Abstract:
An exterior automotive lamp may be formed with LED light sources by efficiently using the available light. The LEDs are arranged in an array to illuminate a central lens to produce the horizontal spread from the central portion of the LED beam. Meanwhile a reflector gathers the more disperse side-emitted portion of the LED beam and directs that light as an outer sheath to form a supplementary portion of the beam. The lamp efficiently provides a beam that may be adapted for highbeam, lowbeam, fog, or signal purposes.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The Applicants hereby claim the benefit of their provisional application, Ser. No. 60/854,011 filed Oct. 24, 2006 High Efficiency Automotive LED Optical System. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to electric lamps and particularly to automotive lamps. More particularly the invention is concerned with automotive lamps using light emitting diodes as light sources. 
     2. Description of the Related Art Including Information Disclosed Under 37 CFR 1.97 and 1.98 
     BRIEF SUMMARY OF THE INVENTION 
     A high efficiency automotive LED optical system can be made with a reflector with a reflective inner surface defining a cavity with an open end facing a field to be illuminated. The reflective surface includes at least a parabolic reflector portion having a focal point. An LED light source array is positioned to emit light into the cavity and arrayed to project light horizontally about a lamp axis directed towards the field to be illuminated. The LED light source array includes one or more LEDs arrayed horizontally. The LED light source array is positioned to span the focal point. A light transmissive, refractive inner lens is positioned axially and intermediate the LED light source array and the field to be illuminated; and is positioned intermediate the reflector and the field to be illuminated. The inner lens is sized and positioned to intercept less than all of the light emitted by the LED light source array; and the reflector is positioned to intercept the remaining light emitted by the LED light source array. The inner lens has a front optical surface having a vertical cross section, and a rear optical surface having a vertical cross section such that the lens refracts light received by the rear optical surface from the LED light source array and projected from the front optical surface to within plus or minus 5 degrees of a horizontal plane through the lamp. The front optical surface has a horizontal cross section, and the rear optical surface has a horizontal cross section such that the lens refracts light received by the rear optical surface from the LED light source array and projected from the front optical surface spread horizontally from the axis. The reflector directs the remaining intercepted light from the LED light source array to provide a supplementary horizontal pattern. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         FIG. 1  shows a schematic front view of an automotive LED optical system. 
         FIG. 2  shows a schematic top view of a horizontal axial cross section of an inner lens. 
         FIG. 3  shows a schematic side view of a vertical axial cross section of an inner lens. 
         FIG. 4  shows a schematic low beam light pattern. 
         FIG. 5  shows a schematic top view in cross section of an alternative inner lens. 
         FIG. 6  shows a schematic top view in cross section of an alternative inner lens. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  shows a schematic front view of a high efficiency automotive LED optical system  10 .  FIG. 2  shows a schematic top view of an axial cross section of an inner lens.  FIG. 3  shows a schematic side view of an axial cross section of an inner lens. The high efficiency automotive LED optical system  10  comprises an LED light source array  12 , an inner lens  14  and a reflector  16 . 
     The LED light source array  12  may be a single LED light source or an array of plural LED light sources. The LED light source array  12  emits light with a distribution about a lamp axis  18 , and generally towards a field to be illuminated. The LED light source array  12  is specifically positioned to emit light toward the inner lens  14  and the reflector  16 , which are in turn aligned to project light horizontally along a lamp axis  18  towards a field to be illuminated. In the preferred embodiment the LED light source array  12  is a horizontal aligned row of closely spaced LEDs, and in particular a horizontal row of five LEDs each facing axially towards the field to be illuminated. 
     The inner lens  14  is optically configured to substantially refract light received from the LED light source array  12  to be in or to the lower side of a horizontal plane through the lamp assembly  10 . The light transmissive, refractive inner lens  14  is positioned axially and intermediate the LED light source array  12  and the field to be illuminated. The inner lens  14  is positioned roughly in front of the LED light source array  12 , and offset from the reflector  16  leaving a surrounding gap  52  between the inner lens  14  and the reflector  16 . The inner lens  14  is further sized to intercept a large portion, but less than all of the light emitted by the LED light source array  12 . In one embodiment the inner lens  14  was sized and positioned to intercept light emitted from the LED light source array  12  that had a vertical angle  22  about the horizontal (positive and negative) of 45 degrees or less (90 degrees total). The inner lens  14  was similarly sized and positioned to intercept light emitted from the LED light source array  12  that had a horizontal angle  24  about the median (positive or negative) of 60 degrees or less (120 degrees total). The inner lens  14  is optically shaped to refract light received from the LED light source array  12  in a horizontal band  62  extending at or below the horizontal. plane  60 . The refracted horizontal band  62  forms a substantial portion of a headlamp beam pattern. 
       FIG. 2  shows a schematic top view of a horizontal, axial cross section of an automotive LED lens  14 . The preferred lens  14  has a straight, central section  26  centered on the median, and extending horizontally transverse to the median and lamp axis  18  leading to a right side end  28  and to a left side end  30 . The central section  26  extends horizontally sufficiently to orthogonally span the LED light source array  12 . The center of the LED emitted beam is then passed substantially straight through the central section  26  towards the field to be illuminated. 
     The front surface  34  of the right side end  28  is circularly arced about the LED light source array  12  to approach the reflector  16  in the horizontal plane. The circular arc of the right side end of the front surface may be centered any where along the LED light source array, but is preferably centered at the right side end  29  of the LED light source array. It is understood that while actually centered is ideal, an offset of several LED diameters likely to be the practical range of a functional assembly and therefore is acceptable in defining “centered” here. The rear surface  36  of the right side end  28  may be circularly arced about a point between the right end  29  of the LED light source array  12  and the right end of the front surface  34  of the right side of lens orthogonally projected onto the line of the LED light source array  12 , for example, midpoint  38 . The right side front surface  34  and rear surface  36  then form a right side lens that spreads light to the right. 
     The lens  14  is further extended on the right side to approach the reflector  16  in the horizontal plane for attachment. The right side end  28  may include a coupling to latch to the reflector  16  or to extend through a passage formed in the reflector  16  to latch to a support in or behind the reflector  16 . For example, an approximately axially extending leg  40  formed with a clip coupling formed on an end of the leg  40  may flexibly latch to a hole in the reflector  16 . The extended leg  40  portions of the lens  14  may be formed to be resilient, and thereby sufficiently compressible to spring latch in corresponding receptacles formed in the reflector  16  or a similarly convenient support. The left side end  30  of the lens  14  may be similarly formed. 
       FIG. 3  shows a schematic side view of a vertical, axial cross section of an automotive LED lens. The lens includes a rear surface  42  facing the LED light source array  12 . The preferred rear surface  42  of the center portion looking in a vertical plane has the form of a circular radius  44  with the center point of the radius  45  located at, along or adjacent the LED light source array  12  (roughly centered). The lens  14  includes a front surface  46  facing the field to be illuminated. The preferred front surface  46  of the center portion looking in a vertical cross section, has the form of an elliptical section whose major axis is in the horizontal plane, having one foci  45  of the ellipse located at, along or adjacent the LED light source array  12  (again roughly centered). 
     The front surface  46  of the arced right side ( 28 ) of the lens is similarly formed (vertical cross section pivoted from the axis about a point along the LED light source array, such as the end point  29  of the light source array) with an elliptical surface with one foci of the ellipse located at, along or adjacent (roughly centered on) the right side end  29  of the LED light source array  12 . In effect, looking at the vertical section, the front optical surface  46  of the central section is dragged around the right side front arc, that is circularly rotated about the LED light source array  12  at the right side end  29  of the lens  14 . The preferred left side the lens  14  may be similarly formed (mirrored symmetry). 
       FIG. 5  shows a schematic top view in cross section of an alternative inner lens  70 . The front surface  72  is formed the same as in  FIG. 2 and 3  with an elliptical section in vertical cross section, and in horizontal cross section a straight central section  74  with circularly arced side sections  76 ,  78 . The side sections  76 ,  78  are arcs pivoted on the respective ends of the LED light source array through an arc  80  of 45 degrees from the axis  69 . The rear surface  82  in vertical cross section is a circular section centered on the LED light source array (the same as radius  44  in  FIG. 3 ). The rear surface  82  in horizontal cross section has a straight central section  84  with circularly arced side sections  86 ,  88 . The side sections  86 ,  88  are arcs pivoted on the respective side ends of the LED light source array  87  through an arc  80  of 45 degrees from the axis  69 . The front surface  72  and rear surface  82  are designed to refract light from the LED light source array into a horizontal plane centered on the LED light source array. Because of the actual LED vertical width, the vertical spread from the horizontal plane may be functionally about 4 or 5 degrees. The front surface  72  and rear surface  82  are designed to spread light from the LED light source horizontally about the axis  69  about plus or minus 45 degrees (90 degrees total). Because of the LED light emitting array width, the horizontal spread from the axial is about 100 degrees. 
       FIG. 6  shows a schematic top view in cross section of an alternative inner lens  100 . The front surface  102  is formed the same as in  FIGS. 2 and 3  with an elliptical section in vertical cross section, and in horizontal cross section a straight central section  104  with circularly arced side sections  106 ,  108 . The side sections  106 ,  108  are arcs horizontally pivoted on the respective ends  105 ,  107  of the LED light source array  130  through an arc  110  of 45 degrees from the axis  112 . The rear surface  114  in vertical cross section has a circular section centered on the LED light source array  130 , as in  FIG. 3 . The rear surface  114  in horizontal cross section is a straight central section  116  with B-spline arced side sections  118 ,  120 . A side section  120  is determined by a first drive line  122  having an angle  124  of 18 degrees to the central section  116  (72 degrees from the axis  112 ), and a second drive line  126  having an angle  128  of 12 degrees to the 45 degree side angle (123 degrees from the axis  112 ). A B-spline is a continuous arc that is tangent at each respective end to the respective drive line. Intermediate the ends, the B-spline arc has a regular transition from the slope of the first drive line  122  to the slope of the second drive line  126 . B-splines are well known in the engineering arts. The front surface  102  and rear surface  114  are designed to refract light from the LED light source array  130  into a horizontal plane centered on the LED light source array  130 . Because of the LED vertical width, the vertical spread from the horizontal plane is actually about 4 to 5 degrees. The front surface  102  and rear surface  114  are designed to spread light from the LED light source  130  horizontally about the axis  112  about plus or minus 22.5 degrees (45 degrees total). Because of the LED light emitting array  130  width, the horizontal spread from the axis  112  is about 55 degrees. The inner lens may include additional refractory elements such as an outer ring to blend the lens provided beam and the reflector provided beam. 
     The reflector  16  has a reflective inner surface  48  defining a cavity  50  with an open end facing along an axis  18  towards the field to be illuminated. The reflector  16  may be molded plastic shell with a metallized reflective surface as is known in the art. The reflector  16  is positioned to surround the inner lens  14 , but is offset from the inner lens  14  to provide an optical gap  52  between the inner lens  14  and the reflector  16  through which light emitted by the LED light source array  12  and reflected by the reflector  16  passes. The preferred reflector  16  is sized to intercept a substantial portion, but less than all of the light emitted by the LED light source array  12 . The reflector  16  is optically shaped to project light emitted by the LED light source array  12  and intercepted by the reflector  16  in a second pattern different from the first pattern formed by the inner lens  14 . Ideally the second pattern is supplementary to the first pattern so the combined patterns form a desired headlamp beam. The preferred reflector  16  is optically shaped to reflect light received from the LED light source array  12  into a supplementary pattern  64  or similar pattern supplementary to the inner lens  14  generated beam pattern, such as the horizontal band  62 . The preferred reflector  16  includes one or more optical portions having the form of a section of a paraboloid of revolution  48  that defines a foci. The LED light source array  12  is located at or adjacent the foci. The section of the paraboloid of revolution  48  is oriented to direct light horizontally to form the supplementary beam pattern, such as the supplementary pattern  64  portion of the headlamp beam. It is understood the first pattern and the second pattern may overlap. In the preferred embodiment the reflector  16  includes seven vertical bands, horizontally arrayed, each band being a section of a paraboloid of revolution having a focal point located at or near the light source, thereby yielding a beam pattern spread at or below the horizon line. The preferred seven vertical bands direct light received through the gap  52  between the inner lens  14  and the reflector  16  towards as a supplementary pattern  64  portion of the final beam pattern. 
     The inner lens  14  then captures the generally forwardly emitted light, perhaps half the emitted LED light, and forms the horizontal spread pattern, emitted from the center or core of the LED light source array  12  beam. The reflector  16  efficiently gathers the generally sideward emitted LED light, and forms the rest of the beam pattern as a sheath coming around the inner lens  14 . The reflector  16  generated beam pattern then supplements inner lens  14  generated pattern. Little of the available light is then lost or mis-direct and only one reflection or refraction is need for each emitted ray. 
     While there have been shown and described what are at present considered to be the preferred embodiments of the invention, it will be apparent to those skilled in the art that various changes and modifications can be made herein without departing from the scope of the invention defined by the appended claims.