Lighting device for a motor vehicle

0001The invention relates to a lighting device for a motor vehicle according to the preamble of claim 1.

0002Lighting devices for motor vehicles with a scanner are known from the prior art, with which a predetermined light distribution in the far field of the vehicle is generated via the deflection of a light beam via a reflecting scanning mirror.

0003In the case of illumination devices with scanners, it proves to be disadvantageous that the deflection frequency of the scanning mirror for generating structures in the light distribution with high resolution or with large gradients must be very high. This leads to disturbing scanning effects, such as the stroboscopic effect, especially at high vehicle speeds. To create cut-off lines, scanning illumination devices require a very high optical resolution in order to be able to generate the necessary gradients in the light distribution.

0004To generate bright-dark boundaries, it is also known to introduce physical aperture in the beam path of the light beam. However, these have the disadvantage that they generally lead to shading effects in the generated light distribution.

0005The documents <patcit id="pcit0001" dnum="DE102010028949A1"><text>DE 10 2010 028 949 A1</text></patcit>. <patcit id="pcit0002" dnum="US20110249460A1"><text>US 2011/0249460 A1</text></patcit> and <patcit id="pcit0003" dnum="US20090046474A1"><text>US 2009/0046474 A1</text></patcit> reveal vehicle lights, which generate a light distribution by means of scanners. The document<patcit id="pcit0004" dnum="DE102011013211A1"><text>DE 102011 013 211 A1</text></patcit> discloses a non-scanner vehicle lamp employing a shutter to generate a cut-off line.

0006The object of the invention is to provide a lighting device for a motor vehicle, with which a light distribution of high quality can be generated.

0007This object is achieved by the lighting device according to claim 1. Further developments of the invention are defined in the dependent claims.

0008The lighting device according to the invention is intended for a motor vehicle, such as a car or a truck. It comprises a light source of a number of semiconductor diodes and a scanning device, on which light of the light source falls and which generates a time-varying deflection of the incident light of the light source and thereby a predetermined light distribution at a distance from the lighting device during operation of the lighting device. The predetermined light distribution is generated in particular in the far field of the lighting device. Far field means the light distribution at a distance from the illumination device which is substantially larger than the dimensions of the illumination device and, in particular, lies in the region of 25 m in front of the illumination device.

0009The lighting device according to the invention is characterized in that the scanning device incorporated therein comprises at least two separately controllable scanners, on each of which a separate, generated from the light of the light source beam falls whose deflection is varied by the respective scanner in time. In this case, a bundle of light beams is understood to mean a bundle of light beams delimited in an angle or in space, wherein the light beams in the bundle can essentially run parallel or apart or together. The scanning device thus comprises at least two separate scanners with associated deflection elements, which are configured in particular as reflective scanning mirrors. Due to the separate control of the scanner, the deflection elements independently of each other cause a temporal variation of the deflection of the corresponding light beam. By using more than one scanner, the deflection frequency of the individual scanners can be reduced while the resolution or the gradient of the light distribution remains unchanged, thereby avoiding disturbing scan effects which occur in particular at high vehicle speeds.

0010In the illumination device according to the invention, a diaphragm is arranged in the beam path of the light beam after deflection by the scanning device, with which the light distribution is limited. In a preferred embodiment, a light-dark boundary in the predetermined light distribution is generated with the diaphragm. Preferably, the diaphragm extends substantially parallel to an optical axis predetermined by the beam path of the light beam.

0011In the illumination device according to the invention, the diaphragm effects a subdivision of an image plane into two regions, wherein in at least one operating mode of the illumination device a part of the scanning device is provided exclusively for deflecting light bundles in a region on one side of the diaphragm and in particular below the diaphragm and the other part the scanner of the scanning device is provided exclusively for the deflection of light bundles in an area on the other side of the diaphragm and in particular above the diaphragm. In this way, shadowing effects that can occur when using a scanners with a single scanner can be avoided. These shading effects will be further explained in detail in the detailed description. The above picture plane,

0012Optionally, there is also the possibility that in addition to the aperture described above, which is arranged in the beam path of the light beam after being deflected by the scanning device, one or more further apertures are provided at other positions in the beam path, for example in front of the scanning device.

0013In a particularly preferred embodiment of the illumination device according to the invention, one or more of the scanners and in particular all scanners of the scanning device each comprise a two-dimensional scanning unit, with which the corresponding light beam can be deflected in two directions and in particular in a horizontal and a vertical direction. The horizontal and vertical directions refer to the lighting device when installed in the vehicle, ie the vertical direction extends from the roadway vertically upwards and the horizontal direction parallel to the roadway. The two-dimensional scanning unit can be configured as a 2D scanner with a single deflecting element or scanning mirror which can be pivoted in two directions. Optionally, the two-dimensional scanning unit can also be formed by two deflection elements or scanning mirrors, which are controlled jointly. In a particularly preferred embodiment, the scanners of the illumination device according to the invention are at least partially vector scan units in which the scan speed and the scan direction can be varied.

0014In a further embodiment, the illumination device according to the invention comprises at least one entrance optics for the light of the light source, wherein during operation of the illumination device the separate light bundles are generated via the at least one entrance optics. Preferably, a common entrance optics for generating all separate light bundles is provided. As a result, the structure of the lighting device is less complex. The entrance optics may include, for example, a lens array, with each lens of the array, a separate light beam is generated. Preferably, the lens array is preceded by a collimator lens for focusing the light originating from the light source.

0015In a further, particularly preferred embodiment, the illumination device is designed such that the separate light beams generate light spots of different sizes in the predetermined light distribution. In this way, the illumination device can very flexibly generate different light distributions with sub-regions of different resolution, so that the function of an adaptive optical element in the form of a lens with variable refractive power can be taken over by the scanning illumination device.

0016In a further embodiment of the illumination device according to the invention, at least one exit optics is provided for the light bundles deflected by the at least two scanners, via which the predetermined light distribution at a distance from the illumination device is generated as an image. Preferably, a common exit optics for all deflected light beams is provided, whereby the structure of the lighting device is simplified.

0017In a further embodiment of the illumination device according to the invention, one or more of the scanners of the scanning device each generate a separate region of the predetermined light distribution. Alternatively or additionally, however, it is also possible that at least two scanners generate overlapping regions of the predetermined light distribution.

0018In addition to the aperture described above, in a further preferred embodiment, at least one scanner is provided exclusively for generating the light distribution at the light-dark boundary in at least one operating mode of the illumination device (eg when generating a low-beam light characteristic). This scanner can be operated at a higher deflection frequency than the other scanner or generate a smaller light spot than the other scanner in the light distribution, thereby achieving high resolutions in the range of the cut-off line. This has the advantage that it is possible to design a gradient curve in a light distribution variably, ie independently of rigid physical diaphragms.

0019In a further embodiment of the illumination device according to the invention, the at least two scanners of the scanning device are provided on a common structural unit, the common structural unit in particular having a common cooling unit and / or a common electronic unit for the scanners and / or a common mechanical adjusting device for a carrier the scanners are mounted. As a result, a simple construction of the scanning device is achieved. Furthermore, due to the use of multiple scanners, a greater spread of the local temperature load on the cooling unit is ensured, which considerably reduces the installation space and the weight of the cooling elements used in the cooling unit.

0020In a further variant, at least one scanner and in particular each of the scanners of the scanning device is configured as a MEMS element which, by virtue of its micromechanical scanner structure, permits a particularly compact and robust embodiment with high deflection speeds. In particular, these elements are suitable for an array-like arrangement on a common component and can be used by the distribution of light fluxes to a plurality of units for high-performance applications in the automotive sector.

0021In a further variant, the number of semiconductor diodes comprises one or more and in particular exclusively laser diodes. As a result, a light distribution with very high local light intensity can be generated. The laser diodes preferably have a respective maximum power of at least 1 W and in particular between 1.5 and 5 W. Preferably, the number of semiconductor diodes for generating the predetermined light distribution is operated with a constant and in particular maximum power, whereby the lighting device is used particularly economically.

0022In a further embodiment of the invention, the light source is a monochromatic light source, wherein a conversion element is provided for converting the light of the light source into white light. Such conversion elements are known per se from the prior art. For example, in blue / violet laser diodes with an emission wavelength of 450 nm / 405 nm, a phosphorous conversion element made of nitride-phosphorus or oxide-nitride-phosphorus or cerium-doped YAG-phosphorus can be used to generate white light.

0023The conversion element, which is configured in particular as a layer, can be arranged at different positions depending on the embodiment of the invention. In one variant, the conversion element is arranged at a position at which the light beam has already passed the scanning device, for example in the intermediate image plane mentioned above. However, the conversion element can also be arranged at the light source or between the light source and the scanning device. In the latter case, the conversion element is arranged at a position in the beam path of the light beam before the light beam is incident on the scanning device.

0024Depending on the application, the lighting device according to the invention can take on different functionalities. In one embodiment, the lighting device comprises a headlight. A headlight is characterized by the fact that it actively illuminates the surroundings of the vehicle. Optionally, the lighting device according to the invention may also include a signal light, which is characterized in that it is used only for signaling to other road users. Likewise, the lighting device according to the invention may be a combination of headlight and signal light.

0025In a preferred variant, the lighting device is configured as a headlight such that in operation as Abblendlichtchara kteristik predetermined as a given light distribution and / or a high beam characteristic can be generated. A low beam characteristic is characterized by a sharp cut-off, which is preferably generated using the aperture described above. The scanner used in the area of ​​the cut-off line preferably has a high or a higher local resolution than other scanners of the scanning device. This can be achieved by using this scanner to produce a light spot of smaller size than the light spots of the other scanners.

0026In addition to the lighting device according to the invention, the invention further relates to a motor vehicle, which comprises one or more of the lighting devices according to the invention.

0027Embodiments of the invention are described in detail below with reference to the accompanying figures.

0028Show it:<dl id="dl0001"><dt>Fig. 1</dt><dd>a schematic representation of a known lighting device with a single scanner;</dd><dt>Fig. 2</dt><dd>a schematic representation of a modification of the lighting device of <figref idref="f0001">Fig. 1</figref> with an alternative diaphragm position;</dd><dt>Fig. 3</dt><dd>a schematic representation of an embodiment of a lighting device according to the invention with multiple scanners; and</dd><dt>Fig. 4</dt><dd>a schematic representation of another embodiment of a non-inventive lighting device.</dd></dl>

0029In <figref idref="f0001">Fig. 1</figref> is a side view of a known lighting device for a motor vehicle reproduced. The lighting device is a headlight installed in a motor vehicle (not shown). The illumination device comprises a light source 1 with which white light is generated, for example in the form of an array of a plurality of semiconductor diodes. Optionally, monochromatic semiconductor diodes or laser diodes can also be used as the light source, in which case a conversion element, for example in the form of a phosphor layer, for converting the monochromatic light into white light is additionally provided at a suitable location in the beam path of the light. In particular, the intermediate image plane Z described below is suitable as a position for the conversion element.

0030The light of the light source 1 is collimated via a collimator lens 4 to a light beam L. The beam path of the light beam of the<figref idref="f0001">Fig. 1</figref> and also the light beam of the <figref idref="f0002 f0003 f0004">FIG. 2 to FIG. 4</figref> is indicated by three lines. The light beam L is incident on a scanning device 2, which comprises a single 2D scanner 3 in a manner known per se. The scanning range of the scanner 3 in the vertical direction in the intermediate image plane Z is indicated by the double arrow P. The scanner is suitably activated via a drive unit (not shown) and deflects the light bundle in a time-varying manner via a scanning mirror in the horizontal direction (ie perpendicular to the plane of the page) and in the vertical direction (ie in the plane of the page). This deflected light beam passes through a diaphragm 6, which in<figref idref="f0001">Fig. 1</figref> is arranged perpendicular to the optical axis O of the lighting device. With this diaphragm, the course of a cut-off line is set, which is required for a low beam characteristic of the headlamp. The light-dark boundary initially runs horizontally from the far end of the roadway edge and then extends obliquely upwards near the roadway edge. The illumination device further comprises an exit optics in the form of a lens 7, with which an image of the intermediate image plane Z is generated in a light distribution LV in the far field of the illumination device on the road. In the aperture region, no light can be generated with this arrangement, so that in this case the scanner can only generate a variable light distribution below the light / dark boundary.

0031In <figref idref="f0002">Fig. 2</figref> is essentially the same lighting device as in <figref idref="f0001">Fig. 1</figref> shown, with the only difference that the aperture 6 is now arranged horizontally (ie along the optical axis O) and the scan area has a greater vertical extent. A horizontal aperture arrangement makes it possible with the scanner both different Abblendlichtverteilungen as well as different high beam distributions or any combination thereof to generate. In order to generate a low-beam light characteristic, the scanner essentially scans only in the scan area above the diaphragm 6, whereby a light distribution below the course of the diaphragm is generated in the far field via the optical imaging through the lens 7. When the main beam is switched on, scanning takes place essentially in the entire scan area P, so that a light distribution is generated in a substantially larger vertical area.<figref idref="f0002">Fig. 2</figref> is clear. It thus occur in the light distribution of the high beam unwanted shadowing. Such shadowing can be avoided with the embodiment of the lighting device according to the invention described below.

0032<figref idref="f0003">Fig. 3</figref> shows a side view of a schematic representation of an embodiment of a lighting device according to the invention. Large parts of the lighting device of<figref idref="f0003">Figure 3</figref> correspond to the <figref idref="f0001">Fig. 1</figref> or. <figref idref="f0002">Fig. 2</figref>, wherein the same reference numerals have been used for the designation of identical components in both figures. In analogy to<figref idref="f0002">Fig. 2</figref> The lighting device of FIG <figref idref="f0003">Fig. 3</figref> a light source 1 in the form of an array of semiconductor diodes which generate white light. As in<figref idref="f0001">Fig. 1</figref> or. <figref idref="f0002">Fig. 2</figref> If appropriate, monochromatic semiconductor diodes or laser diodes can also be used, in which case again a corresponding conversion element is to be arranged in the beam path. The light of the light source 1 passes through an entrance optics, which comprises a converging lens 4 and a lens array of two lenses 5, to a scanning device 2. The essential difference between the device of<figref idref="f0002">Fig. 2</figref> and the device of <figref idref="f0003">Fig. 3</figref> consists in that according to <figref idref="f0003">Fig. 3</figref> Two separate light bundles L and L 'are generated via the entrance optics and the scanning device 2 comprises separately controllable scanners 3 and 3' with corresponding scanning mirrors onto which one of the light bundles L and L 'respectively falls. The two scanners are independently operable, ie the respective light bundles can be deflected independently of each other. The two scanners 3 and 3 'are again 2D scanners, which can pivot the respective light beam in the horizontal and vertical directions. Preferably, so-called vector scanners are used as scanners with which - in contrast to line scanners - the scanning speed or the scanning direction and thus the deflection of the respective light beam can be varied freely.

0033In the embodiment of the <figref idref="f0003">Fig. 3</figref> the two separate scanners are arranged on a common structural unit, which is indicated schematically by the reference numeral 201. In this case, a common cooler for the reflecting scanning mirrors is formed via the common structural unit. Likewise, a common electronics for the scanner can be used, but the control is done by this common electronics separately for each scanner. In addition, if necessary, a common mechanical adjustment can be used for coarse adjustment of the scanner. This adjustment device can adjust the position of a common carrier on which the scanners are arranged.

0034In analogy to the embodiment of the <figref idref="f0002">Fig. 2</figref> The lighting device of FIG <figref idref="f0003">Fig. 3</figref> a diaphragm 6, which is parallel to the optical axis (not off <figref idref="f0002">Fig. 2</figref> visible) and is arranged in the region of the intermediate image plane Z. The aperture in turn produces a cut-off for a low beam characteristic of the headlamp. The intermediate image plane is in turn converted via an exit optics 7 in the form of a lens into the light distribution LV on the road. In the embodiment of the<figref idref="f0002">Fig. 2</figref> is the scan range of the scanner 3 below the aperture 6, which is indicated by the double arrow P1. In contrast, the scanning range of the scanner 3 'is above the diaphragm 6, which is indicated by the double arrow P2. To generate a low-beam light distribution, essentially only the scanner 3 'is used, which generates the low-beam light characteristic with the aid of the diaphragm 6. When switching on the high beam, the scanner 3 is also put into operation, so that horizontally higher areas are illuminated. Due to the separate scan areas of the two scanners 3 and 3 ', a total shadowing is avoided, which results in the use of a single scanner in the device of<figref idref="f0002">Fig. 2</figref> occurs.

0035In a modification of the embodiment of the <figref idref="f0001">Fig. 1</figref> can also overlap the scan areas P1 and P2 of the two scanners 3 and 3 'to achieve a good light output. For example, in the generation of a low beam characteristic, the scanner 3 'can only scan in the immediate vicinity above the aperture 6, whereas the scanner 3 illuminates the remaining area above the aperture. In contrast, when generating a high-beam distribution, both scanners 3 and 3 'work in a scanning region both above and below the diaphragm.

0036<figref idref="f0004">Fig. 4</figref> shows a modification of the embodiment of the <figref idref="f0003">Fig. 3</figref>, In this case, the scanning regions P1 and P2 overlap the scanner 3 or 3 '. Furthermore, the generation of light distributions with a different spot size is achieved by the use of different lenses 5 and 5 'in the entrance optics. In particular, the scanner 3 'generates a light spot SP2 in the intermediate image plane Z and thus also in the light distribution LV, which is substantially larger than the light spot SP1 generated by the scanner 3. Moreover, in the embodiment of the<figref idref="f0004">Fig. 4</figref> the aperture omitted, with the aperture position off <figref idref="f0003">Fig. 3</figref> The spot SP1, which scans in the region of the former position of the diaphragm, is now used to generate a light-dark boundary in the low beam distribution. Dark border can also be generated without aperture.

0037In addition to the advantage of avoiding shading, the lighting device according to the embodiments described above further advantages. In particular, with the use of multiple scanners, the deflection frequency can be reduced to achieve the same spatial resolution or the same brightness gradient of the light distribution. Due to the reduced deflection frequency, disturbing scan effects, such as the stroboscopic effect, are avoided. In addition, a simple construction of the illumination device is ensured by integrating the multiple scanners on a common structural unit and by using a common entrance or exit optics. Furthermore, the achievable sampling rate can be increased through the use of multiple scanners.<figref idref="f0003">Fig. 3</figref> and <figref idref="f0004">Fig. 4</figref> is indicated. However, if necessary, the increase of the sampling rate can also be realized by the multiple sampling of a common scan field.

LIST OF REFERENCE NUMBERS

0038<dl id="dl0002" compact="compact"><dt>1</dt><dd>light source</dd><dt>2</dt><dd>scanning device</dd><dt>201</dt><dd>unit</dd><dt>3,3 '</dt><dd>scanner</dd><dt>4</dt><dd>converging lens</dd><dt>5.5 '</dt><dd>lens array</dd><dt>6</dt><dd>cover</dd><dt>7</dt><dd>exit optics</dd><dt>P, P1, P2</dt><dd>scan areas</dd><dt>L, L '</dt><dd>light beam</dd><dt>L "</dt><dd>aperture position</dd><dt>SZ</dt><dd>shadow zone</dd><dt>LV</dt><dd>light distribution</dd><dt>Z</dt><dd>Intermediate image plane</dd><dt>O</dt><dd>optical axis</dd></dl>