Patent Grant
7114832
1. Field of the Invention
The invention relates the field of light sources using light emitting diodes (LEDs) and in particular to an apparatus and a method of collecting the energy radiating from them. The device could be used in general lighting, decorative and architectural lighting, portable and nonportable lighting, emergency lighting, fiber optic illumination and many other applications.
2. Description of the Prior Art
Typically in the prior art LED light source either a lens or a reflector is used to collect most of the 2π steradians front solid angle or forward hemispherical wavefront of light radiating from an LED. Recall that the solid angle Ω subtended by a surface S is defined as the surface area Ω of a unit sphere covered by the surface's projection onto the sphere. This can be written as:
where {circumflex over (n)} is a unit vector from the origin, da is the differential area of a surface patch, and r is the distance from the origin to the patch. Written in spherical coordinates with φ the colatitude (polar angle) and θ for the longitude (azimuth), this becomes
Ω≡∫∫S sin φdθdφ. (2)
A solid angle is measured in steradians, and the solid angle corresponding to all of space being subtended is 4π steradians.
Total internal reflection (TIR) is also used where the energy from the LED is collected both by an internal shaped reflector-like surface of a first lens and a second lens formed on either the outside or inside surface of the first lens.
Typically devices using a reflector alone generate a beam with two parts, one portion of the beam is reflected and controlled by the reflector and the other portion of the beam is direct radiation from the LED and is not controlled, i.e. not reflected or refracted by any other element. On a surface onto which this two-part beam is directed, the direct light appears as a large halo around the reflected beam. In the conventional 3 or 5 mm LED package a ball lens is situated in front of a cylindrical rod, and the side emitted energy from the LED is substantially uncontrolled or radiated substantially as it is generated out of the emitter junction in the chip. In TIR systems, some portion of the energy radiated from the LED junction is leaked through the walls of the package and remains uncontrolled. Additionally, there are bulk and form losses as well. In systems with LEDs turned around to point back into a concave reflector, the center energy from the LED is shadowed by the LED package itself, so this energy is typically lost or not collected into a useful beam.
What is needed is some type of design whereby efficient collection of almost all of an LED's radiated energy can be obtained and projected into a directed beam with an illumination distribution needed to be useful.
The invention is defined as an apparatus comprising an LED light source, a reflector positioned to reflect light from the LED light source which is radiated from the LED light source in a peripheral forward solid angle as defined by the reflector, and a lens disposed longitudinally forward of the LED light source for focusing light into a predetermined pattern which is radiated from the LED light source in a central forward solid angle as defined by the lens, so that the apparatus projects a beam of light comprised of the light radiated in the central forward solid angle and peripheral forward solid angles. Whereas the light source is described in the illustrated embodiment as an LED, it must be expressly understood that an incandescent or other light source can be substituted with full equivalency. Hence, wherever in the specification, “light source” is used, it must be understood to include an LED, incandescent, arc, fluorescent or plasma arc light or any equivalent light source now known or later devised, whether in the visible spectrum or not. Further, the light source may collectively comprise a plurality of such LEDs, incandescent, arc, fluorescent or plasma light sources or any other light sources now known or later devised organized in an array.
The central forward solid angle and the peripheral forward solid angle are demarcated from each other at approximately 0.6π steradian solid angle centered on the optical axis of the light source. The light source comprises an LED emitter and a package in which the LED emitter is disposed. The package comprises a hemispherical front protective dome for minimizing refraction of light radiated from the LED emitter by the package. The lens is disposed longitudinally forward of the dome.
In one embodiment the lens is suspended in front of the package lens by means of a spider.
The lens approximately collimates light radiated by the LED source into the central forward solid angle and the reflector approximately collimates light radiated by the LED source into the peripheral forward solid angle. In one embodiment of the invention the two separately formed beams will appear as if they were one. The designer has control over the individual beams, however, and may tailor the beam output individually or together to generate the desired result. In another preferred embodiment the beam or beams would be variable and the adjustment of one or both would provide a desired beam effect such as zoom or magnification.
In another embodiment the lens is disposed on the dome or made integrally with it. The lens is comprised of a peripheral annular portion having a first radius, r1, of curvature and a central portion having a second radius of curvature, r2, in which r1>r2. The peripheral annular portion minimally refracts light radiated from the LED light source, if at all, and where the central portion refracts light radiated from the LED light source to form a predetermined pattern of light.
The reflector has a focus and where the focus of the reflector is centered on the LED light source.
In the illustrated embodiment the lens is arranged and configured relative to the LED light source so that the central forward solid angle extends to a solid angle of approximately 0.6π steradians centered on the optical axis. The reflector is arranged and configured relative to the LED light source so that the peripheral forward solid angle extends from a solid angle of approximately 0.6π steradians to a solid angle of approximately 2π steradians centered on the optical axis for an included solid angle of about 1.4π steradians. More specifically, the reflector is arranged and configured relative to the LED light source so that the peripheral forward solid angle extends from a solid angle of approximately 6π steradians centered on the optical axis to a solid angle of approximately 2π steradians centered on the optical axis.
In one implemented embodiment the lens is arranged and configured relative to the LED light source so that the central forward solid angle extends to a solid angle of more than 0.6π steradians centered on the optical axis, and the reflector is arranged and configured relative to the LED light source so that the peripheral forward solid angle extends from central forward solid angle to a solid angle of more than 2π steradians centered on the optical axis.
The invention is also defined as a method comprising the steps of radiating light from an LED light source, reflecting light into a first predetermined beam portion, which light is radiated from the LED light source in a peripheral forward solid angle, and focusing light into a second predetermined beam portion, which light is radiated from the LED light source in a central forward solid angle. The central forward solid angle and the peripheral forward solid angle are demarcated from each other at approximately 0.6π steradian solid angle centered on the optical axis. Where the light source comprises an LED emitter and a package in which the LED emitter is disposed, the method further comprises the step of minimizing refraction of light radiated from the LED emitter through the package in the peripheral forward solid angle. Focusing the light into the second predetermined beam portion comprises approximately collimating the light radiated by the LED source into the central forward solid angle. Reflecting light into a first predetermined beam portion comprises approximately collimating light radiated by the LED source into the peripheral forward solid angle.
In the embodiment where the lens is disposed on the LED package, the step of focusing light into a second predetermined beam portion comprises disposing a lens the protective dome of the LED light source, transmitting the light radiated from the LED light source through a peripheral annular portion of the lens having a first radius, r1, of curvature into the peripheral forward solid angle, and transmitting the light radiated from the LED light source through a central portion of the lens having a second radius of curvature, r2, into the central forward solid angle in which r1>r2. Transmitting the light radiated from the LED light source through a peripheral annular portion of the lens minimally refracts light radiated from the LED light source, if at all. Transmitting the light radiated from the LED light source through a central portion of the lens refracts light radiated from the LED light source to form a predetermined pattern of light.
The step of reflecting light into a first predetermined beam portion comprises centering the focus of the reflector on the LED light source. The step of focusing light into a second predetermined beam portion comprises generating the central forward solid angle to extend to a solid angle of approximately 0.6π steradians centered on the optical axis of the light source. The step of reflecting light into a first predetermined beam portion comprises generating reflected light into the peripheral forward solid angle extending to a solid angle of approximately 2π steradians centered on the optical axis, or more specifically reflecting the light from the LED light source into the peripheral forward solid angle extending from a solid angle of approximately 0.6π steradians centered on the optical axis to a solid angle of approximately 2π steradians centered on the optical axis.
In one embodiment, the step of focusing light into a second predetermined beam portion comprises generating a focused beam portion into the central forward solid angle extending to a solid angle of more than 0.6π steradians centered on the optical axis, and reflecting light into a first predetermined beam portion comprises generating a reflected beam portion into the peripheral forward solid angle extending from central forward solid angle to a solid angle of more than 2π steradians centered on the optical axis.
While the apparatus and method has or will be described for the sake of grammatical fluidity with functional explanations, it is to be expressly understood that the claims, unless expressly formulated under 35 USC 112, are not to be construed as necessarily limited in any way by the construction of “means” or “steps” limitations, but are to be accorded the full scope of the meaning and equivalents of the definition provided by the claims under the judicial doctrine of equivalents, and in the case where the claims are expressly formulated under 35 USC 112 are to be accorded full statutory equivalents under 35 USC 112. The invention can be better visualized by turning now to the following drawings wherein like elements are referenced by like numerals.
The invention and its various embodiments can now be better understood by turning to the following detailed description of the preferred embodiments which are presented as illustrated examples of the invention defined in the claims. It is expressly understood that the invention as defined by the claims may be broader than the illustrated embodiments described below.
In
In
The rays of light radiating from the LED source 1 that are contained within the half angles of about 45 degrees and 0 degrees as illustrated by ray 8 will be collected by the lens 2 and controlled by the optical properties of lens 2 as illustrated in
It can thus be understood that the invention is adapted to a zoom or variable focus of the beam. For example, in the embodiment of
The variability of zoom focus can be realized in the invention by relative movement of lens 2, reflector 3 and/or LED source 1 in any combination. Hence, the lens 2 and reflector 3 as a unit can be longitudinally displaced with respect to a fixed LED source 1 or vice versa, namely lens 2 and reflector 3 are fixed as a unit and LED source 1 is moved. Similarly, lens 2 can be longitudinally displaced with respect to fixed LED source 1 and reflector 3 as a unit as described above or vice versa, namely lens 2 is fixed as LED source 1 and reflector 3 are moved as a unit. Still further, it is within the scope of the invention that the movement of lens 2, reflector 3 and LED source 1 can each be made incrementally and independently from the other. The means for permitting such relative movements of these elements and for providing motive power for making the movement within the context of the invention is obtained by the application of conventional design principles.
In
Essentially all the radiated light energy which is not absorbed by the LED chip from the LED emitter 12 are represented by rays 11, 16 or 14 in the ray diagram of
The invention provides almost complete or 100% collection efficiency of the light energy radiated from an LED source 1 or 18 for purposes of illumination, and distribution of the collected energy into a controlled and definable beam pattern. Be reminded that an LED is a light emitting region mounted on the surface of a chip or substrate. Light from the radiating junction is primarily forward directed out of the surface of the chip with a very small amount directed to the sides and slightly below the substrate's horizon. Light radiating from the junction into the substrate is partially reflected, refracted and absorbed as heat. The invention collects substantially all the light, or energy radiated from an LED source 1 or 18 which is not absorbed in the substrate on or in which it sits and redirects it into two distinct beams of light as described below. By design, these beams could be aimed primarily into a single direction, but need not be where in an application a different distribution of the beams is desired.
The invention collects all of the LED energy in the two regions or beams. The first region is approximately the forward 0.6π steradian solid angle (45 degree half angle in a side cross-sectional view) and the second region is the energy that is radiated from the LED source 1 or 18 approximately between, for example, the forward 0.6π steradian and 2.2π steradian solid angles (47 degree half angle and 95 degree half angle in a side cross-sectional view respectively) for an included solid angle of about 1.6π steradians. The exact angular dividing line between the two beams can be varied according to the application at hand. The invention thus controls substantially all of the energy radiating from the LED source 1 or 18 with only surface, small figure losses and a small loss due to the suspension means 9 for the lens 2. Figure losses include light loss due to imperfections in some aspect of the optical system arising from the fact that seams, edges, fillets and other mechanical disruptions in the light paths are not perfectly defined with mathematical sharpness, but are made from three-dimensional material objects having microscopic roughness or physical tolerances of the order of a wavelength or greater. Losses due to the edges of the Fresnel lens not being infinitely sharp or at least having a lack of sharpness at least in part at a scale of more than a wavelength of light is an example of such figure losses.
In the embodiment of
The reflector 3 may be designed to provide a collimated, convergent or divergent beam. The reflector 3 may be a common conic or not and may be faceted, dimpled or otherwise modified to provide a desired beam pattern. The device 24 may optionally have at least one additional lens and/or surface(s) formed as part of the LED packaging as illustrated in
Thus, it can now be understood that the optical design of lens 2 and contact lens assembly 10 including its longitudinal positioning relative to emitter 12 can be changed according to the teachings of the invention to obtain the objectives of the invention. For example, the nature of the illumination in the central solid angle of the two-part beam can be manipulated by the optical design of lens 2 and contact lens assembly 10, e.g. the degree of collimation. Further, the dividing line and transition between the two parts of the beam, namely the central and peripheral solid angles of the beam, can be manipulated by the longitudinal positioning and radial size or extent of lens 2 and contact lens assembly 10 relative to emitter 12.
Multiple numbers of devices 24 may be arrayed to provide additional functionality. These arrays could include two or more instances of the invention that may be individually optimized by having a unique set of lenses 2 and reflectors 3. For example, an array of devices described above could be used to provide more light than a single cell or unit. The various light sources according to the invention in such an array could be pointed in selected directions, which vary according to design for each element depending on the lighting application at hand. The elements may each have a different focus or beam pattern, or may comprise at least more than one class of elements having a different focus or beam pattern for each class. For example, the invention when used in a street light may be designed in an array to have a broadly spread beam directly under the lamp array, and a closer or more specifically focused spot or ring sending light out to the peripheral edges of the illumination pattern.
Many alterations and modifications may be made by those having ordinary skill in the art without departing from the spirit and scope of the invention. For example, while the illustrated embodiment of the invention has been described in the context of a portable flashlight, it must be understood that the potential range of application is broader and specifically includes, but is not limited to, head torches, bike lights, tactical flashlights, medical head lights, automotive headlights or taillights, motorcycles, aircraft lighting, marine applications both surface and submarine, nonportable lights and any other application where an LED light source might be desired.
Still further the invention when implemented as a flashlight may have a plurality of switching and focusing options or combinations. For example, a tail cap switch may be combined with a focusing or zoom means that is manually manipulated by twisting a flashlight head or other part. The tail cap switch could be realized as a twist on-off switch, a slide switch, a rocker switch, or a push-button switch and combined with an electronic switch for focusing. The nature, form and position of the switch and its activated control may assume any form now known or later devised and be combined with a focusing means which is manual, motorized, automated remote control and may also take any form now known or later devised.
Therefore, it must be understood that the illustrated embodiment has been set forth only for the purposes of example and that it should not be taken as limiting the invention as defined by the following claims. For example, notwithstanding the fact that the elements of a claim are set forth below in a certain combination, it must be expressly understood that the invention includes other combinations of fewer, more or different elements, which are disclosed in above even when not initially claimed in such combinations.
The words used in this specification to describe the invention and its various embodiments are to be understood not only in the sense of their commonly defined meanings, but to include by special definition in this specification structure, material or acts beyond the scope of the commonly defined meanings. Thus if an element can be understood in the context of this specification as including more than one meaning, then its use in a claim must be understood as being generic to all possible meanings supported by the specification and by the word itself.
The definitions of the words or elements of the following claims are, therefore, defined in this specification to include not only the combination of elements which are literally set forth, but all equivalent structure, material or acts for performing substantially the same function in substantially the same way to obtain substantially the same result. In this sense it is therefore contemplated that an equivalent substitution of two or more elements may be made for any one of the elements in the claims below or that a single element may be substituted for two or more elements in a claim. Although elements may be described above as acting in certain combinations and even initially claimed as such, it is to be expressly understood that one or more elements from a claimed combination can in some cases be excised from the combination and that the claimed combination may be directed to a subcombination or variation of a subcombination.
Insubstantial changes from the claimed subject matter as viewed by a person with ordinary skill in the art, now known or later devised, are expressly contemplated as being equivalently within the scope of the claims. Therefore, obvious substitutions now or later known to one with ordinary skill in the art are defined to be within the scope of the defined elements.
The claims are thus to be understood to include what is specifically illustrated and described above, what is conceptionally equivalent, what can be obviously substituted and also what essentially incorporates the essential idea of the invention.
The present application is a divisional of U.S. patent application Ser. No. 10/897,297, filed on Jul. 21, 2004, and to which priority is claimed pursuant to 35 USC 120, and now issued as U.S. Pat. No. 6,986,593, which patent in turn was related to U.S. Provisional Patent Application Ser. No. 60/508,996, filed on Oct. 6, 2003, which is incorporated herein by reference and to which priority is claimed pursuant to 35 USC 119.
| Number | Name | Date | Kind |
|---|---|---|---|
| 4530040 | Petterson | Jul 1985 | A |
| 4583153 | Tsuyama | Apr 1986 | A |
| 6827467 | Tenmyo | Dec 2004 | B1 |
| 6932490 | Emil et al. | Aug 2005 | B1 |
| Number | Date | Country | |
|---|---|---|---|
| 20060056188 A1 | Mar 2006 | US |
| Number | Date | Country | |
|---|---|---|---|
| 60508996 | Oct 2003 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 10897297 | Jul 2004 | US |
| Child | 11215538 | US |
