EP2587132B1 - Reflector for semiconductor light sources - Google Patents

Description

The invention relates to a reflector for semiconductor light sources, in particular for a downlight, according to the preamble of claim 1.

Generic reflectors are conventionally used in modules for semiconductor light sources, in particular for illuminants such as downlight emitters, in order to increase the quality of the light emitted by corresponding light sources. As a light source, for example, LED modules or high-pressure discharge lamps are used. It is a known problem that the light emitted by semiconductor light sources has to be processed so that illumination that is pleasant for the user can be generated by the light sources in which the semiconductor light sources are used. For example, both the light color and the luminance distribution in semiconductor light sources are usually inhomogeneous over the aperture angle of the light beam emitted by the light source. Therefore, in light sources, such as a downlight emitter, a light mixing of the emitted light from the semiconductor light source must be done so that a homogeneous light beam is generated with which a pleasant lighting can be achieved. It is usually desirable that a bundled beam is emitted from the illuminant for illumination, with a beam depending on the field of application a certain width can be advantageous.

A conventional measure to achieve a light mixing of the light emitted by a semiconductor light source in a light source and thus to produce a homogeneous beam, is that on the semiconductor light source, an optical medium, such as a light-diffusing or microfacetted hemisphere is placed. Also, scattering disks are partially arranged in the vicinity of the semiconductor light source in order to achieve such a light mixing in the lighting means. However, all of these measures have the disadvantage that high efficiency losses occur through additional absorption in the corresponding optical media to ensure the light scattering or light mixing.

Furthermore, reflectors are used in conventional bulbs with semiconductor light sources, with which a light mixing is to be achieved. Such reflectors conventionally have an inner space bounded by a reflector wall, within which a light source point is provided, on which a center of an emitting surface of one or more light sources can be arranged in the reflector. The reflector has a longitudinal direction and a transverse direction, wherein the light source point is arranged in the inner space such that the reflector wall circumferentially surrounds the light source point in the transverse direction. At one longitudinal end, the reflector has a light exit side, on which the interior is open and thus no reflector wall is arranged. Furthermore, the reflector wall has a recess through which a light source arranged in the reflector can be electrically contacted and fixed.

The light mixing takes place in conventional reflectors, characterized in that facets are arranged on the inside of the reflector wall facing the interior, which have a have reflective and curved in the longitudinal direction and / or in the transverse direction surface. Usually metal or metallized plastic is used in the production of the facets. In conventional reflectors, the facets are designed, for example, in the manner of spherical sections, so that they have a circular section as a cross section. However, the cross-section of the facets may, for example, also have the shape of a polygon. In this case, the essential characteristic of the facets used in conventional reflectors is that the facets have mutually inclined surface sections, so that a scattering of the incident light on the facet surface, in particular an expansion of the light beam, which occurs on the facet surface is ensured. For such facets, a radius of curvature can thus be assigned: the radius of curvature, for example, corresponds to the radius of the corresponding circle in the case of facets with a circular segment-shaped cross-section, and in the case of facets with a polygonal or polygon-segment-shaped cross-section to the radius of the circle enveloping the polygon. Further, it is from the closest prior art EP 1 632 713 A1 It is known to design a reflector such that it has facets whose curved surface has a radius of curvature in the longitudinal direction and a radius of curvature in the transverse direction, wherein the curvature of the facets, ie the radii of curvature, can be adjusted in a targeted manner to achieve a specific emission characteristic of the reflector, for example a variation of the radii of curvature as a function of the distance of the facet to the vertex of the reflector can also be provided. In order to obtain the highest possible efficiency and thus the highest possible light output from the light source for the illumination, conventional reflectors usually use facets with a highly reflective surface, so that the light absorption at the facets is negligible. However, it has turned out that the light mixing in conventional reflectors is insufficient. Accordingly, such reflectors are insufficient to provide a very homogeneous light beam without colored artifacts or disturbing light-dark areas for illumination. Although this is partly taken into account in conventional reflectors in that the facets have surfaces on which a diffuse reflection of light takes place, so that the light mixing is improved. However, due to the diffuse reflection, a considerable part of the light is scattered back into the reflector, resulting in lower system efficiency.

Moreover, it has turned out to be problematic in conventional reflectors that the light mixing in the reflector is achieved precisely by the expansion of the light beam emitted by the semiconductor light source via the scattering on the facet surfaces. Accordingly, light is emitted at a very large opening angle at the light exit side of the reflector, so that with conventional reflectors only insufficiently a beam of a certain width or with a certain opening angle can be generated.

Starting from the prior art, the invention has the object to provide a reflector for semiconductor light sources, by which the problems described above in conventional reflectors are at least partially resolved.

As a solution to the aforementioned technical problem, the invention proposes a reflector for semiconductor light sources with the features of claim 1.

According to the invention, the radius of curvature of the facets associated with the curvature in the longitudinal direction of the reflector varies, averaged over all facets, whose Surface center point has the same distance from the light source point, depending on this facet spacing. The curvature can also go to 0, whereby the radius of curvature can also strive towards infinity.

• Die Lichtquelle ist an dem Lichtquellenpunkt in dem Reflektor angeordnet und weist eine emittierende Fläche auf, von der aus Licht in den Innenraum des Reflektors emittiert wird. Die Fläche der Lichtquelle kann beispielsweise rechteckig, polygonförmig oder kreisförmig sein. Die Reflektorumwandung mit den Facetten umgibt die Lichtquelle in Querrichtung umfänglich und weist darüber hinaus eine Längserstreckung auf. Die Reflektorumwandung kann dabei beispielsweise einen rotationssymmetrischen Querschnitt aufweisen, es ist jedoch auch ein Querschnitt in anderer Form, wie beispielsweise quadratisch oder polygonförmig, möglich. Insbesondere kann der Querschnitt des Reflektors auch entlang der Längsrichtung des Reflektors variieren. Auch die Öffnung an der Lichtaustrittsseite des Reflektors kann beispielsweise rotationssymmetrisch, quadratisch oder polygonförmig sein.

The inventive design of the reflector makes it possible, as good as possible mixing of light in the reflector and at the same time the smallest possible opening angle of the to realize light emitted from the reflector at the light exit side. From the features of the reflector according to the invention, this results as follows:

• The light source is arranged at the light source point in the reflector and has an emitting surface, from which light is emitted into the interior of the reflector. The surface of the light source may be, for example, rectangular, polygonal or circular. The Reflektorumwandung with the facets surrounds the light source in the transverse direction circumferentially and also has a longitudinal extent. The reflector wall can, for example, have a rotationally symmetrical cross section, but it is also possible to have a cross section in another form, such as square or polygonal. In particular, the cross section of the reflector can also vary along the longitudinal direction of the reflector. The opening on the light exit side of the reflector may for example be rotationally symmetrical, square or polygonal.

From the emitting surface of the light source, the light rays at least partially reach the surfaces of the facets of the reflector wall. The angle τ, which a light beam, which comes from the emitting surface of the light source to a facet, forms with the longitudinal axis of the reflector, in each case depends on the facet spacing. Furthermore, this angle τ, especially for reflectors with non-rotationally symmetrical cross-section, also of the longitudinal distance of the facet, d. H. depending on the distance in the longitudinal direction of the facet to the emitting surface of the light source.

The incident on the facet surface light beam is then reflected by the facet surface, wherein the angle ψ, the reflected light beam with the The longitudinal axis of the reflector forms, depends on the angle τ and the inclination of the facet surface to the longitudinal axis of the reflector at the point where the light beam on the facet surface and is reflected by it depends.

For facets with a small radius of curvature in the longitudinal direction, d. H. with a strong surface curvature in the longitudinal direction, the angle ψ which the light beam reflected by the facet forms with the longitudinal axis of the reflector is highly dependent on the longitudinal position on the facet surface in which the light rays strike the facet surface. Two light beams which strike the facet surface with a small radius of curvature at approximately the same angle τ to the longitudinal axis of the reflector and impinge on the facet surface in the longitudinal direction are thus reflected at significantly different angles ψ from the facet surface.

It follows that over the radius of curvature of the facet, the expansion of the light beam incident on the facet can be influenced. The radius of curvature can be chosen to be positive or negative, the facet thus convex or concave, and the radius of curvature can be changed in its amount. This also includes a completely flat facet surface as the limit of a surface with a radius of curvature going towards infinity.

Depending on the angle τ that forms a light beam to the longitudinal axis of the reflector, however, an expansion of the light beam may just be desirable or not desirable. An expansion is desired as long as a mixing of the light in the reflector is to be achieved, without thereby the opening angle of the emerging from the light exit side of the reflector beam is too large. Accordingly, a Widening of the light beam on the facet surface may then be undesirable if the widening causes an excessively large opening angle of the radiation beam.

For example, a reflector according to the invention may be provided so that a light beam emitted from the emitting surface of the light source toward the facet is reflected at the facet surface and then emerges from the reflector at the light exit side. In this simple example, the angle ψ which the beam reflected by the facet surface forms with the longitudinal axis of the reflector is also the angle to the longitudinal axis of the reflector with which the beam emerges from the reflector. Accordingly, the angle ψ for all light rays emerging from the reflector must be less than half of the desired opening angle of the illuminant comprising the reflector. The inventive design of the reflector, the angle ψ can be effectively predetermined. Accordingly, in the reflector according to the invention, depending on the facet spacing, a small radius of curvature of the facet can be selected in order to realize high light mixing in the reflector, this being limited by the fact that the radius of curvature in FIG Depending on the facet spacing is varied. For adjusting the radius of curvature of the facets as a function of the facet spacing, the aperture angle of the beam emerging from the reflector can thus be adjusted.

It may be useful, especially for reflectors with rotationally symmetrical cross section, that all facets with the same facet spacing have an identical radius of curvature. However, it may also be useful, especially for reflectors with non-rotationally symmetrical cross section, that the radius of curvature of facets each having the same facet spacing varies with each other. Depending on the geometry of the reflector, such as reflector cross-section, reflector longitudinal section and facet size, a variation of the radius of curvature for facets with the same facet spacing in each case the best possible mixing of light with the most accurate setting of an opening angle possible. The mean value of the radius of curvature in the longitudinal direction of the facets with the same facet spacing varies in the reflector according to the invention as a function of the facet spacing.

According to the invention, the radius of curvature of the facets associated with the curvature in the transverse direction, averaged over all the facets whose center of the surface has the same distance in the transverse direction from the axis extending through the light source point in the longitudinal direction, varies as a function of this transverse spacing. The corresponding variation of the curvature in the transverse direction of the facets can ensure that the best possible mixing of light in the reflector is realized with respect to a reflection in the transverse direction at the same time as possible adjustable opening angle of emerging from the reflector beam. The transverse distance refers to the distance from the surface center of a facet to the longitudinal axis of the reflector, which passes through the center of the light-emitting surface of the light source in the reflector. Depending on the transverse distance of the facet, a stronger or weaker widening of a light beam incident on the facet in the transverse direction may be desired in order to realize the best possible light mixing in the reflector with simultaneously adjustable opening angle. The variation of the radius of curvature in the transverse direction of the facets can be effected analogously to the above-described variation of the radius of curvature in the longitudinal direction of the facets.

According to the invention, the radius of curvature of the facets associated with the curvature in the longitudinal direction increases with increasing facet spacing. As a result, with certain geometries of the reflector, an expansion of the opening angle can effectively be limited to a predetermined opening angle within a predetermined opening angle δ of the beam emerging from the reflector.

According to the invention, the curvature radius of the facet associated with the curvature in the transverse direction decreases with increasing transverse spacing. As a result, in certain reflector geometries, light mixing can be ensured by corresponding bulging of the facets in the transverse direction, while at the same time the opening angle of the beam emerging from the reflector can be effectively limited.

In addition, the reflector wall can be rotationally symmetrical about the longitudinal axis of the reflector. As a result, a symmetrical illumination by the beam emerging from the reflector and a homogeneous mixing of the light in the beam may be favored. In addition, due to the rotational symmetry, the manufacture of the reflector and the facets contained therein can be carried out in a particularly simple and cost-effective manner.

The reflector wall can also have a polygonal cross-section. This can be advantageous, for example, for the mixing of light in the reflector, since in a longitudinal plane of the reflector facets each have a different facet distance to the light source point, so that, for example, the radius of curvature in the transverse direction and / or the longitudinal direction of the facets can be varied in a longitudinal plane, without thereby the opening angle is increased, what for Light mixing may be advantageous.

In addition, all facets having the same facet spacing may have substantially the same radius of curvature with respect to the longitudinal bulge. This can be particularly advantageous for uniform light mixing and light intensity distribution in the beam emerging from the reflector.

Also, all facets having the same transverse distance may have the same radius of curvature with respect to the longitudinal curvature. This can be advantageous for a particularly homogeneous light mixing and light intensity distribution in the beam emerging from the reflector.

Furthermore, a light source may be arranged in the reflector so that the center of the emitting surface of a light source coincides with the light source point. The coincidence of the center of the emitting surface of the light source with the light source point enables a particularly precise realization of the light mixing with a simultaneously predetermined opening angle of the emerging from the reflector beam. For both facet spacing and transverse spacing are calculated with respect to the light source point in the reflector according to the invention, so that the advantages of the reflector according to the invention, which result from the fact that the radius of curvature of the facets is adjusted depending on the facet spacing and possibly also on the transverse distance, especially good.

The invention further relates to a radiator comprising a reflector according to the invention as described above. The radiator further comprises an electronic ballast and a light source, which is arranged in the reflector by means of a provided on the recess in the Reflektorumwandung mounting device so that the Center of the emitting surface of the light source coincides with the light source point. The light source is electrically coupled to the electronic ballast. By the radiator according to the invention, a light source is provided which is particularly well suited for lighting, since due to the successful light mixing in the reflector in the radiator by the radiator a pleasant light is generated and further provided by the radiator, a beam having a desired opening angle.

The invention is explained in more detail below by the description of embodiments with reference to the accompanying figures.

Figur 1:

eine Prinzipdarstellung eines erfindungsgemäßen Reflektors, in dem eine Lichtquelle angeordnet ist;

Figur 2:

eine schematische Darstellung des Öffnungswinkels δ der Lichtverteilung eines aus einem erfindungsgemäßen Reflektor ausgetretenen Strahlenbündels;

Figur 3:

eine Prinzipdarstellung eines Ausschnitts eines erfindungsgemäßen Reflektors;

Figur 4:

eine Prinzipdarstellung eines Ausschnitts eines erfindungsgemäßen Reflektors mit gewölbter Facette;

Figur 5:

eine Prinzipdarstellung eines Querschnitts eines erfindungsgemäßen Reflektors mit Lichtquelle.

It shows:

FIG. 1:

a schematic diagram of a reflector according to the invention, in which a light source is arranged;

FIG. 2:

a schematic representation of the opening angle δ of the light distribution of a leaked from a reflector according to the invention beam;

FIG. 3:

a schematic diagram of a section of a reflector according to the invention;

FIG. 4:

a schematic representation of a section of a reflector according to the invention with a curved facet;

FIG. 5:

a schematic diagram of a cross section of a reflector according to the invention with a light source.

In FIG. 1 is shown in a schematic diagram of the longitudinal section of a reflector 1 according to the invention. By doing illustrated embodiment, the light source 6 is arranged in the recess 7 of the reflector 1 so that the center of the emitting surface 8 of the light source 6 coincides with the light source point 5 of the reflector 1. The reflector wall 2 is rotationally symmetrical in the illustrated embodiment and has a circular cross section in each of its transverse planes as a cross section. The light-emitting surface 8 of the light source 6 faces the interior 3 of the reflector 1. In FIG. 1 For the sake of clarity, no facets are shown on the inside of the reflector wall 2 facing the interior 3. In the illustrated embodiment, the light exit side 4 of the reflector 1 of the light emitting surface 8 of the light source 6 is opposite.

In FIG. 2 is the opening angle δ of the light distribution in a beam emerging from a reflector 1 according to the invention at the light exit side 4, shown. It is in FIG. 2 the light intensity is shown as a function of the opening angle. Out FIG. 2 shows that from the reflector 1 according to the invention a beam emerges at the light exit side 4, which has a uniformly high light intensity over almost the entire opening angle δ. Through the mixing of light in a reflector 1 according to the invention, it is further ensured that the beam emerging from the reflector 1 over the entire opening angle δ has a homogeneous, pleasant to the viewer color.

In the FIGS. 3 to 5 the principle of a reflector 1 according to the invention is explained in more detail. For the sake of simplicity, it is assumed that a reflector 1, whose conversion 2 has a rotationally symmetrical cross section, and which is bell-shaped, wherein the reflector wall 2 is open at the light exit side 4 over the entire transverse extent. At the im Interior 3 facing inside of the Reflektorumwandung 2 facets 9 are arranged.

In FIG. 3 For example, a facet 9 is shown on the inside of the reflector wall 2. In the in FIG. 3 illustrated embodiment, the radius of curvature of the illustrated facet 9 is approximately infinite, so that the facet 9 is formed as a flat facet 9. Furthermore, the reflector 1 comprises FIG. 3 a light source 6, which has a diameter D and is also rotationally symmetrical. The center of the emitting surface 8 of the light source 6 coincides with the light source point 5. In FIG. 3 the angle γ is illustrated, which forms a light beam, which extends from the light source point 5 to the surface center of the facet 9, with the longitudinal axis of the reflector 1. The facet spacing corresponding to the distance between the surface center of the facet 9 and the light source point 5 is shown in FIG FIG. 3 marked with r. Furthermore, in FIG. 3 the angle α is defined, which defines the acute angle, the two beams form each other, which extend from a respective opposite transverse end of the emitting surface 8 from the surface center of the facet 9.

angenähert werden. Entsprechend kann der Krümmungswinkel β in Längsrichtung der Facette 9 über einfache geometrische Berechnungen in Abhängigkeit von dem Facettenabstand r ausgerückt werden. Somit kann auch der Krümmungsradius r_L der Facette 9 in Längsrichtung in Abhängigkeit von dem Facettenabstand r bestimmt werden. Falls α größer als δ ist, ist eine Wölbung der Facette 9 in Längsrichtung zu vermeiden und somit ein Krümmungsradius r_L gegen unendlich vorzusehen, so dass die Oberfläche der Facette 9 eben ausgestaltet ist.In the in FIG. 4 described embodiment, the dependence of the radius of curvature r _L in the longitudinal direction of the facet 9 is determined by the distance r as follows: It is assumed that a beam with the opening angle δ should emerge from the reflector 1 according to the invention. In order to achieve a light mixing, facets 9 with a curvature angle β, which corresponds to a radius of curvature r _L , are provided on the reflector wall 2. The curvature of the facet 9 refers to FIG. 4 on the longitudinal direction. It can be assumed that the angle of curvature β should not be greater than δ-α if the opening angle of the beam emerging from the reflector 1 should be limited to the angle δ. Accordingly, the angle of curvature β at a fixed δ of α depends. The angle α, however, is as out FIG. 3 , depending on the facet spacing r. For example, the angle α over the equation $\alpha =2\cdot \arctan \left[\frac{D\cdot \mathrm{cos\gamma }}{2\cdot r}\right]$

be approximated. Accordingly, the angle of curvature β in the longitudinal direction of the facet 9 can be disengaged via simple geometrical calculations as a function of the facet spacing r. Thus, the radius of curvature r _{L of} the facet 9 in the longitudinal direction can also be determined as a function of the facet spacing r. If α is greater than δ, curvature of the facet 9 in the longitudinal direction is to be avoided, and thus a radius of curvature r _L to be provided at infinity, so that the surface of the facet 9 is designed to be flat.

In FIG. 5 It is shown how the radius of curvature r _{Q of} the facet 9 in the transverse direction can be determined as an example depending on the transverse distance x between the surface center of the facet 9 and the light source point 5. In FIG. 5 the circular cross section of one of the described reflector 1 according to the invention is shown.

bestimmt werden. Entsprechend lässt sich durch einfache geometrische Berechnung eine Abhängigkeit des Krümmungswinkels ε und damit des Krümmungsradius r_Q in Querrichtung der Facette 9 von Querabstand x ermitteln. In dem angegebenen Ausführungsbeispiel ist eine Krümmung in Querrichtung der Facette 9 immer dann zu vermeiden, wenn der Winkel ϕ größer als der einzuhaltende Öffnungswinkel δ ist.It is assumed that the opening angle δ of the beam emerging from the reflector 1 according to the invention should not be increased by the curvature of the facet 9 in the transverse direction. For this purpose, it is assumed that the curvature angle ε in the transverse direction of the facet 9 should not be greater than δ - φ, where φ is the angle which two beams form with each other, from respective opposite transverse ends of the emitting surface 8 of the light source 6 to the surface center of the facet 9 are lost. Out FIG. 5 It can be seen that the angle φ depends on the transverse distance x. For example, the angle φ over the equation $\mathrm{\phi }=2\cdot \mathrm{<figure-callout\; id="2"\; label="arctan\; D"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">arctan\; </figure-callout>}\left[\frac{D}{}\right]\left[\frac{}{2\cdot x}\right]$

be determined. Accordingly, it can be explained by simple geometric Calculating a dependence of the curvature angle ε and thus the radius of curvature r _Q in the transverse direction of the facet 9 of transverse distance x determine. In the given embodiment, a curvature in the transverse direction of the facet 9 is always to be avoided if the angle φ is greater than the opening angle δ to be maintained.

By appropriate calculation of the radii of curvature in the longitudinal direction r _L and the radii of curvature in the transverse direction r _{Q of} the facets 9 in a reflector 1 according to the invention can be ensured that on the inside of the Reflektorumwandung 2 facets 9 are arranged with curved surfaces, so that a light mixing in the reflector 1 can take place. In this case, the calculation of the respective radii of curvature as a function of the facet spacing or the transverse spacing ensures that the facets 9 are arched only to such an extent that no widening of the opening angle of the beam emerging from the reflector 1 occurs beyond a predeterminable opening angle δ ,

LIST OF REFERENCE NUMBERS

1

reflector

2

Reflektorumwandung

3

inner space

4

Light output side

5

Light source point

6

light source

7

recess

8th

emitting area

9

facet

Claims (7)

1. Reflector (1) for semiconductor light sources, in particular for a downlight, said reflector comprising an inner space (3) delimited by a reflector surrounding wall (2) and a light exit side (4) that is arranged at a longitudinal end of the reflector (1) and on which the inner space (3) is open, wherein a light source point (5) is provided in the inner space (3) and in the transverse direction of the reflector being peripherally surrounded by the reflector surrounding wall (2), at which light source point a center of an emitting surface of a light source (6) in the reflector can be arranged, wherein the reflector surrounding wall (2) has a recess (7) through which the one light source (6) arranged in the reflector can be electrically contacted and fixed, wherein on the inner side of the reflector surrounding wall (2) facing the inner space (3) facets (9) are disposed that have a surface that is reflecting and curved in the longitudinal direction and/or transverse direction, wherein the radius of curvature of the facets (9) assigned to the curvature in the longitudinal direction, averaged over all the facets (9) the center of the surface thereof has the same distance from the light source point (5), varies as a function of this facet distance, wherein the radius of curvature of the facets (9) assigned to the curvature in the transverse direction, averaged over all the facets (9) the center of the surface thereof having the same distance, with regard to the transverse direction, from the axis running through the light source point in the longitudinal direction, varies as a function of this transverse distance, wherein the radius of curvature of the facets (9) assigned to the curvature in the longitudinal direction increases with an increasing facet distance, characterized in that the radius of curvature of the facets (9) assigned to the curvature in the transverse direction decreases with an increasing transverse distance.
2. Reflector according to claim 1, characterized in that the reflector surrounding wall (2) is rotationally symmetrical about the longitudinal axis of the reflector (1).
3. Reflector according to one of the claims 1 or 2, characterized in that the reflector surrounding wall (2) has a polygonal cross section.
4. Reflector according to any one of the preceding claims, characterized in that all the facets (9) with the same facet distance substantially have the same radius of curvature with respect to the curvature in the longitudinal direction.
5. Reflector according to any one of the preceding claims, characterized in that all the facets (9) with the same transverse distance have the same radius of curvature with respect to the curvature in the longitudinal direction.
6. Reflector according to any one of the preceding claims, characterized in that in the reflector (1), a light source (6) is arranged in such a manner that the center of the emitting surface of a light source (6) coincides with light source point (5).
7. Emitter, comprising a reflector (1) according to one of the claims 1 to 5, an electronic ballast as well as a light source (6) arranged in the reflector (1) by means of a mounting device provided at the recess (7) in the reflector surrounding wall (7), in such a manner that the center of the emitting surface of the light source (6) coincides with the light source point (5), wherein the light source (6) is electrically coupled with the electronic ballast.

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