U.S. patent application number 13/843443 was filed with the patent office on 2014-06-19 for thermal path for heat dissipation in a linear light module.
This patent application is currently assigned to Lumenetix, Inc.. The applicant listed for this patent is LUMENETIX, INC.. Invention is credited to Dustin Cochran, Herman Ferrier, Sanjoy Ghose.
Application Number | 20140169026 13/843443 |
Document ID | / |
Family ID | 50930108 |
Filed Date | 2014-06-19 |
United States Patent
Application |
20140169026 |
Kind Code |
A1 |
Cochran; Dustin ; et
al. |
June 19, 2014 |
THERMAL PATH FOR HEAT DISSIPATION IN A LINEAR LIGHT MODULE
Abstract
A linear light module that uses a thermally conductive housing
for dissipating heat generated by a lighting source within the
housing is described. Light is thermally coupled away from the
lighting source via a thermally conductive heating block. The
heating block is thermally coupled to a thermally conductive heat
pipe that runs along the length of the housing, where the length of
the housing is substantially the same length as the linear light
module. The housing is extruded to include a channel that runs the
length of the housing for holding the heat pipe. Because the
housing is long, the heat is easily conducted from the housing.
Inventors: |
Cochran; Dustin; (Boulder
Creek, CA) ; Ferrier; Herman; (Scotts Valley, CA)
; Ghose; Sanjoy; (Scotts Valley, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
LUMENETIX, INC. |
Scotts Valley |
CA |
US |
|
|
Assignee: |
Lumenetix, Inc.
Scotts Valley
CA
|
Family ID: |
50930108 |
Appl. No.: |
13/843443 |
Filed: |
March 15, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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61737776 |
Dec 15, 2012 |
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|
61737777 |
Dec 15, 2012 |
|
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61737779 |
Dec 15, 2012 |
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61737780 |
Dec 15, 2012 |
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Current U.S.
Class: |
362/555 ;
29/592.1; 362/580 |
Current CPC
Class: |
F21K 9/60 20160801; F21V
29/75 20150115; F21Y 2103/00 20130101; F21S 2/00 20130101; F21V
21/005 20130101; G02B 6/0006 20130101; F21Y 2113/13 20160801; G02B
5/0268 20130101; G02B 6/46 20130101; G02B 5/02 20130101; Y10T
29/49002 20150115; H05B 45/22 20200101; H05B 45/00 20200101; F21Y
2115/10 20160801; H05B 45/20 20200101; G02B 6/0096 20130101 |
Class at
Publication: |
362/555 ;
362/580; 29/592.1 |
International
Class: |
F21V 8/00 20060101
F21V008/00; G02B 6/46 20060101 G02B006/46; F21V 29/00 20060101
F21V029/00 |
Claims
1. A system comprising: a lighting source that generates heat; a
light guide configured to couple light generated by the lighting
source and to emit the light in an elongated configuration along a
length of the light guide; a thermally conductive heat pipe
thermally coupled to the lighting source, wherein the heat pipe is
substantially parallel to the light guide; a housing for the
lighting source, the light guide, and the heat pipe, wherein the
housing is thermally coupled to the heat pipe along a length of the
heat pipe, and further wherein at least a portion of the heat
generated by the lighting source is dissipated by the housing.
2. The system of claim 1, wherein the lighting source includes
multiple light emitting diodes (LEDs), wherein the multiple LEDs
emit light at more than one peak wavelength, and further wherein
the emitted light along the length of the light guide appears
uniform in color.
3. The system of claim 1, further comprising a thermally conductive
heat transfer block, wherein the lighting source is thermally
coupled to the thermally conductive heat transfer block, and
further wherein the thermally conductive heat transfer block is
thermally coupled to the heat pipe.
4. The system of claim 1, wherein the housing is made from a
thermally conductive material.
5. The system of claim 1, wherein the housing includes a channel
for holding the heat pipe, and the channel thermally couples the
housing and the heat pipe.
6. The system of claim 5, wherein the housing is extruded.
7. The system of claim 1, wherein the light guide is at least one
foot long.
8. The system of claim 7, wherein the housing is approximately a
same length as the light guide.
9. The system of claim 8, wherein the heat pipe is approximately a
same length as the housing.
10. A system comprising: a lighting source that generates heat; a
light guide configured to couple light generated by the lighting
source and to emit the light in an elongated configuration along a
length of the light guide, wherein the light guide has a recessed
registration guide; a housing for the light guide and the lighting
source, wherein the housing has a registration bump configured to
match a shape of the recessed registration guide, wherein the
registration bump is located within the recessed registration guide
to fix a position of the light guide relative to the housing, and
further wherein the light guide and the housing have different
thermal coefficients of expansion.
11. The system of claim 10, wherein the light guide can thermally
expand in a first direction along a length of the light guide at a
thermal expansion rate different from the housing while maintaining
the registration bump within the recessed registration guide.
12. The system of claim 11, wherein the light guide can thermally
expand in a second direction at a thermal expansion rate different
from the housing while maintaining the registration bump within the
recessed registration guide, wherein the second direction is
substantially perpendicular to the first direction.
13. The system of claim 12, wherein the light guide is clamped by
the housing in a third direction which limits thermal expansion of
the light guide in the third direction, wherein the third direction
is substantially perpendicular to the first direction and the
second direction.
14. The system of claim 10, wherein the registration bump is
hemispherical.
15. The system of claim 10, wherein the lighting source is
thermally coupled to the housing, and at least a portion of the
heat generated by the lighting source is dissipated by the
housing.
16. The system of claim 10, wherein the lighting source includes
multiple light emitting diodes (LEDs), wherein the multiple LEDs
emit light at more than one peak wavelength, and further wherein
the emitted light along the length of the light guide appears
uniform in color.
17. The system of claim 10, wherein the light guide is at least one
foot long.
18. The system of claim 17, wherein the housing is approximately a
same length as the light guide.
19. The system of claim 10, wherein the housing is made from a
thermally conductive material.
20. A system comprising: means for generating light, wherein the
means for generating light also generates heat; means for coupling
light generated by the lighting source and emitting the light in an
elongated configuration; a thermally conductive heat pipe thermally
coupled to the means for generating light, wherein the heat pipe is
substantially parallel to the light guide; a housing for the means
for generating light, the means for coupling light and emitting the
light, and the heat pipe, wherein the housing is thermally coupled
to the heat pipe along a length of the heat pipe, and further
wherein at least a portion of the heat generated by the means for
generating light is dissipated by the housing.
21. A method of removing heat from a linear light module, wherein
the linear light module has a lighting source near a first end, and
the linear light module emits light from an emission surface along
a length of the linear light module, the method comprising:
conducting heat away from the lighting source via a heat transfer
block; conducting heat away from the heat transfer block via a heat
pipe coupled to the heat transfer block, wherein the heat pipe is
substantially parallel to the emission surface of the linear light
module; conducting heat away from the heat pipe via a housing for
the linear light module, wherein the heat pipe and the housing are
coupled along the length of the linear light module.
22. The method of claim 21, wherein the lighting source includes
multiple light emitting diodes (LEDs), and wherein the multiple
LEDs emit light at more than one peak wavelength.
23. The method of claim 21, wherein the housing includes a channel
for holding the heat pipe, and the channel thermally couples the
housing and the heat pipe.
24. The method of claim 23, wherein the housing is extruded.
25. A method of fixing a relative position of a light guide and a
housing for the light guide, wherein the light guide and the
housing have different thermal coefficients, the method comprising:
placing a recessed registration guide on the light guide, wherein
the light guide is configured to couple light generated by a
lighting source in the housing and to emit the light in an
elongated configuration along a length of the light guide; placing
a matching registration bump on the housing, wherein the
registration bump is configured to match a shape of the recessed
registration guide, and further wherein the registration bump is
situated within the recessed registration guide; upon being heated
by the lighting source, allowing the light guide and the housing to
thermally expand at different rates in a first direction along a
length of the light guide while maintaining the registration bump
within the recessed registration guide.
26. The method of claim 25, wherein the registration bump is
hemispherical.
27. The method of claim 25, wherein the lighting source is
thermally coupled to the housing, and at least a portion of the
heat generated by the lighting source is dissipated by the
housing.
28. The method of claim 25, further comprising upon being heated by
the lighting source, allowing the light guide and the housing to
thermally expand at different rates in a second direction
substantially perpendicular to the first direction while
maintaining the registration bump within the recessed registration
guide.
29. The method of claim 28, further comprising clamping the light
guide in a third direction by the housing to limit thermal
expansion of the light guide in the third direction, wherein the
third direction is substantially perpendicular to the first
direction and the second direction.
Description
CROSS-REFERENCES TO RELATED APPLICATIONS
[0001] This application claims the benefit of the following
applications which are incorporated by reference in their
entireties, U.S. Provisional Application No. 61/737,776, entitled
"SYSTEM AND METHOD FOR MIXING AND GUIDING LIGHT EMITTED FROM LIGHT
EMITTING DIODES TO A LIGHT PIPE FOR EMISSION IN A LINEAR
CONFIGURATION," filed Dec. 15, 2012; U.S. Provisional Application
No. 61/737,777, entitled "THERMAL PATH FOR HEAT DISSIPATION IN A
LINEAR LIGHT MODULE," filed Dec. 15, 2012; U.S. Provisional
Application No. 61/737,779, entitled "MECHANICAL ATTACHMENT SYSTEM
FOR LINEAR LIGHT MODULES," filed Dec. 15, 2012; and U.S.
Provisional Application No. 61/737,780, entitled "SYSTEM AND METHOD
FOR COMMUNICATION AMONG LINEAR LIGHT MODULES IN A LIGHTING SYSTEM,"
filed Dec. 15, 2012.
BACKGROUND
[0002] Conventional systems for controlling lighting in homes and
other buildings suffer from many drawbacks. One such drawback is
that these systems rely on conventional lighting technologies, such
as incandescent bulbs and fluorescent bulbs. Such light sources are
limited in many respects. For example, such light sources typically
do not offer long life or high energy efficiency. Further, such
light sources offer only a limited selection of colors, and the
color or light output of such light sources typically changes or
degrades over time as the bulb ages. In systems that do not rely on
conventional lighting technologies, such as systems that rely on
light emitting diodes ("LEDs"), long system lives are possible and
high energy efficiency can be achieved. However, in such systems
issues with color quality can still exist.
[0003] A light source can be characterized by its color temperature
and by its color rendering index ("CRI"). The color temperature of
a light source is the temperature at which the color of light
emitted from a heated black-body radiator is matched by the color
of the light source. For a light source which does not
substantially emulate a black body radiator, such as a fluorescent
bulb or an LED, the correlated color temperature ("CCT") of the
light source is the temperature at which the color of light emitted
from a heated black-body radiator is approximated by the color of
the light source. The CRI of a light source is a measure of the
ability of a light source to reproduce the colors of various
objects faithfully in comparison with an ideal or natural light
source. The CCT and CRI of LED light sources is typically difficult
to tune and adjust. Further difficulty arises when trying to
maintain an acceptable CRI while varying the CCT of an LED light
source and while dimming the intensity level of the LED light
source from full intensity to an off condition when no light is
emitted at all.
BRIEF DESCRIPTION OF THE DRAWINGS
[0004] FIGS. 1A-1D depict an example optical coupling element for
coupling light emitted from a light emitting diode (LED) array.
[0005] FIG. 2 depicts an example light pipe coupled to an optical
coupling element.
[0006] FIGS. 3A-3F depict different views of another example light
pipe.
[0007] FIGS. 4A-4B depict different views of another example light
pipe.
[0008] FIG. 5 is a diagram of example components that drive a
linear light module.
[0009] FIG. 6 shows an end view of an example housing of a linear
light module.
[0010] FIGS. 7A-7B show views of the ends of an example linear
light module.
[0011] FIG. 8 shows an example of a linear light module.
[0012] FIG. 9 shows a diagram of an example system that includes
four linear light modules.
[0013] FIGS. 10A-10H depict different views of another example
light pipe coupled to an optical coupling element.
[0014] FIG. 11 depicts another example light pipe coupled to an
optical coupling element.
[0015] FIGS. 12A-12C depict example placements of different color
LEDs in an LED array.
[0016] FIG. 13A shows the placement of different color LEDs in an
LED array that eliminates the banding effect, and FIG. 13B shows
the relative locations of the LEDs in the array on a CIE color
diagram.
[0017] FIG. 14 is a diagram of example components of two linear
light modules coupled together.
[0018] FIG. 15 shows the relative angles of the emitted rays from
two coupled linear light modules.
[0019] FIG. 16 illustrates an example block diagram of a master
PCBA 1602 coupled with a slave PCBA 1604.
[0020] FIG. 17 is a flow diagram illustrating an example process of
creating a patterned diffuser.
[0021] FIG. 18 is a flow diagram illustrating another example
process of creating a diffuser.
[0022] FIG. 19 is a flow diagram illustrating an example process of
removing heat from a linear light module.
[0023] FIG. 20 is a flow diagram illustrating an example process of
holding a light pipe in place relative to a housing when the light
pipe and the housing have different thermal coefficients.
[0024] FIG. 21 is a flow diagram illustrating an example process of
determining relative placement locations for different color LEDs
in an LED array.
DETAILED DESCRIPTION
[0025] A linear light module that provides a uniform distribution
of tunable illumination along the length of the light module is
described. Two or more light modules can be used together to
provide a seamless longer linear source of illumination. In some
embodiments, when multiple light modules are used together in a
system, one of the light modules is designated as the primary
module which can function as a primary receiver of light tuning
commands, and the primary module re-transmits the commands to other
modules of the system.
[0026] Various aspects and examples of the invention will now be
described. The following description provides specific details for
a thorough understanding and enabling description of these
examples. One skilled in the art will understand, however, that the
invention may be practiced without many of these details.
Additionally, some well-known structures or functions may not be
shown or described in detail, so as to avoid unnecessarily
obscuring the relevant description.
[0027] The terminology used in the description presented below is
intended to be interpreted in its broadest reasonable manner, even
though it is being used in conjunction with a detailed description
of certain specific examples of the technology. Certain terms may
even be emphasized below; however, any terminology intended to be
interpreted in any restricted manner will be overtly and
specifically defined as such in this Detailed Description
section.
[0028] The correlated color temperature (CCT) of light generated by
a lamp is tunable by adjusting the amount of light contributed by
distinct sources within the lamp that generate different
wavelengths of light. For example, the amount of current supplied
to multiple light-emitting diodes (LEDs) that emit light having
different peak wavelengths can be adjusted to change the CCT of the
light generated by the lamp. Example algorithms for tuning the
light emitted by multiple LEDs to a specific CCT is described in
more detail in U.S. patent application Ser. No. 13/766,695
entitled, "System and Method for Color Tuning Light Output from an
LED-Based Lamp" and is incorporated herein in its entirety. The
light emitted by the individual LEDs should be well mixed so that
there are no visible hot spots of individual colors, particularly
if the illumination surface of the lamp is extended, as with the
linear light modules.
[0029] FIG. 8 shows an example linear light module that can be used
as a modular building block for a lighting system. In some
embodiments, the linear light module is designed to be a particular
standard length, e.g. one-foot or two-foot long lengths, similar to
conventional lighting lengths. However, the linear light module can
be designed to have any desired length. A visually appealing light
is characterized by a uniform illumination intensity along the
entire length of the lighting unit without perceptible hot spots or
color spots. To accomplish this, the light emitted from the
multiple LED sources in the lamp should be efficiently coupled and
mixed to provide the uniform illumination as it is directed to the
portion of the light module that is visible to users (the white bar
in the upper middle of the unit shown in FIG. 8). At the same time,
to make the linear light module efficient, the design of the module
should prevent light from leaking out of the light module before it
reaches the intended emission surface.
[0030] Optical Coupling Element and Linear Light Pipe
[0031] An initial optical coupling element 100 is used to
efficiently couple the light emitted by the LEDs. In some
embodiments, another type of light source can be used, such as a
fluorescent light source or halogen light source. The optical
coupling element 100 can be made from any material that transmits
the wavelengths of light generated by the LED sources, for example,
optical grade acrylic. One example of the optical coupling element
is shown in FIGS. 1A-1D. The input surface 110 of the optical
coupling element 100 has multiple concave inward cavities. In some
embodiments, as shown in FIG. 1A, the input surface 110 has a pair
of troughs 112, 114, with each trough sufficiently wide to receive
the light emitting surface of a single LED and sufficiently long to
receive the light emitting surfaces of multiple LEDs, for example,
multiple LEDs arranged in an array. A cross-section of the troughs
112, 114 are shown in FIG. 1D. The troughs are filled with a
coupling material, such as silicone gel, to couple the LEDs to the
optical coupling element 100. The configuration of concave inward
cavities is not limited to two parallel troughs, rather any number
of troughs in any convenient layout for one or more LED arrays can
be used. In some embodiments (not shown), the input surface 110 can
have a dedicated concave cavity for each individual LED in the
light source.
[0032] The optical coupling element 100 is designed to couple light
from the LEDs through the input surface 110 and emit the coupled
light through an output surface 140, where the output surface 140
is opposite the input surface 110. In some embodiments, the optical
coupling element 100 is symmetrical along the two substantially
perpendicular midlines of the input surface 110 or the output
surface 140. The input surface 110 and output surface 140 are
coupled by several side surfaces of the optical coupling element
100, namely surfaces 130, 131, 120, 121, and the surfaces on the
opposite sides of the optical coupling element 100 to these
surfaces. These side surfaces are designed to use total internal
reflection (TIR) to reflect most of the light from the LEDs within
the optical coupling element 100 until the light exits the optical
coupling element 100 from output surface 140. For example, light
that enters the optical coupling element 100 through input surface
110 can strike a first surface 130 at greater than the critical
angle, be totally internally reflected to strike a second surface
opposite the first surface at greater than the critical angle to
again be totally internally reflected, and exit the output surface
140.
[0033] Light rays that strike the surfaces of the optical coupling
element 100 at less than the critical angle will be transmitted out
of the optical coupling element 100. Thus, the curvatures of the
side surfaces of the optical coupling element 100 are designed to
ensure that most of the light from the LEDs strike the side
surfaces at greater than the critical angle. In some embodiments,
the surfaces 130, 131, 120, 121, and their opposing surfaces of the
optical coupling element 100 are paraboloids.
[0034] Further, to maximize the coupling efficiency of the optical
coupling element 100, a reflective surface, such as Miro silver,
can be positioned behind each surface 130, 131, 120, 121, and their
opposing surfaces to reflect escaping light back into the optical
coupling element 100. The reflective surface is separated from the
optical coupling element 100 by a small air gap to ensure that
conditions for total internal reflection (TIR) are met for angles
greater than the critical angle, i.e., the index of refraction of
the optical coupling element 100 is greater than the material
immediately on the outside of the optical coupling element 100. If
the reflective surface is applied directly to the surfaces of the
optical coupling element 100, the TIR mechanism would not be
effective, rather all the light striking the surface of the optical
coupling element 100 would exit the optical coupling element 100
and be directly reflected from the reflective surfaces, resulting
in a lossier reflection mechanism. The reflective surfaces in
conjunction with the TIR mechanism of the optical coupling element
100 ensure that the amount of light lost between the input surface
110 and the output surface 140 of the optical coupling element 100
is very low. However, in some embodiments, as described below, it
may be beneficial to not use the reflective surface behind one or
more surfaces of the optical coupling element to allow light to
escape from select surfaces into a light pipe.
[0035] In some embodiments, there are two criteria that the light
exiting output surface 140 of the optical coupling element 100
should meet. The first criterion specifies a range of exit angles
of the light from the output surface 140, such that light
satisfying the specified range of exit angles will continue to be
reflected via TIR within a light pipe coupled to the output surface
140. Thus, the shape of the light pipe can contribute to the
desired range of exit angles. FIG. 2 shows an optical coupling
element 210 with an exit surface 212 coupled to an example light
pipe 220. The bottom surface 227 of the light pipe 220 is
substantially normal to the output surface 212 of the optical
coupling element 210, and the top surface 221 (the emitting
surface) of the light pipe 220 is substantially parallel to the
bottom surface 227. Although the light pipe emission surface 221 is
above the height of the optical coupling element 210, the shape of
the light pipe 220 is substantially a rectangular solid. The light
pipe has an elongated shape to ensure that the light is eventually
emitted in the desired linear configuration. Further, the length of
the light pipe can be used advantageously to mix the light before
being emitted, as described below.
[0036] For the example light pipe 310 shown in FIG. 3A, the bottom
surface 314 of the light pipe 310 is tapered upward toward the
emission surface 312, and the top emission surface 312 is still
substantially perpendicular to the surface 315 where the output
surface 140 of the optical coupling element 100 would couple to the
light pipe 310.
[0037] The example light pipe 410 shown in FIG. 4A is similar in
shape to the light pipe 310, but the bottom surface 414 is stepped,
rather having a smooth taper, and the bottom surface 414 rises
toward the emission surface 412. For ease of reference, surfaces
herein may be referred to as the bottom surface and the top
surface, corresponding to the orientation of the element shown in
the figures. However, the element can have any orientation, and the
bottom surface does not have to face downward, nor does the top
surface have to face upward.
[0038] The second criterion specifies an exit aperture so that most
of the exiting light will be contained within certain dimensions of
the output surface 140. Essentially the rays of light emitted from
the extreme edge of the LED array that cross the optical coupling
element 100 will have the least steep angle. The angle at which
these rays strike the optical coupling element 100 must be greater
than the critical angle in order for these light rays to undergo
TIR. Thus, these light rays will determine the geometry of the
optical coupling element 100, and an additional margin on the angle
of these rays can also be taken into account when designing the
optical coupling element 100. The second criterion works in
conjunction with the first criterion to ensure that most of the
light exiting the optical coupling element 100 will be reflected
within the light pipe through the mechanism of TIR until the light
strikes the desired emission surface of the light pipe.
[0039] FIG. 2 illustrates one example configuration where the
optical coupling element 210 is coupled to a light pipe 220.
Similar to the optical coupling element 100, the light pipe 220 can
be made from any material that transmits the wavelengths of light
generated by the LED sources, such as optical grade acrylic. The
output surface 212 of the optical coupling element 210 is coupled
to a side surface of the light pipe 220 using an optical coupling
material, such as silicone or coupling gel.
[0040] In some embodiments, the top surface 221 of the light pipe
220 is the surface from which the light is emitted by the lighting
module, for example, as shown by the white strip of the light
module in FIG. 8. Similar to the side surfaces of the optical
coupling element 100, three side surfaces of the light pipe are
backed by a reflective surface separated from the light pipe by an
air gap: the surface 222 as seen in FIG. 2, the surface 227 that is
opposite surface 221 (on the bottom of the light pipe as depicted
in FIG. 2), and the surface opposite the surface 222. These
surfaces are separated from the reflective surface by an air gap so
that the TIR mechanism functions to keep most of the light within
the light pipe, and only the small percentage of light that strikes
the surface of the light pipe 220 at an angle less than the
critical angle leaks out of the light pipe, to be reflected back
into the light pipe by the reflective surface.
[0041] The light pipe 220 has a distal surface 225 and an opposing
end surface 226 near the optical coupling element 210. The distal
surface 225 of the light pipe 220 can be placed immediately next to
the opposing end surface 226 of a second light pipe to produce a
longer light emitting surface. FIG. 9 shows four linear light
modules 910, 920, 930, 940 placed immediately adjacent to each
other such that the light emitting surfaces of the four modules
form a continuous linear surface with no perceptible joint between
the light pipes. A system having multiple light modules will be
described below.
[0042] When a linear light module is used independently of other
linear light modules, both the distal surface 225 and the opposing
end surface 226 should be covered with reflective caps to prevent
light from propagating out the ends of the light pipe 220. Light
that is reflected from the end caps back into the light pipe 220
bounces within the light pipe until the light exits the desired
emission surface 221.
[0043] Because the light coupled from the LED sources by the
optical coupling element 100 enters the light pipe 220 from the
optical coupling element 210 from a surface 212 that is oriented in
a direction substantially perpendicular to the emission surface
221, rather than in a direction toward the emission surface 221 of
the light pipe 220, there is a strong axial component to the light
rays. The optical coupling element 100 is designed so that the rays
entering the light pipe will strike the surface of the light pipe
220 at an angle greater than the critical angle so that the light
will undergo TIR instead of exiting a surface of the light pipe
220. Because the light pipe 220 in FIG. 2 is a rectangular solid,
the light rays will spiral down the light pipe and be reflected to
spiral back in the direction of the light source. It would be
advantageous to mix the light while it is traveling down the light
pipe so that light from the individual LEDs becomes well mixed to
reduce intensity and color hot spots.
[0044] One way to mix the light in the light pipe is make the
surface opposite the emission surface of the light pipe 220 a
rippled surface. For example, small amplitude grooves or ribs can
be extruded or molded into the side surfaces of the light pipe.
Then the light rays will still undergo TIR reflection at those
surfaces of the light pipe, but the rays will no longer reflect in
a repeating prismatic pattern. Rather, the rays will be scattered
in different directions as they hit the rippled surface and develop
a stronger peripheral component and a weaker axial component. In
some embodiments, the other surfaces of the light pipe can also be
made with a rippled surface.
[0045] FIGS. 3A-3F show an example configuration of a light pipe
310 that has a tapered bottom surface 314. FIG. 3A shows a side
view of the light pipe 310, and FIG. 3F shows a perspective view of
the light pipe 310. Due to the taper of the bottom surface, the
angle that a light ray strikes each surface of the light pipe with
respect to a surface normal becomes steeper and steeper until the
conditions for TIR no longer hold, and the light exits the light
pipe. Typically, the light exits the light pipe at an angle near
the critical angle so that there is still a strong axial component
to the light. Consequently, the intensity of the emitted light does
not appear uniform in all directions. To remedy this situation, a
diffuser (described below) can be used on the emission surface, the
surface of the light pipe opposite the exiting surface, or
both.
[0046] FIGS. 4A-4B show an example configuration of a light pipe
410 that has a stepped bottom surface. The step formation of the
bottom surface helps to mix the light within the light pipe so that
the emitted light is more uniform.
[0047] FIGS. 10A-10H show different views of yet another
configuration of a light pipe 1010 that has a primarily concave
upwards shape along most of the bottom surface 1020 (opposite the
emission surface 1030) with a flat portion near the end of the
light pipe 1010 with the optical coupling element 1050.
Additionally, the bottom surface 1020 has saw-tooth like features.
In some embodiments, the amplitude of the features can vary along
the length of the bottom surface 1020. For example, as shown in
FIG. 10A the amplitude of the features is largest near point J
along the length of the bottom surface 1020 and is constant until
point K. Then from point K to point L, the amplitude monotonically
decreases. In some embodiments, the amplitude of the features can
increase or decrease along the length of the bottom surface and can
even be random. In some embodiments, the amplitude of the saw-tooth
features can be selected to be easily machinable, for example, on
the order of a millimeter or greater.
[0048] The function of the saw-tooth features is to extract light
from the light pipe 1010 to further mix the light from the optical
coupling element 1050. As described above, the surfaces of the
light pipe 1010, except for the emission surface 1030 are backed by
a reflective surface separated from the light pipe 1010 by an air
gap. Light extracted from the light pipe by the saw-tooth features
is reflected back into the light pipe 1010 through the saw-tooth
features into the light pipe 1010 again, causing the light to be
mixed.
[0049] In some embodiments, finer features on the order of tens of
microns to hundreds of microns in amplitude can be used. These
finer features can be saw-tooth or convex or concave features, such
as dots or bars. The finer features can be periodic, aperiodic,
clusters, and/or varying in density. Further, the finer features
can be machined or molded as part of the light pipe. Because the
function of the features is to extract light from the light pipe,
with finer features, there is more control over the uniformity of
the light that is emitted by the light pipe.
[0050] Further, there is a portion of the light pipe that is above
the optical coupling element 1050 and cantilevered out beyond the
optical coupling element 1050 on the left, referred to as a bridge
1040. In this embodiment, the side surfaces of the optical coupling
element 1050 are backed by a reflective surface separated from the
optical coupling element 150 by an air gap, except for portions of
or all of the top surface. Instead, at the top surface, the optical
coupling element 1050 physically contacts the bridge 1040, thus
removing the condition for TIR inside the optical coupling element
1050 and causing some of the light in the optical coupling element
1050 to leak into the bridge 1040. At least at the portions where
the optical coupling element 1050 and the bridge make contact,
there is no reflective surface used. The bridge 1040 is used to
ensure that the light emitted from emission surface 1020 is
uniform, primarily in the region above the optical coupling element
1050. In some embodiments, the bridge 1040 is separate from the
rest of the light pipe 1010, and is physically attached to the top
of the optical coupling element 1050.
[0051] To send even more light to the bridge 1040, there is a slot
1060 angled away from the bridge 1040 next to a middle section 1070
within the light pipe 1010. Light exiting the top surface the
optical coupling element 1050, where there is no reflective surface
backing, will enter the slot and be reflected to the left toward
the bridge 1040. The angled sides of the middle section 1070
further reflect the light toward the emission surface 1030.
[0052] FIG. 11 shows yet another configuration of a light pipe 1110
that has a concave upward shape with saw-tooth like features along
most of the bottom surface 1120 opposite the emission surface 1130,
similar to the light pipe 1010 shown in FIG. 10A. However, the
bridge 1140 and light pipe 1110 in the example configuration shown
in FIG. 11 are molded as a single piece with an air gap between the
optical coupling element 1150 and the bridge 1140. The width of the
air gap can be variable or constant. In some embodiments, the width
of the air gap can be between approximately 2 mm and 6 mm. The
length of the air gap starts from above the LED array 1155 and
extends to the diffuser in some embodiments, and beyond the
diffuser in other embodiments.
[0053] Light is extracted from the optical coupling element 1150
through a light extraction element 1190 coupled to the top surface
of the optical coupling element 1150 that is facing toward the
bridge 1140. Non-limiting examples of the light extraction element
1190 can include a brightness enhancement film, diffusion film, or
other type of diffuser. The length and width of the light
extraction element 1190 can be designed to extract a desired amount
of light from the optical coupling element 1150 for coupling to the
bridge 1140.
[0054] As shown in FIG. 15, the light emitted from emission surface
1130 by the light pipe 1110 is angled from the vertical in a plane
defined by the longitudinal axis of the light pipe and the height
of the light pipe (i.e., the plane of the paper as shown in FIG.
15). The light is angled from vertical because this is the
condition for which the condition for TIR is no longer met. In some
embodiments, the angle of is approximately 30 degrees. As shown in
the example light configuration of FIG. 15, two light pipes can be
placed end to end, where the light pipes face in opposite
directions. Rays emitted from vertical in a first direction from
the first light pipe, and rays emitted from vertical in a second
direction, opposite from the first, from the second light pipe can
be designed to strike a reflector or a diffuser to make the light
appear uniform in the far field to an observer. As a result, the
observer will no longer be able to identify that the light coming
from each of the light pipes was originally emitted in different
directions.
[0055] Diffusers
[0056] In some cases, the embodiments of the light pipe depicted in
FIGS. 2-4 as well as other embodiments of a linear light guiding
pipe can provide a more uniformly mixed illumination output through
the use of a diffuser on the exit surface, for example, exit
surface 221 of the light pipe 220 in FIG. 2. The diffuser functions
by breaking up the light reaching the emission surface at an angle
smaller than the critical angle and re-directing portions of that
light into different directions. A portion of the light will leave
the exit surface after being diffused by the diffuser, while
another portion of the light will re-enter the light pipe to be
reflected within the light pipe until it reaches the exit surface
again and is re-diffused by the diffuser on the exit surface.
[0057] The diffuser can be just as effective in mixing the light
when placed on the bottom surface of the light pipe opposite the
exit surface. However, rather having a portion of the light that
strikes the bottom surface at smaller than the critical angle being
diffused by the diffuser and permanently exiting the light pipe,
the light is reflected back into the light pipe by the reflective
surface outside the light pipe. This reflected light is diffused
again by the diffuser when re-entering the light pipe. The light
will be reflected within the light pipe, either by TIR or by being
directly reflected by a reflective surface outside of the light
pipe, eventually being emitted from the exit surface of the light
pipe.
[0058] The use of the diffuser on either the exiting surface or the
opposite surface of the light pipe helps to mix the light from the
different LED sources inside the light pipe to produce a more
uniform illumination at the exit surface of the light pipe. Without
the use of a diffuser, there can be gradients in the intensity of
the light within the light pipe. For example, the intensity of the
light seen from one end of the light pipe, for example, looking
into end face 225 of the light pipe 220 in FIG. 2 can be stronger
than the intensity of the light seen looking into the opposite end
face 226 of the light pipe 220.
[0059] Various materials can be used on the emission surface and/or
the opposite surface of the light pipe to homogenize the light in
the light pipe, for example, a diffusive material such as a
laminated diffusion film, a molded textured surface, a diffusive
reflector, and/or a spectral reflector. In some embodiments,
various combinations of shapes and materials can be used on the
emission surface and/or the opposite surface. For example, the
diffusive material need not cover the entire emission surface or
the entire opposite surface. The diffusive material can be used in
one or more discrete sections along the light pipe in different
patterns, either uniform or non-uniform.
[0060] Alternatively or additionally, more than one type of
material can be used in different patterns along the emission
surface and/or the opposite surface of the light pipe. For example,
a diffusive material can be alternated with a spectral reflector
along the length of the light pipe.
[0061] In some embodiments, a brightness enhancement film, made by,
for example, 3M of Maplewood, Minn. can be used. The brightness
enhancement film is directional with grooves in the film aligned in
a particular direction. In some embodiments, the brightness
enhancement film can be positioned with the grooves at one or more
angles, for example, a uniform or non-uniform patchwork of groove
angles can be used along the emission surface and/or the opposite
surface. The brightness enhancement film can be used either alone
or with another type of diffusive material in a uniform or
non-uniform pattern.
[0062] A separate steering element can be placed over the emission
surface of the light pipe with an air gap between the steering
element and the emission surface to further reduce the axial
component of the emitted light. In some embodiments, the steering
element has a saw tooth pattern on the surface closest to the light
pipe to diffract the light in different directions.
[0063] The configurations of the light pipe depicted in FIGS.
10A-10H and FIG. 11 as well as other embodiments of the linear
light pipe can provide a more uniformly mixed illumination output
through the use of a diffuser 1080, 1180 between the optical
coupling element and the light pipe. Further, a diffuser can be
used as the light extraction element 1190 shown in FIG. 11.
[0064] A Patterned Light Diffuser
[0065] A diffuser can be the final mixing element for eliminating
any remaining hot-spots by diffusing light exiting an optical
element, such as a light pipe, or an optical coupling element that
couples light from LEDs, into a large range of angles to homogenize
both the color and intensity variations at the diffuser exit, thus
providing more uniform illumination.
[0066] Better mixing is typically achieved by increasing the
diffusion angle of the diffuser to cause the light impinging on the
diffuser to spread over a wider range. As a result, light from the
various hot spots on the diffuser interfere with each other and
decreases the color and intensity gradients perceptible in the
output beam.
[0067] However, higher diffusion usually results in higher losses
so there is a tradeoff between higher diffusion and lower light
output. Described below are two manufacturing processes by which
better light mixing can be achieved with lower losses than with
conventional manufacturing processes. The first process replaces
plastic diffusers with coated glass so that much higher optical
flux densities can be diffused without degradation of the plastic
with time and temperature.
[0068] A patterned diffuser with plain uncoated glass between
patterned sections can effectively cause a large amount of light
mixing while still allowing a significant amount of the light to
pass with low loss through the glass.
[0069] FIG. 17 is a flow diagram illustrating an example process of
creating a patterned diffuser. At block 1705, scattering particles,
such as Kaolin clay, are milled and screened for particles having a
size approximately less than or equal to two microns, or any other
suitable size.
[0070] Then at block 1710, the scattering particles are mixed in a
suspension solution. In some embodiments, the suspension solution
can be a silicone adhesive, such as made by DuPont of Wilmington,
Del.
[0071] Next, at block 1715, controlled amounts of the mixture are
patterned onto a substrate, such as a glass substrate. In some
embodiments, the mixture can be squeezed through a pattern of
micro-holes to deposit drops onto the glass substrate. The pattern
of holes can include holes with a pre-determined diameter and a
predetermined pitch. In some embodiments, the mixture can be made
thinner to have a lower viscosity, and the resulting mixture can be
deposited onto the glass substrate by spin-coating or spraying.
This results in a smooth layer, but the resulting diffuser will not
have a pattern.
[0072] At block 1720, the glass substrate with the deposited
mixture is heated, for example, in an oven, until the adhesive has
cured. The result is a light diffuser that can withstand high
optical flux densities.
[0073] FIG. other is a flow diagram illustrating an example process
of creating a diffuser. As described above, at block 1805,
scattering particles, such as Kaolin clay, are milled and screened
to produce Kaolin powder. The proper ratio of silicone and
scattering particles can be experimentally determined for the
desired diffusive effect.
[0074] Then at block 1810, the injection moldable silicone is
compounded with the scattering particles to produce a resin premix.
At block 1815, the resin premix can be injection molded to produce
diffusers in various desired shapes.
[0075] LED Array
[0076] The LED array used with the optical coupling element can
have any number of LEDs, for example, a 2.times.5 LED array can be
used. The wavelengths of light emitted by the LEDs in the array are
selected so that the combined light from all the LEDs generate a
desired CCT. The array may include LEDs having different colors and
one or more white LEDs. Because the mixing of the light from the
multiple LEDs achieved from bouncing the light against the surfaces
of the optical coupling element and light pipe and the outer
reflective surfaces before being emitted from the emission surface
of the light pipe is not perfect, it would be beneficial to select
the placement of the individual colored LEDs in the array to
`pre-mix` the light to produce a more uniform light distribution at
the emitting surface of the light pipe without discernible bands of
colors.
[0077] In embodiments of the linear light module described above
having an optical coupling element emitting directly into an
adjacent light pipe, a horizontal banding effect may be visible
along the emission surface of the light pipe. The banding effect
arises due to insufficient mixing of the light emitted from
adjacent LEDs.
[0078] FIGS. 12A-12C show three different placements of LEDs in an
LED array. The symbol W corresponds to a white color LED; R
corresponds to a red color LED; A corresponds to an amber color
LED; G corresponds to a green color LED; and B corresponds to a
blue color LED. FIG. 12A shows a 2.times.5 LED array where the top
three rows of LEDs do not additively combine to produce light that
is nearly white. As a result, if there is insufficient mixing of
the light from the array by the optical coupling element and the
light pipe, bands of colored light corresponding to the additive
color of each of the rows of LEDs in the array may be seen
periodically along the emission surface. Thus, the top row of the
LED array causes periodic red bands of light along the emission
surface of the light pipe, the second row causes periodic amber
bands of light, and the third row causes periodic bands of
greenish-blue light.
[0079] One way to eliminate color bands along the emission surface
is to select pairs of LED colors that are nearly opposite each
other in chromaticity space across the Planckian locus to be placed
adjacent to each other. FIG. 13 shows a CIE 1931 chromaticity space
diagram with a Planckian locus, the path that the color of a black
body takes as the blackbody temperature changes. Each LED color in
the LED array is represented by a dot on the diagram and is labeled
with the first letter of the color emitted by that LED (R for red,
A for amber, G for green, B for blue, and W for white). Lines
between the dots connect pairs of LED colors that when mixed,
produce nearly a white color. For example, the red color LED (R) is
paired with the amber color LED (A); the amber color LED is paired
with the blue color LED; and the red color LED is paired with the
green color LED. FIGS. 12B and 13A show a 2.times.5 LED array with
these LED color pairings. The light emitted by a linear light
module that uses this placement configuration for the LEDs in the
LED array does not exhibit discernible color bands across the
emission surface.
[0080] FIG. 12C shows a 3.times.3 LED array where each row of three
LEDs produce nearly a white color. There is a white LED in the
center of each row, and the white light is combined with a red
color LED and an amber color LED in the first row, with a green
color LED and a red color LED in the second row, and with an amber
color LED and a blue color LED in the bottom row.
[0081] Because it is beneficial to pre-mix the light as much as
possible as early as possible before being emitted from the
emission surface of the light pipe, a diffuser 1180 can be added to
the output surface of the optical coupling element, as shown in the
example light pipe configuration of FIG. 11. The diffuser 1180
diffuses the light exiting the optical coupling element 1150 prior
to being mixed as it reflects from the surfaces of the light pipe
1110 and the outer reflective surfaces.
[0082] FIG. 21 is a flow diagram illustrating an example process of
determining relative placement locations for different color LEDs
in an LED array. At block 2105, a number of LEDs and a plurality of
emission wavelengths of the LEDs are initially selected to produce
a desired CCT and output power. Then at block 2110, each of the
corresponding colors for the selected LED emission wavelengths are
plotted on a color diagram. At block 2115, for each row of LEDs in
an LED array, the LEDs are selected by emission color so that the
additive color emitted light of the LEDs in a row generates nearly
white light.
[0083] Providing a Thermal Path for Heat Generated by the LEDs
[0084] FIG. 5 shows example elements in the linear light module 800
that generate the illumination provided by the module. In the
example of FIG. 5, the light source is a 2.times.5 LED array.
However, any number of LEDs in any configuration can be used as the
light source. The LED array is coupled to the optical coupling
element 100 as described above.
[0085] The electronics for driving the LED array are included in a
printed circuit board assembly (PCBA) that is coupled to the LED
array through a flex circuit. A flex circuit is used to couple the
PCBA to the LED array because the flex circuit allows for thermal
expansion of elements due to heating by the LEDs without impacting
the alignment of the LEDs with the optical coupling element
100.
[0086] Coupled directly to the flex circuit is a heat transfer
block made from a thermally conductive material, such as copper.
The heat transfer block conducts the heat generated by the LED
array to a heat pipe that is positioned along the inside of a
housing of the light module. In some embodiments, the housing is
made from a thermally conductive material, such as aluminum. Thus,
there is a thermal path for the heat generated by the LEDs to the
aluminum housing. The mounting for the heat pipe is shown in FIG.
6. The heat pipe is also made from a thermally conductive material
that transfers heat to the housing. The housing acts as a heat sink
and is in contact with the environment to dissipate heat generated
by the LEDs from the light module.
[0087] FIG. 19 is a flow diagram illustrating an example process of
removing heat from a linear light module. At block 1905, heat is
conducted away from the lighting source via a heat transfer block.
Then at block 1910, heat is conducted away from the heat transfer
block via a heat pipe. And at block 1915, heat is conducted away
from the heat pipe via a housing of the linear light module and the
lighting source.
[0088] FIG. 5 also shows registration markers that are used to pin
the light pipe and the housing together at a single point, and yet
allow them to move relative to each other due to different thermal
coefficients that result in different rates of thermal expansion.
The housing has a hemispherical bump, and the light pipe has a
matching hemispherical recess. FIG. 7A shows the back side of the
view shown in FIG. 5 with a better view of the hemispherical recess
722 in the light pipe 720. For reference, light from the 2.times.5
LED array 752 is coupled to the flex circuit 750, and the light
from the LEDs is coupled by the optical coupling element 710 to the
light pipe 720. The heat pipe mounting 730 is also shown in the
housing 740. In some embodiments, the shape of the matching bump
and recess can be different from hemispherical. The dimensions of
the recess in the light pipe is small so that the light within the
light pipe is effected a minimal amount, yet large enough to
prevent the light pipe from moving.
[0089] FIG. 7B shows the distal end of the light pipe 720 and
housing 740. Because the light pipe is only pinned to the housing
at a single location, the light pipe can expand longitudinally
along the length of the lighting module (in the z-direction)
relative to the housing. Although the light pipe cannot move in the
x-direction because it is clamped between the two sides 741, 742 of
the housing 740, the light pipe 720 can also expand in the
y-direction between the sides 741, 742 of the housing.
[0090] By allowing the light pipe the freedom to move relative to
the housing, stress due to thermal expansion is relieved to prevent
breakage of the LEDs.
[0091] FIG. 20 is a flow diagram illustrating an example process of
holding a light pipe in place relative to a housing when the light
pipe and the housing have different thermal coefficients. At block
2005, a recessed registration guide is placed on a light pipe. Then
at block 2010, a matching registration bump is placed on a housing
for the light pipe and a lighting source.
[0092] Next, at block 2015, the light pipe and the housing are
allowed to thermally expand at different rates in a first direction
along a length of the light pipe while maintaining the registration
bump within the recessed registration guide. At block 2020, the
light pipe and the housing are allowed to thermally expand at
different rates in a second direction substantially perpendicular
to the first direction while maintaining the registration bump
within the recessed registration guide. Finally, at block 2025, the
light pipe is clamped in a third direction by the housing which
limits thermal expansion of the light pipe in the third direction,
wherein the third direction is substantially perpendicular to the
first direction and the second direction.
[0093] Mechanically Coupling together Multiple Linear Light
Modules
[0094] The linear light module 800 shown in FIG. 8 uses a light
pipe that has end faces that are flat and perpendicular to the axis
of the light pipe, such as in the example light pipes of FIGS. 2-4.
When the linear light module 800 is used as a stand-alone unit, the
end faces of the light pipe, for example, surfaces 225, 226 in FIG.
2 are covered with a reflective surface to reflect light exiting
these surfaces back into the light pipe to bounce around until
eventually being emitted through the emission surface 221.
[0095] In some embodiments, more than one linear light module 800
can be coupled together to form a longer continuous emission
surface. FIG. 9 shows an example system where four linear light
modules 910, 920, 930, 940 are coupled together as a system 900. In
this case, the light pipe of each of the linear light modules 910,
920, 930, 940 touch, or nearly touch, each adjacent light pipe to
form a single continuous linear emission surface. The example
system of FIG. 9 shows three types of modules, a primary module 910
on the right of the system, two secondary modules 920, 930 in the
middle of the system, and an end unit 940 on the left end of the
system.
[0096] The primary module 910 has a reflective end cap on the end
of its light pipe nearest to the LED sources, corresponding to, for
example, surface 226 of light pipe 220 in FIG. 2. The opposite end
of the light pipe, corresponding to, for example, surface 225 in
FIG. 2, is not covered by a reflective material. Thus, light
escaping from this surface of the light pipe of module 910 enters
the adjacent light pipe of the next light module 920.
[0097] For the secondary modules 920, 930, neither end of the light
pipe is covered so that light can be transmitted between the light
pipes of the four modules 910, 920, 930, 940.
[0098] For the end module 940, the end of the light pipe farthest
from the LED sources, corresponding to, for example, surface 225 of
light pipe 220 in FIG. 2 is covered with a reflective end cap to
prevent light from escaping from this surface. The opposite end of
the light pipe closest to module 930 is not covered with reflective
material to permit light from the light pipe of module 940 to enter
the light pipe of the module 930, and to permit light from the
light pipe of module 930 to enter the light pipe of module 940.
[0099] A person of skill in the art will appreciate that the length
of the light pipes can be designed to be a single length (e.g. one
foot or two foot long light pipes), different standard lengths
(e.g., one foot, two feet, three feet, etc.), or customized
lengths. Thus, the linear light modules can be used as modular
building blocks for designing a lighting system having various
lengths FIG. 9 shows four two-foot modules coupled together to form
a continuous eight foot long light emission surface. Each two-foot
module can have a single two-foot long light pipe having a single
LED array, for example a 2.times.5 array. Alternatively, each
two-foot module can be made up of two one-foot long light pipes
where each light pipe couples light from a separate LED array, for
example, two 2.times.5 arrays of LEDs can drive the two-foot module
together.
[0100] Two linear light modules that each use light pipes that do
not have flat end faces, such as the light pipes shown in the
examples of FIGS. 10 and 11 can be paired together to form a single
composite light emission surface, as shown in the example
configuration of FIG. 15. The light pipes are placed end to end
where the farthest end of the light pipe from the optical coupling
element of a first light pipe is placed closest to the counterpart
end of the second light pipe farthest from the optical coupling
element. In some embodiments, each light pipe building block is
approximately one foot long, providing a two-foot long light when
two light pipes are coupled together. Each light pipe has its own
LED array source. Thus, with two light pipes, twice the light is
emitted as compared to a single light pipe. The length of the
composite light emission surface can be extended by adding on
additional modules, either as a single unit or in pairs as
described above.
[0101] In one embodiment, the linear light modules are designed to
attach from a fixture, a wall, or the ceiling. To permit the light
pipe of the adjacent linear light modules to touch, or nearly
touch, a mechanical system is used that clips the adjacent linear
light modules together. In one embodiment, the linear light modules
should be able to slide directly into place from below (in a
direction perpendicular to the emission surface) without needing to
slide into place horizontally because there is no room to slide the
modules horizontally.
[0102] The linear light modules can be clipped together using the
dovetail grooves in the extruded housing of the modules shown in
FIG. 6. In one embodiment, a clip or other fastener can be used
with these grooves to mechanically couple together two adjacent
linear light modules.
[0103] In one embodiment, the grooves can be used with a rail
system so that the linear light modules can be attached together
using a rail, and a user can use the rail to attach the linear
light modules together or to a particular surface, such as a wall
or ceiling.
[0104] In one embodiment, the side grooves shown in FIG. 6 can be
used to clip together adjacent light modules. Alternatively or
additionally, optics such as reflectors can be clipped onto the
light module using the side grooves. Similarly, the reflector/lens
mounting near the emission surface of the light pipe can also be
used for attaching optics onto the module.
[0105] Communications and Power Transmission among Coupled Light
Modules
[0106] Each lighting module has a PCBA that includes the
electronics for driving the LED array, and the PCBA has two
connectors. One connector (the near connector) is near the LED
array. The other connector (the far connector) is on the far side
of the light module. These connectors can be used to optionally
couple to adjacent light modules so that power and communication
signals can be sent between light modules.
[0107] The system 900 shown in FIG. 9 has four coupled light
modules 910, 920, 930, 940, and the modules are mechanically
coupled as described above. Additionally, each of the modules has a
PCBA 911, 921, 931, 941 with two connectors that can be used to
electrically couple adjacent modules so that power and/or
communication signals can be passed between modules. The near
connector of PCBA 911 is not used because module 910 is the unit on
the farthest right of the system 900. The far connector of PCBA 911
is coupled through an electric cable, e.g. a flat cable, to the
near connector of PCBA 921. Similarly, the far connector of PCBA
921 is coupled through an electric cable to the near connector of
PCBA 931, and the far connector of PCBA 931 is coupled through an
electric cable to the near connector of PCBA 941. The far connector
of PCBA 941 is not used because module 940 is the unit on the
farthest left of the system 900.
[0108] The cables plug into the near connector of the PCBA through
a window, and the windows can be covered with a plate. This setup
allows each light module 910, 920, 930, 940 to slide into place,
for example, as ceiling units. Because the emission surface of each
light pipe seamlessly contacts the neighboring light pipe, there is
no room to electrically couple the units using integrating sockets
or any other method that would require a sideways movement of the
module.
[0109] The electric cables can include a first cable that is used
to transmit communication signals between the light modules 910,
920, 930, 940. In one embodiment, one of the light modules is a
master unit, for example, primary module 910. Only primary module
910 receives commands from an external source, for example, either
wirelessly through a radio receiver or through wired means. The
commands can include, but are not limited to, tuning the color
temperature of the light emitted by all of the modules, adjusting
the intensity of the illumination, calibrating the light modules,
and turning the modules on or off. Primary module 910 then
re-transmits the commands to the rest of the modules 920, 930, 940
in the system 900 through the electric cables. Because the other
modules 920, 930, 940 do not have a radio receiver or a wired
signal receiver, the cost of the system is reduced.
[0110] In one embodiment, each of the modules 910, 920, 930, 940 of
the system 900 has a wired or wireless receiver to receive commands
from an external source. Then the primary module 910 or any other
module 920, 930, 940 can re-broadcast the commands to the other
modules through the electric cables. In this case, the
communications through the flat cables act as a redundant
communication system. If a module has already received the command
from the external source, it can ignore the re-broadcast
command.
[0111] The electric cables can also include a second cable that is
used to transmit power between the light modules 910, 920, 930,
940. In one embodiment, the primary module 910 can include a power
supply large enough to provide power to the other three modules
920, 930, 940. Depending on the strength of the power supply, a
single module can provide power through the electric cables to even
more modules. Alternatively, multiple power supplies can be used
within the system, depending upon how many modules need power.
[0112] FIG. 14 includes a master printed circuit board assembly
(PCBA) 1452 and a slave PCBA 1454 on opposite ends of a composite
linear light module 1400 that includes two individual linear light
modules coupled together. In one example, the master PCBA 1452 is
electrically coupled to the slave PCBA 1454. Both the PCBA 1452 and
the PCBA 1454 are printed circuit boards or other forms of embedded
circuitry. The master PCBA 1452 includes a master controller
module, such as a microprocessor, a radio communication device, and
a memory module.
[0113] The master PCBA 1452 includes a first optical sensor 1456 to
provide optical feedback during calibration. The slave PCBA 1454
also includes a second optical sensor 1458 for feedback to the
master PCBA 1452. The first optical sensor 1456 and the second
optical sensor 1458 can be broad spectrum optical sensors, such as
PIN diodes. The PIN diodes are diodes with wide, lightly doped near
intrinsic semiconductor region between of a p-type semiconductor
and an n-type semiconductor region. One example of a suitable PIN
diode that can be used is the PD15-22C/TR8 PIN diode manufactured
by Everlight Electronics Co., Ltd. Of New Taipei City, Taiwan. Both
the master PCBA 1452 and the slave PCBA 1454 can include one or
more thermal sensors near the LED array, such as the thermistor
1350 of FIG. 13A. The thermistor changes resistance based on
temperature of its environment.
[0114] The PIN diodes 1456, 1458 are oriented on the back side of
the printed circuit board assemblies seen in FIG. 14, facing toward
a side surface of the light pipe. As described above, the side
surfaces of each light pipe are backed by a reflective surface.
Consequently, a hole is formed in the reflective surface near each
PIN diode to allow a small portion of light to escape to be sensed
by the PIN diode.
[0115] The master PCBA 1452 includes circuitry to perform self
calibration on the fly. The slave PCBA 1454 can also perform self
calibration on-the-fly. Self calibration can be performed via
optical feedback through the optical sensor 1456. The LEDs degrade
over time. Some color LED degrades more so than others. For
example, the red LEDs degrade most with life and the blue LEDs are
most resistant to degradation. Hence, during the self calibration
the red color over blue color ratio is measured and compare with
factory values. Then the blue LED current is lower to reset the
present color ratio to that of the factory setting as the red color
LEDs degrade.
[0116] FIG. 16 illustrates an example block diagram of a master
PCBA 1602 coupled with a slave PCBA 1604. The master PCBA 1602 can
be the master PCBA 1452 of FIG. 14. The slave PCBA 1604 can be the
slave PCBA 1454 of FIG. 14. The master PCBA 1602 includes a power
connection 1606 and a LED driver 1608. The power connection 1606
provides electrical power to the LED driver 1608 to drive a first
plurality of LEDs 1609. The LED driver 1608 can be configured by a
master controller module 1610. The master controller module 1610 is
electrical circuitry for configuring the LED driver 1608. The
master controller module 1610 can be a microprocessor or other
controller type embedded within the master PCBA 1602. Commands can
be sent to the master controller module 1610 from an external user
interface 1601, such as dimming the intensity of the light with the
same CCT or changing the CCT of the light. Further, the mater
controller module 1610 can perform algorithms for tuning the CCT of
the LEDs such as described in U.S. patent application Ser. No.
13/766,695 entitled, "System and Method for Color Tuning Light
Output from an LED-Based Lamp."
[0117] Communications between the external user interface 1601 and
the master controller module 1610 can be via RS-232 or RS-485
standards, for example. Similarly, communications between the
master controller module 1610 and the slave controller 1628 can
also be via RS-232 or RS-485 standards, for example.
[0118] The master controller module 1610 can receive inputs from an
optical sensor module 1612. The optical sensor module 1612 can be a
pin diode, such as the pin diodes illustrated in FIG. 14, coupled
to electronic circuitry to transmit a sensed color spectrum to the
master controller module 1610. The master controller module 1610
can also receive inputs from a thermal sensor module 1614. The
thermal sensor module 1614 can receive temperature information from
a thermistor, such as the thermistor 1350 of FIG. 13A, on the
master PCBA 1602 or adjacent to the first plurality of LEDs 1609.
The sensory information received can be stored on a memory module
1616 of the master PCBA 1602. The sensory information can be stored
as a sensor history database 1618. When configuring the LED driver
1608, the master controller module 1610 can refer to a color model
1620 stored on the memory module 1616. The color model 1620
provides a driving signal to produce a particular color spectrum
based on an operating temperature and a driving current level. The
thermal sensor 1614 can provide the operating temperature.
[0119] The first plurality of LEDs 1609 may degrade over time. Some
color sets degrade more so than others. For example, a red color
set within the first plurality of LEDs 1609 may degrade faster than
a blue color set. The master controller module 1610 is configured
to calibrate the first plurality of LEDs 1609. In one example, the
master controller module 1610 can calibrate the first plurality of
LEDs 1609 to return to its factory settings. A factory setting
database 1622 can be stored on the memory 1616. The factory setting
database 1622 may store ratios of colors, such as a red color
intensity over a blue color intensity or an amber color intensity
over a blue color intensity. The optical sensor module 1614 can
provide color spectrum information to the master controller module
1610 in order to return the present color ratios to the factory
setting as according to the factory setting database 1622.
[0120] In some embodiments, to determine the present color ratios,
the master controller module 1610 can flash each color set of the
first plurality of LEDs 1609 and measure the intensity of the color
sensed by the optical sensor module 1614. The measured color
intensities of different colors can be normalized against a chosen
color set, such as blue LEDs, to arrive at the present color ratios
of the first plurality of LEDs 1609. The master controller module
1610 can lower a driving current for a blue color set of LEDs
amongst the first plurality of LEDs 1609 until the present color
ratio with respect to the blue color is the same as the factory
setting ratio in the factory setting database 1622.
[0121] The master PCBA 1602 can also include a radio module 1624 to
communicate with an external control device, such as a remote
control. The radio module 1624 may be a radio transceiver or a set
of a radio transmitter and radio receiver. The radio module 1624
can receive commands, such as calibration commands or commands to
match a particular color spectrum or a particular correlated color
temperature (CCT). The radio module 1624 can also transmit the
current sensor information, the color model 1620, the sensor
history 1618, the factory setting database 1622, or any combination
thereof.
[0122] The master PCBA 1602 further includes a slave interface 1626
for communicating with the slave PCBA 1604. The slave PCBA 1604
includes a master interface 1628 for communicating with the master
PCBA 1602. The master interface 1628 receives configuration
messages from the slave interface 1626 of the master PCBA 1602. The
configuration messages dictate how a LED driver 1630 of the slave
PCBA 1604 drives the second plurality of LEDs 1631. The LED driver
1630 derives its power from a power connection 1632. The
configuration received via the configuration messages can be stored
in a memory module 1634 of the slave PCBA 1604.
[0123] The slave PCBA 1604 can also include a slave thermal sensor
module 1636 and a slave optical sensor module 1638 for providing
thermal and optical feedback through the master interface 1628,
such that the master controller module 1610 can determine the
driving signal configuration for the LED driver 1630 of the slave
PCBA 1604. The master controller module 1610 can determine the
driving signal configuration for the LED driver 1630 the same way
it determines the driving signal configuration for the LED driver
1609, such as through calibration.
CONCLUSION
[0124] Unless the context clearly requires otherwise, throughout
the description and the claims, the words "comprise," "comprising,"
and the like are to be construed in an inclusive sense (i.e., to
say, in the sense of "including, but not limited to"), as opposed
to an exclusive or exhaustive sense. As used herein, the terms
"connected," "coupled," or any variant thereof means any connection
or coupling, either direct or indirect, between two or more
elements. Such a coupling or connection between the elements can be
physical, logical, or a combination thereof. Additionally, the
words "herein," "above," "below," and words of similar import, when
used in this application, refer to this application as a whole and
not to any particular portions of this application. Where the
context permits, words in the above Detailed Description using the
singular or plural number may also include the plural or singular
number respectively. The word "or," in reference to a list of two
or more items, covers all of the following interpretations of the
word: any of the items in the list, all of the items in the list,
and any combination of the items in the list.
[0125] The above Detailed Description of examples of the invention
is not intended to be exhaustive or to limit the invention to the
precise form disclosed above. While specific examples for the
invention are described above for illustrative purposes, various
equivalent modifications are possible within the scope of the
invention, as those skilled in the relevant art will recognize.
While processes or blocks are presented in a given order in this
application, alternative implementations may perform routines
having steps performed in a different order, or employ systems
having blocks in a different order. Some processes or blocks may be
deleted, moved, added, subdivided, combined, and/or modified to
provide alternative or subcombinations. Also, while processes or
blocks are at times shown as being performed in series, these
processes or blocks may instead be performed or implemented in
parallel, or may be performed at different times. Further any
specific numbers noted herein are only examples. It is understood
that alternative implementations may employ differing values or
ranges.
[0126] The various illustrations and teachings provided herein can
also be applied to systems other than the system described above.
The elements and acts of the various examples described above can
be combined to provide further implementations of the
invention.
[0127] Any patents and applications and other references noted
above, including any that may be listed in accompanying filing
papers, are incorporated herein by reference. Aspects of the
invention can be modified, if necessary, to employ the systems,
functions, and concepts included in such references to provide
further implementations of the invention.
[0128] These and other changes can be made to the invention in
light of the above Detailed Description. While the above
description describes certain examples of the invention, and
describes the best mode contemplated, no matter how detailed the
above appears in text, the invention can be practiced in many ways.
Details of the system may vary considerably in its specific
implementation, while still being encompassed by the invention
disclosed herein. As noted above, particular terminology used when
describing certain features or aspects of the invention should not
be taken to imply that the terminology is being redefined herein to
be restricted to any specific characteristics, features, or aspects
of the invention with which that terminology is associated. In
general, the terms used in the following claims should not be
construed to limit the invention to the specific examples disclosed
in the specification, unless the above Detailed Description section
explicitly defines such terms. Accordingly, the actual scope of the
invention encompasses not only the disclosed examples, but also all
equivalent ways of practicing or implementing the invention under
the claims.
[0129] While certain aspects of the invention are presented below
in certain claim forms, the applicant contemplates the various
aspects of the invention in any number of claim forms. For example,
while only one aspect of the invention is recited as a
means-plus-function claim under 35 U.S.C. .sctn.112, sixth
paragraph, other aspects may likewise be embodied as a
means-plus-function claim, or in other forms, such as being
embodied in a computer-readable medium. (Any claims intended to be
treated under 35 U.S.C. .sctn.112, 6 will begin with the words
"means for.") Accordingly, the applicant reserves the right to add
additional claims after filing the application to pursue such
additional claim forms for other aspects of the invention.
* * * * *