Abstract:
A compact optical assembly includes a linear array of LEDs and a plurality of reflectors. The reflectors include two concentric reflecting surfaces that surround the LED light sources. The inner reflecting surface reflects the majority of the light emitted from the LED light source and the outer reflecting surface reflects light emitted through longitudinal channels in the inner reflecting surface. The concentric reflecting surfaces cooperate to create a wide-angle beam of light with a desired dispersion pattern.

Description:
BACKGROUND 
       [0001]    This disclosure relates generally to LED light sources, and more particularly, to a reflector for use with an LED lamp. 
         [0002]    It is traditional to arrange lights on a vehicle to perform a variety of functions, including fog lighting, warning lighting, spot lighting, takedown lighting, scene lighting, ground lighting, and alley lighting. Emergency vehicles such as police, fire, rescue and ambulance vehicles typically include lights intended to serve several of these functions. Generally speaking, larger lights are less useful than smaller lights because of limited mounting space on the vehicles, as well as aerodynamic and aesthetic considerations. The trend is toward very bright, compact lights which use LEDs for a light source. 
         [0003]    Prior art optical configurations may not provide acceptable performance when the size of the light is reduced. These smaller configurations make it particularly difficult to provide focused beams of light of a desired intensity. Traditional optical configurations are limited by symmetrical surfaces of rotation that require a larger optical assembly than desired due to the required reflecting surfaces. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0004]      FIG. 1  is a top plan view of one embodiment of an optical assembly according to aspects of the disclosure; 
           [0005]      FIG. 2  is a partial side sectional view of the optical assembly of  FIG. 1  taken along line A-A thereof; 
           [0006]      FIG. 3  is a side sectional view of the optical assembly of  FIG. 1  taken along line B-B thereof; 
           [0007]      FIG. 4  is an enlarged partial top plan view of the optical assembly of  FIG. 1 ; 
           [0008]      FIG. 5  is a partial side sectional view of the optical assembly of  FIG. 1  taken along line B-B thereof, depicting light ray tracing; 
           [0009]      FIG. 6  is a top plan view of the optical assembly of  FIG. 1  including one embodiment of a lens according to aspects of the disclosure; 
           [0010]      FIG. 7  is a side plan view of the lens of  FIG. 6 ; and 
           [0011]      FIG. 8  is a side sectional view of the lens of  FIG. 6  taken along line C-C thereof. 
       
    
    
     DETAILED DESCRIPTION 
       [0012]    Referring to  FIG. 1 , one embodiment of the optical assembly  2  comprises a plurality of reflectors  4  arranged along line A-A. LED light sources  6  are generally disposed in the center of the reflectors  4 . Reflectors  4  redirect a portion of the light emitted from the LED light sources  6  into a desired illumination pattern. For clarity purposes, the longitudinal direction is defined as along line A-A and the lateral direction is defined as along line B-B. Longitudinal axis A L  is defined on plane one P 1  along line A-A. 
         [0013]    Referring to  FIG. 2 , LED light source  6  emits light in a hemispherical emission pattern to one side of first plane P 1 , surrounding optical axis A O . Optical axis A O  is perpendicular to the first plane P 1 . The reflector  4  comprises two concentric reflecting surfaces that are generally surfaces of rotation about the optical axis A O . 
         [0014]    In the depicted embodiment, the reflector  4  has an inner reflecting surface  10  and an outer reflecting surface  20 . The inner reflecting surface  10  extends from an inner end  12  at first plane P 1  to an outer end  14 . The outer reflecting surface  20  extends from a first end  22  to a second end  24 . In the depicted embodiment, plane one P 1  is axially closer to the second end  24  than the outer end  14 . The axial height of inner reflecting surface  10  is defined as H 1  and the axial height of outer reflecting surface  20  is defined as H 2 . In the depicted embodiment, the ratio of H 1  to H 2  is approximately 1.5. This ratio may differ depending on the desired light emission for the particular application. 
         [0015]    Referring to  FIG. 3 , the inner reflecting surface  10  is defined by a curve  15  of a parabola having a focus at LED light source  6  rotated about optical axis A O . The inner reflecting surface  10  has two windows  16  disposed generally opposite one another in about longitudinal axis A L . In other embodiments, the curve  15  is aspheric and arcuate but not a portion of a parabola. 
         [0016]    Referring to  FIG. 2 , the windows  16  allow light to reflect on the outer reflecting surface  20 . Between windows  16  are lateral tabs  18  that reflect light emitted in the lateral direction. Light rays emitted from the LED light source in the lateral direction reflect on the tabs  18  of inner reflecting surface  10 . This creates a wide-angle beam of light that is focused about the longitudinal axis A L . 
         [0017]    The outer reflecting surface  20  is defined by a curve  25  of a parabola having a focus at LED light source  6  between a first end  22  and a second end  24  generally rotated about the optical axis A O . The first end  22  is defined axially by a light ray  26  that originates at the LED light source and passes through the longitudinal slot  16  of the inner reflecting surface  10  at plane one P 1 . In other embodiments, the curve  25  is aspheric and arcuate but not a portion of a parabola. 
         [0018]    Light emitted from the LED light source  6  may be characterized as either “wide angle” light  30  or “narrow angle” light  32 . The longitudinal direction is defined as within a trajectory of α degrees from longitudinal axis A L . In the embodiment depicted in  FIG. 4  α is approximately 55 degrees, and may range from 30 to 80 degrees.  FIG. 5  depicts the “wide angle” and “narrow angle” light in greater detail. “Wide angle” light  30  is defined as light that is reflected by the outer reflecting surface  20  when directed in the longitudinal direction. “Wide angle” light  30  has a trajectory greater than approximately δ degrees from optical axis A O . In the depicted embodiment δ is approximately 63 degrees, and may range from 55 to 75 degrees. “Narrow angle” light  32  is defined as light that is reflected by the inner reflecting surface  10  when directed in the longitudinal direction. “Narrow angle” light  32  has a trajectory less than approximately Λ degrees from optical axis A O . In the depicted embodiment, Λ is approximately 57 degrees, and may range from 45 to 65 degrees. 
         [0019]    Some “narrow angle” light is emitted from the optical assembly without being handled by either the inner or outer reflecting surfaces. “Narrow angle” light that has a trajectory less than θ degrees from the optical axis A O , is not handled by either reflecting surface. In the depicted embodiment, θ is approximately 27 degrees, and may range from 10 to 40 degrees. The light that exits the center of the optical assembly without being handled by the inner reflecting surface is generally already traveling substantially in the desired direction. Although this light is divergent from the optical axis A O , the angle θ is chosen depending on the specific application. 
         [0020]    Some “wide angle” light emitted in the longitudinal direction is not handled by the outer reflecting surface. “Wide angle” light emitted in the longitudinal direction that has a trajectory greater than ε degrees from the optical axis A O  is not handled by the outer reflecting surface. In the depicted embodiment, ε is approximately 83 degrees. Very little light is emitted from LED light sources in the horizontal direction (ε equal to 90 degrees). The value of angle c is chosen depending on the specific LED light source and needs of the light dispersion pattern. Angle ε may range from 70 to 90 degrees. 
         [0021]    In one embodiment, the outer reflecting surface  20  is interrupted, in the lateral direction, by support members  28 . Referring to  FIG. 4 , the support members  28  are defined by angle β relative to longitudinal axis A L . In the depicted embodiment, angle β is approximately 60 degrees, and may range from 40 to 80 degrees. The support members  28  allow for a narrower reflector  4  in the lateral direction that nevertheless reflects LED light sources  6  in the desired pattern and intensity. 
         [0022]    In the embodiment depicted in  FIGS. 6-8 , a collimating lens  40  refracts a portion of the light within θ degrees from optical axis A O . Referring to  FIG. 8 , light entry surface  42  and light emission surface  44  of lens  40  cooperate to refract the “narrow angle” light divergent from optical axis A O  into a direction substantially parallel to optical axis A O . In one embodiment, the diameter of lens  40  is dependent on θ and H 1 , and is designed to capture and refract a majority of the light not handled by the inner reflecting surface  10 . In one embodiment, the lens  40  redirects light divergent from longitudinal axis A L  into a direction substantially parallel with the longitudinal axis A L . This creates a wide-angle beam of light that is focused about the longitudinal axis A L .