Device and method for optically capturing data relating to a biological structure

Abstract

The invention relates to a device (1) for optically capturing data relating to a biological structure, comprising: a light source (2) for providing illumination radiation (BS) of at least one wavelength, and a plurality of optical waveguides (5) as illumination waveguides (5.1) for guiding the illumination radiation (BS) by means of total reflection to a sample location (9) and for emitting the illumination radiation (BS) at the sample location (9). In addition, at least one optical detection waveguide (5.2), for guiding detection radiation (DS) emitted at the sample location (9), and a detector (3), for detecting the detection radiation (DS), are provided. The device (1) is characterised in that the illumination waveguides (5.1) each comprise an out-coupling region (7) that is expanded within a portion of the length of the particular illumination waveguide (5.1), via which region the illumination radiation (BS) can be coupled out at least in part from the illumination waveguide (5.1) and can be diffusely emitted at the sample location (9). The invention also relates to a method for optically capturing data relating to a biological structure.

Description

[0001] Device and method for optically acquiring data from a biological structure

[0002] The invention relates to a device for optically detecting data of a biological structure according to the preamble of the independent claim and to a method according to the independent claim.

[0003] A number of devices for the optical acquisition of data from biological structures are known from the prior art (e.g., WO 1 998 / 038907 A1; US ​​2010 / 0228124 A1). These devices typically emit directed illumination light along a preferred direction to either directly acquire image data or to generate suitable detection radiation, which can subsequently be detected and evaluated. For example, it is known to label biological structures with excitable molecules (fluorophores). Alternatively, existing autofluorescence of the biological structure in question can be utilized to generate detection radiation. Devices for optical acquisition can be temporarily attached to the biological structure or permanently arranged there (e.g., WO 2021 / 050843 A1).

[0004] A disadvantage of the state-of-the-art methods and devices is that direct illumination can damage the biological structure. Furthermore, the acquired data may be difficult to reproduce even with a slight change in the illumination angle or a change in the biological structure, for example, when it grows, differentiates, or changes its condition.

[0005] The invention is based on the object of proposing a possibility for the optical acquisition of data of a biological structure by means of which the disadvantages of the prior art are reduced.

[0006] This object is achieved by means of a device for optically acquiring data from a biological structure according to the independent and subordinate claims. Advantageous developments of the invention are the subject of the dependent claims.

[0007] The device comprises a light source for providing illumination radiation of at least one wavelength. A plurality of optical light guides, for example in the form of a bundle, serve as illumination light guides for guiding the illumination radiation to a sample location. The illumination radiation is emitted at this location. The guiding occurs essentially by means of total internal reflection at a wall of the light guide. The total internal reflection can be determined by the cross-section of the light guide and the refractive power of a cladding of the respective light guide, wherein the refractive power can be matched to the wavelength or wavelength range of the illumination radiation. Furthermore, at least one optical detection light guide is provided for guiding detection radiation emitted at the sample location, which is guided to a detector that serves to capture the detection radiation.

[0008] The device is characterized in that the illumination light guides each have an outcoupling region which extends within a section of the length of a respective illumination light guide and through which the illumination radiation is at least partially outcoupled, wherein an undirected, diffuse emission of the outcoupled illumination radiation to the environment, that is to say in particular to the sample location, can take place or takes place.

[0009] A key concept of the invention lies in the non-directional or diffuse emission of the illumination radiation, which ensures uniform illumination of a sample location and can generate a signal across a large spatial sector. Furthermore, diffuse illumination relieves the user of the invention of the task of precisely directing the illumination or monitoring its direction over a recording period.

[0010] Of importance for the invention is the diffuse emission of the illumination radiation over the entire coupling-out region, if possible. Diffuse illumination can be achieved, for example, by modifying the cross-section of the illumination light guide and / or its cladding across the extent of the coupling-out region. This modification at least partially eliminates total internal reflection there. For example, a cross-section can be modified to couple out a portion of the illumination radiation guided in the light guide by having it partially strike the outer wall of the light guide at angles that do not cause total internal reflection. The choice of optical properties, such as the refractive index of the cladding used, or the local omission of such a cladding, can also support the emission of the illumination radiation.

[0011] In the following, optical fibers are referred to as illumination fibers if they carry illumination light to the sample location. Detection fibers are fibers that carry detection radiation to a detector. If the specific function is not relevant in a technical context, they are also referred to as optical fibers for simplicity.

[0012] To advantageously promote diffuse illumination of a sample location, the illumination light guides can form a planar or spatial structure, at least in sections, preferably over the length of the respective output region. Thus, each or a number of light guides can be configured as a coil, in which the light guides are intertwined in a non-directional manner, at least over the length of the output region.

[0013] In a further possible embodiment, the light guides can be arranged in a directed manner, at least in sections, preferably over the length of a respective output region, and form a planar or spatial structure. For example, the illumination light guides can be separated and guided as a loop. They can also be laid, woven, or wound parallel to one another or crossing one another in at least one layer around a shaping base body ("dummy") so that they enclose it in a regular pattern. The base body can preferably be removed again, in particular after completion of the spatial structure and optionally after fixing the illumination light guides to (elastically) maintain the spatial structure even without the shaping base body.The base body is advantageously elastically deformable, plastically deformable or disassemblable into several individual parts in order to be able to remove it from the spatial structure or to adapt the spatial structure to the shape of a specific sample location.

[0014] One possibility for effectively utilizing the available material and installation space within the scope of the invention is to continue the optical fibers as detection optical fibers after the planar or spatial structure formed by the output region. This avoids the illumination optical fibers terminating in more or less pointed individual fibers. Such fiber ends would be disadvantageous, on the one hand, because a large portion of the illumination radiation would exit from them in a more or less directed manner, which would contradict the goal of diffuse illumination. On the other hand, fiber ends are fragile and would also adversely affect the usability of the device as an implant (see below) due to their potential tissue irritation.

[0015] To achieve high flexibility and a low risk of breakage, the light guides are preferably made of a polymer. For example, PMMA fiber cores (PMMA = polymethyl methacrylate) with a biocompatible coating can be used.

[0016] If, in one embodiment of the invention, the light source and the detector are to be arranged close to one another, for example to enable a compact design of the device, the light guides can be bent after or already in the coupling-out region, wherein the detection light guides are arranged, for example, substantially parallel to the course of the plurality of illumination light guides.

[0017] In order to couple detection radiation from the sample location into at least a number of the optical fibers, these fibers have a coupling region. In one embodiment of the device according to the invention, the coupling region is formed by a collection optic. This can be present, for example, at a fiber end of a detection optical fiber and can be designed, for example, as an optical lens.

[0018] Within the scope of the invention, however, it is more advantageous if the illumination light guides are continued as detection light guides after the decoupling region and either the decoupling region essentially functions as the coupling region at the same time or the decoupling region and the coupling region follow one another.

[0019] Depending on the wavelength of the detection radiation to be captured, it can enter the optical fibers in a combined coupling and decoupling region due to the modified cross-sections and / or sheathing, if present at all. The guidance of the coupled detection radiation toward the detector again occurs according to the well-known principle of total internal reflection. For example, the detection optical fiber can have a modified cross-section within the coupling region, preferably as a result of a polished section. The polished section creates an optical window through which detection radiation can couple into the detection optical fiber.

[0020] To further increase the efficiency of the coupling and / or decoupling, it is conceivable that at least one optical diffraction grating is arranged or formed within the coupling and / or decoupling region, which is adapted to the respective illumination radiation and / or detection radiation. For example, by applying or incorporating a diffraction grating on or into the respective optical fiber, the efficiency of the coupling of detection radiation can be wavelength-selectively adjusted to the respective detection radiation, and furthermore, (re-)coupling of illumination radiation or other parasitic radiation can be prevented or reduced.

[0021] If the individual optical fibers are arranged in a known pattern to the spatial structure, as described above, and the respective coupling-out or coupling-in areas extend only over known sectors of the planar or spatial structure, an approximate localization of the origin of the detected detection radiation can be achieved.

[0022] For this purpose, it is advantageous if the detection fiber optics or bundles of these are each assigned exclusively to specific detector elements of a spatially resolving detector, for example, a detector with a CCD, CMOS, or sCMOS chip. This allows a detected signal to be assigned to a specific detection fiber optic or bundle of detection fiber optics. If the spatial arrangement of the respective fiber optics or their coupling areas is known, an approximate location of the signal's origin can be determined.

[0023] If it is important for subsequent signal evaluation, at least one additional optical fiber without an input and output region can be arranged and act as a reference fiber. Such a design can, for example, evaluate signal contributions that enter the optical fiber outside the input region.

[0024] Furthermore, an optical filter or beam splitter can be arranged in front of the detector. This filter is transparent to the respective detection radiation but blocks radiation of other wavelengths or deflects it away from the detector, for example, in the direction of a beam trap. The device according to the invention can be used as an implant. In this application, it is advantageous if a power supply source for the light source and / or the detector, in particular an energy storage device, is present that can be charged without contact. Additionally or alternatively, the light source and / or the detector can be controlled without contact, for example via Ethernet, Bluetooth, or the like. Likewise, the image data acquired by the detector can advantageously be read out without contact and, for example, transferred to an external storage device.

[0025] Furthermore, the optical fibers used advantageously allow the coupling-out and coupling-in regions to be spatially separated from the light source and / or the detector. For example, the coupling-out and coupling-in regions can be located within an organ and require only a small amount of space, while the light source and detector are arranged at remote locations, for example, in the subcutaneous fat. The latter also supports the contactless power supply, control, and / or data transmission described above.

[0026] As already mentioned, the device according to the invention can advantageously be used as an implant. One particularly advantageous use of the device is its use in a method for monitoring surgical fields, in particular resection cavities, of human or animal bodies.

[0027] The network formed by the illumination light guides can advantageously grow into the tissue being observed and even serve as a supportive structure for new cell growth. The light guides, whether illumination or detection, can also be loaded with radioactive particles and / or drugs, for example, to achieve a desired effect on the cells or tissue directly on site.

[0028] In addition, the light source can be controlled in such a way that, depending on the acquired image data and their analysis, the wavelength and / or the intensity of the illumination radiation is adjusted in order to produce desired effects in the observed biological structure.

[0029] A positive effect of the device according to the invention can also be the support of other imaging methods. For example, the light guides can increase the contrast or orientation during imaging using other methods.

[0030] The device according to the invention can be used in a method for optically acquiring data from a biological structure. The method comprises the steps of providing illumination radiation of at least one wavelength and guiding the illumination radiation to a sample location using a bundle of optical fibers serving as illumination light guides. The guiding occurs essentially as a result of total internal reflection at a wavelength defined by the cross-section and by a sheath of a respective optical fiber. The illumination radiation is emitted to the sample location along an output region of the illumination light guide, with the illumination being non-directional, i.e., diffuse.

[0031] A detection radiation caused by the effect of the illumination radiation is then detected by coupling it into the optical fiber at a coupling area of ​​the respective illumination optical fiber and feeding it to a detector as detection radiation.

[0032] The detection radiation can be a tissue-specific reaction to the illumination radiation used. It is known that a number of endogenous compounds exist in biological tissues that can be excited to autofluorescence with a suitable wavelength and intensity of illumination radiation. The emitted fluorescent radiation can enter the detection light guides via the respective coupling areas and be detected.

[0033] It is also known from the prior art to add substances to a biological structure that can either be directly excited to emit fluorescent radiation (fluorophores or fluorescent markers) or that lead to the formation and, if necessary, selective accumulation of excitable and fluorescent compounds in the metabolism of living biological structures. A well-known example is 5-aminolevulinic acid. This is more highly accumulated in tumor cells and tumor-like cells than in healthy cells and is converted to protoporphyrin IX. In this way, the presence of autofluorescent cells and / or specifically labeled cells, such as tumor cells and tumor-like cells, can be detected using the device according to the invention and by carrying out the method according to the invention.Other substances that can be used within the scope of the invention are, for example, ICG (indocyanine green), as well as polyaromatic hydrocarbons or heterocycles.

[0034] It is also possible to specifically influence marked cells using illuminating radiation of a selected wavelength, intensity, and / or pulse frequency. This can utilize endogenous and / or externally applied and possibly enriched substances present in the cells, which, in response to the applied illuminating radiation, can stimulate or damage the cell. For example, heating of specific cells (hyperthermia) can be achieved.

[0035] The detection radiation can be evaluated based on its spectral composition and / or the recorded intensities of selected wavelengths. It is advantageous to register and optionally store the occurrence of at least one selected wavelength of the detection radiation and / or the reaching of a threshold value of the intensity of a selected wavelength. The threshold values ​​can be determined in advance, for example, experimentally or using a suitable simulation.

[0036] Advantageously, spatial localization of the origin of a signal indicating a tumor, for example, can be omitted. The mere presence of such a signal can be used as a trigger for subsequent investigations.

[0037] In a further embodiment of the invention, hyperspectral imaging (HSI) can also be used as an analysis technique for the purpose of evaluating the light signals or the detection radiation. This analysis technique involves recording hundreds of images with different wavelengths for the same spatial area. The collected data forms a so-called hyperspectral cube, in which two dimensions represent the spatial extent of the scene and the third its spectral content. Since each tissue area has a specific spectral signature, this can be used as a "fingerprint" for its unique identification. The key advantage of hyperspectral imaging in the present invention is its unobtrusive, label-free, and non-destructive ability to detect different components of tissue or tissue.to distinguish between different biological structures. The method according to the invention can also be used particularly advantageously in the field of inflammation management. The insertion of medical implants into the human body, for example, long-term implants in the form of pacemakers, neuroimplants, hip and knee prostheses, or catheters, can lead to counterproductive adsorption of nonspecific biomolecules and undesirable tissue encapsulation of the biomaterial used, thus resulting in the loss of function of the implant. Even though various approaches to maintaining the function of implants are currently being used, an acute or chronic response of the human organism cannot be ruled out.

[0038] The device according to the invention, in conjunction with the implant inserted into the human or animal body, can be used particularly advantageously for the detection of inflammatory reactions, biofouling, macrophages, and fibroblasts in postoperative tissue structures. The detection of the tissue structures surrounding or contacting the implant can occur automatically at predefined intervals or can be initiated.

[0039] The invention is explained in more detail below using exemplary embodiments and figures. They show:

[0040] Fig. 1 is a schematic representation of a first embodiment of a device according to the invention with a design of the coupling-out regions in the form of a loop;

[0041] Fig. 2 is a schematic representation of a second embodiment of the device according to the invention with the coupling-out regions designed as a regular planar network;

[0042] Fig. 3 is a schematic representation of a third embodiment of a device according to the invention with a design of the coupling-out regions as a first regular spatial structure;

[0043] Fig. 4 shows a schematic detailed representation of a fourth embodiment of the device according to the invention with the decoupling regions configured as a second regular spatial structure; Fig. 5 shows a schematic detailed representation of a fifth embodiment of the device according to the invention with the decoupling regions configured as an irregular spatial network;

[0044] Fig. 6 is a representation of a use of the device according to the invention according to the second embodiment as an implant in a method for optically acquiring data of a biological structure; and

[0045] Fig. 7 is a representation of a use of the device according to the invention according to a further embodiment as an implant in a method for the optical acquisition of data of a biological structure.

[0046] The exemplary embodiments presented below are simplified and not shown to scale. In the following, identical technical elements are identified by identical reference numerals.

[0047] A device 1 according to the invention has, as essential technical elements, a light source 2 for providing an illumination radiation BS of at least one wavelength, a detector 3 for detecting a detection radiation DS, and a plurality of optical light guides 5 (Fig. 1). These are designed, starting from the light source 2, as illumination light guides 5.1 for guiding an illumination radiation BS to a sample location 9. The illumination light guides 5.1 have, over a portion of their length, an output region 7 which is designed to emit the illumination radiation BS to the sample location 9. After the output region 7, the light guides 5 are designed as optical detection light guides 5.2 which serve to guide a detection radiation DS, preferably detected at the sample location 9. The guidance of the illumination radiation BS in the illumination light guide 5.1 and of the detection radiation DS in the at least one detection light guide 5.2 occurs essentially as a result of total internal reflection at a wall of the light guide 5. The total internal reflection is determined by the cross-section of the light guide 5 and the refractive power of a sheath of the respective light guide 5. The output coupling region 7, which serves as the emission region of the illumination radiation BS, causes a diffuse emission of the illumination radiation BS to the environment (symbolized in the figures by thin arrows without reference symbols). Either following the output coupling region 7 or functionally forming a unit with it, there is an input coupling region 8, across whose extent a detection radiation DS coming from the environment, for example from the sample location 9, can be coupled into the light guide 5. The detection radiation DS that thus reaches the detection light guide 5.2 is guided to the detector 3 and detected there.The light source 2 and / or the detector 3 are connected to an energy storage device 4, in particular a battery or a rechargeable accumulator, in a manner suitable for the transmission of electrical energy.

[0048] Light source 2, detector 3 and energy storage 4 are advantageously surrounded by a housing.

[0049] In the illustrated embodiments, the illumination light guides 5.1 are arranged as bundles. These are separated and looped across the output region 7 and the input region 8. This provides a large surface area for the emission of the illumination radiation BS and the input of the detection radiation DS.

[0050] From the end of the coupling area 8, the individual detection optical fibers 5.2 are again guided as a bundle, which serves to increase the stability of the optical fibers 5 and reduce signal loss.

[0051] According to a second embodiment of the device 1 according to the invention, the output coupling regions 7 and the input coupling regions 8 of the optical fibers 5 form a regular planar network (Fig. 2). Such a design is suitable, for example, for optically acquiring data from a narrow but extended sample location 9, for example, a pocket or fold of a biological structure.

[0052] If a more pronounced three-dimensional spatial sample location 9 is to be illuminated, the output coupling regions 7 and the input coupling regions 8 can be designed as a regular spatial structure. For this purpose, the individual optical fibers 5, or smaller bundles thereof, can be arranged around a base body 6 in this region. Depending on the measurement task to be performed by the device 1, this base body 6 can be a permanent component of the device 1. In further embodiments, the base body 6 can also serve for the regular, or in any case a predetermined, arrangement of the optical fibers 5 along their output coupling and input coupling regions 7, 8, as well as for their stabilization during positioning of the device 1. After positioning, the base body 6 can be removed, so that only the optical fibers 5 remain at the sample location 9.In further embodiments, the base body 6 serves to shape the structure during the production of the spatial structure and is removed again after completion of the spatial structure. The actual structure, for example, to be used as an implant, is used, for example, as a hollow oval or in the shape of a hollow net ball.

[0053] Figure 4 shows another embodiment of the coupling-out regions as a further regular spatial structure. Alternatively, the base body 6 can also be made of a flexible material and, for example, be deformed during positioning to achieve a smaller cross-section and thus easier positioning.

[0054] Due to their regular arrangement of the light guides 5, the embodiments illustrated in Figures 1 to 4 enable an approximate localization of the origin(s) of the detected detection radiation DS, provided the orientation of the output coupling regions 7 and / or input coupling regions 8 of the respective light guides 5 relative to one another and to the sample location 9 is known. For this purpose, the detector 3 can be designed as a spatially resolving detector 3, for example in the form of a CCD, CMOS, or an array of individual detectors, e.g., photodiodes. Each detection light guide 5.2 ending at the detector 3 is precisely and exclusively assigned to one detector element or specific detector elements (not shown). The information about the detector elements actually detecting the detection radiation DS can thus be used for localization.

[0055] In a fifth embodiment of the device 1 according to the invention, the coupling-out regions 7 and the coupling-in regions 8 are formed as an irregular spatial network (Fig. 5). In such a form of the invention, positioning can be carried out particularly easily and a large surface area of ​​the optical fibers 5 is achieved, which supports uniform diffuse illumination and efficient detection of the detection radiation DS.

[0056] In all of the aforementioned embodiments, the coupling-out regions 7 and the coupling-in regions 8 of each optical fiber 5 can follow one another. Such a design has advantages when the origin of the detected detection radiation DS is to be localized.

[0057] In all of the above-mentioned embodiments, it is also possible for the decoupling regions 7 to simultaneously function as coupling regions 8.

[0058] Fig. 6 shows the use of the device 1 according to the invention according to the third embodiment (see Fig. 3) as an implant in a method for optically acquiring data from a biological structure. The device 1 is implanted in the body of a patient, with the coupling-out and coupling-in regions 7, 8 being arranged in a resection cavity in the patient's brain. By means of an emission of illumination radiation BS that is controlled with regard to the time intervals, illumination and acquisition duration, as well as the wavelengths and intensities used, a detection radiation DS can be generated and acquired at the sample location 9. The acquired data can be transmitted instantaneously and contactlessly to a device located outside the body.

[0059] The data can be transmitted to the receiving unit 10. Alternatively, the detector 3 can have a readable data memory. These can, for example, be read out and forwarded in blocks by the receiving unit 10 (indicated by an arrow).

[0060] If the receiving unit 10 is appropriately equipped and configured, it can also transmit control commands to the device 1 and / or serve for the contactless charging of the energy storage device 4 (see Fig. 1 to 3).

[0061] In a further illustration of a use of the device 1 according to the invention as an implant in a method for optically acquiring data from a biological structure, a connector 11 that can be contacted extracorporeally is provided. If a plug connection to an external receiving unit 10 is established by means of this connector, data and control commands can be transmitted, as well as the energy storage device 4 can be charged.

[0062] A further possible embodiment consists in using the connector 11 when required and via it to supply the illumination radiation BS to the optical fibers 5 from an external light source 2 and / or to direct a detection radiation DS onto a detector 3 which is also arranged externally.

[0063] Reference symbol

[0064] 1 device

[0065] 2 Light source 3 Detector

[0066] 4 energy storage

[0067] 5 light guides

[0068] 5.1 Lighting light guide

[0069] 5.2 Detection fiber optics 6 Base body

[0070] 7 Decoupling area

[0071] 8 Coupling area

[0072] 9 Sample location

[0073] 10 Receiver 1 1 Plug

[0074] BS illumination radiation

[0075] DS detection radiation

Claims

Patent claims 1 . Device (1 ) for optically detecting data of a biological structure, comprising - a light source (2) for providing an illuminating radiation (BS) of at least one wavelength; - a plurality of optical light guides (5) as illumination light guides (5.1) for guiding the illumination radiation (BS) by means of total reflection to a sample location (9); at least one optical detection light guide (5.2) for guiding a detection radiation (DS) emitted at the sample location (9) by means of total reflection; and - a detector (3) for detecting the detection radiation (DS); characterized in that the illumination light guides (5.1) each have an outcoupling region (7) extending within a section of the length of the respective illumination light guide (5.1), via which the illumination radiation (BS) can be at least partially outcoupled from the illumination light guide (5.1) and diffusely emitted to the sample location (9).

2. Device (1) according to claim 1, characterized in that at least some of the illumination light guides (5.1) within the coupling-out region (7) have a modification of their cross-section and / or their sheath, whereby the total reflection is at least partially canceled there.

3. Device (1) according to claim 1 or 2, characterized in that the light guides (5) form a planar or spatial structure over the length of the coupling-out region (7).

4. Device (1) according to claim 3, characterized in that the light guides (5) are continued as detection light guides (5.2) after the planar or spatial structure.

5. Device (1) according to one of the preceding claims, characterized in that at least a number of the optical fibers (5) each have a coupling region (8) along which detection radiation (DS) from the sample location (9) can be coupled into the respective optical fiber (5).

6. Device (1) according to claim 5, characterized in that the coupling region (8) is formed by a collecting optic, by an optical grating and / or by a modification of the cross section of the light guide (5).

7. Device (1) according to claim 5, characterized in that the coupling-in region (8) is equal to the coupling-out region (7).

8. Device (1) according to one of the preceding claims, characterized in that at least one further optical fiber (5) is arranged without a coupling-out region (7) and a coupling-in region (8) and serves as a reference conductor.

9. Device (1) according to one of the preceding claims, characterized in that an energy storage device (4) is provided for supplying the light source (2) and / or the detector (3) with electrical energy, wherein the energy storage device (4) can be charged contactlessly.

10. Use of a device (1) according to one of the preceding claims as an implant. 1 1. Use of a device (1) according to one of claims 1 to 10 in a method for detecting inflammatory reactions of postoperative tissue structures after the introduction of implants into the human or animal body. 1 2. Use of a device (1) according to one of claims 1 to 10 in a method for monitoring surgical fields, in particular resection cavities of human or animal bodies. 1 3. A method for optically acquiring data from a biological structure, comprising the steps: Providing an illumination radiation (BS) of at least one wavelength; Guiding the illumination radiation (BS) by means of a bundle of optical fibers (5) serving as illumination optical fibers (5,1) to a sample location (9); - emitting the illumination radiation (BS) along a coupling-out region (7) of the illumination light guide (5.1) to the sample location (9), wherein the illumination is undirected; Detecting a detection radiation (DS) caused by the effect of the illumination radiation (BS) by coupling it into the respective optical fiber (5) at a coupling region (8) and feeding it to a detector (3) as detection radiation (DS).

14. The method according to claim 1 3, characterized in that the detection radiation (DS) is evaluated with regard to its spectral composition and / or the detected intensities of selected wavelengths, wherein the occurrence of at least one selected wavelength of the detection radiation (DS) and / or the reaching of a threshold value of a selected wavelength is registered.

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