Patent Publication Number: US-10775012-B2

Title: Pixel light source

Description:
TECHNICAL FIELD 
     This disclosure relates to a pixel light source. 
     BACKGROUND 
     Pixel light sources comprising micromirror matrix arrangements for light shaping are known. Such pixel light sources can be used as headlamps for motor vehicles, for example, as described in Vikrant R. Bhakta et al., “High resolution adaptive headlight using Texas Instruments DLP® technology,” ISAL 2015, page 483. WO 2011/156271 A3 describes a pixel light source having a light source array in a sparse arrangement. 
     SUMMARY 
     We provide a pixel light source including having a light source array, an optical system and an imager matrix arrangement, wherein the optical system maps light radiated by the light source array onto the imager matrix arrangement, the light source array includes a plurality of light emitting diode elements and a plurality of LARP elements, and the optical system is configured to map the light radiated by at least one of the LARP elements into a gap in the angular aperture situated between the light radiated by the light emitting diode elements. 
     We also provide a headlamp for a motor vehicle including having a light source array, an optical system and an imager matrix arrangement, wherein the optical system maps light radiated by the light source array onto the imager matrix arrangement, the light source array includes a plurality of light emitting diode elements and a plurality of LARP elements, and the optical system is configured to map the light radiated by at least one of the LARP elements into a gap in the angular aperture situated between the light radiated by the light emitting diode elements. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  schematically shows a plan view of a pixel light source with a light source array, an optical system and an imager matrix arrangement. 
         FIG. 2  schematically shows a plan view of the light source array of the pixel light source. 
         FIG. 3  schematically shows a graph to illustrate the intensity distribution of light radiated by the light source array. 
         FIG. 4  schematically shows a graph to explain the angular aperture of the light mapped onto the imager matrix arrangement by the optical system. 
     
    
    
     LIST OF REFERENCE SIGNS 
     
         
           10  pixel light source 
           100  light source array 
           105  light 
           110  light emitting diode element 
           115  hexagonal pattern 
           120  LARP element 
           125  hexagonal pattern 
           200  optical system 
           210  optical lens 
           300  imager matrix arrangement 
           301  first direction 
           302  second direction 
           310  middle 
           320  edge region 
           400  intensity distribution 
           401  intensity 
           410  intensity of a light emitting diode element 
           420  intensity of an LARP element 
           430  total intensity 
           500  angular aperture 
           510  first extent of the angular aperture 
           520  second extent of the angular aperture 
           530  angle covered by light emitting diode element 
           540  angle covered by LARP element 
           550  gap 
       
    
     DETAILED DESCRIPTION 
     Our pixel light source comprises a light source array, an optical system and an imager matrix arrangement. In this case, the optical system is intended to map light radiated by the light source array onto the imager matrix arrangement. The light source array has a plurality of light emitting diode elements and a plurality of LARP elements. 
     The LARP elements (LARP stands for laser activated remote phosphor) each have a wavelength-converting element and a semiconductor laser diode that illuminates the wavelength-converting element. The wavelength-converting element converts irradiated laser light into useful light of a different wavelength. 
     The light emitting diode elements of the light source array of the pixel light source may advantageously be available at low cost and allow production of a high total light current by the light source array. The LARP elements can advantageously additionally produce a high illuminance maximum in the center of the region illuminated by the pixel light source. As a result, the pixel light source is advantageously appropriate in particular for applications that require inhomogeneous illumination of a region illuminated by the pixel light source. 
     The LARP elements may be arranged between the light emitting diode elements. Advantageously, this results in a compact and space-saving configuration of the light source array of the pixel light source. 
     The light emitting diode elements may be arranged in a hexagonal pattern. Advantageously, the light emitting diode elements in such an arrangement allow uniform illumination even when the individual light emitting diode elements are arranged at a distance from one another. 
     The LARP elements may be arranged in a hexagonal pattern. Advantageously, this arrangement of the LARP elements allows particularly simple and uniform arrangement of the LARP elements between the light emitting diode elements of the light source array. 
     The hexagonal pattern of the light emitting diode elements and the hexagonal pattern of the LARP elements may overlap. Advantageously, the LARP elements and the light emitting diode elements in this arrangement are particularly uniformly distributed over the surface area of the light source array. In another configuration, the LARP elements and the light emitting diode elements may be arranged separately from one another. 
     The optical system may map the light radiated by the light source array onto the imager matrix arrangement with a first extent, measured in a first direction, of the angular aperture and a second extent, measured in a second direction, of the angular aperture. In this case, the first direction and the second direction are oriented at right angles to one another. Moreover, the first extent of the angular aperture and the second extent of the angular aperture are of different magnitude. Advantageously, the optical system of the pixel light source is thereby adapted to the imager matrix arrangement of the pixel light source being able to comprise different angular aperture magnitudes in different spatial directions. As a result, the optical system allows optimum utilization of the angular aperture of the imager matrix arrangement of the pixel light source. A larger range can be modulated and therefore more modulated light can be transmitted in total. 
     The optical system may be configured to map the light radiated by at least one of the LARP elements into a gap in the angular aperture situated between the light radiated by the light emitting diode elements. Advantageously, this allows gaps in the angular aperture that arise as a result of the individual light emitting diode elements of the light source array being arranged at a distance from one another to be filled at least in part by the LARP elements. Another option is for individual positions in the angular aperture illuminated by light emitting diode elements of the light source array to be additionally illuminated by LARP elements. 
     At least one LARP element may be configured such that light radiated by the LARP element and mapped onto the imager matrix arrangement by the optical system comprises an intensity that falls from the middle of the imager matrix arrangement to an edge region of the imager matrix arrangement. Advantageously, the pixel light source thereby allows a target region to be illuminated with a luminance higher in the central region than in outer regions. This is advantageous for many illumination applications in which a middle region of the illuminated region is of particular interest. Advantageously, the design of the pixel light source exploits the circumstance that LARP elements, based on a design, comprise spatially inhomogeneous radiation characteristics. 
     The optical system may comprise a plurality of optical lenses. As a result, the optical system can allow the light radiated by each of the light emitting diode elements of the plurality of light emitting diode elements of the light source array and the light radiated by each of the LARP elements of the plurality of LARP elements of the light source array to be mapped onto the imager matrix arrangement of the pixel light source. The optical system can comprise a field lens. 
     The imager matrix arrangement may be configured as a micromirror matrix arrangement. A particular advantage of the pixel light source in this case is that different angular aperture magnitudes of the micromirror matrix arrangement in different spatial directions can be exploited in optimum fashion by the pixel light source. 
     The pixel light source may be configured as a headlamp for a motor vehicle. In this case, it is a particular advantage that the pixel light source can illuminate a middle region of the region illuminated by the pixel light source with higher luminance than an edge region. 
     The properties, features and advantages described above and the way in which they are achieved will become clearer and more distinctly comprehensible in connection with the description of examples that follow, these being explained in more detail in connection with the drawings, in schematic form. 
       FIG. 1  shows a highly schematized depiction of a pixel light source  10 . The pixel light source  10  may be configured as a headlamp for a motor vehicle, for example, or can form part of a headlamp of a motor vehicle. In particular, the pixel light source  10  may be configured as a front headlamp, for example. 
     The pixel light source  10  comprises a light source array  100 , an optical system  200  and an imager matrix arrangement  300 . 
     The light source array  100  radiates light  105 . The light  105  is normally light from the visible spectral range, for example, white light. 
     The optical system  200  maps the light  105  radiated by the light source array  100  onto the imager matrix arrangement  300 . 
     The imager matrix arrangement  300  in the example depicted is configured as a micromirror matrix arrangement (Digital Micromirror Device DMD) having a multiplicity of individually tiltable micromirrors arranged in a matrix arrangement. The imager matrix arrangement  300  can alternatively also be configured as a microshutter matrix arrangement (Digital Micro Shutter DMS or MEMS Shutter), as a transmissive liquid crystal display (LCD) or as a reflective liquid crystal display (Liquid Crystal on Silicon LCoS), however. 
     The imager matrix arrangement  300  shapes the light  105  mapped onto the imager matrix arrangement  300  by the optical system  200  and deflects it into a region to be illuminated by the pixel light source  10  in the surroundings of the pixel light source  10 . To this end, the pixel light source  10  can have a further optical system arranged between the imager matrix arrangement  300  and the region to be illuminated by the pixel light source  10 . This further optical system is not shown in the schematic depiction of  FIG. 1  and can also be dispensed with. 
       FIG. 2  shows a schematic depiction of a plan view of the radiation side of the light source array  100  of the pixel light source  10 . The line of vision in  FIG. 2  is opposite to the direction of radiation of the light  105  radiated by the light source array  100 . 
     The light source array  100  has a plurality of light emitting diode elements  110  and a plurality of LARP elements  120 . 
     The light emitting diode elements  110  each have one or more light emitting diode chips and can each also have a converter element that converts light emitted by the respective light emitting diode chip into useful light of a different wavelength, for example, into white light. 
     The abbreviation LARP stands for laser activated remote phosphor, that is to say for a converter element spot lit by a laser chip, which converter element is arranged at a distance from the laser chip. The LARP elements can also be referred to as elements that produce useful light by a converter element illuminated by a laser. The LARP elements each have a laser chip and a wavelength-converting element. The laser chip illuminates the wavelength-converting element with a laser beam. The wavelength-converting element converts at least some of the light of the laser beam into useful light of a different wavelength. By way of example, into yellow light, to produce white light in the mix with unconverted light. 
     The light emitting diode elements  110  of the light source array  100  of the pixel light source  10  are arranged at a distance from one another in what is known as a sparse arrangement. In this case, the light emitting diode elements  110  in the example shown in  FIG. 2  are arranged in a hexagonal pattern  115 . In the example shown in  FIG. 2 , the light source array  100  has ten light emitting diode elements  110 . The light source array  100  can also be configured with a different number of light emitting diode elements  110 , however, in particular with a higher number of light emitting diode elements  10 . 
     The LARP elements  120  of the light source array  100  of the pixel light source  10  are arranged at a distance from one another between the light emitting diode elements  110  of the light source array  100 . In the example shown in  FIG. 2 , the light source array  100  of the pixel light source  10  has ten LARP elements  120 . The number of LARP elements  120  can also be different, however, in particular greater. The number of LARP elements  120  of the light source array  100  may be consistent with the number of light emitting diode elements  110 , this not being absolutely necessary, however. 
     In the example shown in  FIG. 2 , the LARP elements  120  are arranged in a hexagonal pattern  125 . In this case, the hexagonal pattern  125  of the LARP elements  120  and the hexagonal pattern  115  of the light emitting diode elements  110  overlap such that the LARP elements  120  are arranged between the light emitting diode elements  110 . 
     In the example of the light source array  100  shown in  FIG. 2 , the light emitting diode elements  110  and the LARP elements  120  of the light source array  100  are arranged such that the radiation side of the light source array  100  comprises a narrower width in a first direction  301  than in a second direction  302  at right angles to the first direction  301 . This is not absolutely necessary, however. The light source array  100  can also be configured such that it comprises substantially the same width in both the first direction  301  and the second direction  302 . 
     The optical system  200  visible in the schematic depiction of the pixel light source  10  of  FIG. 1  maps the light  105  radiated by the light source array  100  onto the imager matrix arrangement  300 . To this end, the optical system  200  has a plurality of optical lenses  210 . One or more of the optical lenses  210  of the optical system  200 , in particular the last optical lens  210  of the optical system  200 , may be field lenses. The optical system  200  can comprise optical lenses  210  individually associated with the individual light emitting diode elements  110  and LARP elements  120  of the light source array  100 . In this case, each light emitting diode element  110  and each LARP element  120  of the light source array  100  may each have one or more associated optical lens(es)  210  of their own. 
     The optical system  200  maps the light  105  emitted by the light source array  100  onto the imager matrix arrangement  300  such that each portion of the light  105  radiated by a light emitting diode element  110  or an LARP element  120  is respectively mapped onto the entire surface area of the imager matrix arrangement  300 . Those portions of the light  105  radiated by the individual light emitting diode elements  110  and LARP elements  120  overlap at the imager matrix arrangement  300 . 
       FIG. 3  shows a schematic depiction of an intensity distribution of those portions of the light  105  mapped onto the imager matrix arrangement  300  by the optical system  200  radiated by the light emitting diode elements  110  and the LARP elements  120  of the light source array  100  at the location of the imager matrix arrangement  300 . Plotted on a horizontal axis of the graph of  FIG. 3  is the first direction  301  oriented parallel to the imager matrix arrangement  300 . In this case, a middle  310  and edge regions  320  of the imager matrix arrangement  300  are marked. Instead of the first direction  301 , the second direction  302 , which is oriented at right angles to the first direction  301  and likewise parallel to the imager matrix arrangement  300 , could also be depicted, without this changing the quality of the depicted intensity distribution. Plotted on a vertical axis of the graph of  FIG. 3  is an intensity  401  of the light  105  impinging on the imager matrix arrangement  300 . 
     A first intensity curve  410  schematically reproduces the intensity of that portion of the light  105  radiated by an exemplary selected light emitting diode element  110  of the light source array  100 . The intensity of that portion of the light  105  radiated by this light emitting diode element  110  is substantially constant over the entire surface area of the imager matrix arrangement  300 . Those portions of the light  105  radiated by the other light emitting diode elements  110  of the light source array  100  have a corresponding intensity distribution. 
     A second intensity curve  420  exemplarily reproduces the profile of the intensity of that portion of the light  105  radiated by an exemplarily selected LARP element  120  of the light source array  100  at the location of the imager matrix arrangement  300 . The light radiated by this LARP element  120  has a higher intensity in the middle  310  of the imager matrix arrangement  300  than in the edge regions  320  of the imager matrix arrangement  300 . The light radiated by this LARP element  120  can comprise approximately the shape of a Gaussian distribution, for example. Those portions of the light  105  radiated by the other LARP elements  120  of the light source array  100  comprise corresponding intensity distributions at the location of the imager matrix arrangement  300 . 
     Those portions of the light  105  radiated by the individual light emitting diode elements  110  and the individual LARP elements  120  of the light source array  100  overlap at the location of the imager matrix arrangement  300 . The overlap comprises a total intensity  430 , shown schematically in  FIG. 3 , that is higher in the middle  310  of the imager matrix arrangement  300  than in the edge regions  320  of the imager matrix arrangement  300 . The light emitting diode elements  110  of the light source array  100  thus produce a homogeneous background to the light  105 , the intensity of which is substantially constant over the surface area of the imager matrix arrangement  300 . The LARP elements  120  of the light source array  100  furthermore produce an intensity or illuminance maximum in the middle  310  of the imager matrix arrangement  300 . 
     Those portions of the light  105  radiated by the light emitting diode elements  110  and the LARP elements  120  and mapped onto the imager matrix arrangement  300  by the optical system  200  impinge on the imager matrix arrangement  300  from different angular directions.  FIG. 4  shows a schematic depiction of an angular aperture  500  of the imager matrix arrangement  300 . The angular aperture  500  indicates a solid angle within which the light  105  must impinge on the imager matrix arrangement  300  to be able to be controlled by the imager matrix arrangement  300 . The optical system  200  is configured to map the light  105  radiated by the light source array  100  onto the imager matrix arrangement  300  with the angular aperture  500 . 
     The angular aperture  500  has a first extent  510  of the angular aperture in the first direction  301  and a second extent  520  of the angular aperture in the second direction  302 . The first extent  510  of the angular aperture and the second extent  520  of the angular aperture can have different magnitudes. In the example depicted, the second extent  520  of the angular aperture is greater than the first extent  510  of the angular aperture. The first extent  510  of the angular aperture could also be greater than the second extent  520  of the angular aperture, however. By way of example, the first extent  510  of the angular aperture can cover an angle of ±12° and the second extent  520  of the angular aperture can cover an angle of ±21°. The first extent  510  of the angular aperture and the second extent  520  of the angular aperture may also be of the same magnitude. 
     If the imager matrix arrangement  300  is configured as a micromirror matrix arrangement, the first direction  301  may be consistent with a direction of tilt of the micromirrors of the imager matrix arrangement  300 , for example, while the second direction  302  is oriented orthogonally with respect to the direction of tilt of the micromirrors of the imager matrix arrangement  300 . The first extent  510  of the angular aperture is then associated with the angle that can be modulated by tilting the micromirrors of the imager matrix arrangement  300 . It is also conversely be possible for the second direction  302  to be consistent with the direction of tilt of the micromirrors of the imager matrix arrangement  300 , however. 
     Those portions of the light  105  radiated by the light emitting diode elements  110  and the LARP elements  120  mapped onto the imager matrix arrangement  300  by the optical system  200  within the angular aperture  500 . In  FIG. 4 , the angles  530  of the angular aperture  500  covered by the light emitting diode elements  110  and the angles  540  of the angular aperture  500  covered by the LARP elements  120  are depicted schematically. In this case, those portions of the light  105  radiated by the LARP elements  120  are mapped onto the imager matrix arrangement  300  by the optical system  200  in the depicted example such that the angles  540  covered by the LARP elements are situated in gaps  550  between the angles  530  covered by the light emitting diode elements  110 . This achieves more complete coverage of the angular aperture  500  of the imager matrix arrangement  300 . It is also possible for those portions of the light  150  emitted by the LARP elements  120  to be mapped onto the imager matrix arrangement  300  by the optical system  200  such that individual or multiple angles  530  of the angular aperture  500  covered by light emitting diode elements  110  are additionally also covered by one or more LARP elements  120 , however. 
     Our light sources have been illustrated and described in more detail on the basis of preferred examples. Nevertheless, this disclosure is not limited to the examples disclosed. Rather, other variations can be derived therefrom by those skilled in the art without departing from the scope of protection of the appended claims. 
     This application claims priority of DE 10 2016 103 717.6, the subject matter of which is incorporated herein by reference.