Arrangement and devices configured for carrying out optical absorption spectroscopy

An implantable fluorescent concentrator is configured to be inserted in vivo as a subcutaneous light source for optical absorption spectroscopy of surface-near tissue layers. As a result, certain and reliable results of the optical absorption spectroscopy are achievable. Furthermore, various analytes with different absorption properties are certainly and reliably quantifiable.

This application claims priority under 35 U.S.C. §119 to patent application number DE 10 2013 201 275.6, filed on Jan. 28, 2013 in Germany, the disclosure of which is incorporated herein by reference in its entirety.

BACKGROUND

The disclosure relates to an arrangement having devices that permit optical absorption spectroscopy to be carried out.

The absorption spectrum of living tissue, in particular skin, has relatively low light absorption over wide ranges and is therefore generally accessible to spectroscopy with corresponding light wavelengths. One technical difficulty here is the strong scattering of the light in tissue. Depending on the wavelength, the light can travel distances of a few centimeters in the tissue, but covers such distances only via numerous scattering processes. The propagation of light in the tissue corresponds to a diffusion process rather than to the light propagation of straight-line rays. Owing to this uncertainty relating to the optical paths in the tissue, carrying out spectroscopy in the tissue becomes more difficult. The resulting results may be falsified in the process. It might also be the case that weakly absorbing particles (for example molecules, ions, electrons) as analytes in very small concentrations can be quantified with difficulty or hardly at all. Glucose, for example, is such a weakly absorbing molecule.

There is thus a continued need for improved procedures and devices for carrying out optical absorption spectroscopy. It is desirable, for example, to reliably quantify different analytes independently of their absorption strength despite the strong scattering of the light in the tissue.

SUMMARY

The present disclosure is essentially specified by the features described below. Further configurations of the present disclosure can be gathered by way of example from the below description.

The idea of the present disclosure is to place the light source that is necessary for carrying out the absorption spectroscopy under the skin surface in the manner of an implant. Such a light source should as far as possible be a point-type light source and emit light only in the direction of the detector detecting the light from the light source. The present disclosure in this case realizes the light source as a fluorescent concentrator. Here, a fluorescent dye is applied onto a transparent plate or is embedded into the material of the plate. Light that is incident through the skin surface excites the dye to isotropically emitted fluorescence. Since the emission takes place within the material, a majority of the light remains trapped inside the plate due to total internal reflection, as in the case of an optical waveguide, and can be coupled out as far as possible in a point-type fashion at a location that is intended therefor. On account of the fact that the light source according to the disclosure is realized in the form of a fluorescent concentrator, the light source can concentrate diffuse light, as is present also in the tissue after emission through the skin surface. The fluorescent concentrator captures the light that is incident into the tissue with its entire surface, converts it into fluorescent light having a greater wavelength, and emits it from approximately a point in the direction of the detector at the skin surface. Once detected, the emitted fluorescent light can be evaluated using the known methods of absorption spectroscopy.

Despite the strong scattering of the light in the tissue, the present disclosure makes it possible for various analytes to be reliably quantified independently of their absorption strength. Furthermore, the results of the absorption spectroscopy are reliable because the present disclosure is able to collect and concentrate the light that is scattered diffusely within the tissue well and emit the light required for the absorption spectroscopy with greater wavelengths in the direction of the skin surface. The wavelengths of the light emitted by the light source according to the disclosure are greater than those of the light that is absorbed by the light source according to the disclosure. In addition, no energy supply for the light source is necessary for carrying out the absorption spectroscopy.

DETAILED DESCRIPTION

FIG. 1shows an arrangement1according to one embodiment of the present disclosure. The arrangement1has, according to the present embodiment, a device11(as the abovementioned light source), which: is configured to be inserted under a skin surface10; has a fluorescent layer112, wherein the fluorescent layer112is configured to absorb light13that is emitted onto the skin surface10and to convert the absorbed light into fluorescent light; has a fluorescent-light-emitting region113which is configured to absorb the fluorescent light and to emit it in the direction of the skin surface10(see the arrows having the reference sign14). The fluorescent layer112can, for example, be formed on a side of the device11facing the skin surface10. According to the present embodiment, the device11furthermore has a substrate111. The fluorescent layer112can be formed for example on the substrate111. The fluorescent light absorbed in the substrate111(see reference sign14″) and supplied to the fluorescent-light-emitting region113. The region113, which emits the fluorescent light14″,14, couples out the fluorescent light14″,14absorbed in the device11and emits it in the direction of the skin surface10. Since the device11is inserted under the skin surface10, it may also be referred to as an implant. The examination of the tissue, of the fluids, and/or of the particles located between the device11and the skin surface10is made possible and improved by the device11. As already mentioned, the problem of strong scattering of the light under the skin surface10frequently occurs in the case of examinations using light, which makes spectroscopy of the tissue, of the fluids, and/or of the particles more difficult. According to the present disclosure, a large portion of the light scattered under the skin surface10is absorbed by the device11, so that the portion of the light which is scattered under the skin surface10in another way remains small and can no longer negatively influence the result of the spectroscopy. Owing to total internal reflection in the device11(for example in its plate or in the substrate111), the absorbed light remains trapped as fluorescent light in the device11, in the manner of an optical waveguide, and is coupled out only at the location of the device11that is intended therefor—in the fluorescent-light-emitting region113—and is emitted in the direction of the skin surface10. The present disclosure realizes the device11as a fluorescent concentrator, which can concentrate diffuse light. The fluorescent light emitted by the device11(that is to say by the fluorescent-light-emitting region113) in the direction of the skin surface10can be differentiated easily from the light14′ emitted through the skin surface10in another way, which considerably increases and improves the reliability of the results of the spectroscopy. The light14′ emitted through the skin surface10in another way can comprise light that is emitted by the device11in another way, that is to say is not emitted by the region113and/or emitted otherwise by the tissue. For evaluating the fluorescent light emitted by the device11, various known methods of absorption spectroscopy can be used, for example. Furthermore, no energy supply is necessary for the device11with the present disclosure. The device11can moreover remain (as an implant) in the body or under the skin surface10generally unlimited time period, as a result of which the examinations of the tissue, the fluids, and/or the particles can be repeated at any time and as a result of which the examinations can be carried out simply and without further actions.

For irradiating the skin surface10and thus for supplying the light13to the device11through the skin surface10, the arrangement1according to the present embodiment has a light-detecting device12. According to the present embodiment, the light-detecting device12is configured to emit light13onto the skin surface10and to receive the fluorescent light14which was emitted by the device11according to the disclosure. The fluorescent light14that was emitted by the device11according to the disclosure is used by the light-detecting device12to evaluate the emitted fluorescent light14. The device11only emits the fluorescent light14after the light13is emitted onto the skin surface10. According to the present embodiment, this therefore occurs in response to the emission of the light13by the light-detecting device12.

According to the present embodiment, the light-detecting device12has at least one light-emitting element121, which is configured to emit light13onto the skin surface10. The light-detecting device12furthermore has at least one light-receiving element122, which is configured to detect and to receive the fluorescent light14which was emitted by the device11(that is to say by the region113thereof intended therefor). The light-detecting device12can, after it receives the fluorescent light14, evaluate it or provide it to a further device intended therefor for evaluation. The light-detecting device12can be a probe, for example. The at least one light-emitting element121can be, for example, an optical fiber configured for lighting. The at least one light-receiving element122can be, for example, an optical fiber configured for detecting the received fluorescent light14.

FIG. 1shows the device11in a state in which it is inserted or implanted under the skin surface10. The exact depth or thickness of the skin layer depends on the field of use of the arrangement1with the two devices11and12. The tissue to be examined spectroscopically is located between the device11(for example the implant11) and the light-detecting device12(for example a probe12) disposed on the skin surface10. Using the light-detecting device12, light13(also referred to as excitation light below) is irradiated into the skin10and spreads diffusely in the tissue. The device11collects (using the fluorescent layer112) a large portion of the light13irradiated into the skin10, converts it (using the fluorescent layer) into the fluorescent light14′, and radiates the obtained fluorescent light14′,14in the direction of the light-detecting device12.

The device11can have a flat-surface configuration, as a result of which the device11obtains an improved property of light absorption, i.e. the device11can collect or absorb more of the light13that is emitted onto the skin surface10and distributed in the tissue.

The fluorescent-light-emitting region113can be smaller than the side of the device11facing the skin surface. In this case, the fluorescent-light-emitting region113is smaller than the fluorescent layer112. As a result, the fluorescent light14which is emitted by the device11(or by the region113) according to the disclosure can be differentiated better from the light14′ which is emitted in another way through the skin surface10. The fluorescent-light-emitting region113can be configured here such that it constitutes, viewed from the light-detecting device12, a nearly point-type light source arranged in the tissue, which light source can be used for absorption spectroscopy of the tissue located between the two devices11and12, the fluids located between the two devices11and12, and/or the particles located between the two devices11and12. In this manner, the light14′, which is trapped in the device11, is coupled out and emitted in a point-type fashion through the region113(see arrows14). The absorption spectroscopy of the fluorescent light14emitted according to the disclosure can then be carried out by the light-detecting device12or another suitable device using methods known therefor.

According to the present embodiment, the wavelength of the emitted (by the fluorescent-light-emitting region113) fluorescent light14is greater than the wavelength of the absorbed (by the fluorescent layer112) light13. Here, the absorption and emission bands of the fluorescent agent used for the fluorescent layer112overlap spectrally only partially and preferably not at all. In this manner, the fluorescent light14emitted by the device11according to the disclosure and the light14′ scattered back in another way by the tissue and by the device11can be differentiated well using known methods of spectroscopy. The light-detecting device12can have a filter element2, which transmits the fluorescent light14emitted by the device11for evaluation by the light-detecting device12and blocks other light14′ emitted by the skin surface10. An exemplary embodiment of the light-detecting device12with the filter element2is shown inFIG. 2. The filter element2can be arranged on the side of the light-detecting device12which is aligned with the skin surface10, in front of the light-receiving element122. The filter element2can be, for example, a spectral edge filter, which blocks light having wavelengths below the fluorescence band of the device11. Use of the filter element2, which is made possible by the differentiability of the fluorescent light14emitted by the device11(or by the region113), explained above, ensures that only the light that is indeed to be examined is used for the evaluation using spectroscopy, in particular using absorption spectroscopy. Thus the significance, certitude, reliability of the evaluated values are increased. Overall, the examination of the tissue, of the fluids, and/or of the particles between the skin surface10and the device11becomes more precise and simple.

FIG. 3shows the spectral relationships between the light absorbed by the fluorescent layer112and the fluorescent light14emitted according to one embodiment of the present disclosure. The horizontal axis here shows the wavelength λ in nm, and the vertical axis indicates the strength of absorption or emission, wherein the wavelength λ is given on the horizontal axis in an ascending order (from left to right). According toFIG. 2, the fluorescent layer112absorbs the light13irradiated through the skin surface10in a region31which covers the region32of the light13emitted by the light-detecting device12. The fluorescent light14is emitted according to the present embodiment in a region33which is different or separate from the absorption region31and comprises the characteristic absorption bands34of the analyte (that is to say of the tissue to be examined, of the fluid to be examined, and/or of the particles to be examined).

FIG. 4shows the spectral relationships between the light which is radiated back in another way (for example14′ inFIG. 1), which was radiated back after irradiation using the light13from the light-detecting device12, and the fluorescent light14emitted by the device11(or by the region113) according to one embodiment of the present disclosure. The emitted fluorescent light14is here locally attenuated by the absorption by the analyte (that is to say of the tissue to be examined, the fluid to be examined, and/or the particles to be examined). InFIG. 4, the region41belongs to the other light which is radiated back (for example14′ inFIG. 1), and region42belongs to the emitted fluorescent light14, which is locally attenuated owing to the absorption by the analyte. In region42, the fluorescent signal with absorption lines of the analyte is shown. The axes inFIG. 4correspond to the axes inFIG. 3.

According to one embodiment of the present disclosure, the device11or the substrate111of the device11is made of a high-refractive (high-n) material. The refractive index of the material of the device11or of the substrate111is preferably greater than the refractive index of the surrounding biomaterial or of the surrounding tissue, respectively. This supports the differentiability between the fluorescent light14emitted by the device11and the other light14′ emitted via the skin surface10, since the total internal reflection occurs owing to media at the boundary surfaces to high-refractive media, that is to say in this case at the boundary surfaces from the tissue to the device11or to the substrate111of the device11, respectively. In this manner, the reliability of the results of the spectroscopy and in particular of the absorption spectroscopy during examination of the emitted fluorescent light14is increased. If, for example, the refractive index n for the tissue-fluid is given as n=1.36, this could have the following refractive indices for the device11or for the substrate111for example for the following used materials: for glass, the refractive index n=1.52, for plastic such as for example polymethyl methacrylate (PMMA) the refractive index n=1.49, for plastic such as polystyrene the refractive index n=1.58. It should be noted here that the above specifications of the materials and the associated refractive indices are merely exemplary and that the present disclosure permits use of other suitable materials and/or other suitable refractive indices. In principle, the refractive index of the device11or of the substrate111should be as large as possible, in any case greater than the refractive index of the biological material (of the tissue) surrounding the device11.

According to one embodiment of the present disclosure, the fluorescent layer112has a refractive index which is comparable with the refractive index of the device11or of the substrate111, for example is the same or approximately the same. As a result, Fresnel reflections at the boundary surface between the materials of the layer112and of the substrate111are minimized and unobstructed conduction of the light14″ to the coupling-out location113is ensured.

The fluorescent layer112can be one of the layers configured as follows: a layer made of a fluorescent dye or a layer configured from the material of the substrate111or the device11and from a fluorescent dye, wherein the fluorescent dye is embedded in the material of the substrate111or of the device11. The present disclosure permits certain flexibility in relation to the configuration of the fluorescent layer112. The above-mentioned possible configurations of the fluorescent layer112support the property of differentiability of the fluorescent light14emitted by the device11(or by the fluorescent-light-emitting region113) and the light14′ emitted in another way. Furthermore, the reliability of the results obtained after evaluation of the emitted fluorescent light14is increased. If, for example, the material of the substrate111or of the device11is PMMA, the PMMA can be dyed using a fluorescent dye to form the fluorescent layer112. In such a case, a separation of substrate111and fluorescent layer112is no longer absolutely necessary—instead, the substrate111can also be dyed homogeneously with the fluorescent dye, and a fluorescent layer112which can be differentiated from the substrate can be omitted entirely. Therefore, the present disclosure permits an embodiment with a layer (with111and112) in which the substrate111and the fluorescent layer112are connected or combined by dying or introducing the fluorescent dye in the material of the substrate111. The present specification deals with both layers—the substrate111and the fluorescent layer112—separately for reasons of clear and concise illustration, but also comprises the embodiment with just one layer connecting or combining the layers111and112. Here, the features, advantages, functions and further configurations of the substrate111and of the fluorescent layer112are also accordingly comprised by the one layer comprising both layers111,112.

The absorption and emission bands of the fluorescent agent or of the fluorescent dye overlap spectrally only partially or not at all, as a result of which the above-mentioned properties of differentiability of the emitted fluorescent light14from the otherwise emitted light14′ and reliability of the results of the evaluation of the emitted fluorescent light14are likewise ensured and supported. For example, the fluorescent agent or the fluorescent dye can absorb the light13emitted onto the skin surface only in a limited spectral range and emit it by way of fluorescence with high quantum efficiency (for example greater than 90%) in a likewise limited spectral range separate from the absorption band. The fluorescent agent or the fluorescent dye can be, for example, a laser dye, a neon color (for example for highlighters) or a substance based on organic dyes such as perylene or naphthalimide. Alternatively, quantum dots can be used to form the fluorescent layer.

Generally, the choice of fluorescent agent or of fluorescent dye should be made in correspondence with the respective use. In order to support and to ensure the positive effects of the present disclosure, the absorption band of the fluorescent agent or of the fluorescent dye should include the wavelength of the light13irradiated through the skin surface10. The emission band of the fluorescent agent or of the fluorescent dye should include the wavelengths required for spectroscopy. For example, the emission should be configured to have as broad a band as possible and include one or more characteristic absorption bands of the analyte to be measured (completely or nearly completely or as completely as possible).

According to one embodiment of the present disclosure, the fluorescent-light-emitting region113is one of the regions configured as follows: a roughened region, and/or a region covered with scattering particles, of a surface of the substrate111or of the device11that extends with the skin surface, or a light-scattering region in the volume of the substrate111or of the device11. The regions113, which are configured in this way and emit the fluorescent light, permit a point-type emission or a nearly point-type emission of the fluorescent light14, as a result of which the above-mentioned properties of differentiability of the fluorescent light14emitted by the device11(or by the fluorescent-light-emitting region113) and of the light14′ emitted in another way. Furthermore, the reliability of the results obtained after evaluation of the emitted fluorescent light14is increased.

The above-mentioned positive effects (differentiability, reliability) of the roughened region113and/or the region113covered with scattering particles is based on a disturbance of the total internal reflection in the region113. The positive effect is amplified according to one embodiment by the fact that the device11or the substrate111has a reflector at a side of the fluorescent-light-emitting region113facing away from the skin surface10and/or that the fluorescent-light-emitting region113is formed on a surface of the substrate111or of the device11facing away from the skin surface10. The reflector is used to additionally direct the scattered light in the direction of the skin surface10.

If the fluorescent-light-emitting region113is a light-scattering region in the volume of the substrate111or of the device11, it may be formed for example by microscopically small air inclusions or microcracks in the substrate111or in the device11. If, for example, glass is the material used for the substrate111or the device11, microscopically small air inclusions or microcracks in the substrate111or in the device11can be formed by using internal laser engraving. If, for example, plastic is used as the material for the substrate111or the device11, the fluorescent-light-emitting region113can be formed by embedding a scatter body in the volume of the substrate111or of the device11.

FIG. 5shows an embodiment of the device11which is insertable under the skin surface according to one further embodiment of the present disclosure. It should be noted here that each of the further components of the device11shown inFIG. 5can be used alone and/or in combination with at least one further one of the components shown inFIG. 5for configuring the device11.FIG. 5shows the device11with all further components which are possible according to the present disclosure, so as to keep the description short and clear.

According to the present embodiment, the device11has a mirror51at least at one front end of the device11or at least at one edge face of the device11, respectively, wherein the at least one mirror51is configured to reflect fluorescent light14″ propagating within the layer112or substrate111, which fluorescent light14″ would otherwise exit the device11at the relevant edge or front end since it does not meet the prerequisites for total internal reflection. The front end or the edge face of the device11is the side or face of the device that does not extend (substantially parallel) with the skin surface10. Rather, it extends counter to the skin surface10, for example substantially perpendicular with respect to the skin surface10. The device11has at least one mirror51. Light rays13,14″ that extend at flat angles with respect to the plane of the device11or of the substrate111, and are therefore reflected totally at the upper or lower side of the device11, strike the edge face under relatively steep angles and can be coupled out there. This can be prevented by making these surfaces reflective (for example a metallic, preferably silver or gold reflective coating). In this way, the light14″, which is trapped in the device11, is prevented from radiating out. As a result, the amount of the other light14′ emitted by the tissue is reduced, which ultimately results in better differentiability between the light14emitted by the device11(or by the fluorescent-light-emitting region113) and the other light14′ emitted from the tissue and entails better results for the evaluation of the emitted fluorescent light14.

According to the present embodiment, the device11has, on that side of the device11which faces the skin surface, a fluorescent-light-controlling layer52. The fluorescent-light-controlling layer52is formed over the fluorescent layer112. Here, the fluorescent-light-controlling layer52is substantially transparent for the light13emitted onto the skin surface10and substantially reflective or absorbing for the emitted fluorescent light14. The fluorescent-light-controlling layer is configured to direct the emission of the fluorescent light14to a specific position on the skin surface10.

According to the present embodiment, the fluorescent-light-controlling layer52is open with respect to the fluorescent-light-emitting region113(see opening54inFIG. 5) such that the fluorescent light14emitting from the fluorescent-light-emitting region113is emitted to the specific position on the skin surface10. Here, the fluorescent light14is emitted through the opening54of the fluorescent-light-controlling layer52in the direction of the skin surface10. Even though the light is coupled out according to the present disclosure mainly at the scatter zone or in the fluorescent-light-emitting region113, since the fluorescent light14is emitted isotropically, the coupled-out light is, however, not completely subject to total internal reflection. With a correspondingly steep angle with respect to the boundary surface between the device11and the surrounding area of the device11, light rays of the fluorescent light14″ produced by the fluorescent layer can exit the device11. Scattering at usually unavoidable material defects can also result in undesired coupling out of the fluorescent light14″ produced by the fluorescent layer. With the use of the fluorescent-light-controlling layer52, the emission of the produced fluorescent light14can be achieved completely at the location intended therefor or on the fluorescent-light-emitting region113. According to the present embodiment, the fluorescent-light-controlling layer52is located between the fluorescent layer112and the skin surface10, for example on the fluorescent layer112. If the device11is surrounded by an encapsulation material, which will be explained in more detail below, the fluorescent-light-controlling layer52can also be formed on its surface. The fluorescent-light-controlling layer52is open above the fluorescent-light-emitting region113(see opening54). Moreover, the divergence of the emitted fluorescent light14can be set by way of the relationship of the radii of the opening54of the fluorescent-light-controlling layer52and of the fluorescent-light-emitting region113.

The fluorescent-light-controlling layer52can be formed for example by dielectric interference filters. By way of a targeted configuration of a sequence of dielectric layers with varying refractive indices, it is possible to set the reflection and transmission behavior of such layer systems virtually as desired. The relevant high low or bandpass filters are available and usable for all spectral ranges.

Furthermore, the fluorescent-light-controlling layer52can be formed for example by transparent conductive layers. Here, the fluorescent-light-controlling layer52can be formed for example from transparent conductive metal oxides (TCO materials), such as for example variously doped indium zinc or zinc oxides. These have the property of transparency, exhibit good transmission properties in the visible spectral range, and at the same time are good reflectors in the near infrared. The plasma frequency is then important for the position of the reflection edge.

Moreover, the fluorescent-light-controlling layer52can be formed using dye systems. To this end, any dye (organic, inorganic or quantum dots), whose absorption band includes the emission band of the fluorescent dye used in the implant but not the wavelength of the excitation light, is suitable. The dye should furthermore return into its ground state without radiation after irradiation via the skin surface10or emitted in a spectral range irrelevant for the spectroscopy, wherein this spectral range does not overlap with the emission spectral range of the fluorescent light14emitted by the device11(or by the fluorescent-light-emitting region113). The above-described fluorescent-light-controlling layer52can also be referred to as a spectrally selective layer (SSS).

According to the present embodiment, the device11is encapsulated or overmolded in a low-n material53. It is difficult to configure a component consisting of various materials to be biocompatible. This, however, should be done with respect to the device11, since the device11is intended for implantation under the skin surface10and should therefore be biocompatible. That is to say, the organism and its tissue must not be damaged by the device11. Furthermore, the upper and boundary surface quality which is decisive for the optical functionality can hardly be maintained for a longer period of time. For example, a living organism will damage most foreign bodies electromechanically within a short period of time or at least cover it with a protein film. Both influence the boundary surface reflections. One solution to this problem is to encapsulate the device11in a material53which causes no physiological damage and is resistant to biochemical attacks. Crucial for the optics is the quality of the protected internal boundary surfaces. The quality of the encapsulation surface is irrelevant and can certainly be rough, since the surrounding area of the device11(that is to say the tissue) already has a very strongly scattering effect. The refractive index of the encapsulation material53should be as close as possible to the refractive index of the surrounding tissue so as to minimize the optical action of the boundary surface. If this is not possible, the refractive index of the encapsulation material53should preferably be smaller than that of the surrounding tissue.

According to a further embodiment of the present disclosure, it is possible to select, instead of the fluorescent-light-controlling layer52or the spectrally selective layer (SSS)52, an encapsulation material53which absorbs the fluorescent light14. That is to say, with a suitable encapsulation material53, the configuration of the device11with the fluorescent-light-controlling layer52may also be omitted. In this case, transparency must nevertheless be produced at or over the fluorescent-light-emitting region113. This can be achieved for example by way of a locally thinner encapsulation layer or an encapsulation layer of different composition over the fluorescent-light-emitting region113. This encapsulation layer which is configured differently locally would be arranged at the same position as the location of the opening54in the fluorescent-light-controlling layer52.

FIG. 6shows an arrangement1according to one embodiment of the present disclosure. The arrangement1inFIG. 6corresponds to the arrangement1inFIG. 1, with the exception that the device11has an element61which aligns the device11, with which the device11can be aligned noninvasively under the skin surface10. The device11can generally be configured as illustrated in the present application.

The element61aligning the device11can, for example, be a ferromagnetic element. It may be, for example, a plate under the transparent material53, a ring surrounding the device11, or a type of “trough” enclosing the transparent material53on all sides (except for the side facing the skin surface10). With the application of a magnetic field (for example using electromagnets or permanent magnets on the light-detecting device12), a force can be exerted on the device11in a non-invasive manner for pulling the device11in the direction of the light-detecting device12located on the skin surface10and/or aligning it with respect to the light-detecting device12. If the ferromagnetic element61itself has a permanent magnetic moment, it is also possible to impart torque in a non-invasive manner.

According to one embodiment of the present disclosure, unique positioning of the device11with respect to the light-detecting device12can be assured by noninvasively transferring forces and/or torques using the aligning element61.

According to one embodiment of the present disclosure, the device11can be pulled toward the light-detecting device12using the aligning element61, as a result of which the tissue located between the two devices11,12is compromised and as a result of which the portion of blood and tissue fluid in the tissue located therebetween is reduced. By periodically attracting and releasing the device11to and from the light-detecting device12, the tissue located therebetween can be measured alternately with various fluid portions. This is useful in particular for separating influences of tissue and fluids on the absorption spectrum.

According to one embodiment of the present disclosure, the device11can be vibrated (briefly) using the aligning element61before the optical measurement. As a result, local diffusion processes can be accelerated and chemical gradients in the direct neighborhood of the device11can be homogenized. Periodically attracting and repelling the device11with respect to the light-detecting device12arranged on the skin surface10flushes the tissue located therebetween by periodically “flooding” and “squeezing” the fluids in the tissue.

According toFIG. 6, the light-detecting device12has an aligning element62which is configured to noninvasively align the device11under the skin surface such that a side of the light-detecting device12which emits the light and receives the fluorescent light is substantially above the side of the device11which absorbs the light and emits the fluorescent light.

The present disclosure also permits further embodiments in which the layers, regions of the device11, which are responsible for collecting the irradiated light13and for emitting the fluorescent light14, are geometrically separated. In this way, spatial separation of the two light intensities is achieved such that for a corresponding configuration of the light-detecting device12, no light14′ scattered back in another way by the tissue can enter the light-detecting device12or be received by the light-detecting device12.

FIG. 7shows a configuration of the device11which is insertable under the skin surface according to one embodiment of the present disclosure. The device11and thus also its substrate111consist, according to the present embodiment, of an optical fiber (or of another optical waveguide), one portion71of which is provided with a fluorescent layer112and which collects the light13radiating through the skin surface10using the fluorescent layer112. Alternatively, the portion71can also be dyed homogeneously with the fluorescent agent, and one layer may be dispensed with.

According to the present embodiment, the fluorescent portion71connects to a further portion72without the fluorescent layer112, wherein in this embodiment the further portion72is optional. At the end of the fiber11, the fluorescent light14exits. This end can be regarded as the above-described fluorescent-light-emitting region113. According to the present embodiment, the end piece or the fluorescent-light-emitting region113has a rough surface so as to emit the fluorescent light14away from the fiber axis (in the direction of the skin surface10and in the direction of the light-detecting device12) in an amplified manner. This embodiment of the device11can be used well for example in a weakly scattering tissue, since the device configured according to the present embodiment makes it possible to increase the portion of ballistic photons at the skin surface10which reach the skin surface10without scattering in a straight line through the tissue. The higher concentration of the emitted fluorescent light14is a result of a considerably greater length of the fiber part71which has the fluorescent layer112and collects light with respect to the coupling-out end piece113.

The above-explained embodiments with the specific aspects explained there can be combined with one another. The present disclosure makes possible diverse combinations of the above-described layers of the light source11according to the disclosure. Said combinations were not listed in their entirety owing to their large number and for the purposes of precise illustration of the present disclosure, but are clear to the person skilled in the art in view of the description. With the aid of the present disclosure, as it is described, an implantable fluorescent concentrator is inserted in vivo as a subcutaneous light source for optical absorption spectroscopy of surface-near tissue layers. As a result, certain and reliable results of the optical absorption spectroscopy can be achieved. Furthermore, various analytes with different absorption properties can be quantified certainly and reliably. The present disclosure relates to the device configured as a light source, a light-detecting device which detects the light emitted by the light source for the purposes of optical absorption spectroscopy, and an arrangement having the device configured as a light source and the light-detecting device.