WO2006007388A1

WO2006007388A1 - Solid state light device

Info

Publication number: WO2006007388A1
Application number: PCT/US2005/021239
Authority: WO
Inventors: Gordon D. Henson
Original assignee: 3M Innovative Properties Company
Priority date: 2004-06-16
Filing date: 2005-06-16
Publication date: 2006-01-19

Abstract

A photon emitting apparatus comprising a plurality of solid state radiation sources (104); a plurality of optical concentrators (120) in position to receive radiation from the solid state radiation sources; and a plurality of optical waveguides (130). At least the output end of each optical waveguide having a cross section that allows the optical waveguides to be closely-packed together such that there is little (i.e., less dark space than there would be if the second ends of the waveguides had a circular cross section) or no dark space in-between at least the second ends of the optical waveguides. At least the output ends of the optical waveguides are closely-packed together such that there is little or no dark space in-between at least the second ends.

Description

SOLID STATE LIGHT DEVICE

Field of the Invention

The present invention relates to an illumination or light device and system. More particularly, the present invention relates to a solid state light device and system that may replace current high intensity directed light sources.

Background of the Invention

Illumination systems are used in a variety of applications. Home, medical, dental, and industrial applications often require artificial light to be made available. Similarly, aircraft, marine, and automotive applications often require high-intensity illumination beams of light.

Traditional lighting systems have used electrically powered filament or arc lamps, which sometimes include focusing lenses and/or reflective surfaces to direct the produced illumination into a beam of light. Conventional light sources based on powered filament or arc lamps, such as incandescent or discharge bulbs, radiate both heat and light 360 degrees in all directions. Thus, the reflecting/focusing/collecting optics used, for example, in a conventional vehicular headlight application must be designed and/or specially treated to withstand the constant heating effects caused by the high intensity (and high heat) discharge bulbs that are typically used in such applications. In addition, these conventional headlights require sophisticated reflection optics to provide an industry requirements-based illumination output pattern.

Some current alternative approaches to using high power LEDs as a light source can be found in U.S. Patent No. 6,398,988. The light emitted by such a source has been directed into a single optical waveguide, such as a large core plastic optical fiber (e.g., U.S. Patents Nos. 6,272,269 and 5,299,222). In yet another approach, a bundle of individual optical fibers is used (e.g., U.S. Patent Nos. 4,811,172 and 5,222,793). These present systems are inefficient, with approximately 70% loss of the light generated in some cases. Therefore, there is a need for improved solid state lighting systems and devices. Summary Of The Invention

In accordance with one aspect of the present invention, a photon emitting device is provided that comprises a plurality of solid state radiation sources to generate radiation such as, for example, light. By "light" it is meant electromagnetic radiation having a wavelength in the ultraviolet, visible, and/or infrared portion of the electromagnetic spectrum.

In one aspect of the present invention, a photon emitting apparatus is provided that comprises a plurality of solid state radiation sources to generate radiation; a plurality of optical concentrators, with each concentrator being in position to receive radiation from at least one of the solid state radiation sources; a plurality of optical waveguides, with each of the plurality of optical waveguides having a first end that receives concentrated radiation from a corresponding optical concentrator and a second end through which the concentrated radiation is projected, with at least the second end of each optical waveguide having a cross section that allows the optical waveguides to be closely-packed together such that there is little (i.e., less dark space than there would be if the second ends of the waveguides had a circular cross section) or no dark space in-between at least the second ends of the optical waveguides; and an optional support structure to stabilize the plurality of optical waveguides between the first and second ends. At least the second ends of the optical waveguides are closely-packed together such that there is little or no dark space in- between at least the second ends.

Each of the plurality of waveguides can have a polygonal shaped cross section. The apparatus can further comprise an array connector to support the first ends of the plurality of optical waveguides in a pattern defined at least in part by the array connector. The waveguides can comprise a first group or portion of waveguides and a second group or portion of waveguides. The first ends of the first group of the waveguides can have one configuration, the first ends of the second group of the waveguides can have another configuration, and the second ends of the waveguides can be combined into a configuration that is different than either group of first ends. The waveguides can also comprise a first group or portion of waveguides and a second group or portion of waveguides, where the second ends of the first portion provide output illumination in a first direction and the second ends of the second portion provide output illumination in a second direction different from the first direction.

In addition, at least the second ends of the waveguides can have enough area in contact, between their respective cores, to allow a controlled bleeding of some light between adjacent second ends of the waveguides.

In another aspect of the present invention, a vehicular headlight illumination system is provided that comprises a photon emitting apparatus, according to the present invention. The apparatus can be located in a first vehicle compartment to generate a selected illumination pattern that is steerable. The above summary of the present invention is not intended to describe each embodiment or every implementation of the present invention. The figures and the detailed description that follow more particularly describe exemplary embodiments.

Brief Description Of The Drawings Fig. IA shows a perspective view and Fig. IB shows an exploded perspective view of a photon emitting device according to one embodiment of the present invention.

Fig. 2 shows a top view of an exemplary LED die array disposed on an interconnect circuit according to an embodiment of the present invention.

Fig. 3 shows a cross sectional side view of a photon emitting source according to an embodiment of the present-invention.

Fig. 4 shows a partially sectioned close-up side view of an individμal LED die coupled to an optical fiber by a non-imaging optical concentrator according to an embodiment of the present invention.

Figs. 5A-5F show perspective views of exemplary fiber output patterns according to alternative embodiments of the present invention.

Fig. 6A shows a perspective view of an alternative fiber output pattern for a steerable output and Figs. 6B and 6C each respectively show a perspective view of exemplary banding and support structure implementations for a steerable output in accordance with alternative embodiments of the present invention. Fig. 7 shows a perspective view of another alternative output pattern for a steerable output, where a portion of the output ends of the fibers have angle polished output faces in accordance with an alternative embodiment of the present invention.

Fig. 8 shows a perspective view of an alternative construction for a fiber array connector in accordance with an embodiment of the present invention.

Fig. 9A shows a side view of a photon emitting system adapted for pixelation in accordance with another embodiment of the present invention.

Fig. 9B shows a plane view of an exemplary controller circuit adapted for pixelation in accordance with another embodiment of the present invention. Fig. 10 shows a partially sectioned side view of an exemplary implementation of the photon emitting device, here utilized as a "cool" headlight.

Fig. 11 shows a partially sectioned side view of another exemplary implementation of the solid state light device, here utilized as part of a dental curing apparatus.

Fig. 12 shows a perspective view of another exemplary implementation of the solid state light device, here utilized as part of a radiation curing apparatus.

Fig. 13 shows a plane view of an alternative embodiment for a steerable output emission.

Fig. 14 shows a cross sectional plan view of a solid state lighting device, according to another embodiment of the present invention, with an alternative mechanism for aligning an individual optical waveguide, of a waveguide array, and an individual optical concentrator of a concentrator array.

Fig. 15 shows a partially sectioned close-up plan view of an individual LED die coupled to a concentrator aligned with an optical waveguide as shown in Fig. 14.

Figs. 16 A, 16B, 16C and 16D are each plane views respectively showing the input end, lateral side, longitudinal side and output end of an optical waveguide assembly according to one embodiment of the present invention.

Fig. 17 is a perspective view of a sub-array of optical waveguides, with each waveguide having a square cross section, in accordance with an embodiment of the present invention. Fig. 18A is a plane view showing the lateral side of an optical waveguide assembly, according to an embodiment of the present invention similar to that shown in Fig. 16B, where the optical connector is in a flat or planar state, the waveguides have the same length and the output surface formed by the waveguides has a curvature.

Fig. 18B is a plane view showing the lateral side of the optical waveguide assembly of Fig. A, where the optical connector has a curvature and the output surface formed by the waveguides is in a flat or planar state.

Fig. 19A is a plane view of the input ends of three groups or clusters of waveguides.

Fig. 19B is a plane view of the output end of the waveguides of Fig. 19A, which have been combined and reconfigured into a different shape. Fig. 20 is an enlarged view of the encircled area 20 of Fig. 19A, showing one embodiment of an optional air cladding arrangement that can control the bleeding of light between the waveguides.

While the invention is amenable to various modifications and alternative forms, specifics thereof have been shown by way of example in the drawings and will be described in detail. It should be understood, however, that the intention is not to limit the invention to the particular embodiments described. On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the scope of the invention as defined by the appended claims.

Detailed Description

The present application shares disclosure with the U.S. Patent Application Serial No. 10/726225, entitled "Solid State Light Device", which is related to and co-owned, and was concurrently filed on December 2, 2003, with U.S. Patent Application Serial No. 10/726248, entitled "Multiple LED Source and Method for Assembling Same" (Atty.

Docket No. 59376US002); U.S. Patent Application Serial No. 10/726257, entitled "LED Curing Apparatus and Method" (Atty. Docket No. 59432US002); U.S. Patent Application Serial No. 10/726997, entitled "Phosphor Based Light Sources Having a Polymeric Long Pass Reflector" (Atty. Docket No. 58389US004); and U.S. Patent Application Serial No. 10/727072, entitled "Phosphor Based Light Sources Having a Non-Planar Long Pass Reflector" (Atty. Docket No. 59416US002), each of which is incorporated by reference herein in its entirety.

The solid state radiation sources can be disposed in an array pattern. Each of a plurality of optical concentrators can be arranged in a corresponding array pattern so as to receive radiation from a corresponding solid state radiation source. The concentrated radiation can be received by a plurality of optical waveguides, also arranged in a corresponding array pattern. Each optical waveguide includes a first end to receive the radiation and a second end to output the radiation. An optional support structure is provided to stabilize the plurality of optical waveguides between the first and second ends. In exemplary embodiments of such a photon emitting device, the radiation sources can be, for example, individual LED dies or chips, or laser diodes. The waveguides may include optical fibers, such as polymer clad silica fibers. The first ends of the plurality of optical waveguides receive the radiation emitted from the radiation sources. The second ends of the plurality of optical waveguides may be bundled or arrayed to form a single radiation illumination source when illuminated.

The optical concentrators can be non-imaging optical concentrators such as, for example, reflective couplers, refractive couplers or a combination of reflective and refractive optics that couple and concentrate light emitted from the radiation sources to provide useable emissions to be guided through the corresponding optical waveguides. In an exemplary embodiment, each optical concentrator is in optical communication with and interposed between a corresponding radiation source (e.g., an LED die) and a first end of a corresponding optical waveguide.

A photon emitting device according to the present invention can be used, for example, in one or more of an LCD display where the photon emitting device is adapted for backlighting, a vehicle headlight, a dental curing apparatus and a projection system.

A photon emitting system can be provided that comprises a solid state light source that includes a plurality of solid state radiation sources to generate radiation (e.g., light), a plurality of optical concentrators, a plurality of optical waveguides and a controller. The solid state radiation sources can be disposed in an array pattern. The optical concentrators and the optical waveguides can also be arranged in a corresponding array pattern. Each optical concentrator receives radiation from a corresponding solid state radiation source. The concentrated radiation from each optical concentrator is then received by a corresponding optical waveguide. Each optical waveguide includes a first end to receive the radiation and a second end to output the radiation. The system further includes a controller, coupled to the solid state light source, to selectively activate one or more of the individual solid state radiation sources. In one embodiment of such a photon emitting system, LED dies and/or groups of the plurality of LED dies can be used for the solid state radiation sources.

A vehicular headlight illumination system can be provided that comprises a solid state light source located in a first vehicle compartment to generate a selected illumination pattern. Heat generated by the solid state light source can be distributed to a location remote from the first compartment and away from the solid state device.

Fig. IA shows a solid state light device 100 (also referred to herein as an illumination device or photon emitting device) in an exemplary configuration. Light device 100 is shown in an exploded view in Fig. IB. By "light" it is meant electromagnetic radiation having a wavelength in the ultraviolet, visible, and/or infrared portion of the electromagnetic spectrum. In the construction described below, the light device 100 can have an overall compact size comparable to that of a conventional High Intensity Discharge (HID) bulb, thus providing a replacement for a discharge lamp device in various applications including road illumination, spot lighting, back lighting, image projection and radiation activated curing.

Light device 100 comprises an array of solid state radiation sources 104 to generate photon radiation. The radiation is collected and concentrated by a corresponding array of optical concentrators 120. Such concentrators 120 preferably have a numerical aperture (N.A.) in the range of from about .1 to about .65. The concentrated radiation is then launched into a corresponding array of waveguides 130, which can be supported by an optional support structure 150. Each of these features will now be described in more detail.

In an exemplary embodiment, the solid state radiation sources 104 comprise a plurality of discrete LED dies or chips disposed in an array pattern. The discrete LED dies 104 are mounted individually and have independent electrical connections for operational control (rather than an LED array where all the LEDs are connected to each other by their common semiconductor substrate). LED dies can produce a symmetrical radiation pattern and are efficient at converting electrical energy to light. As many LED dies are not overly temperature sensitive, the LED dies may operate adequately with only a modest heat sink compared to many types of laser diodes. Li an exemplary embodiment, each LED die is spaced apart from its nearest neighbor(s) by at least a distance greater than an LED die width. In a further exemplary embodiment, each LED die is spaced apart from its nearest neighbor(s) by at least a distance greater than six LED die widths (e.g., 2.2 mm). Each LED die can also be spaced apart from its nearest neighbor(s) by a distance anywhere between one and ten (e.g., greater than two, three, four or five) LED die widths. These exemplary embodiments can provide for suitable thermal management, as explained in further detail below.

In addition, LED dies 104 can be operated at a temperature from —40° to 125⁰C and can have operating lifetimes in the range of 100,000 hours, as compared to most laser diode lifetimes around 10,000 hours or halogen automobile headlamp lifetimes of 500-

1000 hours. In an exemplary embodiment, the LED dies can each have an output intensity of about 50 Lumens or more. Discrete high-power LED dies can be GaN-based LED dies commercially available from companies such as Cree (such as Cree's InGaN-based XBright™ products) and Osram. In one exemplary embodiment, an array of LED dies (manufactured by Cree), each having an emitting area of about 300 μm x 300 μm, can be used to provide a concentrated (small area, high power) light source. Other light emitting surface shapes such as rectangular or other polygonal shapes can also be utilized, hi addition, in alternative embodiments, the emission layer of the LED dies utilized can be located on the top or bottom surface. hi some exemplary embodiments, a plurality of bare blue or ultraviolet (UV) LED dies can be utilized. In other exemplary embodiments, one or more LED dies can be coated, preferably on a light-emitting surface, with a phosphor layer (not shown), such as YAG:Ce phosphor. The phosphor layer can be used to convert the output of the LED die into "white" light. For example, a blue LED die can be coated with a YAG:Ce phosphor (or the like), hi this example, 'a portion of the blue light from the LED die is mixed with the phosphor-converted yellow light to effectively generate "white" light. In another example, a mixture of RGB (red, green, blue) phosphors can be used to convert UV die output to "white" light. Phosphor layer placement and construction is described in detail in a co-owned and concurrently filed U.S. Patent Application Serial No. 10/726,222, filed December 2, 2003 and entitled "Illumination System Using a Plurality of Light Sources" (Arty. Docket No. 58130US004), which is incorporated herein by reference in its entirety. In an alternative embodiment, a collection of red, blue, and green LED dies can be selectively placed in an array. The resulting emission is collected by the array of fiber waveguides 130 so that the light emitted from the output ends of the fibers is seen by an observer as colored light or "white" light, when blended together in concert. In an alternative embodiment, the LED die array may be replaced with a vertical cavity surface emitting laser (VCSEL) array, which can conventionally provide output in the visible region, including "white" light.

As shown in Fig. IB, the emission from LED dies 104 is received by a plurality of optical concentrators 120 which are, for example, disposed in a corresponding array pattern. In an exemplary embodiment, each optical concentrator receives photon radiation from a corresponding one of the LED dies 104. In an exemplary embodiment, the optical concentrators 120 comprise nόn-imaging optical concentrators (also referred to as reflective optical couplers) disposed in an array. The shape of the reflective surfaces of the optical concentrators 120 are designed to capture a substantial portion of the photon radiation emitted by each of the sources 104 to preserve the power density (lumens/mm²), hi other words, the optical concentrators 120 are designed with an N.A., preferably in the range of from about .1 to about .65, to minimize the degradation of the etendue of the LED source to more efficiently couple light.

In addition, the concentrated output can be designed in a manner to substantially match the acceptance angle criteria of the light receiving waveguides, so that a substantial portion of the radiation is useably captured by the waveguides 130 and guided therethrough. In an exemplary embodiment, each non-imaging concentrator of the array of non-imaging concentrators 120 has an interior reflecting surface conforming to a two- dimensional (2-D) surface, with at least a second portion of the interior reflecting surface conforming to a three-dimensional (3-D) surface. This and other reflective surface designs are described in detail in the commonly owned and co-pending U.S. Patent Application Serial No. 10/726,244, filed December 2, 2003 and entitled "Reflective Light Coupler" (Atty. Docket No. 59121US002), filed concurrently, and incorporated by reference herein in its entirety.

Each optical concentrator in array 120 can be formed by, e.g., injection molding, transfer molding, microreplication, stamping, punching or thermoforming. The substrate or sheeting 122 in which the optical concentrators 120 can be formed (singularly or as part of an array of optical concentrators) can include a variety of materials such as metal, plastic, thermoplastic material, or multilayer optical film (MOF) (such as Enhanced Specular Reflector (ESR) film available from 3M Company, St. Paul, MN). The substrate material used to form the optical concentrator 120 can be coated with a reflective coating, such as silver, aluminum, or reflective multilayer stacks of inorganic thin films, or simply polished in order to increase its reflectivity.

In addition, the optical concentrator substrate can be disposed so that the array of optical concentrators can be oriented beneath, around, or above the LED dies. In an exemplary embodiment, the optical concentrator substrate 122 is disposed on or proximate to the LED array so that each concentrator of array 120 can be formed to slide over each LED die 104, so that the optical concentrator's lower opening 123 (see Fig. 4) provides a close fit around the perimeter of the LED die 104. Alternative concentrator designs include the additional use of a reflective coating on the substrate on which the LED die is supported. " .

One feature of the illustrated embodiment of Fig. IB is the one-to-one correspondence between each radiation source, a corresponding optical concentrator, and a corresponding waveguide. Each optical concentrator surface is designed to convert the isotropic emission from a corresponding LED die, including, in some embodiments, phosphor-coated LED die, into a beam that will meet the acceptance angle criteria of a corresponding light-receiving waveguide. Preferably, the waveguide has a numerical aperture (N.A.) in the range of from about .1 to about .65. In one potential modification to the embodiment of Fig. IB, two or more waveguides may be optically coupled to one corresponding optical concentrator. In another potential modification to the embodiment of Fig. IB, the radiation source may comprise two or more LED die. In either modification, each optical concentrator surface is designed to convert the light emission from the corresponding LED die or dies, including in some embodiments phosphor-coated LED die, into a beam that will meet the acceptance angle criteria of a corresponding one or more light-receiving waveguides. As stated above, the concentrator surface is designed to aid in preserving the power density of the light emitted from the LED die(s). Referring back to Fig. IB, the concentrated output radiation is received by a plurality of optical waveguides 130, shown in Fig. IB as an array of optical fibers, with each waveguide having an input end 132 and an output end 133. The present exemplary embodiment includes an array 130 of large-core (for example, 400 μm to 1000 μm) polymer clad silica fibers (such as those marketed under the trade designation TECS™, available from 3M Company, St. Paul, MN). In a further exemplary embodiment, each of the optical fiber waveguides 130 can comprise polymer clad silica fibers having a core diameter of about 600 μm to 650 μm and an N.A. of about .48. In exemplary embodiments, the longitudinal lengths of the fibers can be about 1 to 5 inches (2.5 cm - 12.5 cm) in length. As the exemplary fibers are very flexible, this short distance still provides the ability to place the fibers in a tight, patterned bundle at the output ends. In addition, the short length provides for a very compact device having a size comparable to the size of conventional HID lamps. Of course, the fiber lengths can be increased in other applications without causing a detrimental effect in operation It can be desirable for the radiation source to be located remote from the output end of the fiber waveguide, for example, when the output end of the waveguide is at a location with little or no air circulation (e.g., headlight compartment), and for heat management purposes, it is desirable to position the radiation sources in a location with good to adequate air circulation (e.g., the vehicle trunk or cabin).

Other types of optical fibers, such as conventional or specialized glass fibers may also be utilized in accordance with the embodiments of the present invention, depending on such parameters as, e.g., the output wavelength(s) of the LED die sources. For example, plastic fibers may be susceptible to degradation and/or bleaching with applications involving deep blue or UV light sources.

Once the light emitted by the LED die is collected and redirected by the concentrator into the light-receiving fiber waveguide(s), the fiber(s) can be used to transport the light to a specific location with low optical loss by total internal reflection. However, the light receiving fibers do not only serve to transport light - by translating the fibers from the wider spacing of the LED die array to a tighter spacing or spacings at the output aperture, such as a tight packed fiber bundle, light from the (relatively) dispersed LED array can be effectively concentrated into a very small area. Also, the optical design of the exemplary light receiving fiber core and cladding provide for shaping the light beams emerging from the bundled ends due to the Numerical Aperture (NA) of the fibers at the input end as well as the output end. Preferably, at least the input ends of the waveguides have an N.A. in the range of from about .1 to about .65. As described herein, the light receiving fibers perform light concentrating and beam shaping, as well as light transportation.

The optical fibers 130 may further include fiber lenses on one or more of the output ends 133 of the optical fibers. Similarly, the light receiving ends 132 of the optical fibers 130 may each further comprise a fiber lens. Fiber lens manufacture and implementation is described in commonly owned and co-pending U.S. Patent Application Serial Nos. 10/317,734 and 10/670,630, which are incorporated by reference herein in their entirety.

A fiber array connector.134 can be utilized to support the first ends of each optical fiber of array 130. In an exemplary embodiment, the fiber array connector 134 comprises a rigid material, such as a molded plastic material, with a plurality of apertures having a pattern corresponding to the pattern of optical concentrators 120. Each aperture receives the input end 132 of an optical fiber of array 130 and can provide for straightforward bonding thereto.

As would be apparent to one of ordinary skill given the present description, other waveguide types, such as planar waveguides, polymer waveguides, flexible polymer waveguides, or the like, may also be utilized in accordance with the present teachings. Examples of other solid state light devices with unique waveguides are described in greater detail below.

For example, solid state light devices can be made that include, without limitation, the use of one or a combination of the following features: LEDs spaced apart from one another to reduce the overall thermal density; a non-imaging optic/reflector to get the high angle beams going forward (perpendicular to the base of the light emitting device); a reflector that may be relatively less complex; an internal optical surface to further collect the light and focus it into the waveguide; an optical high index of refraction material either cured or in a liquid form to improve the coupling of the light out of the die and/or phosphor; waveguides that are formed in conjunction with the imaging optics; gathering individual waveguides together into a compact pixelated array of guided light sources; and less time consuming than handling fiber waveguides in assembly.

Referring to Fig. 14, an alternative solid state radiation or light source assembly 30 comprises one or more sub-arrays 31 of optical waveguides 32 with corresponding optical concentrators 34, which are integrally formed together so as to have an overall unitary structure. Each concentrator 34 can be in optical communication with one or more light sources. The optical waveguides 32 can be formed with a circular, rectangular (e.g., square) or other desired cross section. Each individual optical concentrator 34 can be aligned with one corresponding optical waveguide 32 (as shown). Alternatively, one concentrator 34 can be positioned so as to concentrate the light into a cluster or group of two or more, and possibly all, of the optical waveguides 32 of the sub-array 31. As another option, the concentrators 34 of the sub-array 31 could be separated into one or more clusters or groups of two or more of the concentrators 34, with each cluster or group being aligned with one optical waveguide 32. Each optical concentrator 34 comprises a cavity 35 integrally formed with the corresponding waveguide or waveguides 32. Preferably, the cavities 35 are formed at the same time and with the same material used to form the optical waveguides 32. Though, the cavities 35 could be formed afterward. The sub-array 31 of waveguides 32 and cavities 35 can be fabricated using any one or a combination of various conventional techniques such as, for example, by injection molding or casting one or more acceptable optical waveguide materials into the desired shape. Such materials may include, for example, polymeric (e.g., plastic, elastomeric) materials that are known to be acceptable optical waveguide materials. The tooling should have optical quality finishes in the waveguide defining areas. The materials that compose the waveguides should be selected based on the process chosen and the desired optical performance needed such as, for example, optical loss, wavelength of light transmitted, index of refraction, and environmental conditions such as temperature, chemical exposure, and mechanical properties. Refering to Fig. 15, the light source assembly 30 further comprises a plurality of light sources 36, for example, discrete LED dies or chips disposed in an array pattern defined by the cavities 35. The LED dies 36 can be of any suitable size. Each cavity 35 contains one LED die 36 or a cluster of two or more but not all of the LED dies 36. Each LED die 36 can be mounted individually so that the individual dies 36 have independent electrical connections for operational control (rather than all of the LEDs in the array 31 being connected to each other and controlled in common). Alternatively, the LED dies 36 can be mounted in clusters or groups of two or more dies 36 so that each cluster or group of dies 36 has independent electrical connections for operational control (i.e., each cluster or group can be controlled separate from any other cluster or group of dies 36). Each LED 36 is mounted on a conductive substrate such as, for example, a rigid or flexible electrical circuit 38. A plurality of the sub-arrays 31 can be likewise mounted, preferably in a spaced apart manner, on one such circuit 38. In another modification, all of the sub-arrays 31 can be formed as one integral array such as, for example, by being molded or cast at one time with an interconnected structure.

The cavity 35 of each concentrator 34 is mostly, or at least partially (as shown), filled with a material 39 having an index of refraction that is greater than that of the surrounding material (i.e. the material defining the cavity 35), which in this illustrated example is the material used to make the waveguides 32. An example of such a material 39 is a gel-like material having a relatively high index of refraction of about 1.6 that is manufactured by Nye Optical Products, located in Fairhaven, MA 02719, under the product designation NyoGel OC-462. In the illustrated embodiment, each concentrator 34 includes a reflective optical coupler 40. The individual LED die 36 (as shown), or each cluster of two or more dies 36. (as alternatively proposed), is disposed within a reflective cavity 42 of the reflective coupler 40. To facilitate extraction of light out of the die 36, it is desirable for the cavity 42 to be filled with a material having an index of refraction of at least about 1.5. The reflective surface of the cavity 42 is designed to capture a substantial portion of the light emitted by the LED die(s) 36, disposed therein, and direct the light rays into the material 39 and out of the cavity 35 at an angle that will preserve the power density (lumens/mm²) of the light passing through the waveguide 32. In other words, the optical concentrators 34 are designed to minimize the degradation of the etendue of the LED source 36 to more efficiently couple light. Each LED die 36 can be coated with an appropriate phosphor, if necessary to produce the desired light (e.g., white light) output. Alternatively, the reflective cavity 42 can be filled with the appropriate phosphor so that each LED die 36 is encapsulated with the phosphor. One exemplary light source assembly 30 comprises one or more of the sub-arrays

31, as shown in Figs. 14 and 15, with each of the LED dies 36 being about 300 μm x 300 μm square, each of the cavities 35 having a diameter of about 750 μm., the dies 36 being spaced apart about 2.5 mm from central axis to central axis, the corresponding aligned concentrators 34 and waveguides 32 also being spaced apart about 2.5 mm from central axis to central axis, and each waveguide having a diameter or width of about 800 μm.

Instead of using fiber-shaped optical waveguides as described above, with circular cross sections, it can be advantageous to use optical waveguides having polygonal (e.g., triangular, rectangular, pentagonal, hexagonal, etc.) shaped cross sections or other cross sections for the waveguides that can be closely-packed together. For example, referring to Figs. 16A through 16D, one embodiment of an optical waveguide assembly, according to the present invention, can comprise a waveguide array 50 of such optical waveguides 54, with square cross sections, and a waveguide array connector 52 for supporting the first ends 53 of each waveguide 54. Li an exemplary embodiment, the waveguide array connector 52 comprises a rigid material, such as a molded plastic material, with a plurality of apertures 55 sized and designed so as to receive therein the cross section of corresponding optical waveguides 54. When a construction like that shown in Fig. IB and Fig. 4 is used, which includes an array 120 of optical concentrators 121, the connector 52 can have a pattern of apertures 55 and the concentrator array can have a pattern of optical concentrators that correspond to, and are aligned with, each other. The input end 53 of each optical waveguide 54 of the array 50 can be inserted within a corresponding aperture 55 and the end 53 fixed in place by any suitable mechanism such as, for example, dimensioning the waveguide 54 and aperture 55 to form a friction fit, adhesively bonding the end 53 in place, welding or fusing the end 53 and aperture 55 together, or a combination thereof. Their rectangular cross section enables the second or output ends 56 of the waveguides 54 to be tightly-packed together to form an efficient light output surface 58 with little or no dark gaps between the waveguides 54 (see Fig. 16D). In this way, the surface 58 can produce a high luminosity output. The individual waveguides 54 can be fabricated using any one or a combination of various conventional techniques such as, for example, by extrusion, injection molding or casting one or more acceptable optical waveguide materials into the desired shape. Such materials may include, for example, polymeric (e.g., plastic, elastomeric) materials that are known to be acceptable optical waveguide materials. The tooling should have optical quality finishes in the waveguide defining areas. The materials that compose the waveguides should be selected based on the process chosen and the desired optical performance needed such as, for example, optical loss, wavelength of light transmitted, index of refraction, and environmental conditions such as temperature, chemical exposure, and mechanical properties.

Referring to Fig. 17, the waveguides 54 can be formed together into a sub-array 60 and a group of the waveguide sub-arrays 60 combined to form the array 50. For example, each sub-array 60 can have a desired number of waveguides 54 formed together in a row, like the prongs of a fork or comb. If it is desirable to assemble individual waveguide 54 into the connector 52, then the waveguides 54 can be cut, severed or otherwise removed from the remainder of the sub-array 60 along line 62, or at any other desired point along the length of each of the waveguides 54, and fixed into the connector 52 as described above.

Alternatively, instead of using individual waveguides 54 with the connector 52, entire sub-arrays 60 of waveguides 54 can be combined to form the array 50. For example, the waveguides 54 can be kept together in a row, and their comb shape maintained, by cutting, severing or otherwise removing a remainder 63 of the sub-array 60 along line 64. In one such embodiment, a plurality of these comb-shaped sub-arrays 60 can be used to form the array 50. The output ends 56 of each waveguide 54 in a first comb-shaped sub- array 60 is lined-up with a corresponding row of apertures 55 in the connector 52, and each output end 56 is inserted through a corresponding aperture 55 until the portion 66, of the comb-shaped sub-array 60, connecting together the waveguides 54 rests against the body of the connector 52. That is, the waveguides 54 are inserted as far as they can through the corresponding apertures 55. The waveguides 54 can be fixed in place in the connector 52 in the same manner as described above for individual waveguides 54. Another comb- shaped sub-array 60 could likewise be inserted through another row of apertures 55 and fixed in place, and the process repeated until all of the apertures 55 are filled with waveguides 54 and the array 50 is formed. In another embodiment, instead of using the comb-shaped sub-arrays 60, a plurality of the sub-arrays 31 can be provided in the form of a fork or comb and connected together using the connector 52 in the same manner as described above for the comb-shaped sub-arrays 60.

Instead of being made with apertures 55 designed to receive individual waveguides 54, the waveguide array connector 52 can also be made with slot-shaped apertures (not shown), where each slot-shaped aperture is sized and designed to receive therein the connecting portion 66 of one sub-array 60. The portion 66 of each sub-array 60 is fixed in place within the corresponding slot-shaped aperture by any suitable mechanism such as, for example, dimensioning the connecting portion 66 and slot-shaped aperture to form a friction fit, adhesively bonding, welding or fusing the portion 66 and aperture together, or a combination thereof. In another embodiment, instead of using the comb-shaped sub- arrays 60, a plurality of fork- or comb-shaped sub-arrays 31 can be provided with structure similar to connecting portion 66 and connected together using the slotted connector 52 in the same manner as described above.

The sub-array 60, as well sub-array 31, can be fabricated using any one or a combination of various conventional techniques such as, for example, by injection molding or casting one or more acceptable optical waveguide materials into the desired shape. Such materials may include, for example, polymeric (e.g., plastic, elastomeric) materials that are known to be acceptable optical waveguide materials. The tooling should have optical quality finishes in the waveguide defining areas. The materials that compose the waveguides should be selected based on the process chosen and the desired optical performance needed such as, for example, optical loss, wavelength of light transmitted, index of refraction, and environmental conditions such as temperature, chemical exposure, and mechanical properties.

Referring to Figs. 16B and 16C, if they were all the same length, the waveguides 54 would form a curved or non-planar output surface 58, like that shown in Fig. 18B. Such a curved or non-planar surface 58 could be useful in steering the light output of the lighting device by allowing, for example, a focusing lens positioned in front of the output surface 58 to be more angular sensitive. If this feature is not desirable, the assembly can be post processed (e.g., machined, cut, etc.) for the desired surface 58. In order to provide a flat or planar output surface 58 without such post assembly processing, the spaced waveguides 54 cannot all be the same length, when the waveguide input ends 53 are spaced apart, the waveguide output ends 56 are packed together and the connector 52 is flat, planar and rigid. In particular, the outer waveguides 54' need to be longer than the interior waveguides 54", because the outer waveguides have to travel a greater distance to form part of the flat planer output surface 58.

Referring to Figs. 18A and 18B, the use of waveguides 54 with different lengths can be avoided or at least reduced, if desired, by using a connector 52 that is dimensioned or made with material (e.g., a rubber or elastomeric material) that is flexible enough to be deformed into a desired curvature (i.e., the simple tent-like shape or compound dome-like shape needed to get the output surface 58 desired). When a fork- or comb-shaped sub- array 60 of waveguides 54 is used with such a flexible connector 52, rather than individual unconnected waveguides 54, it may be necessary for the connecting portion 66 to be similarly flexible as well. The connecting portion 66 may also be relatively inflexible or rigid but preformed or later plastically deformed so as to exhibit the desired curvature. Alternatively, a rigid connector 52 could be used that is preformed or later plastically deformed so as to have the desired curvature. The shape of the connector 52 can affect the appearance of the waveguide output surface 58, especially when the waveguides have the same length. Therefore, it may also be desirable at times to employ a non-planar connector 52 in order to provide a waveguide output surface 58 that is not flat and planar.

The light sources (e.g., LEDs) can also be mounted on a flexible circuit or other desired substrate to accommodate such a non-planar or curved connector 52 or, when no connector 52 is used, so that the input surface formed by the waveguides can be non-planar or curved. The ability to employ non-planar or curved input or output waveguide surfaces may have one or more or all oϊ the advantages of minimizing strain on the waveguides, reducing overall length of the waveguides (e.g., one length rather than longer and shorter lengths) and relaxing manufacturing tolerances.

It can be desirable for the waveguides to have a core surrounded or otherwise separated by a cladding such as, for example, a sheath or layer of a polymeric material, air or a combination thereof, where the cladding has a lower index of refraction than the waveguide core. A cladding other than air (e.g., the polymeric cladding) may provide more robust handling properties. The polymeric cladding could be a plastic film material, but it could also be an adhesive that maintains the output waveguide arrangement as the output surface is formed. Alternatively, the cladding could be a conventional polymeric potting resin used to fill the gaps between the waveguides, after the waveguides have been positioned into their desired orientation.

Some of the potential advantages of the above described devices of Figs. 14 - 18 are in regard to their method of fabrication. For example, the imaging optics and the waveguides can be fabricated in one process (e.g., see Figs. 14 and 15), eliminating the individual installation of each waveguide into a holder and then bonding each waveguide in place. An end finishing process, in order to get good optical transmission through the waveguide, can also be eliminated, when the waveguides are manufactured (e.g., molded, cast, etc.) to their finished shape and surface finish (e.g., see Fig. 17). Such manufacturing methods (e.g., molding or casting) helps to reduce or eliminate the internal stresses that can be present, for example, in straight fiber waveguides that are subsequently bent when installed. By eliminating, or at least reducing, such internal stresses in the waveguides, devices with shorter over all end-to-end lengths can be obtained, because the output ends of the waveguides can be bundled/brought together without having to deform (i.e., generate stress in) the waveguides. By compacting their size, the overall environmental survivability of such devices can improve by reducing or eliminating a detrimental amount of entrapped air within the device. This approach can be an improvement over large LED source devices in regard to thermal management and compactness of the overall package size. Large devices have a high thermal load per area which can cause heating issues. In addition, large devices without waveguides are subject to alignment changes with the focusing/projection optics over temperature fluctuations. The use of square cross sections (e.g., see Figs. 16) or other cross sections (e.g., other polygonal shapes) for the waveguides that can be closely-packed can also facilitate obtaining a pixelated or non-pixelated light source having an output with no apparent gaps between the waveguides, as compared with waveguides having round cross sections. This approach can also eliminate, or significantly reduce, reflective light losses due to material to air interfaces. When light passes through materials that have differences in index of refraction light, it is reflected back toward the source. A material to air interface can cause about a 10 to 15 % loss of power throughput. Closely matching material to material can result in much less loss.

This present invention can also allow for a universal package design with a number of performance options based on the number of rows and waveguides that are chosen. The bringing together of these rows of waveguides can give a natural stepped curvature on the output end of the waveguide assembly. This curvature can be used to increase the curvature of the focusing optics and, therefore, make it more effective in steering the light while keeping the optics small. This present invention can provide a more robust fabrication technique and a more universal solution for the development of a light source. A maximum number of rows of these waveguides can be established and from that a light source package, a bulb per say, could be developed. This could allow for such features as, for example, steering of the light, incorporation of multiple wavelength sources and detectors. In addition, by not fully populating the full array but using the same package, a number of smaller sizes of arrays or sub-arrays could be built and used. Referring to Figs. 19A and 19B, the light generated by a light source (e.g., an LED) can be captured or concentrated into a group or cluster 70 of waveguides 54. The waveguides 54 can then be reconfigured at their output 72 into an alternative shape that enables, or at least is more useful for, the desired application (e.g., beam shaping light engines, light beam steering, etc.). The light source, for example, can be a relatively large single LED that radiates light into all of the waveguides 54 in the group or cluster 70. The light source can also be multiple LEDs, where each LED radiates light into one of the waveguides 54. As shown, multiple groups or clusters 70 can also be used, with each group 70 having its own light source or light sources. The waveguides 54 from the multiple groups or clusters 70 can be combined together at their output 72 and reconfigured into a shape that enables a desired application (e.g., light beam steering) or into a shape that is at least more useful for that application than the shapes of the groups 70.

The quality of a pixelated light source, according to the present invention, can be improved by using square, or other similarly, cross-sectioned waveguides with no cladding (e.g., no non- light conducting polymer coating), at least at their output ends, so that the cores of adjacent waveguides are sufficiently in contact with each other to eliminate, or at least minimize, visible dark spaces between the waveguides at their output.

The lack of such dark spaces can be for imaging and projecting light over a long distance. The image gets magnified and the dark spaces can get much bigger, resulting in the projected light not being as homogeneous as desired. If too much light is allowed to transfer from one waveguide into adjoining waveguides, the ability to control pixilation of the projected light can be diminished. By controlling the amount of contact area, the amount of light that transfers is also controlled.

Referring to Fig. 19B, for example, by allowing contact between the cores of the waveguides 54 at the output 72, the bleeding of some light from one waveguide 54 to another can be facilitated. Such light bleeding between selected waveguides 54 can be desirable when illuminating one group 70 of waveguides 54 and then sequentially one or more other groups 70 (e.g., when a pixelated light source is desired), because such light bleeding can have the effect of softening the transition from one group 70 to another, as the light pattern is being expanded. This bleeding of light can be controlled, by controlling the amount of area in contact between adjacent waveguides.

Therefore, it can be desirable to allow at least some bleeding of light, preferably a controlled amount, between the cores of adjacent waveguides 54 that are surrounded, or otherwise separated, by a suitable cladding such as, for example, a layer of plastic, an adhesive layer, an air gap, or a combination thereof, where the cladding has a lower index of refraction than the waveguide core. Referring to Fig. 20, one way to accomplish such controlled light bleeding is to provide a desired amount of one or more contact areas 80 between adjacent cores of the waveguides 54 separated by an air gap 82. Such contact areas 80 are positioned at one or more desired locations along the lengths of the waveguides 54. It can be desirable for these contact areas 80 to be located only at the output 72 of the waveguides 54. It may also be desirable to locate such contact areas 80 at the input 70 of the waveguides 54, in the alternative or in addition to locating them at the output 72. The amount of contact area 80 needed to provide the desired amount of light bleeding between waveguides can depend on the properties (e.g., optical properties) of the material used to bring the waveguide cores in contact with one another and the thickness of the material in the contact area 80, as well as the degree of light bleeding needed for the particular application. The contact areas 80 can be made using the same material as the waveguide material, or at least a material having optical properties (e.g., index of refraction) that are sufficiently similar to the waveguide material to provide the necessary light bleeding. Typically, only a minimal amount of contact surface area is needed to control the bleeding of light between the waveguides. The actual amount of surface area in contact for a given application can be determined by simple trial and error experimentation.

In an exemplary embodiment, an interconnect circuit layer 110, rigid or flexible, can be utilized to provide thermal management for and electrical connection to the LED dies 104. As shown in Fig. IB, the interconnect circuit layer 110 can comprise a multilayer structure, such as 3M™ Flexible (or Flex) Circuits, available from 3M Company, Saint Paul, MN. For example, the multilayer interconnect layer 110 can comprise a metal mounting substrate 112, made of e.g., copper or other thermally conductive material, an electrically insulative dielectric layer 114, and a patterned conductive layer 113, where the LED dies are operatively connected to bond pads (not shown) of the conductive layer 113. Electrically insulative dielectric layer 114 may comprise a variety of suitable materials, including polyimide, polyester, polyethyleneterephthalate (PET), polycarbonate, polysulfone, or FR4 epoxy composite, for example. Electrically and thermally conductive layer 113 may comprise a variety of suitable materials, including copper, nickel, gold, aluminum, tin, lead, and combinations thereof, for example.

In an exemplary embodiment, and as described in more detail below, one or more groups of the LED dies 104 are interconnected with each other, but separate from other groupings of LED dies, to provide for pixelated radiation output. Electrically or thermally conductive paths or vias, for example of copper, (not shown) can be used to extend through the dielectric layer 114.' The metal mounting substrate 112 can be mounted on a heat sink or heat dissipation assembly 140. The substrate 112 can be separated from heat sink 140 by a layer 116 of electrically insulative and thermally conductive material. In an exemplary embodiment, heat sink 140 can further comprise a series of thermal conductor pins to further draw heat away from the LED die array during operation. In one exemplary embodiment, each bare LED die 104 can reside in a recessed portion of the dielectric surface 114, directly on the metal/circuit layer 113. Example implementations of interconnect circuitry are described in a currently pending and co- owned U.S. Patent Application Serial No. 10/727,220, filed December 2, 2003 and entitled "Illumination Assembly" (Atty. Docket No. 59333US002 ), which is incorporated by reference herein in its entirety.

In another embodiment, a more rigid FR4 epoxy based printed wiring board structure can be utilized for electrical interconnection. In yet another embodiment, a low cost circuit can be prepared by patterning conductive epoxy or conductive ink onto a suitable substrate as required to connect the LED die array.

Solid state light device 100 can further include an optional support structure. An output end support structure can be used to precisely and stably locate the output end light emitting surface so that the device 100 can be reliably and repeatably assembled without actively aiming the beam pattern. The support structure can also be used to fix the plurality of waveguides in place to prevent vibration induced failures in the optical waveguides, thereby increasing the useful life of the light source. In the exemplary embodiment of Fig. IB, the support structure is configured as a housing 150, having an input aperture 152 and an output aperture 154. The housing 150 can be formed, e.g., by a molding process. The housing 150 can provide strain relief for the array of waveguides 130 between the input and output ends and can prevent damage to the waveguides 130 from outside sources. In addition, housing 150 can provide a rigid support that can be preferred for vehicular applications, such as those described in more detail below. Optionally, the support structure can further include a banding 156 that is disposed in contact with a perimeter portion of the second ends of waveguides 130. The banding 156 can aid in distributing the output ends 133 of waveguides 130 in a selected output pattern, as is described in further detail below.

In addition, the fiber array connector 134 can include a ridge or indentation to receive the input aperture 152 of housing 150. While the housing 150 may be bonded or otherwise attached to fiber array connector 134, in an exemplary embodiment, the housing 150 is snap fit on fiber array connector 134. In an exemplary construction or fiber mapping method, the fibers 130 are first loaded into the fiber array connector 134 and bonded to the connector 134. A fixture (not shown) can be utilized to group fibers in rows to have an ordered grouping. The fixture can comprise multiple partitions that repeatably position each fiber from the input end to the output end. In addition, the fixture can be designed so that the fibers do not cross over one another and have a predictable location for the output ends. To secure the output end, a rigid or flexible banding, e.g. ceramic or polymer material, can be utilized to fix the location of the fibers within a desired output pattern.

Further, in an exemplary embodiment the support structure can include a housing that can be slid over the fibers and banding and can be secured to the fiber array connector. The banding can be secured within the output aperture of the housing through the use of conventional adhesives or bonding elements. Alternatively, the support structure can comprise an encapsulate material that is formed throughout and around the fiber bundle(s). The support structure 150 can also comprise an adhesive material, such as a binding epoxy, which can be applied to a portion of the waveguides 130, such that when the adhesive sets, the waveguides are fixed in a desired pattern. In an exemplary embodiment where the waveguides are optical fibers, the binding epoxy is also useful in providing support for the output ends of the fibers for polishing. The binding epoxy or adhesive can have a temporary or permanent set. In addition, the waveguides could be made structurally stable enough to eliminate the need for a support structure. The waveguide can be made by molding, casting or otherwise being formed (like that discussed above) so as to have, for example, a significantly greater length dimension than its cross-sectional dimension(s), similar to that of the fiber waveguides, while also having dimensions (e.g., being thicker) and/or being made with materials (e.g., rigid, high strength, cross-linked, etc. materials) that provide the waveguide with significantly greater stability and strength than typical waveguides.

Overall alignment can be provided by one or more alignment pins 160, which can be used to align fiber array connector 134, concentrator array 120, interconnect circuit layer 110 and heat sink 140 together. A series of alignment holes, such as alignment holes 162 shown in Fig. 2, can be formed in each of the aforementioned parts of the device 100 to receive the alignment pins 160. Alignment of the optical concentrator array 120 to the interconnect circuit layer can be accomplished through the use of fϊducials (not shown).

Fig. 2 illustrates the footprint of the solid state light device 100. In this exemplary configuration, an array of sixty (60) LED dies 104 can be provided on an interconnect circuit layer 110, which is thermally coupled to heat sink 140, in a substantially rectangular array pattern. Of course, in accordance with the present invention, the array of LED dies can comprise a substantially greater or lesser number of LED dies 104. However, as each LED die has a width of about 300 micrometers, and each LED die 104 can be spaced from its nearest neighbor by more than a LED die width, the solid state light source of the present invention can provide a high overall power density, a compact footprint area

(about 1 in² to 4 in², or 6.5 cm² to 26 cm²) and adequate thermal control. The footprint of the output ends can be smaller, the same as, or greater than the footprint at the input ends. For example, the footprint of the output ends of the fibers 133 (see Fig. IB) can be even more compact, on the order of about 0.1 in² to 1 in² ( 0.65 cm² to 6.5 cm²), in exemplary embodiments.

A side view of solid state light device 100 is shown in Fig. 3. hi this exemplary embodiment, interconnect circuit layer 110 (having LED dies mounted thereon) is disposed on heat sink 140, which further includes heat dissipation pins 142 that extend in an opposite direction from the output aperture 154. The pins 142 assist in the dissipation of heat away from the circuit layer 110 and the LED dies 104, especially when they are positioned in a location where air is able to circulate through the pins 142. In addition, as described above, the housing 150 can include protrusions 153 to allow for snap fitting onto fiber array connector 134. The array of optical concentrators 120 is disposed between the fiber array connector 134 and the interconnect layer 110. In this embodiment, fibers 130 are supported by the fiber array 'connector 134 and the banding 156, which is disposed within the output aperture 154 of housing 150.

As an alternative to using the heat sink 140, with pins 142, heat pipes can be used. Custom designed multiple cylindrical heat pipes, or pre-manufactured flat heat pipe articles, can be secured in an arrangement so as to remove heat from a cluster of Light Emitting Diode (LED) sources. This enables heat to be removed and transferred from a source that resides in a tight space to a different location. Heat pipes function in this manner, and are well known in the art. An exemplary heat pipe includes a sealed metal (e.g., aluminum or copper) container, whose inner surfaces have a capillary wicking material, that is filled with a working fluid. One end takes in heat and the other expels it. The heat entering the "hot" end of the tube boils the working fluid, which turns into a vapor. The vapor expands in volume and travels to the "cold" end where it condenses to a liquid and gives up its heat. The fluid is then returned to the hot end by gravity or a wicking action and starts the process again. The wick provides the capillary driving force to return a condensate to an evaporator. The quality and type of wick usually determines the performance of the heat pipe. There are physical limits to the rate of heat flow that can be transferred for a given temperature difference between the hot and cold ends. The heat must conduct through several interfaces and conditions. This includes heat transferred through varying thickness of the pipe walls, the thermal path of the liquid before it boils and after it condenses, and pressure differences between the hot and cold ends caused by aerodynamic friction. With this said, a heat pipe can have a delta T as low as 2°F (1⁰C).

The present invention allows for multiple, small diameter, cylindrical heat pipes to be mounted in a thermally conductive substrate. The substrate can be fixed, for example, by way of a thermally conductive epoxy/adhesive/grease, to the LEDs either directly or indirectly (additional substrates may be sandwiched between the LEDs and the epoxy). In one embodiment, the LEDs are confined to the space of an automotive headlamp.

Alternatively, heat can be removed from the LEDs using a commercially available flat heat pipe such as ThermoTek's PhasePlane™.

While heat sinks are becoming more and more elaborate in their design, there is only so much that can be done with a piece of metal. Because many heat sources reside in tight quarters (such as LEDs in a headlamp assembly), alternative cooling methods, such as heat pipes, are an attractive method for removing heat.

Heat pipes can be used to either transport the thermal energy from the LED array to a remote location with air flow and a heat sink 140, with pins 142 or to a relatively cool, solid member of the mobile platform such as a part of an automotive frame. If no air flow or cooler (less than 85C for example) solid member is available, a thermoelectric cooler can be attached in place of the heat sink 140 to maintain the LED array at a reasonable junction temperature (e.g. less than 125C) even in the presence of extreme ambient conditions, e.g. greater than 85C or even 125C.

As shown in greater detail in Fig. 4, an exemplary construction of the solid state light device 100 includes a fiber-concentrator alignment mechanism that reduces misalignment between an individual optical fiber 131 of the fiber array and an individual optical concentrator 121 of the concentrator array. In particular, the fiber array connector 134 can further include a protrusion portion 135 that engages in a depression portion 125 of the optical concentrator array substrate. Thus, fiber 131 is received in an aperture of the fiber array connector 134. The fiber array connector is then disposed on the optical concentrator substrate such that protrusion 135 is received by depression 125. In this manner, the output aperture 126 of optical concentrator 121 can be substantially flush with the input end of fiber 131. In addition, with this exemplary design, multiple input ends of the fibers can be polished at the same time so that the fiber ends are positioned with respect to the optical concentrators for sufficient optical coupling. In addition, in the example construction of Fig. 4, the receiving aperture 123 of optical concentrator 121 can be disposed to be proximate to or to surround the perimeter of an emission surface of a corresponding LED die 104. Although not shown, spacers located between the optical concentrator substrate 122 and the interconnect circuit layer 110 can set the proper spacing between these two components 104 and 121. The optical concentrator substrate 122 can then be affixed to the spacers or otherwise bonded to the interconnect circuit layer 110 using conventional techniques.

Fig. 4 further shows a cross' section of an exemplary multiple layer interconnect 110, which comprises a conductive epoxy 115 to bond LED die 104 to interconnect layer 110. First and second electrically conductive layers 113, 111 (that can comprise, e.g., nickel and gold, or other conductive materials), provide electrical traces to each LED die in the array, with dielectric layer 114 (e.g., a polyimide polymeric material) disposed to provide electrical insulation. A substrate 112 (e.g., copper) is provided to support the conductive and insulating layers, as well as to provide thermal conductivity to the heat sink 140 to conduct heat away from the direction of emission. In accordance with the principles described herein, the solid state light device 100 can provide a highly directional and/or shaped output emission, in one or more directions simultaneously. As shown in Figs. IA and IB, the output ends 133 of fiber array 130 can be patterned to provide a rectangular or square output. Figs. 5A-5F illustrate alternative reconfigurable output end patterns for the fiber array that can be employed depending on the type of illumination that is required for a particular application.

For example, Fig. 5 A shows a hexagonal output fiber pattern 133 A, Fig. 5B shows a circular output fiber pattern 133B, Fig. 5C shows a ring-shaped output fiber pattern 133C, Fig. 5D shows a triangular output fiber pattern 133D, and Fig. 5E shows a line- shaped output fiber pattern 133E. In addition, as shown in Fig. 5F, in an alternative exemplary embodiment, a segmented output pattern 133F can be provided, where multiple separate fiber output groupings can be utilized for specific targeted illumination. The banding that secures the output ends of the fibers can be formed from a material with flexibility, such as lead, tin, and zinc-based materials and alloys (or the like), as well as thermoplastic and other polymeric materials. In this way, for some applications, the fiber output pattern can be made to be reconfigurable.

As shown in Figs. 6A-6C, the output of the solid state light device 110 can be steerable, so that one or more different directions can be illuminated simultaneously or alternatively. Fig. 6A shows fiber output ends 233 arranged, e.g., in three different groupings, 233A, 233B, and 233C. For example, when utilized as a vehicular headlight, the solid state light device 100 can provide output illumination in a forward direction through output ends 233A under normal operation. In the event that the vehicle is turning to a side, the LED dies that correspond to the output fibers 233B can be activated (by, e.g., a trigger signal such as a turn signal indicator or by turning the steering wheel a set amount) so that additional illumination can be provided in that side direction through output fibers 233B. Similarly, if turning to the other side, the LED dies which correspond to the output fibers 233C can be activated so that additional illumination can be provided in that other side direction.

Alternatively, a steerable illumination system can be provided utilizing a laterally extended output arrangement of fibers, such as shown in Fig. 5E, whereby the pixelation control circuitry described below (see e.g., Figs. 9A and 9B) can activate groups, clusters or blocks (e.g., rows, columns, sections with symmetrical or asymmetrical shapes, etc.) of illuminated waveguides from one side to the other, e.g., during a turn or other event. In this manner, the output illumination can be directed towards (or away from) the direction of the turn, depending on the application. In this manner, a non-mechanical approach can be used to provide output illumination from the solid state light device that can be steerable (i.e., the beam of light can be moved and/or shaped). Alternatively, as would be apparent to one of ordinary skill in the art given the present description, greater or fewer fiber groupings can be utilized. In addition, the groupings can have a different relative orientation, such as for high beam - low beam output emissions from the same solid state light source.

In Fig 6B, a construction is shown that can be utilized to stabilize and support the different fiber groupings. For example, a banding 256 is provided at the output ends of the optical fibers. The banding 256 can provide a first aperture 254, a second aperture 254A and a third aperture 254B, where the fibers disposed in apertures 254A and 254B will output light in different directions from the fibers disposed in aperture 254. In addition, as shown in Fig. 6C, the banding 256 can be connected to or integral with housing 250, as part of the support structure for the solid state light device.

Alternatively, as shown in Fig. 7, the solid state light device can generate steerable light from a single bundle of fiber output ends. For example, fiber output ends 133 can be provided in the same location, such as output aperture 254 from Fig. 6B. In this exemplary embodiment, a portion of these output ends, identified as fiber output ends 129, are angle polished at a different angle, of even substantially different angle (e.g., by 10 to 50 degrees with respect to the fiber axis), than the remainder of fiber output ends 133. The resulting emission will be directed in a different direction from that of the output of fiber ends 133. Thus, similar to the application discussed above with respect to Figs. 6A-6C, when utilized as a vehicular headlight, the solid state light device can provide output illumination in a both a forward direction (through output ends 133) and a side direction (through output fibers 129).

In an alternative embodiment to provide steerable illumination, illustrated in Fig. 13, fibers extending from fiber array connector 734 can be bundled into multiple offset fiber bundles, central bundle 730A and side bundles 730B and 730C. Light emitted by the output ends of the fiber bundles is received by a multi-focus lens 750, such as an aspheric lens, that further directs the output from the offset bundles into desired different illumination regions 75 IA, 75 IB, and 751C. The steerable illumination can be performed automatically and/or through operator control. In an exemplary embodiment of the present invention, the solid state light device can be utilized as an illumination source, such as in a vehicle headlight application. For example, attachment to an existing headlight receptacle can be accomplished through the use of flanges 139, shown in Fig. 8. Flanges 139 can be disposed on the perimeter portion of e.g., the fiber array connector 134. The flange can be designed to engage in a locking slot of such a receptacle. Alternatively, the flanges may be formed on other components of the solid state light device, such as the housing or optical concentrator substrate.

According to another embodiment of the present invention, as shown in Fig. 9A, an illumination system 300 is provided that allows for pixelated light control that can be used for aperture shaping and/or dynamic beam movement. Such pixelated light control could be used, for example, to provide a vehicle headlight that can be dynamically steered (i.e., the beam of light dynamically moved and/or shaped). A purportedly steerable automobile headlight is described in U.S. Patent 6,406,172, which is incorporated herein by reference in its entirety. System 300 includes a solid state light source 301 that is constructed in a manner similar to solid state light source 100 described above. A controller 304 is coupled to solid state light source 301 via wiring 302 and connector 310, which can be connected to the interconnect circuit layer. A power source 306 is coupled to the controller 304 to provide power/current to the solid state light source 301. hi an exemplary embodiment, controller 304 is configured to selectively activate individual LED dies or groups of LED dies that are contained in solid state light source 301. In addition, as the light receiving waveguides are provided in a one to one correspondence with the LED dies, the illumination system 300 can provide a pixelated output. This type of pixelated control allows for the control of differently colored (e.g., red, green, and blue for RGB output) or similarly colored (e.g., white) LED dies.

Fig. 9B shows an example control circuit 305 that can provide pixelation to the array of LED dies contained in the solid state light device. In this example, sixty LED dies (LD1-LD60) are provided in the LED die array, which are grouped into three large groupings (314A - 314C) of twenty LED dies each, which are each further divided into smaller subgroups or channels (e.g., LD1-LD5) of five LED dies each. Overall, twelve channels of five LED dies each can be separately controlled in this exemplary embodiment, hi one example implementation, in an RGB output application, a first grouping of LED dies can comprise red emitting LED dies, a second grouping of LED dies can comprise blue emitting LED dies, and a third grouping of LED dies can comprise green emitting LED dies. Alternatively, in another example implementation, first, second, and third groupings of LED dies can comprise "white" emitting LED dies.

In addition, the interconnect circuit layer is also designed to provide separate interconnection for the different LED die groupings. Different types of LED die groupings, and greater or lesser numbers of LED dies, can also be utilized in accordance with the principles described herein. With this configuration, separate RGB LED die channels can be driven to provide "white" or other colored output. In addition, should a particular diode channel fail or be dimmed due to LED die deterioration, adjacent channels can be driven at higher currents so that the output illumination appears to remain unchanged. Because of the (relatively) wide LED die spacing and/or the thermal management capabilities of the interconnect layer, greater drive currents to some of the LED die channels will not adversely affect overall performance. hi addition, temperature sensors (not shown) can be disposed on the interconnect circuit layer (or other suitable locations) to sense temperature changes at or near different LED die channels. In this manner, the control circuit 305 can be used to vary the amount of current in a particular channel to compensate for a general decrease in light output in that channel due to the elevated temperature. hi more detail, circuit 305 receives a voltage through power supply 306. The voltage is converted into a regulated output current/voltage supply by boost converter chips 312A- 312C, and their associated electronics (not shown). In this manner, voltage variations from power source 306 can be mitigated, with the current/voltage supplied to the LED dies being maintained at a regulated level. Chips 312A-312C can comprise, e.g., LM2733 chips available from National Semiconductor. In this exemplary embodiment, driving voltage/current parameters can be about 20 Volts at 80 - 100 mA, thus providing a total of about 1.0 to 1.2 A for the entire LED die array. The driving current/voltage is then supplied to the different LED die channels within the array. In this example, each LED die would nominally require about 20 mA bias current, with a bias threshold increasing as the current increases, approaching about 4.0 V for an exemplary GaN-based LED die array. Of course, differing LED die efficiencies or compositions may require differing bias and driving levels.

In addition, a resistor/thermistor chain 316 can be included in circuit 305 to set the overall maximum current for each LED die channel. Further, a switch set 318, comprising a corresponding number of LED die channel electronic switches, can be provided, whereby each LED die channel is coupled/decoupled to ground (or to power, depending on the switch set arrangement relative to the LED die channels) in order to activate each particular LED die channel. The switch set 318 can be automatically controlled by a microcontroller (not shown) or a remote switch (e.g., a turn signal), based on the illumination parameters required for a particular application. Of course, this circuit architecture permits many implementations and permutations, as would be understood by one of ordinary skill in the art given the present description. For example, the control circuit 305 can be implemented to drive all LED dies with the same current, or alternatively, a given LED die channel can be turned on/off automatically or on command. By adding a fixed or variable resistance to the switch legs of the switch set, differing currents can be applied to each channel. Fig. 10 shows a schematic illustration of an exemplary solid state light device 401 utilized in a "cool" headlamp application. For example, solid state light device 401, which can be configured in accordance with the embodiments described above, is disposed in a headlight compartment 402 of an automobile or other vehicle (not shown). Light device 401 can be secured in compartment 402 through the use of slidably engaging flanges 439 that are configured to slide and lock within slots 438 of a receptacle. Thus, the heat sink 440, which draws heat away from the direction of light output is located in a separate compartment 404, such as the interior engine compartment of an automobile or other vehicle. The beam-shaped output illumination can be collected/focused into a requirements-based illumination pattern by an optical element 415. Optical element 415 can be designed to provide a selected output pattern that complies with current safety organization (e.g., NHTSA) standards. Example optical elements can include aspheric/anamorphic optical elements, and/or discontinuous and/or non-analytic (spline) optical elements.

With this approach, the use of complicated reflection optics disposed in headlight compartment 402 can be avoided. In addition, as heat is drawn away from compartment 402, there is no need to specially heat-treat any remaining optical elements in compartment 402, thus avoiding potential performance degradation caused by exposure to continual high intensity heat. Further, if solid state light device 401 is provided with an output fiber and output aperture structure such as shown above in Figs. 6A-6C, steerable output illumination can be accomplished without having to utilize moving mirror, bulb, and/or lens mechanisms that currently must be employed when steering the output from conventional HID lamps.

The solid state light device described herein may also be utilized in other applications. For example, Fig. 11 shows a schematic dental curing application, where solid state light device 501 (having a similar construction to that shown in Figs. IA and IB, and/or other embodiments herein) is contained in dental curing apparatus 500. The solid state light device 501 can be disposed in a handle portion 510 of dental curing apparatus 500. In addition, the output fibers used to receive and guide the output from the LED dies or other solid state light generating sources may extend through a light delivery arm 525 that can be placed directly over the curable material. In this application, UV and/or blue radiation sources may be utilized depending on the curing aspects of the materials receiving the illumination.

In a further alternative application, Fig. 12 shows a schematic bulk material curing apparatus, such as a web curing station. For example, in adhesive, tape, or web-based manufacturing, the adhesive agent is often a blue/UV curable material that must be cured to a different material substrate. In conventional methods, high intensity discharge and arc lamps are often utilized to perform the curing process. However, these conventional discharge lamps radiate light and heat in 360 degrees and therefore require complicated heat exchange and/or cooling mechanisms. Alternatively, the substrate material and UV curing agent must be adapted to withstand high intensity heat in some conventional approaches. Fig. 12 provides a solution to the heating problems found in conventional cuπng systems, where a curing station 600 comprises a solid state light device 604 (constructed similarly to those embodiments described above), where the heat dissipation or heat sink component of the solid state light device is located in a heat exchange unit 602. As discussed above, heat generated by the radiation sources of the solid state light device is drawn away from the direction of the light output by proper LED die spacing, thermally conductive interconnect circuitry, and/or heat sinks. hi addition, solid state light device 604 can deliver highly concentrated radiation to radiation-curable materials, thus reducing the deleterious effects caused by poor depth of cure. The concentrated output of the LED dies or other radiation-generating source can be collected and guided by the waveguide array, disposed in strain relief housing 630, and delivered to a radiation curable material 650 disposed on a substrate 652. The substrate 652 can be disposed on a moving platform or conveyor belt to provide for continual curing of large quantities of material. As mentioned above with respect to Figs. 5A-5F, the output ends of the waveguides, e.g. optical fibers, can be arranged in a number of different reconfigurable patterns, thus making the solid state light device particularly suited for curing materials having a wide variety of shapes, and/or curing depth requirements. In yet another application, the solid state light source described herein can be utilized in a projection system. Because of the ability to provide pixelated output, the LED die array can comprise different output color LED dies for RGB output. In addition, the output can be multiplexed for progressive scanning to provide a suitable projection image. Further, the solid state light device of the embodiments described above can be utilized as a source for backlighting in LCD displays, hi particular, when using phosphor coated dies for "white" emission, pixelated white LED dies can provide an increased contrast ratio for LCD displays.

While the present invention has been described with a reference to exemplary preferred embodiments, the invention may be embodied in other specific forms without departing from the scope of the invention. Accordingly, it should be understood that the embodiments described and illustrated herein are only exemplary and should not be considered as limiting the scope of the present invention. Other variations and modifications may be made in accordance with the scope of the present invention.

Claims

We Claim:

1. A photon emitting apparatus, comprising: a plurality of solid state radiation sources to generate radiation; a plurality of optical concentrators, with each concentrator being in position to receive radiation from at least one of said solid state radiation sources; a plurality of optical waveguides, with each of said plurality of optical waveguides having a first end that receives concentrated radiation from a corresponding optical concentrator and a second end through which the concentrated radiation is projected, with at least the second end of each optical waveguide having a cross section that allows said optical waveguides to be closely-packed together such that there is little or no dark space in-between at least the second ends of said optical waveguides; and an optional support structure to stabilize said plurality of optical waveguides between said first and second ends, wherein at least the second ends of said optical waveguides are closely-packed together such that there is little or no dark space in-between at least said second ends.

2. The apparatus according to claim 1, wherein said plurality of solid state radiation sources comprises a plurality of LED dies.

3. The apparatus according to claim 2, further comprising: an interconnect circuit layer to provide electrical connection to said plurality of LED dies, wherein said LED dies are bonded thereon; and a heat sink thermally coupled to said interconnect circuit layer.

4. The apparatus according to any one of claims 1 to 3, wherein each of said plurality of waveguides has a polygonal shaped cross section.

5. The apparatus according to any one of claims 1 to 4, wherein said waveguides have the same length, said first ends are spaced apart and form an input surface of said waveguides that is flat, and said second ends form an output surface of said waveguides that has a curvature.

6. The apparatus according to any one of claims 1 to 4, wherein said waveguides have the same length, said first ends are spaced apart and form an input surface of said waveguides that has a curvature, and said second ends form an output surface of said waveguides that is flat.

7. The apparatus according to any one of claims 1 to 6, further comprising an array connector to support the first ends of said plurality of optical waveguides in a pattern defined at least in part by said array connector.

8. The apparatus according to any one of claims 1 to 7, wherein said waveguides comprise a first group of waveguides and a second group of waveguides, wherein the first ends of said first group of said waveguides have one configuration, the first ends of said second group of said waveguides have another configuration, and the second ends of said waveguides are combined into a configuration that is different than either group of first ends.

9. The apparatus according to any one of claims 1 to 8, wherein at least the second ends of said waveguides have enough area in contact, between their respective cores, to allow a controlled bleeding of some light between adjacent second ends of said waveguides.

10. The apparatus according to any one of claims 1 to 9, wherein said waveguides comprise a first group of waveguides and a second group of waveguides, the second ends of said first portion provide output illumination in a first direction and the second ends of said second portion provide output illumination in a second direction different from the first direction.

11. The apparatus according to any one of claims 1 to 10, wherein a portion of said plurality of optical waveguides have shaped second ends such that light emitted from said shaped second ends is directed along a light path different from light emitted through non- shaped second ends.

12. The apparatus according to according to any one of claims 1 to 11, further comprising: an optical element to collect and distribute light from the second ends of said optical waveguides in a selected light distribution pattern.

13. The apparatus according to claim 2 or 3, wherein each LED die is spaced apart from its nearest neighbor by a spacing length that is greater than a width of said LED die.

14. The apparatus according to claim 2 or 3, wherein each LED die is spaced apart from its nearest neighbor by a spacing length that is greater than or equal to six LED die widths.

15. The apparatus according to any one of claims 2, 3, 13 and 14, further comprising: an interconnect circuit layer to provide electrical connection to said plurality of

LED dies, wherein said plurality of LED dies is arranged in a first grouping and a second grouping, wherein said first grouping of LED dies is connected to a first portion of said interconnect circuit layer and said second grouping of LED dies is connected to a second portion of said interconnect ciϊcuit layer.

16. The apparatus according to claim 15, wherein said plurality of LED dies is further arranged in a third grouping of LED dies and wherein said third grouping of LED dies is connected to a third portion of said interconnect circuit layer.

17. The apparatus according to claim 15, wherein a first output intensity of at least one LED die of said first grouping of LED dies is controllable separate from a second output intensity of at least one LED die of said second grouping of LED dies.

18. The apparatus according to claim 17, wherein said plurality of optical waveguides comprises a plurality of optical waveguides, wherein emission from said first grouping of LED dies is in optical communication with a first group of said optical waveguides, and wherein emission from said second grouping of LED dies is in optical communication with a second group of said optical waveguides.

19. The apparatus according to claim 18, wherein the second ends of said second group of optical waveguides emit radiation in a second direction different from a first direction of radiation emitted by the second ends of said first group of optical waveguides.

20. The apparatus according to any one of claims 2, 3 and 13 to 19, wherein each LED die is in optical communication with a phosphor material to convert an output emission of each LED die to a white colored light.

21. A vehicle headlight comprising said photon emitting apparatus according to any one of claims 1 to 20.

22. The apparatus according to any one of claims 1 to 21 further comprising a controller electrically coupled to said solid state light source so as to selectively activate one or more groups of said plurality of solid state radiation sources.

23. The apparatus according to any one of claims 1 to 22, wherein said solid state radiation sources are a plurality of LED dies and said LED dies comprise a first grouping of red emitting LED dies, a second grouping of blue emitting LED dies, and a third grouping of green emitting LED dies.

24. A dental curing apparatus comprising a photon emitting apparatus according to any one of claims 1 to 22.

25. A projection system comprising a photon emitting apparatus according to any one of claims 1 to 23.

26. An LCD display comprising a photon emitting apparatus according to any one of claims 1 to 23, wherein said photon emitting apparatus is adapted for backlighting.

27. A vehicular headlight illumination system comprising a photon emitting apparatus, according to any one of claims 1 to 22, located in a first vehicle compartment to generate a selected illumination pattern that is steerable.

28. The vehicular headlight illumination system according to claim 27, wherein heat generated by said solid state light source is distributed to a location apart from said first compartment.