LIGHTING SYSTEM WITH A LIGHT GUIDE WITH A DIFFUSER ELEMENT

Description

[0001] The invention relates to a lighting system comprising at least one light source, a light guide and an optical element, which is preferably designed as a diffuser element and is arranged at a distal end of the light guide, so that light from the light guide can be coupled into the optical element.

[0002] These types of lighting systems are increasingly used in medical settings. Currently, the following main areas of application can be identified: Photodynamic therapy (PDT) or photoimmunotherapy (PIT) for tumor therapy, endovenous laser therapy (EVLT) for the treatment of varicose veins, laser-induced interstitial thermotherapy (LITT) and other applications, including in the fields of dentistry, ophthalmology and dermatology, or for the treatment of epilepsy.

[0003] Photodynamic therapy (PDT) is a minimally invasive treatment option for various types of cancer. PDT is a procedure used to treat tumors and other tissue abnormalities (such as neovascularization) with light in combination with a light-activated substance. At the start of treatment, patients are intravenously injected with light-sensitive substances, known as photosensitizers, which accumulate in or on the cancer cells. These naturally occurring photosubstances concentrate in the tumor cells, causing them to become highly sensitive to light. During PDT treatment, several cannulas (typically up to eight) are inserted into the tumor tissue. Each cannula must contain a light source, ideally distributed across the tumor tissue.Laser light, usually with wavelengths in the visible spectrum, for example, green light at 532 nm or red light at 690 nm, illuminates the tumor tissue as evenly as possible from within. This process generates aggressive oxygen radicals in these cells, which selectively destroy the tumor cells. Unlike the diseased cells, healthy cells should remain unaffected by this chemical reaction. The precise mechanism of action is described, among other places, in "Photodynamic Therapy of Cancer," Cancer Medicine, 2003. In contrast, photoimmunotherapy (PIT) uses a specially modified photosensitizer to trigger an immune response in or on the cancer cell, which, upon exposure to light, leads to the death of the cancer cell.

[0004] Light sources are typically categorized as either cylindrical diffusers or spot diffusers, which produce a forward-directed beam of light, or point sources, which emit light radially. For cylindrical diffusers, the most important factor during operation is achieving the most homogeneous possible lateral emission along their length. Both axially, meaning at every point along each line from the proximal to the distal end in the direction of the longitudinal axis, the emission intensity is the same, and radially, meaning at every point along each circumferential line in the direction of the longitudinal axis, the emission intensity is approximately the same, thus making cylindrical diffusers behave almost like Lambertian radiators.

[0005] At the same time, achieving high scattering efficiency is also advantageous to ensure minimal heat input into the tissue. Forward radiation, particularly from the distal end, should be avoided. Typical laser power in PDT applications is less than 5 W continuous power, resulting in a maximum output of between 100 mW and 1000 mW per cm of diffuser length, typically between 200 mW and 500 mW.

[0006] Existing examples include diffuser elements made of a thin silicone cylinder into which scattering particles are embedded. German patent DE 10129029 A1 describes a flexible device for the thermal ablation of biological tissue using laser radiation, comprising a laser-carrying optical fiber whose distal end is surrounded by a sheath that is transparent or opaque to the laser radiation and extends beyond the fiber end. However, these devices can only be manufactured with sufficient emission homogeneity at a very complex and costly rate, as conglomerates of scattering particles often result in emission spots where the intensity is significantly above average.

[0007] Optical fibers with diffuser elements are sometimes used only once and discarded after each use. This creates cost pressure regarding manufacturing costs. Therefore, reusable solutions are increasingly being considered. Such solutions must be reprocessable according to established standards, for example, disinfectable and / or sterilizable. Reprocessing methods include cleaning / disinfection with strongly alkaline solutions and sterilization by autoclaving at temperatures up to 135°C and typical steam pressures of approximately 3 bar. Typically, several tens to several hundred such reprocessing cycles are expected. This necessitates high standards for thermal, chemical, and hydrolytic resistance.

[0008] In EVLT, the physician inserts a catheter into the affected vein through a tiny puncture site. This catheter serves as a guide for the vein laser. The laser energy is then emitted laterally via a diffuser, intensely heating the inner wall of the vessel, causing the vein to collapse and close. This prevents the abnormal backflow of venous blood. Subsequently, the vein hardens, shrinks, and can be absorbed by the body. Typically, so-called ring or double-ring fire systems are used as the light source. To ensure even treatment, the laser element is often manually moved through the vein segment at a constant speed. This makes the application more difficult, as further cell damage can occur if the laser is not applied or remains in one area for too long.

[0009] Laser-induced interstitial thermotherapy (LITT) is a minimally invasive procedure used for local tumor destruction. Under imaging guidance (e.g., ultrasound / MRI), the tumor is punctured, one (or more) laser fiber(s) are inserted into the tumor, and the tumor is destroyed by thermal energy. Nd:YAG lasers (1064 nm) and diffuser-tip applicators are primarily used. The laser power is approximately 5 to 8 W (see "Laser-induced interstitial thermotherapy (LITT) in malignant tumors", German Medical Association and National Association of Statutory Health Insurance Physicians, January 2002).

[0010] Another type of diffuser, particularly one that scatters light volume, is described, for example, in EP 3184885A1. This describes a diffuser at the end of a quartz glass optical fiber, whereby the diffuser is created by applying a scattering material to the distal end of the fiber and solidifying it to form the diffuser. A disadvantage of such approaches is that these volume-scattering methods result in a strongly exponential decrease in intensity. Furthermore, porous materials are not preferred in medical technology applications due to their reprocessability.

[0011] In US patent 6,810,184 B2, an approach is described in which nanoporous silicon dioxide-clad optical fibers are used to produce fibers with integrally formed diffusion peaks that can be fused with other fibers. EP 2062077 A4, US 2009 / 0204111 A1, and DE 102015119875 A1 describe diffusers in which structures are embedded in or applied to the fiber using a laser for their creation.

[0012] WO 2008 / 024397 A2 presents, among other things, a diffuser for emitting high-power-density optical energy to a treatment point at the distal end of at least one optical fiber. It is provided that scattering centers are arranged along the predetermined length of the fiber core or in or near an interface between the fiber core and the cladding along the predetermined length.

[0013] However, the approaches presented above have the disadvantage that, with sufficiently homogeneous design of the scattering centers, the lateral radiation is not achieved with the homogeneity required in the medical environment due to the exponential decay of the lateral emission or uneven distributions.

[0014] US 2009 / 0204111 A1 describes a laser delivery system comprising an optical fiber with a core and a cladding layer covering at least part of the core, the cladding layer having a lower refractive index than the core, and a non-feature section and a feature section with features that cause the light to propagate radially from the feature section, creating a desired radial light output pattern. The features are selected from the group consisting of helical structures, radial cuts, axial cuts, and a combination thereof.

[0015] DE 102015119875 A1 describes an optical waveguide comprising a waveguide core, a region in the optical waveguide, wherein micro-modifications are arranged in the region of the optical waveguide and wherein the arrangement of the micro-modifications is ordered.

[0016] WO 2019 / 063799 A1 describes a lighting system, particularly for a medical therapy and / or diagnostic system, comprising at least one laser light source, a light guide that can be connected to and / or assigned to the at least one laser light source at a proximal end, and a diffuser element at the distal end of the light guide with a longitudinal axis that runs perpendicular to an input surface of the light guide into or within the diffuser element. The diffuser element emits light laterally to the longitudinal axis over its active length, and the diffuser element comprises at least one diffuser base body, and the diffuser base body includes at least one scattering element.The lighting system includes a device for homogenizing the emission intensity along the longitudinal axis of the diffuser body, wherein, in the operating state, the lighting system exhibits an intensity distribution of the lateral emission that deviates from the mean lateral emission intensity by at most ± 50%, preferably at most ± 30%, and most preferably at most ± 5%. Therefore, cylindrical diffusers with very homogeneous emission along their length can be realized, which also exhibit high efficiency and low self-heating, making them particularly advantageous for PIT and PDT applications.

[0017] As mentioned previously, many applications in the medical technology field can also irradiate and thus damage healthy tissue, which is usually directly adjacent to the tissue being irradiated. Therefore, efforts are being made to protect this tissue from unwanted radiation exposure in the future.

[0018] EP 0 761 257 A2 describes a probe for laser irradiation used in a medical laser device for performing laser treatment by irradiating a human or animal with laser light or beams. The laser probe includes, in particular, a laser light reflector positioned between the transparent light diffuser and a protective diffusion tube.

[0019] WO 2017 / 174549 A1 describes an irradiation system comprising a radiation source and a coupling unit for coupling the radiation from the radiation source into a front end region of an optical fiber for transmission to an output coupling unit located at a rear end region of the optical fiber. The irradiation system is intended for irradiating materials in industrial processes for heating, polymerization, curing, and / or disinfection with IR and / or UV radiation. US 4,466,697 A describes optical elements with core structures for light emission or transmission. An optical fiber comprises an inner core made of light-conducting plastic or glass, which is provided with an outer cladding layer. The cladding layer may have a defect at which light emission occurs.

[0020] The object of the invention is therefore to enable improved irradiation of unhealthy tissue, which meets the special requirements in a medical technology environment and in particular protects healthy tissue, so that unwanted physical damage to persons is avoided.

[0021] This task is solved by the subject matter of the independent claims. Advantageous further developments are specified in the respective dependent claims.

[0022] Accordingly, the invention relates to a lighting system for a medical therapy and / or diagnostic system, particularly for use on living tissue, comprising at least one light source, an optical fiber that can be connected to or associated with the light source at a proximal end, and an optical element, preferably designed as a diffuser element and arranged at a distal end of the optical fiber, such that light from the optical fiber can be coupled into the optical element. For the purposes of the invention, a diffuser element is understood to be a light-scattering body, in particular a body that guides light and can preferably emit it in different directions. The light can be emitted diffusely or directionally, in particular in a direction that is transverse, diagonal, perpendicular, or parallel to the direction in which the light is coupled into the optical element.The optical element comprises a light-reflecting region and a light-transmitting region, wherein the light-reflecting region exhibits at least partial reflectivity and the light-transmitting region exhibits at least partial transmission, in particular high spectral transmission, preferably up to a wavelength of approximately 2.5 µm. Light coupled into the optical element is at least partially reflectible at the light-reflecting region. This reflection can be diffuse or specular. At the light-transmitting region, light, in particular the aforementioned reflected light, can be at least partially coupled out of the optical element. In particular, the light-reflecting region exhibits a higher reflectivity than the light-transmitting region.Preferably, the reflectivity of the light-reflecting area is at least 30, more preferably at least 50, more preferably at least 70 percentage points higher than that of the light-transmitting area. Preferably, the optical element is covered at least partially with at least one reflector layer, particularly in the light-reflecting area, to give the light-reflecting area at least partial reflectivity. Preferably, the optical element remains free of the reflector layer at least partially, particularly in the light-transmitting area, to give the light-transmitting area at least partial transmissivity. The reflector layer can cover a surface and / or a lateral surface of the optical element. Furthermore, according to the invention, the reflector layer comprises a mirror layer.The optical element can therefore have a lateral surface which is at least partially covered by a light-reflecting reflector layer, preferably a mirror layer, wherein the optical element has a light-reflecting area which is covered by the reflector layer and a light-transmitting area which preferably remains free of the reflector layer, so that the light emitted by the optical element is at least partially reflectable, and light can be emitted from the light-transmitting area. In particular, light can thus be selectively emitted from the light-transmitting area. The term "lateral surface" refers in particular to a surface of the optical element. According to the invention, the reflectivity of the reflector layer is greater than 90% for at least one wavelength range. According to the invention, the reflector layer is designed as a mirror layer.The wavelength range for which the reflector layer is designed can preferably include the visible spectral range (VIS) between approximately 400 nm and approximately 700 nm, e.g., in particular between 400 nm and 450 nm or between 600 nm and 700 nm, as well as the infrared range (IR) between approximately 700 nm and approximately 2.5 µm, in particular the near-infrared range (NIR) between approximately 700 nm and approximately 1200 nm, e.g., 980 nm or 1064 nm. Wavelengths in the near-UV range between approximately 350 nm and approximately 400 nm are also conceivable. However, the light-transmitting or light-reflecting area can also be designed such that a definable wavelength range or a definable principal wavelength is transmitted or reflected, respectively. Preferably, this predefinable range is exceeded by no more than 20 nm, preferably by no more than 10 nm, preferably by no more than 5 nm.Such a definable range can, for example, encompass wavelengths of a specific color, particularly green or red. By having the optical element, on the one hand, an at least partially light-reflecting area and, on the other hand, an at least partially light-transmitting area, wherein the light-reflecting area has a higher reflectivity than the light-transmitting area, it can advantageously be achieved that light emission at the light-reflecting area is reduced or avoided, while light emission at the light-transmitting area is increased or restricted to it. This advantageously enables more targeted light emission, in particular to irradiate diseased tissue while simultaneously protecting adjacent healthy tissue.In particular, the reflector layer, which is applied only to sections of the diffuser element, allows the light to be selectively emitted onto uncovered areas. This enables targeted irradiation during medical treatment, for example, allowing only diseased or irradiated tissue to be irradiated. Tissue can also be selectively ablated by energy input, such as in a LITT application. Adjacent healthy tissue is thus protected from irradiation and ideally remains undamaged. In one embodiment, the light can be emitted or coupled out transversely to a longitudinal axis of the optical element and laterally along an active length of the optical element. If the optical element is designed as an optical waveguide, it can advantageously guide light in a predetermined direction, for example, along the longitudinal axis.In the context of this disclosure, lateral emission is understood to mean emission that has directional components extending radially from the longitudinal axis of the diffuser element. Lateral emission intensity is understood to be the intensity of this emission. The geometry of the emission can be adapted by a corresponding geometric adjustment of the reflector layer, so that, for example, stripe-shaped or lens-shaped patterns can be projected onto the tissue surface to be treated. It is therefore advantageous if at least one area of ​​the diffuser element not covered by the reflector layer, for example, a recess in the reflector layer, extends along the longitudinal direction of the diffuser element and this uncovered area is transparent, so that light guided by the diffuser element can be emitted in a stripe-shaped, and in particular a linear, pattern.The transmissive area can be linear or non-linear. A linear radiation pattern allows for sectional radiation, so that the tissue to be irradiated is not a point source, but rather a larger area, while simultaneously keeping this area within defined limits to protect surrounding tissue. More complex radiation geometries can be achieved by appropriately adapting the reflector layer geometrically, possibly in combination with the geometry of the optical element. For example, gradual zones are also possible, in which case the reflector layer can be less pronounced, particularly with lower reflectance, in a defined area than in a highly reflective area.However, geometries are also conceivable in which, for example, a translucent, especially strip-shaped, area widens or narrows in one direction, such as a longitudinal direction. In this case, a strip-shaped, lens-shaped, or oval area can extend lengthwise along, across, and / or diagonally to the longitudinal axis of the optical element.

[0023] Ideally, the diffuser element is elongated or rod-shaped so that it can be inserted into a catheter, for example. The diffuser element can also have a substantially circular, oval, or polygonal cross-section (e.g., hexagonal, rectangular, or square); star-shaped forms are also possible. In these cases, the light is preferably emitted laterally via the facets or radial surfaces. The reflector layer, applied to the diffuser element only in sections or facets, thus enables the light to be emitted laterally in only a specific direction or into a defined section.It is particularly advantageous if at least one or more facets have a lens-shaped form, preferably the form of a Fresnel lens, so that the light can be focused and, in particular, more intense or higher-energy irradiation is made possible.

[0024] The diffuser element and / or optical element preferably has an elongated, rod-shaped, or cylindrical form, as described, such that the diffuser element and / or optical element defines a longitudinal axis. According to the invention, the lateral surface is therefore a lateral surface extending around the longitudinal axis. In particular, the normal vector of the lateral surface is thus perpendicular to the longitudinal axis.

[0025] It can be provided that the light-reflecting area of ​​the optical element and / or diffuser element, which is covered by the reflector layer as described, extends tangentially to the longitudinal axis over at least a certain angular range (e.g., over at least 90°, 180°, or 270°), and the light-transmitting area, which preferably remains free of the reflector layer as described, also extends tangentially to the longitudinal axis over at least a certain angular range (e.g., over at least 1°, 10°, or 20°). The light-transmitting area can thus be designed, for example, as a pie-shaped portion of the surface, but can, of course, also have more complex geometries as already described.

[0026] The reflector layer is applied concentrically to at least a portion of the lateral surface or to at least one facet. The reflector layer is preferably designed such that light from the diffuser element can be reflected back into the matrix of the diffuser element and / or that externally arriving light is reflected back outwards. This also means that the reflector layer can be unidirectional, allowing externally arriving light to be directed into the diffuser element; in other words, the reflector layer is transmissive to external light. The reflector layer and / or the mirror layer can therefore be designed as a dichroic mirror, for example, as a short-pass, long-pass, narrowband, or broadband mirror.

[0027] Preferably, the maximum reflectivity is greater than 95% and particularly preferably greater than 99%, especially when light is incident perpendicularly onto the reflector layer, and the reflectivity is specifically adjustable to a defined wavelength of the light used or in a predefinable range around a principal wavelength of the light.

[0028] In an advantageous embodiment, the reflectivity of the reflector layer at an angle of incidence greater than 45°, preferably greater than 60°, particularly preferably greater than 80°, relative to the perpendicular to the reflector layer, is greater than 50%, preferably 70%, and most preferably 90% of the reflectivity at perpendicular incidence, particularly in a region around a maximum reflectivity at perpendicular incidence. In other words, the reflectivity in a region, particularly in an angular range around the maximum reflectivity at perpendicular incidence, preferably the aforementioned angular range, can be greater than 50%, preferably greater than 70%, and preferably greater than 90%. Preferably, light in a predetermined wavelength range is guided through the diffuser element. However, different wavelengths have different reflectivities.Advantageously, a reflector layer is used which has a particularly high reflectivity for different wavelengths and / or for a large angular range, so that several maxima or a wavelength-dependent broad reflection maximum plateau occur with the light used and the corresponding wavelengths also exhibit high reflection, especially greater than 90%, even at oblique incidence of light.

[0029] The reflectivity can therefore be adjusted to the wavelengths and angles used. This allows a particularly high amount of light to be reflected. This is especially important because light absorption should be avoided. Since the lighting system can be operated with power levels up to 30 watts, typically between 10 and 20 watts, absorption can lead to significant heating of the diffuser element and / or the reflector layer. Such high absorption can damage the lighting system, for example, through overheating, or in worse cases, even cause personal injury. The lighting system should therefore be kept cool during operation by means of high reflection to prevent self-damage. In other words, self-heating of the optical element, or the diffuser element, should be avoided, preferably by reflecting the maximum amount of light.

[0030] It is also conceivable that the mirror layer, in particular the reflector layer, comprises or is formed from a metallic layer, preferably one or more metals from the group of noble metals or a metal from the group consisting of Mg, Al, Cu. An alloy of these materials is also conceivable. Due to their high reflectivity over a wide wavelength range, noble metals such as Au, Pt, Pd, or Ag are preferably used. Their processability for the production of the reflector layer is also comparatively simple. Due to the low oxidation potential of Au, it is inert, for example, to body fluids, and also exhibits low interaction with endogenous proteins, so the biocompatibility of Au is particularly good and therefore preferred.Overall, the reflector layer should meet the requirements, in particular the standardized requirements for biocompatibility and cytotoxicity, as required in medicine. As described, the lateral surface of the diffuser element or optical element is at least partially covered by a reflector layer, which preferably comprises a mirror layer. In a further development, the reflector layer can be multilayered and / or designed as a layer system. In this case, for example, the mirror layer of the reflector layer can consist of several layers. A multilayered reflector layer can also comprise one or more additional layers, which are present in addition to the mirror layer, in particular arranged below and / or above the mirror layer. The preferred reflectivity of the reflector layer, defined in more detail elsewhere, refers in the case of a multilayered orThe reflector layer, designed as a layered system, encompasses the entire reflector layer, i.e., including the mirror layer consisting of one or more layers, as well as any further layers consisting of one or more layers. Alternatively or additionally, it is of course also possible that further layers are provided below and / or above the reflector layer, which do not belong to the reflector layer itself.

[0031] According to the invention, the reflector layer is designed as a layer system comprising at least one mirror layer. The reflector layer may have at least one of the following features: Below the reflector layer, a base layer area consisting of a single layer or a sequence of layers is provided; between a diffuser base body and the mirror layer, at least one adhesive layer or adhesion promoter layer is provided; between the diffuser base body and the mirror layer, a layer area on the diffuser base body with chemically and / or physically modified adhesive properties is provided; the reflector layer has at least one passivation layer in an outwardly directed area, which at least partially covers the reflector layer. In other words, a cladding reflector of the lighting system with its at least one reflector layer can be designed as a layer system, and / or at least one adhesive layer or adhesion promoter layer can be provided between a diffuser base body, which is also referred to as a diffuser element, and the reflector layer, and / or a layer area on the diffuser base body with chemically and / or physically modified adhesive properties. According to the invention, the reflector layer has a mirror layer and, in addition to the mirror layer, a lower layer located below the mirror layer, and wherein the reflectivity of the reflector layer is greater than 90% for at least one wavelength range. As described, in a further training the reflector layer can be designed as a multi-layered or layered system, whereby it can be provided in particular that the reflector layer includes at least one further layer in addition to the mirror layer. Accordingly, the reflector layer can, in addition to the mirror layer, have a lower layer located below the mirror layer and / or an upper layer located above the mirror layer, wherein the lower layer consists in particular of one or more layers and wherein the upper layer consists in particular of one or more layers. A lower layer located below the mirror layer is preferably designed as an adhesive layer or adhesion promoter layer. A lower layer located below the mirror layer is preferably designed as a layer area on the diffuser base body with chemically and / or physically modified surface properties. A lower layer located below the mirror layer is preferably designed as a base layer region consisting of a single layer or a sequence of layers. A base layer region, e.g., a base layer region located below the mirror layer, which is in particular part of the reflector layer, and / or a base layer region provided below the reflector layer, can therefore comprise one or more layers applied to the optical element. Alternatively or additionally, it can be provided that the base layer region comprises a surface layer of the optical element with a modified surface property, in particular with an increased surface energy and / or an increased number of oxygen radicals, especially produced or producible by means of a chemical and / or physical process for modifying at least one surface property of the optical element.The base layer area, e.g. the base layer area located below the mirror layer, which is in particular part of the reflector layer, and / or the base layer area provided below the reflector layer, can in particular form the adhesive layer or the adhesion promoter layer.

[0032] It is therefore possible for the reflector layer or mirror layer to be arranged directly on the diffuser element, i.e., without an adhesive layer. The passivation layer may, but does not have to, be arranged on the reflector layer and / or the mirror layer. It is therefore also possible to design the diffuser element or the reflector layer with or without an adhesive layer and / or passivation layer. The adhesive layer, or the layer area with modified adhesive properties, ensures improved adhesion of the reflector layer to the optical element, the diffuser element, or the diffuser base body.This is particularly advantageous with regard to the corrosion resistance of the reflector layer, especially if the illumination system is used multiple times and the reflector layer is expected to withstand rigorous cleaning and sterilization processes involving corrosive acids and / or bases. Improved adhesion is also beneficial with regard to abrasion resistance, as friction can occur, for example, when the illumination system is moved within a catheter, and the reflector layer needs to adhere reliably to the diffuser base. It is also conceivable that the adhesive layer could be designed in such a way that it contributes positively to reflection.In other words, the material, surface, and / or crystal orientation of the adhesive layer are selected relative to the properties of the optical element or diffuser element such that at least a portion of the light or predetermined wavelengths are reflected. It is therefore worth noting that a preferred reflectivity of a reflector layer, which, in addition to the mirror layer, includes one or more further layers, such as a base layer and / or a passivation layer, applies to the entire reflector layer. In particular, layers applied below the mirror layer on the optical element and / or layers applied above the mirror layer can contribute to the reflectivity of the reflector layer. This also applies in particular to a surface layer of the optical element located below the mirror layer, which, for example,It can be produced using chemical and / or physical processes. These processes alter the material of the optical element within a surface layer, which can then form part of the reflector layer.

[0033] It may also be provided that the layer system has at least one additional passivation layer in the outer area, which completely covers the reflector layer. The passivation layer offers additional protection, for example against acids or other potentially corrosive media such as gases or liquids. Furthermore, the passivation layer can improve the biocompatibility of the reflector layer with substances of the biological body or material in which the lighting system is to be used, thus also protecting a patient undergoing treatment.

[0034] It is also stipulated that the lighting system must have at least one of the following features: The lower layer (43.1), in particular the adhesion layer or adhesion promoter layer or the base layer region, is designed as a dielectric layer, wherein the dielectric layer preferably comprises oxides, nitrides or oxynitrides of at least one element of the group consisting of Si, Al, Ti, Zr, Hf, Y, Zn; the upper layer (43.2), in particular the passivation layer (43.3), is designed as a dielectric layer, wherein the dielectric layer preferably comprises oxides, nitrides or oxynitrides of at least one element of the group consisting of Si, Al, Ti, Zr, Hf, Y, Zn. Such materials are particularly suitable as adhesion promoters, especially for layers of pure metals, for example on glass. Furthermore, metal oxides and metal nitrites are highly corrosion-resistant to chemical and / or mechanical stresses, such as abrasion. In particular, oxides of titanium and zirconium exhibit low interaction with body fluids, resulting in high biocompatibility. Therefore, such substances are also particularly suitable as passivation layers.

[0035] In an advantageous embodiment, the mirror layer or reflector layer is designed as a dielectric multilayer system comprising a sequence of low- and high-refractive-index metal oxides and / or nitrides. Such layer systems are particularly optimal and highly adjustable with regard to their reflection properties, allowing the design, or layer system, preferably the illumination system with the reflector layer, to be tailored to specific applications, and in particular, the wavelength range to be reflected can be precisely adjusted.

[0036] In a further embodiment, the mirror layer or the reflector layer can also be designed as a layer with scattering centers and can also be combined with reflector layers made of metals and / or dielectric layers, wherein the optionally additional reflector layers made of metals and / or dielectric layers at least partially enclose the layer with the scattering centers. In particular, scattering elements in a certain concentration or in a certain layer thickness can produce a reflective effect in a preferred direction. In principle, the reflective effect increases with increasing concentration of scattering centers and with the thickness of this layer with scattering centers. Examples of this are layers that contain white pigments or have embedded defects at which the incident light is scattered.Additional metallic and / or dielectric reflector layers can completely prevent light from passing through to the outside.

[0037] It is also advantageous if the reflector layer is designed as a system of three, four, or more layers. This allows for better coordination of individual layers and, in particular, very precise adjustment of the wavelengths to be reflected. This also advantageously allows for adjustment of the degree of reflectivity, enabling particularly high reflectivity of the light used. To further increase reflectivity, the mirror layer can also be embedded in a multilayer system, especially a dielectric system.

[0038] It is also conceivable that the layer thicknesses are defined according to at least one of the following characteristics: The thickness of the adhesive layer is greater than 5 nm, preferably greater than 30 nm, and / or less than 3000 nm, preferably less than 300 nm, preferably less than 150 nm; the thickness of the mirror layer is greater than 10 nm, preferably greater than 20 nm, preferably greater than 50 nm and / or less than 5000 nm, preferably less than 200 nm, preferably less than 100 nm; the thickness of the passivation layer is greater than 5 nm, preferably greater than 100 nm, preferably greater than 150 nm and / or less than 5000 nm, preferably less than 500 nm, preferably less than 250 nm. The adhesive layer is designed with a thin layer thickness such that it minimally affects the reflectivity of the reflector layer. Accordingly, the thickness of the mirror layer is determined by the specified values ​​to minimize light transmission while simultaneously minimizing the overall material requirement. The layer thickness of the mirror layer and / or the reflector layer is, for example, adjusted so that wavelengths above 0.35 µm, preferably above 0.4 µm, preferably above 0.8 µm, and / or below 2.5 µm, preferably below 1.6 µm, preferably below 1.2 µm, are reflectable. The layer thickness of the mirror layer and / or the The reflector layer is specifically tailored to a particular application wavelength. Depending on the application wavelength, the reflectivity can therefore be adjusted. If the application wavelength is, for example, 2 µm, then the reflectivity is optimized, for example, to a wavelength range between 1.9 µm and 2.1 µm or narrower, for example, between 670 µm and 710 µm at 690 nm. In other words, the reflectivity of the mirror layer and / or the reflector layer is adjusted to a wavelength that deviates from the application wavelength by at most 100 nm, preferably 50 nm, preferably 20 nm. The thickness of the passivation layer is selected to ensure corrosion resistance.

[0039] Ideally, the abrasion resistance and adhesion of the reflector layer, as previously described in various designs, should be resistant to at least standardized abrasive and adhesion tests. Such tests provide excellent verification of mechanical and physical corrosion resistance. Furthermore, they ensure that the lighting system is suitable for use in its intended environment, as strict regulations apply in the medical field.

[0040] Good adhesion, or physical resistance to mechanical stress, can be verified, for example, by a so-called tape test. In this test, a strip of adhesive is applied to the coated optical element or reflector layer and then peeled off at a defined angle. If no coating remains on the adhesive strip after peeling and no delamination is visible on the coating, the test is considered passed. It is particularly important to ensure that any passivation layer present is also resistant to the aforementioned mechanical stress.

[0041] A mechanical abrasion resistance test is the so-called eraser test or rubber test. In this test, an eraser is repeatedly moved back and forth across the layer being tested while applying a specific force. The layer is considered abrasion-resistant if no damage can be detected on the layer after this test cycle.

[0042] The passivation layer of the reflector layer can also be designed as a barrier layer. Accordingly, the passivation layer can be designed to inhibit or block the diffusion of polymer components, such as acids and / or oxygen, and especially ions from acidic or alkaline solutions, into the reflector layer, particularly at or into the mirror layer. The passivation layer can therefore delay or prevent the permeation of, for example, acids, oxygen, or other components of the air into the reflector layer.

[0043] Alkaline cleaners or disinfectants (e.g., NEODISHER with a pH of approximately 11) can be used, particularly in the reprocessing of medical products. Sterilization methods using ethylene oxide gas are also known, especially for disposable items. Here, too, chemical resistance to this gas must be ensured. Furthermore, good hydrolytic resistance is essential for autoclaving processes (typically at 135 °C / 3 bar).

[0044] Furthermore, a rinsing solution containing sodium hypochlorite (NaClO), a bleaching agent, or a disinfectant may be used, whereby the passivation layer, in particular, should be at least chemically resistant to such substances. This applies especially to applications in the medical dental field.

[0045] Preferably, the passivation layer or the reflector layer also has a hardness of, for example, at least 800 HV (Vickers hardness), preferably at least 1200 HV, and particularly preferably at least 2000 HV, according to the usual or standardized test methods for determining the hardness of a layer. The passivation layer can thus also serve as a mechanical protective layer for the mirror layer or the reflector layer, especially for a metallic mirror layer. In particular, hard materials made of, for example, carbides or nitrides provide protection due to their increased hardness, such as AlN₂: HV up to approximately 2000, Si₃N₄: HV up to approximately 2500.

[0046] It is further provided that the reflector layer is arranged at the distal end of the diffuser element and / or at least partially encases the diffuser element. It is understood that a reflector layer applied to the distal end of the diffuser element may also have an adhesive layer and / or passivation layer. The reflector layer can also be understood as a reflector surface, wherein the reflector surface is formed as sputtered or vapor-deposited dielectric reflective layers on the distal end of the diffuser base body, which consist of several layers and whose reflectivity is tuned to the wavelength of the light used, preferably with a maximum reflectivity at this wavelength.Ideally, the reflector surface, in the form of a specularly reflecting surface (e.g., a metallic mirror surface with a metallic coating, particularly comprising Al, Ag, or Au) or a diffusely reflecting surface (e.g., comprising a white coating), reflects the light passing through the diffuser body back into it. This allows the usual exponential decrease in the intensity of the laterally emitted light along the diffuser body to be at least partially compensated or corrected. The amount of light available at a constant scattering rate is thus at least sectionally adjustable, so that the lateral emission can be homogenized.

[0047] Furthermore, sputtered or vapor-deposited dielectric reflective layers on the distal end of the diffuser body have proven particularly advantageous. These layers can consist of multiple layers and their reflectivity can be tuned to the wavelength of the light used, meaning they can exhibit a maximum reflectivity at the selected wavelength. This allows for ideal back-reflection of the light coupled in during operation, or at least its specific wavelength, while simultaneously preventing hotspots. Alternatively, the reflector can be constructed from a broadband, highly reflective silver layer with back-side passivation. These are particularly robust and can suppress disruptive reflections that can lead to local intensity peaks and hotspots.This allows for the creation of a very broadband reflector that exhibits excellent reflection properties in both the visible (VIS) and IR / MIR spectral ranges, for example, between 1 µm and 2.5 µm wavelengths. A passivation layer on the back prevents oxidation of the silver layer.

[0048] If the reflector surface is concave or convex, it can be achieved that reflected rays are at least partially reflected back with an almost parallel course to the longitudinal axis and / or at a steeper angle to the longitudinal axis and are thus scattered more frequently at the scattering elements, so that the coupling efficiency of the lateral radiation towards the distal end of the diffuser element is increased, resulting in a more homogeneous distribution of the radiation intensity.

[0049] In an advantageous embodiment, the diffuser element comprises scattering elements that are enclosed in the matrix of the diffuser element, or the matrix of the diffuser element is encased in a material containing scattering elements. Scattering elements ensure that the light coupled into the diffuser element is scattered or deflected so that it can exit the diffuser element laterally. At least one scattering element is arranged along the entire longitudinal axis of the diffuser body with a uniform cross-section, essentially parallel to this axis or, in the case of tapered diffuser bodies, at an angle to the longitudinal axis. The scattering element can advantageously also be tubular and, in particular, arranged coaxially to the longitudinal axis.A plurality of scattering elements can be arranged in a specific, predefinable geometric configuration around the longitudinal axis of the diffuser base body, preferably in a regular structure around this axis, and particularly preferably circularly. A plurality of scattering elements arranged at an angle thus preferably converge at a vanishing point outside the diffuser base body.

[0050] In a preferred embodiment, the scattering elements are arranged radially and uniformly around the longitudinal axis of the diffuser body. A core zone around the longitudinal axis contains no or a significantly reduced number of scattering elements per unit area compared to the number of scattering elements per unit area outside the core zone, thus placing the scattering elements predominantly outside this core zone in the matrix. This ensures that the coupled light, which is typically coupled with a low NA (< 0.3, usually around 0.2), is not immediately scattered by the scattering elements. Furthermore, the nearly scattering-element-free core zone allows sufficient light to be guided without scattering to the distal end of the diffuser body.This allows the intensity to be reduced near the coupling point (proximal end of the diffuser body) and the intensity to be increased near the distal end of the diffuser body.

[0051] It is also conceivable that the diffuser element is at least partially or sectionally structured in its volume and / or on its surface, or that the diffuser element has a colored or colorless, in particular transparent, coating, preferably made of colored glass or colored plastic. A structure on the surface of the diffuser element allows for improved adhesion of the reflector layer and / or improved scattering properties. An example of a coating or coating that additionally supports a Lambertian radiation pattern and, in particular, reduces forward radiation in the direction of light coupling, is a boron nitride coating. Other coatings of this type can consist, for example, of titanium oxide, calcium carbonate, or zirconium oxide. The additional coating can, for example, be designed as a clear glass tube containing scattering elements in its glass matrix.However, a colorless or colored coating is also conceivable.

[0052] One embodiment therefore provides that the diffuser element with the reflector layer is at least partially or section by section enclosed by a transparent or translucent, colorless or colored shell. The shell typically has a diameter that corresponds to 1.1 to 1.5 times the diameter of the diffuser element. Preferably, the shell is formed from a rigid tube section made of glass or metal and / or from a flexible tube, wherein the tube section and / or the tube may preferably contain further scattering centers, and the shell is at least section by section made of one or more thin-walled shrink tubes.

[0053] A particularly preferred embodiment of the diffuser element proposes that the diffuser base body be provided distally to the reflector surface described above with a transparent and / or translucent, colored or colorless shell that at least partially or section by encloses it. This provides mechanical and / or chemical protection. Furthermore, by appropriately selecting the materials, especially if they contain scattering centers, the emission characteristics can be further optimized with regard to the homogeneity of the intensity of the lateral emission. This can, for example, promote Lambertian emission.

[0054] In a preferred embodiment, the casing is at least partially reinforced with one or more thin-walled heat-shrink tubes. These can, firstly, provide additional diffuse scattering, thus supporting Lambertian radiation. Secondly, they can provide mechanical protection and, for example, prevent potential chipping should the diffuser be damaged. A thin-walled heat-shrink tube made of white PET with a wall thickness of approximately 5 to 15 µm has proven suitable for this purpose. To suppress reflections, a thin-walled, black or colored heat-shrink tube can also be partially incorporated. The color can be selected to ensure particularly good absorption of the application wavelength. Such heat-shrink tubes are also biocompatible.In this way, damage to people in the vicinity or direct contact with the lighting system can be avoided. However, it is also possible for the casing to be designed as a sizing layer, preferably containing polyamide (PA), polyimide (PL), or polymethyl methacrylate (PMMA), or wax, wax-like components, or alkylsilane, or to be made of at least one of these materials.

[0055] The diffuser body can comprise or consist of a matrix of transparent plastic, particularly for improved processing, glass, quartz glass, or transparent glass-ceramic, wherein the scattering elements are arranged in a A plastic matrix comprises or consists of a porous, pigmented, or colored plastic; a glass matrix comprises or consists of pores, particles, glass or glass-ceramics containing porous, pigmented, colored, or inhomogeneous elements, or glass-ceramic elements and the crystallites contained therein; a quartz matrix comprises or consists of pores, porous quartz glass, or ceramic or polycrystalline particles; a transparent glass-ceramic matrix comprises or consists of pores, particles, glass or glass-ceramics containing porous, pigmented, colored, or inhomogeneous elements, or glass-ceramic elements and the crystallites contained therein, or a combination of the respective scattering elements. include.

[0056] The inhomogeneities of the glass or glass-ceramic that constitute the scattering elements in glass or glass-ceramic matrix solutions include phase separation, segregation, and / or particulate inclusion, nuclei, and / or crystallites. The scattering effect can be specifically adjusted by means of a temperature-time process. The concentrations of the scattering elements should be in the scattering range of 10 ppm to 1000 ppm, and preferably from 20 ppm to 100 ppm. Here, the concentration value in ppm refers to the proportion of scattering particles relative to the mass fractions of the components of the respective material, in particular the plastic, the glass matrix, or the quartz matrix in which the scattering particles are embedded.The scattering elements formed, which mean, for example, the pores, particles, porous or pigmented or, for example, white-colored or inhomogeneous glass or glass-ceramic elements and the crystallites contained therein, preferably have a diameter of 10 nm to 1000 nm, particularly preferably of 100 nm to 800 nm.

[0057] It is also advantageous if the diffuser element is made of borosilicate, phosphate crown glass, lead silicate glass, tin silicate glass, or alkali zinc glass, and / or if the scattering elements are made of clear glass rods, which are enclosed, in particular, by a sheathing tube, preferably made of borosilicate glass. This has the advantage that the diffuser base body as a whole is at least partially or sectionally visible in the X-ray image, and thus the position of the diffuser in a patient's body can be determined. With regard to application wavelengths from 0.8 µm to approximately 2.2 µm, for example, for the aforementioned EVLT applications, special IR-transparent glasses, such as phosphate crown glass or lead silicate glass, can also be used.

[0058] A quartz-based approach is particularly suitable for applications in the UV and / or IR range up to approximately 2.5 µm wavelength, provided the quartz glass has a very low number of OH groups. A further advantage is the extremely high thermal resistance and very low intrinsic absorption of quartz, which allows for higher laser powers up to 50 W in this application. In addition to diffusers made of porous quartz glass, diffusers made of or containing ceramic pigments, such as titanium dioxide, zirconium oxide, or aluminum oxide, can also be used. Quartz-based diffuser substrates are particularly well suited for splicing onto optical fibers made of quartz fibers, which consist of a core and a cladding layer with slightly different refractive indices. The cladding can also be made of organic materials, such as fluoropolymers, PMMA, or polyimide.

[0059] Glass-ceramic-based approaches for the diffuser substrate and / or scattering elements can be formed from a transparent aluminosilicate-high quartz solid solution glass ceramic. This material is extremely resistant to thermal shock and possesses high spectral transmission down to approximately 2.5 µm. For example, a keatite glass ceramic, which can be produced from the high quartz solid solution glass ceramic through a suitable tempering process, is suitable as a scattering element. Cordierite glass ceramics or magnesium-aluminum silicate glass ceramics are also suitable as diffuser substrates and / or scattering elements.A particularly preferred diffuser base body with regard to its manufacturing process is obtained when the diffuser base body is formed from light guide rods made of borosilicate glass rods, tin silicate glass rods, or alkali zinc silicate glass rods and / or the scattering elements are formed from white glass rods, which are preferably enclosed with a sheathing tube made of borosilicate glass, tin silicate glass, or alkali zinc silicate glass and form the preform.

[0060] In a further development of the invention, both the diffuser base and the casing tube can be made of the same type of glass. The refractive index of the casing tube is preferably not greater than that of the glass of the matrix; more preferably, both refractive indices are the same. This facilitates the extraction of the light scattered in the diffuser. This enables cost-effective processes for manufacturing diffusers that allow them to be produced in virtually any length with homogeneous emission intensity.

[0061] The invention also relates to a method for manufacturing a lighting system for a medical therapy and / or diagnostic system, in particular for use on living tissue, comprising at least one light source, an optical fiber which can be connected to or associated with the light source at a proximal end, and an optical element, which is preferably designed as a diffuser element and is arranged at a distal end of the optical fiber. The light from the optical fiber can be coupled into the optical element, and the method comprises the following steps: Providing a diffuser element with a lateral surface, at least partially covering the lateral surface with a light-reflecting reflector layer, preferably a mirror layer, such that the optical element has a light-reflecting area covered by the reflector layer and a light-transmitting area unaffected by the reflector layer, so that the light emitted by the optical element is at least partially reflectable, and light can be selectively emitted from the light-transmitting area. The reflectivity of the reflector layer is greater than 90% for at least one wavelength range. Ideally, the illumination system covered with the reflector layer exhibits at least one, and preferably several, of the properties or features described above in order to generate the corresponding advantages. The reflector layer preferably extends in the axial direction, particularly along the longitudinal axis of the optical element. The surface area can also be understood as the cladding layer or base layer region, the wall thickness of which is preferably in the range of 1 to 100 µm.

[0062] It is also advantageous if the surface is pretreated or activated by creating a base layer with at least one modified surface property, in particular by means of chemical or physical processes to modify the surface properties of the surface, so that the surface can also be understood as a surface layer or base layer, the wall thickness of which is preferably in the range of 1 to 100 µm. The reflector layer can therefore be applied directly to the surface, which is preferably not pretreated, or to the surface layer or the base layer.

[0063] The base layer can comprise a surface layer of the cladding with at least one modified surface property, in particular an increased surface energy and / or an increased number of oxygen radicals, which ensures good adhesion of subsequent coatings, for example, the adhesive layer and / or the reflector layer. Such a surface sublayer of the cladding can be produced, for example, by chemical or physical processes to modify the surface properties of the cladding or cladding layer, in particular plasma treatment (e.g., low-pressure plasma or atmospheric plasma), UV treatment, arc discharge (corona), and / or by chemical treatment, e.g., using alkaline cleaners in an ultrasonic bath, or a combination of such processes. Plasmas can also be used to remove greases, oils, or similar residues and additionally activate oxygen radicals.In other words, the base layer region, or a bottom layer of the base layer region, can be formed by a radial portion of the lateral surface encompassing the outer surface. The base layer region can therefore also consist of a single layer, for example, where this single layer is formed by chemical or physical processes based on the surface properties of the optical element's lateral surface.

[0064] The base layer area can also consist of a sequence of layers, whereby, for example, the lowest layer of the base layer area is formed by chemical or physical processes based on the surface properties of the optical element's lateral surface, and further layers are applied to this lowest layer.

[0065] It is also conceivable that the reflector layer is applied to the surface of the casing, in particular by means of cathode sputtering, high-frequency sputtering, reactive sputtering, magnetron sputtering, evaporation, especially ion beam evaporation, and / or thermal evaporation. In addition to the methods mentioned, the production of at least one layer, preferably several layers of the reflector layer, can also involve other coating processes, for example, vacuum processes (e.g., ion beam or thermal evaporation), chemical vapor deposition (CVD, e.g., PECVD, especially PICVD). Furthermore, liquid-phase processes such as dip coating or spray coating are possible as additional coating methods for applying one or more layers of the reflector layer. Additional functionalities, such as friction reduction, can also be incorporated in these processes.

[0066] The substances intended for coating, in particular oxides, nitrites, or oxynitrides of Si, Al, Ti, Zr, Hf, Y, Zn, can be applied, for example, by means of a sputtering process from a so-called sputtering target. These materials can be in the form of metallic or semi-ceramic targets. The purity of the targets is typically specified as 99% or higher. Lower purities are also possible, in which case greater layer thicknesses may be required.

[0067] It may be provided that an adhesive layer or an adhesion promoter layer is applied to the surface of the casing and / or a passivation layer is applied to the reflector layer, preferably by means of cathode sputtering, high-frequency sputtering, reactive sputtering, magnetron sputtering, vapor deposition, in particular ion beam vapor deposition, and / or thermal vapor deposition. The base layer region may be designed as an adhesion promoter layer. Accordingly, it may be provided that there is greater adhesion between the base layer region and the reflector layer applied to it than would exist between a treated or untreated surface of the casing and a reflector layer applied to it.In other words, increased adhesion can exist between the reflector layer and, in particular, the underlying topmost layer of the base layer area, which may be formed as a layer with increased surface energy and / or an increased number of oxygen radicals, or as an adhesive layer applied to the surface by coating.

[0068] It is also possible for the base layer region to consist of multiple adhesive layers, wherein at least one or each adhesive layer applied above the lowest adhesive layer exhibits higher adhesion to the layer below it than it would to the layer located beneath the layer below that. In other words, the surface or optical element can be coated with a single or multiple adhesive layers forming the base layer region. For at least one adhesive layer, the use of at least one material from the group consisting of Si, Al, Ti, Zr, Hf, Y, or Zn is provided, preferably as an oxide, nitrite, or oxynitride. However, other substances such as boride, carbide, or carbonitride can also be used. Preferred layer systems include, for example, TiO₂.

[0069] The base layer, or the adhesive layer and / or the passivation layer, can have an amorphous structure, but also a crystalline or polycrystalline structure, especially if these are applied by coating. Typical examples of amorphous coatings are SiO₂, Si₃N₄, Al₂O₃, AlSiOx, or BN; typical examples of crystalline coatings are anatases or rutile TiO₂, γ-Al₂O₃, or crystalline Al₃. In particular, mixed phases of amorphous and crystalline structures can also form.

[0070] Another preferred lighting system provides a mirror layer or reflector layer that exhibits different reflection and transmission characteristics for different wavelengths, particularly for closely spaced wavelengths λ₁ and λ₂, where the wavelength difference Δλ = |λ₁ - λ₂| can be < 200 nm, preferably < 100 nm. This allows for the realization of a lighting system with switchable emission characteristics, where these different wavelengths λ₁ and λ₂ can be adjusted via the light source. The basic idea is to design the reflector or mirror layer such that at the first wavelength λ₁, the lateral reflection layer applied to the surface is largely transparent and can be penetrated by light. This achieves the emission characteristics of an omnidirectional diffuser.When switching to the second wavelength λ₂, the lateral reflector layer now acts as a mirror, resulting in a laterally focused beam within a sector. For the two different wavelengths λ₁ and λ₂, the mirror layer or the reflector layer exhibits a different reflectivity and / or transmission of preferably at least 10%, particularly preferably at least 30%. This allows for a significant change in the beam pattern when switching wavelengths, from predominantly omnidirectional to focused beam within a sector. The lateral reflector layer is therefore designed to be narrowband with respect to the wavelength. It would be advantageous if the distal reflector exhibited high reflectivity for both λ₁ and λ₂. This is particularly beneficial in medical applications of the lighting system.Examples of wavelengths λ₁ and λ₂ that are so close together would be 980 nm and 1064 nm, which are often used in medical technology applications. Such behavior can be achieved particularly well with the dielectric layer systems described above. It should be noted that λ₁ and λ₂ can, of course, be further apart (> 200 nm), but in medical technology applications, this can lead to very different absorption properties of the tissue at such different wavelengths. Therefore, the wavelengths cannot be arbitrary or arbitrarily far apart.

[0071] In addition, another application can be mentioned in which different wavelengths, which can be switchable in particular, allow for different penetration depths of the radiation, which can be an advantage especially with regard to the penetration behavior in tissue from a surgical point of view.

[0072] Coating the optical element with the reflector layer first involves creating a base layer area consisting of a single adhesive layer and / or activation of the lateral surface or a sequence of adhesive layers, and then applying (to the base layer area) a mirror layer consisting of a single layer or a sequence of, in particular alternating high and low refractive index layers, or a layer system of high and low refractive index layers. Activation of the lateral surface can be understood as the removal of residues and / or the creation of a modified surface property, in particular an increased surface energy and / or an increased number of oxygen radicals.

[0073] Coating or activation preferably takes place at temperatures below 50°C. This relatively low temperature has the particular advantage that optical elements can be coated with a polymer layer. Processing in a vacuum, and especially without vacuum breakage, is also preferred. For example, the base layer can first be produced in a vacuum, followed by the application of the mirror layer in the same vacuum. Finally, the passivation layer can then be applied in the same vacuum.

[0074] A preferred application of the lighting system, as previously described in its various configurations, is for photodynamic therapy (PDT) or photoimmunotherapy (PIT), for example, for tumor therapy; for endovenous laser therapy (EVLT), for example, for the treatment of varicose veins; for laser-induced interstitial thermotherapy (LITT); or for applications in dentistry, ophthalmology, and dermatology, as described at the beginning. In dentistry, applications for wound or periodontal treatment are particularly noteworthy. Furthermore, there are applications in brain research, where light can be used to stimulate specific brain regions and thus treat disease symptoms.

[0075] Another application of the illumination system, as previously described in its various configurations, involves its use in photodynamic therapy (PDT) or photoimmunotherapy (PIT) for tumor treatment. In this system, at least one light guide with a diffuser element captures light emitted from other diffuser elements and transmits it to a detector for spectroscopic analysis. In addition to the various light-emitting diffuser light guides, light-receiving diffuser light guides are also applied to the patient. The response to the PDT treatment can then be determined based on the spectral differences between the emitted and received light (see Finlay et al., Proc. SPIE Int. Soc. Opt. Eng. 2014, June 14; 5315: Page 132-142). Furthermore, such systems can also be used for dosimetry during, for example, PDT or PIT treatments.

[0076] Furthermore, applications in the industrial sector are also advantageous, for example as a component of a device for targeted illumination of cavities, such as for inspecting hard-to-reach areas, for instance on or inside a machine, where homogeneous illumination is particularly important, for illuminating workpieces with small openings, or for spectroscopic applications, or in biochemistry, where light stimulates biochemical in-vitro reactions, i.e., for irradiating samples in in-vitro diagnostics. Applications can also be seen in the targeted curing of resins or adhesives, or materials containing them, as well as where homogeneous illumination is necessary or joining points are difficult to access.

[0077] The invention is explained in more detail below with reference to the enclosed figures. In the figures, identical reference numerals denote identical or corresponding elements. They show: Fig. 1 Schematic representation of an illumination system with a light guide and a diffuser element emitting sectionally in one direction in a PDT or PIT application; Fig. 2 Schematic representation of a diffuser element; Fig. 3 Comparison of differently coated surfaces after an abrasion test; Fig. 4 Schematic representation of an embodiment of a reflector layer; Fig. 5 Schematic representation of an embodiment with a reflector layer, an adhesive layer, and a passivation layer; Fig. 6 Schematic representation of an embodiment with a dielectric reflector layer, an adhesive layer, and a passivation layer; Fig. 7 Reflectivity curve as a function of wavelength; Fig. 8 Reflectivity curve as a function of wavelength for different angles of incidence; Fig.9. Graph of reflectivity as a function of wavelength and angle of incidence for an interference reflector.

[0078] In the following description of the detailed embodiments, identical reference numerals in the accompanying figures denote identical or equivalently functioning components. For better understanding, the following definitions are provided. For the purposes of this disclosure, the term "illumination system" includes lighting devices, and in particular lighting devices suitable for use in medical technology and, especially insofar as they are intended to come into contact with living tissue, at least partially disinfectable and / or sterilizable. The designation "for a medical therapy and / or diagnostic system" includes, without limitation, in particular the suitability, use, or application of the illumination system disclosed herein itself as a medical therapy and / or diagnostic system.

[0079] Fig. 1Figure 1 schematically shows the structure of an illumination system 1 according to the invention. A medical PDT application is shown as an example. In the example shown, the illumination system 1 comprises an LED or laser light source 10, which emits light in a specific spectral range during operation. For PDT or PIT applications, as described above, lasers are used that emit wavelengths tuned to a previously administered biochemically modified dye (photosensitizer), typically in the visible range, for example in the green spectral range at 532 nm or in the red spectral range at, for example, 690 nm.

[0080] An optical fiber 30 is connected to the laser light source 10 at its proximal end 30.1 by a connector 20 or other connecting element. The proximal end 30.1 is the end of the optical fiber 30 into which light is coupled. At its distal end 30.2, the optical fiber 30 has an optical element in the form of a diffuser element 40, which is placed in or near a tumor tissue 60 that has formed within and is adjacent to healthy tissue 50. The distal end 30.2 is the other end of the optical fiber 30, which is usually located further away from the proximal end 30.1 of the optical fiber 30 and from which light is emitted.

[0081] The laser radiation enters the diffuser element 40 via a light coupling 31 through the light guide 30 at the diffuser element 40. The diffuser element 40 is formed, for example, from a diffuser base body 41. The light is emitted laterally along the length L of the diffuser element, which is defined by the longitudinal axis L, or coupled out as light output 42 in the transparent area. It is important to achieve the most homogeneous emission possible along the length of the diffuser element 40. In particular, intensity peaks must be avoided. In the example shown, the diffuser element 40 emits light in only one direction, i.e., sectionally into the tumor tissue 60. Ideally, a photoinduced biochemical reaction, as described above, leads to the death of the tumor tissue 60 after treatment.

[0082] Without limiting ourselves to the example shown here, quartz fibers are generally used as optical fibers 30, with the connectors 20 typically being designed as coaxial connectors, so-called SMA connectors, in which the fibers are preferably glued into the connector 20. Connectors 20 with nickel silver sleeves can also be advantageous with regard to thermal resistance, in which the optical fiber 30 is positively inserted / crimped into the nickel silver sleeve, particularly by plastic deformation. Furthermore, for higher laser powers, connectors 20 can also be used in which the fiber end of the optical fiber 30 is protected by a conical prism, which can be advantageous in case of misalignment.

[0083] Fig. 2Figure 1 schematically illustrates the structure of the diffuser element 40. The diffuser element 40 consists of a diffuser base body 41, which is preferably spliced ​​or glued to the optical fiber 30. In the applications described above, the optical fiber 30 typically consists of a quartz fiber with a core. The core has a refractive index n1 and a core diameter of usually between 100 µm and 1000 µm, preferably between 200 µm and 600 µm, as well as a cladding or cladding surface with a refractive index n2, where n1 > n2. The numerical aperture NA typically achievable with this is approximately 0.22 or less, for example, 0.1. Higher NA values, up to 0.4 or 0.6, can also be achieved through special doping. The light coupling 31 from the light guide 30 takes place via a corresponding coupling surface of the diffuser base body 41.

[0084] Furthermore, in a spliced ​​connection, it can be advantageous if the connection between the diffuser base body 41 and the optical fiber 30 is implemented in two stages. First, only a short section (typically a few tens of mm long, e.g., approximately 10 to 20 mm) of the optical fiber 30 is spliced ​​to the diffuser base body 41. This is then coated, and subsequently, the actual pigtail, consisting of the optical fiber 30 and the connector 20, is spliced ​​to the short section of the optical fiber 30. This is particularly advantageous because the reflector coating is not thermally damaged or its reflective properties unduly altered during the splicing process, which involves a locally high energy density induced by lasers and / or corona discharges. Additionally, the diffuser base body 41, with only the short section of the optical fiber 30 attached, can be more easily installed in the coating chamber during the coating process.This significantly reduces handling effort compared to handling with a complete pigtail.

[0085] The diffuser base body 41, or optical element, comprises, for example, a matrix of matrix elements with embedded scattering elements and / or a sheathing tube. The diffuser base body 41 can also consist of a glass whose scattering properties can be specifically adjusted by thermal treatment with defined temperature-time control. A glass-ceramic matrix is ​​also conceivable for the diffuser base body 41, in which the crystallite density and / or the size of the crystallites can likewise be specifically adjusted by targeted temperature-time treatment, thus also influencing the scattering properties. Plastic-based optical elements are also conceivable, in which a polymer optical fiber (POF) is attached as a light guide 30.

[0086] To prevent scattered light from the connection zone between light guide 30 and diffuser base body 41, but also as a mechanical stabilization of this connection zone, a sleeve made of plastic, glass, metal or ceramic material can be provided.

[0087] The diffuser element 40 has a reflector layer 43 and optionally also a reflector, or another reflector layer, at the distal end 44. This results in essentially three light extraction contributions 42: a lateral light extraction 42.2 at a predefinable beam angle 42.1, a rear light extraction 42.3 through the reflector layer, and a distal light extraction 42.4.

[0088] For a medical technology application where targeted irradiation of tissue is required, the proportion of backlight emission 42.3 should be as low as possible, which necessitates the highest possible reflectivity of the reflector layer 43. Furthermore, it may also be necessary to largely prevent distal light emission 42.4 at the distal end 44, which again requires the highest possible reflectivity of the reflector layer at the distal end 44. In addition, high reflectivity can increase back-reflection at the distal end 44 and / or the efficiency of lateral light emission 42.2. In both cases, reflectivity values ​​of over 90%, preferably over 95%, and most preferably over 99% are required. Moreover, the reflector layer must not exhibit high absorption to prevent excessive heating.

[0089] Corrosion resistance is also important, especially with regard to complex cleaning processes and mechanical stresses, for example, when the diffuser element 40 is moved several times within a catheter, resulting in friction. The applied layers of the reflector layer can therefore be subjected to cleaning processes (e.g., with ethanol) or even pass abrasive tests, such as the eraser test, the "Tesa test," or the taper test.

[0090] Figure 3Figure 1 shows a comparison following an eraser test: The image above depicts the reflector layer 43, designed as a dielectric multilayer system 45 in a 4-layer design. The image below shows, for comparison, the surface of a metallic Cr + Au reflector coating 46. It can be seen that a purely metallic reflector coating does not withstand the stresses sufficiently and that a dielectric multilayer system 45 can be better tailored with regard to mechanical strength.

[0091] The Figures 4 to 6 The figures show schematic, not to scale, typical embodiments of the reflector layer 43. Figure 4Figure 1 shows a simple layer structure for the cladding reflector 43, in which a metallic mirror layer 43.2 is deposited on the diffuser base body 41. The light to be reflected can strike the mirror layer 43.2, the adhesion promoter layer 43.1, or the reflector layer 43 at different angles of incidence 102 to the perpendicular 47.

[0092] Advantageously, the maximum reflectivity for light incident obliquely to the reflector surface is greater than 50%, preferably greater than 70%, and particularly preferably greater than 90%. For the purposes of this disclosure, obliquely incident light is understood to mean that the light strikes the reflector layer 43 at an angle between 0° and 90°, or preferably at an angle greater than 50°, and more preferably greater than 70°, to the perpendicular 47 of the reflector layer 43. Since the light is guided and scattered substantially along the diffuser element 41, a certain proportion of the light will strike the reflector layer 43 obliquely. It is therefore advantageous if this portion of the light is also reflected.

[0093] Metallic mirror coatings 43.2 can preferably consist of noble metals such as Au, Ag, Pd, or Pt, which exhibit high reflectivity in the visible range of light. Alloys of several metals or multilayer metal coatings are also conceivable. Such simply structured coatings can, as in Figure 3 depicted, but in some cases not practical with regard to mechanical abrasion, adhesion or chemical attack.

[0094] Figure 5This figure therefore shows a more complex, multilayer structure with an adhesive layer 43.1 or bonding agent layer directly on the diffuser substrate 41, the actual mirror layer 43.2, and an additional passivation layer 43.3. It should be noted that the conventional bonding agents for precious metals such as Cr or Ni lead to a reduction in reflection due to the light guidance via the fiber or the optical element. This is the case even with very small layer thicknesses of the adhesive layer 43.1, for example, 10 nm. Dielectric layers can be used as alternative adhesive layers 43.1 to avoid significantly reducing reflection. Oxides, nitrides, or oxynitrides of Si, Al, Si, Al, Ti, Zr, Hf, and optionally also Y and Zn can be used. The layer thicknesses of the precious metal layers designed as mirror layers 43.2 can range from 10 nm to 5000 nm, preferably in the range between 10 nm and 300 nm.The thickness of the adhesive layer 43.1 or adhesion promoter layer is typically a maximum of a few tens of nm, preferably in the range of 5 nm to 50 nm.

[0095] Another example of a possible mirror layer 43.2 is a non-noble metal layer with high reflectivity, such as Mg, Al, or Cu, embedded in an optical design in such a way as to increase reflectivity. In its simplest form, a three-layer design is fabricated from TiO₂ (Mg), SiO₂, and Mg, where the reflection can be increased by using a high-refractive-index first layer, a low-refractive-index second layer, and a highly reflective metal layer. Additional protection against corrosion is provided by a further layer, in particular a passivation layer 43.3, applied downstream of the metal layer. This additional barrier / passivation layer can contain oxides, nitrides, or oxynitrides of Si, AlSi, Al, Ti, Zr, Hf, and optionally also Y and Zn.At this position, the optical properties of the layer are not relevant, which is why sacrificial metal layers could also be used, which corrode instead of the functional metal layer. These could be, for example, Al, Cu, Cr, or Ni. But other metals are also conceivable.

[0096] By way of example and without limitation to the values ​​presented, the layer thicknesses of a functional 3-layer reflector layer 43 are shown in the following example 1, which lie in the following ranges: I. TiO₂ (as adhesive layer 43.1): Range: 30 nm to 5000 nm, preferably between 30 nm and 300 nm, typically 100–200 nm. II. SiO₂: Range: 40 nm to 5000 nm, preferably between 40 nm and 380 nm, typically 150–250 nm. III. Mg: Range: 20 nm to 2000 nm, preferably between 20 nm and 200 nm, typically 50–150 nm. IV. SiO₂: Range: 5 nm to 5000 nm, preferably between 5 nm and 500 nm, typically 100–250 nm.

[0097] The design shown allows the reflection in a wavelength range above 1000 nm to be increased to over 90%, preferably over 92%, or even more preferably over 95%, particularly when light is incident perpendicular to the reflector layer 43. Furthermore, the layer system is characterized by the fact that high reflections are maintained within an angular range of 0 to ±80°, measured from the perpendicular to the reflector layer 43, which is necessary for the intended application in the medical field, especially for tissue irradiation. For the purposes of this invention, high reflections are defined as reflections which, within a previously specified angular range around the maximum reflectivity at perpendicular incidence, are greater than 50%, preferably greater than 70%, and more preferably greater than 90%.

[0098] A key advantage of a Mg-based layer, as in Example 1, is its high reflectivity as a non-precious metal coating, similar to Cu or Al. A major advantage of this variant is its ease of manufacture. Since only a few layers are required, production in large-scale / inline systems is also possible. Furthermore, uniformity is not a critical requirement in this case. Additionally, TiO₂ and SiO₂ layers are well-managed as standard processes. Likewise, a Mg layer, as a metallic layer, is easy to produce. Another advantage over softer precious metal layers is its good adhesion and mechanical resistance. The applied layers can be subjected to cleaning processes (e.g., with ethanol) or even, as in [reference], are resistant to [further explanation]. Figure 3 Abrasive tests were shown.

[0099] In Figure 6 is exemplary and analogous to the Figures 4 and 5Another example is presented in the form of an interference-optical dielectric system. Here, the mirror layer 43.2 is composed of alternating high- and low-refractive-index layers, so that, according to Fresnel's laws, high reflections can be achieved from transparent dielectric layers. This is accomplished by adjusting the lambda-quarter layer thickness for a reference wavelength. Suitable materials for this approach include TiO₂, Ta₂O₅, Nb₂O₅, or ZrO₂ as high-refractive-index layers, or generally layers with a refractive index greater than 2.2. These materials can be further stabilized by doping, for example with Al, Si, Y, or Zn. SiO₂ or doped SiO₂ variants are particularly suitable as low-refractive-index layers. Oxides, nitrides, fluorides (e.g., MgF₂), or oxynitrides of other metals are also possible.SiO₂ with low N₂ doping is also conceivable and fulfills the requirement of a low refractive index, preferably below 1.5, very well. With such designs, for example a high-low refractive index layer system consisting of 11 layers, broadband and highly reflective reflector layers 43 or mirror layers 43.2 can be achieved, with layer thicknesses for TiO₂ being, for example, 120 nm to 130 nm and for SiO₂, for example, 210 nm to 220 nm, particularly for a wavelength range between 1000 nm and 1100 nm. Due to the broadband nature, various angles of incidence over a wide range at a defined reference wavelength (here, for example, 1064 nm) can also be reflected.

[0100] Figure 7Figure 100 shows the reflectivity 101, or the reflectance, as a function of wavelength 103 for a multilayer system of TiO₂ / SiO₂ / Mg / SiO₂ as described in Example 1. For such a system, the reflectance is particularly high at wavelengths around 600 nm, as well as in the wavelength range from approximately 900 nm to approximately 1100 nm, for example, exceeding 90%.

[0101] Figure 8 Another trend diagram 100 shows the reflectivity 101, or the degree of reflection, for the in Figure 7The layer system shown is a function of wavelength 103 and different angles of incidence 102. The first curve 100.1 shows a curve for a 0° angle of incidence from the perpendicular. The second curve 100.2 shows a curve for a 60° angle of incidence from the perpendicular, and the third curve 100.3 shows a curve for an 80° angle of incidence from the perpendicular. It can be seen that, for example, in a range from 1000 nm to 1100 nm, a nearly angle-independent reflectance of 95% can be achieved. In the example shown, such a layer system was optimized for an application wavelength of 1064 nm. By varying the individual layer thicknesses of the mirror layer 34.2, such a high, nearly angle-independent coating can be achieved for a wide range of wavelengths.

[0102] Figure 9Figure 100, in a further curve diagram, shows the reflectivity 101 for a particularly 11-layer high-low refractive index (HRI) layer design made of TiO₂ / SiO₂ in various profiles 100.1, 100.2, 100.3. Here, the reflectivity is normalized to 100% for the maximum value and varies for different angles of incidence 102. The first profile 100.1 represents the 0° angle of incidence 102, the second profile 100.2 represents the 60° angle of incidence 102, and the third profile 100.3 represents the 80° angle of incidence 102 relative to the perpendicular to the mirror layer 43.2. The center wavelength here is approximately 1040 nm to 1060 nm. Very highly reflective designs can be achieved with such layer variants, depending on the absorption or opacity of the layers used.Absorption depends on the materials used and the manufacturing process. Cloudiness can be caused by substrate cleanliness, defects in the coating process, plasma polymerization, cracking, or similar factors. Since a coating process must be highly reproducible and stable, PVD-based processes such as evaporation or sputtering, for example magnetron sputtering or ion beam sputtering, are preferably used to produce the reflector layer 43, the adhesive layer 43.1, and / or the passivation layer 43.3. The coating process can be represented, for example, by a magnetron sputtering process. For a 3- or 4-layer system, the process comprises the following steps: Cleaning of the substrate surface, or the cladding surface or the surface of the optical element via an ultrasonic cleaning process, thermal treatment of the cladding surface or the surface of the optical element in a vacuum to improve adhesion by dewatering the surface, reactive magnetron sputtering of the metallic target of the TiO2 and SiO2 layers or sputtering of the ceramic target in the case of TiO2 or metallic sputtering of Mg, defect-free sputtering by, for example, vertical system and substrate arrangement, or arrangement of the optical element. In a further step, or more specifically an additional process step, oxygen plasma pretreatment can be carried out under vacuum. This serves to improve adhesion by preconditioning the surface. However, plasma pretreatments, especially under atmospheric pressure, are also advantageous. In the case of metallic layers as a reflector layer, it is also conceivable that these are first applied to a pre-form of the diffuser blank and then the diffuser is drawn out in a drawing process. Reference symbol list

[0103] 1 Illumination system 10 Laser light source 20 Connector 30 Optical fiber 30.1 Proximal end of optical fiber 30.2 Distal end of optical fiber 31 Light coupling 40 Diffuser element 41 Diffuser base body 42 Light coupling in the translucent area 42.1 Beam angle 42.2 Lateral light coupling 42.3 Rear light coupling 42.4 Distal light coupling 43 Reflector layer (light-reflecting area) 43.1 Adhesive layer 43.2 Mirror layer 43.3 Passivation layer 44 Reflector distal end 45 Dielectric multilayer system 46 Metallic reflector coating 47 Perpendicular 50 Tissue 60 Tumor tissue 100 Progression diagram 100.1 1. Progression 100.2 2. Course 100.33. Course 101Reflectivity 102Angle of incidence 103Wavelength Longitudinal axis

Claims

1. A lighting system (1), in particular for a medical technology therapy and / or diagnosis system, comprising at least one light source (10), a light guide (30) which is connectable to the light source (10) at a proximal end thereof or assignable thereto, and an optical element, preferably in the form of a diffuser element (40) and arranged at a distal end of the light guide (30), so that light from the light guide (30) can be injected into the optical element, said optical element defining a longitudinal axis (L) and having a lateral surface surrounding the longitudinal axis and being covered by at least one reflector layer (43) at least in sections thereof, wherein the optical element (40) comprises a light-reflecting area covered by the reflector layer (43), and comprises a light-transmissive area which preferably remains free of the reflector layer (43), so that the light injected into the optical element can be reflected at least partially at the light-reflecting area and light can be emitted from the light-transmissive area; characterised in that the reflector layer (43) comprises a mirror layer (43.2) and, in addition to the mirror layer (43.2), comprises a lower layer (43.1) disposed below the mirror layer (43.2), and wherein the reflector layer (43) exhibits a reflectance (101) of more than 90 % for at least one wavelength range.

2. The lighting system (1) according to the preceding claim, characterised in that the light can be emitted transversely to the longitudinal axis (L) of the optical element and laterally over an active length of the optical element; and / or at least one area of the diffuser element (40) that is not covered by the reflector layer (43) extends along the longitudinal extension of the diffuser element (40) and this non-covered area is light-transmissive, so that light carried through the diffuser element (40) can be emitted in a strip-like pattern.

3. The lighting system (1) according to any one of the preceding claims, characterised in that maximum reflectance (101) is greater than 95 % and most preferably greater than 99 %, in particular for perpendicular incidence of light onto the reflector layer (43), and that the reflectance (101) is preferably selectively adjustable to a predefined wavelength (103) of the employed light or in a predetermined range around a main wavelength (103) of the light; and / or for a light incidence angle of greater than 45°, preferably greater than 60°, most preferably greater than 80° with respect to the perpendicular to the reflector layer (43), the reflector layer (43) exhibits a reflectance (101) of more than 50 %, preferably 70 %, most preferably 90 % of the reflectance at perpendicular incidence of light.

4. The lighting system (1) according to any one of the preceding claims, characterised in that the mirror layer (43.2) comprises or is made of a metallic layer which preferably contains one or more metals from the group of noble metals or a metal from the group consisting of Mg, Al, Cu.

5. The lighting system (1) according to any one of the preceding claims, characterised in that the reflector layer (43) comprises an upper layer (43.3) provided above the mirror layer (43.2), wherein said lower layer (43.1) in particular consists of one or more layers and wherein said upper layer (43.3) in particular consists of one or more layers; and wherein a lower layer (43.1) provided below the mirror layer (43.2) is preferably in the form of an adhesion layer or adhesion promoting layer; and / or wherein a lower layer (43.1) provided below the mirror layer (43.2) is preferably in the form of a layer zone on the diffuser base body (41) and has chemically and / or physically modified surface properties; and / or wherein a lower layer (43.1) provided below the mirror layer (43.2) is preferably in the form of a base layer zone consisting of a single layer or of a sequence of layers; wherein said base layer zone provided below the mirror layer (43.2) preferably comprises one or more layers applied on the optical element and / or comprises a near-surface layer of the optical element, which has a modified surface property, which in particular is produced or can be produced by a chemical and / or physical process for altering at least one surface property of the optical element.

6. The lighting system (1) according to the preceding claim, characterised in that the lighting system (1) exhibits at least one of the following features: - the lower layer (43.1), in particular the adhesion layer or adhesion promoting layer (43.1) or the base layer zone, is in the form of a dielectric layer, said dielectric layer preferably including oxides, nitrides, or oxynitrides of at least one element from the group consisting of Si, Al, Ti, Zr, Hf, Y, Zn; - the upper layer (43.3), in particular the passivation layer (43.3), is in the form of a dielectric layer, said dielectric layer preferably including oxides, nitrides, or oxynitrides of at least one element from the group consisting of Si, Al, Ti, Zr, Hf, Y, Zn.

7. The lighting system (1) according to any one of the preceding claims, characterised in that the mirror layer (43.2) or the reflector layer (43) is in the form of a dielectric multilayer system comprising in particular a sequence of low refractive index and high refractive index metal oxides and / or metal nitrites.

8. The lighting system (1) according to any one of the preceding claims, characterised in that the mirror layer (43.2) or the reflector layer (43) includes scattering centres or comprises a layer including scattering centres, said scattering centres allowing light to be reflected diffusely thereon; and wherein the mirror layer (43.2) or the reflector layer (43) preferably furthermore comprise at least one layer including a metal or including a chemical compound comprising a metal, for example comprising dielectric layers, wherein said at least one layer including a metal or including a chemical compound comprising a metal allows light to be reflected thereon in a directed manner; and wherein the at least one layer including the metal or including a chemical compound comprising a metal is preferably disposed above the layer that includes scattering centres, in particular in such a way that the layer including the scattering centres is at least partially enclosed on the outside.

9. The lighting system (1) according to any one of the preceding claims, characterised in that the layer thicknesses of the layers (43.1, 43.2, 43.3) are defined according to at least one of the following features: - the adhesion layer (43.1) has a thickness of more than 5 nm, preferably more than 30 nm, and / or of less than 3000 nm, preferably less than 300 nm, preferably less than 150 nm; - the mirror layer (43.2) has a thickness of more than 10 nm, preferably more than 20 nm, preferably more than 50 nm, and / or of less than 5000 nm, preferably less than 200 nm, preferably less than 100 nm; - the passivation layer (43.3) has a thickness of more than 5 nm, preferably more than 100 nm, preferably more than 150 nm, and / or of less than 5000 nm, preferably less than 500 nm, preferably less than 250 nm.

10. The lighting system (1) according to any one of the preceding claims, characterised by at least one of the following features: (i) the reflector layer (43) is arranged at the distal end (44) of the diffuser element (40) and / or at least partially encloses the diffuser element (40) laterally; (ii) the diffuser element (40) comprises scattering elements which are included in the matrix of the diffuser element (40), and / or the matrix of the diffuser element (40) is laterally enclosed by a material that includes scattering elements; (iii) the diffuser element (40) comprises borosilicate glass or phosphate crown glass or lead silicate glass or tin silicate glass or alkali zinc glass, and / or the scattering elements comprise white glass rods, in particular enclosed by a cladding tube preferably made of borosilicate glass; (iv) the diffuser element (40) is structured at least partially or in sections of its volume and / or on its surface, or the diffuser element (40) comprises a coloured or colourless, in particular transparent jacket, preferably made of a coloured glass or a coloured plastics material.

11. The lighting system (1) according to at least one of the preceding claims, characterised in that the mirror layer (43.2) or the reflector layer (43) exhibit a reflectance and / or transmittance that is different by preferably at least 10 %, most preferably by at least 30 %, for two different wavelengths λ1 and λ2 with a difference of preferably Δλ = |λ1 - λ2| < 200 nm, most preferably Δλ = |λ1 - λ2| < 100 nm; and wherein the light source (10) of the lighting system is preferably adapted so that an emission of the different wavelengths λ1 and λ2 can be set, so that the lighting system (1) can switch between different emission characteristics.

12. A method for producing a lighting system (1) for a medical technology therapy and / or diagnosis system, in particular for use on living tissue, comprising at least one light source (10), a light guide (30) which is connectable to the light source (10) at a proximal end thereof or assignable thereto, and an optical element, preferably in the form of a diffuser element (40) and arranged at a distal end of the light guide (30), and wherein light from the light guide (30) can be injected into the optical element, comprising the steps of: - providing the optical element, said optical element defining a longitudinal axis and having a lateral surface surrounding the longitudinal axis; - covering the lateral surface at least partially with a light-reflecting reflector layer (43), wherein said reflector layer (43) comprises a mirror layer (43.2) and, in addition to the mirror layer (43.2), comprises a lower layer (43.1) disposed below the mirror layer (43.2), so that the optical element (40) comprises a light-reflecting area that is covered by the reflector layer (43), and comprises a light-transmissive area which remains free of the reflector layer (43), so that the light to be emitted by the optical element can be reflected at least partially and light can be selectively emitted from the light-transmissive area, wherein the reflector layer (43) exhibits a reflectance (101) of more than 90 % for at least one wavelength range.

13. The method according to the preceding claim, characterised by at least one of the following features: (i) pre-treating the lateral surface by producing a base layer zone having at least one modified surface property, in particular by chemical or physical processes, for modifying the surface properties of the lateral surface; (ii) applying a reflector layer (43) onto the lateral surface, in particular by vapour deposition, cathode sputter deposition, high-frequency sputter deposition, reactive sputter deposition and / or magnetron sputter deposition; (iii) applying an adhesion layer (43.1) or an adhesion promoting layer onto the lateral surface and / or applying a passivation layer (43.3) onto the reflector layer (43), preferably by vapour deposition, cathode sputter deposition, high-frequency sputter deposition, reactive sputter deposition and / or magnetron sputter deposition.

14. The method according to the preceding claim, comprising: connecting the optical element to the distal end of the light guide (30) by connecting a first light guide portion to the optical element in a first connecting step and then connecting a second, in particular longer light guide portion to the first light guide portion in a second connecting step; and wherein, preferably, the covering of the lateral surface at least partially with a light-reflecting reflector layer is effected between the first connecting step and the second connecting step.

15. A device, comprising a lighting system (1) according to any one of claims 1 to 11 as a component, the device being in the form of: (i) a device for a medical therapy method, in particular for photodynamic therapy (PDT) or photoimmunotherapy (PIT) for tumour treatment, for endovenous laser therapy (EVLT) for the treatment of varicose veins, for laser-induced interstitial thermal therapy (LITT) or for applications in the field of dental medicine, ophthalmology, and dermatology; (ii) a device for photodynamic therapy (PDT) for tumour treatment, wherein at least one light guide (30) with the diffuser element (40) captures light emitted from other diffuser elements (40) to forward it via the light guide (30) to a detector for spectroscopic analysis and / or for a dosimetric measurement; (iii) a device for industrial applications for selectively illuminating cavities or for irradiation of samples in the context of in-vitro diagnostics.