DE102020106104A1 - IR spectrometric method and associated reflection element and component - Google Patents

Abstract

The invention relates to an IR spectrometric method, an associated reflection element and a component. The IR spectrometric method according to the invention comprises at least the following steps: Providing an IR light source and a means for spectral analysis as well as a reflection element (2) which has at least one first surface (6), which is flat and has a second surface (3) which is structured and parallel to the first surface, and wherein the structuring causes a diverse reflection of an incident IR light beam and wherein the reflection element (2) is made of one material , which is at least partially permeable to IR light (4, 5), arranging the reflective element (2) to remain in a viscous sample (1) to be measured at time t0, the first surface of the reflective element (2) being exposed, Irradiating the reflective element (2) on the first surface (6) with an IR light beam (4) at any point in time txab the time t0 at an angle of incidence (γ) which is smaller than the angle of total internal reflection, recording the spectrum of the IR light (5 ) with the means for spectral analysis. The reflective element (2) according to the invention has at least one first surface (6) which is flat and a second surface (3) which is structured and parallel to the first surface. The structuring causes a diverse reflection of an incident IR light beam by a large number of scattering centers. The reflective element (2) is made of a material which is at least partially transparent to IR light (4, 5). In addition, a component is specified in which a reflection element according to the invention is incorporated for carrying out the method according to the invention. The method according to the invention improves the comparability of spectra, since influences of the measurement setup and the sample location are minimized.

Description

Technical area

Infrared (IR) spectrometric methods and corresponding devices are used in particular to follow the course of chemical reactions, in particular polymerizations, and to investigate the chemical composition and structure of gases, liquids and solids.

State of the art

With the help of infrared spectrometry, the composition and concentration of chemical components and their structure in samples, i.e. in materials, can be determined. The wavelength-dependent absorption of the IR light by a sample is measured. This takes place both in transmission and under conditions of reflection. Infrared spectrometry is used in a variety of ways in process and quality control of gases, liquids and solids. While special thin samples generally have to be prepared for transmission measurements on solid components, the condition of e.g. components based on polymers during and after their hardening on surfaces can be determined using reflection, in particular attenuated total reflection (ATR) . The use of ATR in particular requires the use of a suitable optical element, a so-called reflection element, which can be, for example, a prism-shaped crystal or a fiber and enables total reflection at the transition between the reflection element and a sample, and suitable mirror optics. In essay 1 by F.M. Mirabella Jr. (Internal Reflection Spectroscopy, Applied Spectroscopic Reviews, Vol. 21: 1-2, 1985, pp. 45-178) describes the fundamentals of a method using ATR. A device for performing IR spectroscopic methods using ATR according to the prior art accordingly comprises at least one IR light source, a prism-shaped crystal that ensures the attenuated total reflection of an IR light beam incident on a sample, means for pressing the ATR crystal to the sample and an analysis unit for the IR light reflected on the sample.

IR light within the meaning of the invention comprises light in a spectral range from 10 cm ^-1 to 12800 cm ^-1 wavenumbers.

In the context of the invention, a sample means a material, also to be addressed as a material, which is to be sampled, i.e. to be characterized for certain features by means of the IR spectrometric method. As a result, the sample can also be a component made from a material that is to be sampled.

In order to obtain reproducible and comparable results for this method with the described arrangement, the contact pressure and the surface contact achieved must be precisely adjusted. The surface contact should be uniform, which requires generally flat surfaces both on the sample surface and on the ATR crystal or reflection element. Measurements are only possible if there is intimate contact between the crystal / element and the component and there is no air gap or contamination between them. The importance of this condition and the disadvantages, if they are not met, are, for example, in article 2 by FM Mirabella Jr. (Quantitative Analysis of Polymers by Attenuated Total Reflectance Fourier-Transform Infrared Spectroscopy: Vinyl Acetate and Methyl Content of Polyethylenes, Journal of Polymer Science: Polymer Physics Edition, Vol. 20, 1982, pp. 2309-2315). Also in the DE 10 2006 036 808 A1 the importance of the condition is discussed, which among other things also requires that pressing the ATR crystals easily scratches them, which means that the ATR crystals are mostly made of diamond, which, however, has a limited spectral suitability in the area of Have phonon absorptions. The solution to the latter problem disclosed there includes the use of a modified ATR crystal made of diamond, which is optimized ^{in the wave number range from 2000 cm -1} to 2500 cm ^-1. The problem of uniform contact pressure is not discussed further.

An IR spectrometric method using the ATR for monitoring and in use in the production of fiber composite components using resin is for example in the DE 10 2016 215 449 A1 disclosed. In this process, the ATR crystal, which is designed as a prism, is pressed onto the component using springs. This only inadequately fulfills the requirement of level, surface contact with sufficient contact pressure. Since the measurement in this method takes place after curing, additional surface contamination and minor surface unevenness can falsify the result. Also, the arrangement in the described method, for example at a reduced process temperature, does not allow the reproducible assessment of the course of the reaction over time, which is necessary for estimating the termination of the reaction after the specified degree of curing has been reached.

Task

The invention is based on the object of specifying an IR spectrometric method which is simplified with regard to the creation of sufficient contact between the sample and the reflection element and at the same time ensures increased precision compared to the prior art. Furthermore, it is the object of the invention to specify a reflection element belonging to the inventive method and a component.

The object is achieved by the subjects of claims 1, 3 and 4. Advantageous configurations of these solutions are the subject of the dependent claims.

In the inventive IR spectrometric method, an IR light source for emitting IR light is first provided in step a). The IR light is advantageously directed and bundled, that is to say an IR light beam is present. The IR light also advantageously has a spectral width which is sufficient to be able to interact with molecular vibrations in a sample to be examined or its material. In the borderline case covered by this, the spectral width is reduced to a characteristic wave number. The IR light source also includes any optical means required for beam guidance, focusing and filtering of the light emitted by the IR light source, such as lenses, filters, polarizers and mirrors.

Furthermore, a means for spectral analysis of the reflected radiation is provided, advantageously an IR spectrometer. The means for spectral analysis typically includes monochromators or interferometers and detectors as well as means for electronic data processing that process the recorded spectra and also serve for evaluation. The means for spectral analysis also includes any optical means required for beam guidance, focusing and filtering of the light reflected by a sample, such as lenses, filters, polarizers and mirrors.

IR light sources and means for spectral analysis as well as any required optical means are sufficiently known to the person skilled in the art and correspond to the state of the art. In addition, a reflective element according to the invention is provided. The reflective element has at least a first surface, which is smooth, and a second surface, parallel to the first, which has a structure. The structuring is designed in such a way that the IR light penetrating into the reflection element at an angle of incidence that is smaller than the total reflection angle resulting from the transition from air at the interface (first surface) to the material of the reflection element an interface between the material of the sample to be examined and the reflection element is reflected diversely. The diverse reflection here means that there are several scattering centers in the reflective, structured surface. In the simplest case, the structuring of the second surface causes the reflection to take place diffusely, which means for the structuring that it consists of a roughening of the second surface of the reflection element or a disordered structure, as it also corresponds to an embodiment. A roughening can be brought about, for example, by sandblasting or etching. A structuring of the second surface of the reflection element, which causes the condition of reflection at an interface between the sample and the reflection element, is also possible through a directed or ordered structure that also contains several scattering centers causes to achieve, as it corresponds to a further embodiment. This type of structuring can be achieved, for example, by lithographic processes or processing of the second surface with laser or electron beams, or in the manufacturing process by embossing. The structuring, in the form of roughening or ordered structure, lies with its characteristic sizes of the depth or height of the structure-forming elements and their spacing in a size range from one nanometer (1 nm) to the millimeter range (<1 cm) and in particular in one Range from under a micrometer (≥ 100 nm) to the millimeter range (<1 cm). The structuring can also be carried out as a mixed form of roughening and ordered structure, as well as the transitions from highly disordered structuring to ordered structuring. The reflection element according to the invention thus has the effect that a multiple and not just single-directional reflection of the incident IR light beam takes place, it being possible for this to be diffuse and / or directional in accordance with the structuring. The diverse reflection is characterized by the fact that, compared to the simple reflection of a light beam on a smooth surface, it causes various different reflections, such as those caused by diffuse reflection in the extreme case. This light reflected by the reflection element always contains portions of the spectral diagnostic signature that can originate from an attenuated total reflection (ATR) as well as those that arise from other reflection processes through interaction with the sample. Since, according to the invention, the reflection element remains in the sample or a workpiece to be sampled (see below), a geometry or beam guidance as in pure ATR is not possible. However, the fact that the reflective element remains in the sample means the advantage of the method according to the invention, since the contact with the sample remains unchanged, as does the location to be sampled, which increases the comparability of measurements, is also guaranteed over a longer period of time. In the method according to the invention, this outweighs the reduction in the diagnostic signature in the reflected light.

The material from which the reflective element is made is at least permeable to part of the IR spectrum. The refractive index of the material of the reflection element is advantageously higher than that of the material of a sample to be examined. Materials that mostly meet the criteria are e.g. germanium (n = 4.0) and silicon (n = 3.4). In general, however, other higher refractive index and transparent infrared optical materials can also be used. The material used for the reflective element must be selected as required with regard to the properties, i.e. in particular the spectral range of characteristic IR absorption bands of a sample to be examined.

The thickness of the reflection element is advantageously between 0.1 and 5 mm, other dimensions are not a hindrance. The reflection element can be designed as round or square plates. The reflection element is advantageously designed to be rectangular. The dimensions are freely selectable and can be adapted to the corresponding upstream and downstream infrared optical means of the spectral analysis.

In the next step, b), of the method according to the invention, the reflection element according to the invention is arranged in a sample to be measured. The arrangement takes place in such a way that the reflection element is surrounded by the sample and the first surface is exposed, i.e. is openly accessible or accessible to an incident IR light beam. The first surface is advantageously flush with a sample surface, as also corresponds to an embodiment. In the context of the invention, flush means that the reflective element is covered or enclosed from the sample to the edges of its first surface and there is no offset or edge at the transition from the first surface of the reflective element to the surrounding sample. This is particularly advantageous with regard to the fact that, according to the invention, the reflective element remains in the sample and thus possible wear is reduced and the second surface remains in intimate contact with the sample in a reproducible manner.

The inventive method is accessible as samples, ie materials or substances or materials to be examined, which are at least viscous initially, ie at the start of a manufacturing process of the substances themselves or workpieces or components made from the substance. The viscosity can be reversible or irreversible, ie, for example, depending on the temperature, reversible or irreversibly solidified by reaction. The solidification can take place through intrinsic characteristics of the sample (eg solidification at a certain temperature) or it can be triggered externally (extrinsically, eg through an additive or a physical impulse such as UV light, microwaves, etc.). The sample is in a viscous state at the time of step b). All substances are to be regarded as viscous in the inventive sense, which have a dynamic viscosity η less than 10 ¹⁴ mPa · s or which are viscous enough to ensure intimate contact between the sample and the reflection element. According to the general definition, viscous materials in the sense of the invention are viscoelastic solids with a high percentage of viscosity, liquids and gases, ie fluids. The viscosity of the sample is the prerequisite that it completely wets the second surface of the reflection element, so that intimate contact between the sample and the reflection element is ensured.

Since the sample is in the viscous state at the time the reflective element is arranged, the intimate contact of the second surface with the sample is seamlessly fulfilled. The arrangement of the reflection element in a production form of a sample or a component takes place under the condition that the first surface is exposed or that the first surface is flush with the sample surface. As a result of the exposed first surface of the reflective element, infrared spectrometric measurement is already given, e.g. when filling a production mold for a component made from the sample, i.e. the material to be examined.

According to the invention, the reflective element is arranged in the sample to remain. As a result, starting with the point in time of the arrangement, t ₀ , it is possible to record IR spectra of the sample in reflection in series without the reflection element having to be arranged again on or in the sample. Spectra of the sample recorded in a chronological sequence can thus be better compared, since an error or a deviation from one measurement to the next, caused by insufficient or not precisely reproduced contact, and influences of the sample location do not have to be taken into account. If the sample is a component in which a reflective element according to the invention is arranged, a development of the component, such as, for example, solidification, as it also corresponds to an exemplary embodiment, or aging, under the constant conditions of always the same sample location and the same influence of contact between the sample and the sensor plate, at points in time t _x , which are after the point in time t ₀ , and thus increases the comparability the measurements and thus the precision, which justifies the advantage of the method according to the invention.

Point in time within the meaning of the invention is a fixed point in the course of the method, the position of which is described by time units (e.g. minutes, days, weeks) and is related to a zero point (here t ₀ ).

In the case that the sample solidified after or during the placing of the reflecting member, for example, by polymerization, this process is also from the time of solidification of t _1, which at the time t ₀ may coincide, especially if time t ₀ a Solidification has already begun to be followed up to any point in time t _x at which solidification has ended. The solidification can be intrinsic, for example solidification at a certain temperature, or extrinsic, for example by an additive or a physical impulse (for example UV light, microwaves, etc.). The recording of IR spectra using the reflection at any point in time t _x with the method according to the invention can be carried out up to a point in time at which the reflection element is damaged or destroyed or the entire component or sample is discarded. The time span of the measurements that can be carried out using the reflection element according to the invention without re-arranging such a device thus comprises time spans from a few seconds to one or more decades or more.

The following step c) of the method comprises irradiating the reflection element at any point in time t _x from point in time t ₀ (t ₀ inclusive) with IR light from the IR light source at an angle of incidence which is smaller than the total reflection angle at the transition ( first surface) from air to the material of the reflective element.

In step d), the spectrum of the IR light reflected at an interface between the second surface of the reflection element and the sample is analyzed with the means for spectral analysis and, if necessary, output for further processing, monitoring and logging, for example. The evaluation takes place in that the reflected light leaves the reflection element again through the first surface and is made accessible for a spectral analysis, e.g. with an IR spectrometer.

In one embodiment, a reference material to be measured is arranged in an additional method step e) so that it is to be measured in the same beam path of the method for obtaining reference spectra and the reference spectrum by irradiating IR light from the IR light source onto the reference material and Detection of the light reflected by this recorded by the means for spectral analysis. For this purpose, the reference material can be arranged permanently or reversibly on the reflective element or next to it. The recording of reference spectra for the calibration of spectrometric methods and the means and light sources used is known to the person skilled in the art and is common practice in IR spectrometry.

In the context of the invention, a reflection element for use in the method according to the invention is also specified, as has already been described above. The reflective element accordingly has the following features. A first surface that is flat and a second surface that is textured and parallel to the first surface. The structuring of the second surface causes a diverse reflection to take place on the second surface in contact with the material of a sample to be examined. In the simplest case, this means that the reflection takes place diffusely, which means for the structuring that it consists of a roughening of the second surface of the reflection element. Roughening can be achieved, for example, by sandblasting or etching. A structuring of the second surface of the reflection element, which brings about the condition of diverse reflection at an interface between the sample and the reflection element, can furthermore also be achieved by a directed and ordered structure. This type of structuring can be achieved, for example, by lithographic processes or processing of the surface with laser or electron beams, or in the manufacturing process by embossing. The structuring, roughening or ordered structure, with its characteristic dimensions of the depth or height of the structure-forming elements and their spacing, is in a size range from one nanometer (1 nm) to the millimeter range (<1 cm) and in particular in a range of below a micrometer (≥ 100 nm) down to the millimeter range (<1 cm). The reflection element according to the invention has the effect that a diverse reflection of the incident IR light beam or light takes place, diffuse or directional. The reflected light always contains components of the spectral diagnostic signature that originate from an attenuated total reflection (ATR) as well as those that arise from other reflection processes through interaction with the sample. Since, according to the invention, the reflection element remains in the sample or a workpiece to be sampled (see also above), a geometry or beam guidance as in pure ATR is not possible. The fact that the reflective element remains in the sample means the advantage of using it in the associated method according to the invention, since the contact with the sample and the location to be sampled remain unchanged, thereby increasing the comparability of measurements, is also guaranteed over a longer period of time. This outweighs the reduction in the diagnostic signature in the reflected light.

The special design of the reflective element, within the meaning of the invention, thus makes it possible to carry out the method according to the invention with the advantages of increased precision and the improved comparability of repeated measurements.

Furthermore, within the meaning of the invention, a component is also specified in which a reflection element according to the invention is arranged. Every component that is accessible to the inventive arrangement of a reflective element according to the invention is included. In particular, polymer-based components and composite materials (as materials to be appropriately sampled, i.e. samples) are included. The method is particularly advantageous to use on components that are subject to regular quality controls. This is particularly the case in vehicle construction, e.g. in aircraft.

Embodiments

The invention is explained in more detail below in two exemplary embodiments and with the aid of four figures.

• 1: Schematische Querschnittsdarstellung zur Veranschaulichung des erfindungsgemäßen Verfahrens, des erfindungsgemäßen Reflexionselement und des Bauteils bzw. einer Probe;
• 2: Mit dem erfindungsgemäßen Verfahren erhaltene zeitliche Verlauf von IR-Spektren (B) für den Aushärtungsprozess von Epoxidharz im Vergleich zu herkömmlich gewonnenen IR-Spektren (A). (Die Spektren sind entlang der y-Achse zur besseren Übersicht versetzt.)
• 3: Mit dem erfindungsgemäßen Verfahren erhaltenes Spektrum (-) im Vergleich zu einem mit Hilfe einer herkömmlichen ATR-Messzelle gewonnenem Spektrum (---) von Aceton. (Die Spektren sind zur besseren Übersichtlichkeit entlang der y-Achse versetzt.)
• 4: Rauheitsprofil der zweiten Oberfläche des für die Aufnahme der Spektren der 3 verwendeten Reflexionselements.

The figures show:

• 1 : Schematic cross-sectional representation to illustrate the method according to the invention, the reflection element according to the invention and the component or a sample;
• 2 : Time course of IR spectra (B) obtained with the method according to the invention for the curing process of epoxy resin compared to conventionally obtained IR spectra (A). (The spectra are offset along the y-axis for a better overview.)
• 3 : Spectrum (-) obtained with the method according to the invention compared to a spectrum (---) of acetone obtained with the aid of a conventional ATR measuring cell. (The spectra are offset along the y-axis for better clarity.)
• 4th : Roughness profile of the second surface of the for recording the spectra of the 3 used reflective element.

the 1 gives a schematic overview of the method according to the invention at a point in time t _x at which the reflection element 2 already in a rehearsal 1 is introduced and shows the sample to be examined or the component 1 , in which the reflective element according to the invention 2 with exposed first surface 6th is introduced. The one parallel to the first surface 6th lying structured second surface 3 of the reflective element is in intimate contact with the sample or the test material 1 . The optical coupling of the on the reflective element 2 incident IR light beam 4th from an IR light source (not shown) takes place at an angle of incidence y which is smaller than the angle of total reflection at the transition (first surface 6th ) from air to the material of the reflective element. For the sake of clarity and for illustration purposes only, this is just a reflection 5 shown. Due to the structure of the second surface 6th of the reflective element 2 and the diameter of a real IR light beam 4th multiple reflections occur in the process, caused at the multiple scattering centers, caused here by the structuring of the second surface, which is not true to scale 6th is illustrated schematically on. The reflected IR light 5 contains the spectral diagnostic signature of the sample, which is recorded, read out and evaluated by suitable means for spectral analysis, for example conventional spectrometers (not shown) and methods.

The course of the curing process of an epoxy resin is used as a first exemplary embodiment for the inventive method 1 at different times in the 2 shown. 2A shows conventional measurements and 2 B those obtained by the method according to the invention. For the last one, 2 B , the absorption spectra are obtained with the method according to the invention in situ on a mold of the epoxy resin during curing. As a reflective element 2 A 1 mm thick, non-doped so-called FZ (Flow Zone) (110) silicon plate with an area of 10 × 10 mm ² , in which the structured second surface is used 3 on one side of the reflective element 2 is provided with V-shaped trenches at a distance of 0.7 mm by means of photolithography. Anisotropic etching exposes the (111) surface of the silicon as trench edges at an angle of about 35 ° to the surface.

The IR light beam modulated by the source of a spectrometer as an IR source and by an interferometer 4th is placed with a plan mirror, as part of the IR light source, on the exposed first surface 6th of the reflective element according to the invention described in more detail above 2 mirrored so it's here with an angle of incidence γ of 40 ° occurs. Here is the plane of incidence of the IR light beam 4th parallel to the trench structure of the reflection element 2 aligned. Also with a plane mirror, as part of the means for spectral analysis, here a conventional IR spectrometer, is then used by the reflection element 2 reflected IR light 5 mirrored in the detector space of the spectrometer and measured the corresponding spectra. A reference spectrum is used on the sample immediately before each measurement 200 nm thick gold film produced with known coating methods on the reflective element 2 measured the part of the reflective element 2 occupies. The selection of the corresponding surface to be measured, reference material or first surface of the reflection element was made by laterally shifting the optics perpendicular to the plane of incidence.

the 2 compares spectra, degree of absorption vs. wave number recorded during the curing process of an epoxy resin. On the one hand, A, with the aid of an ATR crystal, as is known from the prior art, and on the other hand with the method (B) according to the invention. The spectra for both processes show the state at times t _x = 5 min (...) immediately after the resin has been stirred with the hardener and the casting mold has been filled (t ₀ ), at time t _x = 5 h (- -) as well as after a subsequent tempering at 120 ° C for 2 h (-). The respective spectra in 2 differ only insignificantly from one another and document that the method described here enables comparable statements on curing in relation to the established ATR method. From the change in the spectra, for the person skilled in the art, the course of the hardening is, for example, based on the ^{band change at about 900 cm −1} (oxal ring), band indicated by the arrow in FIG 2 A and B, clearly visible. Any subsequent chemical or structural changes to the component, for example caused by chemical or physical aging, temperature, mechanical stress or exposure to ionizing radiation, can be recognized by a person skilled in the art from the changes in other specific bands in the spectrum.

Recording a spectrum of a viscous sample (acetone) 1 with the help of the reflective element according to the invention 2 as a second embodiment is explained below. As a reflective element 2 a 0.38 mm thick, non-doped so-called FZ (Flow Zone) (100) silicon plate with an area of 10 × 10 mm ² , which was cut out of a commercial Si wafer, is used. The Si wafer has a polished (first surface 6th ) and a production-related rough surface, second and structured surface 3 , with one in the 4th shown roughness profile. The rough second surface 3 of the reflection element forms the structured second surface 3 and is in direct contact with the viscous sample 1 . The IR light beam modulated by the source of a spectrometer as an IR light source and by an interferometer 4th is placed on the exposed first surface with a plan mirror, as part of the IR light source 6th of the reflective element according to the invention described in more detail above 2 mirrored so it's here with an angle of incidence γ of 40 ° occurs. Also with a plane mirror, as part of the means for spectral analysis, here a conventional IR spectrometer, is then used by the reflection element 2 reflected radiation 5 mirrored in the detector space of the spectrometer and measured the corresponding spectra. The reference spectrum is used immediately before the measurement of the sample 1 the unwetted reflective element 2 measured. the 4th shows the absorption spectrum (-) obtained according to the invention in comparison with a spectrum (---) measured in a commercial ATR cell. The high comparability of the spectra is obvious.

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• DE 102006036808 A1 [0005]
• DE 102016215449 A1 [0006]

Claims (7)

IR spectrometric method comprising at least the steps: a) providing an IR light source and a means for spectral analysis and a reflection element (2) which has at least a first surface (6) which is flat and a second surface (3) which is structured and parallel to the first surface, and wherein the structuring effects a diverse reflection of an incident IR light beam and wherein the reflection element (2) is made of a material which is at least partially permeable to IR light (4, 5), b) arranging the reflective element (2) to remain in a viscous sample (1) to be measured at time t ₀ , the first surface (6) of the reflective element (2) being exposed, c) irradiating the reflective element (2) on the first Surface (6) with an IR light beam (4) at any point in time t _x from point in time t ₀ at an angle of incidence (y) which is smaller than the angle of total reflection, d) Aufne hmen the spectrum of the IR light (5) reflected at an interface between the second surface (3) of the reflective element (2) and the sample (1) with the means for spectral analysis. IR spectrometric method according to Claim 1 , characterized in that the reflection element (2) is arranged in step b) such that the first surface (6) is flush with a surface of the sample (1). IR spectrometric method according to Claim 1 , characterized in that the structure of the second surface (3) of the reflective element (2) consists of a roughening of the surface. IR spectrometric method according to Claim 1 , characterized in that the structure of the second surface (3) of the reflection element (2) is formed by an ordered structure. IR spectrometric method according to Claim 1 , characterized in that in an additional step e) a reference material is arranged and a reference spectrum for calibrating a beam path is recorded on this. Reflection element (2) for use in a method according to Claim 1 , at least comprising a first surface (6) which is flat and a second surface (3) which is structured and parallel to the first surface (6) and wherein the structuring effects a diverse reflection of an IR light beam and the reflection element (2) is made of a material which is at least partially transparent to IR light (4, 5). Component from one of the material classes composite material or polymer having at least one reflective element (2) according to Claim 6 to carry out a procedure according to Claim 1 .

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