U.S. patent application number 14/192045 was filed with the patent office on 2014-08-07 for linear illumination devices having light guides and led-based illumination modules.
The applicant listed for this patent is Anthony Catalano. Invention is credited to Anthony Catalano.
Application Number | 20140218957 14/192045 |
Document ID | / |
Family ID | 45817627 |
Filed Date | 2014-08-07 |
United States Patent
Application |
20140218957 |
Kind Code |
A1 |
Catalano; Anthony |
August 7, 2014 |
LINEAR ILLUMINATION DEVICES HAVING LIGHT GUIDES AND LED-BASED
ILLUMINATION MODULES
Abstract
In various embodiments, LED-based illumination devices include
an inlet region for receiving the LED light that is complementary
in shape to the lens of the LED.
Inventors: |
Catalano; Anthony; (Boulder,
CO) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Catalano; Anthony |
Boulder |
CO |
US |
|
|
Family ID: |
45817627 |
Appl. No.: |
14/192045 |
Filed: |
February 27, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13239620 |
Sep 22, 2011 |
8702292 |
|
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14192045 |
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61385378 |
Sep 22, 2010 |
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61385387 |
Sep 22, 2010 |
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Current U.S.
Class: |
362/555 |
Current CPC
Class: |
G02B 6/0021 20130101;
G02B 6/0041 20130101; G02B 6/003 20130101; F21K 9/61 20160801; F21Y
2103/00 20130101; G02B 6/0001 20130101; F21V 17/002 20130101; F21V
2200/00 20150115; F21Y 2103/33 20160801; F21Y 2115/10 20160801;
G02B 6/0073 20130101; F21Y 2103/30 20160801 |
Class at
Publication: |
362/555 |
International
Class: |
F21K 99/00 20060101
F21K099/00; F21V 8/00 20060101 F21V008/00 |
Claims
1.-18. (canceled)
19. An illumination device comprising: an illumination module
comprising at least one light-emitting diode (LED); disposed in
contact with the illumination module, a light guide having (i) an
inlet region for receiving light from the at least one LED, (ii) a
collimation region for collimating the received light, and (iii) an
emission region for emitting the collimated light to an ambient,
the emission region having first and second opposed surfaces
through at least one of which light is emitted, wherein (i) a shape
of the inlet region is substantially complementary to a shape of
the LED, such that substantially all light emitted from the LED
strikes the inlet region at an angle perpendicular to a surface of
the inlet region, and (ii) an axis of the collimation region
extending from the inlet region to the emission region is either
(a) inclined with respect to both the first and second surfaces of
the emission region, thereby increasing an amount of the collimated
light propagating from the collimation region that strikes the
first or second surface of the emission region without intervening
reflection, or (b) substantially parallel to both the first and
second surfaces of the emission region.
20. The illumination device of claim 19, wherein the light guide is
configured to mate with the illumination module so as to define a
gap between the surface of the inlet region and the LED.
21. The illumination device of claim 19, wherein the shape of the
inlet region is parabolic.
22. The illumination device of claim 19, wherein the shape of the
inlet region is hemispherical.
23. The illumination device of claim 19, wherein the emission
region comprises, to facilitate emission of the collimated light,
at least one of a plurality of surface discontinuities or a
plurality of scattering agents.
24. The illumination device of claim 23, wherein a density of the
at least one of a plurality of surface discontinuities or a
plurality of scattering agents increases as a function of distance
away from the at least one LED.
25. The illumination device of claim 23, wherein the emission
region comprises a plurality of surface discontinuities opposite an
emission surface from which the light is emitted.
26. The illumination device of claim 25, wherein the surface
discontinuities each have a shape of a hemisphere, a paraboloid, or
an elongated groove.
27. The illumination device of claim 25, wherein the plurality of
surface discontinuities is disposed along a portion of a perimeter
of the emission region to thereby define a width of an extent of
the light emitted from the emission region.
28. The illumination device of claim 19, wherein a cross-sectional
shape of the emission region is substantially parabolic, thereby
directing the emitted light toward an emission surface
substantially perpendicular to an axis of the parabola.
29. The illumination device of claim 19, wherein (i) a
cross-sectional shape of the emission region is substantially
trapezoidal, (ii) the first and second surfaces of the emission
region are substantially parallel, and (iii) emitted light is
emitted through one of the first or second surfaces of the emission
region.
30. The illumination device of claim 19, wherein a cross-sectional
shape of the emission region is substantially circular.
31. The illumination device of claim 19, wherein a cross-sectional
shape of the emission region is substantially elliptical.
32. The illumination device of claim 19, wherein the light emitted
from the emission region substantially replicates an emission
pattern of a fluorescent light bulb having dimensions approximately
equal to those of the illumination device.
33. The illumination device of claim 19, wherein the illumination
module is configured to be modularly attachable to a plurality of
light guides, each light guide having at least one of a different
size or shape from the others.
32. The illumination device of claim 19, wherein the illumination
module comprises at least one of a heat sink for conducting heat
from the at least one LED or driver circuitry for supplying
electrical current to the at least one LED.
34. The illumination device of claim 19, wherein the illumination
module is disposed at a first end of the light guide, and further
comprising a second illumination module disposed at a second end of
the light guide opposite the first end, the second illumination
module comprising at least one LED.
35. The illumination device of claim 19, wherein light is emitted
from the first surface and the second surface is at least one of
reflective or light-scattering.
36. The illumination device of claim 19, wherein the first and
second surfaces are substantially parallel along substantially an
entire length of the emission region.
37. The illumination device of claim 19, wherein a cross-section of
the emission region is substantially constant along substantially
an entire length of the emission region.
38. The illumination device of claim 19, wherein the light guide
comprises a solid total-internal-reflection optic.
39. The illumination device of claim 19, wherein the axis of the
collimation region extending from the inlet region to the emission
region is inclined with respect to both the first and second
surfaces of the emission region.
40. The illumination device of claim 19, wherein the axis of the
collimation region extending from the inlet region to the emission
region is substantially parallel to both the first and second
surfaces of the emission region.
41. The illumination device of claim 19, further comprising a
reflector disposed on at least one of the inlet region or the
emission region.
Description
RELATED APPLICATIONS
[0001] This application claims the benefit of and priority to U.S.
Provisional Patent Application No. 61/385,378, filed Sep. 22, 2010,
and U.S. Provisional Patent Application No. 61/385,387, filed Sep.
22, 2010, the entire disclosure of each of which is hereby
incorporated herein by reference.
FIELD OF THE INVENTION
[0002] In various embodiments, the present invention relates to
illumination devices, in particular illumination devices
incorporating light-emitting diodes.
BACKGROUND
[0003] Commonly used fluorescent lights are typically long, linear,
hollow glass tubes filled with reduced-pressure gases that, when
excited by a suitable electrical current, cause a glow discharge
(i.e., a plasma). This glow discharge produces short-wavelength
light, which in turn causes fluorescence of a coating (typically
lining the inside surface) within the tube. The light produced,
generally white for ordinary purposes, is emitted from the coating
in all directions as a diffuse glow. Because it is emitted in all
directions, fluorescent light is difficult to focus to a desired
spot, requires a reflector or other optical element that causes
substantial losses of useful light, and requires support
electronics (often referred to as a ballast) which add cost and
reduce the overall efficiency. Nonetheless, fluorescent lights are
ubiquitous due to their high electrical-to-optical efficiency.
[0004] Plasmas exhibit a peculiar property known as "negative
resistance," i.e., plasmas do not obey Ohm's Law--they do not
exhibit a linear and positive current-voltage relationship.
Instead, when an increasing voltage is applied to a fluorescent
light, very little current flows until a breakdown of the gas
occurs, reducing the apparent resistance, after which current and
voltage increase, but usually in a non-linear fashion. The ballast,
either magnetic or electronic, causes a high voltage to be
initially applied to form the plasma, but thereafter limits the
current to a suitable value. However, these electronics add bulk
and cost, reduce efficiency, and increase the probability of
failure.
[0005] Light-emitting diode (LED) technology offers a variety of
advantages when compared to fluorescent and incandescent lights,
including increased efficiency. When compared to fluorescent
lights, LEDs differ markedly in their requirements. They require
low, preferably DC voltages, typically operate at low temperature,
ordinarily below about 100.degree. C., and generally utilize a
constant current for efficient operation. However, unlike
fluorescent lights, LEDs are near point sources of light. There are
ways to diffuse light from an array of LEDs, such as the
utilization of holographic diffusers, but these may not be optimal
for all applications.
[0006] Fluorescent lights typically have an energy efficiency of
50-100 lumens per watt, although the ballast and the optical
efficiency of the fixture generally lower that considerably. LEDs
are more efficient, e.g., in the range of 100-200 lumens per watt.
And, the more directional nature of the LED light may be utilized
to avoid optical inefficiencies. The use of LEDs may also obviate
the need for a ballast, further improving the overall
efficiency.
[0007] Linear illumination devices (i.e., those having one
dimension much larger than another perpendicular dimension)
incorporating LEDs typically utilize a linear arrangement (i.e.,
along the axial length of the device) of LEDs in individual
packages including, e.g., electrical leads and focusing optics such
as lenses. Each package may contain one or more individual
semiconductor dies in a series, parallel, or series-parallel
electrical circuit. These arrangements are capable of yielding a
high lumen output but suffer from several disadvantages. First, the
use of lensed LEDs causes the light source to emit a circular light
beam unless the length of the LED array is considerably larger than
the diameter of the beam at the desired working distance. For
example, an LED with an angular distribution .theta. (theta) of
10.degree., projected from a ceiling height of 10 feet, yields a
circular light with a diameter of 5.8 feet. Therefore, the length
of the linear light source, and hence the length of the LED array
itself, must be comparable to this diameter before the light
pattern can be considered "linear."
[0008] Furthermore, the use of large numbers of individual LEDs,
while useful insofar that the heat from each LED is spatially
distributed, raises the cost of the overall product because one
must pay for the packaging of each LED. In addition to imposing a
significant cost burden, a typical linear light source based on
LEDs appears to be composed of numerous extremely bright point
sources, rather than a unitary source emitting light uniformly
across its length, which is distracting and results in deleterious
glare. While the LEDs may be covered with a diffusing screen to
"blend" the light, this diminishes optical efficiency.
[0009] Moreover, as development of LEDs matures, the light output
and energy efficiency of individual LEDs increases. Thus, over
time, fewer individual LEDs will be required to produce a given
level of illumination. While this trend may reduce overall cost, it
also implies that a desired light output necessitates a linear
array of fewer LEDs. For a given linear light source dimension, the
LEDs will be spaced further apart, further confounding the shape of
the resulting light pattern and exacerbating the above-described
issues.
[0010] In order to address these problems, light guides have been
developed to transform the light in a beneficial manner. In
general, such light guides provide illuminating light from the long
dimension of a clear solid or hollow rod while light enters the rod
from the small dimension (i.e., the "end"). Unfortunately, the
optical efficiency of such devices is very low--50% or more of the
light generated by the external light source is lost (i.e., not
emitted from the light guide), making such light guides undesirable
as means of providing high efficiency, compact, linear
lighting.
[0011] FIG. 1 depicts one origin of inefficiencies in such an
optical assembly 100. Generally, an LED 110 faces the flat face 120
of the light guide 130. Light emerging from the LED 110 generally
has a Lambertian (i.e., omnidirectional) distribution. An exemplary
light ray 140, representing a portion of the light emitted near the
plane of the LED (i.e., nearly parallel to face 120), does not
impinge upon the flat face 120 and is lost. Light emitted toward
the light guide 130 at a slightly greater angle, e.g., light ray
150, will be at least partially reflected at the flat face 120,
although a portion of the ray 150 will typically enter the light
guide 130. And, since such light enters the light guide 130 at an
angle greater than that required for total internal reflection
(TIR), this light will still emerge from the light guide 130.
However, because this light will be cut off abruptly when the
condition for TIR occurs (whether or not it is reflected from the
back surface of the rod (i.e., a reflector 160), as shown in FIG.
1), the exiting light ray 170 will form an undesirable localized
spot in the light emitted from light guide 130. (By way of example,
the sharp cutoff for a plastic rod of refractive index of 1.49 in
air occurs at 42.degree.). In contrast, the light ray 180 is
internally reflected toward reflector 160. Additionally, light that
is not reflected from the reflector 160, and which arrives at the
far surface 190 of the light guide 130 at an angle greater than
that required for total internal reflection will exit the light
guide 130 (except for a small amount reflected back at the surface
190 (not shown)), further reducing the efficiency of the optical
assembly 100.
[0012] Thus, there is a need for linear illumination devices based
on LEDs that simulate the light pattern emitted by fluorescent
lights while limiting light losses and localized spots in the
emission pattern, and that satisfy the different operating
requirements for LEDs while enabling them to function with high
efficiency.
SUMMARY
[0013] In order to improve the optical efficiency of LED-based
linear light sources substantially beyond 50% and provide a more
linear output light beam, embodiments of the invention incorporate
certain features. First, a lens (including or consisting
essentially of, e.g., an inlet and a collimation region) is
utilized to increase the optical coupling efficiency between one or
more LEDs and a linear light guide. Preferably, the lens is a solid
optic, in particular a TIR optic, formed as an integral part of the
light guide, that shapes the entrance into the bulk of the light
guide. In various embodiments, one or both ends of the light guide
are shaped. As utilized herein, the term "linear" refers to light
guides having one dimension significantly larger than another
perpendicular dimension, but such light guides are not necessarily
constrained to take the shape of a straight line. For example,
linear light guides and/or illumination devices in accordance with
embodiments of the invention may be formed into arbitrary shapes
such as U-shapes, circles, and ovals, where the light guide is
"linear" along the perimeter or length of the shape.
[0014] The shape of the lens may depend on several factors,
including the number of LEDs to be coupled thereto. In various
embodiments utilizing a single LED, the lens is shaped as a
paraboloid having a focal point at the position of the LED. The
lens is mated to (and may be an integral portion of) a linear light
guide having a cross-section (e.g., a circular, trapezoidal, or
parabolic cross-section) that is substantially constant over the
remaining length of the light guide. Preferably, the interface
(i.e., the change in cross-section) between the parabolic lens and
the light-guide bulk is smooth and continuous.
[0015] For ease and economy of fabrication, as well as for
increased light output, various embodiments feature multiple LEDs
emitting light into a single end of the light guide. The
above-described paraboloid lens may be utilized in such embodiments
incorporating multiple LEDs. However, the lens may also be shaped
as several paraboloids, one for each LED.
[0016] For LEDs (or other light sources that have a wide Lambertian
light distribution), considerable light exits close to the plane of
the semiconductor die of the LED. However, the shape of the
parabolic lens may be such that the angle of incidence of some
light is greater than the critical angle. In order to prevent the
escape of such light (which would decrease optical efficiency), the
lens may be coated with a material (e.g., a metal such as aluminum)
whose refractive index is much higher than the light guide
material. Alternatively or in combination, the shape of the lens
entrance may be blunted to an angle below the critical angle. In
preferred embodiments, the lens entrance is also a parabaloid whose
shape maintains the angle of incidence below the critical angle.
Thus, some embodiments of the invention feature a lens having a
dual-paraboloid shape, one for the entrance of the TIR lens and
another for the region coupled to the bulk of the light guide.
[0017] The lens also preferably directs incoming light from the
LED(s) such that it reflects inside the light guide as little as
possible (i.e., so as to minimize the number of internal
reflections), as each reflection may represent a loss of
efficiency. For example, light entering the light guide may reflect
from the back of the light guide and exit from the front. Thus, in
preferred embodiments, the lens is shaped to distribute the light
from the LED(s) across the back reflector as evenly as possible.
That is, the axis of the parabola (or parabolas) is preferably
inclined at such an angle to distribute light uniformly along the
length of the rear reflector. Furthermore, the rear reflector may
be faceted to redirect that light directly out of the light guide
(e.g., normal to the long axis). Alternately or in conjunction, a
Lambertian scattering material of high efficiency may be employed
as the rear reflector. Such a material distributes the light over a
wide exit angle, thus enhancing uniformity and simplifying
fabrication.
[0018] As described above, in various embodiments the rear
reflector of the light guide redirects in-coming light out of the
front face of the light guide, and the lens is designed to
illuminate this rear reflector. The rear reflector may not be an
idealized specular reflector but may rather be a Lambertian
scattering reflector of high efficiency. The reflector may have
facets (or other elements) angled to reflect the light
substantially normal to the exit face of the light guide, taking
into account the light distribution of the TIR entrance optic. The
facets of the rear reflector may take the shape of a polygon or of
a section of a spheroid, and/or the facets may be at least
partially filled with a light-scattering material. Because the
reflected light from the rear reflector is typically divergent, the
shape of the walls of the light guide may be designed to reflect
the divergent beam. Thus, the bulk of the waveguide may have a
cross-section shaped as, e.g., a parabola, in order to redirect the
emitted light. The height and width of both the front exit and rear
reflector may be calculated to achieve a light distribution of the
exit beam to meet desired output requirements. A tall, narrow,
parabolic cross-section generally gives rise to a narrow beam,
while a shallow cross-section typically yields a broader beam
profile. In various embodiments, the TIR optic is suitably shaped
to uniformly illuminate the back reflector interfaced to such
shaped light guides.
[0019] In various embodiments, light from one or more LEDs is input
to the light guide from one side only, and the opposite face of the
light guide may prevent light leakage from the light guide. For
example, a second reflector may be provided at the side opposite
the light-entrance side. The second reflector may include or
consist essentially of a material having a high index of
refraction, such as a metal, that will reflect substantially all
light impinging thereon back into the light guide. Alternately or
in combination, the shape of the opposite end may be tailored to
redirect the light to the interior and towards the back reflector,
which then redirects the light out of the light guide.
[0020] In addition, embodiments of the invention feature one or
more of: 1) power conditioning electronics to transform the line
voltage to the constant current for driving the LED(s), 2) a heat
sink to remove and dissipate the heat from the LED(s), 3) a
temperature measurement and control circuit, and 4) an optical
element to transform the LED light so that it more closely
resembles that from a fluorescent light. Fluorescent lights are
available in a variety of shapes that include linear, U-shaped,
round, and other more complex shapes. Embodiments of the invention
enable LED lights to adapt to similar configurations.
[0021] In one aspect, embodiments of the invention feature an
illumination module including or consisting essentially of an
illumination module and a light guide. The illumination module
includes or consists essentially of at least one LED having a lens.
The light guide has an inlet region for receiving light from the
LED(s), a collimation region for collimating the received light,
and an emission region for emitting the collimated light to the
ambient. The shape of the inlet region is nonplanar and
substantially complementary to the shape of the LED lens, such that
substantially all light emitted through the LED lens strikes the
inlet region at an angle perpendicular to the surface of the inlet
region.
[0022] Embodiments of the invention may include one or more of the
following, in any of a variety of combinations. The light guide may
be configured to mate with the illumination module so as to define
a gap between the surface of the inlet region and the LED lens. The
shape of the inlet region may be parabolic or hemispherical. The
shape of the collimation region may be parabolic. The axis of the
parabola may be inclined with respect to the long axis of the light
guide, thereby increasing the amount of the collimated light
propagating from the collimation region that strikes a first
surface in the emission region without intervening reflection, the
first surface being at least one of reflective or light-scattering.
Substantially all of the collimated light may strike the first
surface without intervening reflection. The at least one LED may
include or consist essentially of a single lens and a plurality of
LED dies emitting light therethrough, and the parabolic shape of
the collimation region may include or consist essentially of one
parabolic section for each of the plurality of LED dies.
[0023] In order to facilitate emission of the collimated light, the
emission region may include a plurality of surface discontinuities
and/or a plurality of scattering agents. The density of the surface
discontinuities and/or the scattering agents may increase as a
function of distance away from the LED(s). The emission region may
include a plurality of surface discontinuities opposite an emission
surface from which the light is emitted. At least one of the
surface discontinuities (or even each of them) may have the shape
of a hemisphere, a paraboloid, or an elongated groove. The
plurality of surface discontinuities may be disposed along a
portion of the perimeter of the emission region to thereby define a
width of an extent of the light emitted from the emission region.
The cross-sectional shape of the emission region may be
substantially parabolic, thereby directing the emitted light toward
an emission surface substantially perpendicular to an axis of the
parabola. The cross-sectional shape of the emission region may be
substantially trapezoidal, and the emitted light may be emitted
through a first parallel side of the trapezoidal shape longer than
the second parallel side.
[0024] The light emitted from the emission region may substantially
replicate the emission patter of a fluorescent light bulb having
dimensions approximately equal to those of the illumination device.
The illumination module may be configured to be modularly
attachable to a plurality of light guides, each light guide having
a different size and/or shape from the others. The illumination
module may include a heat sink for conducting heat from the LED(s)
and/or driver circuitry for supplying electrical current to the
LED(s). The illumination module may be disposed at a first end of
the light guide, and a second illumination module may be disposed
at a second end of the light guide opposite the first end. The
second illumination module may include one or more LEDs.
[0025] In another aspect, embodiments of the invention feature a
method of illumination. Light is emitted through a lens of an LED,
and substantially all of the light is coupled into a light guide
through an inlet region. The inlet region has a nonplanar shape
complementary to the shape of the LED lens, such that substantially
all light emitted through the LED lens strikes the inlet region at
an angle perpendicular to the surface of the inlet region. At least
a portion of the coupled light is collimated, and at least a
portion of the collimated light is emitted through the light guide
into the ambient.
[0026] These and other objects, along with advantages and features
of the invention, 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 can exist in various combinations and permutations. As used
herein, the term "substantially" means .+-.10%, and, in some
embodiments, .+-.5%. The term "consists essentially of means
excluding other materials that contribute to function, unless
otherwise defined herein. Nonetheless, such other materials may be
present, collectively or individually, in trace amounts.
BRIEF DESCRIPTION OF THE DRAWINGS
[0027] 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:
[0028] FIG. 1 is a schematic cross-section of an LED-based
illumination device accordance with the prior art;
[0029] FIG. 2 is a schematic cross-section of an LED-based linear
illumination device in accordance with various embodiments of the
invention;
[0030] FIGS. 3A-3E are schematic plan views of exemplary
configurations of illumination devices in accordance with various
embodiments of the invention;
[0031] FIGS. 4A-4E are schematic cross-sections of light guides
utilized in illumination devices in accordance with various
embodiments of the invention; and
[0032] FIG. 5 is a schematic cross-section of an LED-based linear
illumination device in accordance with various embodiments of the
invention.
DETAILED DESCRIPTION
[0033] FIG. 2 depicts an illumination device 200 in accordance with
various embodiments of the present invention. As shown,
illumination device 200 includes or consists essentially of an
illumination module 205 and an optics module 210. In general, the
illumination module 205 includes or consists essentially of one or
more LEDs 215 (and/or other discrete light sources), a support
member 220 (that may also function as a heat sink, as described
below), and driver circuitry 225 electrically connected to the LED
215. Each LED 215 preferably includes one or more LED dies 230
(each a semiconductor die featuring a light-emitting junction) and
an LED lens 235 that at least partially surrounds and preferably
encapsulates the LED die 230. The LED lens 235 is generally part of
the "package" supporting and protecting the LED die 230 and has a
shape that directs the light therefrom in a desired pattern and/or
direction. For example, the LED lens 235 may be hemispherical or
parabolic. As shown, each LED 215 is also electrically connected to
the driver circuitry 225 by, e.g., one or more wires 240 and/or
other suitable electrical connectors. One or more LEDs 215 may be
disposed on a single surface of support member 220 and/or one or
more LEDs 215 may be disposed on each of multiple surfaces of
support member 220 (as shown in FIG. 2).
[0034] The support member 220 may include or consist essentially of
any suitable rigid material and may be electrically insulated from
each LED 215. Preferably, the support member 220 is thermally
connected to one or more LEDs 215 (i.e., in the manner of a heat
sink) and conducts heat away from the LEDs 215 during their
operation. For example, the support member 220 may include fins or
other projections that increase its surface area in order to
facilitate heat conduction away from an LED 215. Support member 220
may therefore include or consist essentially of a thermally
conductive material, e.g., a metal or metal alloy, and/or may even
feature an active cooling system such as a fan.
[0035] The driver circuitry 225 converts an input power signal
(from, e.g., a DC source such as a battery or an AC source such as
an AC main) into a form suitable for driving the LED 215. Driver
circuitry 225 may also include dimmers, transformers, rectifiers,
or ballasts suitable for operation with the LED 215, as understood
by those of skill in the art. The driver circuitry 225 may be
disposed on a support, for example on a printed circuit board. The
driver circuitry 225 may also include circuitry and/or sensors to
detect or determine the operating temperature of the LED 215 and
control current and/or voltage supply thereto (based at least on
the operating temperature), e.g., as disclosed in U.S. Patent
Application Publication Nos. 2010/0320499, 2010/0176746, and
2011/0121760, the entire disclosure of each of which is
incorporated by reference herein.
[0036] The illumination module 205 is preferably modular. That is,
it is preferably designed to be utilized with various different
optics modules 210, depending upon the desired shape of the
illumination device 200 and/or the pattern or intensity of the
light desired to be emitted therefrom. For example, the
illumination module 205 may incorporate a standard socket into
which multiple different optics modules 210 may be connected. Thus,
a single illumination module 205 may be used in multiple different
applications and/or replaced without replacing other components of
a particular illumination device 200. As also described below, the
illumination module 205 and the optics module 210 preferably
collectively define a volume envelope that is substantially the
same as that of a fluorescent bulb they are intended to replace. In
such cases, the illumination device 200 may be utilized in existing
fixtures or luminaires that are sized and shaped to receive
particular fluorescent bulbs.
[0037] The optics module 210 generally includes a light guide 245
for receiving light from the LED 215 and emitting it in a desired
pattern. As mentioned previously, that desired pattern is
preferably the pattern of a fluorescent light bulb to be replaced
by illumination device 200. The light guide 245 is preferably a
solid TIR optic (including or consisting essentially of, e.g.,
plastic or glass), and may be fabricated by, e.g., injection
molding. As shown, the light guide 245 is reversibly or permanently
attached to the illumination module 205 such that light emitted by
the LED 215 is efficiently coupled into the light guide 245. In
order to enhance the efficiency of this in-coupling (by e.g.,
reducing or even substantially eliminating reflections at the inlet
250 that may result in light not being in-coupled into light guide
245), an inlet 250 of the light guide 245 preferably has a shape
complementary to that of the LED lens 235. Specifically, the shape
of the inlet 250 preferably "minors" that of LED lens 235 such that
the light emitted by the LED 215 strikes the inlet 250, across
substantially its entire surface, substantially perpendicular to
the surface of inlet 250; and in general, the shapes of the inlet
250 and the lens 235 will be nonplanar. Thus, the surface of inlet
250 may have, e.g., a substantially hemispherical or parabolic
shape. As shown in FIG. 2, there may be a gap 255 defined between
the LED lens 235 and the inlet 250, and this gap may be
substantially empty (e.g., filled with air) or at least partially
filled with an encapsulation material (preferably one having an
index of refraction substantially equal to that of the light guide
245). In other embodiments the inlet 250 and the LED lens 235 are
in contact and the gap 255 is absent. A substantially unfilled gap
255 may contribute to the modularity of the illumination device
200, as it may facilitate the attachment, removal, and replacement
of the optics module 210 from the illumination module 205. In
embodiments in which multiple LEDs 215 are emitting light into the
light guide 245, there may be a single inlet 250 for each LED 215
and in-coupling its light into the light guide 245.
[0038] Once in-coupled into the light guide 245 via the inlet 250,
the light from the LED 215 enters a collimation region 260 that
collimates (by, e.g., internal reflection) the light and increases
the uniformity of the light entering an emission region 265 of the
light guide 245 (from which the light is emitted to the ambient in
a desired pattern, as mentioned above). As shown in FIG. 2, the
collimation region 260 is preferably tapered between the inlet 250
and the emission region 265, and preferably the interface between
the collimation region 260 and the emission region 265 is
substantially seamless and smooth. In a preferred embodiment, the
collimation region 260 has the shape of one or more parabolic
sections, a shape which may collimate the in-coupled light from the
LED 215 better than other shapes. For example, the collimation
region 260 may take the shape of multiple superimposed parabolic
sections, one for each LED 215 emitting light into the light guide
245 through the inlet(s) 250 and/or one for each LED die 230
disposed within the LED 215 emitting light into the light guide 245
through an inlet 250.
[0039] Preferably, the shape of the collimation region 260 (e.g.,
in cooperation with the shape of the inlet 250) is such that the
angle of incidence of the light in-coupled at the inlet 250 strikes
the outside edge of the collimation region 260 at an angle greater
than the critical angle of light transmission from the collimation
region 260 to the outside ambient; thus, the light is confined
within the collimation region 260 by TIR. (This critical angle may
be straightforwardly determined by those of skill in the art
without undue experimentation utilizing, e.g., Snell's Law and the
indices of refraction of the collimation region 260 and the outside
ambient.) However, some embodiments of the invention utilize an
additional reflector 270 disposed along at least a portion of the
collimation region 260 in order to confine the light therein. The
reflector 270 typically has an index of refraction larger than that
of the collimation region 260 and may include or consist
essentially of, e.g., a metal or other substantially specular
reflective material. Thus, via the shape of collimation region 260
and/or the addition of reflector 270 (which may be disposed outside
or inside the collimation region 260), preferably substantially no
light is emitted to the outside ambient through the collimation
region; rather, the light is collimated therein and propagates into
the emission region 265 for emission.
[0040] The emission region 265 receives the collimated light from
the collimation region 260 and emits it to the outside ambient via,
e.g., scattering. Thus, the emission region 265 of light guide 245
preferably incorporates one or more optical elements that scatter
the light, enabling its emission from light guide 245 in a desired
pattern and/or intensity. As shown in FIG. 2, these optical
elements may include or consist of, e.g., one or more
discontinuities 275 in the surface of emission region 265 (e.g., on
the surface opposite the desired emission direction) and/or one or
more scattering agents 280 embedded within the volume of emission
region 265. The discontinuities 275 may be concave depressions in
the surface of emission region 265 shaped like, e.g., hemispheres,
facets, pyramids, or elongated grooves, and distributed along a
portion of the circumference of emission region 265 (e.g., the
portion of the circumference from which light emission is not
desired). In order to enhance scattering therefrom, one or more of
the discontinuities 275 may be partially or substantially filled
with a scattering material or coating, e.g., titanium dioxide
powder and/or white paint. (The scattering material or coating may
even be disposed on the surface of emission region 265 between the
discontinuities 275.) The scattering agents 280 may be particles,
e.g., spheres or other suitable shapes, having an index of
refraction different from that of emission region 265, and may be
"inserted" within the emission region 265 during the formation
thereof (by, e.g., injection molding, in which case the agents 280
may be dispersed colloidally in the fluid material prior to its
injection). In a preferred embodiment, the scattering agents 280
have an index of refraction lower than that of the emission region
265 (e.g., are hollow), and are substantially spherical with sizes
ranging from approximately 0.1 .mu.m to approximately 0.1 mm. In
embodiments of the invention featuring scattering agents 280 and
lacking discontinuities 275, a reflector may be disposed along at
least a portion of the surface of emission region 265 from which
light emission is not desired. As shown in FIG. 2, the density of
the discontinuities 275 and/or the scattering agents 280 may
increase as a function of distance away from the LED 215; thus, as
the amount of light within the emission region 265 decreases due to
distance from the LED 215, increasingly more of the light is
scattered and emitted from the emission region 265.
[0041] As shown in FIG. 2, a reflector 285 may be disposed at the
end of emission region 265 furthest away from the LED 215 in order
to facilitate containment of light within the light guide 245 until
it is desirably emitted from the emission region 265. Of course,
other shapes of the light guide 245 and/or arrangements of the
illumination module 205 and optics module 210 are possible in
accordance with embodiments of the present invention. FIGS. 3A-3E
depict some exemplary illumination devices 200 having a variety of
shapes and arrangements (most details of the various illumination
devices 200 depicted in FIG. 2 are omitted from FIGS. 3A-3E for
clarity). For example, FIG. 3A depicts a U-shaped optics module 210
having both ends attached to a single illumination module 205,
which thus includes at least one LED 215 disposed at each end of
the optics module 210. These LEDs 215 may share common driver
circuitry or may each have dedicated driver circuitry. FIG. 3B
depicts a similar U-shaped optics module 210 having each end
attached to a different discrete illumination module 205. FIG. 3C
depicts a circular or oval-shaped optics module 210 having both
ends attached to a single illumination module 205. (In various
embodiments, illumination devices 200 similar to that depicted in
FIG. 3C may include discrete illumination modules 205 at each end
of the shaped optics module 210.) In embodiments such as those
depicted in FIGS. 3A-3C, the emission region 265 of the
illumination module 210 may incorporate any of the optical elements
described above (e.g., discontinuities 275 and/or scattering agents
280), and these optical elements may change (e.g., increase) in
density as a function from either end of the optics module 210.
FIGS. 3D and 3E depict additional exemplary illumination devices
200 featuring straight tubular optics modules 210 and illumination
modules disposed either at one end (FIG. 3D) or both ends (FIG.
3E).
[0042] FIGS. 4A-4E schematically depict a variety of
cross-sectional shapes of the light guide 245 that may be utilized
in accordance with embodiments of the present invention, depending
upon the desired shape for the emitted light beam. FIGS. 4A-4C
depict circular and oval-shaped cross-sections having an emission
surface 400 from which the light is emitted from the emission
region 265. As shown, the illumination device 200 may incorporate
discontinuities 275 arranged along at least a portion of the
circumference of the emission region 265 opposite the emission
surface 400. In various embodiments, the width and/or focus of the
light emitted from the emission region 265 is determined at least
in part by the extent of the circumference of emission region 265
covered by the discontinuities 275. For example, fewer
discontinuities 275 spread over only a small portion of the
circumference of emission region 265 opposite emission surface 400
may result in a wider, more diffuse emitted beam. Similarly,
discontinuities 275 spread over a larger portion of the
circumference of emission region 265 may result in a thinner, more
concentrated emitted beam. FIG. 4D depicts an emission region 265
having a trapezoidal cross-section, in which the smaller parallel
side 410 of the trapezoid features discontinuities 275 and the
larger parallel side contains the emission surface 400. The angle
420 between side 410 and a side 430 may be selected to at least
partially determine the angle of distribution of the light emitted
through the emission surface 400. For example, an angle 420 of
approximately 135.degree. will define a wider emitted beam than an
angle 420 of less than 135.degree. (e.g., approximately
90.degree.). FIG. 4E depicts an emission region 265 having a
parabolic cross-section in which the emission surface 400 is
substantially perpendicular to the axis of the parabola. In such
embodiments, the emission surface 400 may be substantially planar
or curved, depending upon the desired pattern of output light. Of
course, each of the emission regions 265 may include scattering
agents 280 instead of or in addition to the discontinuities
275.
[0043] Illumination devices in accordance with embodiments of the
present invention may also be configured to minimize the number of
reflections the in-coupled light undergoes before entering the
emission region 265, as each such reflection has the potential to
reduce overall efficiency (due to, e.g., absorption or partial
reflection in an unintended direction due to microscopic
nonuniformities in the light guide 245). FIG. 5 schematically
depicts an illumination device 500 having a collimation region 510
angled to distribute the light in-coupled at inlet 250 across a
surface 520 of light guide 245 (opposite an emission surface 530
through which the light is emitted into the outside ambient) in a
highly uniform manner while minimizing the number of internal
reflections. As shown, the collimation region 510 may be shaped
similarly to the collimation region 260 previously described, e.g.,
as one or more parabolic sections, but may be arranged to collimate
the light at a non-zero angle to surface 520. That is, the axis of
the parabola(s) may be inclined relative to the surface 520 to
maximize the amount of light striking surface 520 without further
reflection after leaving collimation region 510. Thus, illumination
module 205, and the inlet 250 may also be arranged at a non-zero
angle to surface 520, as shown. The emission region 265 of the
light guide 245 may incorporate a reflector 540 on surface 520
thereof (as shown in FIG. 5), and/or may incorporate
discontinuities 275 and/or scattering agents 280 as previously
described. The reflector 540 may include or consist essentially of
a Lambertian scattering material that distributes the light over a
wide exit angle, thereby enhancing uniformity of the emitted
light.
[0044] The terms and expressions employed herein are used as terms
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, but it is
recognized that various modifications are possible within the scope
of the invention claimed.
* * * * *