DE102016113523A1 - Laser light module with a passive protection device to prevent the emission of laser light - Google Patents

Abstract

Disclosed is a laser light module for a motor vehicle headlight, comprising a laser light source and a wavelength converter, which is illuminated by the laser light source with laser light having comparatively short wavelengths. The wavelength converter disperses a part of the emitted laser light and converts another part of the emitted laser light into light having comparatively longer wavelengths. The laser light module has a wavelength-selective diaphragm which is arranged in the light path behind the wavelength converter and covers a beam cross-section which would have the laser light there in the absence of wavelength converter, without covering an area projecting beyond this beam cross-section, and which is a smaller for light of shorter wavelengths Transmission than for light of longer wavelengths. The laser light module has an optical element which is arranged in the light path behind the wavelength-selective diaphragm and is arranged to distribute light transmitted through the wavelength-selective diaphragm over the area illuminated by the laser light module so that a color-homogeneous light distribution is formed there.

Description

The present invention relates to a laser light module for a motor vehicle headlight according to the preamble of claim 1.

Such a laser light module is assumed to be known per se and has a laser light source and a wavelength converter, which is illuminated by the laser light source with laser light having wavelengths from a first wavelength range. The wavelength converter is configured to scatter a part of the emitted laser light and to convert and emit a further part of the emitted laser light into light having wavelengths from a second wavelength range. The wavelengths of the second wavelength range are greater than the wavelengths of the first wavelength range.

In the field of automotive lighting, especially in motor vehicle headlamps, the use of high-performance light sources with the highest possible luminance is desired. As a result, high-intensity lighting devices can be realized with a small space. The radiated light distributions must have certain, usually prescribed by law properties. For the headlights of a motor vehicle usually white light is desired.

With laser light sources, such as semiconductor laser diodes, high radiation performance can be achieved. However, laser light sources emit mostly almost monochromatic, coherent and highly collimated laser light, which can not be used directly in this form as radiated light of the illumination device, and which is also not white.

In this context, the abovementioned wavelength converter serves to convert the monochromatic, coherent laser light into diffuse and largely incoherent white light. Suitable wavelength converters are, in particular, fluorescent dyes. From the DE 10 2012 220 481 A1 and the US 8,400,011 B2 For example, light modules with a laser light source and a fluorescent dye are known. The fluorescent dye is excited by laser light from a first wavelength range for the emission of (fluorescence) light having wavelengths from a second wavelength range. The second wavelengths are larger than the first wavelengths. A mixture of the converted light with laser light scattered in the wavelength-length converter results in the white light required for the headlights.

In this way, the wavelength converter converts the potentially harmful coherent and usually monochromatic laser light into harmless, polychromatic mixed light. In order to distinguish between scattered laser light, which still has the same wavelength as the coherent and monochromatic laser light emanating directly from the laser light source, the latter is also referred to below as direct laser light.

If the headlamp is damaged, such as may occur in an accident, there is a risk that the wavelength converter will be damaged and coherent laser light, ie direct laser light, without being diffused or converted into light of longer wavelengths from the headlamp exit. Therefore, safety devices are required to prevent the leakage of direct and thus coherent, non-scattered laser light.

For this purpose, both active and passive safety devices are known.

Active safety devices detect damage and deactivate the laser if necessary. Examples of such safety devices are known from US 8,400,011 B2 and from the DE 10 2012 220 481 A2 known.

Also known are passive systems that block the not scattered at the wavelength converter or converted there direct laser light by shading. Disadvantages of these safety devices are that they either require additional electronic components such as detectors or that they have a low optical efficiency. In the case of known passive systems, which then block the laser light scattered or converted by the wavelength converter when the wavelength converter is damaged, a portion of the useful light is shaded even with a functional wavelength converter, the shading losses being approximately 20% to 40%.

Against this background, the object of the invention is to specify a robust passive safety system for a laser light module which has a high optical efficiency in the error-free state of the wavelength converter.

This object is achieved with the features of claim 1. In this case, the present invention differs from the light module assumed to be known per se in that the light module has a wavelength-selective diaphragm which is arranged in the light path behind the wavelength converter and covers a beam cross-section which the laser light would have there in the absence of a wavelength converter, without a To cover over this beam cross-section projecting surface, and for light from the first Wavelength range has a smaller transmission than for light from the second wavelength range. Another difference consists in that the laser light module has an optical element which is arranged in the light path behind the wavelength-selective diaphragm and is arranged to distribute light transmitted through the wavelength-selective diaphragm over the area illuminated by the laser light module so that there a color-homogeneous light distribution arises.

The smaller transmission for the light from the first wavelength range, that is to say for the laser light, causes coherent laser light, which could emerge unattenuated from the laser light module in the event of a damaged or missing wavelength converter, being shaded by the wavelength-selective diaphragm and thus at least attenuated.

At the same time, with an undamaged wavelength converter, fluorescent light incident on the wavelength-selective diaphragm is not attenuated or at least less strongly attenuated, so that this light can still contribute to the generation of a desired light distribution. This limits losses in the optical efficiency (ratio of the total useful light power contributing to the light distribution to the light output of the laser light source).

A preferred embodiment is characterized in that the wavelength converter with respect to its laser light scattering and converting properties is adapted only to generate together with the light transmitted through the wavelength selective iris and deflected by the optical element, the required white light for headlamps.

It is also preferable that the transmission of the wavelength-selective diaphragm for light from the first wavelength range is negligibly small, in particular less than 1%.

A further preferred embodiment is characterized by a beam-forming optical system arranged in the light path of the laser light, which focuses the laser light emitted by the laser light source onto the wavelength converter.

It is also preferred that the wavelength converter is fastened by a carrier component in the light module and that the wavelength-selective diaphragm is rigidly connected to the carrier component.

A further preferred refinement is characterized in that the wavelength-selective diaphragm is a part of a bracket projecting from the carrier component parallel to the main emission direction of the wavelength converter and projecting into the second solid angle region transversely to the main emission direction.

Furthermore, it is preferred that the bracket has a transparent substrate, which is covered with a dichroic material.

A further preferred embodiment is characterized in that the dichroic filter is a dielectric multilayer coating.

It is also preferred that the wavelength-selective diaphragm consists of transparent material into which a diffraction structure is impressed which diverts or scatters light incident on wavelengths from the first wavelength range.

Furthermore, it is preferred that the optical element is a lens that distributes the light transmitted through the wavelength-selective aperture through the area illuminated by the laser light module such that a color-homogeneous light distribution is formed there.

A further preferred refinement is characterized in that the optical element is a reflector which has a reflector facet which distributes light transmitted through the wavelength-selective diaphragm over the area illuminated by the laser light module such that a colorually homogeneous light distribution is formed there.

Further advantages will be apparent from the dependent claims, the description and the attached figures.

It is understood that the features mentioned above and those yet to be explained below can be used not only in the particular combination given, but also in other combinations or in isolation, without departing from the scope of the present invention.

Embodiments of the invention are illustrated in the drawings and are explained in more detail in the following description. In this case, the same reference numerals in different figures denote the same or at least functionally comparable elements. In each case, in schematic form:

1 an embodiment of a motor vehicle headlight according to the invention;

2 a further embodiment of a motor vehicle headlight according to the invention; and

3 constructive details of a light module of a motor vehicle headlight according to the invention.

In detail, the shows 1 a motor vehicle headlight 10 with a housing 12 , whose light exit opening from a transparent cover 14 is covered. Inside the case 12 there is a laser light module 16 , The laser light module 16 has a laser light source 18 on, which is used to emit laser light 20 is arranged, which has wavelengths from a first wavelength range.

The laser light source 18 is preferably a laser diode. The laser light source 18 emits the laser light 20 in a first solid angle area. The laser light 20 has wavelengths from a first wavelength range that includes, for example, wavelengths of or blue light.

An optional beam shaping optics 24 , which is realized here as a lens, but can also be a reflector or a catadioptric optics, directed in the first solid angle range 22 emitted laser light 20 to one in the light path of the laser light 20 arranged wavelength converter 25 , If the laser light source, the laser light already in a sufficiently narrow solid angle 22 focused radiates, can on the first beam shaping optics 24 be waived.

The wavelength converter 25 has a fluorescent dye which, upon excitation by the laser light 20 a part of the laser light 20 emitted in fluorescent light with wavelengths from a second wavelength range and the parallel to a further portion of the laser light 20 scatters. The second wavelength range is, for example, the range of wavelengths of yellow-red light. Overall, this is the wavelength converter 25 yellowish white, white, or blue-white mixed light, depending on how large the proportions of the yellow-red fluorescent light and the only scattered laser light on the mixed light. The fluorescent dye, for example, adheres to a transparent substrate and consists of phosphorus or a phosphorus compound, each with embedded scattering particles.

The mixed light is emitted in a wide solid angle, wherein the main emission corresponds to the direction of the incident laser light. The solid angle filled by the mixed light is determined by the solid angle in which propagates the preferably scattered in the direction of incidence laser light, since the fluorescent light without special preferential direction and thus wider than the scattered light is emitted. It is essential that the solid angle of the white mixed light, resulting in functional wavelength converter 25 results, is substantially wider than the optionally reduced by the first beam-forming optical beam beam cross section of the laser light 20 that is in the absence of wavelength converter 25 would result.

The light module 16 has a wavelength-selective aperture 26 in the light path behind the wavelength converter 25 is arranged. The wavelength-selective iris 26 is in the illustrated embodiment on a substrate 28 attached, which is transparent to light from both wavelength ranges.

The wavelength-selective iris 26 is arranged and dimensioned to cover a beam cross section that the laser light 20 would have there in the absence of wavelength converter, without covering an area projecting beyond this beam cross-section. More precise values for arrangement and dimensioning depend on the opening angle of the laser light beam and the geometry of the light module 16 and can by a person skilled in the art for a given light module 16 and laser light beams are easily detected. This dimensioning and arrangement has the consequence that the wavelength-selective aperture 26 the laser beam that inadvertently missing or damaged wavelength converter 25 has only a comparatively small opening angle and is accordingly highly concentrated, accurately covers

In this coverage area, the wavelength-selective iris has 26 for light from the first wavelength range, ie for the laser light 20 , a smaller transmission than for light from the second wavelength range. This means that the wavelength-selective aperture 26 in the event of a fault, the missing or damaged wavelength converter 25 At least attenuates the incident laser beam.

On the other hand, the accuracy of fit of the cover, so the fact that the wave-selective aperture 26 covers only the laser beam and does not protrude substantially beyond the beam cross section of the laser beam, the non-error case desired consequence that the scattered laser light component of the wavelength converter 25 outgoing white mixed light only in the comparatively small solid angle, through the wavelength-selective aperture 26 is covered, is weakened. It is preferred that the transmission of the wavelength-selective aperture 26 for light from the first wavelength range, ie for the laser light, is negligible. This achieves maximum passive safety. Under a tailor-made cover is in one embodiment, even a size of the aperture 26 understood, which is so much larger than a beam cross-section, as it is for Interception of tolerances of the primary beam direction of the laser is required.

This property, or more generally, the lower transmission of light having wavelengths from the first wavelength range in comparison with the transmission of light having wavelengths from the second wavelength range is achieved in one embodiment in that the wavelength-selective diaphragm 26 a transparent substrate for both wavelength ranges 28 which is covered with a dichroic filter. Such a dichroic filter is in one embodiment a dielectric multilayer.

In an alternative embodiment, the wavelength-selective diaphragm exists 26 made of transparent material, in which a diffraction structure is impressed, which deflects or scatters incident wavelengths from the first wavelength range out of the useful light bundle.

In the embodiment shown in the 1 is shown, the light module has 16 an undamaged wavelength converter 25 which emits the white mixed light in a wide solid angle range, which is substantially larger than that of the wavelength-selective aperture 26 covered solid angle is. In the 1 This situation is caused by mixed light components 30a . 30b and 30c shown. The mixed light components 30a and 30c correspond to the mixed light, the at the wavelength-selective aperture 26 propagated past and from an optical element 32 that in the case of 1 a condenser lens 34 is in front of the headlight 10 lying lighting zone 36 is directed by the headlight 10 , or from the light module 16 of the headlight 10 to be illuminated.

The mixed light component 30b meets the wavelength-selective iris 26 , While the yellow-red fluorescent light component of the mixed light component 30b essentially without weakening by the wavelength-selective diaphragm 30b passes through, the scattered light component having wavelengths from the first wavelength range experiences at least one attenuation at this mixed light. As a result, the residue passed through the wavelength-selective aperture has 30d of the mixed light portion 30b behind the wavelength-selective aperture 26 a light color that is shifted from white to yellow-red. This can cause the lighting zone 36 is inhomogeneously illuminated with respect to the color of the illuminating light, which is undesirable.

To prevent or at least mitigate this undesirable effect is the optical element 32 that in the light path behind the wavelength-selective iris 26 is arranged, adapted to distribute through the wavelength-selective aperture transmitted light so over the illuminated by the laser light module surface, ie on the lighting zone, that there is a homogeneous color light distribution.

For this purpose, that is in the 1 illustrated optical element 32 a freeform lens 34 that at least a first zone 38 and a second zone 40 having. The first zone 38 is a central zone. This central zone 38 is in the light module 16 arranged so that they are with the light 30d is illuminated, with functional wavelength converter 25 through the wavelength-selective aperture 26 has passed through. This central zone 38 is further adapted to be dependent on the wavelength-selective aperture 26 her striking light 30d over the entire lighting zone 36 to distribute.

The second zone 40 one is the central zone 38 surrounding peripheral zone. This peripheral zone 38 is in the light module 16 arranged so that they are with the light 30a . 30c is illuminated, with functional wavelength converter 25 at the wavelength-selective aperture 26 propagated past. This peripheral zone 40 is further adapted to the white mixed light impinging upon it 30a . 30c over the entire lighting zone 36 to distribute.

The result is the different colored light components 30a . 30b . 30c in the lighting zone 36 mixed together, so that there is a homogeneous light color of the lighting.

2 shows an embodiment in which the optical element 32 a reflector 42 is. Except for the realization of the optical element 32 as a reflector 42 in place of a realization as a lens 34 and the following differences in the beam paths, the embodiment of the differs 2 not from the embodiment of 1 so the description for 1 in this respect also for the 2 applies. This reflector 42 has a reflector facet 44 on through the wavelength-selective aperture 26 passed through light 30d so about the laser light module 16 distributed illuminated surface that there creates a homogeneous color light distribution.

The reflector 42 points, like the lens 34 , at least a first zone and a second zone 46 on. The first zone is the already mentioned facet 44 , This facet 44 is arranged in the light module so that it is in contact with the light 30d is illuminated, with functional wavelength converter 25 through the wavelength-selective aperture 26 has passed through. This facet 44 Zone is also set up on top of it wavelength-selective aperture 26 her striking light 30d over the entire lighting zone 36 to distribute.

The second zone 46 one is the central zone, or the facet 44 surrounding peripheral zone. This peripheral zone 46 is in the light module 16 arranged so that they are mixed with the light 30a . 30c is illuminated, with functional wavelength converter 25 at the wavelength-selective aperture 26 propagated past. This peripheral zone 46 is also adapted to the light impinging on it over the whole lighting zone 36 to distribute.

As a result, so are the reflector 42 the different colored light components in the lighting zone 36 mixed together, so that there is a homogeneous light color of the lighting.

Depending on the thickness of the wavelength converter and the density of the distribution of the scattering centers of the wavelength converter, this generates from the incident laser light 20 more scattered light at the expense of the fluorescent light component or more fluorescent light at the expense of the scattered light component. As a result, the color of the mixed light can be within certain limits by varying the thickness of the wavelength converter 25 and the density of the distribution of its scattering centers.

A preferred embodiment is characterized in that the wavelength converter 25 in terms of his laser light 20 scattering and converting properties is set up together with the through the wavelength-selective iris 26 transmitted through and from the optical element 32 deflected light that for headlights 10 to produce required white light. This through the wavelength selective iris 26 transmitted light through 30d has a lower blue content and larger yellow-red content, while the light propagating past the filter 30a . 30c the opposite is true. It is therefore advantageous to change the color of the wavelength-selective iris 26 light to propagate something blue-white to the result in the desired white light color in the lighting zone 36 to achieve.

3 shows structural details of another embodiment of a motor vehicle headlight according to the invention 10 ,

The wavelength converter 25 is by a carrier component 48 in the light module 16 attached. The wavelength-selective iris 26 is preferred on the carrier component 48 attached. The wavelength-selective iris 26 is arranged so that it is parallel to the main radiation direction 50 of the wavelength converter 25 from the carrier component 48 protrudes and transverse to the main emission direction 50 of the wavelength converter 25 in the from the wavelength converter 25 in the from the wavelength converter 25 or, if there is no wavelength converter 25 , from the laser light source 18 outgoing light beam protrudes. The wave-selective iris 26 has the shape of a bracket in this embodiment 52 own, the one side of the support member 48 protrudes.

The coat hanger 52 has a transparent substrate with a dichroic material as the wavelength-selective aperture 26 is occupied. The dichroic material is preferably a dielectric multilayer.

In an alternative embodiment, the wavelength-selective diaphragm exists 26 made of transparent material, in which a diffractive structure is impressed, which diverts or scatters light incident on wavelengths from the first wavelength range.

On the support component 48 is preferably also the laser light source 18 and also the optional beam shaping optics 24 attached. On the beam shaping optics 24 may be omitted, for example, when the laser light source 18 her laser light 20 already in a sufficiently small solid angle range 22 emitted.

In the embodiment shown in the 3 is shown, the white mixed light through an optical element 32 , this is a reflector 42 is, collected and through the transparent cover 14 through in front of the headlight 10 lying lighting zone deflected.

In an alternative formulation, the invention relates to a laser light module for a headlamp, comprising a laser light source for emitting laser light having wavelengths from a first wavelength range, in a first solid angle range, with a wavelength converter arranged in the light path of the laser light, which is adapted to a part of the laser light emitted in the first solid angle range to scatter in a second solid angle range and to convert a further part of the light emitted in the first solid angle range into light having wavelengths from a second wavelength range and to emit converted light in the second solid angle range, wherein the wavelengths of the second wavelength range are greater than the wavelengths of the first wavelength range. The laser light module is characterized in that a wavelength-selective diaphragm which has a smaller transmission for light from the first wavelength range than for light from the second wavelength range, in the second solid angle range is arranged such that it covers directions of incidence from which laser light emitted by the laser light source into the first solid angle range would invade the second solid angle range in the case of a defective or missing wavelength converter and in that the laser light module has an optical element which is arranged in the light path behind the wavelength-selective diaphragm and configured to redirect light transmitted through the wavelength-selective diaphragm with wavelengths from the second wavelength range such that the deflected light mixes with light from beam paths that pass from the wavelength converter at the wavelength-selective diaphragm.

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

• DE 102012220481 A1 [0005]
• US 8400011 B2 [0005, 0009]
• DE 102012220481 A2 [0009]

Claims (11)

Laser light module ( 16 ) for a motor vehicle headlight ( 10 ), with a laser light source ( 18 ) and a wavelength converter ( 25 ) coming from the laser light source ( 18 ) with laser light ( 20 ) having wavelengths from a first wavelength range, wherein the wavelength converter ( 25 ) is arranged to scatter a portion of the emitted laser light and to convert and emit another portion of the emitted laser light into light having wavelengths from a second wavelength range, wherein the wavelengths of the second wavelength range are greater than the wavelengths of the first wavelength range, characterized in that the light module ( 16 ) a wavelength-selective diaphragm ( 26 ) in the light path behind the wavelength converter ( 25 ) is arranged and covers a beam cross section, the laser light ( 20 ) there with missing wavelength converter ( 25 ), without covering an area projecting beyond this beam cross section, and which has a smaller transmission for light from the first wavelength range than for light from the second wavelength range, and that the laser light module ( 16 ) an optical element ( 32 ) located in the light path behind the wavelength-selective diaphragm ( 26 ) is arranged and is adapted, through the wavelength-selective aperture ( 26 ) through the transmitted light from the laser light module ( 16 ) to distribute the illuminated surface that creates a homogeneous color distribution there. Laser light module ( 16 ) according to claim 1, characterized in that the wavelength converter ( 25 ) is arranged with respect to its laser light scattering and converting properties, only together with the wavelength-selective aperture ( 26 ) and transmitted by the optical element ( 32 ) deflected light to produce the required for headlights white light. Laser light module ( 16 ) according to one of the preceding claims, characterized in that the transmission of the wavelength-selective diaphragm ( 26 ) is negligible for light from the first wavelength range, in particular less than 1%. Laser light module ( 16 ) according to one of the preceding claims, characterized by a beam shaping optical system arranged in the light path of the laser light ( 24 ) emitted by the laser light source ( 18 ) outgoing laser light ( 20 ) concentrated on the wavelength converter. Laser light module ( 16 ) according to one of the preceding claims, characterized in that the wavelength converter ( 25 ) by a carrier component ( 48 ) is mounted in the light module and that the wavelength-selective diaphragm ( 26 ) rigidly with the carrier component ( 48 ) connected is. Laser light module ( 16 ) according to claim 5, characterized in that the wavelength-selective diaphragm ( 26 ) a part of a parallel to the main radiation direction ( 50 ) of the wavelength converter ( 25 ) from the carrier component ( 48 ) outstanding and transverse to the main radiation direction ( 50 ) in the second solid angle area projecting bracket ( 52 ). Laser light module ( 16 ) according to claim 6, characterized in that the bracket ( 52 ) has a transparent substrate coated with a dichroic material. Laser light module ( 16 ) according to claim 7, characterized in that the dichroic filter is a dielectric multilayer. Laser light module ( 16 ) according to one of claims 1 to 6, characterized in that the wavelength-selective diaphragm ( 26 ) is made of transparent material, in which a diffractive structure is impressed, which diverts or scatters light incident on wavelengths of the first wavelength range. Laser light module ( 16 ) according to one of the preceding claims, characterized in that the optical element ( 32 ) a lens ( 34 ) through the wavelength-selective aperture ( 26 ) through the transmitted light from the laser light module ( 16 ) distributes the illuminated surface so that a homogeneous, homogeneous light distribution is created there. Laser light module ( 16 ) according to claim 1 or 2, characterized in that the optical element ( 32 ) a reflector ( 42 ), which is a reflector facet ( 44 ) through the wavelength-selective diaphragm ( 26 ) through the light emitted by the laser light module ( 16 ) distributes the illuminated surface so that a homogeneous, homogeneous light distribution is created there.

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