Patent Publication Number: US-2020292143-A1

Title: Lighting arrangement

Description:
FIELD OF THE INVENTION 
     The invention relates to a lighting arrangement. In particular, the invention relates to a lighting arrangement which may be used in a headlamp of a vehicle. 
     BACKGROUND OF THE INVENTION 
     Different types of lighting arrangements are known which use optical elements such as collimators, reflectors and/or lenses to transform light emitted from a light source to a desired illumination beam pattern. 
     EP 2 327 927 B1 describes a lens element for a light source, in particular for an LED. The lens element comprises a body of light conducting material. The body conducts portions of light originating from the light source. Portions of the light are reflected as a consequence of total reflection at boundary surfaces of the body. 
     SUMMARY OF THE INVENTION 
     It may be considered an object to propose a lighting arrangement to achieve a desired illumination beam pattern suited for a vehicle headlamp, in particular from a compact light source. 
     According to an aspect of the invention, a lighting arrangement according to claim  1  is proposed. Dependent claims refer to preferred embodiments. 
     The lighting arrangement according to the invention includes a light source and a beam shaping arrangement with a light input portion and a light output portion. Light from the light source is received at the light input portion and emitted as a shaped beam at the light output portion. The light input portion may be e.g. a light input area or surface, and the light output portion may likewise be a light output area or surface. A forward direction may be defined from the light input portion into the direction of the light output portion, e.g. from a center of a light input surface to a center of a light output surface. 
     As will become apparent in the following description, and in particular from the preferred embodiments of the invention, the beam shaping arrangement may have several different embodiments, and may include one or more types of optical elements to guide,  shape, reflect, and/or otherwise optically modify the light from the light input portion before it is emitted at the light output portion. 
     In the claims and following description, reference will be made to dimensions and/or directions, such as a height direction and lateral directions. These directions may be understood relative to the above defined forward direction being arranged at least substantially horizontally. While an at least generally horizontal arrangement will be the preferred orientation in operation of the lighting arrangement, for example in a vehicle head lamp, the skilled person will understand that there may be situations or uses where the lighting arrangement can be oriented differently. Thus, reference to the above directions is only intended to clarify the relative arrangement and should not be understood as limiting the orientation in which the lighting arrangement may be operated. 
     According to an aspect of the invention, the beam shaping arrangement is disposed to divide light from the light input portion into at least two separate beam portions. These include at least a first and a second beam portion separated in a height direction. Thus, the first and second beam portion may be distinguished in that they follow different corresponding beam paths arranged at different height within the beam shaping arrangement, and/or that they are directed under different angles of inclination relative to the forward direction. For example, a dividing angle of inclination may be defined, e.g. relative to the horizontal direction, such that the first beam portion may include light emitted under angles of inclination greater than the dividing angle of inclination, and the second beam portion may include light emitted under angles of inclination less than the separating angle of inclination. 
     According to an aspect of the invention, the beam shaping arrangement is disposed such that the first and second beam portions are led to converge in the height direction at or towards said light output portion. In this context, the term “converge” is not intended to designate the spread of beam directions within the first and second beam portions, but should be understood as referring to the fact that the first and second beam portions are brought together in the height direction at the light output portion. Thus, the first and second beam portions, which are separated in the height direction at least in a portion of the beam shaping arrangement, are again brought together at the light output portion. As will be apparent in connection with preferred embodiments, the first and second beam portions may be arranged at the light output portion at at least substantially the same height. 
     According to an aspect of the invention, the first and second beam portions are however differently directed into lateral directions, relative to the forward direction. At the light output portion, the second beam portion is arranged and/or directed laterally further  outward relative to the first beam portion. The term “laterally outward” may be understood relative to a center of the light output portion. 
     At the light output portion, the first and second beam portions are thus emitted laterally offset from each other. 
     Thus, the beam shaping arrangement may achieve a beam to be emitted at the light output portion which may be wider in at least one, preferably both lateral directions than the input beam received at the light input portion. Such a broadened beam is particularly preferred for automotive front lighting. According to an underlying concept of the invention, such a broader beam is formed from two or more beam portions initially separated in the height direction. Thus, in the beam path from the light source up to the light output portion, a spread of emitted light in the height direction is transformed into a spread into lateral directions. The intensity distribution may thus be transformed to match the aperture of further optical elements, such as a projection lens. In this way, it is possible to obtain a wide output beam in a very efficient way. 
     In accordance with the widening of the output beam, the dimensions of the light output portion may be such that its lateral width corresponds to more than twice its height or thickness (measured at the thickest portion), preferably more than four times. The height of the light output portion may preferably be less than 10 times the height of the light input portion, further preferably less than 6 times. The width or lateral extension of the light output portion may preferably be more than 10 times the width of the light input portion, further preferably more than 12 times. 
     The general concept of the above described aspects of the invention of using height separated beam portions to obtain a laterally spread output beam pattern may be used in different embodiments and combinations, some of which will be further described below. 
     According to one embodiment, the first beam portion may be designated a center beam, which is directed to a center portion of the light output portion. The second beam portion may be designated a peripheral beam, directed to a peripheral portion of the light output portion, thus laterally further outward relative to the first beam portion. 
     In a particularly preferred embodiment, the peripheral beam may be directed to a first lateral side of the center portion, e.g. to the right, and at least one further beam portion may be directed to the second, opposite lateral side, e.g. to the left. Particularly, the arrangement may be at least substantially symmetrical with regard to the lateral directions. For example, while the first beam portion may be directed to the center portion of the light output portion, one or more peripheral beams may be directed to peripheral portions on one  side, and the same number of peripheral beams may be directed to the opposite side of the center portion at the light output portion. 
     According to a further preferred embodiment, the first beam portion may be a first peripheral beam, which is directed to a first peripheral portion at the light output portion, and the second beam portion may be a second peripheral beam, directed to a second peripheral portion arranged laterally further outward relative to the first peripheral portion. Thus, the first and second beam portions, separated in height direction, may both be directed towards peripheral portions, however one further outward relative to the other. Thus, again, a broadened beam may be achieved. 
     In a particularly preferred embodiment, a first and a second peripheral portion may be arranged on a first lateral side of the light output portion, and further beam portions may be arranged on a second, opposite lateral side of the light output portion. The arrangement may preferably be at least substantially symmetrical. Thus, for example four peripheral portions may be provided, two to each lateral side. 
     In a particularly preferred embodiment, light may be divided into at least a first, second and third beam portion, separated in the height direction. The first beam portion may be a center beam directed to a center portion of the light output portion. The second beam portion may be a first peripheral beam directed to a first peripheral portion of the light output portion, and the third beam portion may be a second peripheral beam, directed to a second peripheral portion arranged laterally further outward relative to the first peripheral portion. As will be shown for preferred embodiments, a separation of at least three different beam portions in height may thus be used to achieve a particularly widely spread output beam. Also, for this embodiment, an at least substantially symmetrical arrangement is preferred, for example with the first and second peripheral portions arranged to one lateral direction of the center portion, and further beam portions arranged towards a second, opposite lateral side. 
     According to further preferred embodiments of the invention, the beam shaping arrangement may include at least one lateral reflection surface to reflect at least one of the beam portions into a lateral direction. This may be used to achieve the desired broadened beam in lateral direction. Particularly preferably, the beam shaping arrangement may include at least a first and a second lateral reflection surface. The first lateral reflection surface may be disposed to reflect one or more of the beam portions into a lateral direction towards the second lateral reflection surface, and the second lateral reflection surface may be disposed to direct the beam portion into a direction at least substantially parallel to the  forward direction toward the light output portion. Thus, by twice reflecting at least one of the beam portions at the first and second lateral reflection surface, beams may be directed to peripheral portions of the light output portion while being oriented at least substantially parallel to the forward direction. 
     According to a preferred embodiment, at least one of the beam portions may be led within the beam shaping arrangement to first diverge from the forward direction in the height direction, and then converge toward the forward direction in the height direction. Again, the terms “converging” and “diverging” should not be understood as to refer to increased or reduced spread of the beam portion itself, but to designate the direction of the beam portion relative to the forward direction. According to the preferred embodiment, for example the first beam portion may be an upper beam portion, which within the beam shaping arrangement is first guided away from the forward direction in height direction, and is then guided back toward the forward direction at the light output portion. 
     For example, this may be achieved by a bridge member included in the beam shaping arrangement, for example a light guide. The bridge member may extend from the light input portion to the light output portion, and may include at least a first bridge member portion directed away from the forward direction into the height direction, and a second bridge member portion directed toward the forward direction in the height direction. In particular, the bridge member may be an arch shaped light guide. 
     Generally, for the output beam at the light output portion it is preferred that the first, second and any further beam portions are directed to be at least substantially parallel to the forward direction to form an illumination beam. 
     The illumination beam emitted from the light output portion may preferably be further projected by a projection lens. The projection lens may be used to image the light output portion. The light output portion may be shaped correspondingly, e.g. be of concave shape. At least one front edge of the light output portion may serve to achieve a light/dark boundary in the projected illumination beam. For use in automotive front lighting, at least one laterally extending front edge of the light output portion may include a first and a second edge portion adjacent to each other, which may both be at least substantially straight (or be shaped such that their images projected by a projection lens are at least substantially straight lines). In order to conform to intensity distributions desired for automotive front lighting, the first and second edge portions may be arranged inclined, e.g. at an angle to each other of 5-50°, preferably 15°.  
     The beam shaping arrangement may in principal be provided as an arrangement of separate optical elements, such as e.g. one or more collimators, one or more reflector surfaces, etc. In a particularly preferred embodiment, the beam shaping arrangement may include a transparent body disposed to guide light from the light input portion in the interior of the body. The body may include reflection surfaces at which light may be reflected due to total internal reflection. As will become apparent in connection with preferred embodiments, the entire beam shaping arrangement may be comprised of a single transparent body. The body may for example include a central cavity forming reflection surfaces to separate different beam portions. The reflection surfaces may in particular be arranged to laterally deflect beam portions into the lateral directions. A light guide may be provided substantially parallel to the forward direction to pass over the cavity. 
     Generally, it is preferred that the beam shaping arrangement may be of overall flat shape. For example, it may have an extension in lateral direction which is more than twice of an extension in height direction. 
     These and other aspects of the invention will become apparent from and elucidated with reference to the embodiments described herein after. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a partly schematical top view of an embodiment of a lighting arrangement including first embodiment of a TIR body; 
         FIG. 2  shows a side view of the lighting arrangement of  FIG. 1 ; 
         FIGS. 3-7  show a second embodiment of a TIR body in a perspective view, front view, top view, back view and side view; 
         FIGS. 8, 9  show the TIR body from  FIG. 3-7  in a top and side view with beam paths; 
         FIG. 10  shows a perspective view of a third embodiment of a TIR body; 
         FIGS. 10 a , 10 b , 10 c    show sectional views of the TIR body of  FIG. 10 , the planes A, B and C in  FIG. 10  showing the position of the sections 
         FIG. 11  shows a front view of the TIR body of  FIG. 10 .  
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
       FIG. 1, 2  schematically show a lighting arrangement  10  in a top view and side view. The lighting arrangement includes an LED light source  12 , a beam shaping arrangement which in the present example is constituted by a solid body  10  made out of transparent material acting as a TIR (total internal reflection) body, and a projection lens  16 . 
     The lighting arrangement may be, for example, part of a headlamp of a motor vehicle. 
     Light emitted from the light emitting surface of the LED light source  12  enters the interior of the TIR body  14  at a light input surface  20  and is internally conducted and guided within the TIR body  14  to be emitted at a light output surface  22  thereof. As will be further explained below, the light intensity distribution emitted from the light emitting surface of the LED  12  as a Lambertian emitter is altered within the TIR body  14  such that a shaped illumination beam  24  is emitted at the light output surface  22  to be projected by the projection lens  16 . 
     While the input beam of light received at the light input surface  20  of the TIR body  14  corresponds to the square shape of the light emitting surface of the LED  12 , the shaped beam  24  is laterally widened, i.e. extended into lateral left and right directions as indicated L and R in  FIG. 1 . The height direction H is indicated in  FIG. 2  for reference. 
     In the schematical example of  FIG. 1 ,  FIG. 2 , a forward direction of the beam shaping arrangement may be defined by an optical axis  18  through the center of the LED  12 , the center of the light input surface  20 , the center of the light output surface  22  and the center of the projection lens  16 . For more detailed embodiments, such as shown in  FIG. 3-11 , these elements may not be exactly aligned, such that an optical axis may not be easily defined for the whole arrangement. However, a forward direction may still be defined through the center of the light input surface  20  and the light output surface  22 , e.g. as shown in  FIG. 10   a.    
     The TIR body  14 , as shown in  FIG. 1 ,  FIG. 2 , is formed in one piece. Three portions arranged one behind the other in the forward direction may be identified, namely an input collimator portion  26 , a beam spreading portion  28  with a central cavity  30 , and a lens adaptation portion  32 . A separation of the three portions  26 ,  28 ,  32  is schematically designated in  FIG. 1 ,  FIG. 2  by vertical lines. 
     Exterior surfaces of the TIR body  14  can serve as reflection surfaces for light guided within the TIR body  14  if struck by light at an angle below the angle of total reflection. Using this effect, the TIR body  14  is shaped to achieve the desired shaped beam  24 .  
     The collimator portion  26  is shaped as a cut-off pyramid with substantially square base. The light input surface  20  is square and corresponds to the size of the light emitting surface of the LED  12 . From the light input surface  20 , the input collimator portion  26  widens both laterally and vertically in the forward direction. 
     The lens adaptation portion  32  comprises the light output surface  22 . In order to adapt to the lens  16 , the light output surface  22  has concave shape. 
     The beam spreading portion  28  comprises left and right wing portions  50   a ,  50   b  to both lateral sides of the central cavity  30  and an arch shaped bridge portion  38  extending over the cavity  30 . 
     The input beam of light at the light input surface  20  is divided into a center beam  34 , shown in  FIG. 1 ,  FIG. 2  in dashed lines, and left and right peripheral beams  36 , shown in dotted lines. 
       FIG. 2  shows how the center beam  34  and the peripheral beams  36  are separated within the TIR body  14  in the height direction H. Light portions emitted upward form the central beam  34 , whereas light portions emitted substantially horizontally or downward form the peripheral beams  36 . 
     The center beam  34  is conducted within the bridge portion  38  arranged parallel to the optical axis  18  in the center of the beam spreading portion  28  of the TIR body  14 . The bridge portion  38  is an arch shaped light guide for guiding the center beam  34  from the input collimator portion  26  to a center portion  46  of the light output surface  22  at the lens adaptation portion  32 . 
     Left and right peripheral beams  36  are guided, as shown in  FIG. 2 , within the beam spreading portion  28  of the TIR body  14  below the bridge portion  38 . The cavity  30  is formed like a wedge, its front edge being arranged on the optical axis  18  and two front surfaces  40   a ,  40   b  extending laterally from the front edge under an oblique angle to the optical axis  18 . The front surfaces  40   a ,  40   b  reflect the peripheral beam  36  due to total internal reflection. The peripheral beam  36  is separated at the front edge of the cavity  30  into left and right peripheral beams reflected to both lateral sides. 
     Both peripheral beams  36  are again reflected at outer surfaces  42   a ,  42   b , of the wing portions  50   a ,  50   b . The surfaces  42   a ,  42   b  are also arranged at an oblique angle to the optical axis  18  such that, as shown in  FIG. 1 , the peripheral beams  36  at the light output surface  22  are directed substantially parallel to the optical axis, but pass through laterally peripheral portions  44   a ,  44   b  of the light output surface  22 .  
     The resulting shaped beam  24  emitted at the light output surface  22  is thus composed of the center beam  34  emitted at the center portion  46  of the light output surface  22  and the peripheral beams  36  emitted at the laterally peripheral portions  44   a ,  44   b  thereof. 
     The resulting shaped beam  24  is thus laterally spread out over the width of the light output surface  22 , thus substantially wider, in the example more than 15 times, compared to the square light emitting surface of the LED  12 . In the height direction H, the resulting shaped beam  24  has roughly the same or only slightly larger extension compared to the LED  12 . 
       FIG. 3  shows a second embodiment of a TIR body  100  in a perspective view. Other views of the TIR body  100  are shown in  FIGS. 4-7 . The TIR body  100  generally corresponds to the TIR body  10  according to the first embodiment. Similar or comparable parts thereof will be designated by like reference numerals. 
     The TIR body  100  comprises an input collimator portion  26  with a square light input surface  20 , and a beam spreading portion  28  with wing portions  50   a ,  50   b  extending to both lateral sides of the forward direction  18 . The beam spreading portion  28  includes a central cavity  30 . A bridge portion  38  is arranged above the central cavity  30 . In the example shown in  FIGS. 3-7 , the TIR body  100  does not have a specially shaped lens adaptation portion with concave shape. The beam spreading portion  28  terminates in a plane light output surface  22 . 
     The beam spreading portion  28  includes, arranged on top of the wing portions  50   a ,  50   b , right and left top wing portions  52   a ,  52   b.    
     The TIR body  100  is designed in the same way as the TIR body  10  according to the first embodiment to receive light from an LED light source  12  at the light input surface  20  and shape a laterally spread output beam  24  thereof by separating beam portions in height direction and guiding them towards different portions of the light output surface  22 . 
     Exemplary beam paths are shown in  FIG. 8 ,  FIG. 9 , including first left peripheral beam  35  shown as dotted lines (symmetrical first right peripheral beam not shown for clarity), second right peripheral beam  36  shown as slash-double-dotted lines (symmetrical second left peripheral beam not shown for clarity), and a central beam  34  shown as a dashed line. 
     As shown in  FIG. 9 , the central beam  34  and the first and second peripheral beams  35 ,  36  follow different beams paths within the TIR body  100  separated in the height direction. Light emitted from the light input surface  20  into upper directions forms the central beam  34  centrally guided along the bridge member  38  to the central portion  46  of the light  output surface  22 . Light emitted substantially horizontally forms the left and right first peripheral beams  35 , whereas light emitted into lower directions forms the left and right second peripheral beams  36 . 
     The peripheral beams  35 ,  36  are guided within the beam spreading portion  28  of the TIR body  100  as shown in  FIG. 8 . As in the previously discussed example, the shape of the beam spreading portion  28  is laterally symmetrical, so that the peripheral beams  35 ,  36  will divide at the front edge of the cavity  30  into left and right beam portions. In order to better illustrate the beam paths,  FIG. 8  shows only the left portion of the first peripheral beam  35  and the right portion of the second peripheral beam  36 . 
     The first peripheral beam  35  is divided at the front edge of the cavity  30  to be reflected at the reflective surfaces  40   a ,  40   b  into left and right lateral directions. The thus reflected light of the left and right first peripheral beams  35  is then again reflected at outside surfaces  54   a ,  54   b  of the top wing portions  52   a ,  52   b  of the beam spreading portion  28 . After the second reflection, the first peripheral beams  35  are again substantially parallel to the forward direction  18  and emitted through inner peripheral portions  44  of the light output surface  22 . The inner peripheral portions  44  directly border the central portion  46 , such that the shaped beam  24  is emitted through the light output surface  22  continuously in the lateral directions. 
     As shown in  FIG. 9 , the second peripheral beams  36  are guided within a lower portion of the TIR body  100 , such that in the height direction H the first peripheral beams  35  are arranged between the center beam  34  and the second peripheral beams  36 . 
     The second peripheral beam portions  36  are also reflected twice, first at the front surfaces  40   a ,  40   b  of the cavity  30  and subsequently at side surfaces  42   a ,  42   b  of the wing portions  50   a ,  50   b . A thus reflected beam  36  is directed substantially parallel to the forward direction  18  and emitted through outer peripheral portions  45  of the light output surface  22 . 
     The outer peripheral portions  45  are arranged laterally further outward relative to the forward direction  18 , such that the inner peripheral portions  44  are arranged laterally in between the center portion  46  and the outer peripheral portions  45 . 
     The light emitted from the LED  12  is spread out broadly in both lateral directions. The spread beam  24  is composed of contributions from the central beam  34  emitted at the center portion  46 , the left and right first peripheral beams  35  emitted at inner peripheral portions  44  of the light emitting surface  22 , and the left and right second peripheral beams  36  emitted at outer peripheral portions  45 . The TIR body  100  is shaped  such that all of the light output surface  22  is illuminated, i.e. the shaped beam  24  is continuous in the lateral direction. 
     As explained, the spread of the beam  24  as compared to the light emitting surface of the LED  12  is achieved by separating different beam portions in the input collimator  26  by their height direction, i.e. by their angle of inclination relative to the forward direction  18  and guiding the respective beam portions  34 ,  35 ,  36  along the described beam paths towards the light output surface  22 . As shown in  FIG. 9 , the different beam portions  34 ,  35 ,  36  converge again in the height direction H towards the light output surface  22 . Thus, the output beam  24  may have the same height dimension as the light output surface of the LED  12 , or may be only slightly larger in the height direction H. 
       FIG. 10  shows a third embodiment of the TIR body  110 . The TIR body  110  corresponds in shape to two of the TIR bodies  100  described above arranged side by side. Similar or comparable parts will be designated by like reference numerals. 
     Each of the halves of TIR body  110  comprises an input collimator  26  and beam spreading portions  28  with wing portions  50   a ,  50   b , top wing portions  52   a ,  52   b , and bridge portions  38 . Light output surfaces  22  are formed at concave lens adaptation portions  32 . 
     The TIR body  110  may be used in a vehicle headlamp with two separate LED light sources arranged in front of the light input surfaces  20 . Two separate lenses, or a double lens, may be arranged in front of the light output surfaces  22 . 
       FIG. 10 a    shows a longitudinal sectional view of the sectional plane corresponding to the plane A in  FIG. 10 . The relative arrangement of the input collimator  26 , the cavity  30  with one front surface  40   a  and the bridge member  38  above are shown. As further visible, the lens adaptation portion  32  widens in height direction H towards the output surface  22 . 
       FIG. 10 b , 10 c    show sectional view of the sectional planes B, C in  FIG. 10 , showing the shape of the wing portions  50   a ,  50   b  and top wing portions  52   a ,  52   b.    
     The light output surface  22  of the TIR body  110  is shown in the front view of  FIG. 11 . It is bordered by upper and lower front edges  56 ,  58  extending laterally. The lower edge  58  is projected by a projection lens to achieve an illumination beam with a light/dark boundary. In order to conform to regulations, the lower edge  58  has a particular asymmetrical shape to achieve a light/dark boundary with a horizontal portion and an inclined portion. At the center of the light output surface  22 , the lower edge  58  comprises an inclined edge  portion  58   b  adjacent to a substantially horizontal edge portion  58   a . In the projected beam, this causes the desired horizontal/inclined light/dark boundary. 
     It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodiments without departing form the scope of the dependent claims. 
     For example, applying the above described concept of first separating beam portions by height or direction of inclination, and then directing the corresponding beam portions to different lateral portions of a light output surface, a skilled person will be able to propose many different shapes of a TIR body. In particular, the relative dimensions of the light input and light output surface of the TIR body may differ. For example, the height of the light output surface of the TIR body may be even less than the height of the light input surface. 
     While the described embodiments show symmetrical arrangements, it is also possible to provide laterally non-symmetrical lighting arrangements. The input beam may be divided in the height direction into two, three, or more different beam portions. 
     While the above embodiments rely on a TIR body, the same concept may also be realized by correspondingly arranged reflector surfaces, such that the beam portions travel through air rather than in the interior of a TIR body. 
     In the claims, any reference signs place between parentheses shall not be construed as limiting the claim. The word “comprising” does not exclude the presence of elements or steps other than those listed in the claim. The word “a” or “an” preceding an element does not exclude the presence of a plurality of such elements. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.