U.S. patent application number 12/398652 was filed with the patent office on 2009-09-10 for illumination apparatus and methods of forming the same.
Invention is credited to Noam Meir, Micha Zimmermann.
Application Number | 20090225566 12/398652 |
Document ID | / |
Family ID | 40765633 |
Filed Date | 2009-09-10 |
United States Patent
Application |
20090225566 |
Kind Code |
A1 |
Zimmermann; Micha ; et
al. |
September 10, 2009 |
ILLUMINATION APPARATUS AND METHODS OF FORMING THE SAME
Abstract
An illumination device includes a waveguide having a recess in a
bottom surface thereof. Disposed beneath and in direct contact with
the bottom surface of the waveguide is a sub-assembly having a
raised profile complementary to the recess, the sub-assembly
including a discrete light source disposed on a carrier. The
discrete light source is disposed within the recess.
Inventors: |
Zimmermann; Micha; (Haifa,
IL) ; Meir; Noam; (Hezlia, IL) |
Correspondence
Address: |
GOODWIN PROCTER LLP;PATENT ADMINISTRATOR
53 STATE STREET, EXCHANGE PLACE
BOSTON
MA
02109-2881
US
|
Family ID: |
40765633 |
Appl. No.: |
12/398652 |
Filed: |
March 5, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61033876 |
Mar 5, 2008 |
|
|
|
61059932 |
Jun 9, 2008 |
|
|
|
61085576 |
Aug 1, 2008 |
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Current U.S.
Class: |
362/555 ;
362/457; 362/581 |
Current CPC
Class: |
G02B 6/0021 20130101;
Y10S 362/80 20130101; G02B 6/0083 20130101; G02B 6/0091 20130101;
G02B 6/0085 20130101 |
Class at
Publication: |
362/555 ;
362/581; 362/457 |
International
Class: |
G02B 6/00 20060101
G02B006/00 |
Claims
1. An illumination device comprising: a waveguide comprising a
recess in a bottom surface thereof; and disposed beneath and in
direct contact with the bottom surface of the waveguide, a
sub-assembly having a raised profile complementary to the recess,
the sub-assembly comprising a discrete light source disposed on a
carrier, wherein the discrete light source is disposed within the
recess.
2. The illumination device of claim 1, wherein the sub-assembly
comprises a cap disposed over the discrete light source.
3. The illumination device of claim 1, wherein the sub-assembly
comprises: a substrate; and a reflector disposed over the
substrate, wherein the reflector is disposed beneath and in direct
contact with the bottom surface of the waveguide proximate the
recess.
4. The illumination device of claim 1, wherein a top surface of the
waveguide is substantially planar.
5. The illumination device of claim 1, wherein the discrete light
source comprises a bare-die light-emitting diode.
6. The illumination device of claim 1, wherein a sidewall of the
carrier is reflective.
7. The illumination device of claim 1, wherein a top surface of the
carrier is reflective.
8. The illumination device of claim 7, wherein the top surface of
the carrier comprises an inner diffusive region surrounding the
discrete light source and a specular region surrounding the inner
diffusive region.
9. The illumination device of claim 7, wherein the top surface of
the carrier comprises an inner specular region, a diffusive region
surrounding the inner specular region, and an outer specular region
surrounding the diffusive region.
10. A illumination device comprising: a waveguide having a
substantially planar bottom surface; and disposed beneath and in
direct contact with the bottom surface of the waveguide, a
sub-assembly having a substantially planar top surface and a
discrete light source disposed on a reflective carrier, wherein a
dimension of the reflective carrier is at least three times a
dimension of the discrete light source.
11. The illumination device of claim 10, wherein the top surface of
the reflective carrier comprises an inner diffusive region
surrounding the discrete light source and a specular region
surrounding the inner diffusive region.
12. The illumination device of claim 10, wherein the top surface of
the reflective carrier comprises an inner specular region, a
diffusive region disposed around the inner specular region, and an
outer specular region disposed around the diffusive region.
13. A method of forming an illumination device, the method
comprising: providing a waveguide comprising a recess in a bottom
surface thereof; providing a sub-assembly having a raised profile
complementary to the recess, the sub-assembly comprising a discrete
light source disposed on a carrier; and mating the waveguide and
the sub-assembly such that the discrete light source is disposed
within the recess.
14. The method of claim 13, wherein a top surface of the waveguide
is substantially planar.
15. The method of claim 13, wherein the discrete light source
comprises a bare-die light-emitting diode.
16. A plurality of sub-assemblies, each of which comprises: a
plurality of discrete lighting devices disposed over a carrier;
carrier interconnections disposed on the carrier and electrically
connected to the discrete lighting devices; and a substrate
disposed beneath the carrier and comprising substrate
interconnections disposed on the substrate and electrically
connected to the carrier interconnections, wherein the plurality of
discrete lighting devices on a first sub-assembly is connected in
series, the plurality of discrete lighting devices on a second
sub-assembly is connected in parallel, and the carrier
interconnections of the first sub-assembly is substantially
identical to the carrier interconnections of the second
sub-assembly.
17. The plurality of sub-assemblies of claim 16, wherein each
sub-assembly is joined to a waveguide.
18. The plurality of sub-assemblies of claim 17, wherein each
sub-assembly comprises a contour complementary to a recess in the
waveguide to which it is joined.
19. The plurality of sub-assemblies of claim 16, wherein the series
connection on the first sub-assembly is defined by the substrate
interconnections on the first sub-assembly.
20. The plurality of sub-assemblies of claim 16, wherein the
parallel connection on the second sub-assembly is defined by the
substrate interconnections on the second sub-assembly.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority to and the benefit of U.S.
Provisional Patent Application No. 61/033,876, filed Mar. 5, 2008;
U.S. Provisional Patent Application No. 61/059,932, filed Jun. 9,
2008; and U.S. Provisional Patent Application No. 61/085,576, filed
on Aug. 1, 2008. The entire disclosure of each of these
applications is incorporated by reference herein.
TECHNICAL FIELD
[0002] In various embodiments, the present invention relates to
illumination apparatuses for artificial lighting, and in particular
to illumination apparatuses including discrete light sources such
as light-emitting diodes.
BACKGROUND
[0003] Utilizing a discrete light source, such as a light-emitting
diode (LED) to create a large, efficient, uniformly emitting
illumination device is difficult. Light from the light source may
be obstructed or absorbed by any number of structures between the
light source and the region of desired illumination; such
structures may include LED packaging, wiring circuitry, and even
parts of the sub-assembly supporting the light source. In devices
utilizing multiple light sources, e.g., devices for the
illumination of white light produced by color mixing, emitted light
may even be obstructed or absorbed by neighboring light sources.
Further, attempts to harness most of the light from the light
source may require complicated fabrication processes that are
expensive and not mass-producible.
[0004] Typical illumination devices incorporating discrete light
sources also disregard the fact that light emitted downward from
the light source (or light back-reflected toward the light source)
is often lost, reducing the efficiency of the device. This drop in
efficiency may be severe, particularly for devices incorporating
multiple light sources. Clearly, a need exists for illumination
devices (and components thereof) designed for the efficient
in-coupling of light emitted from discrete light sources, as well
as for the minimization of light obstructed or absorbed by other
components or even other light sources.
SUMMARY
[0005] Embodiments of the present invention include sub-assemblies
for the support and connectivity of discrete light sources, as well
as illumination devices incorporating such sub-assemblies, and a
waveguide for the controlled propagation and emission of light. In
general, sub-assemblies in accordance with embodiments of the
invention position discrete light sources above substantially all
other components of the sub-assembly in order to minimize the
amount of light obstructed or absorbed by such structures. In some
embodiments, the sub-assemblies mate with the waveguide; for
example, the sub-assembly (or portion thereof) may have a geometric
contour or envelope complementary to a recess in the waveguide,
thus facilitating manufacturability and enabling the "embedding" of
the light source into the waveguide (rather than positioning the
light source at the waveguide edge, for example). In addition to
providing a superior optical interface for discrete light sources,
sub-assemblies in accordance with the present invention may provide
mechanical support, electrical connectivity, and thermal
management.
[0006] In an aspect, embodiments of the invention feature a
sub-assembly matable to a waveguide having a recess therein. The
sub-assembly includes a structure that itself includes a discrete
light source disposed on a carrier. The structure has a contour
complementary to the recess such that, when the sub-assembly is
joined to the waveguide, the discrete light source is within the
waveguide. A substrate and a heat spreader are disposed beneath the
structure.
[0007] One or more of the following features may be included. The
structure may fit snugly within the recess. The discrete light
source may include a bare-die light-emitting diode. A dimension of
the top surface of the carrier may be at least three times a
dimension of the discrete light source. The top surface of the
carrier may have an area at least three times an area of the
discrete light source. The top surface of the carrier may be
reflective, and may include an inner diffusive region surrounding
the discrete light source and a specular region surrounding the
inner diffusive region. The top surface of the carrier may include
an inner specular region surrounding the discrete light source, a
diffusive region surrounding the inner specular region, and an
outer specular region surrounding the diffusive region.
[0008] A reflector may be disposed over the substrate. The discrete
light source may be disposed in a recess in the carrier, and a top
surface of the discrete light source may be substantially coplanar
with the top surface of the carrier. The top surface of the carrier
may include a step complementary to the bottom surface of the
discrete light source. The structure may include a cap disposed
over the discrete light source, and a shape of the cap may at least
partially define the contour of the structure complementary to the
recess in the waveguide. The shape of the carrier may define the
contour of the structure complementary to the recess in the
waveguide.
[0009] The discrete light source may be electrically connected to
the carrier. A contact on the discrete light source may be in
direct contact with a contact on the carrier. The discrete light
source may be electrically connected to the carrier and/or the
substrate by at least one wire. A contact on the carrier may be in
direct contact with a contact on the substrate. The substrate
and/or the carrier may include an electrical connector for
connection to an external power source.
[0010] In another aspect, embodiments of the invention feature a
sub-assembly including a discrete light source, where substantially
all of the light emitted from the discrete light source is emitted
from its top surface. A reflective carrier is disposed beneath and
in direct contact with the discrete light source. A top surface of
the reflective carrier includes an inner diffusive region
surrounding the discrete light source and a specular region
surrounding the inner diffusive region.
[0011] In yet another aspect, embodiments of the invention feature
a sub-assembly including a discrete light source, where
substantially all of the light emitted from the discrete light
source is emitted from its top surface and at least one side
surface. A reflective carrier is disposed beneath and in direct
contact with the discrete light source. A top surface of the
reflective carrier includes an inner specular region surrounding
the discrete light source, a diffusive region surrounding the inner
specular region, and an outer specular region surrounding the
diffusive region.
[0012] In another aspect, embodiments of the invention feature a
method of forming a sub-assembly matable to a waveguide having a
recess. The method includes providing a structure that includes a
discrete light source disposed on a carrier, the structure having a
contour complementary to the recess such that, when the structure
is mated to the waveguide, the discrete light source is within the
waveguide. The method also includes disposing the structure over a
substrate and a heat spreader. Providing the structure may include
providing a cap over the discrete light source, the shape of the
cap at least partically defining the contour of the structure
complementary to the recess in the waveguide. The shape of the
carrier may at least partially define the contour of the structure
complementary to the recess in the waveguide.
[0013] In an aspect, embodiments of the invention feature an
illumination device including a waveguide having a recess in a
bottom surface thereof. Disposed beneath and in direct contact with
the bottom surface of the waveguide is a sub-assembly having a
raised profile complementary to the recess. The sub-assembly
includes a discrete light source disposed on a carrier, and the
discrete light source is disposed in the recess.
[0014] One or more of the following features may be included. The
sub-assembly may include a cap disposed over the discrete light
source. The sub-assembly may include a substrate and a reflector
disposed over the substrate, and the reflector may be disposed
beneath and in direct contact with the bottom surface of the
waveguide proximate the recess. The top surface of the waveguide
may be substantially planar. The discrete light source may include
a bare-die light-emitting diode. At least one sidewall and/or the
top surface of the carrier may be reflective. The top surface of
the carrier may include an inner diffusive region surrounding the
discrete light source and a specular region surrounding the inner
diffusive region. The top surface of the carrier may include an
inner specular region, a diffusive region surrounding the inner
specular region, and an outer specular region surrounding the
diffusive region.
[0015] In another aspect, embodiments of the invention feature an
illumination device including a waveguide having a substantially
planar bottom surface. Disposed beneath and in direct contact with
the bottom surface is a sub-assembly having a substantially planar
top surface and a discrete light source disposed on a reflective
carrier. A dimension of the reflective carrier may be at least
three times a dimension of the discrete light source. The top
surface of the carrier may include an inner diffusive region
surrounding the discrete light source and a specular region
surrounding the inner diffusive region. The top surface of the
carrier may include an inner specular region, a diffusive region
surrounding the inner specular region, and an outer specular region
surrounding the diffusive region.
[0016] In yet another aspect, embodiments of the invention feature
a method of forming an illumination device including providing a
waveguide comprising a recess in a bottom surface thereof. A
sub-assembly having a raised profile complementary to the recess is
provided, the sub-assembly including a discrete light source
disposed on a carrier. The waveguide and the sub-assembly are mated
such that the discrete light source is disposed within the recess.
A top surface of the waveguide may be substantially planar. The
discrete light source may include a bare-die light-emitting
diode.
[0017] In a further aspect, embodiments of the invention feature a
plurality of sub-assemblies, each of which includes a plurality of
discrete lighting devices disposed over a carrier, carrier
interconnections disposed on the carrier and electrically connected
to the discrete lighting devices, and a substrate disposed beneath
the carrier and including substrate interconnections. The substrate
interconnections are disposed on the substrate and are electrically
connected to the carrier interconnections. The plurality of
discrete lighting devices on a first sub-assembly is connected in
series, the plurality of discrete lighting devices on a second
sub-assembly is connected in parallel, and the carrier
interconnections of the first sub-assembly is substantially
identical to the carrier interconnections of the second
sub-assembly. Each sub-assembly may be joined to a waveguide, and
each sub-assembly may include a contour complementary to a recess
in the waveguide to which it is joined. The series connection on
the first sub-assembly may be defined by the substrate
interconnections on the first sub-assembly. The parallel connection
on the second sub-assembly may be defined by the substrate
interconnections on the second sub-assembly.
[0018] These and other objects, along with advantages and features
of the present invention herein disclosed, will become more
apparent through reference to the following description, the
accompanying drawings, and the claims. Furthermore, it is to be
understood that the features of the various embodiments described
herein are not mutually exclusive and may exist in various
combinations and permutations.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] In the drawings, like reference characters generally refer
to the same parts throughout the different views. Also, the
drawings are not necessarily to scale, emphasis instead generally
being placed upon illustrating the principles of the invention. In
the following description, various embodiments of the present
invention are described with reference to the following drawings,
in which:
[0020] FIG. 1A is a top view of a sub-assembly, according to
various exemplary embodiments of the present invention;
[0021] FIG. 1B is a sectional view, taken along the line A-A', of
the sub-assembly shown in FIG. 1A;
[0022] FIGS. 2A-2C are, respectively, a top view (FIG. 2A), an
exploded sectional view (FIG. 2B), and a sectional view (FIG. 2C)
of an illumination device incorporating the sub-assembly of FIGS.
1A-1B;
[0023] FIGS. 3, 4A, and 4B are sectional views of sub-assemblies
according to various alternative embodiments of the present
invention;
[0024] FIGS. 5A and 5B are top views of a top surface of a carrier
utilized in a sub-assembly, according to various exemplary
embodiments of the present invention;
[0025] FIGS. 6A and 6B are schematic wiring diagrams for light
sources utilized in various embodiments of the present
invention;
[0026] FIGS. 7A-7C are schematic illustrations of carriers with
various surface topographies utilized in various embodiments of the
present invention; and
[0027] FIG. 8 is a sectional view of an illumination device having
a substantially planar interface between a sub-assembly and a
waveguide, according to various embodiments of the present
invention.
DETAILED DESCRIPTION
[0028] Referring to FIGS. 1A and 1B, a sub-assembly 100 includes or
consists essentially of a carrier 110, a substrate 120, heat
spreader 130, and electrical connection means 140. Carrier 110 is
typically formed of an electrically insulating, e.g., ceramic,
material, and supports one or more discrete light sources (e.g.,
LEDs) 150. In an embodiment, carrier 110 is thermally conductive
(and may therefore even be electrically conductive) in order to
provide better heat dissipation. Substrate 120 may be formed of any
rigid or flexible material, e.g., Bakelite or polycarbonate. In an
embodiment, substrate 120 includes or consists essentially of a
printed circuit board (PCB). Substrate 120 may have a thickness
ranging from approximately 25 .mu.m to approximately 50 .mu.m.
Additional active and/or passive electrical components may be
present on substrate 120, and may be electrically connected to
discrete light source 150 by means of wires, printed conductive
traces or the like. Heat spreader 130 is disposed beneath carrier
110 and includes or consists essentially of a thermally conductive
material, e.g., a metal such as aluminum or copper. Heat spreader
130 conducts heat away from carrier 110 and discrete light source
150 during operation thereof. Exposed top portions of substrate 120
surrounding carrier 120 are preferably coated with a reflective
material to form a reflector 160, e.g., a specular mirror.
Reflector 160 functions to contain light within a waveguide coupled
to sub-assembly 100 (as further described below), and may be
attached to substrate 120 via an adhesive such as VHB cold-pressing
tape available from 3M. The adhesive preferably is compatible with
and may mediate thermal expansion-related stresses between
waveguide 210, reflector 160, and substrate 120. Discrete light
source 150 is, e.g., a bare-die light-emitting diode (LED), i.e., a
substantially unpackaged LED. Preferably (and as described further
below), carrier 110 has a geometric profile complementary to that
of a recess in a waveguide, such that when sub-assembly 100 is
mated to the waveguide, discrete light source 150 is disposed
within the waveguide. The top surface 180 of carrier 110 is
preferably reflective, e.g., diffusive and/or specular, as further
described below.
[0029] Electrical conduction means 140 is a conventional electrical
interface to an external power source (not shown), and is
electrically connected to discrete light source 150 through
substrate 120 and carrier 110. In an embodiment, discrete light
source 150 is a flip-chip LED having two electrodes coupled to
electrical contacts disposed between carrier 110 and discrete light
source 150; for example, the electrical contacts may pads on the
surface of carrier 110 and connected to wires extending through the
thickness of the carrier. In this way, the electrical contacts are
electrically coupled to contact pads 170 on substrate 120 beneath
carrier 110. Contact pads 170, in turn, are coupled (on and/or
through substrate 120) to electrical conduction means 140. In an
embodiment, electrical conduction means 140 includes or consists
essentially of a flexible "PCB tail" connector attached to
substrate 120. In another embodiment, electrical conduction means
140 is directly connected to carrier 110 rather than substrate
120.
[0030] Referring to FIGS. 2A, 2B, and 2C, illumination device 200
includes or consists essentially of sub-assembly 100 disposed in
direct contact with (i.e., mated to) a waveguide 210 having a
recess 220 with a geometric profile complementary to the geometric
profile of carrier 110. FIG. 2C is a sectional view (through line
B-B' in FIG. 2A) of waveguide 210 with the raised portion of the
carrier 110 of sub-assembly 100 received within the recess 220 and
reflector 160 flush against the bottom surface of waveguide 210.
The exploded view of FIG. 2B illustrates recess 220 and its
geometric complemetarity to carrier 110. As shown in FIG. 2C, when
sub-assembly 100 is mated to waveguide 210, the raised portion of
carrier 110 fits snugly within (and may be in mechanical contact
with) recess 220; any gap therebetween is preferably filled with,
e.g., transparent optical encapsulation material, e.g., an epoxy,
silicone, or polyurethane. An adhesive (which is preferably
transparent) may be utilized to retain reflector 160 against the
waveguide 210. Thus, discrete light source 150 is disposed within
the thickness of waveguide 210, and substantially all (i.e., more
than approximately 90% of) light from discrete light source 150 is
emitted into (and may be coupled into) waveguide 210 during
operation of illumination device 200. Reflector 160, in direct
contact with the bottom surface of waveguide 210, reflects light
that would otherwise be lost back into waveguide 210. In an
alternative embodiment, reflector 160 is not present, and the
portions of the bottom surface of waveguide 210 in contact with
sub-assembly 100 are coated with a reflective material, e.g.,
aluminum or silver. In this way, once again, light from discrete
light source 150 is retained within waveguide 210.
[0031] Waveguide 210 may include or consist of a rigid or flexible
polymeric material, may have a substantially planar top surface
(that includes at least one region from which light is emitted
during operation). Assembly of illumination device 200 is
facilitated by the complementary geometric profiles of carrier 110
and recess 220, since, e.g., it is unnecessary to mold waveguide
210 around carrier 110 and discrete light source 150. Although
carrier 110 and recess 220 (and cap 310 described below) are
depicted as having a particular geometric profile, any number of
complementary geometric profiles are compatible with embodiments of
the present invention.
[0032] Referring to FIG. 3, in an embodiment, discrete light source
150 has at least one contact electrically connected to carrier 110
by a wire 300. For example, in an embodiment, discrete light source
150 is a "vertical" LED and has one bottom contact electrically
connected to carrier 110 as described above with reference to FIG.
1C. Additionally, vertical discrete light source 150 has a top
contact electrically connected to carrier 110 via wire 300 bonded
between the top contact and a bonding pad on the top surface of
carrier 110. Wire 300 includes or consists essentially of an
electrically conductive material, e.g., a metal such as copper or
gold. An encapsulating cap 310 may be disposed over carrier 110,
discrete light source 150, and wire 300, and may include or consist
essentially of an optically transparent material (e.g., epoxy,
silicone, or polyurethane) such that light from discrete light
source 150 efficiently couples into waveguide 210 during operation.
Cap 310 and/or carrier 110 may have a geometric profile
complementary to that of recess 220 in waveguide 210, such that
there is substantially no gap therebetween when sub-assembly 100 is
mated to waveguide 210. Further, wire 300 is the only opaque
component present in illumination device 210 between discrete light
source 150 and waveguide 210, thus enabling efficient in-coupling
of light. In order to prevent absorptive light loss, wire 300 may
be inherently reflective or coated with a reflective coating such
that light striking wire 300 may reflect into waveguide 210. In
some embodiments, discrete light source 150 has two top contacts
electrically connected to carrier 110 via wires 300.
[0033] FIG. 4A illustrates an embodiment similar to that depicted
in FIG. 3, but in which the electrical connection between carrier
110 and substrate 120 is via another wire 300. In order to
substantially prevent light loss in such an embodiment, gap 320
between carrier 110 and substrate 120 may be filled or covered by a
reflective material, e.g., a white solder mask such as PSR-400 LEW1
available from Taiyo America. Cap 310 is disposed over all wires
300 and preferably has a geometric profile complementary to that of
recess 220 in waveguide 210.
[0034] Referring to FIG. 4B, in another embodiment, wires 300 may
connect at least one contact of discrete light source 150 directly
to substrate 120 (thereby bypassing carrier 110). In this
embodiment, a portion of reflector 160 may be removed in order to
expose the electrical connection to substrate 120 (e.g., a bonding
pad). Any exposed area around the bonding pad may be covered by a
reflective material, e.g., a white solder mask such as PSR-400
LEW1.
[0035] Referring to FIGS. 5A and 5B, top surface 180 of carrier 110
is preferably reflective, in order to prevent absorptive light loss
into carrier 110. Moreover, at least one dimension of top surface
180 is as much as two, three, five, or even ten times as large as a
dimension of discrete light source 150 in order to provide more
efficient in-coupling of light into waveguide 210. The area of top
surface 180 may be as much as three, five, ten, twenty-five, or
even one hundred times as large as the top surface area of discrete
light source 150. Moreover, top surface 180 may include discrete
diffusive regions 500 and specular regions 510, arranged according
to the type of discrete light source 150 disposed thereon. For
example, FIG. 5A depicts an embodiment in which substantially all
light from discrete light source 150 is emitted from a top surface
thereof (i.e., the surface of discrete light source opposite
carrier 110). Diffusive region 500 immediately surrounding discrete
light source 150 diffusively reflects substantially all light
emitted from discrete light source 150 that back-reflects toward
discrete light source 150. Specular region 510 surrounding
diffusive region 500 specularly reflects light into waveguide 210,
essentially mimicking the total internal reflectance (and
light-confining) behavior of waveguide 210.
[0036] FIG. 5B depicts an embodiment in which discrete light source
150 emits light from not only its top surface but its side
surfaces. In such an embodiment, top surface 180 of carrier 110
includes a specular region 510 immediately surrounding discrete
light source 150, such that laterally emitted light is reflected
into waveguide 210. Surrounding this specular region 510 are the
diffusive region 500 and additional specular region 510 described
above in reference to FIG. 5A. The diffusive region 500 again
diffuses back-reflected light and the outer specular region 510
reflects light into waveguide 210. The arrangements of diffusive
regions 500 and specular regions 510 depicted in FIGS. 5A and 5B
facilitate the in-coupling of substantially all of the light
emitted by discrete light source 150 into waveguide 210.
[0037] In embodiments of the invention having multiple discrete
light sources 150 disposed on carrier 110, the discrete light
sources 150 (and/or other discrete lighting devices such as
packaged light-emitting diodes) may be connected either in series
or in parallel, depending upon the demands of the application.
FIGS. 6A and 6B schematically depict series and parallel
connections, respectively, among three discrete light sources 150.
In both embodiments depicted in FIGS. 6A and 6B, the electrical
interconnections 600 (which may be disposed in or on carrier 110
and substrate 120) associated with carrier 110 are identical, and
the series or parallel connectivity is defined by the electrical
interconnections 600 present on substrate 120. That is, it is
unnecessary to vary the production or configuration of carrier 110
based on whether discrete light sources 150 are to be ultimately
connected in series or in parallel. FIGS. 6A and 6B are schematic
drawings, and do not include features such as reflector 160,
electrical connection means 140, diffusive regions 500, and
specular regions 510, and do not indicate any geometric profile of
carrier 110. Enabling different connectivities of a plurality of
discrete light sources 150 via changes only in the electrical
interconnections 600 on substrate 120 facilitates the production of
a plurality of illumination devices 200 that include substantially
identical carriers 110 (and, perhaps, discrete light sources 150)
but which facilitate serial, parallel, or mixed serial and parallel
connections among the illumination devices 200.
[0038] Carrier 110 may, if desired, have a top surface topography
shaped to maximize the amount of light in-coupled into waveguide
210 and to minimize the amount of light absorbed or obstructed by
the discrete light sources 150 themselves. FIG. 7A depicts a
carrier 110 that includes a plurality of cavities 700 in the top
surface thereof. The cavities 700 are sized and shaped such that
the top surfaces 710 of discrete light sources 150, which have
different thicknesses, are substantially coplanar when placed on
carrier 110. In such an embodiment, the top surfaces 710 are
disposed above all other components associated with sub-assembly
100 (except for any wires connected to discrete light sources 150,
if present), enabling the efficient in-coupling of light into a
waveguide 210 with substantially no light from one discrete light
source 150 being absorbed or obstructed by any other discrete light
sources 150 present on carrier 110.
[0039] FIG. 7B depicts a plurality of top-emitting discrete light
sources 150 disposed in cavities 700 in a carrier 110. Since the
light from such discrete light sources 150 is emitted from only top
surfaces 710, only a small amount of the thickness of the discrete
light sources 150 protrudes above top surface 180 of carrier 110.
In some embodiments, cavities 700 are sized and shaped such that
top surfaces 710 of discrete light sources 150 are substantially
coplanar with top surface 180 of carrier 110, i.e., substantially
none of the thickness of discrete light sources 150 protrudes above
top surface 180.
[0040] FIG. 7C depicts a carrier 110 having a top surface 180 with
a "step" 720 (or other suitable topographical feature) sized and
shaped to enable "flip chip"-type bonding of a discrete light
source 150 having two top contacts. Such discrete light sources
150, also termed "horizontal" light sources, require contacts made
to two vertically stacked layers therein. Thus, the two "top"
contacts are actually made at slightly different heights, and the
discrete light source 150 has a stepped shape to enable contact
with the lower of the two layers. Embodiments of the invention may
include such horizontal discrete light sources 150 flipped over and
electrically coupling to contact pads 730 disposed to either side
of step 720. Thus, one or more horizontal discrete light sources
150 may be electrically connected to carrier 110 without the use of
wires that might obstruct or block emitted light.
[0041] Referring to FIG. 8, embodiments of the invention also
include an illumination device 200 having a substantially planar
interface between waveguide 210 and sub-assembly 100. In
particular, waveguide 210 may substantially lack any recess 220. In
this embodiment, top surface 180 of carrier 110 is disposed below
the top surface of substrate 120 and/or reflector 160 such that
discrete light source 150 is not disposed within waveguide 210. In
some embodiments, an optically transparent cap 310 may be disposed
over discrete light source 150 and top surface 180 of carrier 110.
The top surface of cap 310 may be substantially coplanar with the
top surface of substrate 120 and/or reflector 160 such that the
interface between waveguide 210 and sub-assembly 100 is
substantially completely planar. In such embodiments, sub-assembly
100 may be attached to waveguide 210 via an adhesive, e.g.,
transparent optical glue. Further, sidewalls 800 of substrate 120
and/or reflector 160 disposed proximate carrier 110 may also be
reflective (or coated with a reflective material) so as to reflect
rather than obstruct or absorb light from discrete light source
150.
[0042] The terms and expressions employed herein are used as terms
and expressions of description and not of limitation, and there is
no intention, in the use of such terms and expressions, of
excluding any equivalents of the features shown and described or
portions thereof. In addition, having described certain embodiments
of the invention, it will be apparent to those of ordinary skill in
the art that other embodiments incorporating the concepts disclosed
herein may be used without departing from the spirit and scope of
the invention. Accordingly, the described embodiments are to be
considered in all respects as only illustrative and not
restrictive.
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