DE102008011866B4 - Light source arrangement with a semiconductor light source - Google Patents

Abstract

A light source arrangement comprising a semiconductor light source, comprising: - a primary radiation source (110) having a layer sequence which in operation emits a first electromagnetic primary radiation along a first main radiation direction; a luminescence conversion element (120) spaced from the primary radiation source (110) and comprising a heat sink (121) and a luminescent material (122) arranged thereon, which wavelength-converts at least a portion of the coupled primary radiation by means of at least one phosphor into secondary radiation along a second main beam direction, - a wavelength-selective reflector element (160) which is arranged and embodied in the beam path of the primary radiation source (110) to direct the primary radiation to the luminescent material (122) of the luminescence conversion element (120) or to redirect secondary radiation emitted by the luminescent material (122) in the direction of the primary radiation source (110), and d- a second primary radiation source (130) emitting a third electromagnetic radiation, wherein the second primary radiation source (130) is disposed opposite the primary radiation source (110), and wherein the wavelength-selective reflector element (160) is configured to deflect the third electromagnetic radiation.

Description

The present invention relates to a light source arrangement with a semiconductor light source.

Semiconductor light sources are often used for lighting applications that require high luminance, such as projectors. With semiconductor light sources of different wavelengths, in turn, a white light can be generated.

The pamphlets US 2005/0270775 A1 . WO 2007/075661 A1 . US 7,234,820 B2 and US 2004/0150997 A1 show semiconductor light sources.

In some implementations, a semiconductor light source includes a primary radiation source and a luminescence conversion element to generate light having a different wavelength than that of the primary radiation source. Such a semiconductor light source is for example from the document US 6,066,861 known. This shows a light source embedded in a luminescence conversion element. In operation, the light source, also referred to as a primary radiation source, generates electromagnetic radiation of a first wavelength, which is converted by a luminescent material into electromagnetic radiation of a second wavelength.

However, such semiconductor light sources could have an unsatisfactory dissipation of heat loss from the luminescence conversion element. In particular, irradiation of the luminescence conversion element by a primary radiation source having a high energy density can lead to a relatively high temperature increase of the luminescence conversion element and in particular of the luminescence material. This adversely affects the efficiency of wavelength conversion by the luminescent material.

In the EP 1 734 302 A1 a semiconductor light source is shown in which a luminescence conversion element is provided with a heat conducting element.

In the pamphlets US 2006/0124951 A1 . EP 1760794 A1 . JP 2003-243717 A and US 2008/0042153 A1 Semiconductor light sources are described which have luminescence conversion elements made of ceramic materials.

It is intended to specify a light source arrangement which is suitable for producing light of different wavelengths with a particularly high luminous efficacy.

This object is achieved by the light source arrangement with a semiconductor light source according to the independent claim. Further developments and refinements emerge from the subclaims.

The light source arrangement comprises a primary radiation source with a layer sequence which, during operation, emits electromagnetic primary radiation along a first main emission direction. Furthermore, a luminescence conversion element spaced from the primary radiation source is provided, which has a heat sink and a luminescence material arranged thereon or thereon. The luminescent material is designed to convert at least a part of a coupled primary radiation into a secondary radiation along a second main beam direction with respect to the wavelength. Thus, the luminescent material serves to carry out a conversion of coupled primary radiation of a first wavelength into a secondary radiation of a second wavelength. The semiconductor light source further comprises a wavelength-selective reflector element, which is arranged in the beam path of the primary radiation source. The reflector element is designed to direct the primary radiation onto the luminescent material of the luminescence conversion element or to redirect secondary radiation emitted by the luminescent material in the direction of the primary radiation source. Furthermore, the light source arrangement comprises a second primary radiation source, which emits a third electromagnetic radiation, wherein the second primary radiation source is arranged opposite the primary radiation source, and wherein the wavelength-selective reflector element is designed for deflecting the third electromagnetic radiation.

The semiconductor light source thus generates during operation a wavelength-converted secondary radiation, for example a luminescence radiation. The spaced arrangement of the luminescence conversion element of the primary radiation source, a heating of the luminescence conversion element and the material contained therein is avoided by the primary radiation source. Rather, an efficient cooling of the luminescent material can be achieved by the heat sink of the luminescence conversion material, so that the conversion or conversion efficiency is increased.

It is achieved by the reflector element that the light emitted by the primary radiation source along the first main emission direction is directed substantially completely onto the luminescent material of the luminescence conversion element. This makes it possible to arrange the primary radiation source and the luminescence conversion element spatially separated from one another, in particular on different heat sinks. For example, the first main direction the primary radiation source are substantially perpendicular to the second main radiation direction. Correspondingly, the primary radiation source can also be arranged essentially at a right angle to the luminescence conversion element. The reflector element reflects the primary radiation emitted by the primary radiation source onto the luminescence material of the luminescence conversion element.

In one embodiment, a re-radiation of the secondary radiation emitted by the luminescent material to the primary radiation source is avoided by the reflector element deflecting the secondary radiation.

In a further development, the reflector element can be arranged both in the beam path of the primary radiation and the secondary radiation. In addition, in the first embodiment mentioned above, it can be substantially transparent to the secondary radiation. In this case, the reflector element reflects the primary radiation and directs it onto the luminescent material, while it is transparent to the converted secondary radiation. In the second embodiment, in which the primary radiation source and the luminescent element are arranged opposite one another, the reflector element can be transparent to the primary radiation and can have a high reflection with respect to the secondary radiation.

In one embodiment, the reflector element has a dichroic mirror which has a reflection behavior in a first wavelength range and a corresponding transmission behavior in a second wavelength range. In this case, the first wavelength range may be a range of the primary radiation or the secondary radiation, and the second wavelength range may correspond to a range of the secondary radiation or the primary radiation.

In a further embodiment, the reflector element may have two reflector surfaces arranged substantially perpendicular to one another. For example, the reflector element may be a prism with a partially mirrored surface. The embodiment with two reflector surfaces arranged essentially perpendicular to one another makes it possible to design the first and the second main emission directions essentially parallel to one another. As a result, both the primary radiation source and the luminescence conversion material spaced therefrom can be fastened on a common holding element.

For the layer sequence of the primary radiation source, a material, preferably a semiconductor material, which generates electromagnetic radiation in the ultraviolet range is suitable. By way of example, the layer sequence may comprise indium gallium nitride In _x Ga _1-x N or gallium nitride in different proportions. The luminescent material may be configured to generate a secondary radiation in the green region of visible light by a conversion of radiation of shorter wavelength, in particular of ultraviolet electromagnetic radiation. As a result, green light with a high energy density can be generated particularly efficiently. This allows the production of projectors or bulbs that produce white light.

In one embodiment, the luminescence conversion material is provided on one side with a mirrored material. As a result, both a coupled-in primary radiation is reflected back, as well as secondary radiation generated by the luminescent material. This reflective layer is arranged so that it reflects primary and secondary radiation substantially parallel to the second main radiation direction. The reflection of the primary radiation also increases the efficiency since the reflected primary radiation now traverses the luminescence conversion material again. The luminescent material may be in the form of a single crystal or a ceramic material. Likewise embedding of the luminescent material in a plastic or a silicate is possible.

To improve the coupling of the primary radiation into the luminescence conversion element or into the luminescent material, the surface of the material may have a roughening or structuring.

In another embodiment, a first lens system is arranged between the primary radiation source and the reflector element. Alternatively or additionally, a lens system may also be arranged between the reflector element and the luminescence conversion element. The lens system may include a positive lens and / or a diverging lens. This ensures that emitted by the primary radiation source light is collimated. The parallel light beams are guided by the reflector element on the conversion element. By a second lens system between the reflector element and the luminescence conversion element, the parallel primary radiation can be bundled again and concentrated directed to the luminescent material.

Alternatively, it is possible to reduce the radiation density on the reflector via diverging lenses and thus to protect it from additional heating. By an appropriate Conveying lens, the light is focused back and directed to the luminescence conversion element.

The semiconductor light source is suitable for being incorporated in a light source arrangement in order, for example, to form a white light source with further radiation sources.

For this purpose, a light source arrangement comprises, in addition to the semiconductor light source with the primary radiation source and the second radiation source for generating the third electromagnetic radiation, a third radiation source for generating a fourth electromagnetic radiation. The third and fourth electromagnetic radiation may each have different wavelengths and moreover have wavelengths different from the wavelengths of the primary radiation and the secondary radiation.

For example, the second radiation source for generating light in the blue region and the third radiation source for generating light in the red region can be configured. With the luminescence conversion element of the semiconductor light source, which is designed to convert ultraviolet light into green light, it is thus possible to generate white light with a high intensity and luminosity. In addition, the light source arrangement comprises a reflector arrangement, which is arranged in a beam path of the secondary radiation, the third and the fourth radiation and configured to align the secondary radiation, the third and the fourth radiation essentially parallel to one another.

The combined superposition of the secondary radiation, the third and the fourth radiation produces a combined hue.

In addition, in the beam path of the third and fourth radiation source and in the beam path of the secondary radiation, a luminescent screen, such as an LCD screen, are provided. This makes it possible to obtain colored images after a common superposition of the different electromagnetic radiations.

• 1 eine schematische Draufsicht auf eine Lichtquellenanordnung gemäß einem ersten Ausführungsbeispiel der Erfindung,
• 2 eine schematische Draufsicht auf ein Beispiel einer Lichtquellenanordnung,
• 2A eine Darstellung des Reflexionsverhaltens gegenüber der Wellenlänge bei verwendeten Reflektorflächen gemäß dem Beispiel der 2,
• 3 eine schematische Draufsicht auf ein Beispiel einer Lichtquellenanordnung,
• 4 eine schematische Draufsicht auf ein Beispiel einer Lichtquellenanordnung,
• 5 einen schematischen Querschnitt einer Linsenanordnung,
• 6 eine schematische Draufsicht auf eine Lichtquellenanordnung nach einem weiteren Ausführungsbeispiel,
• 7 einen schematischen Querschnitt einer Leuchtdiode, die als Primärstrahlungsquelle einsetzbar ist,
• 8 einen schematischen Querschnitt eines Lumineszenzkonversionselements.

In the following, the invention will be described with reference to several exemplary embodiments ( 1 . 5 . 6 . 7 and 8th ) and not according to the invention further examples ( 2 . 2A . 3 . 4 ) with reference to the drawings explained in detail. Show it:

• 1 a schematic plan view of a light source arrangement according to a first embodiment of the invention,
• 2 a schematic plan view of an example of a light source arrangement,
• 2A a representation of the reflection behavior with respect to the wavelength at reflector surfaces used according to the example of 2 .
• 3 a schematic plan view of an example of a light source arrangement,
• 4 a schematic plan view of an example of a light source arrangement,
• 5 a schematic cross section of a lens arrangement,
• 6 a schematic plan view of a light source arrangement according to a further embodiment,
• 7 a schematic cross section of a light emitting diode, which can be used as a primary radiation source,
• 8th a schematic cross section of a luminescence conversion element.

In the exemplary embodiments and the figures, the same or the same components bear the same reference numerals. The proportions of the elements shown in the figures with each other are not necessarily to be considered as true to scale. For example, the individual elements may be shown exaggeratedly large and / or thick for better representability or for better understanding.

1 shows an embodiment of a light source arrangement with a semiconductor light source according to the proposed principle. The semiconductor light source comprises a primary radiation source 110 and a luminescence conversion element spaced therefrom and arranged substantially perpendicular thereto 120 , The primary radiation source 110 and the luminescence conversion element 120 each have a heat sink 111 respectively. 121 on, which is designed as a heat sink. The heat generated in an operation of the semiconductor light source can thus be effectively dissipated via the two cooling elements. As a result, in particular the efficiency of the luminescence conversion element is increased.

The primary radiation source comprises, in addition to the heat sink, a light-emitting diode realized by semiconductor technology or a light-emitting component. The light-emitting diode 112 emits in its main beam direction electromagnetic radiation in the ultraviolet range. As shown here, the main radiation direction is perpendicular to the cooling element 111 , the light-emitting diode 112 and thus in the direction of the reflector 160 which will be described below. The radiation is cone-shaped, which is indicated here by the curved light beams.

The light-emitting diode can be formed, for example, as a thin-film light-emitting diode chip and arranged on a carrier substrate. This carrier substrate is in turn connected to the heat sink 111 connected. Alternatively, the carrier substrate itself may also be part of the heat sink 111 form.

• - an einer zu einem Trägersubstrat hingewandten Hauptfläche der strahlungserzeugenden Halbleiterschichtenfolge, bei der es sich insbesondere um eine strahlungserzeugende Epitaxie-Schichtenfolge handelt, ist eine reflektierende Schicht aufgebracht oder ausgebildet, die zumindest einen Teil der in der Halbleiterschichtenfolge erzeugten elektromagnetischen Strahlung in diese zurückreflektiert;
• - der Dünnfilm-Leuchtdiodenchip weist ein Hilfsträgerelement auf, bei dem es sich nicht um das Wachstumssubstrat handelt, auf dem die Halbleiterschichtenfolge epitaktisch gewachsen wurde sondern um ein separates Trägerelement, welches nachträglich an der gewachsenen Halbleiterschichtenfolge befestigt wird;

• - die Halbleiterschichtenfolge weist eine Dicke im Bereich von zwanzig Mikrometer oder weniger, insbesondere im Bereich von zehn Mikrometer auf;
• - die Halbleiterschichtenfolge ist frei von einem Aufwachssubstrat. Hierbei bedeutet „frei von einem Aufwachssubstrat“ das ein gegebenenfalls zum Aufwachsen benutztes Aufwachssubstrat von der Halbleiterschichtenfolge entfernt oder zumindest stark gedünnt ist. Insbesondere ist es derart gedünnt, dass es für sich oder zusammen mit der epitaktisch gewachsenen Schichtenfolge alleine nicht freitragend ist. Der verbleibende Rest des stark gedünnten Aufwachssubstrats ist insbesondere als solches für die Funktion eines Aufwachssubstrats ungeeignet; und
• - die epitaktisch gewachsene Schichtenfolge enthält mindestens eine Halbleiterschicht mit zumindest einer Fläche, die eine Durchmischungsstruktur aufweist, welche im Idealfall zu einer annähernd ergodischen Verteilung des Lichts in der Halbleiterschichtenfolge führt. Sie weist damit ein möglichst ergodisch stöchiastisches Streuverhalten auf.

A thin-film light-emitting diode chip is characterized by at least one of the following features:

• a reflective layer, which reflects back at least a part of the electromagnetic radiation generated in the semiconductor layer sequence, is applied or formed on a main surface of the radiation-generating semiconductor layer sequence facing a carrier substrate, which is in particular a radiation-generating epitaxial layer sequence;
• the thin-film light-emitting diode chip has an auxiliary carrier element, which is not the growth substrate on which the semiconductor layer sequence has been epitaxially grown, but a separate carrier element which is subsequently attached to the grown semiconductor layer sequence;

• the semiconductor layer sequence has a thickness in the range of twenty micrometers or less, in particular in the region of ten micrometers;
• - The semiconductor layer sequence is free of a growth substrate. Herein, "free from a growth substrate" means that a growth substrate optionally used for growth is removed from the semiconductor layer sequence or at least heavily thinned. In particular, it is thinned so that it alone or together with the epitaxially grown layer sequence alone is not self-supporting. The remainder of the highly thinned growth substrate is particularly unsuitable as such for the function of a growth substrate; and
• the epitaxially grown layer sequence contains at least one semiconductor layer having at least one surface which has a mixing structure which, in the ideal case, leads to an approximately ergodic distribution of the light in the semiconductor layer sequence. It thus has as ergodically stoichiastic scattering behavior as possible.

A basic principle of a thin-film light-emitting diode chip is, for example, in the document Schnitzer et al. Appl. Phys. Lett. 63 (16), 18 October 1993, pages 2174 to 2176 whose disclosure content is hereby incorporated by reference. Further examples of thin-film light-emitting diode chips can be found in the documents EP 0 905 797 and WO 02/13281 , the corresponding disclosure of which is hereby also incorporated by reference.

A thin-film light-emitting diode chip is, to a good approximation, a Lambertian surface radiator and is accordingly well suited for applications in light sources which require a high luminosity. Other lighting applications are very well feasible with such a radiator.

Semiconductor layers of a III / V compound semiconductor material, for example indium gallium nitride / gallium nitride, are suitable for generating light in the ultraviolet range. In this case, the wavelength of the emitted electromagnetic radiation can be adjusted via a stoichiometric distribution In _x Ga _1-x N of the ratio x of indium and gallium. The wavelength can be adjusted from the blue-green over the blue range to the near ultraviolet. For the light source shown is therefore also a primary radiation source that generates light in the blue visible range.

In one embodiment of a layer sequence forming a light-emitting diode, this has an at least partially mirrored layer on a surface opposite the main emission surface. A refractive index of this mirror layer points away from the refractive index of a layer of the epitaxially grown layer sequence which follows and in particular adjoins the mirror layer in the direction of the main emission surface. As a non-limiting example, the refractive index may be around the value 1 or more. The mirror layer may contain, for example, a metal but also a dielectric such as SiO ₂ .

In one embodiment, the mirror layer may be semiconductive or electrically insulating and may include a distributed Bragg reflector (DBR). This may have at least one layer pair with alternating high or low refractive index.

In a further embodiment, it may be expedient to also carry out contact elements for the layer sequence with mirrored surfaces. Mirrored surfaces can likewise be provided in isolation between the contact elements, so that the surface opposite the main emission surface has a mirrored subregion of more than 50% of the total area. In a variant, the surface opposite the main emission surface may be substantially completely mirrored, wherein a plurality of isolated openings may be provided which form the contact elements for connection to the active layer.

In the concrete case of the 1 indicates the LED 112 on the surface opposite the main emission side, a mirrored layer for improving the emission characteristic.

The luminescence conversion element 120 contains next to the heat sink 121 also a luminescent material arranged thereon and attached 122 , The luminescent material 122 is applied to the surface of the heat sink. This can be done either directly or with additional materials that allow a holder and a better attachment.

In addition, an additional mirror layer may be provided between the luminescent material and the heat sink, which on the one hand reflects radiation generated by the luminescent material and on the other hand also casts coupled radiation back into the luminescent material. This improves a conversion of a coupled-in radiation and increases the luminous efficacy of the secondary radiation.

The luminescent material may have an inorganic phosphor which converts primary radiation from a first wavelength range into an electromagnetic secondary radiation in a second wavelength range. In this case, the second wavelength range is different from the first wavelength range. For example, such a conversion is generated by excitation of the primary radiation for fluorescence or phosphorescence of the phosphor.

A convertible phosphor includes a material from the group containing garnet phosphors, such as rare earth doped yttrium aluminum garnet (YAG). For example, SrAl ₂ O ₄ : Eu ²⁺ is suitable for converting ultraviolet or blue radiation into electromagnetic radiation in the green wavelength range. Green to green-yellow emitting phosphors are, for example, chlorosilicates of the formula Ca ₈ Mg (SiO ₄ ) ₄ Cl ₂ : Eu ²⁺ , Mn ²⁺ , which are doped with europium or manganese. Tiogalates of the general formula AGa ₂ S ₄ : Eu ²⁺ , Ce ²⁺ are also suitable for this purpose, where "A" is selected in particular from the group: calcium, strontium, barium, zinc or magnesium.

Other suitable luminescence conversion materials, such as a YAG: Ce powder are, for example in the WO 98/12757 whose contents are hereby incorporated by reference. These luminescent materials produce second wavelength light of radiation of a first wavelength shorter than the second wavelength. If, for example, blue or ultraviolet light is irradiated onto the conversion material, then the phosphor adsorbs the radiation and thereby excites a portion of its electrons, which emit light in the relaxation in a low-energy range, for example in the green range.

The luminescent material is in the form of a powder, which is introduced into a fixing layer, for example a silicon oxide layer or a temperature-resistant silicate layer. This protects the luminescent material from mechanical damage and allows uniform distribution over a predefined area.

In order to increase the thermal conductivity of the luminescent material, it can also be present as a powdered phosphor introduced into a ceramic material or as a single crystal. For example, the luminescent material is sintered on a ceramic surface, wherein the ceramic surface has a particularly high thermal conductivity to the heat sink.

In the present embodiment according to 1 the beam directions of the primary radiation and the secondary radiation are different. The semiconductor light source therefore further comprises a reflector 160 , This is arranged in the beam path of the primary and the secondary radiation, so that it from the light emitting diode 112 emitted primary radiation to the luminescence conversion element 120 directs. In the present embodiment, the reflector 160 arranged at 45 ° to the main emission of the primary radiation.

The present reflector 160 shows a wavelength-selective reflection and transmission behavior. In terms of primary and secondary radiation. So he has a high reflection coefficient in the wavelength range of the primary radiation, so that in operation of the light source of the light emitting diode 112 generated ultraviolet radiation on the luminescence conversion element 120 is reflected. This is indicated by the indicated light beams, which simultaneously illustrate the beam path.

Furthermore, the reflector has 160 a particularly large transmission coefficient for the secondary radiation emitted by the luminescence conversion element, so that it is substantially unattenuated by the reflector 160 passes through. In other words, the reflector may be referred to as a semitransparent mirror, wherein the term is semi-transparent based on its wavelength-dependent reflection and transmission behavior.

Such a reflector 160 can be realized for example with a dichroic mirror. The same is a mirror that reflects a part of the light spectrum and lets the rest through essentially unattenuated. It is similar in behavior to an optical band-stop filter, in contrast to which it does not absorb the part of the spectrum, as in the case of the barrier, but reflects it.

Dichroic mirrors are based on the interference of the light waves, which are reflected by a succession of several thin dielectric layers on the surface. As a result, the beam portions reflected and transmitted at the boundary surfaces of the layers interfere, so that extinction occurs in the case of destructive interference or to amplify beams of a specific wavelength. By varying the thickness, the number of layers and the material used, the reflection as well as the transmission behavior of a dichroic mirror can be chosen exactly.

As a result, there is no absorption of electromagnetic radiation within the mirror material compared to conventional filters or mirrors, so that the thermal load on dichroic mirrors is very low. They can be used with advantage especially at a high radiation density.

The primary radiation source with the light emitting diode 112 as well as the luminescence conversion element 120 with the luminescent material 122 has a conical emission characteristic in each case in their main emission direction.

In order to improve the efficiency of a conversion further measures are provided to direct both the primary radiation and the secondary radiation in parallel and on the reflector surface 160 to steer. For this purpose is in front of the primary radiation source 110 a lens system of two lenses 113 and 114 arranged. These two serve to the shown here of the light emitting diode 112 parallel outgoing light rays. The parallelized primary radiation strikes the reflector surface after reflection 160 on the lens system from the lenses 123 and 124 , in front of the luminescence conversion element 120 are arranged. These act as converging lenses and focus the parallel primary radiation on the luminescence conversion material, so that the conversion efficiency is increased.

The through the luminescent material 122 the conversion element 120 generated secondary radiation is in turn conical and is arranged by the lens system arranged in the beam path of the secondary radiation 123 . 124 directed in parallel. As a result, a surface located in the beam path of the secondary radiation can be uniformly illuminated with high luminosity.

The semiconductor light source in the proposed principle makes it possible to generate from a primary radiation having a first wavelength by conversion a secondary radiation having a second wavelength with high luminosity and a large uniform luminous distribution. Due to the spatially separated arrangement of the luminescence conversion material on one side and the primary radiation source on the other side, a uniformly good cooling of the two elements can be achieved. As a result, on the one hand, the conversion efficiency is increased and, on the other hand, a flexible arrangement and design in various applications is achieved.

1 shows one of these applications in which the semiconductor light source is used as part of a light source arrangement to produce white composite light. For this purpose, the light source arrangement contains, in addition to the semiconductor light source already described, two further radiation sources 130 and 140 ,

This is another source of radiation 130 with a light emitting diode 132 formed, which generates light in the blue region of the visible spectrum. Such a light-emitting diode, like the light-emitting diode of the primary radiation source, can be realized with a thin-film technology.

Suitable materials are, for example, silicon carbide or indium gallium nitride / gallium nitride in various stoichiometric ratios. That of the LED 132 emitted light is also through the reflector 160 reflected and in the present case aligned parallel to the beam path of the secondary radiation. For this purpose, as shown here, the radiation source 130 opposite the primary radiation source 110 arranged.

Another fourth radiation source 140 contains a light emitting diode 142 , arranged on a heat sink 141 , The light-emitting diode 142 is designed to generate light in the red region of the visible spectrum. In addition to organic light-emitting diodes, inorganic semiconductor compounds, for example aluminum gallium arsenide / gallium arsenide (Al-GaAs / GaAs), gallium arsenide phosphite compounds (GaAsP) and aluminum indium gallium phosphite compounds (AlInGaP) are suitable for this purpose.

In this embodiment, the fourth radiation source is aligned parallel to the third radiation source, whereby the main emission direction is substantially perpendicular to the beam direction of the secondary radiation. For deflecting the light from the LED 142 generated red light is this another reflector 150 intended. This also has a wavelength-selective transmission and reflection behavior. In particular, it reflects radiation in the red region of the visible spectrum while transmitting electromagnetic radiation in the blue or green region of the electromagnetic spectrum without being attenuated.

The reflector 150 is parallel to the first reflector 160 and may also include a dichroic mirror. In other words, it is at 45 ° to the main radiation direction of the fourth radiation source, whereby the light emitted from the LED 142 the fourth radiation source 140 generated light is reflected parallel to the main emission direction of the secondary radiation. This results in the area 90 a light spectrum, which is composed of the light components of the secondary radiation and the reflected blue and red radiation. With a suitable choice of the different light spectra and a corresponding adjustment of the luminous intensity can thus in the output range 90 white light composed of different colors.

2 shows an example of a light source arrangement for the conversion of a primary radiation into a secondary radiation in the green region of the visible spectrum.

In this example, the primary radiation source together with a third and fourth radiation source are on a common heat sink 211 attached. The heat sink 211 has a variety of cooling ribs, not shown here, to increase the surface and thus to allow effective heat dissipation. Furthermore, the heat sink contains 211 Attachments for the supply of the necessary electrical contact lines to the individual LEDs 212 . 223 and 242 , The top 211 of the common heat sink 211 is executed in the area in which the individual diodes of the radiation sources are arranged, mirrored. As a result, the light generated in the light-emitting diodes is reflected back into the main emission direction.

Furthermore, in front of each LED 212 . 232 and 242 a lens system of corresponding collecting and diverging lenses arranged. More specifically, each lens system includes a first converging lens 213 . 233 . 243 and a second lens 214 . 234 . 244 with which the radiation cone of the individual light-emitting diodes is collimated. This results in a uniform illumination of a surface in the output area 90 reaches the light source assembly.

In the present example, the luminescence conversion element is 220 substantially perpendicular to the heat sink 211 and the primary radiation sources 200 arranged. The luminescence conversion element likewise comprises a heat sink 221 and thereon a fixed device with the luminescence conversion material 222 , In turn, before the luminescence conversion material is a lens system of the two lenses 223 and 224 intended. On the one hand, these focus on those of the diode 212 generated and on the reflector 270 reflected radiation on the luminescence conversion material. On the other hand, they also serve to collect the radiation cone of the secondary radiation, so that the beam path of the secondary radiation is parallel in the direction of the output region 90 runs. This is indicated by the parallel light beams after the lens arrangement of the lenses 223 and 224 ,

In this example, the reflector 270 substantially perpendicular to the second reflector 280 for the third radiation source and the reflector 250 arranged for reflection of the fourth radiation. Again, the individual reflector surfaces are realized for example by dichroic mirrors with different transmission and reflection behavior. For example, the reflector shows 270 a reflective behavior for the wavelength of the light emitting diode 212 emitted primary radiation.

This through the luminescent material 222 Conversely, converted light is through the three reflectors 270 . 280 and 250 let through almost undamped. Accordingly reflects the reflector 280 that of the light emitting diode 232 generated light and the reflector 250 that of the light emitting diode 242 generated light on the output area 90 the light source arrangement out. The corresponding incident from the left secondary radiation is from the reflector 280 pass through. The reflector also transmits accordingly 250 both the secondary radiation and that of the light emitting diode 232 generated radiation.

To generate white light, for example, the reflector 250 have a reflective behavior in the red area. The light-emitting diode 242 then emits corresponding red light. The reflector 280 shows a strong reflection in the blue area and a correspondingly high transmission for green light.

For the generation of green light, it is now appropriate to use on the one hand radiation in the ultraviolet range as well as radiation in the blue visible range of the spectrum. Accordingly, the light-emitting diode generates 212 either blue light or light in the near ultraviolet range. In the first case, the reflector 270 made of the same material as the reflector 280 consist. For example, such a prism can be formed with the two reflective surfaces.

2A shows the reflection behavior of the reflectors 250 . 270 and 280 depending on the wavelength of the incident light.

In the curve L270, the reflection is a function of the wavelength for the reflector 270 according to the embodiment in 2 shown. Here, above all, light in the region of the ultraviolet spectrum in the direction of the luminescence conversion element 220 reflected. The reflector 270 on the other hand shows only a small reflection of light in the green region of the visible spectrum, ie at about 550 nm. The same applies to the reflection behavior of the reflector 280 shown in curve L280, which has its greatest value in the blue region of the visible spectrum at about 450 nm. Again, light is transmitted in the green region of the electromagnetic spectrum. The reflection of the reflector 250 is again highest in the red region and falls sharply towards the green and blue regions of the visible spectrum. The three reflector surfaces with a wavelength-selective transmission and reflection behavior thus allow selectively to reflect different colors and thus in the output range 90 the light source assembly to produce a mixed light. By a current flow change through the individual LEDs also single spectral components can be amplified.

3 shows another example of a light source arrangement in which the three primary radiation sources 310 . 330 and 340 and the luminescence conversion element 320 are arranged parallel to each other. The primary radiation sources each contain an array 312 . 332 . 342 juxtaposed LEDs. Individual LEDs of the array can be controlled differently so as to produce, for example, a different light intensity.

In this example, there are four reflector surfaces 350 . 370 . 380 and 390 provided to the radiation generated by the LEDs of the primary radiation sources and the luminescent material of the conversion element in the output region 90 to focus the light source assembly. The reflector surfaces 350 . 370 and 380 are formed with dichroic mirrors. The reflector surface 390 can be designed for cost reasons as a normal mirror, if sufficient heat dissipation is guaranteed.

Also in this example is in front of each primary radiation source and the luminescence conversion element 320 a lens system of two lenses 313 to 343 such as 314 to 344 arranged. The lens system for the conversion element 320 serves, on the one hand, those of the diode 312 generated and through the lens system 313 . 314 to focus in parallel directed primary radiation. At the same time that of the conversion material 323 radiated secondary radiation collected by the lens system and parallel to the reflector surface 390 bundled. It thus acts as a combined converging lens. The reflector surface 390 reflects both the primary radiation of the source 310 as well as the secondary radiation of the luminescence conversion element 320 .

The individual cooling elements 311 to 341 the primary radiation sources 310 . 330 . 340 and the luminescence conversion element 320 are shown separately in this embodiment. Each individual cooling element constitutes a heat sink for cooling the corresponding primary radiation source or the luminescence conversion material. The cooling elements may, for example, have a plurality of cooling fins running in parallel in order to improve heat dissipation to the environment.

On their surface, the cooling elements with the corresponding LED arrays 312 . 332 and 342 or with the luminescence conversion material 322 be connected. The layer sequence of the light-emitting diode arrays is in turn applied to a substrate wafer and thus forms the array. The substrate wafer may also form part of the cooling element. Alternatively, the cooling element may also have a V-shaped or U-shaped structure, for example in the form of a recess. In this, the luminescence conversion material or even individual light-emitting diodes or the entire light-emitting diode array can be arranged. This allows cooling not only from the back, but also from the side surface, which further enhances efficiency. In addition, a particularly compact design of the light source arrangement can be realized.

4 shows another example. In this case, the luminescence conversion element 420 perpendicular to the primary radiation sources 410 . 430 and 440 arranged. In the beam path of the second and third primary radiation source 430 and 440 and the luminescence conversion element 420 In addition, a so-called "Color Cube" 490 is provided. This includes as indicated several reflector elements 490a . 490b , which are perpendicular to each other. They are opposite the radiation paths of the two primary radiation sources 430 . 440 and the luminescence conversion element 420 each offset by an angle of 45 °.

Between the "Color Cube" 490 and the corresponding lens systems 433 . 434 the second primary radiation source 430 as well as the lens system 443 . 444 the third primary radiation source 440 each liquid crystal screens (LCD screens) are arranged for individual fields. In the same way is also between the beam path of the luminescence conversion 420 and the "Color Cube" 490 a liquid crystal screen 494 intended. The liquid crystal displays, or liquid crystal displays, are screens or displays whose function is based on the fact that liquid crystals can influence the polarization direction of light in the case of an applied voltage. Depending on the orientation of the liquid crystals, the light may penetrate the screen or not. Thus, in the simplest form on the other side creates a "light-dark" image.

By dividing into individual picture elements, a different brightness can thus be achieved for each subarea of a liquid crystal screen, called pixels, by appropriate alignment of the liquid crystals. In the downstream "Color Cube" 490 are those of the individual liquid crystal screens 492 . 493 and 494 generated red, blue and green fields composed and in the output area 90 the light source arrangement shown.

5 shows an enlarged view of the lens system with a reflector surface according to the example of 4 , Accordingly, this lens system can also be used in the other embodiments of the light source arrangement. In the embodiment, the lens system in each case comprises two lenses arranged one behind the other and symmetrically mounted about an optical axis. Further indicated are the surfaces 412a the light emitting diode and 422a of the luminescent material.

The reflector necessary for the deflection 470 with its planar surface L3 is also shown schematically. The two lens systems 423 . 424 such as 413 and 414 are structured similarly. The radius L1 of the first lenses 413 and 423 is greater than the radius L2 of the two lenses, resulting in a convex-concave diverging lens. From the surface 422a respectively. 412a radiated light is thus scattered. By arranged in the beam path biconvex converging lenses 424 respectively. 414 the emitted light is directed in parallel and on the reflector surface 470 directed. For this purpose, the radius of curvature L2.1 is greater than the radius of curvature L2.2 facing the reflector surface.

The from the surface 412a delivered and from the lens system 413 . 414 collimated radiation passes through the reflector surface 470 towards the lens system 424 . 423 directed. The parallel radiation is in the first lens 424 focused and through the second lens 423 slightly scattered so that they are as completely as possible on the existing conversion material on the surface 422a meets. There it is converted into secondary radiation and emitted again. The emitted secondary radiation is transmitted through the lens system 423 and 424 collected again and discharged in parallel along the optical axis.

7 shows an embodiment of a light emitting diode, which can be used for example as a primary radiation source, but also as a second or third radiation source. It may also be part of a diode array, which in turn forms a radiation source. The light-emitting diode is formed with a thin-film layer technology and on a substrate carrier 614 arranged. The substrate carrier 614 is formed of an electrically conductive material and comprises on its the main emission direction A opposite side of an electrical contact 612 , This serves to electrically contact an electrode of the light emitting diode. On the surface of the substrate carrier 614 is a light-emitting layer sequence realized with different semiconductor materials.

In the embodiment, a first electrically conductive and at the same time reflective layer 623 on the surface of the substrate carrier 614 applied. On this is a first doped semiconductor material 622 arranged. A differentially doped second semiconductor material is applied over it, as a result of which a pn junction 620 is formed at the interface. In this operation, the diode recombines externally injected holes and electrons with light generation.

On the second semiconductor layer 621 is a transparent electrode 624 applied and this via an electrical contact with a supply line 616 Mistake. The transparent electrically conductive layer 622 allows a large-scale coupling of charge carriers in the underlying semiconductor material 621 ,

Transparent conductive oxides ("TCO" for short) are transparent, conductive materials, usually metal oxides, such as zinc oxide, tin oxide, cadmium oxide, titanium oxide, indium oxide or indium tin oxide (ITO). In addition to binary metal oxygen compounds such as ZnO, SnO ₂ or In ₂ O _{3 also} include ternary metal oxygen compounds such as Zn ₂ SnO ₄ , CdSnO ₃ , ZnSnO ₃ , MgIn ₂ O ₄ , GaInO ₃ , Zn ₂ In ₂ O ₅ or In ₄ Sn ₃ O ₁₂ or mixtures of different transparent conductive oxides to the group of TCOs. Furthermore, the TCOs do not necessarily correspond to a stoichiometric composition and may also be p- or n-doped.

A feed of the charge carriers takes place via the supply line arranged on one side 616 , This leads outside the layer sequence via insulation 615 to one at the bottom of the substrate carrier 614 arranged second contact 613 , The insulation 615 prevents a short circuit between the electrically conductive substrate carrier 614 and contacting 616 ,

In addition, the layer sequence is with a transparent dielectric material 618 surrounded to protect against mechanical or chemical damage. For example, this transparent material may comprise silicon dioxide or a transparent plastic.

In addition, on the dielectric layer 618 , In particular on the side walls of the dielectric layer, a further mirror layer may be arranged. As a result, laterally emitted light is reflected back and optionally emitted along the main emission direction A.

8th shows an embodiment of a luminescence conversion element 820 , The element 820 is on a heat sink 821 arranged, which represents a good thermal heat sink. The luminescent material 822 is again on a mirror layer 822b applied as a planar layer. For example, the luminescent material is embedded and fixed in a ceramic carrier. To improve the conversion efficiency are also on the side walls of the luminescence conversion element 820 additional mirrors 822a arranged. As a result, converted light, which is in the direction of the side walls or in the direction of the cooling element 821 is emitted, reflected by the mirrors and transmitted in the main emission direction.

At the same time coupled primary radiation, which is not wavelength converted in the conversion material, through the additional mirror layer 822b reflected back into the conversion material. This increases the conversion probability and the efficiency of the conversion element is further improved.

The proposed invention is not limited by the description based on the embodiments. Rather, it includes every new feature as well as any combination of features of the individual embodiments, even if this feature or this combination is not explicitly specified in the exemplary embodiments and / or claims.

Claims (22)

Light source arrangement with a semiconductor light source, comprising: - A primary radiation source (110) having a layer sequence which emits in operation a first primary electromagnetic radiation along a first main radiation direction; a luminescence conversion element (120) spaced from the primary radiation source (110) and having a heat sink (121) and luminescent material (122) disposed thereon which wavelength converts at least a portion of the coupled primary radiation to at least one phosphor along a second radiation direction along a second main radiation direction; a wavelength-selective reflector element (160) which is arranged and designed in the beam path of the primary radiation source (110) to direct the primary radiation onto the luminescent material (122) of the luminescence conversion element (120) or from the luminescent material (122) in the direction of the primary radiation source (110). to redirect emitted secondary radiation, and - A second primary radiation source (130) emitting a third electromagnetic radiation, wherein the second primary radiation source (130) of the primary radiation source (110) is arranged opposite, and wherein the wavelength-selective reflector element (160) for deflecting the third electromagnetic radiation is formed. Light source arrangement according to Claim 1 in which the second main beam direction is not parallel to the first main beam direction. Light source arrangement according to one of Claims 1 to 2 in which the reflector element (160) is arranged in the beam path of the secondary radiation and is transparent to it. Light source arrangement according to one of Claims 1 to 3 in which the reflector element (160) has a dichroic mirror which exhibits a reflection behavior in the wavelength range of a radiation of the first primary radiation and the secondary radiation and a transmission behavior in the wavelength range of the other radiation. Light source arrangement according to one of Claims 1 to 4 in which the reflector element has two reflector surfaces arranged perpendicular to one another. Light source arrangement according to one of Claims 1 to 5 in which the layer sequence of the primary radiation source (110) comprises indium gallium nitride and gallium nitride. Light source arrangement according to one of Claims 1 to 6 in which the layer sequence of the primary radiation source (110) generates a primary radiation in the ultraviolet range. Light source arrangement according to one of Claims 1 to 7 in which the luminescent material (122) generates a secondary radiation in the green region of visible light by a conversion of radiation of shorter wavelength. Light source arrangement according to one of Claims 1 to 8th in which the luminescence conversion element (120) comprises a reflective layer which is arranged on one side of the luminescent material (122) and which reflects primary and / or secondary radiation parallel to the second main radiation direction. Light source arrangement according to one of Claims 1 to 9 in which the primary radiation source (110) and the luminescence conversion element (120) are formed with different, mutually thermally separated heat sinks (111, 121). Light source arrangement according to one of Claims 1 to 10 in which the luminescence conversion element (120) has the shape of a planar layer or a plate whose surface is perpendicular to a direction of irradiation of the primary radiation and / or the secondary radiation. Light source arrangement according to Claim 11 in which a reflective layer is disposed on an opposite surface to the surface of the luminescence conversion element (120). Light source arrangement according to one of Claims 11 to 12 in which the surface has a roughening and / or structuring. Light source arrangement according to one of Claims 1 to 13 in which a first lens system (113, 114) is arranged between the primary radiation source (120) and the reflector element (160). Light source arrangement according to one of Claims 1 to 14 in which a second lens system (123, 124) is arranged between the reflector element (160) and the luminescence conversion element (120). Light source arrangement according to one of Claims 14 to 15 in which the lens system (113, 114, 123, 124) comprises at least one converging lens and / or a diverging lens. Light source arrangement according to one of Claims 14 to 16 in which the first (113, 114) and / or second lens system (123, 124) is designed to parallelize the primary and / or secondary radiation. Light source arrangement according to one of Claims 1 to 17 and further comprising: - a third primary radiation source (140) for generating a fourth electromagnetic radiation having a wavelength different from wavelengths of the primary radiation, the secondary radiation and the third electromagnetic radiation; a reflector arrangement which is arranged in a beam path of the secondary radiation as well as the third and fourth radiation and is configured to align secondary radiation, third and fourth radiation parallel to one another. Light source arrangement according to Claim 18 in which at least two of the primary radiation sources (110, 130, 140) are arranged on a common heat sink. Light source arrangement according to one of Claims 18 to 19 in which the heat sink (121) of the luminescence conversion element (110) and at least one of the primary radiation sources (110, 130, 140) are arranged on a common heat sink. Light source arrangement according to one of Claims 18 to 20 in which a lens system is arranged between the third primary radiation source and the reflector arrangement. Light source arrangement according to one of Claims 18 to 21 in which the primary radiation and the third electromagnetic radiation have the same electromagnetic spectrum.

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