TOTAL INTERNAL REFLECTION LENS HAVING A TAPERED SIDEWALL ENTRY AND A CONCAVE SPHERICAL EXIT BOUNDED BY A COMPOUND PARABOLIC CONCENTRATOR OUTER SURFACE TO LESSEN GLARE WHILE MAINTAINING COLOR MIXING AND BEAM CONTROL OF AN LED LIGHT SOURCE

Abstract

A multi-color LED illumination device and specifically a lens comprising a cylindrical opening extending into the lens from a light entry region at which one or more LEDs are configured. A concave spherical surface extends across the entirety of the light exit region of the lens, and a TIR outer surface shaped as a CPC extends between the light entry region and the light exit region. There are various diffusion surfaces placed on the sidewall surface of the cylindrical opening, as well as its upper planar surface and, depending on whether glare control is not needed, the exit surface of the lens. Lunes can also be configured on the sidewall surfaces of the cylindrical opening and if lessening glare is needed, also on the TIR outer reflective surface. The combination of lunes, diffusion elements, and the overall configuration of the lens provides improved color mixing and output brightness according to one embodiment. According to another embodiment, diffusion elements are manufactured and possibly increased on only select surfaces but not on the light exit region in order to lessen glare. Three light interactions in a first portion of light and two interactions in a second portion of light can improve color mixing and beam control. Those interactions includes two refractions either with an intermediate reflection or not, all of which are necessary to achieve the improved performance of the multi-color LED illumination device and lens hereof.

Claims

1. A lens for receiving light from an LED, comprising: a tapered cylindrical opening having a tapered sidewall surface extending into the lens from a light entry region configured for receiving the entirety of light from the LED; a concave spherical surface extending across the entirety of a light exit region of the lens; and a total internal reflective (TIR) outer surface shaped as a compound parabolic concentrator (CPC) extending between the light entry region and the light exit region.

2. The lens as recited in claim 1, wherein the tapered cylindrical opening extends partially into the lens from the light entry region and is centered along a central axis of the lens.

3. The lens as recited in claim 2, wherein the tapered sidewall surface is configured about the central axis a decreasing radial distance from the central axis from the light entry region toward the light exit region.

4. The lens as recited in claim 3, wherein the decreasing radial distance is along an axis that is 4-10 degrees relative to the central axis.

5. The lens as recited in claim 1, wherein the tapered sidewall surface extends from an opening formed by the tapered cylindrical opening at the light entry region to an upper plane that is parallel to a base plane on which at least one light emitting diode is configured.

6. The lens as recited in claim 5, wherein the tapered sidewall surface further comprises: a plurality of planar lunes extending radially inward toward the central axis from the opening to the upper plane and all of which are of equal width and all of which are of equal length, said equal length is from the opening to the upper plane; and a manufactured diffusion surface on each of the plurality of lunes.

7. The lens as recited in claim 5, wherein the upper plane comprises a circular surface on the upper plane facing toward the light entry region and having a manufactured diffusion on said circular surface.

8. The lens as recited in claim 6, wherein the TIR outer surface comprises a second plurality of planar lunes of equal width and equal length, said equal length of the second plurality of lunes is from the opening to the concave spherical surface and the second plurality of lunes outnumbers the plurality of lunes by a ratio of between 1.5 to 1 to 2.5 to 1.

9. The lens as recited in claim 1, wherein the concave spherical surface comprises a substantially smooth surface absent any manufactured diffusion on said smooth surface.

10. The lens as recited in claim 1 is made of a unibody construction of transparent material having a refractive index greater than air and wherein the unibody is configured between surfaces formed by tapered sidewalls, the concave spherical surface, and the TIR outer surface shaped as a CPC.

11. The lens as recited in claim 2, wherein the TIR outer surface is symmetrical about the central axis, and the concave spherical surface is also symmetrical about the central axis.

12. The lens as recited in claim 1, wherein the diameter of the concave spherical surface is between 2 to 2.5 times the diameter of the opening of the tapered cylindrical opening at the light entry region.

13. An illumination device, comprising: a unibody lens having a reflective outer surface shaped as a compound parabolic concentrator (CPC) around a central axis between an diffusion manufactured light entry surface and a non-diffusion manufactured spherical concave light exit surface; a plurality of light emitting diodes proximate to the light entry surface and spaced from each other along a base plane perpendicular to the central axis; a first plurality of lunes upon the light entry surface, each having an elongated planar surface extending a decreasing distance from the central axis from the base plane to an upper plane that is parallel to the base plane; and a second plurality of lunes upon the reflective outer surface, each having a second elongated planar surface extending an increasing distance from the central axis from the base plane to the spherical concave exit surface.

14. The illumination device as recited in claim 13, wherein the spherical concave exit surface extends around the central axis an entire distance to the reflective outer surface.

15. The illumination device as recited in claim 13, wherein the lens is a light transparent lens, and the second plurality of lunes comprises reflective planar surfaces that reflect all light from the light emitting diodes that is directed to the reflective outer surface.

16. The illumination device as recited in claim 13, wherein the spherical concave exit surface is operable to receive all light from the light emitting diodes that is directed to and reflected from the reflective outer surface.

17. The illumination device as recited in claim 13, wherein the decreasing distance extends along a planar vector that is 4-10 degrees from the central axis.

18. The illumination device as recited in claim 14, wherein the ratio between a number of second plurality of lunes and a number of first plurality of lunes is between 1.5 to 1 and 2.5 to 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Other objects and advantages of the invention will become apparent upon reading the following detailed description and upon reference to the accompanying drawings.

[0039] FIG. 1 is a plan view of a compound parabolic shape relative to a parabolic shape;

[0040] FIG. 2 is a plan view of a parabolic shape having a wider radius from a central axis than the compound parabolic shape;

[0041] FIG. 3 is a plan view of a compound parabolic concentrator typically used to accept and concentrate solar rays onto a focal point;

[0042] FIG. 4 is a side cross sectional view of a lens mounted within a reflective housing to achieve total internal reflection;

[0043] FIG. 5 is a view along plane 5 of FIG. 4 showing an array of LEDs;

[0044] FIG. 6 is a side cross sectional view of a TIR lens absent a reflective housing to achieve total internal reflection using only one light interaction;

[0045] FIG. 7 is a side cross sectional view of a TIR lens absent a reflective housing to achieve total internal reflecting using no more than two light interactions;

[0046] FIG. 8A is a side cross sectional view a lens with a TIR outer surface shaped as a CPC and having up to three light interactions to achieve improved output collimation and color mixing according to one embodiment of the present invention;

[0047] FIG. 8B is a blow up cross sectional view of the diffusion surfaces;

[0048] FIG. 9A is a view along plane 9 of FIG. 9 showing a cylindrical opening having a plurality of lunes arranged along the sidewall surface of the cylindrical opening;

[0049] FIG. 9B is a blow up cross sectional view of the two lunes of a TIR lens shaped with a CPC;

[0050] FIG. 10A is a side cross sectional view of the lens of FIG. 8A according to an alternative embodiment in which the concave light exit region does not comprise a diffusion surface and the light entry region comprises diffusion surfaces and a tapered sidewall surface to minimize glare;

[0051] FIG. 10B is a blow up cross sectional view of the diffusion surfaces configured on the light entry region of the lens according to the embodiment of FIG. 10A; and

[0052] FIG. 11 is a cross-section view along plane 11 of FIG. 10A showing the reflective TIR outer surface of the lens having a plurality of lunes, each having a width that extends around the circumference of the outer surface and a length extending from the light entry region to the light exit region.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0053] FIG. 8A illustrates lens 80 filled with material 82, e.g., an injection molded light transparent material. Material 82 is bound between light entry region 84, light exit region 86, and TIR outer surface 88, which is shaped as a CPC. TIR outer surface 88 has a smaller exit region then a parabolic TIR, shown in dashed line 90. Moreover, exit region 86 comprises concave spherical surface 94, instead of most conventional parabolic lenses having a flat surface, shown in dashed line 96. Thus, FIG. 8A illustrates a comparison between a conventional parabolic lens 91 and the present lens 80. Present lens 80 is not only shaped as a CPC, but also is more compact in its configuration, being less than 2.5 inches in diameter for exit region 86, 1 inch in diameter for entry region 84, and no more than 1.4 inches in height from the entry region to the exit region. The entry region is defined as a planar base on which the LEDs 100 reside. The overall maximum height of the compact PAR dimension of the present invention is 1.4 inches from the planar base to the outer extents of the TIR reflective surface 88 at which it joins the concave spherical surface 94.

[0054] Of import, the compact PAR configuration of lens 80, which is shaped as a CPC, is beneficial over the conventional parabolic lens. Conventional lens 91 can receive light passing through a sidewall surface 102 near the light entry region 84, such sidewall surface constitutes the sidewall surface of a cylindrical opening, also having an upper planar surface 104. The dashed line indicates refraction at angles φ.sub.PA1 and φ.sub.PM2 at the plastic-to-air interface of the parabolic lens. Next, a reflection occurs at the TIR external surface of lens 91, shown at angles φ.sub.R3 and φ.sub.R4, whereby the reflected light is then refracted at the exit surface of lens 91 by the interaction of φ.sub.PM2 to φ.sub.PA2. The resulting exiting light ray or beam may not be collimated. Thus, it is desirable to form a collimated lens, which can be achieved by strict adherence to the configuration of lens 80, with a cylindrical opening that forms sidewall surface 102 and upper planar surface 104, along with concave spherical surface 94, where surface 94 must extend across the entirety of the light exit region from the central axis about which lens 80 is symmetrical to external surface 88.

[0055] FIG. 8A illustrates that any beam that strikes sidewall surface 102 must go through three light interactions. For example, beam 106 goes through a refraction φ.sub.A1/φ.sub.M1 at sidewall surface 102 to a reflection φ.sub.R1/φ.sub.R2, to another refraction φ.sub.M2/φ.sub.A2 on surface 94. Beam 108 also goes through three interactions. The first interaction is a refraction, followed by a reflection, ending with another refraction. Thus, every beam that enters the sidewall surface near the beam entry portion goes through the sequence of refraction, reflection, and refraction, finally exiting the light exit region as a collimated light beam, which is not achievable in conventional lens 91. For brevity and clarity of the drawings in showing the various ray paths, which can exceed several hundred if not thousands, only two are shown for lens 80 entering the sidewall surfaces. Moreover, so as not to obscure the ray path line, material 82 is not shown in cross-hatch; however, it is understood that in the region between the cylindrical opening near the light entry region to the concave spherical surface of the light exit region, lens 80 is filled with unibody material 82, which is contiguous and non-interrupted, such as injection molding.

[0056] In addition to transmitting a first portion of light from LEDs 100 through air attributable to the cylindrical opening where it impinges upon sidewall surface 102, a second portion of light can be sent through air of the cylindrical opening where it impinges upon planar upper surface 104. The first portion of light is first refracted at surface 102, then reflected at surface 88, then second refracted at surface 94. The second portion of light 110 is third refracted φ.sub.A3/φ.sub.M3, if it impinges upon the planar upper surface at a non-perpendicular angle, where it is later fourth refracted φ.sub.M4/φ.sub.A4 on surface 94.

[0057] The first portion of light from the outer radial region of the LED output is shown collimated as it exists as beam 106. The first portion, however, passes through diffusion surfaces on the sidewall surface 102 to scatter, or mix the light output to achieve both angular and linear uniformity of the output. Such diffused, collimated output is purposely placed on the outer radial region to surround the non-collimated inner radial region of the LED output to achieve color mixing at the near and far field. The improved color mixing is due to the unique configuration of the cylindrical opening of the light entry region to the concave spherical surface of the light exit region, bound by a reflective outer surface being CPC-shaped to achieve an overall compact dimension of a PAR lamp.

[0058] On sidewall surface 102, planar upper surface 104, and exit surface 94 of lens 80 is a diffuser surface 112, shown in FIG. 8B. Diffuser surface 112 scatters light from the various LED sources, resulting in a wider beam angle. In general, diffuser surface 112 is preferably configured with some combination of differently textured surfaces and/or patterns 114, so that light 116 entering the surface will get scattered or diffused, shown by light 118. For example, lensets that perform the scattering can be rectangular or square shaped domes, and may be small enough so that the curvature of the lensets is defined by the radius of the arcs that create the lensets.

[0059] FIG. 9A illustrates a plurality of lunes 120, when viewed from the base of lens 80 along plane 9-9 of FIG. 8A. Peering into the cylindrical opening, a series of substantially flat or planar lunes 120 extend along sidewall surface 102 spaced equal distance from central axis 122. Shown are eight lunes, and preferably, the improved lens design hereof uses between eight to no more than 20 lunes to enhance color mixing in the inner cylindrical opening into which the LED output enters. Each lune has an elongated surface that extends the entire length of the sidewall surface from the planar base on which LEDs 100 reside to upper planar surface 104. The elongated surface of lunes 120 extend perpendicular from the base plane, spaced equal distance along central axis 122 to upper plane 104 that is parallel to the base plane. The lunes are simply planar cutouts from lens 80, formed as part of the injection molding process when the fill material is applied to the mold, with the mold outer regions within the cylindrical opening of the lens having a plurality of circumferentially configured planar surfaces.

[0060] FIG. 9B is an expanded view of a region showing two lunes 120a/120b, and provides a general description as to why such surfaces are defined as lunes. The lune surfaces are formed as a concave-convex area, shown in cross hatch, bounded by two circular arcs. The lune surfaces 120a/120b are formed therefrom.

[0061] Turning now to FIGS. 10A, 10B and 11, an alternative embodiment for a lens is shown. Contrary to the lens shown in FIGS. 8A and 8B, the lens in FIGS. 10A and 10B is a lens that emits a lower glare from the light exit region 86, and specifically the concave spherical surface 94 that extends across the entirety of the light exit region 86. Since lens 80 shown in FIG. 10A is one having a TIR outer surface and shaped as a CPC, many like numerical identifiers exist between FIG. 10A and FIG. 8A describing a TIR lens 80, albeit some of the surfaces of lens 80 in FIG. 10A are different from the surfaces of lens 80 in FIG. 8A.

[0062] For example, the concave spherical surface 94 of the light exit region 86 in the alternative embodiment shown in FIG. 10A does not have any diffusion treatment or any diffusion manufactured thereon. Accordingly, FIG. 10B shows a diffusion surface of textured patterns 114 so that light 116 entering the surface will get scattered or diffused, shown by light 118. Importantly, diffuser surface 112 exists only on the light entry region, and specifically on the tapered sidewall surface 102 and the upper planar surface 104. While similar numerals are shown for the sidewall surface 102 and the upper planar surface 104 of the cylindrical opening, the alternative embodiment of FIG. 10A indicates nonetheless a difference from the sidewall surface 102 and the upper planar surface 104 in FIG. 8A. Specifically, the sidewall surface 102 in FIG. 10A is tapered and not perpendicular to the base plane on which the LEDs 100 extend, while the sidewall surface 102 in FIG. 8A is a straight sidewall surface that is perpendicular to the base plane on which the LEDs 100 extend. More diffusion or texture can be applied to the tapered sidewall surface 102 than to the straight sidewall surface 102.

[0063] FIGS. 10A and 10B do not illustrate any diffuser surface on the light exit region 86, and specifically the concave spherical surface 94 of the light exit region 86. All diffusion is placed on the tapered sidewall surface 102 and the upper planar surface 104, of the light entry region. By placing the diffuser surface only on the light entry region, and tapering the sidewall of the tapered cylindrical opening, color mixing can be maintained somewhat close to that of the embodiment shown in FIG. 8A. However, by removing any diffuser surface from the light exit region, a lower glare can be achieved.

[0064] It is typically recognized that there are at least two types of glare: direct or indirect. Direct glare is the glare that appears when a person looks straight onto the illumination device source, or the LED behind the secondary optic lens. Indirect glare is that which occurs from illumination output reflected off surfaces in the field of view. Those surfaces can be within the lens itself or outside the lens, such as on an object distal from the illumination device (e.g., a desk, computer screen, etc).

[0065] Regardless of the type of glare, glare in general can cause significant problems such as blurred images, eye strain, or even headaches. Typical ways in which to deal with glare and the visual discomforts associated therewith, are anti-glare structures. Popular anti-glare structures include diffusive films and reflective screens. Anti-glare structures are oftentimes placed on the illumination device in an attempt to match and offset any reflection that might arise from the illumination output. It is difficult at best to perform such matching and, if done successfully results in a complicated design and manufacturing of the matching and offsetting screens that almost certainly results in poor light efficiency output from the illumination device.

[0066] The problems of glare and any failed attempts to offset that glare by anti-glare reflective filtering, screening, etc. are eliminated entirely by ensuring that no such anti-glare screening, filtering or offsetting occurs on the light exit region. Such problems are therefore solved by removing any diffusive surface from the concave spherical surface 94 and instead tapering the sidewall surface 102 to effectuate diffusion closer to the light source, or LEDs 100. This allows the natural refraction and reflection within the lens to cause any necessary offset or matching to occur within the lens and not to add any additional glare by attempting a diffusive surface on the light exit region 86.

[0067] Minimizing glare in ceiling-mounted light fixtures, and specifically PAR downlights that use LEDs not only eliminates glare zones, but according to the anti-glare alternative embodiment shown in FIGS. 10A-11, no offset, reverse compensation, glare-tuning, matching, or any other expensive and difficult to manufacture exit diffuser surfaces are needed on the concave spherical surface 94 of the exit region 86. All glare control and glare-zone elimination occurs at the light entry region, and specifically through use of a tapered cylindrical opening and the various refraction and reflections that occur within the CPC shape itself.

[0068] As shown in FIG. 10A, LEDs 100 are moved closer to the upper planar surface 104, as shown in dashed line, and the opening 130 of the tapered cylindrical opening can be made of a larger diameter, possibly more than one inch so that the diameter of the concave spherical surface 94 relative to the central axis 132 is between 2-2.5 times the diameter of the opening 130, also relative to the central axis 132. Accordingly, if the diameter of opening 130 is greater than one inch, and the diameter of the concave spherical surface 94 diameter is 2.5 inches, the ratio would be less than 2.5. The amount of taper of the sidewall surface 102 can be described as an angle Ø relative to the central axis 132. Accordingly, angle Ø of the tapered sidewall surface relative to the central axis 132 can range between 4° to 10°. The amount of taper is primarily determined by the specific beam angle requirement. Also, the amount of diffusion manufactured on the tapered sidewall surface 102 and the upper planar surface 104 of the light entry region is dependent upon the amount of color mixing and beam uniformity needed.

[0069] Like the embodiment shown in FIGS. 8A-9B, the low glare embodiment shown in FIGS. 10A-11 also include a first plurality of lunes on the sidewall surface 102. The only difference between the two different embodiments is that the lunes on the sidewall surface 102 in FIG. 10A are tapered planar surfaces and the first plurality of lunes on the embodiment in FIG. 8A are not tapered and extend perpendicular to the base plane. Specifically, the tapered first plurality of planar lunes extend as part of the tapered sidewall surface radially inward toward the central axis from the opening 130 to the upper plane 104. All of the first plurality of lunes are of equal length and all of the first plurality of planar lunes are ones that extend from the opening to the upper plane. Each of the first plurality of tapered lunes has a manufactured diffusion surface thereon.

[0070] While the TIR reflective surface in the embodiment of FIG. 8A, shown as numeral 88 does not have a second plurality of planar lunes, the embodiment in FIGS. 10A-11 for low glare configuration does. As shown in the cross-section 11-11 of the outer reflective surface 88 in the second embodiment, a second plurality of planar lunes 140 are arranged upon the reflective outer surface 88. Each of the second plurality of lunes 140 has a second elongated planar surface extending an increasing distance from the central axis 132 from the opening 130 of the base plane on which LEDs 100 exist to the spherical concave exit surface 94. Each of the second plurality of lunes are compound parabolic in shape to conform to the CPC outer surface, yet having a planar shape bent as it extends from the light entry region to the light exit region. Preferably, the ratio between the number of second plurality of lunes and the number of first plurality of lunes is between 1.5:1 and 2.5:1. Thus, if the first plurality of lunes is between 8 and 20, the second plurality of lunes is between 12-50. As shown in FIG. 11, the second plurality of lunes 140 preferably exists on the inside surface of the outer reflective surface 88. The second plurality of lunes 140, are therefore reflective planar surfaces that reflect all light that are received on the lunes back into the lens 80 and out through the light exit surface 86. The second plurality of lunes therefore achieves TIR functionality, but within a CPC configuration.

[0071] It will be appreciated to those skilled in the art having the benefit of this disclosure that this invention is believed to provide an improved lens configuration that achieves improved color mixing. The improved color mixing occurs by treating a collimated outer radial region of the LED module output, while maintaining non-collimation on an inner radial region of the LED output. More than three light interactions are needed to achieve the improved color mixing, with both improved spatial and angular uniformity. Improved glare control is also achieved using a taped diffusion-manufactured sidewall surface of a light entry region without any diffusion manufactured on the concave spherical surface of the light exit region. Further modifications and alternative embodiments of various aspects of the invention will be apparent to those skilled in the art in view of this description. It is intended that the following claims be interpreted to embrace all such modifications and changes. Accordingly, the specification and drawings are to be regarded in an illustrative, rather than a restrictive, sense.