Optical arrangement for a solid-state lighting system

An optical arrangement and a solid-state lighting system comprise an optical element having at least one lens where the lens has a faceted surface defining a plurality of facets. An LED light source comprises a plurality of LED chips and is arranged relative to the faceted surface such that the plurality of facets are disposed asymmetrically relative to the plurality of chips such that mixing of light from the plurality of LED chips occurs via the surface.

BACKGROUND

Light emitting diode (LED) lighting systems and light fixtures are becoming more prevalent and may be used as replacements for existing lighting systems and light fixtures. LEDs are an example of solid state lighting and have advantages over traditional lighting solutions such as incandescent and fluorescent lighting because they use less energy, are more durable, operate longer, can be combined in red-blue-green arrays that can be controlled to deliver virtually any color light, and contain no lead or mercury.

In many applications, one or more LED dies or chips are mounted within an LED package or an LED module, which may make up part of a lighting fixture which includes one or more power supplies to power the LEDs. Some lighting fixtures include multiple LED modules. A module may include, for example, a packaging material with metal leads (to the LED dies from outside circuits), a protective housing for the LED dies, a heat sink, or a combination of such elements. An LED fixture may be made using the LED modules with a form factor that allows it to be used as a bulb, lamp or the like to replace a standard threaded incandescent bulb, fluorescent or halogen lamps or the like. LED fixtures may include some type of optical elements external to the LED modules themselves.

SUMMARY

An optical arrangement for a solid-state lighting system comprises an optical element comprising at least one lens, the lens having a faceted surface defining a plurality of facets. An LED light source comprises a plurality of LED chips and is arranged relative to the faceted surface such that the plurality of facets are disposed asymmetrically relative to the plurality of chips such that light from the plurality of LED chips is mixed by the faceted surface.

The optical element may comprise a TIR optical element. The LED light source may comprise four LED chips. The faceted surface may comprise six facets. At least one of the plurality of LED chips may comprise a red-emitting LED. At least one of the plurality of LED chips may comprise a blue-shifted yellow LED device. The blue-shifted yellow LED device may be packaged with a local phosphor. The blue-shifted yellow LED device plus the red-emitting LED may create substantially white light. A plurality of LED light sources may be provided where the TIR optical element comprises a plurality of lenses where each one of the plurality of lenses corresponds to one of the plurality of LED light sources. An exit surface may comprise a flat substrate with a microlens. An entrance surface may be associated with the at least one lens where the entrance surface comprises a second plurality of facets. The facets may be planar surfaces. A first light from one of the plurality of LED chips may pass through one of the plurality of facets and a second light from another one of the plurality of LED chips may pass through the same facet. The first light may be a first color and the second light may be a second color. A first amount of the first light may pass through a facet and a second amount of the second light may pass through the same facet where the first amount is less than the second amount. The LED light source may comprise a plurality of light sources arranged in an array where each of said light sources comprises a plurality of LED chips wherein the plurality of LED chips comprises a first type of chip for emitting a first color light and a second type of chip for emitting a second color of light. A plurality of lenses may be provided where one of the plurality of lenses corresponds to each one of the plurality of light sources. An LED lamp comprising the optical element is also provided. A connector of a standard, MR-16 lamp may be provided. An interior surface of the optical element that surrounds the LED light source may be faceted.

An LED lighting system comprises an optical element having at least one lens, the lens having a faceted entrance surface defining a plurality of facets. An LED light source comprises a plurality of LED chips, the LED light source being arranged relative to the faceted surface such that the plurality of facets are disposed asymmetrically relative to the plurality of LED chips such that light from the plurality of LED chips is mixed.

A method of assembling a lighting system comprises arranging a plurality of LED light sources in an array within a housing where each light source comprises a plurality of LED chips; placing at least one optical element to receive and direct light from the plurality of LED light sources where the optical element comprises a plurality of lenses and each of the plurality of lenses having a faceted surface defining a plurality of facets; and arranging the at least one optical element relative to the array such that the plurality of facets of each of the plurality of lenses are disposed asymmetrically relative to the plurality of LED chips of each of the plurality of LED light sources.

DETAILED DESCRIPTION

Unless otherwise expressly stated, comparative, quantitative terms such as “less” and “greater”, are intended to encompass the concept of equality. As an example, “less” can mean not only “less” in the strictest mathematical sense, but also, “less than or equal to.”

An optical element that exhibits total internal reflection (TIR), a “TIR optic” or “TIR optical element,” may be used in solid-state lighting systems that require directional focus or collimation. A TIR optical element is essentially a lens made of transparent material such as polycarbonate, acrylic, glass or the like designed in such a way that light, once having entered into the transparent media, encounters the side walls of the lens at angles greater than the critical angle, resulting in total internal reflection. Thus, a TIR optic can also serve as a reflector. Typical TIR optical elements include one or more entry surfaces, one or more exit surfaces, and a sidewall or outer surface that internally reflects light. The sidewall is shaped so that light rays hitting at various angles on the sidewall reflect at an angle greater than the critical angle. A TIR optic outer surface may have various shapes including conic, angled, arced, spherical, curved as well as segmented shapes.

Shown herein are example embodiments of LED solid-state replacement lamps using an optical arrangement as described above. These detailed embodiments are provided as examples only and a lighting fixture, luminaire, lighting system, bulb or lamp that implements an embodiment of the invention can take many forms and be made in many ways. An embodiment of the invention can be developed based on the disclosure herein for many types of directional solid-state lighting.

Referring toFIGS. 1 and 2an embodiment of an LED-based, solid-state replacement for a standard, MR16 halogen lamp is shown. Solid state lamp10includes TIR optical element12, which has three lobes12a,12b,12c. Each lobe corresponds to an LED light source24and each light source in this example embodiment includes four LED chips. Lamp10also includes a heat sink14that may be made of aluminum or other thermally conductive material and may comprise a plurality of fins14afor dissipating heat to the ambient environment.

A power supply18is provided that includes electrical components to provide the proper voltage and current to the LED light sources24within lamp10. The power supply18may be contained in a housing that is connected to the heat sink14. Connection pins20provide a standard connection to power rails, which may be AC or DC supply rails. The lamp may also be used as a solid-state replacement for a standard, PAR type incandescent bulb. In such an application the lamp would include an Edison type base in place of pins20. Other connectors may be used to provide power to the lamp in other applications

A diffuse, white, highly reflective secondary reflector22may be provided within the heat sink structure14of lamp10, so that the secondary reflector is substantially adjacent to but spaced a small airgap apart from the sidewalls of TIR optical element12. Secondary reflector22is molded or thermoformed into the desired shape to fit together with the heat sink portion of the lamp and TIR optical element12. The secondary reflector can be made of many different materials, including materials that are made reflective by application of a powder coating, reflective paint, or the like. The air gap between the TIR optical element12and the highly reflective secondary reflector serves to insure that the internal reflectivity of the optical element is not interfered with by the secondary reflector. However, light that escapes by transmission from the TIR optical element12is efficiently reflected back into the TIR optical element for another opportunity to eventually be transmitted or reflected from the exit surface38of the optical element.

A mounting surface21is provided inside the lamp10for mounting the LED light sources24. In the illustrated embodiment three LED light sources24are arranged in an array so that each light source corresponds to a lobe12a,12b, and12cof the optical element12. A recess or slot26is provided in the mounting surface21and a corresponding recess or slot27is formed in the base29of heat sink14. The slots26and27are aligned when the mounting surface21is mounted to the base of the heat sink14. The recesses or slots26and27receive a mating projection35formed on the optical element12to seat the TIR optical element12, for aligning the LED light sources24and the TIR optical element12. Alternatively, a plurality of projections29may be provided, for example around the periphery of the optical element12, that engage a plurality of mating recesses or slots formed on the mounting surface21and/or heat sink14as shown inFIG. 12. Secondary reflector22includes a hole or holes23through which light passes from LED light sources24into the TIR optical element12, and through which the projection passes so that the projections29and/or35can seat properly with the recesses of the mounting surface21and/or the heat sink14. A retention ring, not shown, may be used to clamp the various portions of the lamp together and hold the optical element12in the housing.

Various arrangements and types of LED light sources24emitting various colors of light can be used with embodiments of the invention. The embodiment of the LED light source24shown inFIG. 7comprises four LED chips or dies (hereinafter “chips”)31a,31b,31cand31dpackaged on a submount or mounting surface21with a lens (not shown). At least one of the LED chips, for example LED chip31a, may be a red-emitting LED, and at least one of other LED chips, for example LED chip31b, may be a blue-shifted yellow LED device. The blue-shifted yellow LED device may be packaged with a local phosphor to form blue-shifted yellow LED devices. Such a blue-shifted yellow plus red (BSY+R) system is used to create substantially white light. In some embodiments, the red LEDs, when illuminated, emit light having dominant wavelength from 605 to 630 nm. In some embodiments, the LED chips for the BSY devices emit blue light having a dominant wavelength from 440 to 480 nm. The phosphor packaged with the blue LEDs when excited by the impinging blue light, may emit light having a dominant wavelength from 560 to 580 nm. This is but one example of light sources that can be used with embodiments of the present invention. Various numbers and types of LEDs can be combined. Further examples and details of mixing colors of light using solid state emitters can be found in U.S. Pat. No. 7,213,940, which is incorporated herein by reference. In one embodiment, as shown inFIGS. 8A-8D, three LED light sources24may be used where each light source24includes four LED chips31a-31dwhere the red-emitting LED chip is shown as shaded and the BSY LED device is shown unshaded. The LED chips are arranged such that between the three LED light sources24a red-emitting LED chip is located in each of the four quadrants. In other words if the three LED light sources24were overlayed on top of one another a red-emitting LED chip would be located in each quadrant.

In the illustrated embodiment, the TIR optical element12is shown with three lobes12a,12b,12cwhere each lobe corresponds to an LED light source24and each light source24in this example embodiment includes four LED chips31a-31d. The TIR optical element12has an exit surface38that comprises a first portion43that comprises a flat substrate with a microlens for diffusing light and a second portion that comprises discrete lenses40a,40band40carranged in a one to one relationship with the LED light sources24. The lenses40a,40band40ceach have an exit surface45through which the light exits the lenses. In the illustrated embodiment each lobe12a,12band12ccomprises a lens40a,40band40carranged such that one lens corresponds to and is arranged in line with one of the LED light sources24. The TIR optical element12and the heat sink14do not have to be provided with a lobed configuration provided that the lenses40a,40band40care provided on the TIR optical element in a one-to-one corresponding relationship to the LED light sources24. The lenses40a,40band40calso includes recessed, curved entrance surfaces42that receive light from one of the LED light sources24and that transmit light to the corresponding exit surfaces45of lenses40a,40band40c. While a single TIR optical element is shown, multiple TIR elements may be used.

Light from the LED light source is directed as shown inFIG. 6where one lens40a, having an entry surface42, an exit surface45and surrounding portion of the TIR optical element12, is shown. Each of the lenses40a,40band40coperates in substantially an identical manner such that specific reference will be made to lens40a. A portion of the light A from light source24is emitted directly into the entrance surface42, exits from exit surface45and is focused by the lens40ato create a beam of collimated light. A further portion of the light B is directed onto the TIR surface of the TIR optical element12where it is reflected toward exit surface38. The light may exit from the microlens43. The microlens43mixes the light and disperses the light to overlap with the light exiting from lenses40a-40c. Light that escapes from the TIR optical element12may be reflected back into the TIR optical element by secondary reflector22where it also may exit through the microlens43and lens40a. Typically, the angular distribution of light emitted from an LED light source is close to Lambertian, which has Full Width at Half Maximum (FWHM) beam angle of 120 degrees. The TIR optical element12as described herein may be used in directional lighting to collimate the light at a narrow beam angle such as between 12 and 60 degrees.

The lenses40a,40band40care formed as faceted domed lenses to disperse the light in a manner that mixes the light and eliminates dark spots in the projected light. Round dome lenses are known for collimating light in directional lighting applications. One problem with round dome lenses is that the light projected from a plurality of LED chips may show up as distinct light areas separated by darker areas. For example, in a system that uses four LED chips light may be projected as four relatively distinct squares of light separated by darker, unlit lines. The faceted lenses40a,40b,40cbetter mix light exiting the lamp and eliminate the dark spots or lines to create a more uniform, better shaped beam.

Each faceted lens40a,40b,40cincludes a plurality of facets50on the entrance surface42and/or exit surface45that are disposed relative to the LED light sources24such that light from each light source24is mixed with light from other ones of the light sources24. The facets50are disposed such that they are asymmetrically arranged with respect to the associated LED light source24such that the light from each of the light sources is dispersed in an asymmetrical manner. The facets50are arranged such that the lenses collimate the light beam. Each facet50may be a planar surface or the facets may be slightly convex or concave in shape. In the embodiment ofFIGS. 1-6the facets50are formed on the exit surfaces45. InFIG. 11the facets50are formed on the entrance surfaces42. The facets may be provided on either the entrance surfaces42of the lenses40a,40b,40cor the exit surfaces45of the lenses40a,40b,40c. Moreover, both the exit surfaces and the entrance surfaces of each of the lenses40a,40b,40cmay be faceted as will be explained.

An example arrangement of one light source and a faceted dome lens is shown diagrammatically inFIG. 7. One LED light source24is shown having four LED chips31a-31dwhere the chips may emit different color light as previously described. A faceted lens40ais shown overlayed on the LED light source24to illustrate the arrangement of the facets50relative to the LED chips31a-31d. In the illustrated embodiment six facets50are provided on one lens40awhere the six facets50are arranged relative to the LED chips31a-31dand divide the light projected by the LED light source24asymmetrically. For example, a major portion of the light from LED chip31b(shaded area a) is directed through facet50′ while a second smaller or minor portion of the light from the same LED chip31b(shaded area b) is directed through facet50″. A relatively small or minor portion of the light from LED chip31c(shaded area c) is directed through facet50′ and mixed with the major portion of the light from chip31b. The minor portion, shaded area b, of the light from LED chip31bdirected through facet50″ and mixed with a minor portion of the light from LED chip31a(shaded area d). The same relationship is true for each of the LED chips where a portion of the light from each LED chip passes through at least two different facets. Mixing of light for all of the LED chips31a-31doccurs at each facet50. Because the facets50are disposed at varying angles relative to the light beam, light directed through each facet50is projected at a slightly different angle as the light projected through any other facet. The facets enhance mixing of light and may be used where the adjacent chips project light of the same color and/or light of a different color. The light from the different chips31a-31ddirected through the facets50is mixed upon exiting the TIR optical element12and the projected dark and light spots found with round dome lenses are eliminated to create a better mixed and shaped uniform beam of light. The actual angular relationship of the light source24and the faceted lens may vary from that shown in the figures.

In the illustrated embodiment six facets50are used with four LED chips31a-31dbecause the six equally dimensioned and shaped facets50asymmetrically divide the light projected from the four LED chips31a-31d. If four or eight facets of equal size and shape were used, the light from the four LED chips would be symmetrically divided and the resultant light mixing would not be obtained. However, some mixing benefit would be obtained if four or eight facets were used with four LED chips if the facets were asymmetrically related to one another and to the chips such as by making each facet of a different size and shape. The number of facets used on each lens is dependent on the number of chips in each light source and is determined such that an asymmetrical relationship is established between the facets and the chips. In one embodiment the number of facets is selected such that it is not evenly divisible by the number of LED chips. Moreover, the number of facets is selected so as to be as far from an evenly divisible number as possible. For example, in the illustrated example with four LED chips both four (facets) and eight (facets) are divisible by 4 (the number of LED chips) while six (facets) is not divisible by four (the number of LED chips). Thus, six facets provides the desired asymmetrical relationship between the facets and LED chips. While five (facets) and seven (facets) are also not divisible by four, both five and seven are closer to the divisible numbers four and eight than is six. Therefore, six facets will provide better light mixing than either four, five, seven or eight facets. Where more or less than four chips are used in the LED light source the number of facets will likewise vary to provide the asymmetric relationship between the chips and the facets.

Referring toFIG. 9an example arrangement of one light source24and a faceted dome lens is shown diagrammatically where both the entrance surface42and the exit surface43of the same lens are faceted. In such an arrangement the entrance surface42may be angularly offset relative to the exit surface43by an angle α such that the facets50of the entrance surface42are angularly offset relative to the facets150of the exit surface45. Alternatively, the entrance surface42may be provided with a different number of facets150than the number of facets50and the number of LED chips. In the illustrated example five facets50of the entrance surface42may be used in combination with the six facets150of the exit surface45and the four LED chips31a-31d. In one embodiment the angular offset α between the entrance surface42and the exit surface43is between 20 and 30 degrees. The faceting of both the entrance and exit surfaces enhances mixing of the light as shown where the light from each of LED chips31a-31dis mixed by the entrance surface42and the exit surface45in an asymmetric manner. Each faceted surface is asymmetrically related to the light source24and the faceted surfaces are angularly offset relative to one another.

In addition to faceting the entrance surfaces42and exit surfaces45of the lenses40a,40b,40c, the interior surface47of the body of the optical element12that surrounds the light source24and that leads to the entrance surface42of the lens may also be faceted as shown inFIG. 10. The faceting of surface42enhances the mixing of the light that exits the TIR optical element12through the microlens43.

Embodiments of the invention can use varied fastening methods and mechanisms for interconnecting the parts of the lighting system and luminaire. For example, in some embodiments locking tabs and holes can be used. In some embodiments, combinations of fasteners such as tabs, latches or other suitable fastening arrangements and combinations of fasteners can be used which would not require adhesives or screws. In other embodiments, adhesives, screws, bolts, or other fasteners may be used to fasten together the various components.