Abstract:
Disclosed are systems and methods which provide an illuminator configuration in which an optical element is provided integral with a reflector component. Embodiments provide an LED encapsulation optical element having 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 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.

Description:
TECHNICAL FIELD  
       [0001]     The invention relates generally to illuminators, more specifically, to high efficiency illuminators implementing a small package design.  
       BACKGROUND OF THE INVENTION  
       [0002]     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.  
         [0003]     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.  
         [0004]     Directing attention to  FIG. 1 , a cross section from the side of an exemplary prior art configuration of an illumination device having an LED light source, such as may be used as an illuminator on a cellular telephone, is shown as illuminator  100 . Illuminator  100  includes reflector  110 , shown to comprise a cylindrical body providing reflective inner surface  111  formed as a frustum of a cone, disposed upon substrate  130 , such as may comprise a printed circuit board or other planer structure. Illuminator  100  further includes LED  120 , shown to comprise LED chip or die  121  incarcerated in encapsulation  122 . Encapsulation  122  provides a protective housing for LED chip  121  and bond wires (not shown) associated therewith. Encapsulation  122  is formed as a cylinder having a flat top surface in order to facilitate mechanized assembly of illuminator  100 , such as using pick-and-place machines. Lens  140  is included to further calumniate the light emitted by LED  120  and which is reflected by reflector  110 .  
         [0005]     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&#39; 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 .  
       BRIEF SUMMARY OF THE INVENTION  
       [0006]     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.  
         [0007]     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. 
     
    
     BRIEF DESCRIPTION OF THE DRAWING  
       [0008]     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:  
         [0009]      FIG. 1  shows a cross-section view of a typical LED illuminator configuration of the prior art;  
         [0010]      FIG. 2  shows a cross-section view of a LED illuminator of an embodiment of the present invention;  
         [0011]      FIG. 3  shows a plan view of the LED illuminator of  FIG. 2 ; and  
         [0012]      FIG. 4  shows a cross-section view of a LED illuminator of an alternative embodiment of the present invention.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0013]     Directing attention to  FIG. 2 , illuminator  200  adapted according to an embodiment of the present invention is shown in a cross section view from the side. Illuminator  200  of the illustrated embodiment may be utilized as an illuminator device disposed on a host system, such as a cellular telephone or other system having a battery or similar power supply, for use as a flashlight, for example. Of course, illuminator  200  may be utilized in any number of other configurations, such as in a light fixture disposed in a home or office for general illumination, to provide illumination of objects such as signs, computer displays, etcetera, to provide light signaling such as in traffic lights, navigation markers on ships and planes, etcetera, and the like.  
         [0014]     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.  
         [0015]     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.  
         [0016]     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 .  
         [0017]     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 .  
         [0018]     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.  
         [0019]     As may be more readily appreciated from the plan view of  FIG. 3 , because reflector surface  223  is formed integral with optical dome  224  as encapsulation  222 , which incarcerates LED chip  221 , the relative placement of reflective surface  211 , disposed upon reflector surface  223 , optical dome  224 , and LED chip  221  is precisely controlled to optimize light output and/or columniation. Such precise placement is not possible in automated mass manufacturing methods as are typically employed with respect to illuminator  100  of  FIG. 1 , wherein reflector  110  and LED  120  are discrete components.  
         [0020]     Although shown in the embodiment of  FIG. 2  as being formed as a frustum of a cone, reflector surface  223  may be formed in a number of different shapes determined to provide a desired level of light output and/or columniation. For example, reflector surface  223  may be provided in a parabolic shape, as shown in  FIG. 4 , if desired. Precise relative placement of the optical element and reflector component according to embodiments of the present invention facilitates the use of reflector surface shapes, such as the aforementioned parabolic shape, which provide further optimization of light output and/or columniation. Such reflector shapes may not be practical in configurations wherein the LED and reflector are separate, such as that of  FIG. 1 , because the reflector is provided in a shape (e.g., frustum of a cone) which is tolerant to imprecise relative placement of these components.  
         [0021]     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.  
         [0022]     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  FIG. 1 . Accordingly, embodiments of the present invention provide a low profile illuminator assembly, such as may be particularly desirable for integration into various host devices which do not typically provide an illuminator, such as key fobs (e.g., vehicle remote keyless entry transmitters attached to a key ring), cellular telephones, personal digital assistants (PDAs), clothing (e.g., caps, hats, wrist bands, and belts), and the like. Moreover, the integration of the optical element and reflector component of embodiments of the present invention further provides a configuration which is resistant to damage, such as removal or repositioning of an optical element, thereby facilitating reliable use in highly portable situations, such as may be experienced when integrated with the foregoing host devices.  
         [0023]     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.  
         [0024]     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 .  
         [0025]     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.