Patent Application
20060092644
The invention relates generally to illuminators, more specifically, to high efficiency illuminators implementing a small package design.
Illumination devices have been used for many years to provide illuminators suitable for use in various situations. For example, portable battery powered hand held flashlights or torches are very common. As technology has progressed with respect to light sources, different configurations and implementations of illumination devices have proliferated. For example, with the development of white light emitting diodes (LEDs), illumination devices using extremely low power and which may present a relatively small configuration have become widely available.
Because of their relative small size and low power consumption, illumination devices implementing LEDs as a light source have been integrated into various host devices which do not typically provide an illuminator. For example, key fobs (e.g., vehicle remote keyless entry transmitters attached to a key ring) and cellular telephones are beginning to include illuminators having an LED light source for use as a portable flashlight. However, LED devices used in the past have not provided a solution which may be easily integrated, such as by automated “pick-and-place” machinery, into an illumination device and which provides optimized light output and columniation.
Directing attention to
The foregoing illuminator configuration has been found to provide less than optimized light output and columniation for a number of reasons. It is often difficult to properly position reflector 110 and/or LED 120 on substrate 130 such that the relative positions of reflector 110 and LED 120 result in the desired columniation of light. For example, LED 120 may be disposed off-center within reflector 110. The foregoing results in a beam of light which is not as well defined as is desired, which exhibits undesired edge phenomena associated with the beam, which has non-uniform illumination within the beam, etcetera. Moreover, although providing a package configuration well suited for mechanized assembly, encapsulation 122 presents surfaces disposed such that critical angles are present with respect to a significant amount of light radiated by LED chip 121 resulting in light lost due to the total internal reflection phenomena. Specifically, light radiated by LED chip 121 and passing through the media of encapsulation 122 into the surrounding air is refracted in accordance with Snells' Law. However, some portion of the light radiated by LED chip 121 strikes the interface between encapsulation 122 and the surrounding air at a critical angle (or an angle more acute than the critical angle) associated with the boundary of these 2 media of differing refractive indices, thereby resulting in the light being reflected back into encapsulation 122 rather than passing into the air surrounding encapsulation 122.
The present invention is directed to systems and methods which provide an illuminator configuration in which an optical element is provided integral with a reflector component. Embodiments of the present invention provide an LED encapsulation optical element providing a boundary with a surrounding medium, such as air, which avoids or minimizes total internal reflection phenomena. Such an LED encapsulation optical element is formed integral with a reflector component according to embodiments of the invention in order to ensure proper relative placement of the LED light source, optical element, and reflector component and/or to facilitate rapid and predictable mechanical assembly of an illuminator. Plated through holes may be disposed in a substrate beneath the LED light source to dissipate heat from the LED light source, prolonging the life of the LED light source and/or the encapsulation material.
The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention. It should be appreciated that the conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. It should also be realized that such equivalent constructions do not depart from the invention as set forth in the appended claims. The novel features which are believed to be characteristic of the invention, both as to its organization and method of operation, together with further objects and advantages will be better understood from the following description when considered in connection with the accompanying figures. It is to be expressly understood, however, that each of the figures is provided for the purpose of illustration and description only and is not intended as a definition of the limits of the present invention.
For a more complete understanding of the present invention, reference is now made to the following descriptions taken in conjunction with the accompanying drawing, in which:
Directing attention to
Illuminator 200 of the illustrated embodiment includes LED 220, shown to comprise LED chip or die 221 incarcerated in encapsulation 222. LED 220 is disposed upon substrate 230, such as may comprise a printed circuit board or other planer structure. LED chip 221 may comprise any number of LED emitter embodiments, including single or multiple LED emitters composed of materials such as InGaN, AlInGaP, GaP, GaN, GaAs, AlGaAs, SiC, etcetera. Encapsulation 222 may be comprised of any number of formable materials which pass light of a wavelength emitted by LED chip 221, such as clear polymeric resins epoxy resins, silicone, polyurethanes, acetates, acrylates, acrylics, etcetera.
Encapsulation 222 provides a protective housing for LED chip 221 and bond wires (not shown) associated therewith. Additionally, encapsulation 222 may provide a structure upon which material may be placed to facilitate radiation of a desired color of light, such as a yellow phosphor where LED chip 221 emits a blue light and a white light is desired. Encapsulation 222 is formed as an integrated structure which includes an optical element, shown here as optical dome 224, and a reflector component, shown here as reflector surface 223. For example, encapsulation 222 may be formed from a liquid, or otherwise sufficiently moldable, material introduced into a negative mold defining a desired optical element and reflector component shape as an integrated body. Additionally or alternatively, encapsulation 222 may be formed from a solid, or otherwise hardened, material through removal of portions thereof to define a desired optical element and reflector component shape as an integrated body.
Optical dome 224 of the illustrated embodiment provides a surface shaped to avoid or minimize the effects of total internal reflection phenomena. Specifically, the surface of optical dome 224 of embodiments of the invention is shaped such that no portion of the light radiated by LED chip 221 strikes the interface between optical dome 224 and the surrounding air at a critical angle (or an angle more acute than the critical angle) associated with the boundary of these 2 media of differing refractive indices. Accordingly, no light radiated by LED chip 221 and propagating into optical dome 224 is reflected back into encapsulation 222, but rather all such light passes into the air surrounding optical dome 224.
Optical dome 224 of embodiments of the invention is additionally or alternatively shaped to columniate light radiated by LED chip 221 to provide a wave front propagating away from LED 220 in a direction substantially orthogonal to substrate 230. According to the illustrated embodiment, optical dome 224 is provided a lens shaped surface to provide the aforementioned columniation. For example, the surface of optical dome 224 providing an interface with air surrounding LED 220 is shaped as a convex lens such that a substantial portion of light radiated by LED chip 221 is refracted and directed to propagate substantially orthogonally with respect to substrate 230.
Reflector surface 223 provides a base for supporting a reflective surface, such as reflective surface 211, and is shaped and spaced from LED chip 221 and optical dome 224 to facilitate columniation of light from illuminator 200. For example, reflective surface 211 may comprise a metalized, or otherwise light reflective, coating deposited upon reflector surface 223 such as nickel, chrome, silver, and/or the like. Through cooperation of the shape of optical dome 224 and reflector surface 223, a portion of light which is not otherwise directed to propagate substantially orthogonally with respect to substrate 230 by optical dome 224 impinges upon reflective surface 211 and is reflected to propagate substantially orthogonally with respect to substrate 230. Through careful shaping of optical dome 224 and reflector surface 223 and by properly spacing optical dome 224 and reflector surface 223 light output by illuminator 200 may be optimized and/or desired beam attributes (e.g., shape, width, edge phenomena, even illumination within the beam, etcetera) may be attained.
As may be more readily appreciated from the plan view of
Although shown in the embodiment of
LED 220 of embodiments of the invention allows for mechanized assembly of illuminator 200, such as using pick-and-place machines. For example, horizontal surface 224 and/or vertical surface 225 of encapsulation 222 of the illustrated embodiment facilitate reliable interfacing with pick-and-place mechanisms. Accordingly, although optical dome 224 of the illustrated embodiment presents a compound curved surface which is often difficult to reliably interface with pick-and-place mechanisms, encapsulation 222 presents surfaces more readily interfaced with such mechanisms. Of course, optical dome 224 of embodiments of the invention may interface with the aforementioned pick-and-place mechanisms where such mechanisms are adapted to interface with the surface presented thereby and/or where optical dome 224 is shaped to interface with such mechanisms.
The illustrated embodiment of illuminator 200 disposes an optical element, here optical dome 224, within a corresponding reflector component, here reflector surface 223, eliminating a need for an external optical element, such as lens 140 of
LED chip 221 of embodiments of the invention will generate an appreciable amount of heat during operation thereof. Heat generated by LED chip 221 may degrade the material of encapsulation 222 and/or shorten the operational life of LED chip 221. Accordingly, embodiments of illuminator 200 include plated through holes 231 disposed in substrate 230 beneath LED chip 221. Plated through holes 231 provide heat conduction from LED chip 221 through substrate 230, such as may comprise a printed circuit board material such as FR4. The heat conducted by plated through holes 231 may be radiated by an exposed end of the plated through holes, may be transferred to a heat sink disposed on the underside of substrate 230, may be transferred to other components disposed on the underside of substrate 230, etcetera.
Plated through holes 231 may be provided in any number beneath LED chip 221. However, embodiments of the invention utilize 10 or fewer plated through holes for a typical LED chip. The plated through holes may be disposed in any number of configurations, which do not otherwise interfere with the electronics of illuminator 200, such as evenly spaced beneath LED chip 221 or more densely spaced in juxtaposition with “hot spots” of LED chip 221.
Although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the invention as defined by the appended claims. Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. As one will readily appreciate from the disclosure, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.
