Device for light application

Abstract

Device for light application (1), in particular for light curing of liquid materials, e.g. dental fillings within the oral cavity, the device comprising: - a handheld handpiece (10) with a housing and a light source (11) arranged inside the housing for emitting light, - a light guiding element (20) with a light guide body (21) consisting of a transparent solid, a light inlet (27) for coupling light into the light guide body (21) such that the light is guided through the transparent solid, and a light outlet (26) for coupling light out of the light guide body (21), and - a fastening device provided on the housing of the handpiece (10) and a fastening area provided on the light guide element (20) for fastening the light guide element (20) to the housing of the handpiece (10), such that light emitted by the light source (11) is coupled into the light guide body (21) through the light inlet (27) and is coupled out of the light guide body (21) outside the housing of the handpiece (10) through the light outlet (26), - wherein the light guide element (20) has a longitudinal extent and defines a first optical axis for light coupled into the light guide body (21), wherein this first optical axis runs along the longitudinal extent of the light guide element (20), and wherein the light exit (26) defines a second optical axis for light coupled out of the light guide body (21), wherein this second optical axis runs transversely to the first optical axis and - wherein the light guiding element (20) is designed in the form of a rod with a rod axis extending substantially in a straight line along its longitudinal extent, such that the second optical axis runs transversely to the rod axis at the distal end, and / or wherein a reflector (23) for coupling out light is applied to the light guiding element (20), - wherein the light guiding element (20) comprises a sheath (22) enclosing the light guide body (21) and / or the reflector (23), wherein the sheath (22) has a refractive index which is lower than the refractive index of the light guide body (21), such that a core-sheath interface is formed for guiding the light.

Description

[0001] The invention relates to a device for light application with a handheld handpiece and a light guiding element with a light guide body consisting of a solid, wherein the light guiding element can be attached to or is attached to the handheld handpiece.

[0002] US Patent 5,147,204 relates to a light-emitting device for curing dental materials. The device comprises a handpiece with a housing, handle, and detachable light guide. The light guide is housed in a head connected to the housing. A rotational movement of the head relative to the housing also rotates the light guide, allowing the guide to be rotated by the same hand of the user gripping the handle. Additionally, a pivoting connection between the housing and the handle allows for limited adjustment of the angle of the housing relative to the handle for improved handling and ease of use. The base of the device includes an upright pedestal that accommodates a device for determining the intensity of the light emitted by the light guide.The optical fiber is formed from a bundle of interconnected optical fibers, allowing the light to follow a curved path before exiting. However, this design has the disadvantage of requiring a relatively large amount of space during application. Furthermore, the production costs are relatively high.

[0003] European patent application EP 2 339 382 A1 discloses a light guide for a dental lighting device. The light guide, adapted for use with a dental lighting device, has a reflector tube for receiving light from a light source of the lighting device and for guiding the light to one end of the reflector tube. The light guide also includes a reflector plate at the end of the reflector tube. The reflector plate has a reflective surface that is inclined relative to the longitudinal axis. A disadvantage of this device, however, is that it is relatively complex to recondition the cavity formed by the reflector tube for reuse. Furthermore, the manufacturing process is relatively complex and expensive.

[0004] Other devices are known from US 2008 / 0254405 A1, US 2006 / 0040231 A1, US 6,749,427 B1, FR 2 334 785 A1, DE 26 03 513 A1.

[0005] One object of the invention is to provide a device for light application which enables light curing of dental fillings, particularly on hard-to-reach molars, wherein a cost-effectively manufactured light guiding element is desirable which requires as little space as possible during application and can also be easily processed or used as a disposable product.

[0006] This problem is solved by the subject matter of the independent claims. Advantageous embodiments are the subject matter of the dependent claims.

[0007] According to the invention, a device for applying light, in particular for light-curing liquid materials, especially dental fillings, within the oral cavity is provided. The device comprises a handheld handpiece and a light-guiding element.

[0008] The handheld device has a housing and a light source located inside the housing for emitting primarily blue light. However, other wavelengths can also be provided, as will be explained in more detail below.

[0009] The light guide element comprises a light guide body made of a solid material. Furthermore, the light guide element has a light inlet for coupling light into the light guide body and a light outlet for coupling light out of the light guide body. In other words, the light guide element directs light through a transparent solid material.

[0010] The device further comprises a fastening device provided on the housing of the handpiece and a fastening area provided on the light guide element, wherein the fastening device and the fastening area are each configured to fasten the light guide element to the housing of the handpiece such that light emitted by the light source is coupled into the light guide element through the light inlet and coupled out of the housing of the handpiece through the light outlet of the light guide element. In other words, the light guide element can be fastened to, or is fastened to, the housing of the handpiece. The fastening area of ​​the light guide element is, in particular, arranged at its proximal end.

[0011] The light guide element is designed such that a first optical axis for coupled-in light runs perpendicular to a second optical axis for coupled-out light. The light guide element thus defines a first optical axis for light coupled into the light guide body, with this first optical axis running along a longitudinal dimension of the light guide element. Furthermore, the light exit point defines a second optical axis for light coupled out of the light guide body, with this second optical axis running perpendicular, i.e., not parallel, to the first optical axis. The light guide element is therefore designed such that light is coupled out at least partially laterally to the first optical axis, for example, at an angle of 90 degrees.

[0012] The light guide element and / or the light guide body has, in particular, the form of a rod with a rod axis running along its longitudinal extent, which is essentially straight. In other words, the light guide element and / or the light guide body is essentially straight.

[0013] The optical axis of the coupled-out light (the second optical axis) thus also runs transversely to the longitudinal extent and / or the rod axis of the light guide element, particularly transversely to the longitudinal extent and / or rod axis in the distal region. In other words, the light is coupled out laterally.

[0014] A flat light guide element can be provided by using a essentially straight light guide designed to laterally couple out light. This flat design requires minimal space, thus enabling, for example, the curing of dental fillings, particularly in molars.

[0015] The light-guiding element and / or the light-guiding body has, in particular at a proximal end of its longitudinal extension, a proximal end face, which preferably forms the light entry point. A distal end face is preferably provided at a distal end of the longitudinal extension. The proximal and / or the distal end face can be flat or have a curvature, as described in more detail below.

[0016] Preferably, the light guide element 20 has a reflector designed to couple light out of the light guide body, particularly laterally. The reflector is preferably applied to the distal end face; for example, the reflector can be applied substantially across the entire distal end face. The reflector is thus preferably positioned opposite the mounting area of ​​the light guide element.

[0017] The reflector can be designed as a mirror or interference mirror with one or more layers, whereby the coating or layers can be vapor-deposited and / or sputtered, for example, directly onto the optical fiber. The reflector can therefore be applied directly to the optical fiber, i.e., without any further underlying layer.

[0018] As already mentioned, the light exits along the second optical axis at least partially laterally to the first optical axis. Preferably, the second optical axis runs at an angle to the first optical axis of between 45 and 135 degrees, preferably between 70 and 110 degrees, particularly preferably between 80 and 100 degrees, and even more preferably between 85 and 95 degrees.

[0019] This can be achieved in particular by aligning the distal frontal surface and / or the reflector such that a normal vector of the distal frontal surface and / or of the reflector, e.g., applied to the distal frontal surface, forms an angle with the first and / or second optical axis which lies between 157.5 and 112.5 degrees, preferably between 145 and 125 degrees, particularly preferably between 140 and 130 degrees, and even more preferably between 137.5 and 132.5 degrees.

[0020] The reflector exhibits a reflectivity of over 90 percent, preferably over 95 percent, and particularly preferably over 99 percent, especially for light with a wavelength between 380 and 500 nanometers.

[0021] Through a clever design of the prism, cost-effective manufacturing via grinding and polishing from bar stock can be achieved. For this, it is advantageous if the outer contour consists only of flat surfaces. In other words, it can be beneficial for the light-guiding element, which is designed, for example, as a rod, to have a shape defined by a plurality of surfaces, where, in particular, all surfaces are planar or flat. A polygonal cross-sectional area can therefore be provided. For example, the cross-sectional area can be triangular, quadrilateral (e.g., square or rectangular), but also pentagonal, hexagonal, etc.

[0022] The light guide element 20 is preferably designed such that the emission angle of the light coupled out of the light guide body is less than 30 degrees, preferably less than 20 degrees, and particularly preferably less than 10 degrees. This can be achieved in particular by making the distal end face and / or the reflector flat, convex, or concave.

[0023] In one embodiment, the solid-state optical fiber is made of glass, in particular as a pressed glass part. For example, it may include borosilicate glass and / or optical crown glass. In another embodiment, the optical fiber is made of plastic, in particular as a plastic injection-molded part, which may include polycarbonate (PC), polymethyl methacrylate (PMMA), and / or cycloolefin copolymers (COC).

[0024] The material of the optical fiber is preferably substantially homogeneous and / or substantially isotropic. In particular, the optical fiber is therefore preferably not designed as a fiber bundle, i.e., preferably not a fiber-based optical fiber. In other words, no fiber optic elements are provided, but rather, as described, preferably glass or plastic molded parts, which may be coated and may have at least one reflector element.

[0025] The optical fiber is preferably monolithic or formed in one piece. In other words, the optical fiber preferably does not consist of a plurality or number of interconnected components, and in particular not of interconnected individual optical fibers. The optical fiber can thus form the single light-conducting core of the optical element.

[0026] The light guide element comprises a sheath that partially or completely encloses the light guide body and / or the reflector. The sheath has a refractive index lower than that of the light guide body and is preferably formed as a SiO2 sputter layer, a plastic layer, or a liquid silicone rubber coating. As described, the light guide body is preferably homogeneous, isotropic, and / or monolithic. In particular, the light guide body can have a substantially homogeneous and / or isotropic refractive index. The sheath, if any, applied to the light guide body can also preferably have a homogeneous and / or isotropic refractive index. In other words, it is possible for the light guide body to have only one refractive index and / or for any sheath to have only one refractive index.

[0027] Surprisingly, sometimes a very small difference in refractive index and a thin cladding are sufficient to generate a light-guiding effect adequate for the application. Depending on the specific application, the following factors may be responsible for this.

[0028] A first consideration is that the cross-sectional area of ​​the light guide can be significantly larger than the area of ​​the light source, such as LEDs, which emit the predominantly blue light. For the radiant power required in certain applications, a chip area of ​​approximately 2–4 square millimeters is sufficient according to the current state of LED technology. With further developments toward higher efficiencies and power densities, this area is expected to decrease in the future. The cross-sectional area of ​​the light guide element is primarily determined by the size of the area to be illuminated homogeneously. In the case of curing a filling material, this area ranges, for example, from 7 x 7 square millimeters to 12 x 12 square millimeters, whereby the cross-sectional area need not be square but can also have other shapes with the same cross-sectional area.Since the light exits the light guide element divergently, the cross-sectional area of ​​the light guide can be somewhat smaller. Preferably, it can be in the range of 5 x 5 square millimeters to 10 x 10 square millimeters, and the shape is not limited to square surfaces. This difference in cross-sectional area can be used to align the light at the point of coupling into the light guide element. For example, starting with an LED with an edge length of 2 mm, which emits 75% of its radiant power as a Lambertian radiator within an angular range of ±60°, and a light guide element with an edge length of 7 mm, a reduction of the angular range to <±27° is achieved. More generally, the cross-sectional area of ​​the light guide element, particularly of the light entry point, can therefore be larger than the emitting area of ​​the light source, especially by a factor between 6 and 36, preferably between 12 and 25.

[0029] Another important factor is that, unlike conventional optical fibers, the aspect ratio of diameter to length in optical fibers can differ by orders of magnitude. For example, in an optical fiber with a diameter of 50 µm and a length of 10 cm (as is typical in this application), the aspect ratio is 10 cm / 50 µm = 2000. This means that a very large number of reflections occur at the core-cladding interface during light transmission through such a fiber. The losses due to reflection are compounded. Assuming, for example, 500 reflections with an efficiency of 99%, only 99%^500 = 0.66% of the light reaches the exit surface. To achieve an efficiency of > 90% for the optical fiber, each individual reflection must have an efficiency of at least 90%^(1 / 500) ~ 99.98%.

[0030] In contrast, the homogeneous, isotropic, and / or monolithic optical fiber has, for example, an aspect ratio of 10 cm / 7 mm = 14. Therefore, in this example, there are > 100 fewer reflections at the core-shell interface; compared to the example above, this equates to 3 to 4 reflections during passage through the optical fiber. The device and / or the optical fiber can therefore be designed such that the light coupled into the optical fiber is reflected less than 100, preferably less than 50, and particularly preferably less than 10 times within the optical fiber before being coupled out again.

[0031] Another factor concerns the thickness of the cladding. The losses due to reflection at the core-cladding interface are primarily determined by the difference in refractive indices between the core and cladding, and by the thickness of the cladding. An example of a light guide element with a core made of B270 glass (refractive index 1.52) and a cladding made of SiO2 (refractive index 1.46) has a nominal numerical aperture of 0.42 and can therefore guide light up to a coupling angle of up to 25° perpendicular to the end face. Light at particularly steep angles penetrates deep into the cladding. The attenuation of the light intensity in the cladding is, for example, on the order of 1 / e = 0.37 at a depth of one wavelength (e.g., 450 nm, depending on the application).

[0032] A reflection efficiency of 99.98% (see the example above with 99.98%) would then correspond to a decrease in intensity across the thickness of the coating to 0.02%. In this example, the layer would therefore need to be 8 to 9 times the wavelength thick. For an example wavelength of 450 nm, this corresponds to approximately 4 µm. This thickness is considerable, especially for sputtered SiO2 layers, and can have a detrimental impact on processing times and thus costs. Furthermore, residual stresses can increase with increasing layer thickness, sometimes leading to faster delamination of the layer and consequently to component failure.

[0033] In contrast, with a smaller number of reflections (see preferred values ​​given above), for example 3 to 4 reflections, a layer thickness of approximately 3 times the wavelength, i.e. 1.5 µm, may be sufficient.

[0034] These circumstances, which are sometimes rather atypical for other LED light guide applications, especially the small coupling angle and the small aspect ratio of length to diameter, advantageously lead to the optical requirements for the cladding being lower than usually expected and therefore suitable for small refractive index differences (e.g. n). Kern -n Mantel ~ 0.05) as well as with small shell thicknesses (e.g. d Mantel ~ 1.5 µm) a good light transmission efficiency on the order of 90% can be achieved.

[0035] The resulting preferably small difference in refractive index also advantageously simplifies the selection of a material pairing of light guide body and cladding with good technical properties (high transmission, low thermal expansion, etc.) and commercial properties (low material costs, easy processing, good availability, etc.).

[0036] The difference between the refractive index of the optical fiber and the refractive index of the cladding is preferably less than or equal to 0.16, and more preferably less than or equal to 0.08. Furthermore, the thickness of the cladding is preferably less than or equal to 3 µm, and more preferably less than or equal to 2 µm.

[0037] The longitudinal extent of the light guide element and / or the light guide body is preferably between 1 and 30 centimeters, particularly preferably between 5 and 15 centimeters, and even more preferably between 8 and 12 centimeters. As described above, the light guide body is preferably substantially homogeneous, isotropic, and / or monolithic over this length.

[0038] Preferably, the light guide element and / or the light guide body has a cross-section along its longitudinal extent with an area between 0.1 and 3 square centimeters, particularly preferably between 0.3 and 1.2 square centimeters, and even more preferably between 0.5 and 1.0 square centimeters. The light guide body is preferably substantially homogeneous, isotropic, and / or monolithic across this cross-section, as already described above.

[0039] The aforementioned cross-sections are used in particular to provide a light guide for the curing of dental fillings, which has an extremely flat design and, as explained above, preferably emits the light to the side.

[0040] It may be provided that the light guiding element has a variable cross-section along its longitudinal extent, in particular along the rod axis.

[0041] For example, the cross-section of the light guide element can be round, particularly circular, at the proximal end and angular, particularly rectangular or square, at the distal end. A transition zone can be provided between the proximal and distal ends.

[0042] It is also possible for the cross-section of the light guide element to be conical at the proximal end to facilitate the coupling of divergent light. In this case, the outermost proximal end can have the smallest cross-section, with this cross-section increasing along the longitudinal extent.

[0043] In a further development of the invention, a further light source for emitting red light can be included, wherein the device is configured to switch between the emission of blue light and the emission of red light. A switch can therefore be provided. More generally, it can also be provided that several light sources for emitting light of different wavelengths are included.

[0044] In a further development of the invention, a voltage source for providing an electrical voltage to operate the light source can be arranged within the housing of the handheld device. Such a voltage source can, for example, be designed as a rechargeable energy storage device. In this case, it is advantageous if the light application device also includes a charging station designed to recharge the rechargeable energy storage device.

[0045] The light guide element can be detachably attached to the handpiece housing. For example, the mounting device provided on the handpiece housing can be designed as a mounting sleeve, so that the light guide element can preferably be detachably mounted in the mounting sleeve.

[0046] The invention further relates to a handheld device for a light application device, comprising a light guide element with a solid-state light guide body, a light inlet for coupling light into the light guide body, and a light outlet for coupling light out of the light guide body, particularly as described above. The handheld device according to the invention comprises a housing and a light source arranged within the housing for emitting light, and a fastening device provided on the housing for attaching the light guide element to the housing, such that light emitted by the light source is coupled into the light guide body of the light guide element through the light inlet of the light guide element and is coupled out of the light guide body of the light guide element outside the housing through the light outlet of the light guide element.

[0047] The handheld handpiece according to the invention can in particular have the features described above in connection with the device for light application.

[0048] The invention further relates to a light guiding element, in particular for a device for light application with a handheld handpiece with a housing, a light source arranged inside the housing for emitting light and a fastening device provided on the housing of the handpiece, in particular as described above.

[0049] The light guiding element according to the invention comprises a light guide body made of a solid, a light inlet for coupling light into the light guide body, a light outlet for coupling light out of the light guide body, and a mounting area for attaching the light guide element, in particular to the housing of the handpiece of the device for light application, such that light emitted by the light source is coupled into the light guide body through the light inlet and is coupled out of the light guide body through the light outlet outside the housing of the handpiece of the device for light application.

[0050] The light guide element according to the invention has a longitudinal extent and defines a first optical axis for light coupled into the light guide body, wherein this first optical axis runs along the longitudinal extent of the light guide element, and the light exit defines a second optical axis for light coupled out of the light guide body, wherein this second optical axis runs transversely to the first optical axis.

[0051] The light guiding element according to the invention can in particular have the features described above in connection with the device for light application.

[0052] The invention further relates to the use of a light guiding element, as described above, for curing liquid materials, in particular for industrial adhesive curing.

[0053] Furthermore, the invention relates to the use of a light-guiding element, particularly as described above, especially for hard-to-reach areas in the mouth, e.g., in the area of ​​the molars. Blue light can be used in this context. The invention further relates to the use of a light-guiding element, particularly as described above, for wound healing in the mouth. Red light can be used in this context. The invention also relates to the use of a light-guiding element, particularly as described above, for caries detection. Illumination with blue light, e.g., at 405 nm, can be used in this context, and / or surface detection in the green or red spectral range can be achieved by using a filter. The invention also relates to the use of a light-guiding element, particularly as described above, for skin treatment with visible light and / or IR light.

[0054] Further embodiments of the invention are explained in more detail with reference to the accompanying drawings. These show: Fig. 1: A side view of a device for light application with a light guiding element, a handheld handpiece and a charging cradle, Fig. 2: A side view of a light guide element with a reflector and a sheath, Fig. 3: A side view of a light guide element with a reflector and a sheath and a conically shaped proximal end.

[0055] Fig. Figure 1 shows a curing device 1 for curing, in particular, dental fillings. The curing device 1 comprises a handpiece 10 with a light guide element 20, which can be fixed in the handpiece 10 by means of a mounting sleeve 25. A light source 11, which can be, for example, an LED, in particular a blue LED, is arranged in the handpiece 10 at an entry surface of the light guide element 20. The handpiece 10 with the light guide element 20 can be removed from a charging station 30 for treatment. Furthermore, after treatment, it can be inserted back into the charging station 30 to recharge the batteries integrated in the handpiece 10. Separation between the light guide element 20 and the handpiece 10 allows for medical reprocessing (cleaning, disinfection, autoclaving) of the light guide element 20 after treatment.

[0056] Fig. Figure 2 shows a light guide element 20 with a light guide body 21 made of transparent plastic or glass, which has a sheath 22 made of a similarly transparent material, wherein the refractive index of the light guide body 21 is greater than the refractive index n2 of the sheath 22, so that light guidance in the light guide body 21 can be ensured. A reflector 23 is provided at the light exit 26, which deflects the light and couples it out essentially perpendicular to the central axis of the light guide body 21.

[0057] The light guide 21 preferably has a square or rectangular cross-section in the region of the reflector 23, which facilitates light extraction via the reflector 23. In contrast, the light guide 21 can have a circular cross-section in the region of light extraction (light entry 27). Furthermore, the light guide 21 has a shape transition region along its longitudinal axis. Since many high-power LEDs, in particular, have a square cross-section, a more square cross-sectional shape can also be advantageous here.

[0058] The reflector 23 can be designed as an additionally applied mirror element or as a vapor-deposited or sputtered interference mirror (dichroic mirror), e.g., consisting of a multitude of layers, which exhibits very high reflectivity (> 99%), particularly for the wavelength of the light used, typically blue light between 380 and 500 nm. The reflector 30 can be covered with the cladding material. This is particularly advantageous for two reasons. Firstly, the light-guiding element can be coated across its entire surface, eliminating the need for additional shading. Secondly, the cladding protects the mirror layer and / or the adhesive bond between the glass and the mirror from adverse environmental influences. In particular, it prevents or significantly reduces the penetration of water or water vapor into the interface between the glass and the mirror. This significantly increases the service life of the light-guiding element.

[0059] The reflector 30 can also be slightly curved, e.g., parabolic, to enable a more diffuse or more focused beam pattern. The reflector can also consist of several flat faceted surfaces. In principle, other freeform shapes are also possible, resulting in specific beam shapes.

[0060] Fig.Figure 3 shows a further embodiment in which the light guide 21 has a conical section 24 in the area of ​​light coupling. This makes it possible to capture and couple the light from LEDs, which is usually emitted at a large angle, and to couple it into the light guide. Preferably, the design of the handpiece 10 with the light source 11, here the LED chip, is such that the coupling surface of the light guide 20 is arranged directly at a small distance (for example, less than 1 cm, or preferably less than 1 mm) from the light source, here the LED chip.

[0061] The light guide element 21 can be manufactured as a glass pressing or as a plastic injection molding part. This allows for cost-effective shaping.

[0062] Borosilicate glass, for example, is suitable as the glass, particularly due to its low coefficient of thermal expansion (CTE), high temperature resistance, very good optical properties, and high transmission. Optical glasses such as SCHOTT BK7® are also suitable. A SiO2 sputter layer, which has a lower refractive index than that of the light guide 21, can serve as the cladding 22. A liquid silicone rubber (LSR) coating of the light guide 21 is also conceivable. LSR is known as a crystal-clear silicone that can be applied to the light guide 21 by dip coating or injection molding. A cladding 22 made of LSR has the advantage of also providing mechanical protection. The high temperature resistance of 200°C also allows for processing, particularly by autoclaving at typically 135°C and approximately 3 bar vapor pressure.

[0063] The light guide element 21 can also be made of clear, transparent plastic. For example, plastics such as PC, PMMA, and COC (e.g., TOPAS®) are used, which are coated in a two-stage injection molding process, for instance, with a plastic with a lower refractive index as a sheath 22. LSR can also be used as the sheath material here. A SiO2 spatter layer is also conceivable. This allows for the very cost-effective production of such light guide elements 20 in large quantities, which can then be manufactured, for example, as so-called "disposables," i.e., for single treatment. These are simply sterilized before delivery (usually by ethylene oxide gassing) and packaged sterile.

[0064] In the above embodiments, with regard to the design of a mounting sleeve 25, it can be provided that this is glued onto the light guide body 21 with the sheath 22 as a metal or plastic sleeve (e.g. made of PPSU) by means of an adhesive (e.g. 2k epoxy adhesive) or is molded in a further injection molding process (e.g. using PPS). Reference symbol list: 1 Curing device 10 Handpiece 11 Light source 20 light guiding elements 21 optical fibers 22 coat 23 Reflector 24 Cone section 25 Mounting sleeve 26 Light emission 27 Light entry 30 charging stations

Claims

[1] Device for applying light (1), in particular for light curing of liquid materials, e.g. dental fillings within the oral cavity, the device comprising: - a handheld handpiece (10) with a housing and a light source (11) arranged inside the housing for emitting light, - a light guiding element (20) with a light guide body (21) consisting of a transparent solid, a light inlet (27) for coupling light into the light guide body (21) such that the light is guided through the transparent solid, and a light outlet (26) for coupling light out of the light guide body (21), and - a fastening device provided on the housing of the handpiece (10) and a fastening area provided on the light guide element (20) for fastening the light guide element (20) to the housing of the handpiece (10), such that light emitted by the light source (11) is coupled into the light guide body (21) through the light inlet (27) and is coupled out of the light guide body (21) outside the housing of the handpiece (10) through the light outlet (26), - wherein the light guide element (20) has a longitudinal extent and defines a first optical axis for light coupled into the light guide body (21), wherein this first optical axis runs along the longitudinal extent of the light guide element (20), and wherein the light exit (26) defines a second optical axis for light coupled out of the light guide body (21), wherein this second optical axis runs transversely to the first optical axis and - wherein the light guiding element (20) is designed in the form of a rod with a rod axis extending substantially in a straight line along its longitudinal extent, such that the second optical axis runs transversely to the rod axis at the distal end, and / or wherein a reflector (23) for coupling out light is applied to the light guiding element (20), - wherein the light guiding element (20) comprises a sheath (22) enclosing the light guide body (21) and / or the reflector (23), wherein the sheath (22) has a refractive index which is lower than the refractive index of the light guide body (21), such that a core-sheath interface is formed for guiding the light. [2] Device for light application (1) according to claim 1, - wherein the light guiding element (20) has a proximal end face at a proximal end of its longitudinal extent, in particular forming the light entry (27) and / or - wherein the light guiding element (20) has a distal end face at a distal end of its longitudinal extension. [3] Device for light application (1) according to one of claims 1 or 2, - wherein the reflector (23) is applied to the distal frontal surface and - wherein the reflector (23) is preferably designed as a mirror or interference mirror with one or more layers, which is preferably vapor-deposited and / or sputtered. [4] Device for light application (1) according to any one of claims 1 to 3, - wherein the second optical axis is at an angle to the first optical axis which is between 45 and 135 degrees, preferably between 70 and 110 degrees, particularly preferably between 80 and 100 degrees, and even more preferably between 85 and 95 degrees, in particular by orienting the distal frontal surface and / or the reflector 23 such that a normal vector of the distal frontal surface and / or of the reflector 23 applied to the distal frontal surface forms an angle with the first and / or second optical axis which is between 157.5 and 112.5 degrees, preferably between 145 and 125 degrees, particularly preferably between 140 and 130 degrees, and even more preferably between 137.5 and 132.5 degrees. [5] Device for light application (1) according to one of claims 3 or 4, - wherein the reflector (23) for light with a wavelength between 380 and 500 nanometers has a reflectivity of over 90 percent, preferably over 95 percent, particularly preferably over 99 percent. [6] Device for light application (1) according to any one of claims 1 to 5, - wherein the light guiding element (20) is designed such that light coupled out of the light guiding body 21 has a beam angle of less than 30 degrees, preferably less than 20 degrees, particularly preferably less than 10 degrees, in particular by having the distal end face and / or the reflector (23) be flat, convex or concave. [7] Device for light application (1) according to any one of claims 1 to 6, - wherein the optical fiber (21) consisting of a solid is made of a homogeneous material and / or - wherein the optical fiber (21) consisting of a solid is made of an isotropic material and / or - wherein the light guide body (21), consisting of a solid, is monolithic. [8] Device for light application (1) according to any one of claims 1 to 7, - wherein the light guide body (21) is made of glass, in particular as a glass pressing, comprising borosilicate glass and / or optical crown glass. [9] Device for light application (1) according to any one of claims 1 to 7, - wherein the light guide body (21) is made of plastic, in particular as a plastic injection molded part, comprising polycarbonate (PC), polymethyl methacrylate (PMMA) and / or cycloolefin copolymers (COC). [10] Device for light application (1) according to any one of claims 1 to 9, - wherein the jacket (22) is designed as a SiO2 sputter layer, as a plastic layer or as a liquid silicone rubber coating. [11] Device for light application (1) according to claim 10, - wherein the difference between the refractive index of the light guide body (21) and the refractive index of the cladding (22) is less than or equal to 0.16, preferably less than or equal to 0.

08. [12] Device for light application (1) according to one of claims 10 or 11, - wherein the thickness of the cladding (22) is less than or equal to 3 µm, preferably less than or equal to 2 µm. [13] Device for light application (1) according to any one of claims 1 to 12, - wherein the longitudinal extent of the light guiding element (20) and / or the light guiding body (21) is between 1 and 30 centimeters, preferably between 5 and 15 centimeters, particularly preferably between 8 and 12 centimeters and / or - wherein the light guiding element (20) and / or the light guiding body (21) has a cross-section along its longitudinal extent, the area of ​​which is between 0.1 and 3 square centimeters, preferably between 0.3 and 1.2 square centimeters, and particularly preferably between 0.5 and 1.0 square centimeters. [14] Device for light application (1) according to any one of claims 1 to 13, - wherein the light guiding element (20) has a variable cross-section along its longitudinal extent, in particular along the rod axis. [15] Device for light application (1) according to claim 14, - wherein the cross-section of the light guiding element (20) is round, in particular circular, at the proximal end and angular, in particular rectangular, at the distal end and wherein a shape transition area is provided between the proximal and the distal end. [16] Device for light application (1) according to one of claims 14 or 15, - wherein the cross-section of the light guide element (20) is conical at the proximal end to facilitate the coupling of divergent light. [17] Device for light application (1) according to any one of claims 1 to 16, - comprising a further light source for the emission of red light and wherein the device is configured to switch between the emission of blue light and the emission of red light. [18] Device for light application (1) according to any one of claims 1 to 17, - wherein a voltage source for providing an electrical voltage for operating the light source (11) is arranged within the housing of the handheld handpiece (10) and - wherein the voltage source is preferably designed as a rechargeable energy storage device and wherein the device for light application (1) further comprises a charging station (30) designed to charge the rechargeable energy storage device. [19] Device for light application (1) according to any one of claims 1 to 18, - wherein the fastening device provided on the housing of the handpiece (10) is designed as a mounting sleeve (25) and wherein the light guiding element (20) can preferably be detachably mounted in the mounting sleeve (25). [20] Light guiding element (20), in particular for a device for light application (1) with a handheld handpiece (10) with a housing, a light source (11) arranged inside the housing for emitting light and a fastening device provided on the housing of the handpiece (10), in particular according to one of claims 1 to 19, wherein the light guiding element (20) comprises: - a light guide body consisting of a transparent solid (21), - a light inlet (27) for coupling light into the light guide body (21) such that the light is guided through the transparent solid body, - a light exit (26) for coupling light out of the light guide body (21) and - a mounting area for attaching the light guide element (20) in particular to the housing of the handpiece (10) of the device for light application (1), such that light emitted from the light source (11) is coupled into the light guide body (21) through the light inlet (27) and is coupled out of the light guide body (21) outside the housing of the handpiece (10) of the device for light application (1) through the light outlet (26), - wherein the light guide element (20) has a longitudinal extent and defines a first optical axis for light coupled into the light guide body (21), wherein this first optical axis runs along the longitudinal extent of the light guide element (20), and wherein the light exit (26) defines a second optical axis for light coupled out of the light guide body (21), wherein this second optical axis runs transversely to the first optical axis and - wherein the light guiding element (20) is designed in the form of a rod with a rod axis extending substantially in a straight line along its longitudinal extent, such that the second optical axis runs transversely to the rod axis at the distal end, and / or wherein a reflector (23) for coupling light out is applied to the light guiding element (20), - wherein the light guiding element (20) comprises a sheath (22) enclosing the light guide body (21) and / or the reflector (23), wherein the sheath (22) has a refractive index which is lower than the refractive index of the light guide body (21), such that a core-sheath interface is formed for guiding the light. [21] Use of a light guiding element (20) according to claim 20 for curing liquid materials, in particular for industrial adhesive curing.

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