BACKGROUND 
       [0001]    Light emitting diode (LED) lighting systems are becoming more prevalent as replacements for traditional lighting systems. LEDs are an example of solid state lighting and have advantages over traditional lighting solutions such as incandescent and fluorescent lighting because they use less energy, are more durable, operate longer, can be combined in red-blue-green arrays that can be controlled to deliver virtually any color light, and contain no lead or mercury. 
         [0002]    In many applications, one or more LED dies (or chips) are mounted within an LED package or on an LED module, which may make up part of a lighting fixture which includes one or more power supplies to power the LEDs. Some lighting fixtures include multiple LED modules. A module or strip of a fixture includes a packaging material with metal leads (to the LED dies from outside circuits), a protective housing for the LED dies, a heat sink, or a combination of leads, housing and heat sink. 
         [0003]    An LED fixture may be made with a form factor that allows it to replace a standard threaded incandescent bulb, or any of various types of fluorescent lamps. LED fixtures and lamps often include some type of optical elements external to the LED modules themselves. Such optical elements may allow for localized mixing of colors, collimate light, and/or provide the minimum beam angle possible. 
         [0004]    Optical elements may include reflectors, lenses, or a combination of the two. Reflectors can be, for example, of the metallic or mirrored type, in which light reflects of opaque silvered surfaces. Reflectors may also be made of glass or plastic and function through the principle of total internal reflection (TIR) in which light reflects inside the optical element because it strikes an internal surface of the element at an angle which is equal to or greater than the critical angle relative to the normal vector. 
       SUMMARY 
       [0005]    Embodiments of the present invention provide an optical element, or “optic” that can enable a lighting system to achieve beam control. The optic combines TIR and other surfaces into one collimator. The optic collects light from substantially all angles of an LED&#39;s light output and collimates the light into a narrow beam angle. A lighting system according to example embodiments of the invention can include a single LED and optic, or can include a plurality of LEDs and optics. 
         [0006]    An optical element according to at least some embodiments of the invention includes an entry surface and an exit surface. A concentrator lens is disposed opposite the entry surface and the concentrator lens is recessed relative to the exit surface. The concentrator lens may be, as examples, a convex lens or a surface forming, or acting as, a convex lens, or a Fresnel lens. In example embodiments, a mounting feature adjacent to the entry surface spaces the entry surface and concentrator lens from an LED. An outer surface is disposed between the exit surface and the mounting feature. In example embodiments of the invention, the outer surface provides the TIR surface for the optic. 
         [0007]    In at least some embodiments, the mounting feature is sized so that the LED would be at a focal point of the concentrator lens and opposite the radial center of the entry surface relative to the concentrator lens. In some embodiments, the mounting feature has a thickness of between 0.5 mm and 1.0 mm. In some embodiments, the mounting feature has a thickness of about 0.75 mm. In some embodiments, the mounting feature is adapted to fit around a submount of an LED device package. In some embodiments, the mounting feature and the entry surface of the optic form an optic-device interface that conforms to the LED device package. In some embodiments, the outer, TIR surface of the optic is at least partially parabolic. In some embodiments, the entry surface has a radius between 1.5 mm and 2.0 mm. 
         [0008]    In some embodiments, the base of the recessed, concentrator lens is recessed from about 14 mm to about 18 mm relative to the exit surface, resulting in the exit surface having a flat, annular shape. Thus, a substantially cylindrical wall is formed between the flat, annular exit surface and the base of the concentrator lens. In at least some embodiments, the angle between the exit surface and the substantially cylindrical wall is greater than 90 degrees. In some embodiments of the invention, the angle is about 91 degrees and the base of the concentrator lens is recessed from about 15.5 mm to about 16.0 mm away from a flat, annular exit surface. The concentrator lens can take various forms. As examples the concentrator lens can be or include a convex refracting surface (acting as or being a convex lens) or a Fresnel lens. 
         [0009]    A lighting system making use of an optic according to embodiments of the present invention can include at least one LED, and an optical element placed next to an LED so that a center of the LED is at a focal point for the concentrator lens and the optical element receives light from the LED through the entry surface. An electrical connection is provided for the LED or for each of the LEDs if multiple LEDs and optics are used. It should be noted that the mounting feature is located so as not to detract from the luminous area of the optic and in example embodiments does not directly affect the light pattern, but rather, provides appropriate spacing for the other features of the optic. In some embodiments, the mounting feature forms a part of the optical element. In some embodiments, the mounting feature, which may also be referred to herein as a spacer, is fastened to the optical element. This fastening may be accomplished, as an example, through the use of an adhesive. The mounting feature may also be fastened to or rest on an adjacent structure, such as a structure inside a lighting system making use of the optic. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]      FIGS. 1-5  show various perspective views of an optical element according to example embodiments of the present invention. 
           [0011]      FIG. 6  presents a detailed, cross-sectional view of the optical element of  FIGS. 1-5 . 
           [0012]      FIG. 7  presents a detailed, cross-sectional view of a portion of an optical element according to additional embodiments of the invention. 
           [0013]      FIG. 8  is a close-up view of the entry surface and mounting feature area of an optic according to example embodiments of the invention. 
           [0014]      FIG. 9  shows a perspective view of an example lighting system making use of an optic like that illustrated in the foregoing figures. 
           [0015]      FIG. 10  shows a view of another example lighting system making use of the optic, according to embodiments of the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0016]    Embodiments of the present invention now will be described more fully hereinafter with reference to the accompanying drawings, in which embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout. 
         [0017]    It will be understood that, although the terms first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element could be termed a second element, and, similarly, a second element could be termed a first element, without departing from the scope of the present invention. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. 
         [0018]    It will be understood that when an element such as a layer, region or substrate is referred to as being “on” or extending “onto” another element, it can be directly on or extend directly onto the other element or intervening elements may also be present. In contrast, when an element is referred to as being “directly on” or extending “directly onto” another element, there are no intervening elements present. It will also be understood that when an element is referred to as being “connected” or “coupled” to another element, it can be directly connected or coupled to the other element or intervening elements may be present. In contrast, when an element is referred to as being “directly connected” or “directly coupled” to another element, there are no intervening elements present. 
         [0019]    Relative terms such as “below” or “above” or “upper” or “lower” or “horizontal” or “vertical” may be used herein to describe a relationship of one element, layer or region to another element, layer or region as illustrated in the figures. It will be understood that these terms are intended to encompass different orientations of the device in addition to the orientation depicted in the figures. 
         [0020]    The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” “comprising,” “includes” and/or “including” when used herein, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. 
         [0021]    Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms used herein should be interpreted as having a meaning that is consistent with their meaning in the context of this specification and the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein. 
         [0022]    Unless otherwise expressly stated, comparative, quantitative terms such as “less” and “greater”, are intended to encompass the concept of equality. As an example, “less” can mean not only “less” in the strictest mathematical sense, but also, “less than or equal to.” 
         [0023]    The terms “LED” and “LED device” as used herein may refer to any solid state light emitter. The terms “solid state light emitter” or “solid state emitter” may include a light emitting diode, laser diode, organic light emitting diode, and/or other semiconductor device which includes one or more semiconductor layers, which may include silicon, silicon carbide, gallium nitride and/or other semiconductor materials, a substrate which may include sapphire, silicon, silicon carbide and/or other microelectronic substrates, and one or more contact layers which may include metal and/or other conductive materials. A solid state lighting device produces light (ultraviolet, visible, or infrared) by exciting electrons across the band gap between a conduction band and a valence band of a semiconductor active (light-emitting) layer, with the electron transition generating light at a wavelength that depends on the band gap. Thus, the color (wavelength) of the light emitted by a solid state emitter depends on the materials of the active layers thereof. In various embodiments, solid state light emitters may have peak wavelengths in the visible range and/or be used in combination with lumiphoric materials having peak wavelengths in the visible range. Multiple solid state light emitters and/or multiple lumiphoric materials (i.e., in combination with at least one solid state light emitter) may be used in a single device, such as to produce light perceived as white or near-white in character. In certain embodiments, the aggregated output of multiple solid state light emitters and/or lumiphoric materials may generate warm white light output having a color temperature range of from about 2700K to about 4000K. 
         [0024]    Solid state light emitters may be used individually or in combination with one or more lumiphoric materials (e.g., phosphors, scintillators, lumiphoric inks) and/or optical elements to generate light at a peak wavelength, or of at least one desired perceived color (including combinations of colors that may be perceived as white). Inclusion of lumiphoric (also called ‘luminescent’) materials in lighting devices as described herein may be accomplished by direct coating on solid state light emitter, adding such materials to encapsulants, adding such materials to lenses, by embedding or dispersing such materials within lumiphor support elements, and/or coating such materials on lumiphor support elements. Other materials, such as light scattering elements (e.g., particles) and/or index matching materials may be associated with a lumiphor, a lumiphor binding medium, or a lumiphor support element that may be spatially segregated from a solid state emitter. 
         [0025]      FIGS. 1 through 5  illustrate various perspective views of an optic,  100 , according to example embodiments of the present invention. In example embodiments, the optic is substantially made of clear, optical material such as glass or plastic. Such material has an index of refraction of approximately 1.5. The refractive indices of glasses and plastics vary, with some having an index of refraction as low as 1.48 and some having an index of refraction as high as 1.59. Exit surface  102  is visible in  FIGS. 1 ,  2 , and  3 . In example embodiments, the exit surface is substantially flat. In at least some embodiments, the exit surface is annular in shape due to the recess for the concentrator lens discussed in more detail below. Mounting feature  104  is visible in  FIGS. 1 ,  2 , and  5 . Disposed between the flat, annular exit surface  102  and the mounting feature  104  is an outer surface  106  that provides the TIR surface for the optical element. Surface  106  is visible in  FIG. 1 ,  FIG. 2 ,  FIG. 4 , and  FIG. 5 . Mounting feature  104  serves as a spacer to maintain the various optical surfaces of the optical element at an appropriate distance from an LED light source. Mounting feature  104  may be molded into and form a part of the optic. Alternatively, mounting feature  104  may be a separate component and may or may not be made of a different material than the main portion of optic  100 . In such a case, mounting feature  104  might be fastened to the rest of optic  100  with adhesive. The mounting feature can also be attached to or supported by a structure adjacent to the main body of the optic such as a portion of a fixture or lighting system making use of the optic. 
         [0026]    Referring to  FIGS. 3 ,  4 , and  5 , entry surface  108  is visible in  FIG. 4  and  FIG. 5 , and concentrator lens  110 , opposite the entry service  108 , is visible in  FIG. 3 . In this example embodiment, the concentrator lens is a convex, refracting surface that forms a convex lens. Also in this embodiment, the entry surface is a curved entry surface. As can also be seen in  FIG. 3 , convex refractive surface  110  is recessed relative to flat, annular exit surface  102 . In example embodiments, mounting feature  104  is sized so that an LED would be at a focal point of the convex refractive surface  110 . Mounting feature  104  may also space curved entry surface  108  appropriately from an LED light source. In example embodiments, the LED light source is opposite the radial center of the curved entry surface  108  from the convex refractive surface, and is the focal point for concentrator lens  110 . 
         [0027]    Referring now to  FIGS. 1 ,  2 , and  3 , the recessed convex refractive surface defines a substantially cylindrical wall  112  between the flat annular exit surface and the base of the convex refractive surface. In at least some embodiments, the angle between the substantially cylindrical wall and the flat, annular exit surface is greater than 90 degrees. Stated differently, the substantially cylindrical surface  112  has a slightly conical shape. The geometric details of this part of the optical element  100  are more apparent in  FIG. 6 , discussed below. 
         [0028]    Turning to  FIG. 6 , a cross section of optic  100  is shown, with many dimensions indicated by additional reference numbers. In example embodiments, the length  602  of the main body of the optic is between about 16 mm and about 26 mm. In some embodiments, this length is from about 20 mm to about 23 mm. In still additional embodiments, this length is about 21.71 mm. Measurement  602  also specifies the length of the outer surface  106 . In at least some embodiments, this surface is at least partially parabolic. A parabolic shape as may be used in at least portions or sections of outer surface  106  is defined by the formula: 
         [0000]    
       
         
           
             z 
             = 
             
               
                 cr 
                 2 
               
               
                 1 
                 + 
                 
                   
                     1 
                     - 
                     
                       ( 
                       
                         1 
                         - 
                         
                           
                             kc 
                             2 
                           
                            
                           
                             r 
                             2 
                           
                         
                       
                       ) 
                     
                   
                 
               
             
           
         
       
     
         [0000]    where x, y and z are positions on a typical 3-axis system, k is the conic constant, and c is the curvature. The formula specifies conic shapes generally. For a parabolic shape, k is less than or equal to −1. However, it should be noted that the outer surface being or including a surface that is parabolic, and indeed being or including a surface that is conic is just an example. Optical elements could be designed with outer surfaces of various shapes; for example, angled, arced, curved as well as spherical, including segmented shapes. 
         [0029]    A parabolic surface or parabolic surfaces as shown in the examples disclosed herein may be used to provide total internal reflection (TIR), however, there may be instances where total internal reflection is not be needed or desired at all points of the optic. In at least some embodiments, the cross-sectional curve of surface  106  may include several parabolic curve sections combined by simulation to maximize the TIR characteristics of the optic. 
         [0030]    Still referring to  FIG. 6 , curved entry surface  108  in example embodiments has a radius R between 1.5 mm and 2.0 mm. In some embodiments, the radius R is about 1.8 mm. The width  604  of the surface can be about 3.6 mm, or range from about 3.0 mm to 4.0 mm. The distance  606  from the edge of the curved entry surface to the edge of the optic when the width of the entry surface is about 3.6 mm, is about 1.64 mm. This distance can vary with the width of the entry surface when the total width  608  of the entry portion of the optic is maintained. In some embodiments width  608  can range from about 6.5 mm to about 7.0 mm. In some embodiments, width  608  is about 6.88 mm. In some embodiments, the base of the concentrator lens  110  is at a distance  618  from flat, annular exit surface  102  of from about 14 mm to about 18 mm. In some embodiments this recess distance can be from about 15.5 mm to about 16.0 mm. In some embodiments, this recess distance is about 15.83 mm. These dimensions, together with the thickness  619  for spacer  104  of from about 0.5 mm to about 1.0 mm, or in some embodiments, about 0.75 mm, keep the optical surfaces of the optical element at an appropriate distance from packaged LED  620 . In such embodiments, the LED chip itself is at or near the focal point of concentrator lens  110 , and at the other side of the radial center of curved entry surface  108  from the convex refractive surface. 
         [0031]    In at least some embodiments, the chip is coated with or packaged with a lumiphor in order to create substantially white light. The emitter package can be referred to herein merely as an “LED” even if it contains more elements than a lone semiconductor die. In at least some systems, the LED chip itself is packaged and fastened to a flat structure that is or is similar to a small circuit board, which provides electrical connections. The LED device lens may also be fixed to this structure, which can be referred to as a “submount.” The submount and lens of the LED device package in  FIG. 6  are shown in broken lines. 
         [0032]    Continuing with  FIG. 6 , example dimensions of the exit portions of optic  100  in some embodiments may be as follows. The total width  640  across the flat, annular exit surface in example embodiments can be from about 20 mm to about 30 mm. In some embodiments, this width is from about 25 mm to about 26 mm. In at least some embodiments, the width is about 25.39 mm. The distance  642  across the base of the concentrator lens that is recessed within the optic can be from about 6.5 mm to about 7 mm. In at least some embodiments, this width is from about 6.8 mm to about 6.9 mm, or about 6.85 mm. Cylindrical wall  112  may be perpendicular to the base of concentrator lens  110 , in which case the width of the annular part of the exit surface,  644 , is just the difference between width  640  and distance  642 . However, in some embodiments, angle A is greater than 90°. Thus, the cylindrical shaft formed by the recess of concentrator lens  110  has a “draft” of anywhere from a fraction of a degree to several degrees. In at least some embodiments, angle A is about 91°. In this case, distance  644  across the annular part of the exit surface is about 9 mm. In various embodiments, distance  644  can be anywhere from about 8 mm to about 10 mm, or from about 8.5 mm to about 9.5 mm. If any of the distances shown in  FIG. 6  are altered within the example ranges given, adjustments may need to be made to other surfaces and distances in the optic. The size of the optic can also be adjusted to accommodate variations. 
         [0033]    The optic works in part because the conic or parabolic outer surface provides for many light rays to be totally reflected internally and exit the optic through the exit surface  102  at or near a normal angle relative to the exit surface. However, since the entry surface is curved and possibly spherical in shape like the light pattern from the LED, light rays are not bent by the entry surface. Light rays which strike outer surface  106  are reflected through exit surface  102  at a normal angle. If the exit surface were contiguous across its diameter, light rays that came from the light source straight up would also exit the optic at a normal angle. However, all other light rays would leave the optical element through the exit surface  102  at an angle and be bent away from the normal vector relative to exit surface  102  if the exit surface were contiguous, since these rays would be passing from a medium with a refractive index of roughly 1.5 into air, which has a refractive index of approximately 1. This bending away would actually decrease the collimation of the light through the optical element. The recessed concentrator lens is provided to collimate these light rays so that substantially all the light leaving the optic is collimated. 
         [0034]    In at least some embodiments, the concentrator lens can be molded into the optic, for example where acrylic is used and the entire optic is injection molded. The concentrator lens could also be placed upon a flat recessed surface within the optic and fastened there with adhesive, force fit into the recess, or otherwise mounted by fasteners, tabs, or the like. These latter techniques may be more effective if the concentrator is other than a convex lens surface, such as the Fresnel lens shown in  FIG. 7 , which illustrates a portion of an optic according to additional embodiments of the invention. Optic  700  includes mostly the same surfaces and features previously discussed, as indicated by like reference characters. However, optic  700  includes Fresnel lens  710  as a concentrator lens in lieu of the convex surface previously shown. The design of a Fresnel lens can vary and other dimensions of the optic may need to be adjusted accordingly. 
         [0035]      FIG. 8  shows a detailed view of the mounting feature and entry surface of the optic according to example embodiments. In  FIG. 8 , it can be observed that mounting feature  104  includes a square aperture defined by four sides  802 . In the examples shown herein this aperture is adapted, sized, and/or shaped so that the mounting feature fits around and/or conforms to the submount of the LED device package used. Entry surface  108  then conforms to the lens of the LED package. It can be said that the mounting feature and entry surface together form an optic-device interface  804  that conforms to the LED device package. The shape of the aperture and the entry surface can very to accommodate various types of LED devices and packages. The aperture could be round, oval, rectangular, or irregularly shaped. The entry surface likewise could be cubic, square, triangular, conical, or any other geometric shape needed and could conform to, as examples, an LED package with a hemisphere-shaped lens or a cubic-shaped lens. 
         [0036]      FIG. 9  is an illustration of a lighting system making use of an optical element as described herein. Lighting system  900  is formed to be a replacement for a standard R30 incandescent bulb of the type commonly used in so-called “recessed can” ceiling light fixtures. The lighting system includes a standard threaded base  902 , through which is provided an electrical connection for the LED. In the example of  FIG. 9 , a power supply or driver (not shown) is included within the base of the lighting system so that the system can be function from standard AC line voltage. Seven LEDs are used as the light source and are located inside the lighting system behind front plate  904 . Cooling fins  906  aid in maintaining an appropriate operating temperature inside the system. There is a void above each LED module, and the void contains optical element  910 , which is an optical element according to example embodiments of the present invention. 
         [0037]      FIG. 9  presents just one example of a use of an optical element according to embodiments of the present invention. An individual optic can be used in smaller lighting systems such as those based on an “MR” form factor. The optic can be used in any of various systems that require an AC to DC driver. Additionally, the optic can be used in DC-based systems that do not require AC to DC voltage conversion. Examples of such uses include use in vehicular lighting systems such as off-road vehicles, trucks, cars, boats and marine vehicles, agricultural vehicles, military vehicles, ATV/UTV dirt bikes, mining vehicles, fire and rescue vehicles, etc., as well as in compact, battery-operated systems such as flashlights. 
         [0038]      FIG. 10  is an illustration of another example lighting system making use of optical elements as described herein. Lighting system  1000  is a so called, “light bar” for a vehicle. The lighting system includes mounting brackets  1002  to which the housing  1003  is fastened with bolts  1004 . Lighting system  1000  includes built-in circuitry (not shown) to drive the LEDs. In this case, the power supplied is vehicular DC power so that the circuitry does not need to provide AC to DC conversion. Twenty LEDs are used as the light source and are located inside the lighting system behind optical elements  1010 , which are similar to or the same as the optic shown in  FIGS. 1-6 . The optical elements and corresponding light sources are arranged in two rows of ten. However, any other arrangement is possible with many different numbers of light sources and optics. A light bar or light panel like that of  FIG. 10  can also include an AC to DC power supply or driver, a standard AC line cord, and a stand or bracket so that the lighting system can serve more appropriately as a task light or work light. 
         [0039]    Although specific embodiments have been illustrated and described herein, those of ordinary skill in the art appreciate that any arrangement which is calculated to achieve the same purpose may be substituted for the specific embodiments shown and that the invention has other applications in other environments. This application is intended to cover any adaptations or variations of the present invention. The following claims are in no way intended to limit the scope of the invention to the specific embodiments described herein.
A narrow-beam optic and a lighting system using the optic are disclosed. Embodiments of the present invention provide an optical element, or "optic" that can enable a lighting system to achieve beam control. The optic collects light from substantially all angles of an LED's light output and collimates the light into a narrow beam angle. In example embodiments, the optic includes an entry surface, an exit surface, and a concentrator lens opposite the entry surface and recessed relative to the exit surface. In example embodiments, a mounting feature or spacer adjacent to the entry surface spaces the entry surface and concentrator lens from an LED. An outer surface serves to provide total internal reflection (TIR) and is disposed between the exit surface and the mounting feature.