U.S. patent number RE48,922 [Application Number 16/001,523] was granted by the patent office on 2022-02-01 for linear led illumination device with improved color mixing.
This patent grant is currently assigned to Lutron Technology Company LLC. The grantee listed for this patent is Lutron Technology Company LLC. Invention is credited to Fangxu Dong, Craig T. Phillips.
United States Patent |
RE48,922 |
Dong , et al. |
February 1, 2022 |
Linear LED illumination device with improved color mixing
Abstract
A linear multi-color LED illumination device that produces
uniform color throughout the output light beam without the use of
excessively large optics or optical losses is disclosed herein.
Embodiments for improving color mixing in the linear illumination
device include, but are not limited to, a shallow dome
encapsulating a plurality of emission LEDs within an emitter
module, a unique arrangement of a plurality of such emitter modules
in a linear light form factor, and special reflectors designed to
improve color mixing between the plurality of emitter modules. In
addition to improved color mixing, the illumination device includes
a light detector and optical feedback for maintaining precise and
uniform color over time and/or with changes in temperature. The
light detector is encapsulated within the shallow dome along with
the emission LEDs and is positioned to capture the greatest amount
of light reflected by the dome from the LED having the shortest
emission wavelength.
Inventors: |
Dong; Fangxu (Austin, TX),
Phillips; Craig T. (San Marcos, TX) |
Applicant: |
Name |
City |
State |
Country |
Type |
Lutron Technology Company LLC |
Coopersburg |
PA |
US |
|
|
Assignee: |
Lutron Technology Company LLC
(Coopersburg, PA)
|
Family
ID: |
53270741 |
Appl.
No.: |
16/001,523 |
Filed: |
June 6, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
Reissue of: |
14097339 |
Dec 5, 2013 |
9360174 |
Jun 7, 2016 |
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H05B
45/10 (20200101); F21V 7/0083 (20130101); F21V
7/048 (20130101); F21V 21/30 (20130101); H05B
45/22 (20200101); F21V 7/06 (20130101); F21K
9/62 (20160801); H05B 45/20 (20200101); H05B
45/00 (20200101); F21V 13/04 (20130101); F21Y
2115/10 (20160801); F21Y 2105/12 (20160801); F21Y
2105/10 (20160801); F21Y 2113/17 (20160801); F21Y
2103/00 (20130101); F21Y 2103/10 (20160801); H05B
45/18 (20200101); H05B 45/28 (20200101) |
Current International
Class: |
F21V
7/00 (20060101); F21K 99/00 (20160101); F21V
21/30 (20060101); H05B 45/22 (20200101); F21K
9/62 (20160101); H05B 45/00 (20200101); H05B
45/20 (20200101); H05B 45/10 (20200101); F21V
13/04 (20060101); F21V 7/04 (20060101); F21V
7/06 (20060101) |
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|
Primary Examiner: Lie; Angela M
Attorney, Agent or Firm: Condo Roccia Koptiw LLP
Claims
What is claimed is:
1. An illumination device, comprising: a plurality of emitter
modules spaced apart from each other and arranged in a line,
wherein each emitter module comprises an array of at least two
different colors of light emitting diodes (LEDs), which are mounted
on a substrate and encapsulated within a shallow dome, and wherein
a flattened shape of the shallow dome allows a greater portion of
light emitted by the array of LEDs to emanate sideways from the
emitter module than a hemispherical shaped dome; and a reflector
comprising a plurality of louvers, wherein each louver is centered
upon and suspended a spaced distance above a different one of the
emitter modules to focus a majority of light emitted by that
emitter module into an output beam, and wherein each louver is
configured to reflect the portion of the light that emanates
sideways from adjacent emitter modules to improve color mixing in
the output beam.
2. The illumination device as recited in claim 1, wherein a radius
of the shallow dome in a plane of the array of LEDs is 20-30%
larger than a radius of a curvature of the shallow dome, so that
the portion of the light that emanates sideways from the emitter
module exits the shallow dome at small angles relative to a plane
of the LED array.
3. The illumination device as recited in claim 2, wherein
approximately 40% of the light emitted by the array of LEDs exits
the shallow dome at approximately 0 to 30 degrees relative to the
plane of the LED array.
4. The illumination device as recited in claim 1, wherein a top
diameter of each louver is substantially larger than a bottom
diameter of the louver.
5. The illumination device as recited in claim 4, wherein the
plurality of louvers each comprise a substantially circular shape
with sloping sidewalls.
6. The illumination device as recited in claim 4, wherein the
plurality of louvers each comprise sidewalls with a substantially
parabolic shape.
7. The illumination device as recited in claim 4, wherein the
louvers are configured to focus the majority of the light emitted
by the emitter modules into the output beam by configuring the
bottom diameter of the louvers to be substantially larger than a
diameter of the emitter modules.
8. The illumination device as recited in claim 4, wherein the
sloping sidewalls of the louvers include a plurality of planar
facets, which are configured to randomize a direction of light
reflected from the planar facets.
9. The illumination device as recited in claim 4, wherein the
louvers are suspended approximately 5 mm to approximately 10 mm
above the emitter modules to allow the portion of the light that
emanates sideways from the emitter modules to mix underneath the
louvers.
10. The illumination device as recited in claim 1, wherein the
plurality of emitter modules comprise at least a first emitter
module, a second emitter module, and a third emitter module, and
wherein: the second emitter module is spaced equally distant
between the first and third emitter modules; the second emitter
module is rotated X degrees relative to the first emitter module;
the third emitter module is rotated 2X degrees relative to the
first emitter module; and wherein X is a rotational angle equal to
360 degrees divided by an integer N, where N is greater than or
equal to 3.
11. The illumination device as recited in claim 1, wherein the
array of LEDs comprises at least four LEDs, which are mounted on
the substrate close together and arranged in a square pattern near
a center of the shallow dome.
12. The illumination device as recited in claim 11, wherein the
array of LEDs comprises a red LED, a green LED, a blue LED and a
white LED.
13. The illumination device as recited in claim 1, further
comprising: an emitter housing, wherein the plurality of emitter
modules and the reflector reside within the emitter housing; and an
exit lens mounted above the reflector and attached to sidewalls of
the emitter housing.
14. The illumination device as recited in claim 13, wherein an
internal surface of the exit lens comprises a flat roughened
surface that scatters light rays passing through the exit lens, and
wherein an external surface of the exit lens comprises an array of
lenslets that randomizes the scattered light rays.
.Iadd.15. An illumination device, comprising: an emitter module
comprising: at least two light emitting diodes (LEDs) mounted on a
substrate; and a dome that encapsulates the at least two LEDs;
wherein a radius of the dome in a plane of the LEDs is greater than
a radius of curvature of the dome; and a reflector comprising a
louver that is suspended a distance above the emitter
module..Iaddend.
.Iadd.16. The illumination device of claim 15, further comprising a
plurality of emitter modules including the emitter module, wherein
the plurality of emitter modules are spaced apart from each other
and arranged in a line..Iaddend.
.Iadd.17. The illumination device of claim 15, wherein the at least
two LEDs comprise a two by two array of LEDs..Iaddend.
.Iadd.18. The illumination device of claim 15, wherein the distance
of the louver above the emitter module is within a range of
approximately 5 mm to approximately 10 mm..Iaddend.
.Iadd.19. The illumination device of claim 18, wherein the louver
comprises sloped sidewalls, and wherein the sloped sidewalls
include a plurality of planar facets..Iaddend.
.Iadd.20. The illumination device of claim 15, wherein the radius
of the dome in the plane of the LEDs is greater than the radius of
curvature of the dome by 20-30%..Iaddend.
.Iadd.21. The illumination device of claim 20, wherein
approximately 40% of light emitted by the at least two LEDs exits
the dome at approximately 0 to 30 degrees relative to the plane of
the LEDs..Iaddend.
.Iadd.22. The illumination device of claim 16, wherein the
plurality of emitter modules comprise at least a first emitter
module, a second emitter module, and a third emitter module, and
wherein: the second emitter module is between the first emitter
module and third emitter module; the second emitter module is
rotated X degrees relative to the first emitter module; the third
emitter module is rotated 2X degrees relative to the first emitter
module; and X is a rotational angle..Iaddend.
.Iadd.23. The illumination device of claim 15, wherein the louver
comprises sloped sidewalls, and wherein the sloped sidewalls
include a plurality of planar facets..Iaddend.
.Iadd.24. The illumination device of claim 15, wherein a top
diameter of the louver is larger than a bottom diameter of the
louver..Iaddend.
.Iadd.25. The illumination device of claim 24, wherein the louver
comprises a substantially circular shape..Iaddend.
.Iadd.26. The illumination device of claim 24, wherein the louver
comprises a substantially parabolic shape..Iaddend.
.Iadd.27. The illumination device of claim 24, wherein the bottom
diameter of the louver is larger than a diameter of the emitter
module..Iaddend.
.Iadd.28. The illumination device of claim 24, wherein the louver
comprises sloped sidewalls, and wherein the sloped sidewalls
include a plurality of planar facets..Iaddend.
.Iadd.29. The illumination device of claim 15, further comprising
an exit lens mounted above the reflector, wherein an internal
surface of the exit lens comprises a flat roughened surface that
scatters light rays passing through the exit lens, and wherein an
external surface of the exit lens comprises an array of lenslets
that randomizes the scattered light rays..Iaddend.
.Iadd.30. The illumination device of claim 29, further comprising a
plurality of emitter modules including the emitter
module..Iaddend.
.Iadd.31. The illumination device of claim 30, wherein the
plurality of emitter modules are spaced apart from each other and
arranged in a line, wherein the plurality of emitter modules
comprise at least a first emitter module, a second emitter module,
and a third emitter module, and wherein: the second emitter module
is between the first emitter module and third emitter module; the
second emitter module is rotated X degrees relative to the first
emitter module; the third emitter module is rotated 2X degrees
relative to the first emitter module; and X is a rotational
angle..Iaddend.
.Iadd.32. The illumination device of claim 31, wherein the distance
of the louver above the emitter module is within a range of
approximately 5 mm to approximately 10 mm..Iaddend.
.Iadd.33. The illumination device of claim 32, wherein the radius
of the dome in the plane of the LEDs is greater than the radius of
curvature of the dome by 20-30%..Iaddend.
.Iadd.34. The illumination device of claim 33, wherein a top
diameter of the louver is larger than a bottom diameter of the
louver..Iaddend.
.Iadd.35. The illumination device of claim 34, wherein the bottom
diameter of the louver is larger than a diameter of the emitter
module..Iaddend.
Description
.Iadd.CROSS-REFERENCE TO RELATED APPLICATIONS.Iaddend.
.Iadd.The present application is a reissue of U.S. Pat. No.
9,360,174, issued on Jun. 7, 2016 from U.S. application Ser. No.
14/097,339, filed Dec. 5, 2013, which is hereby incorporated by
reference herein in its entirety..Iaddend.
RELATED APPLICATIONS
This application is related to the following applications: U.S.
patent application Ser. No. 14/097,355, now U.S. Pat. No.
9,146,028; U.S. patent application Ser. Nos. 13/970,944; now issued
as U.S. Pat. No. 9,237,620; 13/970,964; 13/970,990; 12/803,805; and
12/806,118 now issued as U.S. Pat. No. 8,772,336; each of which is
hereby incorporated by reference in its entirety.
BACKGROUND
1. Field of the Invention
The invention relates to the addition of color mixing optics and
optical feedback to produce uniform color throughout the output
light beam of a multi-color linear LED illumination device.
2. Description of Related Art
Multi-color linear LED illumination devices (also referred to
herein as lights, luminaires or lamps) have been commercially
available for many years. Typical applications for linear LED
illumination devices include wall washing in which a chain of
lights attempt to uniformly illuminate a large portion of a wall,
and cove lighting in which a chain of lights typically illuminates
a large portion of a ceiling Multi-color linear LED lights often
comprise red, green, and blue LEDs, however, some products use some
combination of red, green, blue, white, and amber LEDs.
A multi-color linear LED illumination device typically includes one
or more high power LEDs, which are mounted on a substrate and
covered by a hemispherical silicone dome in a conventional package.
The light output from the LED package is typically lambertian,
which means that the LED package emits light in all directions. In
most cases, Total Internal Reflection (TIR) secondary optical
elements are used to extract the light emitted from a conventional
LED package and focus that light into a desired beam. In order to
extract the maximum amount of light, the TIR optics must have a
specific shape relative to the dome of the LED package. Other
dimensions of the TIR optics determine the shape of the emitted
light beam.
Some multi-color linear LED light products comprise individually
packaged LEDs and individual TIR optics for each LED. In order for
the light emitted from the different colored LED emitters to mix
properly, the light beams from each individual color LED must
overlap. However, because the LEDs are spaced centimeters apart,
the beams will overlap and the colors will mix only in the far
field, at some distance away from the linear light. At a very close
range to the linear light, the beams will be separate and the
different colors are clearly visible. Although such a product may
exhibit good color mixing in the far field, it does not exhibit
good color mixing in the near field.
Other multi-color linear LED light products use red, green, and
blue LEDs packaged together with a single TIR optic attached to
each RGB LED package. These RGB LED packages typically comprise an
array of three or four LEDs, which are placed as close together as
possible on a substrate and the entire array is covered by one
hemispherical dome. In products that use one TIR optical element
for each multi-color LED package, there is not necessarily a need
for the beams from the different TIR optical elements to overlap
for the colors to mix. Therefore, such products tend to have better
near field color mixing than products that use individually
packaged LEDs.
However, depending on the size of the primary and secondary optics,
the far field color mixing may actually be worse in products that
package multiple colors of LEDs together. Since the different
colored LEDs are in physically different locations within the
hemispherical silicone dome, the light radiated from the dome, and
therefore, from the TIR optical element will not be perfectly
mixed. Although larger domes and larger TIR optical elements may be
used to provide better color mixing, there are practical limits to
the size of these components, and consequently, to the near and far
field color mixing provided by such an approach.
An alternative optical system, although not commonly used, for
color mixing and beam shaping in multi-color LED linear lights uses
reflectors. In some cases, the light from a plurality of
multi-colored LED emitter packages are mixed by a diffusion element
and shaped by a concave reflector that redirects the light beams
down a wall. The diffusion element could be combined with an exit
lens or could be a shell diffuser placed over the multi-color
emitter packages, for instance. Alternatively, the system could use
a shell diffuser and a diffused exit lens. Although such systems
can achieve very good color mixing in both the near and the far
field, there is a tradeoff between color mixing and optical
efficiency. As the amount of diffusion increases, the color mixing
improves, but the optical efficiency decreases as the diffuser
absorbs and scatters more light.
As LEDs age, the light output at a given drive current changes.
Over thousands of hours, the light output from any individual LED
may decrease by approximately 10-25% or more. The amount of
degradation varies with drive current, temperature, color, and
random defect density. As such, the different colored LEDs in a
multi-color LED light will age differently, which changes the color
of the light produced by the illumination device over time. A high
quality multi-color LED light that can maintain precise color
points over time should have the means to measure the light output
from each color component, and adjust the drive current to
compensate for changes. Further, a multi-color linear light should
have the means to measure the light produced by each set of colored
LEDs independent from other sets to prevent part of the linear
light from producing a different color than other parts.
Multi-color LED linear lights with TIR optics on each individual
LED cannot achieve good color mixing in the near field. Multi-color
LED linear lights that combine a multi-color LED package with a TIR
optical element require a large TIR optical element to achieve good
color mixing in the near and far fields. Multi-color LED linear
lights that use conventional diffusers and reflectors to achieve
good color mixing in both the near and the far field suffer optical
losses. As such, there is a need for an improved optical system for
multi-color LED linear lights that provides good color mixing in
the near and far fields, is not excessively large and expensive,
and has good optical efficiency. Further, there is a need for an
optical feedback system to maintain precise color in such linear
lights. The invention described herein provides a solution.
SUMMARY OF THE INVENTION
A linear multi-color LED illumination device that produces a light
beam with uniform color throughout the output beam without the use
of excessively large optics or optical losses is disclosed herein.
In addition to improved color mixing, the illumination device
includes a light detector and optical feedback for maintaining
precise and uniform color over time and/or with changes in
temperature. The illumination device described herein may also be
referred to as a light, luminaire or lamp.
Various embodiments are disclosed herein for improving color mixing
in a linear multi-color LED illumination device. These embodiments
include, but are not limited to, a uniquely configured dome
encapsulating a plurality of emission LEDs and a light detector
within an emitter module, a unique arrangement of the light
detector relative to the emission LEDs within the dome, a unique
arrangement of a plurality of such emitter modules in a linear
light form factor, and reflectors that are specially designed to
improve color mixing between the plurality of emitter modules. The
embodiments disclosed herein may be utilized together or
separately, and a variety of features and variations can be
implemented, as desired, to achieve optimum color mixing results.
In addition, related systems and methods can be utilized with the
embodiments disclosed herein to provide additional advantages or
features. Although the various embodiments disclosed herein are
described as being implemented in a linear light form factor,
certain features of the disclosed embodiments may be utilized in
illumination devices having other form factors to improve the color
mixing in those devices.
According to one embodiment, an illumination device is disclosed
herein as including a plurality of LED emitter modules, which are
spaced apart from each other and arranged in a line. Each emitter
module may include a plurality of emission LEDs whose output beams
combine to provide a wide color gamut and a wide range of precise
white color temperatures along the black body curve. For example,
each emitter module may include four different colors of emission
LEDs, such as red, green, blue, and white LEDs. In such an example,
the red, green, and blue emission LEDs may provide saturated
colors, while a combination of light from the RGB LEDs and a
phosphor converted white LED provide a range of whites and pastel
colors. However, the emitter modules described herein are not
limited to any particular number and/or color of emission LEDs, and
may generally include a plurality of emission LEDs, which include
at least two different colors of LEDs. The plurality of LEDs may be
arranged in a two-dimensional array (e.g., a square array), mounted
on a substrate (e.g., a ceramic substrate), and encapsulated within
a dome.
In some embodiments, the linear illumination device may comprise
six emitter modules per foot, and each emitter module may be
rotated approximately 120 degrees relative to the next adjacent
emitter module. The rotation of subsequent emitters in the line
improves color mixing between adjacent emitter modules to some
degree. Although such an arrangement has been shown to provide
sufficient lumen output, efficacy, and color mixing, one skilled in
the art would understand how the inventive concepts described
herein can be applied to other combinations of LED numbers/colors
per emitter module, alternative numbers of LED emitter modules per
foot, and other angular rotations between emitter modules without
departing from the scope of the invention.
In general, an illumination device in accordance with the present
invention may include at least a first emitter module, a second
emitter module, and a third emitter module arranged in a line,
wherein the second emitter module is spaced equally distant between
the first and third emitter modules. To improve color mixing, the
second emitter module may be rotated X degrees relative to the
first emitter module, and the third emitter module may be rotated
2X degrees relative to the first emitter module. X may be
substantially any rotational angle equal to 360 degrees divided by
an integer N, where N is greater than or equal to 3.
In some embodiments, color mixing may be further improved by
covering each emitter module with an optically transmissive dome,
whose shallow or flattened shape allows a significant amount of
light emitted by the LED array to escape out of the side of the
emitter module. For example, a shallow dome may be formed with a
radius in a plane of the LED array that is about 20-30% larger than
the radius of the curvature of the shallow dome. Such a shape may
enable approximately 40% of the light emitted by the LED array to
exit the shallow dome at small angles (e.g., approximately 0 to 30
degrees) relative to the plane of the LED array.
In some embodiments, color mixing may be further improved by the
inclusion of a specially designed reflector, which is suspended
above the plurality of emitter modules. The reflector comprises a
plurality of louvers, each of which may be centered upon and
suspended a spaced distance above a different one of the emitter
modules. These louvers comprise a substantially circular shape with
sloping sidewalls, which are angled so that a top diameter of the
louver is substantially larger than a bottom diameter of the
louver. The louvers are configured to focus a majority of the light
emitted by the emitter modules into an output beam by configuring
the bottom diameter of the louvers to be substantially larger than
the diameter of the emitter modules. In some cases, the sloping
sidewalls of the louvers may include a plurality of planar facets,
which randomize the direction of light rays reflected from the
planar facets.
By suspending the louvers a spaced distance above the emitter
modules, the louvers allow the portion of the light that emanates
sideways from adjacent emitter modules to mix underneath the
louvers before that light is redirected out of the illumination
device through an exit lens. In some embodiments, the louvers may
be suspended approximately 5 mm to approximately 10 mm above the
emitter modules. Other distances may be appropriate depending on
the particular design of the emitter modules and the louvers.
In some embodiments, an exit lens may be provided with a
combination of differently textured surfaces and/or patterns on
opposing sides of the lens to further promote color mixing. For
example, an internal surface of the exit lens may comprise a flat
roughened surface that diffuses the light passing through the exit
lens. An external surface of the exit lens may comprise an array of
micro-lenses, or lenslets, to further scatter the light rays and
shape the output beam.
In some embodiments, each emitter module may also comprise a
detector, which is configured to detect light emitted by the
emission LEDs. The detector is mounted onto the substrate and
encapsulated within the shallow dome, along with the emission LEDs,
and may be an orange, red or yellow LED, in one embodiment.
Regardless of color, the detector LED is preferably placed so as to
receive the greatest amount of reflected light from the emission
LED having the shortest wavelength. For example, the emission LEDs
may include red, green, blue and white LEDs arranged in a square
array, in one embodiment. In this embodiment, the detector LED is
least sensitive to the shortest wavelength emitter LED, i.e., the
blue LED. For this reason, the detector LED is positioned on the
side of the array that is furthest from the blue LED, so as to
receive the greatest amount of light reflected off the dome from
the blue LED. In some cases, the dome may have a diffuse or
textured surface, which increases the amount of light that is
reflected off the surface of the dome back towards the detector
LED.
In addition to the emitter modules, the illumination device
described herein includes a plurality of driver circuits coupled to
the plurality of LEDs for supplying drive currents thereto. During
a compensation period, the plurality of driver circuits are
configured to supply drive currents to the plurality of emission
LEDs, one LED at a time, so that the detector LED can detect the
light emitted by each individual LED. A receiver is coupled to the
detector LED for monitoring the light emitted by each individual
LED and detected by the detector LED during the compensation
period. In some embodiments, the receiver may comprise a
trans-impedance amplifier that detects the amount of light produced
by each individual LED. Control logic is coupled to the receiver
and the driver circuits for controlling the drive currents produced
by the driver circuits based on the amount of light detected from
each LED. In some embodiments, the control logic may use optical
and/or temperature measurements obtained from the emission LEDs to
adjust the color and/or intensity of the light produced by the
illumination device over time and/or with changes in
temperature.
Various other patents and patent applications assigned to the
assignee, including U.S. Publication No. 2010/0327764, describe
means for periodically turning all but one emission LED off during
the compensation period, so that the light produced by each
emission LED can be individually measured. Other patent
applications assigned to the assignee, including U.S. patent
application Ser. Nos. 13/970,944; 13/970,964; and 13/970,990
describe means for measuring a temperature of the LEDs and
adjusting the intensity of light emitted by the LEDs to compensate
for changes in temperature. These commonly assigned patents and
patent applications are incorporated by reference in their
entirety. The invention described herein utilizes the assignee's
earlier work and improves upon the optical measurements by placing
the detector LED within the dome, and away from the shortest
wavelength LED, to ensure the light for all emission LEDs is
properly detected.
Any detector in a multi-color light source with optical feedback
should be placed to minimize interference from external light
sources. This invention places the detectors within the silicone
dome to prevent interference from external sources and other
emitter modules within the linear light. The detectors are
preferably red, orange or yellow LEDs, but could comprise silicon
diodes or any other type of light detector. However, red, orange or
yellow detector LEDs are preferable over silicon diodes, since
silicon diodes are sensitive to infrared as well as visible light,
while LEDs are sensitive to only visible light.
In some embodiments, the illumination device may further include an
emitter housing, a power supply housing coupled to the emitter
housing and at least one mounting bracket for mounting the
illumination device to a surface (e.g., a wall or ceiling) The
emitter modules, the reflector and the driver circuits described
above reside within the emitter housing. The exit lens is mounted
above the reflector and attached to sidewalls of the emitter
housing. In some embodiments, the power supply housing may be
coupled to a bottom surface of the emitter housing and comprises an
orifice through which a power cable may be routed and connected to
a power converter housed within the power supply housing. In some
embodiments, a special hinge mechanism may be coupled between the
emitter housing and the at least one mounting bracket. As described
in the commonly assigned co-pending U.S. application Ser. No.
14/097,335, the hinge mechanism allows the emitter housing to
rotate approximately 180 degrees relative to the mounting bracket
around a rotational axis of the hinge mechanism. The co-pending
application is hereby incorporated in its entirety.
DESCRIPTION OF THE DRAWINGS
Other objects and advantages of the invention will become apparent
upon reading the following detailed description and upon reference
to the accompanying drawings.
FIG. 1 is a picture of an exemplary full color gamut linear LED
light.
FIG. 2 is an exemplary illustration of the rotating hinges shown in
FIG. 1.
FIG. 3 provides additional illustration of the rotating hinge
components.
FIG. 4 is a picture of exemplary components that may be included
within the full color gamut linear LED light of FIG. 1.
FIG. 5 is an exemplary block diagram of circuitry that may be
included on the driver board and the emitter board of the exemplary
full color gamut linear LED light of FIG. 1.
FIG. 6 is an exemplary block diagram of the interface circuitry and
emitter module of FIG. 5.
FIG. 7 is an illustration of an exemplary color gamut that may be
produced by the linear LED light on a CIE1931 color chart.
FIG. 8 is a photograph of an exemplary LED emitter module
comprising a plurality of emission LEDs and a detector LED mounted
on a substrate and encapsulated in a shallow dome.
FIG. 9 is a side view drawing of the LED emitter module of FIG.
8.
FIG. 10A is a drawing of an exemplary LED emitter module depicting
a desirable placement of the emission LEDs and the detector LED
within the dome, according to one embodiment.
FIG. 10B is a drawing of an exemplary LED emitter module depicting
another desirable placement of the emission LEDs and the detector
LED within the dome, according to another embodiment.
FIG. 11 is a photograph of an exemplary emitter board comprising a
plurality of LED emitter modules, wherein sets of the modules are
rotated relative to each other to promote color mixing.
FIG. 12 is a photograph of an exemplary emitter board, emitter
housing and reflector for a full color gamut linear LED light with
a 120 degree beam angle.
FIG. 13 is a photograph of an exemplary emitter board, emitter
housing and a reflector for a full color gamut linear LED light
with a 60 degree beam angle.
FIG. 14 is an exemplary ray diagram illustrating how the shallow
dome of the emitter modules and the reflector of FIG. 13 enable
light rays from adjacent emitter modules to mix together to promote
color mixing.
FIG. 15 is an exemplary drawing providing a close up view of one of
the emitter modules and floating louvers shown in FIG. 14.
FIG. 16 is an exemplary drawing of an exit lens comprising a
plurality of lenslets formed on an external surface of the lens,
according to one embodiment.
FIG. 17 is an exemplary ray diagram illustrating the effect that
the exit lens shown in FIG. 16 has on the output beam when the
plurality of lenslets formed on the external surface is combined
with a textured internal surface.
While the invention is susceptible to various modifications and
alternative forms, specific embodiments thereof are shown by way of
example in the drawings and will herein be described in detail. It
should be understood, however, that the drawings and detailed
description thereto are not intended to limit the invention to the
particular form disclosed, but on the contrary, the intention is to
cover all modifications, equivalents and alternatives falling
within the spirit and scope of the present invention as defined by
the appended claims.
DETAILED DESCRIPTION OF THE INVENTION
Turning now to the drawings, FIG. 1 is a picture of a linear LED
lamp 10, according to one embodiment of the invention. As described
in more detail below, linear LED lamp 10 produces light over a wide
color gamut, thoroughly mixes the color components within the
output beam, and uses an optical feedback system to maintain
precise color over LED lifetime, and in some cases, with changes in
temperature. The linear LED lamp 10 shown in FIG. 1 is powered by
the AC mains, but may be powered by alternative power sources
without departing from the scope of the invention. The light beam
produced by LED lamp 10 can be symmetric or asymmetric, and can
have a variety of beam angles including, but not limited to,
120.times.120, 60.times.60, and 60.times.30. If an asymmetric beam
is desired, the asymmetric beam typically has a wider beam angle
across the length of the lamp.
In general, LED lamp 10 comprises emitter housing 11, power supply
housing 12, and rotating hinges 13. As shown more clearly in FIG.
4, and discussed below, emitter housing 11 comprises a plurality of
LED driver circuits, a plurality of LED emitter modules and a
reflector, which is mounted a spaced distance above the emitter
modules for focusing the light emitted by the emitter modules. The
power supply housing 12 comprises an AC/DC converter powered by the
AC mains, in one embodiment. Rotating hinges 13 allow both emitter
housing 11 and power supply housing 12 to rotate 180 degrees
relative to a pair of mounting brackets 14, which provides
installation flexibility. Although a pair of mounting brackets 14
are shown in FIG. 1, alternative embodiments of the LED lamp may
include a greater or lesser number of brackets, as desired.
In linear lighting fixtures, such as LED lamp 10, one major design
requirement is to have the power cable enter and exit through the
axis of rotation. This requirement allows adjacent lighting
fixtures to be independently adjusted, while maintaining a constant
distance between connection points of adjacent lighting fixtures.
However, this requirement complicates the design of the rotational
hinges used in linear lighting, as it prevents the hinges from both
rotating and passing power through the same central axis. LED lamp
10 solves this problem by moving the rotational components of the
hinge off-axis, and joining the rotational components to the
central axis with a swing arm to a rack and pinion gear assembly.
An embodiment of such a solution is shown in FIGS. 2-3 and
described below.
As shown in FIG. 2, each rotating hinge 13 may include a swing arm
15, an end cap 17 and a hinge element 16. The end cap 17 may be
configured with a flat upper surface for attachment to the emitter
housing 11 and a semi-circular inner surface comprising a plurality
of teeth. One end of the swing arm 15 is securely mounted onto the
mounting bracket 14 of the linear LED lamp 10. In some embodiments,
the swing arm 15 can be secured to the mounting bracket 14 by way
of screws 19, as shown in FIG. 3. However, alternative means of
attachment may be used in other embodiments of the invention. An
opposite end of the swing arm 15 is coupled near the flat upper
surface of the end cap 17 and is centered about the rotational axis
of the hinge mechanism. The opposite end of the swing arm comprises
a cable exit gland 18, which is aligned with the orifice of the
power supply housing for routing the power cable into the power
supply housing at the rotational axis of the hinge mechanism.
As shown in FIGS. 2 and 3, swing arm 15 houses a hinge element 16
that provides an amount of resistance needed to secure the lamp 10
in substantially any rotational position within a 180 degree range
of motion. The hinge element 16 extends outward from within the
swing arm 15 and generally comprises a position holding gear, which
is configured to interface with the toothed end cap 17 of the
linear LED lamp 10. In some embodiments, the hinge element 16 may
further comprise a constant torque element that provides a
substantially consistent amount of torque to the position holding
gear, regardless of whether the position holding gear is stationary
or in motion. In other embodiments, the constant torque element may
be replaced with a high static energy/low kinetic energy rotational
element to enable easier rotational adjustment, while still
providing the necessary resistance to hold the lamp 10 in the
desired rotational position.
The rotating hinge 13 shown in FIGS. 2-3 enables electrical wiring
(e.g., a power cable) to be routed through the rotational axis of
the rotating hinge 13 and to enter/exit the hinge at the cable exit
gland 18. In some embodiments, a strain relief member (e.g., a
nylon bushing) may be provided at the cable exit gland 18 to reduce
the amount of strain applied to the electrical wiring in response
to rotational movement about the rotational axis.
Unlike conventional lighting devices, the present invention
provides both power and rotation through the same axis by
positioning the rotational components of the hinge 13 (i.e., the
hinge element 16 and end cap 17) away from the rotational axis of
the hinge mechanism. This is achieved, in one embodiment, by
positioning the position holding gear of the hinge element 16 so
that it travels around the semi-circular inner surface of the end
cap 17 in an arc, whose radius is a fixed distance (d) away from
the rotational axis of the hinge 13.
FIG. 4 is a photograph of various components that may be included
within LED lamp 10, such as a power supply board 20, emitter
housing 11, emitter board 21, 120.times.120 degree reflector 22,
60.times.60 degree reflector 23, and exit lens 24. Although two
reflectors are shown in the photograph of FIG. 4, the assembled LED
lamp 10 would include either the 120.times.120 degree reflector 22
or the 60.times.60 degree reflector 23, but not both. Power supply
board 20 connects the LED lamp 10 to the AC mains (not shown) and
resides in power supply housing 12 (shown in FIG. 1). Power supply
board 20 provides DC power and control to emitter board 21, which
comprises the emitter modules and driver circuits. Emitter board 21
resides inside emitter housing 11 and is covered by either
reflector 22 or reflector 23. The exit lens 24 is mounted above the
reflector 22/23 and attached to the sidewalls of the emitter
housing 11. As shown in FIG. 1, the exit lens 24 is configured such
that the external surface of the lens is substantially flush with
the top of the sidewalls of the emitter housing. As described in
more detail below, exit lens 24 may comprise an array of small
lenses (or lenslets) on the external surface of the exit lens to
improve color mixing and beam shape.
FIGS. 1 and 4 illustrate one possible set of components for a
linear LED lamp 10, in accordance with the present invention. Other
embodiments of linear LED lights could have substantially different
components and/or dimensions for different applications. For
instance, if LED lamp 10 was used for outdoor wall washing, the
mechanics, optics and dimensions could be significantly different
than those shown in FIGS. 1 and 4. As such FIGS. 1 and 4 provide
just one example of a linear LED lamp.
FIG. 5 is an exemplary block diagram for the circuitry included on
power supply board 20 and emitter board 21. Power supply board 20
comprises AC/DC converter 30 and controller 31. AC/DC converter 30
converters AC mains power to a DC voltage of typically 15-20V,
which is then used to power controller 31 and emitter board 21.
Each such block may further regulate the DC voltage from AC/DC
converter 30 to lower voltages as well. Controller 31 communicates
with emitter board 21 through a digital control bus, in this
example. Controller 31 could comprise a wireless, powerline, or any
other type of communication interface to enable the color of LED
lamp 10 to be adjusted. In the illustrated embodiment, emitter
board 21 comprises six emitter modules 33 and six interface
circuits 32. Interface circuits 32 communicate with controller 31
over the digital control bus and produce the drive currents
supplied to the LEDs within the emitter modules 33.
FIG. 6 illustrates exemplary circuitry that may be included within
interface circuitry 32 and emitter modules 33. Interface circuitry
32 comprises control logic 34, LED drivers 35, and receiver 36.
Emitter module 33 comprises emission LEDs 37 and a detector 38.
Control logic 34 may comprise a microcontroller or special logic,
and communicates with controller 31 over the digital control bus.
Control logic 34 also sets the drive current produced by LED
drivers 35 to adjust the color and/or intensity of the light
produced by emission LEDs 37, and manages receiver 36 to monitor
the light produced by each individual LED 37 via detector 38. In
some embodiments, control logic 34 may comprise memory for storing
calibration information necessary for maintaining precise color, or
alternatively, such information could be stored in controller
31.
According to one embodiment, LED drivers 35 may comprise step down
DC to DC converters that provide substantially constant current to
the emission LEDs 37. Emission LEDs 37, in this example, may
comprise white, blue, green, and red LEDs, but could include
substantially any other combination of colors. LED drivers 35
typically supply different currents (levels or duty cycles) to each
emission LED 37 to produce the desired overall color output from
LED lamp 10. In some embodiments, LED drivers 35 may measure the
temperature of the emission LEDs 37 through mechanisms described,
e.g., in pending U.S. patent application Ser. Nos. 13/970,944;
13/970,964; 13/970,990; and may periodically turn off all LEDs but
one to perform optical measurements during a compensation period.
The optical and temperature measurements obtained from the emission
LEDs 37 may then be used to adjust the color and/or intensity of
the light produced by the linear LED lamp 10 over time and with
changes in temperature.
FIG. 7 is an illustration of an exemplary color gamut produced with
the red, green, blue, and white emission LEDs 37 included within
linear LED lamp 10. Points 40, 41, 42, and 43 represent the color
produced by the red, green, blue, and white LEDs 37 individually.
The lines 44, 45, and 46 represent the boundaries of the colors
that this example LED lamp 10 could produce. All colors within the
triangle formed by 44, 45, and 46 can be produced by LED lamp
10.
FIG. 7 is just one example of a possible color gamut that can be
produced with a particular combination of multi-colored LEDs.
Alternative color gamuts can be produced with different LED color
combinations. For instance, the green LED within LEDs 37 could be
replaced with another phosphor converted LED to produce a higher
lumen output over a smaller color gamut. Such phosphor converted
LEDs could have a chromaticity in the range of (0.4, 0.5) which is
commonly used in white plus red LED lamps. Additionally, cyan or
yellow LEDs could be added to expand the color gamut. As such, FIG.
7 illustrates just one exemplary color gamut that could be produced
with LED lamp 10.
Detector 38 may be any device, such as a silicon photodiode or an
LED, that produces current indicative of incident light. In at
least one embodiment, however, detector 38 is preferably an LED
with a peak emission wavelength in the range of approximately 550
nm to 700 nm. A detector 38 with such a peak emission wavelength
will not produce photocurrent in response to infrared light, which
reduces interference from ambient light. In at least one preferred
embodiment, detector 38 may comprise a small red, orange or yellow
LED.
Referring back to FIG. 6, detector 38 is connected to a receiver
36. Receiver 36 may comprise a trans-impedance amplifier that
converts photocurrent to a voltage that may be digitized by an ADC
and used by control logic 34 to adjust the drive currents, which
are supplied to the emission LEDs 37 by the LED drivers 35. In some
embodiments, receiver 36 may further be used to measure the
temperature of detector 38 through mechanisms described, e.g., in
pending U.S. patent application Ser. Nos. 13/970,944, 13/970,964,
13/970,990. This temperature measurement may be used, in some
embodiments, to adjust the color and/or intensity of the light
produced by the linear LED lamp 10 over changes in temperature.
FIG. 5 and FIG. 6 are just examples of many possible block diagrams
for power supply board 20, emitter board 21, interface circuitry
32, and emitter module 33. In other embodiments, interface
circuitry 32 could be configured to drive more or less LEDs 37, or
may have multiple receiver channels. In yet other embodiments,
emitter board 21 could be powered by a DC voltage, and as such,
would not need AC/DC converter 30. Emitter module 33 could have
more or less LEDs 37 configured in more or less chains, or more or
less LEDs per chain. As such, FIG. 5 and FIG. 6 are just
examples.
FIGS. 8-9 depict an exemplary emitter module 33 that may be used to
improve color mixing in the linear LED lamp 10. As shown in FIG. 8,
emitter module 33 may include an array of four emission LEDs 37 and
a detector 38, all of which are mounted on a common substrate 70
and encapsulated in a dome 71. In one embodiment, the substrate 70
may be a ceramic substrate formed from an aluminum nitride or an
aluminum oxide material (or some other reflective material) and may
generally function to improve output efficiency by reflecting light
back out of the emitter module 33.
The dome 71 may comprise substantially any optically transmissive
material, such as silicone or the like, and may be formed through
an overmolding process, for example. In some embodiments, a surface
of the dome 71 may be lightly textured to increase light scattering
and promote color mixing, as well as to reflect a small amount
(e.g., about 5%) of the emitted light back toward the detector 38
mounted on the substrate 70. The size of the dome 71 (i.e., the
diameter of the dome in the plane of the LEDs) is generally
dependent on the size of the LED array. However, it is generally
desired that the diameter of the dome be substantially larger
(e.g., about 1.5 to 4 times larger) than the diameter of the LED
array to prevent occurrences of total internal reflection. As
described in more detail below, the size and shape (or curvature)
of the dome 71 is specifically designed to enhance color mixing
between the plurality of emitter modules 33.
FIG. 9 depicts a side view of the emitter module 33 to illustrate a
desired shape of the dome 71, according to one embodiment of the
invention. As noted above, conventional emitter modules typically
include a dome with a hemispherical shape, in which the radius of
the dome in the plane of the LED array is the same as the radius of
the curvature of dome. As shown in FIG. 9, dome 71 does not have
the conventional hemispherical shape, and instead, is a much
flatter or shallower dome. In general, the radius (r.sub.dome) of
the shallow dome 71 in the plane of the LED array is approximately
20-30% larger than the radius (r.sub.curve) of the curvature of
dome 71.
In one example, the radius (r.sub.dome) of the shallow dome 71 in
the plane of the LEDs may be approximately 4.8 mm and the radius
(r.sub.curve) of the dome curvature may be approximately 3.75 mm.
The ratio of the two radii (4.8/3.75) is 1.28, which has been shown
to provide the best balance between color mixing and efficiency for
at least one particular combination and size of LEDs. However, one
skilled in the art would understand how alternative radii and
ratios may be used to achieve the same or similar color mixing
results.
By configuring the dome 71 with a substantially flatter shape, the
dome 71 shown in FIGS. 8-9 allows a larger portion of the emitted
light to emanate sideways from the emitter module 33. Stated
another way, a shallower dome 71 allows a significant portion of
the emitted light to exit the dome at small angles
(.alpha..sub.side) relative to the horizontal plane of the LED
array. In one example, the shallower dome 71 may allow
approximately 40% of the light emitted by the array of LEDs 37 to
exit the shallow dome at approximately 0 to 30 degrees relative to
the horizontal plane of the LED array. In comparison, a
conventional hemispherical dome may allow only 25% (or less) of the
emitted light to exit between 0 and 30 degrees. As described in
more detail below with reference to FIGS. 14-15, the shallow dome
71 shown in FIGS. 8-9 improves color mixing in the linear LED lamp
10 by allowing a significant portion (e.g., 40%) of the light
emitted from the sides of adjacent emitter modules to intermix
before that light is reflected back out of the lamp.
FIGS. 10A-10B are exemplary drawings of the emitter module 33 shown
in FIGS. 8-9 including emission LEDs 37 and detector 38 within
shallow dome 71. As shown in FIGS. 10A-10B, the four differently
colored (e.g., red, green, blue and white) emission LEDs 37 are
arranged in a square array and are placed as close as possible
together in the center of the dome 71, so as to approximate a
centrally located point source. As noted above, it is generally
desired that the diameter (d.sub.dome) of the dome 71 in the plane
of the LEDs is substantially larger than the diameter (d.sub.array)
of the LED array to prevent occurrences of total internal
reflection. In one example, the diameter (d.sub.dome) of the dome
71 in the plane of the LEDs may be approximately 7.5 mm and the
diameter (d.sub.array) of the LED array may be approximately 2.5
mm. Other dimensions may be appropriate in other embodiments of the
invention.
FIGS. 10A-10B also illustrate exemplary placements of the detector
38 relative to the array of emission LEDs 37 within the shallow
dome 71. As shown in the embodiment of FIG. 10A, the detector 38
may be placed closest to, and in the middle of, the edge of the
array that is furthest from the short wavelength emitters. In this
example, the short wavelength emitters are the green and blue LEDs
positioned at the top of the array, and the detector 38 is an
orange LED, which is least sensitive to blue light. Although
somewhat counterintuitive, it is desirable to place the detector 38
as far away as possible from the blue LED so as to gather the most
light reflected off the surface of the shallow dome 71 from the
blue LED. As noted above, a surface of the dome 71 may be lightly
textured, in some embodiments, so as to increase the amount of
emitted light that is reflected back to the detector 38.
FIG. 10B illustrates an alternative placement for the detector 38
within the shallow dome 71. In some embodiments, the best place for
the detector 38 to capture the most light from the blue LED may be
on the other side of the array, and diagonally across from, the
blue LED. In the embodiment shown in FIG. 10B, the detector 38 is
preferably placed somewhere between the dome 71 and a corner of the
red LED. Since the green LED produces at least 10.times. the
photocurrent as the blue LED on the orange detector, FIG. 10B
represents an ideal location for an orange detector 38 in relation
to the particular RGBW array 37 described above. However, the
detector 38 may be positioned as shown in FIG. 10A, without
sacrificing detection accuracy, if there is insufficient space
between the dome 71 and the corner of the red LED, as shown in FIG.
10B.
FIG. 11 illustrates an exemplary emitter board 21 comprising six
emitter modules 100, 101, 102, 103, 104, and 105 arranged in a
line. Each of the emitter modules shown in FIG. 11 may be identical
to the emitter module 33 shown in FIGS. 8-10 and described above.
FIG. 11 illustrates a preferred method for altering the orientation
of emitter modules, or sets of emitter modules, to further improve
color mixing there between. In the embodiment of FIG. 11, the
orientation of emitter modules 102 and 105 (i.e., a first set of
emitter modules) is the same, the orientation of emitter modules
101 and 104 (i.e., a second set of emitter modules) is the same,
and the orientation of emitter modules 100 and 103 (i.e., a third
set of emitter modules) is the same. However, the orientation of
the second set of emitter modules 101 and 104 is rotated 120
degrees from that of the first set of emitter modules 102 and 105.
Likewise, the orientation of the third set of emitter modules 100
and 103 is rotated 120 degrees from that of the second set of
emitter modules 101 and 104, and 240 degrees from the first set of
emitter modules 102 and 105. This rotation in combination with the
shallow curvature of dome 71 enables the various colors of light
produced by the plurality of emitter modules 100, 101, 102, 103,
104, and 105 to thoroughly mix.
FIG. 11 is just one example of an emitter board 21 that may be used
to improve color mixing in a linear LED lamp 10. Although the
emitter board 21 is depicted in FIG. 11 with six emitter modules
spaced approximately 2 inches apart, an emitter board 21 in
accordance with the present invention could have substantially any
number of emitter modules spaced substantially any distance apart.
In embodiment shown in FIG. 11, three sets of emitter modules are
rotated 120 degrees from each other. In other embodiments, however,
one or more of the emitter modules could be rotated by any amount
provided that the emitter modules on the emitter board 21 make an
integer number of rotations along the length of emitter board
21.
For example, each emitter module may be rotated an additional X
degrees from a preceding emitter module in the line. Generally
speaking, X is a rotational angle equal to 360 degrees divided by
an integer N, where N is greater than or equal to 3. The number N
is dependent on the number of emitter modules included on the
emitter board. For instance, with six emitter modules, each module
could be rotated 60 or 120 degrees from the preceding emitter
module. With eight emitter modules, each module could be rotated an
additional 45 or 90 degrees. For best color mixing, the rotational
angle X should be equal to 360 degrees divided by three or four
depending on how many emitter modules are included on the emitter
board 21.
FIG. 12 is a photograph of the emitter board 21 and reflector 22
placed within the emitter housing 11 of the linear LED lamp 10. In
particular, FIG. 12 illustrates an exemplary placement of the
emitter modules 33 and reflector 22 within emitter housing 11 for
120.times.120 degree beam applications. As noted above with regard
to FIG. 11, each set of emitter modules 33 (e.g., modules 102/105,
101/104 and 100/103 shown in FIG. 11) may be rotated 120 degrees
relative to each other to improve color mixing. In the embodiment
of FIG. 12, the reflector 22 comprises a highly reflective material
(e.g., vacuum metalized aluminum) that covers the entire inside of
the emitter housing 11 except for the emitter modules 33. The
reflector 22 used in this embodiment improves the overall optical
efficiency of the lamp 10 by reflecting light scattered off the
exit lens The rotation of the emitter modules 33, the shallow dome
71, and the shape of the exit lens 24 (discussed below) all
contribute to produce thorough color mixing throughout the
120.times.120 beam in this example.
FIG. 13 is a photograph of the emitter board 21 and reflector 23
placed within the emitter housing 11. In particular, FIG. 13
illustrates an exemplary placement of the emitter modules 33 and
reflector 23 within emitter housing 11 for 60.times.60 degree beam
applications. As in FIG. 12, the sets of emitter modules 33 may be
rotated 120 degrees relative to each other to improve color mixing.
Like reflector 22, reflector 23 also comprises a highly reflective
material (e.g., vacuum metalized aluminum) to improve optical
efficiency, however, reflector 23 additionally includes a plurality
of louvers, each of which is centered around and suspended above a
different one of the emitter modules 33. As depicted more clearly
in FIGS. 14-15, the louvers are attached to the reflector 23 only
on the sides and ends, and are open below. The space between the
emitter modules 33 and the bottom of the louvers allows light
emitted sideways from the emitter modules 33 to intermix to improve
color uniformity in the output beam.
FIG. 14 is an exemplary ray diagram illustrating the color mixing
effect between emitter modules 100-105 and reflector 23. As shown
in FIG. 14, louvers 110, 111, 112, 113, 114, and 115 are
individually centered upon and positioned above a different emitter
module. The louvers 110-115 focus a majority of the light emitted
from the emitter modules 100-105 into an output beam, but allow
some of the light that emanates from the side of the emitter
modules 100-105 to mix with light from other emitter modules. For
example, louver 112 focuses most of the light emitted from emitter
module 102 into the output beam, however, some rays from emitter
module 102 are reflected by louvers 111, 113, and 115. Likewise,
louver 113 focuses most of the light emitted from emitter module
103; however, some rays from emitter module 103 are reflected by
louvers 110, 112, and 114. The exemplary ray diagram of FIG. 14
illustrates only a limited number of rays. In reality, each louver
110-115 reflects some light from all emitter modules 100-105, which
significantly improves color mixing in the resulting beam.
FIG. 15 illustrates a cross section of a portion of the exemplary
60.times.60 degree reflector 23 comprising louver 110 and emitter
module 100. Louver 110 is attached to both lateral sides of
reflector 23. The same is true for louvers 111-115. Additionally,
louvers 110 and 115 are attached to the ends of reflector 23. In
some embodiments, the louvers 110-115 may be attached to the
sidewalls and ends of the reflector 23 by forming the louvers and
reflector as one integral piece (e.g., by a molding process). Other
means for attachment may be used in other embodiments of the
invention.
The overall shape and size of the louvers 110-115 determine the
shape, and to some extent the color, of the output beam. As shown
in FIGS. 13-15, each louver has a substantially round or circular
shape with sloping sidewalls. As shown in FIG. 15, the sidewalls of
the louvers are angled outward, such that the diameter at the
bottom of the louver (d.sub.bottom) is substantially smaller than
the diameter at the top of the louver (d.sub.top). It is generally
desired that the louvers 110-115 be substantially larger than the
emitter modules 100-105, so that the louvers may focus a majority
of the light emitted by the emitter modules into an output beam. As
noted above, the diameter of the emitter module (d.sub.emit) may be
about 7.5 mm, in one embodiment. In such an embodiment, the bottom
diameter (d.sub.bottom) of the louver may be about 35 mm and the
top diameter (d.sub.top) of the louver may be about 42 mm. Other
dimensions and shapes may be appropriate in other embodiments of
the invention. In one alternative embodiment, for example, the
louvers may alternatively be configured with a substantially
parabolic shape, as would be appropriate in 30.times.60 beam
applications.
As further depicted in FIG. 15, the angle (.alpha..sub.ref) of the
sidewalls of reflector 23 is substantially the same as the angle
(.alpha..sub.ref) of the sidewalls of the louvers 110-115.
According to one embodiment, the angle of the sidewall surfaces of
the reflector 23 and the angle of the louvers 110-115 may be
approximately 60 degrees. In the illustrated embodiment, the shape
and size of the reflector and louvers are chosen for 60.times.60
beam applications. One skilled in the art would understand how
alternative shapes and sizes may be used to produce other beam
shapes. As such, FIGS. 13-15 are just example illustrations of the
invention.
As further shown in FIG. 15, the louvers (e.g., 110) are formed so
as to include a plurality of planar facets, or lunes 116, in the
sidewalls. Lunes 116 are flattened segments in the otherwise round
louvers 110-115. The lunes 116 generally function to randomize the
direction of the light rays and improve color mixing. FIG. 15
further depicts how the louvers (e.g., 110) are suspended some
height (h) above the emitter modules (e.g., 100). The height (h) is
generally dependent on the shape of the shallow dome 71 and the
configuration of the lunes 116. According to one embodiment, the
louvers 110-115 may be suspended approximately 5 mm to
approximately 10 mm above the emitter modules 100-105 to allow a
sufficient amount of light to mix underneath the louvers.
In addition the features described above (e.g., the flattened dome
shape, the rotated emitter modules, the reflector with floating
louvers, etc.), the exit lens 24 of the linear LED lamp 10 provides
an additional measure of color mixing and beam shaping for the
output beam. In general, the exit lens 24 is preferably configured
with some combination of differently textured surfaces and/or
patterns on opposing sides of the exit lens. The exit lens 24
preferably comprises injection modeled PMMA (acrylic), but could
comprise substantially any other optically transparent
material.
FIGS. 16 and 17 illustrate one exemplary embodiment of an exit lens
24 comprising an internal surface having a flat roughened surface
that diffuses the light passing through the exit lens, and an array
of micro-lenses or lenslets 120 formed on an external surface of
the lens. As shown in FIG. 16, the lenslets 120 may be rectangular
or square-shaped domes, and may be approximately 1 mm square, but
could have a variety of other shapes and sizes. The curvature of
lenslets 120 is defined by the radius of the arcs that create the
lenslets. In one embodiment, the radius of the lenslets 120 is
about 1 mm. Although any combination of size, shape and curvature
of lenslets 120 is possible, such dimensions have been shown to
provide optimum color mixing and beam shaping performance.
FIG. 16 is just one example of an exit lens 24. One skilled in the
art would understand how an exit lens may be alternatively
configured to produce the same or similar color mixing results. In
other embodiments, for example, the pattern on the exterior surface
of the exit lens could be hexagonal instead of rectangular, and/or
the diameter of the lenslets 120 could be different. Likewise, the
curvature of the lenslets 120 could change significantly and still
achieve the desired results. In general, the exit lens 24 described
herein may provide improved color mixing with substantially any
shape, any diameter, and any lenslet curvature by providing an
array of lenslets on at least one side of the exit lens 24. In some
embodiments, an array of similarly or differently configured
lenslets may also be provided on the interior surface of the exit
lens.
FIG. 17 illustrates a ray diagram for the exemplary exit lens 24
shown in FIG. 16. In this example, the light rays 130 from the
emitter modules 33 enter the exit lens 24 through the flat
roughened internal side and are diffused within the exit lens 24.
The scattered light rays within the exit lens 24 are further
randomized by the array of lenslets 120 formed on the external side
of the exit lens to produce an output beam 131 with substantially
uniform color throughout the beam.
It will be appreciated to those skilled in the art having the
benefit of this disclosure that this invention is believed to
provide color mixing optics and optical feedback to produce uniform
color throughout the output light beam of a multi-color linear LED
illumination device. More specifically, the invention provides an
emitter module comprising a plurality of emission LEDs and a
detector LED, all of which are mounted on a substrate and
encapsulated in a shallow dome. The shallow dome allows a
significant portion of the emitted light to emanate from the side
of the emitter module, where it can mix with light from other
emitter modules to improve color mixing. The invention further
improves color mixing within a multi-color linear LED illumination
device by rotating sets of the emitter modules relative to each
other and providing a reflector comprising a plurality of floating
louvers, which are centered upon and suspended above each of the
emitter modules. The floating louvers allow a portion of the light
emitted from each emitter module to mix with light from other
emitter modules to produce uniform color throughout the resulting
output beam. Further modifications and alternative embodiments of
various aspects of the invention will be apparent to those skilled
in the art in view of this description. It is intended that the
following claims be interpreted to embrace all such modifications
and changes and, accordingly, the specification and drawings are to
be regarded in an illustrative rather than a restrictive sense.
* * * * *