Patent Publication Number: US-2012039077-A1

Title: Area lighting devices and methods

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of priority of U.S. Provisional Application No. 61/372,781, entitled “Area Lighting Devices and Methods” and filed Aug. 11, 2010, which is hereby incorporated by reference in its entirety. 
    
    
     FIELD 
     The present invention generally relates to optics and lighting systems, and more particularly to optics and lighting systems for generating an asymmetric lighting pattern, including devices, systems and methods for generating an asymmetric lighting pattern from one or more light sources. 
     BACKGROUND 
     Optics for high-power light sources, such as light emitting diodes, can have a wide variety of configurations. In many cases, a particular configuration can be characterized by the illumination pattern it produces, by the coherence, intensity, efficiency and uniformity of the light it projects, and/or in other ways. The application for which the lens and/or lighting system is designed may demand a high level of performance in many of these areas. 
     Many applications call for the lens and/or lighting system to direct the light to a target area, while reducing the transmission of stray light beyond the boundaries of a desired illumination pattern. Further, some applications require that light from a light source be manipulated to produce an asymmetric illumination pattern. By way of example, street lamps should be designed to illuminate preferentially the street rather than adjacent areas, even when the light source(s) of the street lamp is not positioned directly over the street. To date, street lighting systems have typically been tilted relative to the plane of the street to direct the light accordingly. However, the uniformity and efficiency of such systems can be limited and their illumination characteristics are typically sub-par. 
     Accordingly, there is a need for improved area lighting devices, systems and methods, and particularly a need for such lighting devices, systems and methods that can be utilized in street lighting applications. 
     SUMMARY 
     In one aspect, the present invention provides an optic that comprises an input surface adapted for receiving light from a light source, an output surface having a central portion and a pair of side portions, and a pair of reflective sidewalls. The central portion of the output surface has a surface profile and is positioned relative to said input surface such that it refracts light incident thereon via the input surface asymmetrically out of the optic. Further, each of the reflective sidewalls is adapted to reflect light incident thereon via the input surface to a respective one of said side portions of the output surface for exiting the optic. 
     In some embodiments, the input surface exhibits rotational symmetry about an axis (herein referred to as “central axis”). Further, in some embodiments, the optic can exhibit a plane of mirror symmetry. In some cases, the central axis associated with the input surface can lie in the optic&#39;s plane of symmetry. 
     In some embodiments, the optic is configured such that the light rays that exit the central portion of the output surface in the optic&#39;s plane of symmetry diverge asymmetrically relative to the central axis (i.e., the axis of rotational symmetry of the input surface). By way of example, the light rays exiting the optic through the central portion of the output surface in the plane of symmetry can exhibit a maximum divergence angle relative to the central axis on one side of the central axis that is different from a respective maximum divergence angle relative to the central axis on an opposed side of the central axis. 
     In some embodiments, the optic is configured such that a maximum divergence angle relative to the central axis of light rays that exit the central portion of the output surface in the plane of symmetry on one side of the central axis is equal to or greater than a maximum divergence angle of light rays that exit the optic in the plane of symmetry through a side portion of the output surface that is located on an opposed side of the central axis. 
     In some embodiments, the optic is configured such that a maximum divergence angle of light rays exiting the optic in the plane of symmetry relative to the central axis is less than a respective maximum divergence angle of the light rays exiting the optic in another plane (“second plane”) that contains the central axis and is perpendicular to the plane of symmetry. In some embodiments, the optic can be asymmetric relative to such a second plane (i.e., the optic lacks minor symmetry about the second plane). 
     In some embodiments, the optic is configured such that the light rays that exit the central portion of the output surface in the second plane diverge symmetrically relative to the central axis. By way of example, in one embodiment, the light rays exiting the central portion of the output surface in the second plane exhibit a maximum divergence angle of about 70 degrees relative to the central axis on each side of the central axis. 
     In another aspect, in the above optic, the pair of reflective sidewalls comprises first and second sidewalls, where the angular divergence of light rays (i.e., the angle between two rays representing the boundaries of the bundle of rays) received by the first sidewall from the input surface in the plane of symmetry is less than the angular divergence of light received by the second sidewall from the input surface in the plane of symmetry. 
     In some embodiments, a minimum distance between the first sidewall and the central axis in the optic&#39;s plane of symmetry is greater than a minimum distance between the second sidewall and the central axis in that plane of symmetry. 
     In some embodiments, the side portions of the output surface intersect with the central portion of the output surface at an intersection point in the plane of symmetry. In one embodiment, the minimum distance between the intersection point and the central axis on one side of the central axis than on the other side of the central axis. 
     In some embodiments, the central portion of the output surface is positioned relative to the input surface such that a majority of light rays in the plane of symmetry incident on the central portion of the output surface are refracted toward one side of the central axis relative to the other side. 
     In some embodiments, the central portion of the output surface is positioned relative to the input surface such that light rays traversing the optic in the plane of symmetry exit the central portion of the output surface at an angle in a range of about 0 degree to about 60 degrees relative to the central axis on a first side of the central axis and at an angle in a range of about 0 degree to about 20 degrees relative to the central axis on a second side of the central axis. 
     In some embodiments, the side portion of the output surface associated with the sidewall on said first side of the central axis (“first side output surface”) is configured such that light rays traversing the optic in the plane of symmetry exit said first side output surface and exhibit an angular divergence (i.e., the angle between two rays representing the two boundaries of the bundle of rays) of about 20 degrees. 
     In some embodiments, the side portion of the output surface associated with the sidewall on said second side of the central axis (“second side output surface”) is configured such that light rays traversing the optic in the plane of symmetry exit said second side output and exhibit an angular divergence of about 60 degrees. 
     While in some embodiments, the sidewalls of the optic are configured to reflect light incident thereon via total internal reflection, in other embodiments, the sidewalls are configured to reflect light incident thereon via specular reflection. Such specular reflection of the incident light can be achieved, for example, via metallization of the sidewall surface, e.g., via a thin metal coating. 
     The output surface of the optic including its central and side portions can be implemented in a variety of ways. By way of example, in some embodiments the central portion of the output surface is formed as two lobes each of which presents a concave surface to the light incident thereon via the input surface. In some embodiments, the side portions of the output surface are substantially planar surfaces. In some implementations, such planar side portions of the output surface can be tilted relative to the central axis of the input surface. The tilt of one side portion relative to the central axis can be different than the tilt of the other side portion relative to the central axis. In some embodiments, one of the side portions of the output surface forms an angle in the optic&#39;s plane of symmetry in a range of about 50 degrees to about 70 degrees relative to the central axis and the other side portion forms an angle in a range of about 10 degrees to about 30 degrees in the optic&#39;s plane of symmetry relative to the central axis. By way of example, in one embodiment, one of the side portions of the output surface forms an angle in the plane of symmetry of about 60 degrees relative to the central axis and the other side portion forms an angle of about 20 degrees in the plane of symmetry relative to the central axis. 
     In some embodiments, the optic comprises a unitary structure. In other words, the optic is formed as an undivided whole unit. 
     The optic can be formed of a variety of materials, which are preferably transparent to visible radiation. By way of example, in some embodiments, the optic can be formed at least partially of one of polymethyl methacrylate (PMMA), glass, polycarbonate, and cyclic olefin polymer. 
     In another aspect, an optical system is provided that comprises a light source, and an optic having an inferior surface, a superior surface, and a pair of sidewalls extending therebetween, for example, so as to form a central lens portion and two side lens portions. The inferior surface comprises an input portion for receiving light from the light source, where the input portion forms a cavity for at least partially housing the light source. The superior surface in turn comprises a central portion and two side portions, where the central portion of the superior surface is adapted to refract at least a portion of the light received through the input portion out of the optic so as to generate an asymmetric illumination area on a target surface, and the sidewalls are adapted to reflect at least a portion of the light received through the input portion to a respective side portion of the superior surface such that each side portion of the superior surface refracts light incident thereon out of the optic to said asymmetric illumination area. 
     In some embodiments, the sidewalls are curved so as to present a convex or a concave surface to the light incident thereon via the inferior surface. Further, in some embodiments, the side portions of the superior surface are substantially planar, though in other embodiments they can be curved. In some embodiments, the side portions of the superior surface have different surface areas. 
     In some embodiments, the light source emits light that can be characterized as having a central propagation axis. For example, the light emitted by the source can exhibit rotational symmetry about such a central propagation axis (the light intensity in a plane perpendicular to the central propagation axis can be rotationally symmetric about the central propagation axis). In some embodiments, the optic can include a plane of symmetry (i.e., a plane through which the optic exhibits minor symmetry) that contains the central propagation axis. In other words, the central propagation axis can lie in the plane of symmetry. 
     In some embodiments, the input surface of the lens exhibits rotational symmetry about an axis (“central axis”). In some cases, the central propagation axis of the light rays emitted by the source and the central axis of the optic are substantially aligned. 
     In some embodiments, the optic is positioned relative to the light source such that a majority of light rays exiting the optic in the plane of symmetry are preferentially refracted away from the central propagation axis and toward one side of the central propagation axis (and/or the central axis) relative to the other side. 
     In some embodiments, the side portions of the superior surface are substantially planar. In such cases, an angle of each side portion relative to the central propagation axis can be defined as the angle between a line segment representing the intersection of the side portion with the optic&#39;s plane of symmetry and the central propagation axis. In some such embodiments, the side portions have different angles relative to the central propagation axis. 
     In some embodiments, a minimum distance between one side portion of the superior surface and the central propagation axis is greater than a minimum distance between the other side portion of the superior surface and the central propagation axis. 
     In some embodiments, the optic is configured such that light rays that traverse the optic in the plane of symmetry and exit the optic through the central portion diverge asymmetrically relative to said central propagation axis. 
     In some embodiments, the optic is configured such that light rays that traverse the optic in the plane of symmetry and exit the optic through the central portion of the superior surface exhibit a maximum divergence angle on one side of the central propagation axis that is different from a maximum divergence angle on an opposed side of the central propagation axis. 
     In some embodiments, the optic is configured such that a maximum divergence angle relative to the central propagation axis of light rays exiting the optic through the central portion of the superior surface in the plane of symmetry on one side of the central propagation axis is equal to or greater than an angular divergence of light rays exiting the optic through a side portion of the superior surface that is located on an opposed side of the central propagation axis. 
     In some embodiments, the optic is configured such that the light rays that traverse the optic in the plane of symmetry and exit the optic through the superior surface exhibit a maximum divergence angle that is less than a maximum divergence angle exhibited by the light rays that traverse the optic in another plane that is perpendicular to the plane of symmetry and contains the central propagation axis (“second plane”) and exit the optic through the superior surface. 
     In some embodiments, the light rays that traverse the optic in said second plane to exit the optic through the superior surface diverge symmetrically relative to the central propagation axis. 
     In some embodiments, the optic is asymmetric relative to the second plane, i.e., it does not exhibit minor symmetry about the second plane. 
     In some embodiments, the input surface exhibits rotational symmetry about a central axis. In some embodiments, the central axis and the central propagation axis are aligned. In some embodiments, the minimum distance between one side portion of the superior surface and the central axis is greater than a minimum distance between the other side portion of the superior surface and the central axis. 
     In another aspect, a lighting system is disclosed that comprises a pole disposed adjacent to a target surface, and at least one lighting module mounted on said pole, where the lighting module comprises a light source and an optic for directing light from said source to said target surface. The optic comprises a central refractive portion and a pair of side portions, where the central refractive portion has a cavity for at least partially receiving said light source and for coupling light from said light source into the optic. The central refractive portion further includes an output surface adapted to refract at least a portion of light received through the input surface out of the optic so as to generate an asymmetric illumination area on said target surface. Each side portion is adapted to redirect at least portion of the light received through the input surface out of the optic—via reflection and refraction—to said asymmetric lighting area. 
     In some embodiments, the lighting module is mounted such that one of said side portions (“proximal side portion”) is disposed proximal to said pole and the other side portion (“distal side portion”) is disposed distal to the pole. 
     In some embodiments, the light emitted by the light source is characterized by a central propagation axis. In some implementations, the lighting module is mounted on the pole such that the central propagation axis is substantially parallel to a central longitudinal axis of the pole. 
     In some embodiments, in the above lighting module, the optic exhibits a plane of symmetry and the central propagation axis lies in said plane of symmetry. 
     In some embodiments, the optic is configured such that the light rays exiting the output surface of said central refractive portion in said plane of symmetry diverge asymmetrically relative to said central propagation axis. 
     In some embodiments, the optic is configured such that light rays exiting said output surface of the central refractive portion in said plane of symmetry exhibit a maximum divergence angle relative to the central axis on a distal side of said central propagation axis that is greater than a maximum divergence angle relative to the central axis on a proximal side of said central propagation axis. 
     In some embodiments, the proximal side portion can comprise a proximal sidewall and a proximal output surface and the distal side portion can comprise a distal sidewall and a distal output surface. The proximal sidewall can be configured such that substantially all light received from the input surface at the proximal sidewall is reflected to exit the optic through the proximal output surface, and the distal sidewall is configured such that substantially all light received from the input surface at the distal sidewall is reflected to exit the optic through the distal output surface. 
     In some embodiments, a maximum divergence angle relative to the central axis of light rays exiting said output surface of the central refractive portion in the plane of symmetry on said distal side of the central propagation axis is equal to or greater than an angular divergence of light rays exiting the proximal output surface in said plane of symmetry. 
     In some embodiments, a maximum divergence angle relative to the central axis of light rays exiting the output surface of the central refractive portion in said plane of symmetry on said proximal side of the central propagation axis is equal to or greater than an angular divergence of light rays exiting the distal output surface in said plane of symmetry. 
     In some embodiments, the optic is positioned relative to the light source such that in the plane of symmetry, a majority of light received through the input surface exits the output surface distal to the central propagation axis. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A further understanding of various aspects of the application can be obtained by reference to the following detailed description in conjunction with the associated drawings, in which: 
         FIG. 1  depicts a perspective view of one embodiment of a lighting system according to the teachings of the invention having an optic and a light source; 
         FIG. 2  depicts another perspective view of the system shown in  FIG. 1 ; 
         FIG. 3  shows a plan view of the system shown in  FIG. 1 ; 
         FIG. 4  shows an another plan view of the system shown in  FIG. 1 ; 
         FIG. 5  depicts a plane of symmetry of the optic of the system shown in  FIG. 1  as well as a plane perpendicular to the plane of symmetry; 
         FIG. 6  schematically depicts a partial cross-sectional view of the system shown in  FIG. 1 , the cross-section being in the plane of symmetry of the optic with exemplary ray traces representing light emitted from the light source and traversing through the optic; 
         FIG. 7  schematically depicts another partial cross-sectional view of the system shown in  FIG. 1 , in a plane perpendicular to the plane of symmetry and containing the central propagation axis of the source, with exemplary ray traces representing light emitted from the light source and traversing through the optic; 
         FIG. 8  schematically depicts a partial cross-sectional view in the plane of symmetry of an exemplary embodiment of an optic according to the teachings of the invention; 
         FIG. 9  schematically depicts boundary rays of light exiting the optic of  FIG. 8  in the optic&#39;s plane of symmetry; 
         FIG. 10  depicts one embodiment of a lighting system according to the teachings of the invention for illuminating a target surface, such as a street. 
     
    
    
     DETAILED DESCRIPTION 
     The present application discloses, among other things, optics and lighting devices, systems, and associated methods for delivering light asymmetrically onto a target surface so as to create a desired illumination pattern. Typically, the optics and lighting systems described herein include an optic that receives light from one or more light sources and redirects the light in a patterned or other controlled manner. In many cases, a central lens portion can generate a desired asymmetric illumination pattern while peripheral lens portions redirect light received from the light source to portions of the asymmetric illumination pattern generated by the central lens portion. In many embodiments, the central lens portion redirects light received from a source only via refraction, whereas the peripheral lens portions redirect the light received from the source via a combination of reflection and refraction. 
     In some embodiments, such redirection of the source light by the peripheral lens portions can improve the uniformity of light intensity throughout the pattern and/or prevent light from being directed to undesirable directions (e.g., outside of the asymmetric pattern generated by the central lens portion). In many cases, such an optic can reduce losses associated with prior art lighting systems in which a substantial amount of light generated by the lighting source may fail to illuminate a desired area on a target surface, or indeed, miss the target surface altogether. Further, in some embodiments, multiple optics and their associated light sources (i.e., lighting modules) can be used together to generate an illumination pattern on a target surface. By way of example, the modules can be positioned relative to one another such that the pattern generated by each individual module at least partially overlaps (and in some cases substantially coincides) with the illumination pattern(s) generated by one or more of the other modules to form a desired overall illumination pattern. 
     The devices, systems, and methods disclosed herein can be used with a wide variety of light sources, including light emitting diodes and incandescent bulbs, or other coherent or non-coherent light sources. Such devices, systems, and methods incorporating the teachings herein can have a wide range of applications, including, for example, street lighting, spot lighting, customizable/adjustable lighting systems, household lighting, flashlights, wearable headlamps or other body-mounted lighting, among others. 
     Throughout this application, the term “e.g.” will be used as an abbreviation of the non-limiting term “for example.” It should be understood that regardless of whether explicitly stated or not, all characteristics of the optics described herein are by way of example only, and not necessarily requirements. All figures merely depict exemplary embodiments of the invention. 
     Directional terms such as “proximal,” “superior,” and “anterior” will be used to describe various portions of the optics. These directional terms are merely used as a naming convention to describe the relationship of various parts of the optic relative to one another. These terms do not, however, necessarily indicate a particular orientation or disposition of the optics or systems in use. For example, though an output surface of a lens may be described as “superior,” the system can be oriented such that light from the light source exits the “superior” surface of the lens in a downward direction (e.g., towards the ground). 
     Further, in some embodiments discussed below, various features of an optic according to the teachings of the invention are discussed with reference to the way the optic redirects light rays incident thereon. For this discussion, it is generally assumed that the light rays are emitted from a putative point source and illuminate an input surface of the optic substantially uniformly. Such light rays can be simulated by ray-tracing software, or they can be provided by a physical light source, such as an LED. It should be understood that the optics and the lighting systems according to the teachings of the invention can be utilized with and can incorporate a variety of light sources. In some cases, such a light source can have a size small enough relative to the size of the optic to be considered as a point source, while in other cases the size of the light source can be comparable to that of the optic. Further, while in some cases the light from such a source illuminates the input surface of the optic substantially uniformly, in other cases the light rays can provide a non-uniform illumination of the optic&#39;s input surface. 
     Turning to  FIGS. 1 and 2 , one exemplary embodiment of a lighting system or lighting module  100  can include an optic  120  and a light source  110 . In this embodiment, the optic  120  includes side portions  140   a,b  and a central refractive portion  122  disposed therebetween. The central refractive portion  122  includes a superior surface  124  and an inferior surface  126 , as best shown in  FIG. 2 . Each of the side portions  140   a,b , which can be unitary with the central refractive portion  122 , includes a reflective sidewall  142   a,b  and a side output surface  144   a,b  associated therewith. The side portions  140   a,b  can be bounded by lateral surfaces  146 . 
     The inferior surface  126  of the central refractive portion  122  is generally configured to couple light from a light source into the optic  120  through at least a portion thereof (herein also referred to as “input surface”) and can have a variety of configurations. In the embodiment depicted in  FIGS. 1-4 , the input surface  128  forms a recess or cavity in the inferior surface  126 , which can house at least partially one or more light source(s). Although any number of light sources can be employed,  FIG. 1  shows a single light source  110 , such as a light emitting diode, that is disposed at least partially within the cavity of the optic  120 . In some embodiments, however, the light source  110  can be disposed outside of the cavity such that the input portion only receives the light from the light source, rather than the light source  110  itself. Regardless, the input surface  128  receives light from the light source  110  and is configured to couple the light from the light source  110  into the optic  120 , for example, via refraction at the input surface  128 . 
     The term “refraction” is used herein consistent with it ordinary meaning in the art and refers to the passage of light rays from one medium having one index of refraction (e.g., air outside the optic  120 ) to another medium having a different index of refraction (e.g., the material forming the optic  120 ). The refraction of light rays at the interface of two such media can lead to deflection of the rays (i.e., for light rays incident on the interface in non-orthogonal directions). As one skilled in the art will understand, some light from the light source  110  can enter the optic  120  without redirection, for example, if they strike the input surface  128  in a direction normal to the surface. 
     The input surface  128  can have a variety of configurations to couple light from the light source  110  into the optic  120 . By way of non-limiting example, the input surface  128  can present a substantially concave surface to the light rays emitted by the light source  110  such that the refraction of the light rays at the input surface  128  for entry into the optic can cause their divergence. Alternatively, for example, the input surface  128  can present a convex surface, or even planar surface to the light source  110  for coupling the light into the optic  120 . 
     As shown in  FIGS. 1-4 , in this embodiment the input surface  128  is in the form of a hemispherical surface that is rotationally symmetric about a central axis  132 . In other embodiments, the input surface may lack an axis of rotational symmetry. The light source  110 , which as shown emits light characterized by a central propagation axis  112 , is positioned within the cavity defined by the hemispherical surface such that the central propagation axis  112  and the central axis  132  of the input surface  128  are substantially aligned. In some embodiments, however, various portions of the input surface  128  can be irregular, or the light source  110  can be positioned relative to the input surface  128  such that light from the light source  110  is refracted asymmetrically into the optic  120  by the input surface  128 . In some embodiments, for example, the input surface  128  can be configured to redirect light within the optic  120  with an asymmetric distribution such that the ultimate asymmetric distribution of light exiting the optic  120  can be through the combined effect of the input and output surfaces. 
     The superior surface  124  of the central refractive portion  122  can have a variety of configurations to refract light incident thereon out of the optic asymmetrically, e.g., to generate an asymmetric illumination pattern on a target surface. That is, the central refractive portion  122  can refract light rays incident thereon out of the optic such that the exiting light rays lack an axis of rotational symmetry. For example, in this embodiment, the light rays exiting the optic  120  through the central refractive portion  122  do not exhibit rotational symmetry relative to the central axis  132 . In other words, an illumination pattern (characterized by an intensity distribution of light) generated by the light rays exiting the optic through the central refractive portion  122  on a target surface perpendicular to the central axis lacks rotational symmetry. For example, such an illumination pattern can be substantially rectangular, elliptical, square, hexagonal, or in fact, can exhibit an irregular shape. 
     As shown in  FIGS. 1-4 , in this embodiment, the superior surface  124  is a continuously curved surface that extends between the side output surfaces  144   a,b . Though the superior surface  124  generally presents a concave surface to light transmitted thereto from the input surface  128 , various portions of the superior surface  124  can include features that alter the propagation of light therethrough in different ways. By way of example, the superior surface  124  shown in  FIGS. 1-4  includes a trough  134  formed in the superior surface  124  near its intersection with one of the side output surfaces  144   b . Thus, whereas most of the superior surface  124  acts to diverge light incident thereon from the input surface (i.e., the surface has a negative optical power), at least a portion of the superior surface  124  is shaped as the trough  134  that converges the light exiting therethrough. In this embodiment, the superior surface  124  is shaped and positioned relative to the input surface  128  such that the light incident on the superior surface  124  can be refracted asymmetrically out of the optic  120 . In this embodiment, the superior surface  124  lacks rotational symmetry, but includes one plane of minor symmetry. In other embodiments, the superior surface  124  can have an axis of rotational symmetry but can be positioned relative to the input surface (e.g., with an offset between the central axis of the input surface and the axis of rotational symmetry of the superior surface) so as to refract light received from the input surface asymmetrically out of the optic. 
     The side portions  140   a,b  can also have a variety of configurations, but generally, are configured to redirect light rays received from the input surface such that most of the rays exiting the optic through the side portions intersect the light rays exiting the optic through the central refractive portion. For example, in this embodiment, the side portions  140   a,b  are configured to redirect light received from the input surface such that it exits the optic  120  to portions of an asymmetric illumination pattern generated by the superior surface  124  of the central refractive portion  122  on a target surface. In some embodiments, some light rays (e.g., some stray rays) exiting the superior surface  124  near the side output surfaces  144   a,b  can impinge on the side output surfaces  144   a,b  and be reflected thereby or re-enter the optic  120  and be reflected by the sidewalls  142   a,b  (e.g., be reflected back to the side output surfaces  144   a,b  through which they would again exit the optic or be reflected towards another portion of the optic  120 ) or transmitted therethrough (e.g., if the angle is less than the critical angle of a TIR surface of the sidewalls  142   a,b ). 
     As best shown in the view of  FIG. 4 , in this embodiment, each of the side portions  140   a,b  includes a curved reflective sidewall  142   a,b  and a planar side output surface  144   a,b . As will be discussed in detail below, the size, curvature, and orientation of the sidewalls  142   a,b  and side output surfaces  144   a,b  relative to the input surface can be configured to controllably redirect the light out of the optic  120 . For example, the sidewalls  142   a,b  can be curved so as to present a concave surface to the light incident thereon via the input surface  128 . In other embodiments, the sidewalls  142   a,b  or a portion thereof can also present a convex or planar surface to the incident light. While in this embodiment the side output surfaces  144   a,b  are planar, in other embodiments, they can be curved, e.g., they can present concave or convex surfaces to incident light rays. 
     The reflective sidewalls  142   a,b  can be configured to reflect light via a wide range of mechanisms, for example, via total internal reflection (TIR) or via specular reflection, which can be achieved. e.g., by metalizing (e.g., forming a metallic coating) on the sidewalls. Further, in some embodiments, one sidewall can employ one mechanism for reflecting the light incident thereon (e.g., TIR) and the other sidewall can employ a different mechanism for reflecting the light incident thereon (e.g., specular reflection). 
     As is known in the art, total internal reflection can occur at an interface between two media having different indices of refraction when the light traversing the medium having the larger index is incident on the interface at an angle relative to a normal to the interface that exceeds a critical angle, which can be defined by the following relation: 
     
       
         
           
             
               θ 
               crit 
             
             = 
             
               arcsin 
                
               
                 
                   n 
                   2 
                 
                 
                   n 
                   1 
                 
               
             
           
         
       
     
     where n 1  is the refractive index of the medium having the larger index and n 2  is the refractive index of the medium having the lower refractive index. 
     The lateral surfaces  146  can also have a variety of configurations. For example, light incident thereon can exit the optic  120  through the lateral surface (e.g. via refraction). In some embodiments, the lateral surfaces  146  can be metalized so as to redirect the light back into the optic  120  to thereby increase the efficiency of the lens. In some embodiments, the optic  120  can be shaped to minimize the incidence of light on the lateral surfaces. 
     In some embodiments, the lighting system  100 , and indeed the optic  120  itself, can exhibit at least one plane of symmetry. For example, with reference now to  FIG. 5 , the optic  120  includes an input surface  128  rotationally symmetric about a central axis  132 , as described above. Further, in this embodiment, the optic  120  exhibits minor symmetry about a plane  160  that contains the central axis  132 . In other words, the putative plane  160  bisects the optic into two symmetrical portions. Additionally, in this exemplary embodiment, the central axis  132  and the central propagation axis  112  are aligned such that the plane of symmetry  160  also contains the central propagation axis  112 . In addition, in this embodiment, the central refractive portion  122  also exhibits mirror symmetry about the plane  160 . A putative second plane  162 , also shown in  FIG. 5 , is perpendicular to the plane of symmetry  160  and includes the central axis  132 . 
     The propagation of light through an optic will be discussed in further detail below, but generally, the light that enters the optic  120  through the input surface  128  (or at least a portion of the light) is conveyed through the optic  120  to each of the superior surface  124  and the sidewalls  142   a,b . Light incident on the superior surface  124  of the central refractive portion  122  exits the optic  120  (e.g., via refraction) through the superior surface  124  and propagates, e.g., towards a target surface. As discussed in more detail below, the light can exit the optic through the central refractive portion  122  asymmetrically. The light rays from the light source  110  that enter the optic  120  through the input surface  128  at angles such that they are transmitted to the sidewalls  142   a,b  are thereby reflected by each of the sidewalls  142   a,b , in this embodiment via total internal reflection, towards a respective one of the side output surfaces  144   a,b . The reflected rays then exit the optic  120  through the output surfaces  144   a,b  of the side portions  140   a,b  (e.g., via refraction at those surfaces) and propagate, e.g., towards a target surface. 
       FIG. 6  depicts an exemplary ray trace in the plane of symmetry  160  of the optic  120 , illustrating light rays originating at light source  110  that impinge on the input surface  128  of the inferior portion  126 . Some of the light rays are refracted at the input surface  128  so as to propagate to the superior surface  124  of the central refractive portion  122 . At the superior surface  124 , these rays are refracted to exit the optic  120 . In this embodiment, the light rays exiting the optic in the plane of symmetry  160  through the superior surface  124  of the central refractive portion  122  exhibit asymmetry relative to central axis  132 , which in this embodiment is substantially aligned with the central propagation axis  112 . That is, the superior surface  124  can redirect light rays out of the optic  120  such that the illumination pattern (characterized by an intensity distribution of light) generated by the light rays exiting the superior surface  124  on a target surface perpendicular to the central axis  132  lacks rotational symmetry. By way of non-limiting example, more light rays exiting the optic  112  in the plane of symmetry  160  are directed to one side of the central axis  132  than to the other. 
     With continued reference to  FIG. 6 , the light rays exit the superior surface  124  of the central refractive portion  122  in the plane of symmetry  160  with a maximum divergence angle of about 60 degrees relative to the central propagation axis  112  on one side (i.e., to the left in  FIG. 6 ) of the central propagation axis  112  and a maximum divergence angle of about 20 degrees on the other side (i.e., to the right in  FIG. 6 ). 
     Some of the light rays emitted by the light source  110  that are incident on the input surface  128  are refracted at that surface so as to propagate through the optic  120  to the reflective sidewall  142   a  on one side (i.e., to the left in  FIG. 6 ) of the central propagation axis  112 . The reflective sidewall  142   a  reflects these rays to the side output surface  144   a . At the side output surface  144   a , these rays are refracted to exit the optic  120 . As depicted in  FIG. 6 , a portion of those light rays exit the side output surface  144   a  in the plane of symmetry toward the central axis  132 , converge to a point, and continue to propagate therefrom at an angular divergence of about 20 degrees. 
     Some of the light rays emitted by the light source that are incident on the input surface  128  are refracted at that surface so as to propagate through the optic  120  to the reflective sidewall  142   b  on the other side (i.e., to the right in  FIG. 6B ) of the central propagation axis  112 . The reflective sidewall  142   b  reflects these rays to the side output surface  144   b . At the side output surface  144   b , these rays are refracted to exit the optic  120 . As depicted in  FIG. 6 , a portion of those rays exit the side output surface  144   b  in the plane of symmetry toward the central axis  132 , converge to a point, and continue to propagate therefrom at an angular divergence of about 50 degrees. 
       FIG. 7  illustrates an exemplary ray trace in a putative second plane  162  of the optic  120  that is perpendicular to the symmetry plane  160  and includes the central axis  132 . The illustrated light rays originate at light source  110  and impinge on the input surface  128  of the inferior portion  126  and are refracted at the input surface  128  to enter the optic  120  and propagate to the superior surface  124  of the central refractive portion  122 . At the superior surface  124 , these rays are refracted to exit the optic  120 . As depicted in  FIG. 7 , the light rays exit the superior surface  124  of the central refractive portion  122  in the second plane  162  symmetrically relative to the central axis  132 . In this embodiment, the maximum divergence angle of light from the central refractive portion in the putative second plane is about 70 degrees relative to the central axis  132 . 
     Turning to  FIGS. 8 and 9 , another exemplary implementation of the optic  120  (herein referred to as optic  820 ) is shown. In this implementation, the optic  820  includes an output surface having two side portions  844   a,b  and a central portion  824 . Each of the side portions  840   a,b  is associated with a reflective sidewall  842   a,b . The optic  820  also includes an inferior surface  826  having an input surface  828 , which forms a cavity for receiving light from a light source (not shown). As shown, the input surface  828  is in the form of a hemispherical surface that is rotationally symmetric about a central axis  832 . 
     Further, in this embodiment, the optic  820  exhibits minor symmetry about a plane  860  that contains the central axis  832 . In other words, the putative plane  860  bisects the optic into two symmetrical portions. Additionally, in this exemplary embodiment, a putative second plane (not shown) of the optic  820  can be defined, the second plane being perpendicular to the plane of symmetry  860  and also including the central axis  832 . 
       FIG. 8  schematically depicts a cross-sectional view of the optic  820  in the plane of symmetry  860 . As discussed above with reference to  FIGS. 1-4 , the side portions  844   a,b  are planar though in other embodiments, they can present concave or convex surfaces to incident light rays. Thus, in this cross-sectional view, the planar side portions  844   a,b  are shown as line segments. In this embodiment, the line segments  844   a  and  844   b  form different angles α and β relative to the central axis  832 . More specifically, in this embodiment, the angle α is about 60 degrees and the angle β is about 20 degrees. More generally, one of the angles (e.g., a) can be in a range of about 50 degrees to about 70 degrees and the other angle (e.g., α) can be in a range of about 10 degrees to about 30 degrees, though the configuration of the side output surfaces  844   a,b  and their arrangement relative to the input surface  828  can be modified to achieve a desired output light distribution, as otherwise discussed herein. 
     With continued reference to  FIG. 8 , a minimum distance between each side portion  844   a,b  and the central axis  832  in the plane of symmetry  860  can be defined as the distance between the central axis  832  and the intersection point  848   a,b  of a respective line segment  844   a,b  with the central portion  824 , which distance can be characterized by the length of an orthogonal line segment that connects the intersection point  848   a,b  to the central axis  832  and is orthogonal to the central axis  832 . For example, in this embodiment, the minimum distance between the side portion  844   a  and the central axis  832 , defined by the length of the line segment L 1 , is less than the minimum distance between the side output surface  844   b  and the central axis  832 , defined by the length of the line segment L 2 . Referring now to  FIG. 9 , the dotted lines represent boundary conditions of light rays exiting the optic  820  through the central portion  824  and side portions  844   a,b , when emitted from a putative light source  810  and input into the optic at input surface  828 . While these conditions refer to a point light source which provides substantially uniform illumination at the input surface  828 , one of skill in the art will appreciate that such measures discussed below can be similarly used to approximate the boundary conditions of the optic  820  of a variety of light sources positioned at a variety of locations relative to the input surface  828 . 
     The boundary line  900  represents the angle of the side portion  844   b  relative to the putative point light source  810  (i.e., β), as discussed above in reference to  FIG. 8 . Light that enters and traverses the optic  820  at an angle slightly greater than β relative to the central axis  832  (i.e., slightly clockwise of boundary line  900 ), is reflected from the most superior portion of sidewall  842   b  to the side portion  844   b , and is thereby refracted to exit the optic  820  approximately along the boundary line  901 . As shown, the boundary line  901  forms an angle of about α* relative to the central axis  832 . 
     Light that enters and traverses the optic  820  at an angle slightly less than 90 degrees relative to the central axis  832  is reflected from the most inferior portion of sidewall  842   b  to the side portion  844   b , and is thereby refracted to exit the optic  820  approximately along the boundary line  902 , which as shown is approximately parallel to the central axis  832 . 
     The boundary line  901  therefore represents the maximum exit angle of light that is reflected from the sidewall  842   b , while the boundary line  902  represents the minimum exit angle of light that is reflected from the sidewall  842   b . Accordingly, light emitted by a putative point light source  810  at an angle of between about 90 degrees relative to the central axis  832  and about β exits the side portion  844   b  within the boundaries defined by boundary lines  901  and  902  (i.e., at an angle between about 0 degree and about α*). 
     Conversely, the boundary line  903  represents the angle of the side portion  844   a  relative to the putative point light source  810  (i.e., a), as discussed above in reference to  FIG. 8 . Light that enters and traverses the optic  820  at an angle slightly greater than α relative to the central axis  832  (i.e., slightly counterclockwise of boundary line  903 ), is reflected from the most superior portion of sidewall  842   a  to the side portion  844   a , and is thereby refracted to exit the optic  820  approximately along the boundary line  904 . As shown, the boundary line  904  forms an angle of about β* relative to the central axis  832 . 
     Light that enters and traverses the optic  820  at an angle slightly less than 90 degrees relative to the central axis  832  is reflected from the most inferior portion of sidewall  842   a  to the side portion  844   a , and is thereby refracted to exit the optic  820  approximately along the boundary line  905 , which as shown is approximately parallel to the central axis  832 . 
     The boundary line  904  therefore represents the maximum exit angle of light that is reflected from the sidewall  842   a  while the boundary line  905  represents the minimum exit angle of light that is reflected from the sidewall  842   a . Accordingly, light emitted by a putative point light source  810  at an angle of between about 90 degrees and about a relative to the central axis  832  exits the side portion  844   a  within the boundaries defined by boundary lines  904  and  905  (i.e., at an angle between about 0 degree and about β*). 
     On the other hand, light that enters the optic  820  at an angle slightly less than β relative to the central axis  832  (i.e., slightly counterclockwise of boundary line  900 ), is thereby refracted by the central portion  824  at an angle of about β relative to the central axis. On the other side of the central portion  824  (i.e. to the left in  FIG. 9 ), light that enters the optic  820  at an angle slightly less than α relative to the central axis  832  (i.e., slightly clockwise of boundary line  903 ), is thereby refracted by the central portion  824  at an angle of about a relative to the central axis. 
     In the exemplary embodiment depicted in  FIG. 9 , the side portions  844   a,b  are therefore configured to act as cutoffs by redirecting light received from the input surface into an illumination area generated by the light exiting the optic through the central portion  824 . In this manner, the side portions  844   a,b  prevent glare and increase the efficiency of the light source (e.g., by preventing light from being directed outside of the desired illumination area). By way of example, light emitted from the central surface  824  on one side of the central axis  832  (e.g., to the right in  FIG. 9 ) exhibits a maximum divergence angle relative to the central axis  832  of about β in the plane of symmetry, while the light exiting the side portion  844   a  on the opposed side exhibits an angular divergence of about α. In some embodiments, β* is equal to or less than β such that one edge of the illumination pattern generated by the optic  820  in the plane of symmetry is restricted by α (i.e., boundary line  904  will not intersect boundary line  900 ). Conversely, on the other side of the central axis  832  (e.g., to the left in  FIG. 9 ), light emitted from the central surface  824  exhibits a maximum divergence angle of about a relative to the central axis  832  in the plane of symmetry, while the light exiting the side portion  844   b  exhibits an angular divergence of about α*. In some embodiments, α* is equal to or less than α such that one edge of the illumination pattern generated by the optic  820  in the plane of symmetry is restricted by α (i.e., boundary line  901  will not intersect boundary line  903 ). In this manner, the light rays exiting the side portions  844   a,b  are confined within the illumination pattern generated by the central surface  824 . 
     As shown in  FIG. 9 , the sidewalls  842   a  and  842   b  are configured and positioned relative to the input surface  828  such that the angular divergence of the light rays received by the sidewall  842   b  via the input surface  828  is greater than the angular divergence of those light rays received by the sidewall  842   b  via the input surface  828 . By way of example, in this embodiment, the light rays entering the optic via the input surface  828  in the plane of symmetry  860  received by the sidewall  842   a  exhibit an angular divergence of about (90-α) degrees, which is less than the angular divergence of about (90-β) degrees of the light rays in the plane of symmetry  860  received by sidewall  842   b.    
     As noted above, the optics and lighting modules comprising the optic (e.g., optic  120 ) and a light source  110 , such as an LED, can be utilized in a variety of applications. By way of example,  FIG. 10  schematically depicts such an application in which the optic(s)  1020  and an LED  1010  are employed as a lighting module  1000  for illuminating a street surface. The lighting modules  1000  are mounted on a pole, which is disposed adjacent to a street, such that each individual lighting module  1000  directs light generated by the LED(s)  1010  onto a portion of the street surface so as to generate a substantially rectangular illumination area  1002  thereon (as shown by the dotted line). More specifically, in the depicted embodiment, a plurality of lighting modules  1000  are mounted on the pole such that the LED  1010  is mounted above the optic  1000  and its central output surface  1024  and the side output surfaces  1044   a,b  face downward. Further, each optic  1020  can be mounted on the pole such that the side portion  1040   a  is distal to the pole and the other side portion  1040   b  is proximal to the pole such that a plane of symmetry of the optic  1020  extends across the street while the plane perpendicular to the plane of symmetry and containing the central propagation axis runs along the length of the street. Any number of lighting modules  1000  can be used, and the modules  1000  can be disposed in a variety of patterns (e.g., in an array). For example, the lighting modules may be aligned side-by-side or such that their side portions  1040   a,b  are adjacent. The modules  1000  can also be positioned relative to one another such that the pattern  1002  generated by each individual module  1000  at least partially overlaps (and in some cases substantially coincides) with the illumination pattern(s) generated by one or more of the other modules to form a desired illumination pattern. 
     In the embodiment depicted in  FIG. 10 , in which the light sources  1010  emit light characterized by a central propagation axis, the modules  1000  can be mounted such that said central propagation axis is substantially parallel with a central longitudinal axis of the pole. Nonetheless, the modules  1000  can be effective to preferentially direct a majority of the light to the target surface, even if the module is not disposed directly over that surface. Indeed, the optics  1020  can be configured such that light rays exiting the central output surface  1024  diverge asymmetrically relative to the central propagation axis to generate an asymmetric illumination pattern on the target surface. That is, the optics  1020  can redirect light rays out of the optic  1020  such that the illumination pattern (characterized by an intensity distribution of light) generated by the light rays exiting the optic  1020  on a target surface perpendicular to the central axis lacks rotational symmetry. By way of example, the central output surface  1024  in the plane of symmetry can diverge light asymmetrically relative to the central propagation axis. In one embodiment, light rays exiting the central output surface  1024  in the plane of symmetry can exhibit a maximum divergence angle relative to the central propagation axis on a distal side of the central propagation axis that is greater than a maximum divergence angle relative to the central propagation axis on a proximal side of the central propagation axis. In this manner, light can preferentially be directed by the central output surface  1024  distally (i.e., toward the center of the street). 
     Accordingly, as discussed otherwise herein, each optic  1020  can redirect the light generated by the LED  1010  to produce an asymmetric illumination pattern  1002 . By way of example, the central refractive portion  1024  of each optic  1020  can output light incident thereon to generate the asymmetric lighting pattern  1002 . For example, an optic  1020  oriented such that the plane of symmetry extends across the street outputs light along the length of the street according to the maximum divergence angle relative to the central propagation axis of the light rays exiting the central output surface  1024  in the plane perpendicular to the plane of symmetry and containing the central propagation axis (e.g., as discussed above in reference to  FIG. 6 , light exiting optic  120  in the second plane  162  exits the optic  120  symmetrically about the central propagation axis  112 ). 
     On the other hand, the distribution across the width of the street (i.e., in the plane of symmetry and planes parallel thereto) can be restricted based on the configuration of the central portion and/or the angle of the side output surfaces  1044   a,b  relative to the light source  1010  and their position relative to the input surface  1028 . For example, in some embodiments, the optic  1020  can be configured such that a maximum divergence angle relative to the central propagation axis of light rays exiting the central output surface  1024  on the distal side of the central propagation axis is equal to or greater than an angular divergence of light rays exiting the proximal output surface  1044   b  in the plane of symmetry. Similarly, the optic  1020  can be configured such that a maximum divergence angle relative to the central propagation axis of light rays exiting the central output surface  1024  on the proximal side of the central propagation axis is equal to or greater than an angular divergence of light rays exiting the distal output surface  1044   a  in the plane of symmetry. In this manner, the distal end of the central output surface  1024  restricts the distal edge of the asymmetric illumination pattern  1002  while the proximal end of the central output surface  1024  (e.g., the portion near the proximal output surface  1044   b ) restricts the proximal edge of the asymmetric illumination pattern  1002 . In this manner, light can be preferentially directed away from the light pole such that a majority of the light is distributed on the target surface (e.g., the street). As discussed otherwise herein, the side portions  1040   a,b  can thereby act as cutoffs to prevent light from exiting the optic  1020  at undesirable angles, which could inefficiently illuminate the target surface or miss the target surface. The side portions  1040   a,b  can be effective to redistribute light from the input surfaces directed thereat to the asymmetric illumination pattern  1002  generated by the central output surface  1024 , thereby improving the efficiency of the street lighting system and increasing the intensity and in some cases the uniformity of the light throughout the pattern  1002 . 
     Further, the distal and proximal side portions  1040   a,b  and their respective components (e.g., the distal and proximal sidewalls  1042   a,b  and the distal and proximal output surfaces  1044   a,b ) can have the same or different shapes and or configurations. In the depicted embodiment, the distal side portion  1042   a  is generally smaller than that of the proximal side portion  1042   b . The size of the proximal side portion  1042   b  and the more acute angle of the side output surface  1044   b  relative to the central propagation axis enable directing less light toward the pole (and therefore towards a house adjacent the pole side of the street). Additionally, differences in the configurations of the side portions  1040   a,b  can be important to alter the light cut-off angle for various light distribution requirements. For example, the desired illumination pattern for a residential street may be different than for a major motorway. The side portions  1040   a,b  can be sized and configured to allow for balancing the efficiency and light control. By way of example, the proximal side portion  1044   b  can be configured to form a more acute angle with the central axis so as to provide less light towards the pole side of the central axis. Similarly, the distal side portion  1044   a  can be tilted at a more obtuse angle relative to the central axis to allow the optic  1020  to provide an illumination pattern with a greater width across the width of the street. 
     The present application also provides an exemplary method of designing a lens configured to produce an asymmetric illumination pattern on a target surface area. For ease of reference, the following description will use terminology similar to that used above in connection with  FIG. 1 , but this should not be construed to mean that the optic  120  shown in  FIG. 1  must be designed in accordance with the following principles or that  FIG. 1  represents a result of performing every part of this exemplary design process. The design of such a lens can involve the use of a computer aided-model for designing optics and/or simulating the light produced by such optics. In one exemplary approach, the design of a lens can be viewed as a series of design goals or parameters for each surface or lens element of the optic. 
     For example, in some embodiments, the central output surface  124  can be designed by starting with an initial surface profile and iteratively changing the profile (e.g., by changing one or more parameters) based on a ray-tracing simulation of an asymmetric pattern generated by each profile relative to light received from a previously defined input surface until a desired illumination profile is achieved. The input surface  128 , side portions  140   a,b  can then be designed to preferentially direct light to various portions of the asymmetric lighting pattern and/or so as to increase uniformity of the desired illumination pattern and reduce the occurrence of glare. By way of example, optics and lighting systems made in accordance with the principles described herein can in some cases produce an asymmetric illumination area having a substantially uniform light intensity throughout the illumination area. 
     Indeed, an optic  120  can be designed in light of the teachings herein to create a variety of illumination patterns. As will be appreciated by the person of skill in the art, the exemplary optics described can be modified such that the general components (e.g., the superior surface  124  of the central refractive portion  122 ) can be configured and arranged to generate a desired illumination pattern. For example, the optic  120  can be made of various lengths, widths, or depths, and the size and arrangement of the input surface  128 , central refractive portion  122 , and side portions  140   a,b  relative to one another can be selected to achieve a desired output light distribution. 
     Texture, micro-lenses, micro-prisms, micro-cylinders, or other light-controlling structures can be added to the output surface, or any portion thereof, to achieve desired optical effects, e.g., to improve the uniformity of the light. 
     Optics and lighting systems made in accordance with the principles described herein can, in some cases, provide a variety of advantages. For example, in some embodiments, the side portions can prevent light rays emitted by the sources from diverging beyond a desired angle relative to the central axis of the input surface or central propagation axis of the light source. In some embodiments, the optics can reduce or avoid glare and/or improve the efficiency in illuminating the target area, and/or improve the uniformity of light of the desired illumination area. 
     Optics and lighting systems made in accordance with the principles described herein can, in some cases, provide an efficiency of at least about 80%, where efficiency is measured as the ratio of total source light to total light exiting the optic, for example, to illuminate a target surface. In other embodiments, such an optic and/or lighting system can exhibit at least about 50% efficiency, at least about 60% efficiency, at least about 70% efficiency, or at least about 75% efficiency. 
     It should be noted that the foregoing discussion is not intended to necessarily describe optimal results that can be achieved or that need to be achieved by employing an optic or lighting system in accordance with the teachings of the invention, but merely to illustrate exemplary advantages that may be possible in certain applications. 
     Any of the foregoing optics (e.g., any of the lens bodies illustrated and/or described in connection with  FIGS. 1-10 ) can be formed as a unitary structure. For example, with reference to the optic of  FIG. 1 , though the central refractive portion  122  and side portions  140   a,b  are described as distinct portions of the optic  120 , these “portions” of the optic  120  can form a continuous, physically undivided structure (which in many embodiments is formed of substantially the same material composition throughout). In other embodiments, different portions of the optic can be assembled as separate units, e.g., via physical and/or optical coupling. 
     The optics described herein can be made of a variety of materials. By way of non-limiting example, any of the lenses or other optics described herein can be made of polymethyl methacrylate (PMMA), glass, polycarbonate, cyclic olefin copolymer and cyclic olefin polymer, or any other suitable material. 
     The optics described herein can be fabricated by utilizing a variety of different methods. By way of non-limiting example, the optic  120  can be formed by injection molding, by mechanically cutting an optic from a block of source material and/or polishing it, by forming a sheet of metal over a spinning mandrel, by pressing a sheet of metal between tooling die representing the final surface geometry including any local facet detail, and so on. In some embodiments, reflective surfaces can be created by a vacuum metallization process which deposits a reflective metallic (e.g., aluminum) coating, by using highly reflective metal substrates via spinning or forming processes. Faceting on reflective surfaces can be created by injection molding, by mechanically cutting a reflector or lens from a block of source material and/or polishing it, by pressing a sheet of metal between tooling die representing the final surface geometry including any local facet detail, and so on. 
     Any publications or patent applications referred to herein, as well the appended claims, are incorporated by reference herein and are considered to represent part of the disclosure and detailed description of this patent application. Moreover, it should be understood that the features illustrated or described in connection with any exemplary embodiment may be combined with the features of any other embodiments. Such modifications and variations are intended to be within the scope of the present patent application.