EP2825818B1 - Light guiding element for a laser vehicle headlight - Google Patents

Description

The invention relates to a laser vehicle headlight with a light guide element for a laser vehicle headlight according to claim 1.

Various types of vehicle headlights are known in the prior art, with headlamps with discharge lamps and halogen light sources being used in recent years predominantly. For energy saving reasons and to further reduce the space requirement of vehicle headlamps, the use of laser light sources such as semiconductor lasers is being increasingly tested, since they are advantageous in this regard. In order to make the laser light usable for a vehicle headlight, a light source, a so-called phosphor converter (eg a phosphorus compound, a YAG crystal with cerium doping, etc.), is irradiated with a laser light source, thereby radiating visible light is stimulated. The phosphor converter thus converts laser light into light of other wavelengths.

In this case, free-jet concepts are frequently used in which the laser light source is arranged at a distance from the luminous element and the laser light travels a free path before impinging on the luminous element. In such a case, it is necessary that the laser light impinges exactly on the luminous element - on the one hand, in order to exploit the radiated power as well as possible, on the other hand for safety reasons. The laser light sources used emit powers of currently up to 3 W and more, in the case of a malfunction (for example, if the light element is not optimally hit) may result from high-intensity eye-damaging laser light radiation to injuries, but in any case to endanger other road users.

US 2011/0292636 A1 discloses a generic laser vehicle headlamp with a light guide for a laser vehicle headlamp.

It is therefore an object of the invention to provide a solution for laser vehicle headlights which overcomes the above-mentioned problems of the prior art.

This object is achieved with an aforementioned laser vehicle headlamp with a light guide for a laser vehicle headlamp according to the invention that the luminous element is arranged in the light guide and that the limiting element is applied to the light guide.

The invention allows the compensation of positioning errors of the luminous element with respect to the laser light source and ensures even with slight deviations that the irradiated laser light hits the luminous element and is not distracted uncontrolled or possibly endanger other road users. The in the mounted state of the laser light source facing the light entry surface is larger than the light exit surface and thus collects the incoming radiation, which are directed by the reflective inner surface to the light emitting element.

Thanks to the solution according to the invention, both the high demands on the mounting of the luminous element relative to the laser light source can be reduced and thereby fulfilled, as well as the dimensional stability of the parts used in a laser vehicle headlamp during use (eg vibration load, resonance, strength, thermal expansion, ...) be ensured.

The inner surface here designates the interior (or the one oriented in the direction of the light-guiding element interior) of the lateral surface between the light entry surface and the light exit surface. By way of example, the light-guiding element has a substantially circular cross-section, that is, the light-entry surface has a larger diameter than the light-emitting surface. The light-guiding element preferably consists of a transparent material such as glass or plastic - the light-guiding element is embodied, for example, in one piece as a volumetric body, that is to say it consists of a material throughout. The reflective inner surface results in particular due to the total reflection at the interface light guide element environment.

In a variant of the invention, the acceptance angle of the light-guiding element is between 0 ° and 45 ° with respect to the optical axis of the light-guiding element. This means that the light-guiding element is set up to reflect or concentrate light which impinges on the light-entry surface at an angle between 0 ° and 45 ° with respect to the optical axis, in the direction of the light-exit surface. Thus, the light guide according to the invention allows high tolerances with respect to the positioning of the laser light source and the luminous element to each other.

The reflective inner surface of the light-guiding element is designed essentially as a paraboloid or as a free-form surface. The formation as a paraboloid can in particular also take the form of a paraboloid of revolution. Depending on the exact application, the inner surface is thus shaped with the desired reflection properties.

When using the light-guiding element in a vehicle headlight, it is advantageous if no unwanted false light is emitted, which could then falsify the light image. For this purpose, the outside of the light-guiding element in the region between the light-entry surface and the light-emitting surface is expediently provided at least in regions, but in particular completely, with an opaque coating. This can be prevented that light is emitted off the light exit surface of the light guide. The coating can be applied for example by painting or steaming.

In the invention, at least one receptacle for the luminous element is provided in the region of the light exit surface, wherein the receptacle is designed in particular as a blind hole or as a hollow completely surrounded by the light guide element. The lighting element is thus arranged in the light guide. This has the advantage that during assembly, only the light guide element with respect to the laser light source must be accurately mounted - the optimal position of the light-emitting element is thus ensured at the same time, since the light-emitting element is held in the light guide. When carrying out the recording as a blind hole, the lighting element can be replaced if necessary, the light guide can continue to be used. When executed as a completely surrounded cavity, the light-emitting element can be protected from environmental influences. By providing the receptacle, the luminous element is arranged in the mounted state "below" the light exit surface in the light guide.

With the solution according to the invention also different light functions can be realized. According to the invention, the light exit surface is at least partially covered by an opaque limiting element. This opaque limiting element may for example be designed as a coating in the form of painting or vapor deposition, but it may also be a separate component glued or otherwise applied. This limiting element (possibly in conjunction with a free-form reflector surface - see below) can be used to produce a dipped beam with a sharp light-dark transition.

According to a further variant of the invention, at least one reflector element extending around the light guide element is arranged between the light entry surface and the light exit surface, preferably in the area of the light exit surface, for deflecting the light emitted by the light element in a direction away from the light entry surface. With this reflector element, the light emitted by the luminous element can be used photometrically - e.g. in connection with the above-mentioned limiting element for the realization of a low beam. In principle, such a reflector element is advantageous because, for example, when using the light-guiding element in a vehicle headlight, the light emitted by the light-emitting element can be optimally directed into a main reflector of the vehicle headlight. At the same time an uncontrolled leakage of light from the headlight is prevented, or a better utilization of the light emitted by the light emitting element possible.

The object of the invention is further achieved by an aforementioned vehicle headlamp according to the invention in that between the laser light source and the luminous element is arranged at least one light guide element as described above. Conveniently, the laser light source is arranged in the main emission direction of the vehicle headlamp in front of the luminous element, so that the light of the laser light source is emitted counter to the main emission direction of the vehicle headlamp. In this variant, in particular the risk of uninvolved road users by the laser beam is prevented when it comes to a malfunction of the headlight - because the laser beam runs counter to the main beam direction, he can not radiate uncontrolled from the headlight. The invention allows the realization of a vehicle headlamp, which can meet the legal requirements such as ECE, SAE, CCC, etc.

As an additional security element, according to a variant of the invention, at least one diaphragm element is provided, with which light reflected from the light entry surface of the light guide element or from the interior of the light guide element in the main emission direction of the vehicle headlamp can be shielded. In a further variant of the invention, the diaphragm element is designed as a connecting piece running between the laser light source and the light-guiding element, which is designed in particular as a tubular or semi-tubular shape.

With the diaphragm element, the radiation can be prevented in particular from laser light in the direction outside of the vehicle headlight. For this purpose, the diaphragm element can be coated, for example, with an anti-reflective or absorbent coating, or it can surround the relevant regions of the light-guiding element.

• Fig. 1 eine Querschnittsansicht einer ersten Variante des erfindungsgemäßen Lichtleitelements;
• Fig. 2 eine Querschnittsansicht einer zweiten Variante des erfindungsgemäßen Lichtleitelements;
• Fig. 3 eine Querschnittsansicht einer dritten Variante des erfindungsgemäßen Lichtleitelements; und
• Fig. 4 eine Querschnittsansicht eines Fahrzeugscheinwerfers mit einem erfindungsgemäßen Lichtleitelement.

In the following the invention will be explained in more detail with reference to a non-limiting embodiment, which is illustrated in the drawing. In this shows schematically:

• Fig. 1 a cross-sectional view of a first variant of the light guide element according to the invention;
• Fig. 2 a cross-sectional view of a second variant of the light-guiding element according to the invention;
• Fig. 3 a cross-sectional view of a third variant of the light-guiding element according to the invention; and
• Fig. 4 a cross-sectional view of a vehicle headlamp with a light guide according to the invention.

In the following figures, the same elements are provided with the same reference numerals for reasons of clarity.

In Fig. 1 a first variant of the light-guiding element 1 according to the invention is shown. The light guide 1 comes in a laser vehicle headlight 2 (see

Fig. 4 ) is used, between a laser light source 3 and a luminous element 4, which is excited by the incident light from the laser light source 3 for the emission of visible light in particular white color.

The light guide 1 has a light entrance surface 5 and a light exit surface 6. The inlet cross-sectional area of the light entry surface 5 is greater than the exit cross-sectional area of the light exit surface 6 - if, for example, as in the present embodiment, the light guide 1 has a substantially circular cross-section, so the entrance surface radius 50 is greater than the exit surface radius 60th

Irradiated light (from the laser light source 3) is focused on the running between the inlet 5 and the exit surface 6 inner surface 7 to the light exit surface 6 out. This is done predominantly by total reflection at the interface between the light guide 1 and the surrounding medium, which is predominantly ambient air. In the area of the light exit surface 6 is then the luminous element 4 (see Fig. 4 ), which is excited by the collimated laser light to emit visible, preferably white light.

The incident light does not have to impinge perpendicularly on the light entry surface 5, but can be noticed within an acceptance angle 300. The acceptance angle 300 denotes the angle to the optical axis 100 of the light guide 1. An acceptance angle of 0 ° results when the light exactly parallel to the optical axis 100 (and thus perpendicular to the light entrance surface 5) is incident. The acceptance angle 300 is in the present embodiment between 0 ° and 45 °.

Light incident under this acceptance angle range (that is, between 0 ° and 45 °) is converged toward the light exit surface 6. Light incident at an angle greater than the acceptance angle is either reflected directly at the light entry surface 5 or enters the light guide element 1, but is then reflected back and forth so that it exits again at the light entrance surface 5 and not the light exit surface 6 reached.

The light guide 1 thus increases the tolerances with which the light of the laser light source 3 (see Fig. 4 ) to the luminous element 4 ( Fig. 4 ) irradiates and thus facilitates the one hand, the construction of a laser vehicle headlamp 2, on the other hand, the vibrations occurring during operation are less significant.

In order to achieve the bundling effect, the inner surface 7 of the light-guiding element 1 is designed essentially as a paraboloid or as a free-form surface. Furthermore can, as in Fig. 1 illustrated, the outside of the light guide 1 in the region between the light entrance surface 5 and the light exit surface 6 with an opaque and / or reflective coating 8 may be provided. This coating 8 may cover the specified area in areas or even completely.

As a result, on the one hand, the reflective or bundling effect of the inner surface 7 is amplified, on the other hand, no misdirected laser radiation can emerge from the light guide element, which could lead to injuries in uninvolved road users. The coating 8 is designed, for example, as a coating, vapor deposition or form-fitting envelope.

In principle, the light-guiding element 1 can be tube-shaped, that is to say hollow, but it can also be made as a one-piece volumetric body. The material used is various transparent materials such as glass, plastic, etc. in question.

In the area of the light exit surface 6, a receptacle for a luminous element 4 is provided. In the illustrated embodiments, only one receptacle for a luminous element 4 is provided, but it can also be provided receptacles for several lighting element 4, or several lighting elements 4 are spent in a recording. In Fig. 1 is the receptacle for the light-emitting element 4 designed as a blind hole 9, the variant in Fig. 2 provides a completely surrounded by the light guide 1 cavity 10 before.

The luminous element 4 is struck by the collimated laser light and excited to emit visible light. This visible light then exits the light guide 1 and can be used in lighting technology, in a laser vehicle headlamp 2, as in Fig. 4 is shown and explained in more detail.

In Fig. 2 is apparent according to the invention as the light exit surface 6 is at least partially covered by an opaque limiting element 15. In the illustrated embodiment, the limiting element 15 is below a plane passing through the optical axis 100 horizontal plane (the horizontal plane extends in Fig. 2 perpendicular to the plane of the page and therefore coincides with the dot-dash line of the optical axis 100). Of course, other versions are possible depending on the desired light function.

The delimiting element 15 can be of any desired design, for example as an opaque coating or as a separate diaphragm which is adhesively bonded or otherwise applied to the light guiding element 1 or held mechanically thereon. The limiting element 15 allows the generation of a light-dark transition, whereby various light functions such as low beam, fog light, etc. can be realized.

The mentioned light-dark transition can be achieved by the in Fig. 3 Therein, the light-guiding element 1 has a reflector element 11 running around the light-guiding element 1, which deflects the light emitted by the light-emitting element 4 in a direction away from the light-entry surface 5. Thus, the radiated light from all sides of the light-emitting element 4 can be used even better in terms of lighting technology. The reflector element 11 is designed for example as a half-shell (only the upper or lower half is present) or as a full reflector.

The reflector element 11 is either designed in one piece with the light guide 1 or designed as a separate component. In the second case, it consists for example of metal, plastic or glass, wherein the light-emitting element 4 facing side reflective, that is designed to be coated accordingly. If the reflector element 11 is embodied in one piece with the light-conducting element 1, it must be ensured that no light can escape in the direction of the light-entry surface 5 - the reflective layer is therefore thick enough, or is an opaque layer on the side facing away from the light-emitting element 4 applied.

In principle, the reflector element 11 is to be arranged between the light entrance 5 and the light exit surface 6, but is preferably located, as in the present exemplary embodiment, in the region of the light exit surface 6.

In Fig. 4 is finally a vehicle headlight 2 in a sectional view in cross section to see in which an inventive light guide 1 is used. Only the essential features for the understanding of the invention are shown, since those skilled in the other elements of a vehicle headlamp are known.

The vehicle headlight 2 comprises a laser light source 3 which, for example, in a wavelength range between 200 nm and 450 nm, that is partially in the non-visible UV range, radiates. The radiated power of the laser light source 3 is between 0.5 and 2 W, but may be higher. The laser light source 3 is, for example, a semiconductor laser in the form of a laser diode. It is also possible to provide a plurality of laser light sources 3, for example in the form of laser diode arrays.

The laser light source 3 has to dissipate the heat generated during operation in the illustrated embodiment, a heat sink 12 and a ventilation device 13 - the ventilation device 13 serves here, the cooling body 12 to supply cool air or dissipate heated air. The ventilation device 13 may, for example, comprise a ventilation device. The heat sink 12 may be made of a suitable material and in addition, for example, cooling fins or the like. exhibit.

In addition to the laser light source 3 (in Fig. 4 shown with heat sink 12 and fan 13), a luminous element 4 is provided which is spherical in the present embodiment. The spherical design is only one of several possible configurations, the light-emitting element 4 can also be designed differently. The luminous element 4 is preferably a phosphor converter, which can be excited by the light of the laser light source 3 in a known manner to emit visible light. In principle, all materials which convert monochromatic laser light into light of other wavelengths (preferably white light) can be used as the phosphorus converter. In principle, the phosphorus converter is thus a light converter - the electrons of the converter material are excited by the laser light into higher energy levels and emit light when falling back the wavelength difference corresponding to the level difference.

The luminous element 4 is arranged in a light-guiding element 1 according to the invention, which is positioned in a reflector 16. The reflector 16 directs the light emitted by the luminous element 4 in the main emission direction 200 of the vehicle headlight 2. The main emission direction 200 extends in the present example in FIG Fig. 4 left to right. The reflector 16 may be arranged to be pivotable and / or adjustable, which is not shown in the figures for reasons of clarity. In principle, any desired embodiments of the reflector 16 are possible; free-form variants as well as parabolas, hyperbolas, ellipses or combinations thereof can be used as the reflector surface. The reflector 16 is in Fig. 4 as a cross section and can be used as a half shell (only the upper or lower half is present) or executed as a full reflector, the skilled person a number of variants for the reflector 16 is known.

In the illustrated variant of the invention, the luminous element 4 is arranged on the optical axis 400 of the vehicle headlight 2 in a focal point of the reflector 16. It should be noted that the reflector 16 may also be designed as an open-space reflector with a plurality of different focal points, wherein according to the illustrated embodiment, the luminous element 4 is arranged precisely in one of these focal points. Of course, it is not absolutely necessary that the light-emitting element 4 is arranged in a focal point - but it must remain stationary to achieve a desired light distribution in the reflector, which should be ensured even when shaken. The vehicle headlight 2 is closed by a cover 17. The cover 17 may be configured as desired, but is preferably largely transparent.

The desired light pattern of the vehicle headlight 2 is generated by the light guide element 1, the luminous element 4 arranged therein and the reflector 16. In addition, the light guide 1 according to the invention allows greater tolerances with respect to the relative positioning between the laser light source 3 and light element 4, for example when the light source 3 is replaced due to repair or if the laser light source 3 is no longer in optimal position due to vibrations during operation.

For fixing the light guide 1 in the reflector 16, a support member 18 is provided - the support member 18 is here provided with cooling fins 19, which serve to derive the resulting in the light generation in the light element 4 and the light guide 1 heat. The cooling fins 19 are just one example of heat sinks that can be used here - a number of possibilities are known to those skilled in the art in this regard, so will not be discussed in detail here.

The laser light source 3 and the luminous element 4 are arranged so that the light of the laser light source 3 is emitted against the main emission direction 200 of the vehicle headlamp 2. The laser light source 3 is thus arranged in the main emission direction 200 of the vehicle headlamp 2 in front of the luminous element 4, so that the light of the laser light source 3 is emitted counter to the main emission direction 200 of the vehicle headlamp 2. The beam direction 500 of the laser light source 3 thus runs opposite to the Main emission direction 200 of the vehicle headlight 2. This prevents that in the event of damage to the vehicle headlight 2 or a malfunction, the light of the laser light source 3 escape and may endanger other road users.

The beam direction 500 of the laser light source 3 preferably extends at an acute angle to the main emission direction 200 of the vehicle headlight 2. The angle can therefore be between 0 ° and 90 °. An angle of 0 ° thus means that the laser light source 3 is arranged on the optical axis of the vehicle headlight 2 in the main beam direction 200 behind the light-emitting element 4. Accordingly, an angle of 90 ° means that the beam direction 500 of the laser light source 3 is normal to the optical axis of the vehicle headlight 2. Optical axis and main emission direction 200 of the vehicle headlight 2 are substantially parallel to each other. Depending on the available installation space for the vehicle headlight 2 or the desired field of application, therefore, light source 3 and light-guiding element 1 or light-emitting element 4 can be arranged relative to one another.

Between the laser light source 3 and the light guide 1 with the luminous element 4, a number of elements can be arranged. For example, in the illustrated embodiment according to Fig. 4 an optical element in the form of a collecting lens element 20 is arranged immediately after the laser light source 3. This convergent lens concentrates the light of the laser light source 3 in the direction of the light-guiding element 1 or of the luminous element 4 arranged therein. Of course, any other optical elements may also be used, for example lenses and / or prisms of various kinds.

Conveniently, absorbing elements are arranged around such optical or light-guiding elements 1 in order to prevent any reflections of the incoming laser light in the main emission direction 200 of the vehicle headlight 2 and thus endanger other road users. The aperture element 21 in Fig. 4 represents an embodiment of such elements. It prevents radiation of reflections from the vehicle headlight 2 out. In a variant or in addition, the said optical, light-guiding elements 1 and absorbing elements such as the diaphragm element 21 may also be provided with anti-reflective surfaces or be designed so that they only reflect or absorb light in the wavelength range of the laser light, but translucent for visible light are executed and thus have a look at the headlight components allow. In this case, irregularities such as inclusions or microstructures can be provided, which deflect the laser light, make visible from the outside and thus serve as a design element.

By way of example, the diaphragm element 21 in FIG Fig. 4 arranged above a horizontal plane extending through the optical axis 400 of the vehicle headlight 2 between the light guide 1 and the cover 17. Of course, however, other known to those skilled solutions - the only requirement of such devices is that the light functions of the vehicle headlamp 2 are not adversely affected.

The diaphragm element 21 can also be designed so that it covers the entire free-jet region of the laser light, for example in the form of a tube or a tube with a semicircular cross-section ("half-pipe"). In a further variant, it may be semi-mirrored and / or illuminated for design reasons with its own light source (e.g., a blue LED). Such variants are not shown in the figures.

The invention according to the above embodiments allows the realization of a vehicle headlamp, which can meet the legal requirements such as ECE, SAE, CCC, etc.

In the vehicle headlight 2 according to the variant in Fig. 4 In addition, the heat generated during operation of the laser light source 3 waste heat can be used. In the embodiment according to Fig. 4 is the laser light source 3 below a mounted in the installed state of the vehicle headlamp 2 by the optical axis 400 of the vehicle headlamp 2 horizontal plane close to the cover 17 is arranged. The horizontal plane runs in Fig. 4 normal to the plane of the drawing through the optical axis 400 of the vehicle headlight 2.

The laser light source 3 is arranged so close to the cover plate 17 that the cover plate 17 can be heated by means of the waste heat of the laser light source 3. The waste heat can be used for defrosting and deicing the cover 17. Depending on the used laser light source 3 or depending on the material of the cover plate 17 etc. it has to be decided how close the laser light source 3 to the cover plate 17 has to be positioned. The ventilation device 13 of the laser light source 3 can here by supporting the waste heat flow supportive be used. According to the variant in Fig. 4 the laser light source 3 is positioned under a design shutter member 22 having corresponding design apertures 23 for the passage of the waste heat. According to a variant, these design aperture openings 23 can have a nozzle-like shape, so that the airflow 24 caused by the waste heat of the laser light source 3 can be directed in a targeted manner. By nozzle-like shape is here to be understood a shape that allows the steering of the air passing through the design aperture openings 23 air flow to meet the above-mentioned object. Thus, the defrosting and deicing, or in general the benefits of the waste heat of the laser light source 3 can be done even more efficient.

Claims (9)

1. A laser vehicle headlight comprising a light guiding element (1) for a laser vehicle headlight (2), wherein the laser vehicle headlight (2) comprises at least one laser light source (3) and at least one luminous element (4) which can be irradiated by the laser light source (3) and can thus be excited to emit visible light, wherein the light guiding element (1) has a light entrance surface (5) and a light exit surface (6), wherein the entrance cross-sectional area of the light entrance surface (5) is greater than the exit cross-sectional area of the light exit surface (6), wherein the light radiated in through the light entrance surface (5) can be concentrated in the direction of the light exit surface (6) via the inner surface (7) connecting the light entrance surface (5) and the light exit surface (6), wherein the light exit surface (6) is covered at least in part by a light-impermeable delimitation element (15), characterised in that the luminous element (4) is arranged in the light guiding element (1) and the light-impermeable delimitation element (15) is applied to the light guiding element (1).
2. The laser vehicle headlight comprising a light guiding element (1) according to Claim 1, characterised in that the angle of acceptance (300) of the light guiding element (1) is between 0° and 45° with respect to the optical axis (100) of the light guiding element (1).
3. The laser vehicle headlight comprising a light guiding element (1) according to Claim 1 or 2, characterised in that the inner surface (7) of the light guiding element (1) is formed substantially as a paraboloid or as a free-form face.
4. The laser vehicle headlight comprising a light guiding element (1) according to one of the preceding claims, characterised in that the outer face of the light guiding element (1), in the region between the light entrance surface (5) and the light exit surface (6), is provided at least in regions, but particularly completely with a light-impermeable and/or reflective coating (8).
5. The laser vehicle headlight comprising a light guiding element (1) according to one of the preceding claims, characterised in that at least one receptacle for the luminous element (4) is provided in the region of the light exit surface (6), wherein the receptacle is formed in particular as a blind bore (9) or as a cavity (10) completely surrounded by the light guiding element (1).
6. The laser vehicle headlight comprising a light guiding element (1) according to one of the preceding claims, characterised in that at least one reflector element (11), which runs around the light guiding element (1), is provided between the light entrance surface (5) and the light exit surface (6), preferably in the region of the light exit surface (6), in order to deflect the light emitted from the luminous element (4) in a direction facing away from the light entrance surface (5).
7. A laser vehicle headlight according to one of Claims 1 to 6, characterised in that the laser light source (3) is arranged in front of the luminous element (4) as viewed in the main radiation direction (200) of the vehicle headlight (2), such that the light of the laser light source (3) is emitted against the main radiation direction (200) of the vehicle headlight (2).
8. The laser vehicle headlight according to one of Claims 1 to 7, characterised in that at least one screen element (21) is provided, by means of which light reflected by the light entrance surface (5) of the light guiding element (1) or from the interior of the light guiding element (1) in the main radiation direction (200) of the vehicle headlight (2) can be shielded.
9. The laser vehicle headlight according to one of Claims 1 to 8, characterised in that the screen element (21) is formed as a connection piece running between the laser light source (3) and the light guiding element (1) and is formed in particular in a tubular or semi-tubular manner.

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