Emitter and method for light emission

Abstract

An emitter (1) and a method for emitting light are described. The emitter (1) has a substrate (2) with a substrate surface (3) and at least one LED element (5) arranged on the substrate surface (3) for generating light to be emitted. An active cooling unit for cooling the at least one LED element (5) has at least one cooling channel (7). The at least one cooling channel (7) is arranged on the substrate surface (3) in a beam path of at least a portion of the light to be emitted for redirecting the light to be emitted, which can be generated by the at least one LED element (5).

Description

[0001] The content of the German patent application DE 10 2019 213 150.6 is incorporated herein by reference. TECHNICAL FIELD

[0002] The present invention relates to an emitter for emitting light, in particular visible light, infrared light and / or UV light. In particular, the present invention relates to a lamp for emitting visible light. Furthermore, the present invention relates to a method for emitting light by an emitter. BACKGROUND

[0003] EP 1 681 728 A1 describes a luminaire with LED light emitting elements which generate ultraviolet light (UV light). The UV light is converted into visible light by light conversion means. Heat dissipation elements are provided for cooling the light conversion means. According to DE 10 2007 054 039 A1, a liquid is known to be used for light conversion of light emitting diodes. DE 10 2010 007 687 A1 describes an LED lamp with a heat pipe as cooling system. US 2005 / 0094397 A1 describes a light source and a projector. SUMMARY

[0004] It is an object of the present invention to provide an improved emitter for emitting light. In particular, an emitter is to be provided which is structurally efficient and simple.

[0005] This object is achieved by an emitter having the features according to claim 1. The emitter has a substrate with a substrate surface. At least one LED element for generating light to be emitted is arranged on the substrate surface. The emitter has an active cooling unit for cooling the at least one LED element with at least one cooling channel for a coolant. At least one cooling channel is arranged in a beam path of at least a portion of the light to be emitted for redirecting the light to be emitted which can be generated by the at least one LED element. In particular, the at least one cooling channel is arranged on the substrate surface. According to the present invention, it can be recognized that the at least one cooling channel for cooling the at least one LED element can also be used for redirecting light which can be generated by the LED element. In this way, the emission properties of the emitter can be adapted in a simple manner. It can be dispensed with using further optical elements. The emitter is efficient and structurally simple.

[0006] The light which can be generated by the at least one LED element is usually distributed uniformly over the entire solid angle of 2p above the substrate surface. By redirecting at least a portion of this light by the at least one cooling channel, the distribution of the light, in particular the covered solid angle, can be changed. For example, the redirection of the light takes place by reflection and / or refraction of the light at the at least one cooling channel.

[0007] By redirecting at least a portion of this light via the at least one cooling channel, it is possible, inter alia, to concentrate the light to be emitted by the emitter. By concentrating, it is understood that the solid angle range in which the emitter emits light is reduced. This increases the intensity of the emitted light in the solid angle range covered. The emitter efficiently illuminates a predefined solid angle range.

[0008] The emitter serves for emitting light. In the use of a spotlight, the at least one LED element directly generates the light to be emitted. This means that the emitter emits light in the frequency range that can be generated by the at least one LED element. There is no need for a conversion or frequency change of the light generated by the at least one LED element. The redirection of the light to be emitted takes place without changing the frequency of the light to be emitted. In particular, the light generated by the at least one LED element is not absorbed by the light conversion unit to be converted into a different frequency range. Thus, the redirection of at least a portion of this light by the at least one cooling channel takes place without changing the frequency of the light generated by the at least one LED element. The efficiency of the emitter is improved.

[0009] The light to be emitted is, inter alia, visible light, infrared light and / or UV light. For example, the light to be emitted can have a frequency between 180 THz and 3000 THz. Visible light is electromagnetic radiation in the frequency range that can be perceived by the human eye. In general, the visible light frequency range extends from about 400 Thz to 790 THz. In order to emit visible light, the light is generated directly by the LED element. The electromagnetic radiation generated by the LED element is not converted into visible light. In particular, the UV light generated by the LED element is not converted into visible light. The emitter for emitting visible light serves for illumination, also referred to as a lamp or luminaire. Preferably, the light to be emitted covers the visible light frequency range. Particularly preferably, the light to be emitted is white light. The emitter can be a white light luminaire.

[0010] The emitter for emitting infrared light can be used, for example, in surveillance cameras for infrared illumination, in image recognition and monitoring systems and in data transmission systems. Infrared light in the near-infrared range is particularly suitable. For example, it has a frequency of between about 180 Thz and about 399 THz.

[0011] The emitter for emitting UV light is used, for example, for disinfection, UV curing and UV drying. UV light in the near-UV range is particularly suitable. For example, the frequency of suitable UV light can be between about 791 THz and about 3000 THz. LED elements for generating UV light are generally very inefficient, for example with an efficiency of less than 20%. Thus, the efficiency gain that can be achieved by the redirection, in particular the concentration, of the light to be emitted is particularly advantageous for emitters for emitting UV light.

[0012] The substrate is in particular a printed circuit board. The substrate has a substrate surface on which at least one LED element is arranged. In particular, the substrate has an additional substrate surface which is spaced apart from the first substrate surface by a substrate thickness. For a more precise differentiation, the substrate surface on which at least one LED element is arranged is also referred to in the following as the first substrate surface and the additional substrate surface on which at least one LED element is not arranged is also referred to in the following as the second substrate surface. If in the following only a "substrate surface" is quoted, this means the substrate surface on which at least one LED element is arranged.

[0013] The emitter has at least one LED element, in particular a plurality of LED elements. In the case of a plurality of LED elements, these can be arranged randomly on the first substrate surface. Preferably, the plurality of LED elements is arranged on the first substrate surface at regular intervals.

[0014] The at least one LED element can have one or a plurality of LEDs, respectively. In particular, the at least one LED element has at least one LED chip, in particular a high-power chip. In particular, the LED element is also referred to as an LED light device if it can generate visible light with it. For emitting visible light, the LED light device can in particular have an LED chip which can be used to generate visible light, in particular dedicated visible light. Alternatively or additionally, light in the non-visible light range can be generated by the at least one LED chip. If necessary, the at least one LED light device can comprise a light conversion unit by means of which the light generated by the at least one LED chip is converted into visible light.

[0015] The active cooling unit serves for cooling the at least one LED element. The active cooling unit has cooling channels for a coolant, in particular a cooling liquid. The coolant is pumped in the at least one cooling channel by means of a pump of the active cooling unit.

[0016] The at least one cooling channel is arranged at or adjacent to the first substrate surface. The at least one cooling channel is arranged on the same substrate surface as the at least one LED element. The at least one LED element is cooled directly. There is no need to dissipate heat via the substrate, for example to a cooling channel arranged at the second substrate surface. The cooling of the at least one LED element is efficient.

[0017] The active cooling unit in particular has a plurality of cooling channels, preferably a network of cooling channels. The course of the cooling channels can be adapted to the arrangement of the plurality of LED elements on the first substrate surface. In particular, the plurality of cooling channels extends along the first substrate surface between the LED elements.

[0018] The emitter according to claim 2 ensures a directional and efficient redirection of light, in particular a bunching of light. The main emission direction is in particular defined as being perpendicular to the substrate surface. A deflection in the direction of the main emission direction is understood as meaning that a component of the direction of spread of the beam path of the light is amplified in the main emission direction. For example, the beam path of the light that can be generated by the LED element has an emission angle b with respect to the main emission direction, wherein 0° ≤ b ≤ 90°. For b ≠ 0°, the beam path is not parallel to the main emission direction. Where appropriate, a deflection in the main emission direction in particular results in a deflected beam path that has an angle b' with respect to the main emission direction, wherein: 0° ≤ b' < b. The light intensity in the direction of the main emission direction is increased.

[0019] The emitter according to claim 3 ensures an especially efficient redirection, in particular a bunching, of the light to be emitted. The reflection at the cooling channel boundary surface of the at least one cooling channel results in a directional and controlled redirection of at least a portion of the light to be emitted. The light reflected at the at least one cooling channel does not penetrate into the cooling channel and thus does not suffer any attenuation. The reflection of at least a portion of the light can also occur by total reflection of the light at the cooling channel boundary surface. In addition or alternatively, the area of the cooling channel boundary surface that is illuminated by at least a portion of the light that can be generated by the at least one LED element can be mirrored.

[0020] The emitter according to claim 4 ensures a direct and efficient cooling while maintaining a high light output. The adjacent arrangement of the at least one cooling channel to the at least one LED element also has the advantage that light that is laterally emitted from the at least one LED element can be efficiently redirected. The at least one cooling channel can be arranged in a plane formed by the substrate surface that is directly adjacent or spaced-adjacent to the at least one LED element. In particular, the at least one cooling channel is arranged directly on the substrate surface.

[0021] Preferably, the at least one cooling channel has no overlap with the at least one LED element perpendicular to the substrate surface. Particularly preferably, the at least one cooling channel has no overlap with the at least one LED element in the main emission direction. Light that is emitted perpendicular to the substrate surface, in particular light that is emitted in the main emission direction, does not suffer any attenuation and / or redirection due to the at least one cooling channel. The yield of the light to be emitted is improved, in particular in the main emission direction.

[0022] The emitter according to claim 5 ensures an efficient cooling of the at least one LED element. Furthermore, a greater proportion of the light that can be generated by the at least one LED element can be redirected in a direction perpendicular to the substrate surface, in particular in the main emission direction. The bundling of the light is further improved. Here and in the following, "adjacent" is to be understood to mean that the at least one LED element is arranged directly to the at least one cooling channel arrangement or at a distance adjacent to the at least one cooling channel.

[0023] Preferably, the at least one LED element is adjacent to the at least one cooling channel on at least three sides, in particular on all sides, in a plane delimited by the substrate surface. Particularly preferably, the at least one LED element is completely surrounded by the at least one cooling channel in a plane delimited by the first substrate surface. The same cooling channel, for example a cooling channel that is curved around the at least one LED element, can be adjacent to different sides of the LED element. Alternatively, different cooling channels can be adjacent to the at least one LED element on different sides.

[0024] The emitter according to claim 6 has a high light output and precisely defined emission characteristics. The region of the cooling channel boundary surface of the at least one cooling channel that extends away from the respective adjacent LED element delimits an open emission area or light cone that begins at the substrate surface.

[0025] The emitter according to claim 7 is stable and can be easily manufactured. The transparent encapsulation protects the at least one LED element and the at least one cooling channel. Damage is avoided. The encapsulation in particular has an emission surface at which the light to be emitted by the emitter exits. The emission surface in particular is formed parallel to the substrate surface. The emission surface in particular is perpendicular to the main emission direction.

[0026] The emitter according to claim 8 can be easily and flexibly manufactured. The geometry, in particular the cross section, of the cooling channel can be flexibly determined. The cooling channel formed as a cavity in the encapsulation in particular does not have an additional cooling channel housing, in particular no separately formed cooling channel side wall. The heat is in particular transferred directly from the at least one LED element to the coolant in the cooling channel via the encapsulation. The cooling effect is improved.

[0027] The emitter according to claim 9 is low-cost and easy to manufacture. The resin, in particular the epoxy resin and / or the silicone elastomer, can be easily applied and cured. The geometry of the encapsulation, in particular the shape of the emission surface, is advantageously easily and flexibly adapted to the respective requirements, in particular the desired lamp shape.

[0028] The emitter according to claim 10 ensures an efficient redirection of at least a portion of the light. Due to the refractive index n EThe refractive index n of the transparent encapsulation is greater than the refractive index of the cooling channel K The encapsulation is thus a higher optical density medium than the cooling channel. As a result, total reflection can be achieved, in which the higher optical density medium of the encapsulation merges into the cooling channel. For this reason, at least a portion of the light can be reflected efficiently at the cooling channel boundary surface without the need for a mirror of the cooling channel boundary surface. Thereby, reflection can be achieved without limiting the heat transfer of the cooling channel boundary surface.

[0029] The refractive index of the cooling channel can be predetermined by a cooling channel housing of the cooling channel. If no cooling channel housing is present, in particular if the at least one cooling channel is formed as a cavity in the encapsulation, the refractive index of the cooling channel in particular corresponds to the refractive index of the coolant, in particular the coolant liquid. An exemplary coolant contains water with a refractive index of 1.33 and / or ethylene glycol with a refractive index of 1.43.

[0030] The refractive index n of the transparent encapsulation is greater than the refractive index of the cooling channel E greater than 1.33, in particular greater than 1.43, in particular greater than 1.45, in particular greater than 1.5. For example, the refractive index n of the encapsulation E may be in the range of 1.45 to 1.59, in particular in the range between 1.45 and 1.54. An exemplary epoxy resin sold under the trade name "Nitto Denko NT-8524" has a refractive index of 1.57. An exemplary silicone elastomer sold under the trade name "Dow Corning OE-6550" has a refractive index of 1.54.

[0031] The emitter according to claim 11 ensures that light incident on the cooling channel boundary surface of the at least one cooling channel is redirected efficiently. The angle d between the surface tangent of the region of the cooling channel boundary surface facing the at least one LED element and the first substrate surface determines the relative inclination of this region of the cooling channel boundary surface with respect to the light that can be generated by the LED element. Depending on the angle d, light emitted at an emission angle b with respect to the main emission direction is totally reflected at the cooling channel boundary surface. This is the case under the following conditions:

[0032]

[0033] Light emitted at an emission angle b with respect to the main emission direction defined as perpendicular to the first substrate surface is totally reflected at the cooling channel boundary surface. The greater the emission angle b, the smaller the angle d must be in order to ensure total reflection. For

[0034]

[0035] It is ensured that light emitted from the at least one LED element parallel to the substrate surface (b = 90°) is also totally reflected at the cooling channel boundary surface.

[0036] Preferably, the region of the cooling channel boundary surface facing the at least one LED element is planar, and particularly preferably the entire region facing the at least one LED element extends at an angle d to the surface. Where appropriate, the angle d describes the angle at which the entire region of the cooling channel boundary surface facing the at least one LED element extends relative to the substrate surface. The angle d is also referred to hereinafter as the base angle.

[0037] The emitter according to claim 12 ensures a controlled and reliable redirection of light. The polygonal cross section of the at least one cooling channel has a planar boundary surface region which enables an efficient redirection of light. Preferably, the cross section of the at least one cooling channel has the shape of a triangle, in particular an isosceles triangle. The base of the triangle is particularly preferably parallel to the plane formed by the substrate surface. In particular, the sides of the triangle extend away from the substrate surface. Particularly preferably, the sides of the triangular cross section of the cooling channel extend at a base angle d to the substrate surface which meets the condition of formula (2).

[0038] Alternatively, the at least one cooling channel can have a curved cooling channel boundary surface region. For example, the at least one cooling channel can have a convexly curved cooling channel boundary surface region, in particular a dome shape. Preferably, the at least one cooling channel has a concavely curved cooling channel boundary surface region, in particular a concave side. The cross section of the at least one cooling channel can be lenticular at least in regions. This enables a particularly good bundling of light.

[0039] The emitter according to claim 13 ensures an efficient bundling of light. The extension of the cooling channel perpendicular to the substrate surface is also referred to hereinafter as the height of the cooling channel. As the height of the cooling channel increases, in particular when the width measured in the direction of the substrate surface remains constant while the height of the cooling channel increases, the light cone of the light to be emitted by the emitter decreases. The height of the cooling channel can thus be used to adapt the emission characteristics.

[0040] In general, the emission characteristics can depend on the height of the cooling channel, the width of the cooling channel, the extension of the at least one LED element measured in the direction of the substrate surface and / or the distance between the LED element and the adjacent cooling channel measured in the direction of the substrate surface. In order to adapt the emission characteristics to the respective requirements, in particular to optimize the bundling, the above-mentioned parameters can be varied and matched to one another.

[0041] The emitter according to claim 14 has an efficient cooling system. Glycol has proven to be an effective coolant. Glycol has a wide temperature range when it is a liquid.

[0042] It is another object of the present application to improve a method for emitting light, in particular a method for emitting light efficiently and simply.

[0043] The object is achieved by a method comprising the steps according to claim 15. First, an emitter is provided. The provided emitter comprises a substrate having a substrate surface, at least one LED element arranged on the substrate surface for generating light in a visible light frequency range to be emitted, and an active cooling unit for cooling the at least one LED element. The active cooling unit has at least one cooling channel for a coolant, which cooling channel is arranged in a beam path of at least a portion of the light to be emitted, which can be generated by the at least one LED element. The light to be emitted is generated in the visible light frequency range by the at least one LED element. The at least one LED element is cooled by the active cooling unit. At least a portion of the light to be emitted is redirected by the at least one cooling channel. The advantages of the method correspond to the advantages of the above-described emitter. The provided emitter can particularly comprise one or more features described above in connection with the emitter.

[0044] The method according to claim 16 enables an efficient and directional redirection, in particular a bunching, of the light to be emitted by the emitter.

[0045] The method according to claim 17 ensures an efficient redirection of at least a portion of the light to be deflected. In particular, when the light is totally reflected at the cooling channel boundary surface of the at least one cooling channel, the light is not absorbed or transmitted into the cooling channel. The light is not subject to any attenuation of the cooling channel. The intensity of the light emitted by the emitter is enhanced. BRIEF DESCRIPTION OF DRAWINGS

[0046] Further features, advantages and details of the present application will become apparent from the following description of several embodiments, wherein:

[0047] Figure 1 a top view of a first embodiment showing a schematic illustration of a luminaire having a plurality of LED light sources and an active cooling unit;

[0048] Figure 2 a sectional view showing the luminaire according to Figure 1 taken along the section line II-II;

[0049] Figure 3 a detail III showing the sectional view according to Figure 2 ;

[0050] Figure 4 a schematic flow chart showing a method of operation of the luminaire according to Figure 1 ;

[0051] Figure 5 a schematic illustration of a luminaire according toFigure 1 a schematic illustration of the emission characteristics of a luminaire of the lamp;

[0052] Figure 6 a cross-sectional view showing a second embodiment of a luminaire; and

[0053] Figure 7 a cross-sectional view showing a third embodiment of a luminaire. DETAILED DESCRIPTION

[0054] In Figures 1 to 3 a first embodiment of an emitter in the form of a luminaire 1 is shown. The luminaire 1 has a substrate 2 with a first substrate surface 3 and a second substrate surface 4 that is spaced apart from the first substrate surface 3 by a substrate thickness. A plurality of LED elements in the form of LED light emitting devices 5 is arranged on the first substrate surface 3. The luminaire 1 further comprises an active cooling unit 6 with a network of cooling channels 7 arranged on the first substrate surface 3.

[0055] In the illustrated embodiment, six LED light emitting devices 5 are arranged on the first substrate surface 3. The LED light emitting devices 5 are arranged on the first substrate surface 3 in the form of a 3x2 regular grid of LED light emitting devices 5. The number and arrangement of LED light emitting devices is not essential and can vary according to embodiment examples.

[0056] The LED light emitting devices 5 serve to generate visible light that is emitted by the luminaire 1. The light that can be generated by the LED light emitting devices 5 is electromagnetic radiation in the visible light range. This means that the light generated by the LED light emitting devices 5 has a frequency or a wavelength in the frequency range or wavelength range of visible light. The LED light emitting devices 5 are LED chips.

[0057] Heat is generated in the process of generating light by the LED light emitting devices 5. The active cooling unit 6 serves to cool the LED light emitting devices 5. For this purpose, a coolant 8 is conveyed in the cooling channels 7. The coolant 8 takes the form of a cooling liquid, which is schematically shown in Figure 1 and Figure 2 . The coolant 8 flows in the cooling channels 7 in a flow direction that is symbolically indicated by the arrows 9 in Figure 1 . In order to pump or convey the coolant 8 in the cooling channels 7, the luminaire 1 has a pump 10. The pump 10 is schematically shown in Figure 1 and is connected to the cooling channels 7 via a fluidic connection 11 that is also shown schematically. In the illustrated embodiment, the pump 10 is arranged on the first substrate surface 3. In further embodiments that are not shown, the pump 10 is directly integrated into the network of cooling channels 7. In yet further embodiments that are not shown, the pump 10 is arranged in the area of the second substrate surface 4 or independently of the substrate 2. In particular, the fluidic connection 11 can pass through the substrate 2 or be remote therefrom.

[0058] The cooling channel 7 is arranged on the first substrate surface 3. The cooling channel 7 is arranged in the plane formed by the first substrate surface 3 adjacent to the LED light emitting device 5. The cooling channel 7 is circumferentially adjacent to the LED light emitting device 5. The cooling channel 7 is circumferentially arranged on all four sides of the LED light emitting device 5. In the plane formed by the first substrate surface 3, the cooling channel 7 circumferentially surrounds the respective LED light emitting device 5. Arranging the cooling channel 7 on the same substrate surface as the LED light emitting device 5, i.e. on the first substrate surface 3, has in particular the advantage that the cooling of the LED light emitting device 5 is directly performed and not through the substrate 2. This ensures that the active cooling unit 6 particularly efficiently cools the LED light emitting device 5.

[0059] The LED light emitting device 5 as well as the cooling channel 7 are embedded in the transparent encapsulation 12. The cooling channel 7 is formed as a cavity in the encapsulation 12. Thus, the cooling channel 7 does not have any additional cooling channel enclosure. This facilitates the manufacturing of the cooling channel 7. The geometry of the cooling channel 7, in particular their cross section, can be flexibly determined.

[0060] The encapsulation 12 defines an emission surface 13 opposite the first substrate surface 3 with respect to the LED light emitting device 5. The light generated by the LED light emitting device 5 is emitted from the emission surface 13 of the luminaire 1. In the shown embodiment, the emission surface 13 is planar and parallel to the first substrate surface 3. In other embodiments, not shown, the emission surface can also have a different position relative to the first substrate surface and / or a different shape.

[0061] In Figure 2 A cross section of the cooling channel 7 of the luminaire 1 is shown in Fig. 1. The cooling channel 7 has a cross section in the form of an isosceles triangle. The base of the triangle lies in the plane formed by the first substrate surface 3. The sides of the isosceles triangle extend with a base angle d from the first substrate surface 3 to the emission surface 13. The plane bounded by the sides of the isosceles triangle has a surface normal 16 and a surface tangent 17. The surface tangent 17 is parallel to the plane of the respective side. Thus, the base angle d is defined as the angle at which the surface tangent 17 extends relative to the first substrate surface 3. The cooling channel 7 has a height H in a direction perpendicular to the first substrate surface 3.

[0062] The cooling channel 7 has a cooling channel boundary surface 14 to the encapsulation 12. In the shown embodiment, in which the cooling channel 7 is formed by a cavity in the encapsulation 12, the cooling channel boundary surface 14 is formed by the transition between the encapsulation 12 and the coolant 8. In other embodiments, not shown, the cooling channel boundary surface 14 can also be formed by a cooling channel housing.

[0063] The cooling channel boundary surface 14 extends along the sides of the triangular cross section of the cooling channel 7. As Figure 2 As can be seen in Figure 2 , the region of the cooling channel boundary surface 14 facing one of the LED light emitting devices 5 extends away from the respective adjacent LED light emitting device 5 with increasing distance from the first substrate surface 3. In other words, the distance of the cooling channel boundary surface 14 from the respective adjacent LED light emitting device 5, measured in the plane of the first substrate surface 3, increases with increasing distance perpendicular to the first substrate surface 3. Thereby, the cooling channel 7, in particular its cooling channel boundary surface 14, delimits a light cone for the light generated by the LED light emitting devices 5 that opens from the first substrate surface 3 towards the light emitting surface 13.

[0064] With reference to Figure 2 and Figure 3 , the light emission through the luminaire 1 will be described in the following. Due to the arrangement of the cooling channel 7, a concentration of the light generated by the LED light emitting devices 5 can be achieved.

[0065] A main emission direction 15 is defined perpendicular to the first substrate surface 3. In the shown embodiment, the main emission direction 15 is perpendicular to the emission surface 13. The LED light emitting devices 5 generate light that is emitted by the LED light emitting devices 5 over the entire solid angle of 2p size above the first substrate surface 3. Figure 2 The arrows in Figure 2 indicate exemplary light beams S i that can be generated by the LED light emitting devices 5 shown in the middle, wherein i = 1, 2, 3, 4.

[0066] The cooling channel 7 does not overlap with the LED light emitting devices 5 in the direction of the main emission direction 15. Thus, the cooling channel 7 is not arranged on the light beam path of the light beams that extend in the direction of the main emission direction 15 in general. In the light beam paths shown by way of example in Figure 2 , the light beams S1, S2, S3 do not impinge on the cooling channel 7. The light beams S1, S2, S3 directly reach the emission surface 13 and are emitted from there into the environment of the luminaire 1. However, the cooling channel 7 is arranged on the light beam path of at least a portion of the light generated by at least one of the LED light emitting devices 5. In the light beams shown by way of example in Figure 2 , the light beam S4 impinges on the cooling channel boundary surface 14 of the cooling channel 7 shown on the right-hand side of Figure 2 adjacent to the LED light emitting device 5 shown in the middle. The light beam S4 is reflected at the cooling channel boundary surface 14 in the direction of the emission surface 13. The reflected light beam is drawn as light beam S'4 in Figure 2 and Figure 3 . The light impinging on the cooling channel 7 is redirected at the cooling channel boundary surface 14. The redirection is described in detail in the following with reference to Figure 3 .

[0067] The light beam S4 has an emission angle b with respect to the main emission direction 15. The light beam angle b is typically between 0° and 90°. The light beam S4 has an incidence angle c with respect to the surface normal 16 of the cooling channel boundary surface 14 when impinging on the cooling channel boundary surface 14. The reflected light beam S'4 has a reflection angle c' with respect to the surface normal 16, wherein the reflection angle c' is equal in magnitude to the incidence angle c. The angle between the reflected light beam S'4 and the main emission direction 15 is indicated by b'. Due to the reflection at the cooling channel boundary surface 14 extending away from the LED light emitting device 5, the following condition applies to the angle b': 0° < b' < b. Due to the reflection at the cooling channel boundary surface 14, the angle b' of the reflected light beam S'4 with respect to the main emission direction 15 is reduced compared to the emission angle b of the light beam S4. The light reflected at the cooling channel boundary surface 14 is deflected in the direction of the emission direction 15. The cooling channel 7 redirects and concentrates the light generated by the LED light emitting device 5 in the main emission direction 15. The light intensity in the direction of the main emission direction 15 is increased.

[0068] Thereby, when electromagnetic radiation impinges on the boundary surface, it is not only reflected, but also partly transmitted through the boundary surface. Thus, in Figure 3 the light beam S4 impinging on the cooling channel boundary surface 14 is also indicated as a transmitted light beam of the light beam S4 impinging on the cooling channel boundary surface 14. The transmitted light beam has a transmission angle with respect to the surface normal 16. The transmission angle is determined according to Snell's law, according to which

[0069]

[0070] wherein n E is the refractive index of the package 12 and n K is the refractive index of the coolant 8. Since the refractive index n E of the package 12 is greater than the refractive index n K of the coolant 8, the transmission angle is greater than the incidence angle c. By reducing, especially avoiding, the transmitted light beam, the light intensity in the main emission direction 15 can be increased. For this purpose, the luminaire 1 makes use of the total reflection effect that occurs at a certain incidence angle c when passing from an optically dense medium to an optically less dense medium, i.e. from a medium with a greater refractive index to a medium with a smaller refractive index. In the case of total reflection, this angle is . Thus, depending on the refractive index of the package 12 or the cooling medium 8, the condition for the incidence angle C at which total reflection occurs is:

[0071]

[0072] The incidence angle c depends on the emission angle b and the base angle d. The smaller the emission angle b, the larger the incidence angle c. In the shown embodiment, the base angle d is chosen such that the incidence angle c promotes total reflection, regardless of the emission angle b, in particular also for an emission angle b = 90°. Thus, for the base angle d, the following condition applies:

[0073]

[0074] In the shown embodiment, the refractive index of the transparent encapsulation 12 is between 1.45 and 1.59. In the shown embodiment, an epoxy resin is used for the transparent encapsulation 12. For example, the epoxy resin used for the encapsulation is an epoxy resin sold under the trade name "Nitto Denko NT-8524", which has a refractive index of 1.57.

[0075] A variety of fluids, in particular liquids, can be used as the coolant 8. An exemplary coolant is ethylene glycol, which has a refractive index of 1.43. For n E = 1.57 and n K = 1.43, the result for the base angle d that ensures total reflection independent of the emission angle b according to equation (5) is as follows: d < 21.7°. An alternative coolant is water, which has a refractive index of 1.33. In this case, the result for the base angle d that ensures total internal reflection independent of the light beam angle b is as follows: d < 32°.

[0076] In an alternative embodiment, not shown, the transparent encapsulation is made of a silicone elastomer. An exemplary silicone elastomer sold under the trade name "Dow Corning OE-6550" has a refractive index of 1.54.

[0077] The cooling channel 7 has a height H perpendicular to the first substrate surface 3 and thus in the main emission direction 15. The height H depends on the width B of the base of the triangular cross section of the cooling channel 7 and on the base angle d. The height H increases when the base angle d increases and / or when the width B increases. When the height increases, a larger proportion of the light generated by the LED light device 5 impinges on the cooling channel boundary surface 14 and is redirected there. Thus, the collimation effect promoted by the cooling channel 7 depends on the height H and the base angle d of the cross section of the cooling channel 7. Thus, the light intensity and the collimation of the light emitted by the luminaire 1 along the main emission direction 15 can be adjusted by the geometry of the cooling channel 7. The height H is for example between 1 mm and 20 mm, in particular between 1 mm and 15 mm, preferably approximately 10 mm. The width of the cooling channel 7 is for example between 5 mm and 50 mm, in particular between 5 mm and 40 mm, preferably approximately 20 mm. The base angle d is for example between 0° and 90°, in particular between 10° and 80°, in particular between 15° and 45°, preferably approximately 35°.

[0078] Other parameters for influencing the emission characteristic are an extension L of the LED light emitting device 5 measured in the direction of the first substrate surface 3 and a distance A between the cooling channel 7 and the LED light emitting device 5 measured in the direction of the first substrate surface 3 (see Fig. 2). Figure 2 ). The distance A can for example be between 0 mm and 5 mm, in particular between 0.5 mm and 2 mm, in particular about 1 mm. At a distance A = 0 mm, the LED light emitting device 5 and the cooling channel 7 are arranged directly adjacent to each other on the first substrate surface 3. An exemplary extension L of the LED light emitting device 5 can be between 0.1 mm and 5 mm, in particular between 0.2 mm and 2 mm, in particular about 1 mm. In an exemplary embodiment, the extension of the LED light emitting device 5 is about 1 mm and in each case the distance between the LED light emitting device 5 and the adjacent cooling channel 7 is 1 mm. In an exemplary embodiment, the base angle d = 35°, the height H = 7.5 mm and the width B = 21 mm.

[0079] In Figure 4 , a sequence of a method of operation 20 of the luminaire 1 is schematically shown. In a providing step 21, the luminaire 1 is provided.

[0080] The providing step 21 is followed by an emitting step 22. In the emitting step 22, light is emitted by the luminaire 1. In a light generating step 23, light to be emitted is generated by the LED light emitting device 5. The light generated by the LED light emitting device 5 is in the visible light range. In a redirecting step 24, at least a portion of the light generated by the LED light emitting device 5 is redirected by the cooling channel 7. In this process, the light is reflected at the cooling channel boundary surface 14, in particular totally reflected.

[0081] In a cooling step 25, the LED light emitting device 5 is cooled by the active cooling unit 6. Here, the coolant 8 is pumped through the cooling channel 7 by the pump 10.

[0082] Figure 5 The emission characteristic 27 of the luminaire 1 is schematically shown. The intensity I of the light generated by the LED light emitting device varies with the beam angle b. For determining the emission characteristic 27, the intensity Imax normalized to the maximum intensity I is applied by the emission angle b. The emission characteristic 27 is illustrated as a dashed line. For comparison, a reference emission characteristic 28 is also schematically shown as Figure 5The reference radiation characteristic 28 corresponds to the emission characteristic of a reference luminaire similar to the luminaire 1 except that the luminaire 1 does not have cooling channels 7 on the first substrate surface 3. In a reference luminaire whose structure corresponds to the structure of a commercially available LED lamp, no part of the light generated by the LED light emitting device is redirected at the cooling channels. The comparison of the light emission characteristic 27 with the reference emission characteristic 28 clearly shows that due to the redirection of a part of the light generated by the LED light emitting device 5 at the cooling channels 7, the light is bunched around the main emission direction 15 with b = 0°. In particular, the light emission characteristic 27 has an increased intensity I for small values of the emission angle b compared to the reference emission characteristic 28. For larger values of the emission angle b, in particular in the range close to 90° or -90°, the intensity I of the light emission characteristic 27 is reduced compared to the reference emission characteristic 28.

[0083] In further embodiments, not shown, the ratio of the base angle d and / or the refractive index n K / n E is chosen such that the condition in equation (5) is not fulfilled. Thus, total reflection cannot be guaranteed for all beam angles b. In such embodiments, total reflection occurs only for light beams with beam angles b

[0084]

[0085] In further embodiments, the cooling channels 7 have a different cross-sectional geometry. For example, the cooling channels 7 have a polygonal cross-section. The polygonal cross-section has the advantage of planar areas of the cooling channel boundary surface 14, thereby ensuring a controlled redirection of light incident thereon.

[0086] Figure 6 An alternative embodiment of a luminaire la is shown. Components already described in connection with the embodiment of the luminaire 1 have the same reference numerals. Components that are structurally different but functionally identical have the same reference numerals and are followed by a. Figures 1 to 3

[0087] The luminaire la differs from the luminaire 1 shown in Figures 1 to 3 only in the geometry of the cooling channels 7a. The cooling channels 7a have a dome-like cross-section. For the dome-like cross-section of the cooling channels 7a, a large height Ha can be achieved even if the width Ba of the cooling channels 7a is small. The dome-shaped cross-section has two sides that extend away from the first substrate surface 3 in a substantially straight line. At the end away from the first substrate surface 3, the cooling channels 7a have a rounded tip.

[0088] The luminaire la differs from the luminaire 1 shown in Figure 3 ​The triangular cross section of the cooling channel 7 shown has a uniform base angle d in comparison. The cooling channel boundary surface 14a does not have a uniform base angle d in comparison. Therefore, the base angle d is defined in a region as the angle under which a surface tangent 17a of the respective region of the cooling channel boundary surface 14a extends with respect to the first substrate surface 3.

[0089] In a region of the tip of the cooling channel 7a, the base angle d is small enough to satisfy the equation (5). In this region, the angle of incidence c with respect to the surface normal 16a is large enough to produce total reflection as shown by the exemplary light beam S5 in Figure 6 .

[0090] In Figure 7 , a further alternative embodiment of the luminaire 1b is shown. Components that have already been described in connection with the embodiment of the luminaire 1a of Figures 1 to 3 have the same reference signs. Components that are structurally different but functionally identical have the same reference signs and are followed by b.

[0091] The luminaire 1b differs from the luminaire 1 shown in Figures 1 to 3 or the luminaire 1a shown in Figure 6 only in the geometry of the cooling channel 7b. The cooling channel 7b has a wedge-shaped cross section. The region of the cooling channel boundary surface 14b facing the LED light emitting device 5 has a concave curvature. Overall, the cooling channel 7b thus has a generally lens-shaped cross section. Due to the concave curvature of the region of the cooling channel boundary surface 14b facing the LED light emitting device 5, the base angle d decreases with the distance from the first substrate surface 3. This ensures that light beams with a large beam angle b are incident on a region of the cooling channel boundary surface 14b with a small base angle d. This can efficiently ensure the conditions for total reflection at the cooling channel boundary surface 14b. The cooling channel 7b enables particularly efficient bundling of the light generated by the LED light emitting device 5. In Figure 7 , an exemplary light beam S6 is shown that is totally reflected at the cooling channel boundary surface 14b.

[0092] In order to improve the reflection of the light beams at the cooling channel, in further embodiments not shown, a reflective layer is provided at the cooling channel boundary surface. In some embodiments, for this purpose, the cooling channel boundary surface is coated with a reflective material. In still further embodiments, these cooling channels comprise a cooling channel housing with a reflective surface. For example in the case of the cross-sectional shape of the cooling channel 7a shown in Figure 6 , a reflective layer is particularly advantageous when the base angle d does not satisfy the condition of the equation (5) for all regions of the cooling channel boundary surface facing the respective adjacent LED light emitting device 5.

[0093] Alternative embodiments relate to emitters for emitting infrared light or UV light. These emitters can be designed similar to the above described luminaire, wherein the corresponding LED elements are designed to generate infrared light or UV light, respectively. The light to be emitted is at least partially redirected by the respective cooling channel without causing a change in frequency.

Claims

1. An emitter for emitting light, comprising - a substrate (2) having a substrate surface (3), - at least one LED element (5) arranged on the substrate surface (3) for generating light to be emitted, and - an active cooling unit (6) for cooling the at least one LED element (5) with at least one cooling channel (7; 7a; 7b) containing a coolant (8) therein, wherein the at least one cooling channel (7; 7a; 7b) being arranged on a beam path (S4; S5; S6) of at least a portion of the light to be emitted for redirecting the light to be emitted, the light to be emitted being generatable by the at least one LED element (5), wherein the light to be emitted is redirected without changing a frequency of the light to be emitted, wherein the at least one LED element (5) and the at least one cooling channel (7; 7a; 7b) are embedded in a transparent encapsulation (12), wherein the refractive index n of the transparent encapsulation (12) E is greater than the refractive index n of the at least one cooling channel (7; 7a; 7b) K , wherein a surface tangent (17; 17a; 17b) of a cooling channel boundary surface (14; 14a; 14b) of the at least one cooling channel (7; 7a; 7b) facing an area of the at least one LED element (5) is angled with respect to the substrate surface (3) by an angle d, wherein the following equation applies: d < 90° - sin -1 (n K / n E ).

2. The emitter according to claim 1, characterized in that at least a portion of the light to be emitted is redirectable by the at least one cooling channel (7; 7a; 7b) in a direction of a predetermined main emission direction (15).

3. The emitter according to claim 1, characterized in that at least a portion of the light to be emitted is redirectable by the at least one cooling channel (7; 7a; 7b) in a main emission direction (15) defined as perpendicular to the substrate surface (3).

4. The emitter according to claim 1, characterized in that a cooling channel boundary surface (14; 14a; 14b) of the at least one cooling channel (7; 7a; 7b) is formed at least in several areas in such a way that at least a portion of the light to be emitted is reflected at the cooling channel boundary surface (14; 14a; 14b).

5. The emitter according to claim 1, characterized in that the at least one cooling channel (7; 7a; 7b) is arranged adjacent to the at least one LED element (5) in a plane formed by the substrate surface (3).

6. The emitter according to claim 5, characterized in that the at least one LED element (5) adjoins the at least one cooling channel (7; 7a; 7b) on at least two sides in the plane delimited by the substrate surface (3).

7. The emitter according to any one of claims 5 to 6, characterized in that The area of the cooling channel boundary surface (14; 14a; 14b) of the at least one cooling channel (7; 7a; 7b) facing the respective adjacent LED element (5) extends away from the adjacent LED element (5) as the distance from the substrate surface (3) increases.

8. The emitter according to claim 1, characterized in that The at least one cooling channel (7; 7a; 7b) is formed as a cavity in the encapsulation (12).

9. The emitter according to any one of claims 1 or 8, characterized in that The encapsulation (12) comprises an organic silicone elastomer and / or a resin.

10. The emitter according to claim 9, characterized in that The organic silicone elastomer and / or the resin is an epoxy resin.

11. The emitter according to claim 1, characterized in that The at least one cooling channel (7) has a polygonal cross section.

12. The emitter according to claim 11, characterized in that The cross section is triangular.

13. The emitter according to claim 1, characterized in that The at least one cooling channel (7; 7a; 7b) has an extension perpendicular to the substrate surface (3) of between 1 mm and 20 mm.

14. The emitter according to claim 13, characterized in that The extension is between 1 mm and 15 mm.

15. The emitter according to claim 1, characterized in that The at least one cooling channel (7; 7a; 7b) contains a coolant (8) comprising ethylene glycol.

16. A method of emitting light by an emitter, comprising the following steps: - providing an emitter (1; 1a; 1b) having -- a substrate (2) having a substrate surface (3), -- at least one LED element (5) arranged on the substrate surface (3) for generating light to be emitted, and -- an active cooling unit (6) for cooling the at least one LED element (5) with at least one cooling channel (7; 7a; 7b) containing a coolant (8), wherein the at least one cooling channel (7; 7a; 7b) is arranged on a beam path (S4; S5; S6) of the light to be emitted, which can be generated by the at least one LED element (5), - generating the light to be emitted by the at least one LED element (5), - cooling the at least one LED element (5) by the active cooling unit (6), and - redirecting at least a portion of the light to be emitted by the at least one cooling channel (7; 7a; 7b), wherein the redirection of the light to be emitted takes place without changing the frequency of the light to be emitted, wherein the at least one LED element (5) and the at least one cooling channel (7; 7a; 7b) are embedded in a transparent encapsulation (12), wherein the refractive index n of the transparent encapsulation (12) E is greater than the refractive index n of the cooling channel (7; 7a; 7b) K , wherein a surface tangent (17; 17a; 17b) of a region of the cooling channel boundary surface (14; 14a; 14b) of the at least one cooling channel (7; 7a; 7b) facing the at least one LED element (5) is angled with respect to the substrate surface (3) by an angle d, wherein the following equation applies: d < 90° - sin -1 (n K / n E ), wherein a redirection of at least a portion of the light to be emitted occurs by total reflection at the cooling channel boundary surface (14; 14a; 14b) of the at least one cooling channel (7; 7a; 7b).

17. The method according to claim 16, characterized in that at least a portion of the light to be emitted is redirected by the at least one cooling channel (7; 7a; 7b) in the direction of a predetermined main emission direction (15), in particular in the direction of a main emission direction (15) defined perpendicular to the substrate surface (3).

18. The method according to claim 16, characterized in that at least a portion of the light to be emitted is redirected by the at least one cooling channel (7; 7a; 7b) in the direction of a main emission direction (15) defined perpendicular to the substrate surface (3).

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