Abstract:
An emergency vehicle light fixture includes, among other things, an elongated body having a reflective surface formed by a series of alternating linear and revolved parabolic segments. The series of alternating linear and revolved parabolic segments are coextensive along the height of the reflective surface and have an optical axis. Each of the alternating linear and revolved parabolic segments has a focal point that lies along a common axis that is orthogonal to the optical axis.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a National Phase application of International Application No. PCT/US2013/049892, filed Jul. 10, 2013, which claims the benefit of U.S. Provisional Application Ser. No. 61/669,834 filed Jul. 10, 2012, which is incorporated herein by reference in its entirety. 
    
    
     BACKGROUND 
     This invention relates to lighting and illumination fixtures for emergency vehicles. In one of its aspects, the invention relates to a light bar fixture with multiple LED light sources and a reflector to project directional light. In another of its aspects, the invention relates to a light assembly of one or more reflectors for a light bar fixture. 
     Stopa et al. U.S. Pat. No. 6,641,284 discloses an LED light assembly that includes a parabolic reflector and a linear array of LEDs arranged on the focal axis of the reflector. An optional collimating lens is arranged in front of the reflector to collimate the light emitted from the reflector at less than a predetermine angle so that the light emitted by the LEDs either passes through the lens or is otherwise reflected from the reflector. A substantially collimated beam of light is said to form a band extending the longitudinal span of the reflector 
     Czajkowski U.S. Pat. No. 7,578,600 discloses a light assembly which can include an LED array and a reflector that has a central portion and a pair of end portions. The LED array includes LEDs which are positioned to define a focal axis and which emit light substantially along an optical output axis that is perpendicular to the focal axis. The optical output axis of the LED array can be disposed in an intersecting relationship with the reflector surface. The reflector can be defined by a curved section defined with respect to a principal axis. Each portion of the reflector has two or more sections, each of which is defined by a different mathematical equation. In one iteration, a reflector is formed from a composite of adjacent parabolic curve sections, each having a principle axis that is perpendicular to the optical output axis LEDs in front of the curved sections. Czajkowski US20070153530 discloses to a reflector which includes a linear curved section which may be defined by a parabolic equation and a plurality of parabolic sections which are positioned at the bottom part of the reflector. In addition, end reflectors are planar and are perpendicular to the back wall of the reflector. LEDs are mounted at the focal axis of parabolic sections and the parabolic sections are configured to direct a portion of the light from the LEDs to the center or H-V point of the beam pattern. The output axis of each LED is vertical and is thus perpendicular to the principal axis of the reflective surface. 
     SUMMARY OF INVENTION 
     According to the invention, an emergency vehicle light fixture comprising an elongated body having an optical axis and a continuous reflective surface formed by a series of alternating linear and revolved parabolic segments that are coextensive along the height of the reflective surface, each of which has a focal point that lies along a common axis that is orthogonal to the optical axis, wherein the elongated body extends parallel to the common axis, and wherein the alternating linear and revolved parabolic segments are joined at edges and alternated in a direction parallel to the common axis. 
     In one embodiment, the emergency vehicle light fixture further comprises an LED positioned at the focal point of one or more of the revolved parabolic segments. The revolved parabolic segments may be concave or convex with respect to the optical axis in orthogonal cross-section. 
     The emergency vehicle light fixture may further comprise revolved end reflector segments that flank the series of linear and revolved reflector segments. LEDs may be positioned at each of the focal points of the revolved end reflector segments. 
     The revolved parabolic segments may be defined by partial revolution of a line around the optical axis and then projected orthogonally to the optical and common axis onto a curve that is defined by a parabolic function. The the focus of the curve is preferably located at the intersection of the optical and common axes. Thus, each normal cross section through a revolved parabolic segment will be a curve with a common radius of curvature. 
     The revolved parabolic segments may be defined by a parabolic curve that modulated along the length thereof with a complex function such as a sinusoidal function. The complex function may be convex. Alternatively, the complex function may be concave. The sinusoidal function of at least some of the revolved parabolic segments may be convex along a portion of at least one of the revolved parabolic segments and concave along another portion of at least some of the revolved parabolic segments. 
     The linear parabolic segments may be linear with respect to the optical axis in orthogonal cross-section. 
     According to yet another embodiment, the emergency vehicle light fixture further comprises an LED positioned at the focal point of one or more linear and revolved parabolic segments wherein the output axis of the LEDs are positioned at an acute angle with respect to the axis orthogonal to the common axis and the optical axis. The acute angle may be greater than 0 degrees and less than 15 degrees. Alternatively, the acute angle may be greater than 8 degrees and less than 12 degrees. Alternatively, the acute angle may be about 10 degrees. 
     The linear and revolved parabolic segments may have a common parabolic function. The common parabolic function may be aspheric or conic. The parabolic function may be modulated with a sinusoidal or other complex function. 
     The emergency vehicle light fixture may further comprise revolved end reflector segments that flank the series of linear and revolved reflector segments. The revolved end reflector segments may comprise a series of reflector segments that are defined by rotating a parabolic curve about a common point at the intersection of the end reflector segments. 
     The emergency vehicle light fixture may further comprise an LED positioned at the focal point of one or more linear and revolved parabolic segments and further comprise an optical element that is positioned and configured to direct light rays emanating from the LED and not reflected by the reflective surface of the light fixture. 
     In yet another embodiment of the emergency vehicle light fixture, the parabolic surfaces form a mirror-symmetrical curve with respect to the optical axis. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the drawings: 
         FIG. 1  is a perspective view of an embodiment of a light assembly according to the present invention. 
         FIG. 2  is a partial horizontal cross-sectional view of the light assembly of  FIG. 1  taken along the line II-II through the reflector assembly. 
         FIG. 3  is a vertical cross-sectional view of the light assembly of  FIG. 1  positioned in a fixture housing and taken along the line III-III through a revolved reflector segment. 
         FIG. 4  is a vertical cross-sectional view of the light assembly of  FIG. 1  positioned in a fixture housing and taken along the line IV-IV through an linear reflector segment. 
         FIG. 5  is a perspective view of the light assembly of  FIG. 1  including a ray-traced representation of light emitted from two LED&#39;s interacting with the light assembly. 
         FIG. 6  is a candela distribution of the output in the horizontal plane of the single active interior LED in the light assembly of  FIG. 5 . 
         FIG. 7  is an isocandela plot of the output of the single active interior LED in the light assembly of  FIG. 5 . 
         FIG. 8  is a candela distribution of the output in the horizontal plane of the single active flanking LED and the end reflector in the light assembly of  FIG. 5 . 
         FIG. 9  is an isocandela plot of the output of the single active flanking LED and the end reflector in the light assembly of  FIG. 5 . 
         FIG. 10  is a perspective view of the light assembly of  FIG. 1 , including a ray-traced representation of light emitted from four interior LEDs interacting with the light assembly. 
         FIG. 11  is a candela distribution of the output in the horizontal plane of the four active interior LEDs in the light assembly of  FIG. 10 . 
         FIG. 12  is an isocandela plot of the output of the four active interior LEDs in the light assembly of  FIG. 10 . 
         FIG. 13  is an isocandela plot of the output of the LED array in the light assembly of  FIG. 1 . 
         FIG. 14  is the profile of an aspheric surface modulated with a sinusoidal function for a reflector in accordance with an embodiment of the invention. 
         FIG. 15  is the profile of an aspheric surface modulated with a filtered sinusoidal function for a reflector in accordance with an embodiment of the invention. 
         FIG. 16  is a perspective view of an additional embodiment of a light assembly according to the invention wherein the end reflector has a series of reflector segments that are swept about a common point at the intersection of the segments. 
         FIG. 17  is a perspective view of an additional embodiment of a light assembly according to the invention where the revolved concave reflector segments are placed vertically between revolved convex reflector segments. 
         FIG. 18  is an enlarged partial perspective view of the light assembly of  FIG. 18 . 
         FIG. 19  is a diagrammatic view of a revolved section of the reflector, illustrating the geometry of a concave revolved section according to the invention. 
         FIG. 20  is a diagrammatic view of a revolved section of the reflector, illustrating the geometry of a convex revolved section according to the invention. 
         FIG. 21  is a perspective view of an additional embodiment of a light assembly according to the invention wherein multiple light assemblies 10 are juxtaposed. 
         FIG. 22  is a perspective view of an additional embodiment of a light assembly according to the invention wherein multiple light assemblies 10 are juxtaposed. 
         FIG. 23  is a perspective view of an additional embodiment of a light assembly according to the invention where the parabolic surfaces form a mirror-symmetrical curve with respect to the optical axis. 
     
    
    
     DETAILED DESCRIPTION 
     An embodiment of a light assembly  10  according to the present invention is shown in  FIG. 1 . The light assembly  10  comprises a reflector array  12 , an LED array  14  and supporting structures upon which the reflector array and LED are integrated including the base  16  upon which they are mounted. The reflector array  12  of  FIG. 1  comprises a highly reflective material that is adhered to the surface of the reflector array  12  facing the LED array  14 . The profile of the reflective face of the reflector array  12  comprises alternating segments of revolved  18  and linear  20  surfaces that are flanked by revolved segments  22 . The LED array  14  includes a plurality of interior LEDs  24  flanked by an LED  26  at either end. 
     As shown in  FIG. 1 , the LED array  14  is aligned in a linear distribution of 18 LEDs evenly spaced along the horizontal axis  28 , herein referred to as the X-axis that is perpendicular to the optical axis  30  of the reflector array  12 , herein referred to as the Z-axis. Other embodiments may include a different number of LEDs. The distribution of the LEDs  24 ,  26  in the LED array  14  may also be curvilinear. Depending upon the embodiment of the light assembly  10 , the flanking LEDs  26  can be offset from the LED array  14  distribution. 
       FIG. 2  is a partial horizontal cross-sectional view of the light assembly  10  of  FIG. 1  taken through line II-II. The end reflector segment  22  is joined to a linear reflector segment  20  at a chamfered or filleted edge  214 . The alternating interior reflector segments  18 ,  20  are also joined by chamfered or filleted edges  212 . Each revolved interior reflector segment  18  is defined by a facet that is formed by partial revolution of a line around the Z-axis  30  and then projected orthogonally in the direction of the Y-axis  32  onto a curve that is defined by a parabolic function that preferably has its origin at the intersection of the Y-Z axes and the focal point on the X-axis, thus defining a curved horizontal profile with a focus of the effective output of an LED  24 . By placing the LEDs  24  at the focal point of the revolved segments  18 , the revolved segments collect light from the LEDs  24  and direct it along the Z-axis  30 . Each linear interior reflector segment  20  as shown in  FIG. 2  is defined by a parabolic curve that is projected along the X-axis and thus has a linear horizontal profile that is parallel to the X-axis  28 . The linear segments direct light from the LEDs  24  radially out from the Z-axis  30 . 
     Referring now to  FIG. 19 , the revolved segments  18  are formed as a concave downward facet  38  that is formed by partial revolution of a line around the Z-axis  30 . The concave downward facet  38  is then projected orthogonally in the direction of the Y-axis  32  onto a curve that is defined by a parabolic function  42  that preferably has its origin at the intersection of the Y-Z axes with the focus of the curve located at the intersection of the Z and X-axes  30 ,  28 , respectively. The upward projection of the segment  18  thus has a curvature that is defined by a function that imparts a curvature to the shape of the facet in the YZ plane. As shown, the revolved segment  18  follows a parabolic function  42  in a vertical profile. The revolved segment  18  can be formed by projecting the curved facet  38  onto a curve of any aspheric function to define the vertical profile. 
     The configuration of the light assembly  10  integrated into the transparent front  320  and rear housing elements  312  can be seen in vertical cross-section along lines III-III and IV-IV of  FIG. 1  in  FIGS. 3 and 4 . As shown in  FIGS. 3 and 4 , the LEDs  24  can be inclined from the Y-axis  32 ; that is, the axis that is orthogonal to the plane formed as the intersection of the X-axis  28  and the Z-axis  30 . That is, the output axis of the LEDs  24  may be positioned at an acute angle with respect to the axis orthogonal to the common axis (or X-axis  28 ) and the optical axis (or Z-axis  30 ). The flanking LEDs  26  can also be inclined. The inclination can range from 0 to 15 degrees where the axis of rotation is the X-axis  28  and the plane of rotation is both parallel to the plane formed as the intersection of the Z-axis  30  and the Y-axis  32  and bisects the LED  24 ,  26 . The acute angle may be greater than 0 degrees and less than 15 degrees. Alternatively, the acute angle may be greater than 8 degrees and less than 12 degrees. Alternatively, the acute angle may be about 10 degrees as embodied for the LEDs  24  in  FIGS. 3 and 4 . The LEDs  24  may be inclined to any angle depending upon the implementation. The components  310 ,  312 ,  314  of the light assembly base  16  are configured to offset the output axis of the LEDs  24  from the Y-axis  32 . 
     The revolved reflector segments  18  shown in  FIG. 3  and the linear reflector segments  20  shown in  FIG. 4  extend vertically along the Y-axis  32  in a parabolic profile. The focus of the parabolic surfaces is located on the X-axis  28 . As previously established in  FIG. 1 , the LED array  14  is also located on the X-axis  28 . The consequence of collocating the LED array  14  and the focus of the revolved reflector segments  18  is to collimate the emitted output by each LED  24  into a direction substantially along the Z-axis. The linear segments  20  direct light away from the Z-axis  30 . 
     Each alternating revolved and linear segment are joined by a chamfered or filleted edge  212  as shown in vertical profile in  FIGS. 3 and 4 . As a consequence of joining the revolved and linear segments  18 ,  20  at their upper edge  324 , the chamfered or filleted edges  212  have a surface profile that relaxes from strictly parabolic at its lower edge  322  to its upper edge  324 . The chamfered or filleted edges that result as a natural consequence of the manufacturing process have a diffusive effect on the distribution of the light intensity. Distributing light in many directions is desirable because it makes the light assembly visible from more viewing angles. 
     Additionally, the light assembly  10  may include an optical element  321  that is positioned and configured to direct light rays emanating from the LED. The position and configuration of the optical element  321  is preferably selected to direct light that has not been reflected by the reflective surface of the light assembly. That is, the optical element  321  may redirect light emanating from an LED that would not be reflected by the reflective surface of the light assembly. The optical element  321  may configured to gather light directly from the LEDs  24  or from the reflective surface of the light assembly. Additional considerations that effect the particular position and configuration of the optical element  321  may include redirecting light rays reflected from the reflective surface of the light assembly to effect a desired distribution of the light intensity. Additional optical elements may be provided on the inner surface of the outer lens housing  320 . Example optical elements may include, but not be limited to, a collimating lens, a holographic element and a diffractive element. 
     The light intensity output of the light assembly  10  is dependent upon the relative placement of the LED array  14 , the reflector array  12  and its constituent reflective elements  18 ,  20 ,  22 ,  212 ,  214 . A common method for determining performance of an optical system is to model the system in a computer with a geometrical ray-tracing program. Geometrical ray tracing for optical design is used to describe the propagation of light rays through an optical system like the light assembly  10 . Ray trace modeling provides a simulation technique that predicts the effective light output and performance of an optical system.  FIG. 5  is a perspective view of the light assembly of  FIG. 1  that includes a representation of the geometrical ray tracing for a simulation where two LEDs  24  are active and illuminating for the light assembly  10 . 
     The light intensity pattern of a single interior LED  24  at the output of the reflector assembly  12  is represented by the candela distribution plot in  FIG. 6 . The curve  610  represents the angular distribution of light intensity aligned with the horizontal structure of the reflector assembly  12 . This curve  610  shows that the reflector system illuminates a bright spot of light along the optical axis and spreads light radially out from the Z-axis  30 . 
     The profile and placement of the alternating segments of the reflector  18 ,  20  control the spreading and focusing of light intensity. The linear segments  20  direct light substantially off of the Z-axis  30 . The revolved segments  18  direct light along the Z-axis  30 . The overall effect of the reflector assembly  12  is to produce an illumination pattern that is substantially constrained vertically and substantially directed horizontally. An isocandela plot as in  FIG. 7  graphically represents the pattern of the light output from the single interior LED  24  illuminating through the reflector assembly  12 . Not to be confused with an intensity image of the light assembly, the isocandela plot is a graphical representation of the distribution of light intensity output from the assembly for a specific angular position of a detector. The isocandela plot demonstrates a strong central intensity  710  on the optical axis and a horizontal dispersion  712  indicative of the focal line contributions of the linear reflector segments  20 . This is a desirable characteristic because it makes the light assembly  10  visible for a viewer located off of the Z-axis  30  on the plane determined by the Z-axis  30  and the X-axis  28 . 
     The light intensity pattern of a single exterior LED  512  at the output of the reflector assembly  12  is represented by the candela distribution plot in  FIG. 8 . The curve  810  represents the angular distribution of light intensity aligned with the horizontal structure of the reflector assembly  12 . This curve  810  shows that the end reflector segment  22  substantially illuminates a bright spot of light along the optical axis; spreading light minimally out in a radial fashion from the Z-axis  30 . 
     The revolved end reflector segment  22  is defined by an aspheric or conic curve that is revolved about an axis parallel to the Z-axis and that passes through the LED  26  and contributes to the overall effect of the reflector assembly  12  by contributing more intense illumination along the Z-axis  30 . An isocandela plot as in  FIG. 9  graphically represents the pattern of the light output from the single exterior LED  24  illuminating primarily through the end reflector segment  22  of the reflector assembly  12 . The isocandela plot demonstrates a strong central intensity  910  on the optical axis. This intensity is a desirable characteristic because it makes the light assembly  10  appear brightest when viewed head-on. 
       FIG. 10  is a perspective view of the light assembly of  FIG. 1  that includes a representation of the geometrical ray tracing for a simulation where four interior LEDs  24  are active and illuminating for the light assembly  10 . More LEDs  24  are activated for the simulation to determine the scalability of the light output. Assuming proper positioning of the LEDs in the LED array, it is expected that as more LEDs  24  are activated, light output intensity will increase and that light output pattern will be well-behaved. For the light assembly  10  of the present invention, a well-behaved and desirable light output pattern will show a strong light output directed from a horizontal orientation that projects a strong central intensity along the Z-axis  30  that extends radially out from the Z-axis  30  horizontally along the X-axis  28  regardless of the number of LEDs  24  activated.  FIG. 11  is a candela distribution of the output in the horizontal plane for ray-tracing simulation of the light assembly  10  where four interior LEDs  24  are active and illuminating as shown in  FIG. 10 . This plot demonstrates the strong light intensity output  24  on the horizontal plane; that is the plane defined by the X-axis  28  and Z-axis  30 . The light output is strongest at  1112  directly along the Z-axis  30  and modulates to lower intensity at  1114  radially outward from the Z-axis  30 . 
     The isocandela plot shown in  FIG. 12  demonstrates the strong intensity at  1210  along the Z-axis  30 , the relatively wide horizontal spread of intensity at  1214  and the sharp vertical cutoff at  1216  when the four LEDs  24  are activated. The isocandela plot shown in  FIG. 13  demonstrates the strong intensity at  1218  along the Z-axis  30 , the relatively wide horizontal spread of intensity at  1220  and the sharp vertical cutoff at  1222  when the entire LED array  14  is activated. The overall beam pattern is more intense, or brighter, but the shape of the pattern remains stable as more LEDs are activated. 
     In other embodiments of the invention, the vertical surface profiles of the interior reflector segments  18 ,  20  are not limited to strictly parabolic profiles. However, for each embodiment of the invention, the interior reflector segments  18 ,  20  will have the same vertical surface profile that intersects a plane that is parallel to the coordinate plane formed from the Y-axis  32  and Z-axis  30  for a given embodiment. The end reflector segments  22  will be described by a single profile but may not be the same vertical profile as the interior segments. 
     As shown in  FIGS. 14 and 15 , the vertical surface profile of the reflector segments  18 ,  20 ,  22  will be aspheric or conic. A surface profile is aspheric or conic if it is not spherical or cylindrical. A common way to describe an aspheric or conic surface is given by the following equation: 
     
       
         
           
             
               z 
               ⁡ 
               
                 ( 
                 x 
                 ) 
               
             
             = 
             
               
                 
                   c 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   
                     x 
                     2 
                   
                 
                 
                   1 
                   + 
                   
                     
                       1 
                       - 
                       
                         
                           ( 
                           
                             1 
                             + 
                             k 
                           
                           ) 
                         
                         ⁢ 
                         
                           c 
                           2 
                         
                         ⁢ 
                         
                           x 
                           2 
                         
                       
                     
                   
                 
               
               + 
               
                 A 
                 ⁢ 
                 
                     
                 
                 ⁢ 
                 
                   x 
                   4 
                 
               
               + 
               
                 B 
                 ⁢ 
                 
                     
                 
                 ⁢ 
                 
                   x 
                   6 
                 
               
               + 
               
                 C 
                 ⁢ 
                 
                     
                 
                 ⁢ 
                 
                   x 
                   8 
                 
               
               + 
               
                 D 
                 ⁢ 
                 
                     
                 
                 ⁢ 
                 
                   x 
                   10 
                 
               
               + 
               
                 E 
                 ⁢ 
                 
                     
                 
                 ⁢ 
                 
                   x 
                   12 
                 
                 ⁢ 
                 
                     
                 
                 ⁢ 
                 … 
               
             
           
         
       
     
     where: 
     z is the aspheric or conic profile 
     k is the conic coefficient 
     x is the radial distance from the optical axis 
     c is the curvature defined as the inverse of radius 
     A, B, C, D, E . . . are the higher order aspheric coefficients 
     The conic coefficient, k, determines the general shape of the profile. A conic coefficient of 0 indicates a spherical surface. An elliptical surface has a conic coefficient ranging from 0 to −1. A parabolic surface has a conic coefficient of −1. A hyperbolic surface has a conic coefficient less than −1. 
     The higher order coefficients of the aspheric or conic equation are similar in construction to a Taylor series expansion such as that which defines sinusoidal functions like sine and cosine. A Taylor series expansion of cosine is shown by the following equation: 
     
       
         
           
             
               cos 
               ⁢ 
               
                   
               
               ⁢ 
               x 
             
             = 
             
               
                 
                   ∑ 
                   
                     n 
                     = 
                     0 
                   
                   ∞ 
                 
                 ⁢ 
                 
                   
                     
                       - 
                       
                         1 
                         n 
                       
                     
                     
                       
                         ( 
                         
                           2 
                           ⁢ 
                           n 
                         
                         ) 
                       
                       ! 
                     
                   
                   ⁢ 
                   
                     x 
                     
                       2 
                       ⁢ 
                       n 
                     
                   
                 
               
               = 
               
                 1 
                 - 
                 
                   
                     x 
                     2 
                   
                   
                     2 
                     ! 
                   
                 
                 + 
                 
                   
                     x 
                     4 
                   
                   
                     4 
                     ! 
                   
                 
                 - 
                 
                   
                     x 
                     6 
                   
                   
                     6 
                     ! 
                   
                 
                 + 
                 
                   
                     x 
                     8 
                   
                   
                     8 
                     ! 
                   
                 
                 - 
                 … 
               
             
           
         
       
     
     The vertical surface profile may be described by one of many functions depending upon the implementation. The above-described examples for the aspheric equation and the Taylor series expansion of a cosine function are merely illustrative and should not be considered limiting. For example, the vertical surface profile may be described by a function with both even and odd exponents. 
     Embodiments of the reflector segments  18 ,  20  may include a surface profile  1310  formed by a paraboloid modulated with a sine wave as shown in  FIG. 14 . The sinusoidal function can be filtered to produce additional embodiments of the reflector segments  18 ,  20 ,  22  such as the parabolic surface shown in  FIG. 15  modulated with the positive components of a sinusoidal function that produces a bumpy surface profile  1410 . 
       FIG. 16  is a perspective view of an additional embodiment of a light assembly according to the invention wherein the end reflector consists of a series of reflector segments  1710 ,  1712 ,  1714  that are defined by rotating a parabolic curve about a common point  1716  at the intersection of the segments. 
     Referring to  FIGS. 17 and 18 , LEDs  24  are placed at the focal point of a reflector segment  18  that is revolved around the Z-axis  30 . The vertical extent of the revolved segments  18  is limited to a length shorter than the height of the reflector assembly. Each revolved segment  18  is placed vertically to split a convex segment  34  that is defined by a sinusoidal function  36  along the X-axis parallel to the X-Z plane and defined vertically by the same aspheric or conic equation used for the previously described revolved  18  and linear  20  reflector segments. 
     As in previous embodiments, the revolved reflector segments  18  direct light substantially along the Z-axis  30  and the linear reflector segments  20  direct light substantially away from the Z-axis  30 . Because of their convex shape, the additional segments  34  defined by the swept sinusoidal function  36  that are placed above and below the revolved segments  18  defocus the light from the LED and substantially spread light off of the Z-axis  30 . 
     Referring to  FIG. 20 , the convex segments  34  are shown as a curved facet  40  that is revolved around the Z-axis  30  such that the nadir of the curve is located at the intersection of the Z- and X-axes  28 . The convex downward facet  40  is then projected up in the direction of the Y-axis  32  onto a curve  42  that is defined by an equation that preferably has its origin at the intersection of the Y-Z axes. The upward projection of the facet  34  is defined by a function  42  that forms the convex segment  34 . As shown, the convex segment  34  has a vertical profile that follows a parabolic function  42 . The convex segment  34  can be formed by projecting the curved facet  40  onto any aspheric function to define the vertical profile. 
     Multiple segments of the light assembly with a series of alternating linear and revolved concave or convex segments may be combined to form additional embodiments of the light assembly according to the present invention. The particular layout of the alternating linear and revolved segments may be identical or different among the light assembly segments depending upon the desired output light distribution. Similarly, the light assembly segments may be substantially parallel or configured about one or more axes of rotation.  FIGS. 21-23  show several embodiments of the light assembly that includes the combination of light assembly segments. The particular embodiments shown in  FIGS. 21-23  should not be considered limiting as they are intended to illustrate how the light assembly segments may be combined to produce an overall light assembly that can produce one of many desired output light distributions. 
       FIG. 21  is a perspective view of an additional embodiment of a light assembly according to the invention wherein multiple light assemblies are juxtaposed. Each section of the light assembly may include a series of alternating linear  20  and revolved parabolic concave and convex segments  18 ,  34  as previously described in  FIGS. 17 and 18 . The revolved end reflector segments  22  may be joined to form a continuous transition between the light assembly segments. The end reflector segments may be revolved or linear depending upon the relative orientation of the multiple light assemblies. In other words, the light assemblies may be juxtaposed such that each series of linear and revolved parabolic segments have unique common axes or each light assembly may be joined to form a long linear light assembly with a parallel common axis. Preferably, each light assembly segment may be joined where the end reflector segment  22  of a first light assembly segment intersects with the end reflector segment  22  of a second light assembly. 
     Additionally, linear parabolic segments  1810  may be integrated into the light assembly that share the same common axis as the alternating linear  20  and revolved parabolic concave and convex segments  18 ,  34  but with widths substantially different from the series of alternating parabolic segments. As shown, the long linear parabolic segment  1810  is equal in width to the entire series of alternating linear  20  and revolved parabolic concave and convex segments  18 ,  34 , but other widths are contemplated. While the light assembly in  FIG. 21  shows two light assembly segments juxtaposed, other numbers of light assembly segments are contemplated. For example, six segments may be joined such that the optical axes of the six segments substantially cover 180 degrees. In other words, a light assembly segment at one end of the overall light assembly has an optical axis rotated 180 degrees from the light assembly segment at the opposite end of the overall light assembly. 
       FIG. 22  is a perspective view of an additional embodiment of a light assembly according to the invention wherein multiple parabolic light assemblies are juxtaposed. Long linear parabolic segments  1910  are in place of the alternating series of linear  20  and revolved parabolic concave segments  18  shown in  FIG. 21 . The long linear parabolic segments  1910  provide a geometry that will advantageously direct a distribution of light away from the optical axis. Other placements of linear parabolic segments are contemplated and may be implemented depending upon the desired pattern of light with respect to the optical axis. 
       FIG. 23  is a perspective view of an additional embodiment of a light assembly according to the invention where the parabolic surfaces form a mirror-symmetrical curve with respect to the plane composed of both the optical axis and the common axis. Each light assembly segment includes a series of alternating linear  20  and revolved parabolic  18  segments but are now joined in opposition and share the common axis. Additionally, the light from the LEDs is aimed along the axes of the parabolas and not perpendicular to parabolic axes and may further be directed by an optical element  2021  as previously described. 
     While the invention has been specifically described in connection with certain specific embodiments thereof, it is to be understood that this is by way of illustration and not of limitation. Reasonable variation and modification are possible within the scope of the forgoing disclosure and drawings without departing from the spirit of the invention which is defined in the appended claims.