DE102015205353A1 - lighting device - Google Patents

Abstract

Disclosed is a lighting device with a light source, via which a conversion element is irradiated, which converts a light wavelength of a portion of the light. The illumination device has an optical element in which at least one scattering area is formed. Scattered light can be detected by at least one light sensor to detect a malfunction of the illumination device.

Description

Technical area

The invention is based on a lighting device according to the preamble of claim 1.

State of the art

In the document WO 2014/037217 A1 such a lighting device is disclosed. This has a light source in the form of a laser diode which emits blue light. In the radiation direction of the laser diode, a conversion element is arranged. This partly converts the blue light into yellow light, so that light emerging from the conversion element is white, ie a mixture of unconverted blue light and converted yellow light. The lighting device further has a first light sensor that can detect blue light and a second light sensor that can detect yellow light. The light intensities determined by the sensors are evaluated by an evaluation unit. In particular, a quotient of the converted yellow light to the unconverted blue light is determined here. If this quotient changes by a predetermined amount, a malfunction of the illumination device is inferred. A disadvantage of this solution is that the light sensors measure the light directly, whereby the radiation emitted by the conversion element should be disturbed as little as possible, which is why arrangements of the light sensors in the illumination device are very limited.

Presentation of the invention

The object of the present invention is to provide a lighting device which is designed device technology simple and flexible and is safe to use.

This object is achieved by a lighting device according to the features of claim 1.

Particularly advantageous embodiments can be found in the dependent claims.

According to the invention, a lighting device is provided with at least one light source. The light source is preferably associated with a conversion element for converting light wavelengths of a light emitted by the light source. Furthermore, an optical component is provided, which is preferably arranged in the light path of the light emitted by the at least one light source. In the optical component, at least one scattering range or a scattering center or a scattering point for scattering a, in particular small, or in particular comparatively small, part of the light can be introduced in the light path. Furthermore, at least one light sensor can then be assigned to the optical component, with which at least part of the light scattered by the scattering range can be detected or detected.

This solution has the advantage that converted and unconverted light is no longer detected and characterized directly by the sensor, but decouples one or more scattered regions of light from the optical path for the measurement. This results in a measuring position (scattering range) and a position of the light sensor being separated from one another, which leads to a flexible arrangement of the light sensor and the measuring position (scattering range). Furthermore, the measuring position, ie the scattering range, can be made extremely small and, for example, have only a few μm, which is why the scattering range can in principle be arranged arbitrarily close to the conversion element without leading to interference. Since optical components are usually present in an illumination device, the at least one scattering region can thus be formed in an already existing optical component, so that no additional optical component is required. Since the scattering range, as already explained above, can have an extremely small size, it is possible to flexibly arrange or form it in the illumination device. Thus, in contrast to the prior art, where the light sensors can be tapped directly by the light sensors, the scattering range or measuring position can be arranged in the most suitable position, so that they can only be arranged inflexibly in the illumination device. A detection of a malfunction of the illumination device can thus be optimized by suitably selecting a position of a scattering range or by suitably selecting positions of a plurality of scattering regions and / or by a suitable choice of the number of scattering regions.

The light source can be considered together with the conversion element as a light source, which is then in particular the light source is a remote phosphor laser light source.

With the at least one light sensor, preferably with two light sensors, detection of the luminous flux and / or the ratio of converted to unconverted light over the scattering range or, in the case of several scattering regions, integrally over all scattering ranges can take place. In this case, in particular a change in the luminous flux with respect to a reference luminous flux and / or a change in the said ratio can be monitored.

The scattering area or the plurality of scattering areas are preferably arranged in a central emission area.

By a suitable position of the scattering range or the scattering ranges, as already explained above, the detection of the fault of the illumination device can be optimized. In this case, the scattering region or the plurality of scattering regions can preferably be arranged as close as possible to the conversion element. Furthermore, the scattering range or the plurality of scattering ranges can be arranged directly or at least comparatively close in the region of the greatest luminance (maximum of the light beam).

In a further embodiment of the invention, the optical component is preferably configured and / or the at least one scattering area is arranged and / or configured in the optical component such that at least part of the light scattered by the scattering area is totally reflected in the optical component. This solution has the advantage that a part of the scattered light can be guided by the total reflection thus away from the scattering range and thus away from the non-scattered luminous flux in a simple manner. The scattered light can then be guided further out of the optical component in a region which does not disturb the non-scattered luminous flux and can be detected by the light sensor. Preferably, at least part of the totally reflected light is totally reflected in such a way that it is conducted to an edge region of the optical component. It can then be tapped from there, as already explained, by the light sensor without the non-scattered luminous flux being influenced. Thus, a part of the scattered light remains in the optical component by means of total reflection and can be detected with the at least one light sensor, which is preferably arranged at the edge of the optical component. Furthermore, as a result, the light sensor can be arranged in an edge region outside the non-scattered luminous flux. The light scattered by the at least one scattering area, which is not totally reflected, initially remains in the illumination device as scattered light. This light is advantageously greatly reduced by the configuration of the at least one scattering area with a small size and by the flexible and thus suitable positioning of the at least one scattering area.

In a further embodiment of the invention, the optical component is a cover of the illumination device. If the illumination device is used, for example, for a vehicle headlight, the cover plate may be a headlight cover disc. The cover is usually arranged in the direction of the luminous flux in the light path after the conversion element. The cover plate may have a light input side and a light output side comprised of a disk edge. The sensor can then be arranged in terms of device technology simply on the edge of the pane and / or the sensor detects the light emerging from the edge of the pane emerging scattered, in particular totally reflected.

Preferably, a reflector and a lens are arranged in the light path between the cover, in particular the Scheinwerferabdeckscheibe, and the conversion element. The reflector may then reflect outgoing light from the conversion element towards the lens. In the cover plate may be introduced a plurality or plurality of scattering areas. These can then further be arranged in a plane, wherein the plane extends approximately perpendicular to the luminous flux. Preferably, the scattering areas are evenly distributed in the cover.

Alternatively or in addition to the cover, a transparent cooling element or sapphire substrate or sapphire plate for the conversion element can be provided as an optical component for introducing the at least one scattering region. The cooling element is then preferably arranged in the direction of the luminous flux in the light path after or before the conversion element, wherein in turn the conversion element can be arranged on the cooling element. The cooling element has a light input and a light output side encompassed by an element edge. The light sensor can be arranged on the element edge and / or the light sensor detects the light emerging from the element edge, scattered, in particular totally reflected. In a preferred embodiment, the cooling element is arranged between the light source and the conversion element. A scattering range, two scattering ranges or a multiplicity of scattering ranges can be arranged at least slightly offset from the maximum of the luminance of the light which radiates into the conversion element.

In a further preferred embodiment, a TIR (Total Internal Reflection) optical element or a lens is provided as an optical component in which at least one scattering region is introduced. The TIR optical element or the lens can be arranged in the direction of the luminous flux in the light path after the conversion element. Preferably, the TIR optical element has a light input and a light output side encompassed by an element edge. The light sensor can be arranged on the element edge and / or the light sensor can detect the light emerging from the element edge scattered, in particular totally reflected. Preferably, a plurality of scattering regions, preferably three, are present in the TIR optical element. introduced, which are further preferably arranged in a common plane, which may extend approximately parallel to the conversion element approximately perpendicular to the light path. Furthermore, it is conceivable that a reflector is arranged in the light path between the conversion element and the lens.

Furthermore, it is advantageous that the scattering regions can be introduced into optical components which have a very wide variety of materials. For example, the optical component may consist essentially of glass, PE (polyethylene), PMMA (polymethyl methacrylate), acrylic glass, plexiglass, PC (polycarbonate), COP (cyclic olefin polymer), silicone or sapphire.

The light source is preferably a laser light source or a laser diode or a light emitting diode (LED). The LED may be in the form of at least one individually housed light emitting diode or in the form of at least one LED chip. Alternatively or additionally, a plurality of LED chips may be mounted on a common substrate ("submount"). The at least one light emitting diode may be equipped with at least one own and / or common optics for beam guidance, e.g. at least one Fresnel lens, collimator, and so on. Instead of or in addition to inorganic light emitting diodes, e.g. based on InGaN or AlInGaP, organic LEDs (OLEDs, for example polymer OLEDs) can generally also be used. Alternatively, the LED may also be a laser diode or a laser diode array. The emission wavelengths of the LED can be in the ultraviolet, visible or infrared spectral range.

Preferably, blue light is emitted from the light source or from the laser light source.

It is conceivable that a plurality of light sources is provided, and then a scattering area is formed for each light source. In this case, a scattering range can be introduced in a respective local maximum of the luminance or directly above a respective maximum of the luminance in the optical component.

The conversion element is preferably a conversion element containing phosphor to partially convert light emitted by the light source into light of other wavelengths. In the conversion element in particular blue excitation light can be partially converted into yellow conversion light, which then results in white light through the spatial mixture of unconverted excitation light and converted conversion light in normal operation.

The light sensor is preferably a photodiode. Furthermore, two light sensors are preferably provided, a light sensor being provided for detecting unconverted light, in particular short-wave light, in particular blue light, and the other light sensor for detecting converted light, in particular long-wave light, in particular yellow light. Thus, as already explained above, the ratio of converted to unconverted light can be determined via the two light sensors. Furthermore, a change in the luminous flux in comparison with a reference luminous flux can be determined with the light sensor.

In a further embodiment of the invention, the scattering device is simply introduced by means of an engraving, in particular an interior engraving, in particular a glass interior engraving, into the optical component. The glass engraving can be done for example by a laser engraving. Defective structures are created in the irradiated material, where the light is scattered or deflected. In this case, a plurality of scattering regions can also be formed in a simple manner. By engraving is also possible to design the scattering areas extremely small in the micron range, so that they can be arranged close to the conversion element.

Advantageously, the geometry of the scattering area can be made flexible. For example, the scattering area may have a line shape or a spherical shape or a symmetrical pattern. Furthermore, the symmetrical pattern or, in general, the geometry of the scattering area can advantageously be formed as a function of the illuminance of the optical component.

The scattering range is preferably introduced into the optical component in the region or directly above the region of the largest luminance occurring in normal operation. To characterize the light detected by the at least one light sensor, an evaluation device (CPU) may be provided. The light detection by one or more sensor (s) and the evaluation by an evaluation must be done very quickly, so that in case of error, so with increased radiation intensity of the exiting unconverted laser radiation, for example, in the presence of a defect of the conversion element (phosphor) or missing conversion element , The excitation light sources are either dimmed immediately to a photobiologically harmless intensity level or even switched off completely. This is done by means of a control device connected to the evaluation unit, which controls the operating devices of the excitation light sources or is connected directly to a switch-off element. A dimming or Shutdown of the excitation light sources should already take place after a few milliseconds, possibly even faster. A fault thus represents in particular an unconverted, emerging from the illumination device laser radiation whose intensity is a photobiological safety limit, especially in accordance with the IEC 62471: 2006 defined risk groups.

The photobiological safety of vehicle lights and vehicle headlights with LED or laser light sources must be guaranteed. According to the classification of risk groups IEC 62471: 2006 In any case, the achievement of risk group 3 must be avoided. It is even desirable to avoid risk group 2. If applicable, further relevant guidelines, for example from the Federal Institute for Occupational Safety and Health, must be taken into account. Here, the distinction between day, night and twilight is to be considered. This topic is particularly relevant in the context of laser light sources and other light sources in which the headlight has a particularly high luminance at the light exit surface. As a further example may be mentioned at this point high-current LEDs and in particular the use of the aforementioned light sources in headlamps with small aperture. Particularly critical in this context are dipped beam and high beam functions, as well as adaptive systems, in particular Advanced Forward Lighting Systems (AFS), and marker light function.

Brief description of the drawings

In the following, the invention will be explained in more detail with reference to exemplary embodiments. The figures show:

1 in a schematic representation of a lighting device according to the invention according to a first embodiment in normal operation

2 the lighting device off 1 in a malfunction

3 - 8th each in a schematic representation of different embodiments of the illumination device according to the invention

Preferred embodiment of the invention

According to 1 has a lighting device 1 According to a first embodiment, a light source in the form of a laser light source (not shown), whose emitted laser light 2 in 1 is shown schematically. The laser light 2 is focused and meets a conversion element 4 made of cerium-doped yttrium-aluminum garnet (Ce: YAG), with which part of the blue laser light 2 is converted into yellow light, bringing that from the conversion element 4 emitted light 6 , this in 1 is schematically indicated, white and strongly scattered.

The lighting device 1 further includes an optical device in the form of a cover 8th on, in the direction of radiation of the light 6 seen after the conversion element 4 is arranged. The cover 8th , for example in the form of a thin plate, has a light input side 10 and a light output side 12 , The pages 10 and 12 are from a disk edge 14 includes. Furthermore, in the cover 8th a scattered area 16 engraved, which is approximately in the middle between the pages 10 and 12 in the direction of radiation of the light 6 seen trained. The spreading area 16 sprinkle a small part of the through the cover 8th passing light 6 , A part 18 of the spreading area 16 scattered light is then by total reflection on the sides 10 and 12 inside the cover 8th to the disc edge 14 led, this part 18 of the scattered light by arrows in the 1 is marked. The part 18 The scattered light is therefore totally reflected, as this at an angle to the sides 10 . 12 which is larger than an angle for the total reflection. Another part 20 the scattered light, however, is not totally reflected and occurs, especially on the sides 10 and 12 , from the cover 8th from, which is also indicated by arrows.

At the disk edge 14 are two light sensors 22 . 24 provided, of which only one is shown for the sake of simplicity. At the light sensors 22 and 24 each is a photodiode. The one light sensor 22 can detect light in the short-wave, blue spectral range, thus he unconverted laser light 2 can capture that from the spread area 16 scattered and then totally reflected. The other light sensor 24 On the other hand, it can detect light in the long-wave, yellow spectral range, bringing it from the conversion element 4 converted light, that of the scattering area 16 scattered and then totally reflected.

According to the embodiment in FIG 1 it is assumed that there is no error. From the light sensors 22 and 24 Thus, a luminous flux is measured, which is the same compared to a reference luminous flux. Furthermore, a ratio of converted, yellow to unconverted, blue light has not changed.

According to 2 is a fault of the lighting device 1 shown. This involuntarily penetrates a larger part 26 of the laser light 2 the conversion element 4 unchanged, which is why the conversion element 4 has no or only limited functionality. With the light sensors 22 . 24 can be found that the luminous flux of the excitation radiation at a certain angle of radiation (within the laser beam) increases. Furthermore, via the light sensors 22 . 24 It can be seen that the ratio of converted, yellow and unconverted, blue light changes, since the proportion of unconverted laser light after the conversion element 4 is increased. This can indicate a malfunction of the lighting device 1 getting closed.

According to 3 has the lighting device 1 the conversion element 4 and the cover 8th , The conversion element 4 is from the laser light 2 irradiated. The cover 8th according to 3 is directly adjacent or after the conversion element 4 arranged. Furthermore, the scatter area 16 in the area of the maximum luminance or in the area directly above the maximum luminance. The sensors 22 . 24 are appropriate 1 on the cover 8th arranged. Such an arrangement of the scattering area 16 is possible because of this the luminous flux, the conversion element 4 emanating, practically unaffected. The conversion element 4 can have contact directly with the cover. The cover may, for example, be made of a good heat-conducting and optically transparent material sapphire or diamond, or made of glass or plastic.

According to 4 has the lighting device 1 a cooling element 28 in the form of a sapphire substrate on which the conversion element 4 in the form of a ceramic wafer of cerium-doped yttrium-aluminum garnet (Ce: YAG) is arranged. The cooling element 28 is according to 4 between the conversion element 4 and arranged the light source, not shown. The laser light 2 penetrates the cooling element 28 and radiates into the conversion element 4 , In the cooling element 28 are two scattered areas 30 and 32 brought in. Part of the conversion element 4 emitted light is from the scattering areas 30 . 32 scattered and total reflection to an element edge 34 of the cooling element 28 led, which between a light entrance side 36 and a light output side 38 is arranged. The element border 34 are the light sensors 22 and 24 assigned. According to 4 are the scattering areas 30 and 32 outside the highest luminance of the laser light 2 educated.

According to 5 is the conversion element 4 provided by three light sources with laser light 2 . 40 and 42 is irradiated. The laser light 2 In this case, it is approximately perpendicular to the conversion element 4 while the laser light 40 and 42 are formed approximately V-shaped to each other and obliquely on the conversion element 4 meet, preferably as p-polarized radiation under the Brewster angle of the conversion element. The conversion element 4 Downstream is the cover 8th which is responsible for a respective laser light 2 . 40 . 42 each a scatter area 44 to 48 having. The scattered areas 44 . 46 . 48 are each in local maxima of the luminance of the respective laser 2 . 40 respectively. 42 educated. At the disk edge 14 the cover 8th are the light sensors 22 . 24 intended.

According to 6 has the lighting device 1 the conversion element 4 that from the laser light 2 is irradiated, with downstream of the conversion element 4 a TIR optical element 50 is provided. This has a light entrance side 52 and a light output side 54 , Within the TIR Optic 50 are several scattering areas 56 trained, whereby conceivable would be only a spreading area 56 provided. The light sensors 22 . 24 are in the range of an element margin 58 adjacent to the light output side 54 intended.

According to 7 has the lighting device 1 also the conversion element 4 that from the laser light 2 is irradiated. In the wake of the conversion element 4 is a reflector 60 arranged by the conversion element 4 emitted light 64 towards a lens 62 directs. The Lens 62 has a light input page 66 and a light output side 68 , The pages 66 . 68 are from an element border 70 includes. Approximately in the middle of the lens 62 is a scattering center 72 engraved. Part of the scattered light is from the light sensors 22 . 24 captures the edge of the element 70 assigned. It is conceivable, besides the spreading area 72 to provide additional scattering areas.

In 8th is different from 7 the lighting device 1 shown in addition a headlamp cover 74 for a vehicle headlamp. In contrast to the embodiment in 7 is in the lens 62 no scattered area provided. In contrast, in the headlight cover 74 a variety of scattering areas 76 introduced, of which only one is provided with a reference numeral for the sake of simplicity. However, it is also conceivable here to form only a scatter area. The scattered areas 76 are even in the headlamp cover 74 distributed. They are between a light entrance side 78 and a light output side 80 arranged. A border area 82 between the pages 78 . 80 are the light sensors 22 . 24 assigned by the scattering area 76 detect scattered light.

Disclosed is a lighting device with a light source, via which a conversion element is irradiated, which converts a light wavelength of a portion of the light. The illumination device has an optical element in which at least one scattering area is formed. scattered Light can be detected by at least one light sensor to detect a malfunction of the illumination device. In the event of a fault, the excitation light sources can then be dimmed to a photobiologically harmless intensity level and even switched off completely via an evaluation device connected to the sensor device and a control device connected to the evaluation device. The evaluation device and the control device are in the 1 to 8th not shown.

As excitation light sources laser diodes in the wavelength range around 450 nm are usually used. The illumination device may include one or more laser diodes.

Although the invention has been further illustrated and described in detail by the illustrated embodiments, the invention is not so limited and other variations can be derived therefrom by those skilled in the art without departing from the scope of the invention.

Generally, "on", "an", etc. may be taken to mean a singular or a plurality, in particular in the sense of "at least one" or "one or more" etc., unless this is explicitly excluded, e.g. by the expression "exactly one", etc.

Also, a number may include exactly the specified number as well as a usual tolerance range, as long as this is not explicitly excluded.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• WO 2014/037217 A1 [0002]

Cited non-patent literature

• IEC 62471: 2006 [0025]
• IEC 62471: 2006 [0026]

Claims (13)

Lighting device with at least one light source ( 2 ), which is a conversion element ( 4 ) for converting light wavelengths from one of the light source ( 2 ) emitted light ( 2 ), wherein an optical component ( 8th ) provided in the light path of the at least one light source ( 2 ) emitted light ( 2 ), characterized in that in the optical component ( 8th ) at least one spread ( 16 ) for scattering part of the light ( 2 . 6 ) is introduced in the light path, wherein at least one light sensor ( 22 . 24 ) is provided, with the at least part of the of the scattering area ( 16 ) scattered light ( 18 ) is detectable. Lighting device according to claim 1, wherein the optical component ( 8th ) is designed in such a way and / or the at least one scattering area ( 16 ) in the optical component ( 8th ) is arranged and / or configured such that at least part of the light scattered by the scattering area ( 18 ) is totally reflected in the optical component. Lighting device according to claim 2, wherein at least part of the total reflected light ( 18 ) to a border area ( 14 ) of the optical component ( 8th ). Lighting device according to claim 3, wherein the light sensor ( 22 . 24 ) in the border area ( 14 ) of the optical component ( 8th ) is arranged. Lighting device according to one of the preceding claims, wherein the optical component ( 8th ) is a cover plate or a headlamp cover or a transparent cooling element or a TIR (Total Internal Reflection) -Optikelement or a lens. Lighting device according to one of the preceding claims, wherein the scattering range ( 16 ) by engraving in the optical component ( 8th ) is introduced. Lighting device according to one of the preceding claims, wherein the scattering range ( 16 ) in the region of the greatest luminance in the optical component ( 8th ) is introduced. Lighting device according to one of the preceding claims, wherein a plurality of light sources ( 2 . 40 . 42 ), and for each light source ( 2 . 40 . 42 ) at least one spread ( 44 . 46 . 48 ) is trained. Lighting device according to claim 8, wherein in each local maximum the luminance of a respective light source ( 2 . 40 . 42 ) in the optical component ( 8th ) a respective scatter area ( 44 . 46 . 48 ) is introduced. Lighting device according to one of the preceding claims, wherein a light sensor ( 22 ) for detecting unconverted light and a light sensor ( 24 ) are provided for detecting converted Li cht. Lighting device according to one of the preceding claims, wherein with the light sensor ( 22 . 24 ) a change of a luminous flux in comparison to a reference luminous flux can be determined. Lighting device according to one of the preceding claims, wherein one of the light sensor ( 22 . 24 ) connected evaluation device and connected to an evaluation device control device in case of failure, the light source ( 2 ) is reduced in intensity or switched off. Vehicle headlight with a lighting device according to one of the preceding claims.

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