is used.

5. The spectrometer (100) of claim 4, wherein the intermediate grating is configured as an analysis grating for determining a phase shift of the intensity pattern.

6. The spectrometer (100) of one of claims 3 to 5, wherein the detector (104) has a detector matrix with the pixel (106) and at least one further angularly sensitive pixel for detecting the intensity depending on the angle of incidence, wherein the further pixel has: a further diffraction grating, different from the diffraction grating (300), for generating a further intensity pattern with a phase depending on the angle of incidence using the transmitted radiation (402); and a further sensor element for generating a further intensity signal representing the further intensity pattern if the further intensity pattern is used.

7. The spectrometer (100) of one of the preceding claims, wherein the optical filter (102) is implemented as an optical resonator.

8. The spectrometer (100) of one of the preceding claims, wherein the optical filter (102) and the detector (104) are combined with each other into a layer complex.

9. A method (1100) for manufacturing a spectrometer (100), wherein the method (1100) comprises the steps of:

an optical filter (102) for filtering out a wavelength range to be analyzed from electromagnetic radiation is combined (1120) with a detector (104) having at least one angularly sensitive pixel (106), in particular a plurality of angularly sensitive pixels (106), in order to detect the intensity of the transmitted radiation (402) by means of the pixel (106) and/or the pixels (106) depending on the angle of incidence of the transmitted radiation (402) transmitted from the optical filter (102).

10. A method (1000) for operating a spectrometer (100) according to one of the claims 1 to 8, wherein the method (1000) comprises the steps of:

-manipulating (1010) the optical filter (102) so as to filter out a wavelength range to be analyzed from the electromagnetic radiation; and is

In response to the manipulation (1010), an intensity signal (306) representing an intensity pattern with a phase depending on the angle of incidence generated using a diffraction grating (300, 304) of one (106) and/or a plurality of (106) of the pixels is analyzed (1020) in order to determine a spectrum from the intensity pattern.

11. An apparatus (900) having a unit (910, 920) configured for carrying out and/or handling the method (1000) according to claim 10.

12. A computer program configured to implement and/or handle the method (1000) according to claim 10.

13. A machine readable storage medium having stored thereon a computer program according to claim 12.

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