Abstract:
The present disclosure provides an optical system including a TIR mother lens and a secondary output lens, preferably for efficiently distributing light out of an LED track lighting system. The optical system of the present disclosure is configured to create variant beam angles from a lens assembly using the same TIR lens. Preferably, by altering the dimensions and focal lengths of the secondary output lens in a single TIR lens, the optical system can create a variety of beam angles, including, but not limited to, Spot (“SP”), Narrow Flood (“NFL”), Flood (“FL”), or Wide Flood (“WFL”) beam angles.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present patent application is related to and claims the benefit of priority to U.S. Provisional Application Ser. No. 62/137,059, filed Mar. 23, 2015, and U.S. Provisional Application Ser. No. 62/060,448, filed Oct. 6, 2014. Each of the aforementioned patent applications is incorporated by reference herein in its entirety for any purpose whatsoever. 
     
    
     BACKGROUND 
       [0002]    In the field of optics, there are various types of lenses which are commonly used independently from one another, each serving a distinct purpose and having a differing function. For example, total internal reflection (“TIR”) lenses are often used for illumination or display by light emitting diodes (“LEDs”) in light fixtures. Total internal reflection occurs when a light wave strikes the interface between two media that have different refractive indices at an angle that is so great that light cannot pass through the interface but is entirely reflected. TIR lenses can be conical in shape and provide rotational symmetry which provides desired intensity of light at different angles. A Fresnel lens is often used in focusing and imaging applications. It has a large aperture and short focal length, and is made up of a set of concentric, micro-grooved sections which provide collimated light rays which preferably do not diverge in distance. A micro lens is a negative-focal-length micro-structured flat lens. It is mainly used for widening a collimated beam while preserving or improving on the beam uniformity. It has been widely used in linear general lighting. These types of lenses serve vastly different functions and thus have not previously been combined into a single optical system for use in conjunction with one another. 
       SUMMARY 
       [0003]    The present disclosure provides an optical system including a TIR mother lens and a secondary output lens, preferably for efficiently distributing light out of an LED track lighting system. The optical system of the present disclosure is configured to create variant beam angles from a lens assembly using the same TIR lens. Preferably, by altering the dimensions and focal lengths of the secondary output lens in a single TIR lens, the optical system can create a variety of beam angles, including, but not limited to, Spot (“SP”), Narrow Flood (“NFL”), Flood (“FL”), or Wide Flood (“WFL”) beam angles. The optical system of the present disclosure provides a conical-shaped TIR lens which allows for placement of a light source at the entrance of the lens, and a secondary Fresnel lens or micro lens placed within the output surface area of the TIR lens, and spaced parallel to, but a distance apart from, the light source. The secondary Fresnel lens or micro lens is preferably set a distance apart from the light source by placing the secondary lens at one end of a hollow cut-out from the TIR lens which is preferably filled with air, with the light source placed at the other end of the cut-out. Preferably, the secondary lens can be interchangeable within the single TIR lens. 
         [0004]    Both the TIR and secondary lenses are preferably made of generic poly(methyl methacrylate) (“PMMA”) which is a thermoplastic often used in optics as an alternative to glass (having a refractive index of about 1.4893 to 1.4899), but it will be appreciated that other suitable materials can be used, such as acrylic glass (refractive index of about 1.49 to 1.492), polycarbonate (refractive index of about 1.584 to 1.586), polyethylene terephthalate (PET) (refractive index of about 1.575), crown glass (refractive index of about 1.50-1.54), and Pyrex® glass (refractive index of about 1.47). More generally speaking, both the TIR and secondary lenses are preferably made from a material having a refractive index between about 1.3 and about 2.0 and in any incremental value within this range of about .001. 
         [0005]    According to various embodiments of the present disclosure, the geometry of a TIR lens and secondary lens combination can be altered based on a number of mutually exclusive variables which can change in any embodiment of the disclosure, either individually or in combination. For example, the input and output aperture in the TIR lens can be altered to vary the overall triangular cross sectional profile of the lens and therefore diverges the beam passing through the TIR lens differently. The conical surface curvature of a TIR lens can be varied to yield a desired intensity distribution and beam spread. The conical surface of a TIR lens acts as a highly reflective reflector surface because of total internal reflection (TIR). 
         [0006]    A Fresnel lens is a refractor collimator. Thus, by combining the collimating power of both types of lens, one can achieve even higher center beam intensity with the minimal loss. The diameter and/or focal length of the Fresnel lens can be altered to provide varied beam angles. 
         [0007]    Preferably, varying the secondary lens within a single TIR lens can result, for example, in four different beam angles from the optical system of the present disclosure: a) a Spot beam (at an angle of 0-17°, or any angular increment therebetween of 0.1 degrees), b) a Narrow Flood beam (at an angle of 18-25°, or any angular increment therebetween of 0.1 degrees), c) a Flood beam (with an angle of 26-39°, or any angular increment therebetween of 0.1 degrees), and d) a Wide Flood beam angle (with an angle of 40° or greater in any increasing angular increment of 0.1 degrees), respectively. While using the same TIR lens and maintaining the distance between the light source and the secondary lens, the focal length of the secondary lens can be altered to affect the resulting beam angle and the center beam output. This allows the optical system of the present disclosure to be used in a variety of products and for a multitude of applications. 
         [0008]    In some embodiments, the disclosure provides an optical system that includes a TIR lens and a secondary lens. The TIR lens has a first end and a second end, and is configured to refract light from a light source near the first end of the TIR lens. The secondary lens is attached proximate the second end of the TIR lens. The secondary lens is configured to redirect the light passing through the secondary lens. 
         [0009]    In some implementations, the secondary lens can be coaxially co-located with the TIR lens. The TIR lens can define a central passage therethrough that passes through the second end of the TIR lens to define an opening in the TIR lens. The secondary lens can cover the opening and can be about the same size as the opening, or larger. The secondary lens can be a Fresnel lens or a micro lens, for example. The TIR lens is preferably annularly shaped and can define a patterned surface portion at its distal end for redirecting light passing therethrough. 
         [0010]    The secondary lens can define a patterned surface portion thereon for redirecting light passing therethrough. The secondary lens can have a diameter that is between about one percent of the diameter of the TIR lens, and 100 percent the diameter of the TIR lens, and in any desired increment therebetween of 1 percent. If desired, the ratio of the radius Ri of the secondary lens to that of the TIR lens at the second end of the system can be between about 0.01 to about 1.0, for example. The ratio of the height of the TIR lens to the radius of the TIR lens can be between about 0.1 to about 10.0, for example. 
         [0011]    If desired, the secondary lens can be removably attached to the TIR lens. For example, the secondary lens can be attached to the TIR lens via an interference fit, snap fit, threaded connection, threaded or other fastener, adhesive, and the like. For example, a protrusion on one or more of the secondary lens and TIR lens can be received in a corresponding cavity of one of the TIR lens and secondary lens to couple the secondary lens to the TIR lens. 
         [0012]    In further accordance with the disclosure, a light fixture is provided that includes a housing, a light source (such as a LED or group of LEDs) and a TIR lens. The TIR lens can be located within the housing, and can be configured to refract light from the coaxially located light source. The TIR lens can define a central well. The TIR lens can further include a secondary lens disposed over the central well, located at a distance from the coaxially aligned light source and attached to the TIR lens. The secondary lens is configured to redirect the light from the light source. The light fixture can be provided with any of the features or characteristics disclosed elsewhere herein. 
         [0013]    All of the components of the optical system of the present disclosure can be incorporated into a housing for use in a variety of products. A benefit of embodiments of the present disclosure is the ability to obtain a plurality of output beams—preferably selected from the group of SP, NFL, FL, and WFL beams—for output in a single device, allowing a user to alter the uses of embodiments of the present disclosure system by mere variation of the secondary lens. Preferably, the optical system of the present disclosure can be utilized for LED lighting from an LED source. 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0014]      FIG. 1( a )  is a side perspective view of the optical system of the present disclosure, containing a TIR lens and a circular Fresnel lens placed therein; 
           [0015]      FIG. 1( b )  is a cross sectional view of the optical system seen in  FIG. 1 , showing the ray-tracing of the TIR lens and the Fresnel lens; 
           [0016]      FIG. 1( c )  is a side perspective view of the optical system seen in  FIG. 1 , with the Fresnel lens having been removed from the distal end of the central well in the TIR lens; 
           [0017]      FIG. 1( d )  is a top perspective view of the optical system seen in  FIG. 1 , showing the central well of the TIR lens and placement of the light source at the proximal end thereof; 
           [0018]      FIGS. 1( e )-1( g )  are views of a mother TIR lens in combination with a micro lens; 
           [0019]      FIG. 2( a )  is a side perspective view of an illustrative lens system of the disclosure configured to deliver a spot (SP) beam; 
           [0020]      FIG. 2( b )  is a plotted graph showing the intensity distribution of the Spot beam; 
           [0021]      FIG. 3( a )  is a side perspective view of an illustrative lens system of the disclosure configured to deliver a narrow flood (NF) beam; 
           [0022]      FIG. 3( b )  is a plotted graph showing the intensity distribution of the Narrow Flood beam; 
           [0023]      FIG. 4( a )  is a side perspective view of an illustrative lens system of the disclosure configured to deliver a flood (FL) beam; 
           [0024]      FIG. 4( b )  is a plotted graph showing the intensity distribution of the Flood beam; 
           [0025]      FIG. 5( a )  is a side perspective view of an illustrative lens system of the disclosure configured to deliver a wide flood (WFL) beam; 
           [0026]      FIG. 5( b )  is a plotted graph showing the intensity distribution of the Wide Flood beam; 
           [0027]      FIG. 6( a )  is a side perspective view of an exemplary mother TIR lens used in the embodiments of  FIGS. 2-5 ; 
           [0028]      FIG. 6( b )  is a plotted graph showing the intensity distribution of the mother TIR lens; 
           [0029]      FIGS. 7( a )-7( e )  illustrate further aspects of the lens assembly of  FIG. 2( a ) ; 
           [0030]      FIGS. 8( a )-8( e )  illustrate further aspects of the lens assembly of  FIG. 3( a ) ; 
           [0031]      FIGS. 9( a )-9( e )  illustrate further aspects of the lens assembly of  FIG. 4( a ) ; 
           [0032]      FIGS. 10( a )-10( e )  illustrate further aspects of the lens assembly of  FIG. 5( a ) ; and 
           [0033]      FIG. 11  is a cross section of an exemplary light fixture including an embodiment of the disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0034]    Descriptions herein of the optical systems and lenses of the present disclosure shown in  FIGS. 1-11  represent conceptual embodiments of systems embodying the principles of the disclosed embodiments. It should be understood that these figures and embodiments are exemplary in nature and in no way serve to limit the scope of the disclosure. 
         [0035]    As can be seen in  FIGS. 1( a )-( d ) , one illustrated embodiment  10  includes a TIR lens  20  which is preferably conically shaped. At the flat proximal surface  22  of the TIR lens, there is a light source  30 , which is preferably an LED light source. Light source  30  is positioned to refract light into the TIR lens which can then provide symmetrical light distribution. 
         [0036]    Extending within the TIR lens, and coaxially located with respect to the light source  30  placed at the flat proximal surface  22 , is a cut-out segment  24  of the TIR lens, which is more preferably filled with air, through which light can be passed from the light source  30 . At the opposite distal end  26  of the cut-out segment  24 , and a Fresnel lens  40  can be placed so that it falls within the surface area of TIR lens  20  and spaced a distance apart from the light source  30 . Preferably, the Fresnel lens  40  can be interchangeable within a single TIR lens  20 . By combining the TIR lens  20  with the Fresnel lens  40 , the system can emit a strong central beam. This provides an improvement over the use of a TIR lens individually, which lacks refractive collimating power, and over the use of a Fresnel lens individually, which lacks reflective collimating power. 
         [0037]      FIGS. 1 e -1 g    similarly illustrate a system that places a micro lens  45  at the opposite distal end  26  of the cut-out segment  24  rather than a Fresnel lens so that it falls within the surface area of TIR lens  20  and spaced a distance apart from the light source  30 . Preferably, the micro lens  45  can be interchangeable within a single TIR lens  20 . By combining the TIR lens  20  with the micro lens  45 , the light source can emit a desired wider beam. 
       EXAMPLES 
       [0038]    The presently provided examples presented below in  FIGS. 2-10  are intended to be non-limiting and are presented to illustrate aspects of inventions provided in accordance with the disclosure. 
         [0039]    As can be seen in  FIGS. 2( a )-5( a ) , the optical system  10  preferably provides the additional benefit of enabling a single TIR lens  20  to be used with a variety of secondary (e.g., Fresnel type or other) lenses to create different beam angles of projected light. Preferably, using a single TIR lens  20  and light source  30 , at least four different inserted lenses  50 ,  52 ,  54 , and  56 —each with a different diameter, focal length and surface geometries—can be used to create Spot beam (e.g., at an angle of 0-17°, or any angular increment therebetween of 0.1 degrees), a Narrow Flood beam (e.g., at an angle of 18-25°, or any angular increment therebetween of 0.1 degrees), a Flood beam (e.g., with an angle of 26-39°, or any angular increment therebetween of 0.1 degrees), and a Wide Flood beam angle (e.g., with an angle of 40° or greater in any angular increment above) 40°), respectively. Of the aforementioned embodiments, the embodiments of  FIGS. 2 and 3  use a Fresnel lens insert, while the embodiments of  FIGS. 4 and 5  use a micro lens insert, which uses a pattern of (e.g., hexagonal or other shaped) elements to spread out the resulting beam. 
         [0040]    A cross sectional side schematic of a secondary micro lens installed over a mother TIR lens is presented in  FIG. 1( f ) . The illustrated micro lens insert is a flat lens element that can have micro geometries on one-side or both sides of the lens. Such a lens can be used for spreading out a collimated beam into a wide-distribution beam such as Flood (FL) or Wide Flood (WFL). Its role as opposed to the aforementioned Fresnel secondary lens can be compared to a concave lens vs. a convex lens, where the former spreads out a collimated beam while the latter takes a natural beam at focus and collimate it. 
         [0041]    As disclosed herein, the micro-lens insert has micro-lens geometries only on the perimeter that covers the output surface of the mother TIR lens where the collimated beam comes out but leaves the center that covers the air-well of the TIR lens transparent, or with slight surface treatment such as frosting to soften the beam. Therefore, the collimated beam is spread wider by the micro-lens while the direct light from the LED source comes out without collimation to also serve as part of the wider beam. 
         [0042]    Plotted graphs showing the intensity distributions emitted through the different lenses  50 ,  52 ,  54 , and  56  inserted into a mother TIR lens  20  can be seen in  FIGS. 2( b )-5( b ) , corresponding with the inserted lenses seen in  FIGS. 2( a )-5( a ) , respectively. This allows the optical system  10  of the present disclosure to be used in a variety of applications and products, while using a single housing  12  (e.g.,  FIG. 11 ), the same TIR lens  20 , and the same light source  30 , despite the need for variation in central beam intensity. 
         [0043]    It will be appreciated that the focal length of the secondary lens insert can be any desired distance, to produce beam angle from about 5° to about 150°, in any desired increment there between, for example, of one degree. Moreover, the ratio of the radius Ri of the secondary lens (e.g.,  50 ) to that of the TIR lens (e.g., 20) at the distal face of the assembly Ro can range, for example, from about 0.01 to about 1.0 and in any desired increment there between of about 0.01. At the same time, the ratio of the height H of the TIR lens to its Radius Ro can vary from about 0.1 to about 10.0 and in any desired increment there between of about 0.1. Moreover, the distance between the LED and the TIR lens entrance  22  can be varied from about 1 mm to about 20 mm and in any desired increment there between of about 0.1 mm. 
         [0044]    In some embodiments, spot beams can be used for illuminating an object on a wall, a flood beam can be used for ceiling light, and a wide flood beam can be used to light a hallway. As can be seen in  FIG. 1( c ) , a Fresnel lens  40  can be removed from the TIR lens  20  to be replaced with another Fresnel or other lens of varying specifications to create different beam angles. Thus, as can be seen in  FIGS. 2( a )-5( a ) , lenses  50 ,  52 ,  54 , and  56  can be interchanged within the same TIR lens  20  for creation of SP, NFL, FL, and WFL beam angles, respectively. It will also be appreciated that the diameter of the secondary lens can be any suitable diameter and may overlap the surface of the mother TIR lens to any desired extent as is needed to effectuate the desired design. 
         [0045]    A non-limiting example of an illustrative mother TIR lens and corresponding polar plot are presented in  FIGS. 6( a )-6( b ) , respectively. As can be seen, six receiving apertures  60  are symmetrically positioned about a central orifice  62  for receiving corresponding alignment and fixation pegs  64  from a corresponding lens insert. As will be appreciated by those of skill in the art, other retaining structures may be used instead of the disclosed peg/orifice combination, such as snap fit connections, threaded connections, adhesive and the like. 
         [0046]      FIGS. 7( a )-7( e )  illustrate the lens system illustrated in  FIG. 2A  in further detail. As can be seen in  FIG. 7( a ) , a mother TIR lens  20  is presented with the aforementioned receiving apertures. Also presented is a central Fresnel lens  50  with three symmetrically spaced fixation pegs  64  for insertion into three of the receiving apertures  60 . While any method of joining can be accomplished (threaded connection, snap fit, etc.), the illustrated technique can provide for a removable lens insert that can be substituted with other inserts if a user&#39;s preference changes or simply to provide versatility. The extra three orifices are provided for substitution if any pegs were broken in the first three orifices when removing a previous insert. 
         [0047]      FIG. 7( b )  presents an end view of the lens assembly  10 , whereas  FIG. 7( c )  presents a central longitudinal cross sectional view of the lens assembly  10 , illustrating the mother TIR lens  20 , and the central Fresnel lens  50  attached to the mother TIR lens  20  via fixation pegs  64 . Also present in  FIG. 7( c )  is a stepped central aperture  24  defined through the mother TIR lens  20  including a distal-most chamber adjacent the Fresnel lens  50  that steps radially inward at its proximal end to form a central generally cylindrical chamber that is joined to a conical chamber with a slight taper that terminates at a proximal opening defined into the mother TIR lens  20 .  FIG. 7( d )  presents an exploded view of the lens assembly  10 , illustrating the mother TIR lens  20 , and the Fresnel lens  50 , wherein the detail illustrates a prismatic patterning  28  around an annularly shaped distal face of the mother TIR lens. The patterning  28  is for maximizing beam uniformity without sacrificing central beam and beam angle.  FIG. 7( e )  presents a rear facing exploded view of the lens assembly, again illustrating the mother TIR lens  20  and the Fresnel lens  50 . 
         [0048]      FIGS. 8( a )-8( e )  illustrate the lens system illustrated in  FIG. 3A  in further detail. As can be seen, a mother TIR lens  20  is presented with the aforementioned receiving apertures. Also presented is a central Fresnel lens  52  with three symmetrically spaced fixation pegs  64  for insertion into three of the receiving apertures. It will be appreciated that the diameter can be any suitable diameter and may overlap the surface of the mother TIR lens to any desired extent as is needed to effectuate the desired design. 
         [0049]      FIG. 8( b )  presents an end view of the lens assembly  10 , whereas  FIG. 8( c )  presents a central longitudinal cross sectional view of the lens assembly  10 , illustrating the mother TIR lens  20 , and the central Fresnel lens  52  attached to the mother TIR lens  20  via fixation pegs  64 . Also present in  FIG. 8( c )  is a stepped central aperture  24  defined through the mother TIR lens  20  including a distal-most chamber adjacent the Fresnel lens  52  that steps radially inward at its proximal end to form a central generally cylindrical chamber that is joined to a conical chamber with a slight taper that terminates at a proximal opening defined into the mother TIR lens  20 .  FIG. 8( d )  presents an exploded view of the lens assembly  10 , illustrating the mother TIR lens  20 , and the Fresnel lens  52 , wherein the detail illustrates a hexagonal patterning  28  around an annularly shaped distal face of the mother TIR lens. The patterning  28  is for maximizing beam uniformity without sacrificing central beam and beam angle.  FIG. 8( e )  presents a rear facing exploded view of the lens assembly, again illustrating the mother TIR lens  20  and the Fresnel lens  52 . As further illustrated in  FIG. 8( e ) , lens  52  also includes a patterned portion molded therein in a grid pattern for the best beam uniformity. 
         [0050]      FIGS. 9( a )-9( e )  illustrate the lens system illustrated in  FIG. 4( a )  in further detail. As can be seen, a mother TIR lens  20  is presented with the aforementioned receiving apertures. Also presented is a micro lens  54  with three symmetrically spaced fixation pegs  64  for insertion into three of the receiving apertures, as with the two preceding embodiments. 
         [0051]      FIG. 9( b )  presents an end view of the lens assembly  10 , whereas  FIG. 9( c )  presents a central longitudinal cross sectional view of the lens assembly  10 , illustrating the mother TIR lens  20 , and the central micro lens  54  attached to the mother TIR lens  20  via fixation pegs  64 . Also present in  FIG. 9(c)  is a stepped central aperture  24  defined through the mother TIR lens  20  including a distal-most chamber adjacent the micro lens  54  that steps radially inward at its proximal end to form a central generally cylindrical chamber that is joined to a conical chamber with a slight taper that terminates at a proximal opening defined into the mother TIR lens  20 .  FIG. 9( d )  presents an exploded view of the lens assembly  10 , illustrating the mother TIR lens  20 , and the micro lens  54 , wherein the detail illustrates a hexagonal prismatic patterning  28  around an annularly shaped distal face of the mother TIR lens  20 . The patterning  28  is for maximizing beam uniformity without sacrificing central beam and beam angle.  FIG. 9( e )  presents a rear facing exploded view of the lens assembly, again illustrating the mother TIR lens  20  and the micro lens  54 .  FIG. 9( e )  shows the micro lens structure details on lens  54 . 
         [0052]      FIGS. 10( a )-10( e )  illustrate the lens system illustrated in  FIG. 5( a )  in further detail. As can be seen, a mother TIR lens  20  is presented with the aforementioned receiving apertures. Also presented is a micro lens  56  with three symmetrically spaced fixation pegs  64  for insertion into three of the receiving apertures, as with the three preceding embodiments. 
         [0053]      FIG. 10( b )  presents an end view of the lens assembly  10 , whereas  FIG. 10( c )  presents a central longitudinal cross sectional view of the lens assembly  10 , illustrating the mother TIR lens  20 , and the central micro lens  56  attached to the mother TIR lens  20  via fixation pegs  64 . Also present in  FIG. 10( c )  is a stepped central aperture  24  defined through the mother TIR lens  20  including a distal-most chamber adjacent the micro lens  56  that steps radially inward at its proximal end to form a central generally cylindrical chamber that is joined to a conical chamber with a slight taper that terminates at a proximal opening defined into the mother TIR lens  20 .  FIG. 10( d )  presents an exploded view of the lens assembly  10 , illustrating the mother TIR lens  20 , and the micro lens  56 , wherein the detail illustrates a patterning  28  around an annularly shaped distal face of the mother TIR lens  20 . The patterning  28  is for maximizing beam uniformity without sacrificing central beam and beam angle.  FIG. 10( e )  presents a rear facing exploded view of the lens assembly, again illustrating the mother TIR lens  20  and the micro lens  56 .  FIG. 10( e )  shows the micro lens structure details on lens  56 . 
         [0054]      FIG. 11  presents a cross section of an example of a light fixture  100  including a lens element  10  as described herein, operably positioned with respect to one or more LED elements  30 , which in turn are operably coupled to a LED driver and/or power supply  60 . 
         [0055]    Although the present disclosure herein has been described with reference to particular preferred embodiments thereof, it is to be understood that these embodiments are merely illustrative of the principles and applications of the disclosure. Therefore, modifications may be made to these embodiments and other arrangements may be devised without departing from the spirit and scope of the disclosure.