Abstract:
A folded circularly symmetric illumination optic comprising a first light transfer mode having a first central refractive surface and a second central refractive surface, wherein one of the first and second central refractive surfaces has at least one peened feature; a second light transfer mode having a first refractive surface, a first TIR surface, a second TIR surface and a second refractive surface; a third light transfer mode having a first refractive surface, a first TIR surface and a second refractive surface, wherein the first TIR surface has at least one peening feature, and wherein the second refractive surface is conical; wherein the first TIR surface and second refractive surface of the second light transfer mode is coincident at least one point, wherein the second refractive surface of the third light transfer mode is coincident with the first TIR surface and second refractive surface of the second light transfer mode.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims benefit under 35 U.S.C. §119(e) to U.S. Ser. Nos. 61/495,094, filed Jun. 9, 2011, and 61/499,250, filed Jun. 21, 2011, which are both hereby incorporated by reference in this application. 
     Throughout this application, several references and patents are referenced herein. Disclosure of these references and patents in their entirety is hereby incorporated by reference in this application. 
    
    
     BACKGROUND OF THE INVENTION 
     High efficiency etendue limited folded optics have been known for some years, such as U.S. Pat. Nos. 6,639,733, 6,896,381, 7,152,985, 7,181,378, all of which have several inventors in common with the present application. However, such prior art optics work best for narrow exit angles, which may not be desirable in some applications. Also, when used with light sources that have color separation or non uniform luminance (as nearly all LED light sources), these optics may create a pattern that mimics the color separation of the source or create artifacts that reflect the form or placement of the chip or chips. This may be a serious disadvantage in some applications in which a uniform color pattern or intensity distribution is necessary. 
     SUMMARY OF THE INVENTION 
     The present invention solves the practical issues presented by traditional high efficiency folded optics, by providing an optical architecture and method of design where the resulting optic (in combination with a solid state light source) has a wide angular output pattern and mixes the light output in such a way that the structure of the source no longer influences the uniformity of the output pattern. 
     The present invention addresses the aforementioned problem by adding specially designed peening features to optical surfaces of one embodiment in U.S. Pat. No. 6,896,381 (“patent &#39;381”). The new optic increases the output angle and mixes said output light compared to the original one so that the structure (mechanical or color) of the source is no longer visible in the output pattern. The peening process consists of adding at least one peening feature (e.g., a small “bump” or a plurality of “bumps” (as discussed below, such “bump” can have the same or differing characteristics relative to another “bump”) to the two of the surfaces of embodiment shown in FIG. 17 of patent &#39;381. Also some changes are made to the geometry of the surfaces of FIG. 17 of patent &#39;381 to improve light mixing. In embodiments of the present invention, surface 323 in FIG. 17 of patent &#39;381 can be replaced by a conical surface. In one embodiment in the present invention convex surface 322 of patent &#39;381 is replaced with a planar surface and interior surface 329 is replaced with a peened planar surface (feature  701  of  FIG. 7 ). In a preferred embodiment in the present invention surface 322 of patent &#39;381 is left convex and interior surface 329 is replaced with a peened planar surface. 
     In accordance with a first aspect of the present invention, a folded circularly symmetric illumination optic comprising: a first light transfer mode having a first central refractive surface and a second central refractive surface, wherein one of the first and second central refractive surfaces has at least one peened feature; a second light transfer mode having a first refractive surface, a first Total Internal Reflection (“TIR”) surface, a second TIR surface and a second refractive surface; a third light transfer mode having a first refractive surface, a first TIR surface and a second refractive surface, wherein the first TIR surface has at least one peening feature, and wherein the second refractive surface is conical; wherein the first TIR surface and second refractive surface of the second light transfer mode is coincident at least one point, wherein the second refractive surface of the third light transfer mode is coincident with the first TIR surface and second refractive surface of the second light transfer mode. 
     In accordance with a second aspect of the present invention, a folded circularly symmetric illumination optic comprising: a first light transfer mode comprising a first central refractive surface and a second central refractive surface, wherein one of the first and second central refractive surfaces has at least one peened feature; a second light transfer mode having a third refractive surface, a first TIR surface, a second TIR surface and a fourth refractive surface, wherein the first TIR surface and fourth refractive surface are coincident at least one point; and a third light transfer mode which has a fifth refractive surface, the second TIR surface, and a sixth refractive surface, wherein the second TIR surface has at least one peening feature; and wherein the sixth refractive surface is coincident with the first TIR surface and fourth refractive surface at least one point. 
     In another aspect, the sixth refractive surface is conical. 
     In another aspect, the second TIR surface is conical. 
     In another aspect, the first central refractive surface of the first light transfer mode is planar, and the second central refractive surface of the first light transfer mode is curved. 
     In another aspect, the first refractive surface is planar, and the second refractive surface is curved. 
     In another aspect, the at least one peened feature is a bump or a plurality of bumps. 
     In another aspect, the bump allows a spread beam angle range from 15 degrees to 60 degrees. 
     In another aspect, the plurality of bumps comprises at least one bump which allows a spread beam angle range from 15 degrees to 60 degrees. 
     In another aspect, the bump has a lens size with a diameter range from 20 mm to 50 mm. 
     In another aspect, the plurality of bumps comprises at least one bump which has a lens size with a diameter range from 20 mm to 50 mm. 
     In accordance with a third aspect of the present invention, a lighting apparatus comprising the folded circularly symmetric illumination optic herein. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The figures are for illustration purposes only and are not necessarily drawn to scale. The present invention itself, however, may be best be understood by reference to the detailed description which follows when taken in conjunction with the accompanying drawings in which: 
         FIG. 1  shows a standard open parabolic reflector with a light source in accordance with an embodiment of the present invention; 
         FIG. 2A  shows a 2D segment on the same reflector shown in  FIG. 1  with an exemplary convex peening feature in profile; 
         FIG. 2B  shows a 2D segment on the same reflector shown in  FIG. 1  with an exemplary concave peening feature in profile; 
         FIG. 3A  shows a 3D illustration of 2 profiles on same reflector segment illustrating a convex peening feature in accordance with an another embodiment of the present invention; 
         FIG. 3B  shows another view of  FIG. 3A  with ray and other additional information; 
         FIG. 3C  shows a 3D view of a reflector with at least one peened feature in accordance with an embodiment of the present invention; 
         FIG. 4  shows a close-up of exemplary peening on a refractive surface in accordance with an embodiment of the present invention; 
         FIG. 5  shows a cross-sectional view of a preferred collimator embodiment prior to it being peened; 
         FIG. 6  is a perspective 3D view of the same collimator embodiment shown in  FIG. 5  with its peened back reflector; 
         FIG. 7  is a bottom 3D perspective view of the same collimator embodiment in  FIG. 6  showing both peened surfaces; and 
         FIG. 8  shows a top 3D perspective view of a collimator embodiment with peened features on the front central face of the optic in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     A better understanding of various features and advantages of the present invention will be obtained by reference to the following detailed description of embodiments of the present invention and accompanying drawings, which set forth illustrative embodiments in which the principles of the invention are utilized. 
     We will first start with the background information needed to design the peened features. 
       FIG. 1  shows a light source  101  whose light is collimated by a reflective surface  102 . Rays  103  coming from the source are reflected and emitted vertically. 
       FIG. 2A  shows a detail of a collimating optic similar to that in  FIG. 1 . Light rays  201  and  203  coming from the light source are reflected upwards as rays  202  and  204  by reflective surface  205 . Reflective surface  205  is part of that generic collimator optic similar, for example, to that in  FIG. 1 . Rays  202  and  204  are essentially parallel and the light output is highly collimated. 
     Spreading of the output pattern can be achieved by replacing the smooth surface  205  by small “bumps” that spread the outgoing light. In this example, one of these “bumps” is an arc of a circle  206  (thick line) centered at  215  with end points  207  and  208 . At each one of these points the normal to the circle makes an angle α to the normal  209  to reflective surface  205 . Ray  201  will now be reflected by curved reflective surface  206  at point  207  in direction  210  making an angle 2α to ray  204 . Also, ray  203  is now reflected at point  208  in direction  211  making an angle 2α to ray  202 . Incoming rays parallel to  201  and  203  are reflected by  206  in directions contained between those of  210  and  211 . The output pattern is then spread by a total angle 4α. Similar “bumps” can be added to surface  205  resulting in an irregular surface. “Bumps” can also have a shape/size which allows a spread beam angle range from 15 degrees to 60 degrees and/or a lens size with a diameter range from 20 mm to 50 mm. 
     In general rays  201  and  203  are not parallel, but in any case the incident and reflected directions at point  207  define the normal to the “bump” at that point. Also, the incident and reflected directions at point  208  define the normal to the “bump” at that point. A curve can then be adjusted between points  207  and  208  that matches the desired normals. Other options include having a “bump” that starts at point  207  but does not exactly end at point  208 . The circular curves can also be replaced by conics or tailored contours. 
       FIG. 2B  shows a similar situation to that in  FIG. 2A , only now lenticulation  216  is concave instead of convex, as  206  in  FIG. 2A . Again, spreading of the output pattern can be achieved by replacing the smooth surface  205  by small “bumps” that spread the outgoing light. In this example, one of these “bumps” is a circle  216  with end points  207  and  208 . At each one of these points the normal to the circle makes an angle α to the normal  212  to reflective surface  205 . Ray  201  will now be reflected by curved reflective surface  216  at point  207  in direction  213  making an angle 2α to ray  204 . Also, ray  203  is now reflected at point  208  in direction  214  making an angle 2α to ray  202 . Incoming rays parallel to  201  and  203  are reflected by  216  in directions contained between those of  213  and  214 . The output pattern is then spread by a total angle 4α. Similar “bumps” can be added to surface  205  resulting in an irregular surface. 
       FIG. 3A  shows a 3D view of a reflective profile  301  of a collimating optic with circular symmetry around axis  302 . The meridian plane shape of the “bump” on the reflective surface is defined by circular space curve profile  303  with center  304  (although other shape profiles are also possible as described above) and space curve profile  305 . 
     Profile  303  can be convex or concave (as in  FIG. 2A  and  FIG. 2B ). The same is true for profile  305 . This results in four possible shapes for the lenticulation based on profiles  303  and  305 . 
     The shape of the “bump” in the direction perpendicular to the vertical plane (containing axis  302  and curve  301 ) is defined by another circular profile  305  with center  306  located on line  307  perpendicular to profile  301 . Arc  305  is defined by its radius and its angular aperture, as seen from its center  306 . These two parameters can be adjusted by imposing two conditions. 
       FIG. 3B  shows again the same “bump” profiles  303  and  305  as in  FIG. 3A . A light ray  308  coming from source  310  hits the edge  309  of profile  305  and leaves in a direction that makes an angle 2α to the vertical (parallel to axis  302 ). 
     Also, when projected onto the horizontal plane, edge point  309  and its symmetrical edge point  311  subtend an angle φ to the source  310 . Angle φ is given by φ=2π/N where N is the number of lenticulations in the circular direction (around axis  302 ). The above conditions define the two parameters of arc  305 : its radius and its angular aperture, as seen from its center  306 . 
     The radius of curvature for a peened surface can be calculated once the desired angular spread and the dimension of the peen feature is determined in the two directions. A useful equation is provided in the book “The Optical Design of Reflectors”, by W. Elmer, 2 nd  Edition, by equation 2 (pg. 27) for calculating the radius of curvature of a convex peen as follows: 
     
       
         
           
             
               r 
               p 
             
             = 
             
               
                 r 
                 f 
               
               
                 
                   
                     
                       [ 
                       
                         
                           
                             ( 
                             
                               2 
                               ⁢ 
                               
                                 
                                   r 
                                   f 
                                 
                                 w 
                               
                             
                             ) 
                           
                           2 
                         
                         - 
                         1 
                       
                       ] 
                     
                     
                       1 
                       2 
                     
                   
                   ⁢ 
                   
                     sin 
                     ⁡ 
                     
                       ( 
                       
                         θ 
                         2 
                       
                       ) 
                     
                   
                 
                 + 
                 
                   cos 
                   ⁡ 
                   
                     ( 
                     
                       θ 
                       2 
                     
                     ) 
                   
                 
               
             
           
         
       
     
     Where, r p  is the radius of curvature of the peen surface, r f  is the radius of curvature of reflector surface at point of peening, w is the dimension of the peened feature, θ is the maximum desired angular spread (equal to 2α). For the case when the peen is concave (or a dent in the nomenclature of Elmer) the equation becomes: 
     
       
         
           
             
               r 
               p 
             
             = 
             
               
                 r 
                 f 
               
               
                 
                   
                     
                       [ 
                       
                         
                           
                             ( 
                             
                               2 
                               ⁢ 
                               
                                 
                                   r 
                                   f 
                                 
                                 w 
                               
                             
                             ) 
                           
                           2 
                         
                         - 
                         1 
                       
                       ] 
                     
                     
                       1 
                       2 
                     
                   
                   ⁢ 
                   
                     sin 
                     ⁡ 
                     
                       ( 
                       
                         θ 
                         2 
                       
                       ) 
                     
                   
                 
                 - 
                 
                   cos 
                   ⁡ 
                   
                     ( 
                     
                       θ 
                       2 
                     
                     ) 
                   
                 
               
             
           
         
       
     
     The two profiles obtained by the method described above can now be used to build a surface containing them, which will be used as a lenticulation. The technique for creating a surface from the two curves is to use the so-called sweep transformation used in computer aided design software such as Rhinoceros by McNeel North America of Seattle, Washington. One of the curves is chosen to be the rail curve for the sweep (the direction for the sweep, while the second curve is the so-called section curve for the sweep (the profile that is swept along the rail curve). The process is well known to those skilled in the art of computer aided design. Either resultant surface can be used. 
       FIG. 3C  shows several lenticulations placed around symmetry axis  302 , forming a complete circle. 
       FIG. 4  shows a refractive surface  403  and incident rays  401  and  402  which are refracted in directions  404  and  405 , respectively. Now a portion of the optical surface between points  406  and  407  can be replaced by a “bump”  408 . Rays  401  and  402  are now refracted at points  406  and  407  in directions  408  and  409  respectively, making angles α and β to  404  and  405  respectively. As in the case of the refractive optical surface, also here the shape of  408  can be adjusted, for example, so that α=βwith β having a prescribed value, or  408  can be forced to be, for example, an arc of a circle in which case only one of the angles can be made to coincide with a prescribed value. 
     As in the case of the reflective surfaces, also here the “bumps” can be convex or concave. 
       FIG. 5  shows the profile of a rotational folded optic  501  designed for an LED light source  502  based on the optical architecture in aforementioned FIG. 17 of patent &#39;381. Folded optic  501 , comprising planar front central refractive surface  503  or optional curved surface  513  and rear central planar refractive surface  504 , side curved refractive surfaces  508  and  509 , conical front surface  506  (which operates by both TIR and refraction depending on the angle of incidence of a ray) and rear TIR surface  507 , is an optical architecture that can be used, into which in the lenticular features described above can be built in. The ray propagation through the optic operates similar to the embodiment of FIG. 17. 
     There are three modes of travel. Mode one is illustrated by ray  512  which travels through the central refractive lens region defined by refractive surfaces  503  and  504 . Central refractive surface can also be optionally curved as illustrated by surface  513 . It can be designed as a tailored nonimaging surface to collimate the light from the extended source, as is known to those skilled in the field of nonimaging optics. The second mode of travel is illustrated by ray  511 , which travels through refractive surface  509 , is redirected by TIR from front conical surface  506  to rear TIR surface  507 , whereupon it is redirected to front conical surface  506 , where it exits the optic. The third mode of travel is illustrated by ray  510 , which travels through refractive surface  508 , whereupon it is redirected to rear TIR surface  507 , which in turn redirects it to front conical surface  506  which refracts the ray and allows it to exit the optic. The 2D profile of back TIR surface  507  can be linear or a Cartesian oval. The 2D profile of refractive lenses  508  and  509  are Cartesian ovals. The 2D profiles are swept around central axis  504  to create the three dimensional lens. The design method for the starting optic can be described as follows. 
     Refractive surface  508  is a circumferentially swept hyperbola that in section collimates a point source at the center of the LED into a set of ray bundles parallel to ray  510 . Refractive surface  509  is also a circumferentially swept hyperbola which behaves similarly creating a set of parallel exit rays (in 2D). The slope of front TIR surface  506  is designed so that after these rays reflect on surface  506  these rays in 2D are parallel to ray  510  just after exiting refractive surface  508 . At this point all rays in any 2D section are parallel to each other, either coming from  508  (as ray  510 ) or from surface  506  (as ray  511  prior to striking surface  507 ). The constraint system further requires that all rays from surface  509  do not strike first  507  before  506 . Secondly, there is the requirement that rays from  508  avoid hitting surface  506  before hitting  507 . In one embodiment a further constraint can be that surface  507  be conical. The final constraint that is needed is that rays traveling in the mode  2  region must first undergo TIR on  506  and also  507 , while those rays to be refracted at  506  must strike the surface at angles inside the critical angle. The above set of constraints is sufficient to one skilled in the art of nonimaging optics to complete the design. The next step is to decide on the spread angle or angles needed in the peening features. 
     The peen faceting of this optic can be done using the method described above. However, the incoming rays can cross other optical surfaces on their way from the source to the lenticulation and also some other optical surfaces on their way from the lenticulation towards the output pattern. In that case, the methods described above are applied to those ray paths. 
       FIG. 6  shows the same optic as in  FIG. 5 , but now with faceting on its side reflective wall  601 . 
       FIG. 7  shows the same optic as in  FIG. 6 , but now from a different perspective showing the faceting on its bottom central refractive wall  701 . 
       FIG. 8  shows an alternative to the faceting of the refractive surfaces in which the top central refractive wall  801  is facetted. 
     Although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that a variety of alternate and/or equivalent implementations may be substituted for the specific embodiments shown and described without departing from the scope of the present invention. This application is intended to cover any adaptations or variations of the specific embodiments discussed herein. Therefore, it is intended that this invention be limited only by the claims and the equivalents thereof.