Abstract:
High efficiency optical collimator utilizing an open central light flow feature reduces losses while maintaining high intensity. Many degrees of collimation are possible including wide beam angles which traditionally exhibit high back-reflection losses.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority from U.S. Provisional Patent Application Ser. No. 61/896,356, entitled “Open Light Flow Optics”, filed on Oct. 28, 2013. The benefit under 35 USC §119e of the United States provisional application is hereby claimed, and the aforementioned application is hereby incorporated herein by reference. 
     
    
     FEDERALLY SPONSORED RESEARCH 
       [0002]    Not Applicable 
       SEQUENCE LISTING OR PROGRAM 
       [0003]    Not Applicable 
       TECHNICAL FIELD OF THE INVENTION 
       [0004]    The present invention relates generally to optical collimators. More specifically, the present invention relates to a high efficiency optical collimator utilizing an open central light flow feature reduces losses while maintaining high intensity. 
       BACKGROUND OF THE INVENTION 
       [0005]    Antiquated incandescent, halogen cycle, and mercury vapor lighting devices do not provide the color stability, and luminous efficacy to reduce carbon emissions. Solid-state devices such as light emitting diodes produce light at much higher efficacy. Such devices produce light in a Lambertian 180 deg distribution which requires optical control to reduce glare and to increase light on the task or work surface. 
       SUMMARY OF THE INVENTION 
       [0006]    In the past optics for solid-state lighting devices failed to produce narrow-beam collimation at efficiencies &gt;94%, due to central zone Fresnel losses, limited vacuum metalized coating reflectance, or due to internal material absorption losses. Producing high intensity light by means of parabolic and semi-parabolic reflectors results in spill light produced by the light rays which do not strike the top of reflecting surfaces. To collimate more of the light emerging from the central zone a novel light collimator utilizing an inward sloped refractor may pull more of this light laterally for collimation by means of a TIR or totally-internally reflecting lens surface. Although a small percentage of the light which emerges from narrow angles in the central zone is not collimated by the open architecture of the optic, the degree of spill light is reduced, the total material volume of the optic decreased, and the total light transfer efficiency increased. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    The accompanying drawings, which are incorporated herein and form a part of the specification, illustrate the present invention and, together with the description, further serve to explain the principles of the invention and to enable a person skilled in the pertinent art to make and use the invention. 
           [0008]      FIG. 1  illustrates a prior art TIR collimator utilizing inward facing convex lens; 
           [0009]      FIG. 2  illustrates a prior art compact TIR collimator; 
           [0010]      FIG. 3  illustrates an open narrow light flow optic spline design; 
           [0011]      FIG. 4  illustrates an open narrow beam light flow optic; 
           [0012]      FIG. 5  illustrates an open narrow beam light flow optic with secondary refractor; 
           [0013]      FIG. 6  illustrates a high efficiency open medium beam light flow optic; 
           [0014]      FIG. 7  illustrates a high efficiency open wide beam light flow optic; 
           [0015]      FIG. 8  illustrates a narrow, medium, wide light flow optical intensity distribution; 
           [0016]      FIG. 9  illustrates a faceted open light flow narrow beam optic; 
           [0017]      FIG. 10  illustrates a high efficiency wide beam light flow optic lenslet diffuser; 
           [0018]      FIG. 11  illustrates a thermal vector air flow through open light flow optic; 
           [0019]      FIG. 12  illustrates a narrow light flow optic array; 
           [0020]      FIG. 13  illustrates a raytrace of a three-cell narrow light flow optic array with micro-texture pattern; 
           [0021]      FIG. 14  illustrates a three-cell narrow light flow optic array top view of micro texture leaf pattern; and 
           [0022]      FIG. 15  illustrates a three-cell narrow light flow optic array raytrace depicting scatter function of light upon hitting a single micro-texture leaf. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0023]    In the following detailed description of the invention of exemplary embodiments of the invention, reference is made to the accompanying drawings where like numbers represent like elements, which form a part hereof, and in which is shown by way of illustration specific exemplary embodiments disclosing how the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, but other embodiments may be utilized and logical, mechanical, electrical, and other changes may be made without departing from the scope of the present invention. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is defined only by the appended claims. 
         [0024]    In the following description, numerous specific details are set forth to provide a thorough understanding of the invention. However, it is understood that the invention may be practiced without these specific details. In other instances, well-known structures and techniques known to one of ordinary skill in the art have not been shown in detail in order not to obscure the invention. 
         [0025]    Referring to the Figures, it is possible to see the various major elements constituting the apparatus of the present invention. The enclosed Figure drawings are intended to illustrate the open light flow optics. 
         [0026]      FIG. 1  depicts prior art pertaining to the light ray paths emerging from a solid state lighting source  100 , in which the central ray fan  101  passes through a convex lens with radius of curvature facing the light source  100 , resulting in higher collimated light through the exit face  105 . The light ray fan striking the TIR or total internally reflecting surface  102  transforms light which initially passes internally in a lateral direction through the transparent dielectric to a forward direction. The light energy depicted by rays  106  may emerge with collimated direction cosines, or with light divergence as required—produced by control surface  102 . The large thickness of dielectric material  104  requires extended time for molding, and sink marks at the center of exit surface  105  are common. When passing through the thickness of material  104  light absorption is increased, and typical optical light transfer efficiency does not exceed 90% when including Fresnel losses. 
         [0027]      FIG. 2  depicts a prior art compact collimator for a solid-state light source  200 , which transforms the upward light ray energy and lateral light energy into high intensity light. The major light control surfaces which produce transformation on the direction of the light energy emerging from source  200 , include the high conic constant triangular convex surface  204  which works in tandem with the outwardly convex collimator surface  206  to produce collimated light. The light  201  emerging after initial refraction control by the triangular surface  204  passes through dielectric material  205 . The tandem use of lenses  204  and  206  results in a more compact collimator than the  FIG. 1  collimator. The light source  200  produces light in a Lambertian 180 deg distribution which splits into light fans  201  and a lateral fan which collimates upward by means of TIR surface  203 . One of the issues with such compact collimators is the number of sharp flat or semi-flat spline to convex surface intersections. Light energy scatters at these interfaces producing more back-ward direction loss and absorption. 
         [0028]      FIG. 3  displays the light energy control produced by a novel optic with an open light flow feature  304 . An open light flow feature  304  allows light within a restricted distribution zone to pass uninhibited through the core of the collimator. Many solid state light sources are comprised of a violet or blue light emitting diode which pumps a thin phosphor layer to produce white light. Within the central intensity distribution of the light produced by the solid-state light source the CCT or correlated color temperature is cooler in white appearance i.e. bluer than the edges. 
         [0029]    Color mixing features are usually applied to the top surface of TIR collimators to mix the light to a uniform white within the beam and field. Although the light emerging through the open light flow core  304  is not collimated the free flow is restricted to only cover the beam of the light on task surface, whereas in other prior art optics the central zone of light is collimated by a convex collimator as in  FIG. 1 , and then dispersed again by a lenslet diffuser at the top surface. As the percentage of light passing through the core is collimated and then dispersed again after passing through an absorbing transparent dielectric the utility is limited. The light source  300  may produce a Lambertian distribution which is controlled by refractive optical control surface  302 . 
         [0030]    Although the central zone of light from 0-5 deg may pass unimpeded through the open light flow feature  304 , some light from 6-10 deg may inwardly refract by means of surface  303  before undergoing TIR reflection upward by means of TIR surface  301 . The exiting light  305  emerging by means of control via TIR surface  301  may be collimated to a high degree i.e. 5-10 deg beam, or more weakly collimated to a 25-40 deg medium flood. The optical efficiency of the open TIR optic is typically 93-95%, produces collimation similar to a metallic reflector, but has more collimation due to the light control provided by surface  302 . An open light flow optic also has fewer problems with sink marks at the top surface, and can have 2 to 3× faster mold cycle time, thereby reducing the cost. 
         [0031]      FIG. 4  depicts an enhanced open light flow optic with more aggressive material reduction which utilizes a refraction control surface  406  very close to the light source  400 . Light emerges unimpeded through the open light flow feature  407  before passing through air section  404  to exit. Light produced laterally 30-90 deg from light source  400  is controlled and collimated by means of TIR surface  401 . The resulting light beam  403  disperses uniformly to cover the majority of the light energy  402  producing high intensity light. The material volume of the transparent dielectric is 30% that of  FIG. 1 , but produces similar collimation performance and lower cycle time. Transparent materials which may be used include pmma, polycarbonate, silicone and glass. Control surface  405  may also be used to pull light back into the dielectric for collimation. 
         [0032]      FIG. 5  changes the light control profiles of the open light flow optic depicted in  FIG. 4 . Light produced by solid-state light source  500  refracts into a light guide section before control by TIR surface  501 . TIR surface  501  performs two functions both collimated light as well as inwardly directing light for control by means of surface  505 . As can be shown a percentage of light  502  passes through air before re-entering the optic for collimation near the TIR control section  503 . Surface  503  provides further collimation and results in higher intensity of light  506 . Light control surface  505  which provides secondary control upon light directed upward and inward by means of TIR surface  501 , may be a straight section, or may have more complex curvature or discrete sections of variable slope. The open retains the features of open light flow architecture including high efficiency &gt;93%, and substantial collimation efficiency or candela/lumen while using less material. 
         [0033]      FIG. 6  shows a medium beam open light flow optic which produces a 25 deg beam at 94% efficiency. The light source  600  is first collimated laterally by refractor surface  604  before collimation by means of TIR surface  601  with a secondary TIR spline  602  controlling the light. The open section  605  allows light to pass unimpeded by Fresnel back reflection or by lenslet diffusers. Most 25-35 deg optics utilize aggressive lenslet diffusers to homogenize and spread out the light from the source which at best can only achieve 87-90 percent light transfer efficiency. The two resultant light beams  606  and  603  which emerge by first passing through open light flow  605  and the second by means of a TIR/refractor combination  604 ,  601 ,  602  produce pleasing Gaussian intensity distribution free of striations and artifacts while using far less dielectric material. 
         [0034]      FIG. 7  shows a 50 deg open light flow optical collimator which transforms light from a Lambertian distribution source  700  into a wide flood at high efficiency &gt;94%. The open light flow (OLF) optic utilizes the following light control surface to accomplish wide flood collimation including a refractor surface  704  which transforms light within the 50-90 deg zones into laterally collimated light which strikes TIR control surface  701 . An intermediate caustic is produced near zone  702  which represents in some features a CEC or confocal elliptic concentrator with a 45 deg tilt from a reference ray emerging upward from source  700  with a directional vector of xyz [0,0,1]. Light flow through the open air feature  705  continues unimpeded by a convex collimator+lossy dielectric+lenslet diffuser. The distribution depicted by the splitting of light ray fans at  703  allows for the production of flatter field super Gaussian beams to light with more spill, field light with depressed central intensity i.e. “bat-wing” distribution as required by lighting application. 
         [0035]    The primary novel features of the open light flow optic include lower material volume, lower cycle time, and higher efficiency than most prior art optics. 
         [0036]      FIG. 8  shows the light distribution charts of the optics embodiments comprising  FIGS. 5 ,  6 ,  7 . Light distribution can be characterized by the beam and the field. The beam of a light is the full distribution angle at which the light intensity is 50% of the peak. The field is the full distribution angle at which the intensity is 10% of the peak. The ratio of the beam to the field represents the edge of the light distribution. With unity beam/field representing a perfectly sharp projector beam, and a ratio of 0.25 a distribution with more spill light and soft beam to field transition. The light distributions depicted in the charts in  FIG. 8  include  800  the beam of narrow optic  FIG. 5  with a distribution of 10 deg,  801  the beam distribution of 25 deg from the optical structure of the open light flow optic shown in  FIGS. 6 and 802  the beam distribution of the 50 deg optic shown in  FIG. 7 . The field distributions of the three classes of optics are 20 deg  803  narrow beam optic from  FIG. 5 , 50 deg the field of medium optic  FIGS. 6 , and 75 deg the field of the novel wide flood optic disclosed in  FIG. 7 . The ratio of beam/field of the three optics are 0.5, 0.5, and 0.75 respectively for the narrow, medium, and wide. 
         [0037]      FIG. 9  shows the faceted modifiers which may be applied to the open light flow optical architectures embodied in  FIGS. 4 and 5 , or the medium and wide optics of  FIGS. 6 and 7  as well. The light source  900  is converted by means of refractor surface  901 , TIR surface  902  and may be modified by facet surface  904 . The facets cut into the smooth spline revolved structure and the flat faces produce micro-aberrations into the collimation function of the classical confocal parabolic concentrator to produce higher homogeneity in the field. The  905  open light flow feature allows the light fields depicted by  906  to pass unperturbed and when combined with the controlled light fields  903  produces a high uniformity beam without the lossy flat exit face lenslets of prior designs. 
         [0038]      FIG. 10  depicts the wide flood open light flow optic of  FIG. 7  with the addition of a micro-lenslet array applied to the flat exit surface  1003 . Solid-state light source  1000  produces light which passes through the transparent section of the collimator where it is directed upward by means of surface  1001 . A caustic formed at zone  1002  become a secondary source which is homogenized by means of an array of small lenslets  1003 . Lenslets have convex radius of curvature relative to the flat face of the optic to distort the light fields impinging on the features thereby creating higher uniformity light  1005  which mixes with the light  1004  which passed through the optic. The advantage of partial lenslet diffusion is the net efficiency produced as the lenslets required are smaller resulting in less back-ward light reflection. 
         [0039]      FIG. 11  depicts the air flow  1103  which passes through the open light flow feature  1104  before exiting through outlets  1105  on either side of the light emitting diode (LED). The TIR surface  1102  collimates light from the light source  1101 , which is affixed to a metal core printed circuit board  1100 . The magnitude of the air flow vectors represents thermal flux/unit area. Any air flow, although restricted is good for cooling the solid-state lighting source. The combination of not just air flow, but open light flow and associated design features results in a higher efficiency optic &gt;95% typical with this embodiment. 
         [0040]      FIG. 12  shows an array of narrow-beam open light flow optics  1202 ,  1203 . The 7-cell array allows for illumination multiplexing of the scale of light from 100 lumens to 100 klumens. The light emerging from light sources  1200  are refracted by surface  1201 , which conditions more of the light which would be pass uncontrolled by a simple aluminum reflector of limited height. The resulting light field  1204  is a 10 deg beam with high efficiency &gt;93%, with far less material volume than the solid prior art tulip design of  FIG. 1 . Mold cycle times of the  FIG. 12  array are lower, and the material cost reduced. 
         [0041]      FIG. 13  represents the light flow ray paths through a three-cell open light flow (OLF) optic in which the three cells are joined in the center to make the overall cluster smaller in diameter.  1300  represents the solid-state light source such as a white LED or light emitting diode.  1301  represents the curvature of the TIR or total internally reflecting wall which collimates the light which hits the dielectric/air interface.  1302  indicates the open air flow channel which passes through the center of each optic cell.  1303  points to a micro-scattering pattern which perturbs the ray-path to mix and to homogenize brighter spots of light into a smooth pattern.  1304  points to a bundle of un-perturbed rays which have passed through the optic without hitting a scatter-pattern, and remain highly collimated. Ray  1305  is a ray which has been perturbed or bent by a micro-scattering pattern on the top surface of the optic. 
         [0042]      FIG. 14  depicts the top surface of the three-cell cluster which clearly shows the open air flow light paths through the center of each cell ( 1400 ). This is the channel through which both air and light may flow without back-reflection by means of Fresnel scatter.  1401  indicates the small spaces on the upper surface of the optic which do not scatter light.  1402  indicates a micro-scattering pattern or “leaf” which takes collimated light which hits the pattern area and then expands the flow into a bloom of light thereby producing higher homogenization. The combination of the scatter patterns with areas of no micro-texture results in a fine-tuning of the distribution of the light at the beam and field. 
         [0043]      FIG. 15   1500  is the TIR wall of the optic which produces collimation of the light which strikes upon it.  1501  is a magnified view of the flat areas on the top surface of the optic which have high polish and dielectric/air transfer efficiency.  1502  indicates a magnified view of one of the many micro-scattering “leaves” or patterns of scattering features. Finally,  1503  is a ray which has been perturbed by means of a micro-scattering leaf. Although the patterns shown are on the top-surface of the optic on a flat surface this is not necessary for the invention to function. The top surface may have both concave or convex curvature and incorporate micro-scattering leaves. The primary advantage of utilizing a pattern of micro-scattering leaves is higher efficiency, approximately 4% higher than what would be achieved when using an array of micro-lenslets over the entire surface to homogenize the light. 
         [0044]    Thus, it is appreciated that the optimum dimensional relationships for the parts of the invention, to include variation in size, materials, shape, form, function, and manner of operation, assembly and use, are deemed readily apparent and obvious to one of ordinary skill in the art, and all equivalent relationships to those illustrated in the drawings and described in the above description are intended to be encompassed by the present invention. 
         [0045]    Furthermore, other areas of art may benefit from this method and adjustments to the design are anticipated. Thus, the scope of the invention should be determined by the appended claims and their legal equivalents, rather than by the examples given.