Patent Application
20150192257
Light emitting diode (LED) lighting systems are becoming more prevalent as replacements for traditional lighting systems. 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 on 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 or strip of a fixture includes 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 leads, housing and heat sink.
An LED fixture may be made with a form factor that allows it to replace a standard threaded incandescent bulb, or any of various types of fluorescent lamps. LED fixtures and lamps often include some type of optical elements external to the LED modules themselves. Such optical elements may allow for localized mixing of colors, collimate light, and/or provide the minimum beam angle possible.
Optical elements may include reflectors, lenses, or a combination of the two. Reflectors can be, for example, of the metallic or mirrored type, in which light reflects of opaque silvered surfaces. Reflectors may also be made of glass or plastic and function through the principle of total internal reflection (TIR) in which light reflects inside the optical element because it strikes an internal surface of the element at an angle which is equal to or greater than the critical angle relative to the normal vector.
Embodiments of the present invention provide an optical element, or “optic” that can enable a lighting system to achieve beam control. The optic combines TIR and other surfaces into one collimator. The optic collects light from substantially all angles of an LED's light output and collimates the light into a narrow beam angle. A lighting system according to example embodiments of the invention can include a single LED and optic, or can include a plurality of LEDs and optics.
An optical element according to at least some embodiments of the invention includes an entry surface and an exit surface. A concentrator lens is disposed opposite the entry surface and the concentrator lens is recessed relative to the exit surface. The concentrator lens may be, as examples, a convex lens or a surface forming, or acting as, a convex lens, or a Fresnel lens. In example embodiments, a mounting feature adjacent to the entry surface spaces the entry surface and concentrator lens from an LED. An outer surface is disposed between the exit surface and the mounting feature. In example embodiments of the invention, the outer surface provides the TIR surface for the optic.
In at least some embodiments, the mounting feature is sized so that the LED would be at a focal point of the concentrator lens and opposite the radial center of the entry surface relative to the concentrator lens. In some embodiments, the mounting feature has a thickness of between 0.5 mm and 1.0 mm. In some embodiments, the mounting feature has a thickness of about 0.75 mm. In some embodiments, the mounting feature is adapted to fit around a submount of an LED device package. In some embodiments, the mounting feature and the entry surface of the optic form an optic-device interface that conforms to the LED device package. In some embodiments, the outer, TIR surface of the optic is at least partially parabolic. In some embodiments, the entry surface has a radius between 1.5 mm and 2.0 mm.
In some embodiments, the base of the recessed, concentrator lens is recessed from about 14 mm to about 18 mm relative to the exit surface, resulting in the exit surface having a flat, annular shape. Thus, a substantially cylindrical wall is formed between the flat, annular exit surface and the base of the concentrator lens. In at least some embodiments, the angle between the exit surface and the substantially cylindrical wall is greater than 90 degrees. In some embodiments of the invention, the angle is about 91 degrees and the base of the concentrator lens is recessed from about 15.5 mm to about 16.0 mm away from a flat, annular exit surface. The concentrator lens can take various forms. As examples the concentrator lens can be or include a convex refracting surface (acting as or being a convex lens) or a Fresnel lens.
A lighting system making use of an optic according to embodiments of the present invention can include at least one LED, and an optical element placed next to an LED so that a center of the LED is at a focal point for the concentrator lens and the optical element receives light from the LED through the entry surface. An electrical connection is provided for the LED or for each of the LEDs if multiple LEDs and optics are used. It should be noted that the mounting feature is located so as not to detract from the luminous area of the optic and in example embodiments does not directly affect the light pattern, but rather, provides appropriate spacing for the other features of the optic. In some embodiments, the mounting feature forms a part of the optical element. In some embodiments, the mounting feature, which may also be referred to herein as a spacer, is fastened to the optical element. This fastening may be accomplished, as an example, through the use of an adhesive. The mounting feature may also be fastened to or rest on an adjacent structure, such as a structure inside a lighting system making use of the optic.
Embodiments of the present invention now will be described more fully hereinafter with reference to the accompanying drawings, in which embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout.
It will be understood that, although the terms first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element could be termed a second element, and, similarly, a second element could be termed a first element, without departing from the scope of the present invention. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.
It will be understood that when an element such as a layer, region or substrate is referred to as being “on” or extending “onto” another element, it can be directly on or extend directly onto the other element or intervening elements may also be present. In contrast, when an element is referred to as being “directly on” or extending “directly onto” another element, there are no intervening elements present. It will also be understood that when an element is referred to as being “connected” or “coupled” to another element, it can be directly connected or coupled to the other element or intervening elements may be present. In contrast, when an element is referred to as being “directly connected” or “directly coupled” to another element, there are no intervening elements present.
Relative terms such as “below” or “above” or “upper” or “lower” or “horizontal” or “vertical” may be used herein to describe a relationship of one element, layer or region to another element, layer or region as illustrated in the figures. It will be understood that these terms are intended to encompass different orientations of the device in addition to the orientation depicted in the figures.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” “comprising,” “includes” and/or “including” when used herein, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.
Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms used herein should be interpreted as having a meaning that is consistent with their meaning in the context of this specification and the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
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.”
The terms “LED” and “LED device” as used herein may refer to any solid state light emitter. The terms “solid state light emitter” or “solid state emitter” may include a light emitting diode, laser diode, organic light emitting diode, and/or other semiconductor device which includes one or more semiconductor layers, which may include silicon, silicon carbide, gallium nitride and/or other semiconductor materials, a substrate which may include sapphire, silicon, silicon carbide and/or other microelectronic substrates, and one or more contact layers which may include metal and/or other conductive materials. A solid state lighting device produces light (ultraviolet, visible, or infrared) by exciting electrons across the band gap between a conduction band and a valence band of a semiconductor active (light-emitting) layer, with the electron transition generating light at a wavelength that depends on the band gap. Thus, the color (wavelength) of the light emitted by a solid state emitter depends on the materials of the active layers thereof. In various embodiments, solid state light emitters may have peak wavelengths in the visible range and/or be used in combination with lumiphoric materials having peak wavelengths in the visible range. Multiple solid state light emitters and/or multiple lumiphoric materials (i.e., in combination with at least one solid state light emitter) may be used in a single device, such as to produce light perceived as white or near-white in character. In certain embodiments, the aggregated output of multiple solid state light emitters and/or lumiphoric materials may generate warm white light output having a color temperature range of from about 2700K to about 4000K.
Solid state light emitters may be used individually or in combination with one or more lumiphoric materials (e.g., phosphors, scintillators, lumiphoric inks) and/or optical elements to generate light at a peak wavelength, or of at least one desired perceived color (including combinations of colors that may be perceived as white). Inclusion of lumiphoric (also called ‘luminescent’) materials in lighting devices as described herein may be accomplished by direct coating on solid state light emitter, adding such materials to encapsulants, adding such materials to lenses, by embedding or dispersing such materials within lumiphor support elements, and/or coating such materials on lumiphor support elements. Other materials, such as light scattering elements (e.g., particles) and/or index matching materials may be associated with a lumiphor, a lumiphor binding medium, or a lumiphor support element that may be spatially segregated from a solid state emitter.
Referring to
Referring now to
Turning to
where x, y and z are positions on a typical 3-axis system, k is the conic constant, and c is the curvature. The formula specifies conic shapes generally. For a parabolic shape, k is less than or equal to −1. However, it should be noted that the outer surface being or including a surface that is parabolic, and indeed being or including a surface that is conic is just an example. Optical elements could be designed with outer surfaces of various shapes; for example, angled, arced, curved as well as spherical, including segmented shapes.
A parabolic surface or parabolic surfaces as shown in the examples disclosed herein may be used to provide total internal reflection (TIR), however, there may be instances where total internal reflection is not be needed or desired at all points of the optic. In at least some embodiments, the cross-sectional curve of surface 106 may include several parabolic curve sections combined by simulation to maximize the TIR characteristics of the optic.
Still referring to
In at least some embodiments, the chip is coated with or packaged with a lumiphor in order to create substantially white light. The emitter package can be referred to herein merely as an “LED” even if it contains more elements than a lone semiconductor die. In at least some systems, the LED chip itself is packaged and fastened to a flat structure that is or is similar to a small circuit board, which provides electrical connections. The LED device lens may also be fixed to this structure, which can be referred to as a “submount.” The submount and lens of the LED device package in
Continuing with
The optic works in part because the conic or parabolic outer surface provides for many light rays to be totally reflected internally and exit the optic through the exit surface 102 at or near a normal angle relative to the exit surface. However, since the entry surface is curved and possibly spherical in shape like the light pattern from the LED, light rays are not bent by the entry surface. Light rays which strike outer surface 106 are reflected through exit surface 102 at a normal angle. If the exit surface were contiguous across its diameter, light rays that came from the light source straight up would also exit the optic at a normal angle. However, all other light rays would leave the optical element through the exit surface 102 at an angle and be bent away from the normal vector relative to exit surface 102 if the exit surface were contiguous, since these rays would be passing from a medium with a refractive index of roughly 1.5 into air, which has a refractive index of approximately 1. This bending away would actually decrease the collimation of the light through the optical element. The recessed concentrator lens is provided to collimate these light rays so that substantially all the light leaving the optic is collimated.
In at least some embodiments, the concentrator lens can be molded into the optic, for example where acrylic is used and the entire optic is injection molded. The concentrator lens could also be placed upon a flat recessed surface within the optic and fastened there with adhesive, force fit into the recess, or otherwise mounted by fasteners, tabs, or the like. These latter techniques may be more effective if the concentrator is other than a convex lens surface, such as the Fresnel lens shown in
Although specific embodiments have been illustrated and described herein, those of ordinary skill in the art appreciate that any arrangement which is calculated to achieve the same purpose may be substituted for the specific embodiments shown and that the invention has other applications in other environments. This application is intended to cover any adaptations or variations of the present invention. The following claims are in no way intended to limit the scope of the invention to the specific embodiments described herein.
