U.S. patent application number 14/149042 was filed with the patent office on 2014-05-08 for constrained folded path resonant white light scintillator.
This patent application is currently assigned to LumenFlow Corp.. The applicant listed for this patent is LumenFlow Corp.. Invention is credited to Paul L. Bourget, Harold W. Brunt, JR..
Application Number | 20140126224 14/149042 |
Document ID | / |
Family ID | 43859835 |
Filed Date | 2014-05-08 |
United States Patent
Application |
20140126224 |
Kind Code |
A1 |
Brunt, JR.; Harold W. ; et
al. |
May 8, 2014 |
CONSTRAINED FOLDED PATH RESONANT WHITE LIGHT SCINTILLATOR
Abstract
An optical emitter enabling conversion of light from a light
source. The optical emitter includes a first conic reflector
defining an aperture for receiving the light source, a second conic
reflector opposite the first conic reflector for collimating light
emitted by the light source, and a volumetric light conversion
element between at least a portion of the first reflector and at
least a portion of the second reflector. The optical emitter can
also include a convex mirror adjacent the vertex of the second
conic reflector, and an elliptical element adjacent the first conic
reflector. The light conversion element can include phosphor
dispersed in a resin to convert light from a first wavelength to
light of a second, longer, wavelength, wherein converted light is
emitted from the light conversion element.
Inventors: |
Brunt, JR.; Harold W.;
(Grand Rapids, MI) ; Bourget; Paul L.; (Kentwood,
MI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
LumenFlow Corp. |
Middleville |
MI |
US |
|
|
Assignee: |
LumenFlow Corp.
Middleville
MI
|
Family ID: |
43859835 |
Appl. No.: |
14/149042 |
Filed: |
January 7, 2014 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
12716337 |
Mar 3, 2010 |
8646949 |
|
|
14149042 |
|
|
|
|
Current U.S.
Class: |
362/346 |
Current CPC
Class: |
F21V 13/08 20130101;
F21K 9/60 20160801; H01L 33/58 20130101; H01L 33/50 20130101; F21V
7/0033 20130101 |
Class at
Publication: |
362/346 |
International
Class: |
F21V 13/08 20060101
F21V013/08 |
Claims
1. An optical emitter comprising: a first conic reflector including
a first reflector vertex and adapted to receive a light source
proximate the first reflector vertex; a second conic reflector
coaxial with the first reflector, the first and second conic
reflectors facing one another to define a folded path cavity
therebetween; and a volumetric light conversion element between at
least a portion of the first conic reflector and at least a portion
of the second conic reflector within the folded path cavity,
wherein the volumetric light conversion element is adapted to
down-convert light reflected between the first and second conic
reflectors and emit the down-converted light generally radially
outward from between the first and second conic reflectors.
2. The optical emitter of claim 1 wherein the first conic reflector
defines an aperture at the first reflector vertex.
3. The optical emitter of claim 1 wherein the volumetric light
conversion element interconnects the first and second conic
reflectors.
4. The optical emitter of claim 1 wherein the light conversion
element includes a plurality of wavelength-converting
phosphors.
5. The optical emitter of claim 1 wherein the light conversion
element includes an annular outer surface to form at least one of a
cylindrical exterior and a frusto-conical exterior.
6. The optical emitter of claim 1 wherein the first conic reflector
is elliptical.
7. The optical emitter of claim 1 wherein the second conic
reflector is parabolic.
8. The optical emitter of claim 1 wherein the first conic reflector
vertex is located at the focus of the second conic reflector.
9. The optical emitter of claim 1 further comprising a convex
mirror adjacent the second conic reflector and coaxial with the
first conic reflector.
10. The optical emitter of claim 1 further comprising an elliptical
element coaxial with the first conic reflector, wherein the first
reflector vertex is aligned with one of the elliptical element
focus and the elliptical element vertex.
11. A light emitter comprising: a first reflector defining an
aperture for a light source; a second reflector opposite the first
reflector, at least one of the first and second reflectors being a
conic, the first and second reflectors defining a folded path
cavity therebetween; and a volumetric light conversion medium
within the folded path cavity, the volumetric light conversion
medium including phosphor dispersed in a resin to convert light
emitted by the light source from a first wavelength to a second
wavelength, the second wavelength being longer than the first
wavelength, wherein the volumetric light conversion medium radiates
light at the second wavelength generally radially outward from
between the first and second reflectors.
12. The light emitter of claim 11 wherein the light conversion
medium is substantially solid.
13. The light emitter of claim 11 wherein: the light conversion
medium includes an annular outer surface; and the converted light
is emitted through the annular outer surface in a generally
toroidal pattern.
14. The light emitter of claim 11 wherein the first reflector is a
discontinuous conic reflector.
15. The light emitter of claim 11 wherein the light conversion
medium is injection molded.
16. An optical emitter comprising: a first conic reflector; a
second conic reflector opposite the first conic reflector; a third
conic reflector opposite the second conic reflector and adjacent
the first conic reflector; a negative minor adjacent the vertex of
the second conic reflector; and a translucent light conversion
element between the first and second conic reflectors, wherein the
translucent light conversion element emits light generally radially
outward from between the first and second reflectors.
17. The optical emitter of claim 16 wherein the first and third
conic reflectors define a coextensive aperture for a light
source.
18. The optical emitter of claim 16 wherein the first, second and
third conic reflectors are coaxial.
19. The optical emitter of claim 16 wherein the light conversion
element extends between at least a portion of the first conic
reflector and at least a portion of the second conic reflector.
20. The optical emitter of claim 16 wherein the light conversion
element includes phosphor dispersed in a resin to convert light
emitted by the light source from a first wavelength to a second
wavelength, the second wavelength being longer than the first
wavelength.
Description
FIELD OF THE INVENTION
[0001] This invention relates to light sources and the
manufacturing of light sources. In particular, this invention
relates to light sources and "light engines" that are used for
specific light tasks including, for example, flash lights,
automotive lights, streets and public areas as well as industrial
area lighting and medical illumination.
BACKGROUND OF THE INVENTION
[0002] With the development of the Light Emitting Diode (LED) for
use in the lighting industry, the opportunity for energy savings
continues to be significant for individuals and society as a whole.
A major hurdle impeding the realization of energy savings, however,
is the cost of installation or manufacturing. In particular, many
of the new technological improvements which greatly improve the
luminous efficacy of white LEDs come with disadvantages in the
manufacturing process.
[0003] In the manufacturing of a common white light LED, a phosphor
powder blend is normally mixed with an encapsulant and deposited as
a layer onto the surface of an emitter junction. Many emitter
junctions are narrow wavelength band blue or near ultraviolet (UV)
diodes, with a Full Width at Half Maximum (FWHM) of only 40 nm. The
phosphor blend is created to absorb the blue or UV wavelengths and
reemit broadband green to red wavelengths. The ratio of blue
absorption to secondary green to red emissions determines the color
temperature of the emitted white light. This is a straightforward
process and as such any improvements to increase the luminosity
output add complications to this process which can increase the
manufacturing cost.
[0004] Failures that plague the above approach include heat
degradation of the phosphor due to its proximity to the emitter
junctions. The emitter junctions run at relatively high
temperatures (>70 deg C.) against an ambient background (25 deg
C.). The encapsulant degrades with higher temperatures, often
resulting in discoloration and inefficient transmitters in the blue
or the visible wavelength region. Additionally, the encapsulant
acts as a thermal blanket on top of the emitter junctions causing a
further loss of efficiency. Close proximity of the phosphor layer
to the emitter junctions also creates an additional loss of white
luminosity, as efficient emitters by definition (thermo-dynamic
blackbodies) must also be efficient absorbers, thus white light
generated near the emitters is lost energy.
[0005] There exists another limitation to the above approach: the
relatively small area of emission. This creates an increase in
luminosity but spreads the light output over a small cone angle,
thus creating a very high brightness. Such brightness levels can
pose a threat to the human vision system and can contribute to
migraines, seizures, and temporary washout of the human eye. Yet
another limitation to the above approach is that it is not directly
scalable. It is not an easy task to increase luminosity by adding
more emitter junctions and thicker layers of phosphor. Such
endeavors increase the heat load in a non-linear way while adding
more of the "blanket" effect from the phosphor encapsulant.
SUMMARY OF THE INVENTION
[0006] The aforementioned problems are overcome by the present
invention which includes a volumetric light emitter that can be
manufactured independently of an emitter junction. The volumetric
light emitter includes a first conic reflector including an
aperture for a light source or an emitter junction, a second conic
reflector opposite the first conic reflector for collimating light
emitted by the light source, and a volumetric light conversion
element extending between at least a portion of the first reflector
and at least a portion of the second reflector.
[0007] In one aspect of the invention, the light conversion element
includes phosphor particles dispersed in a resin to convert light
emitted by the light source from a first wavelength to a second
wavelength, the second wavelength being longer than the first
wavelength. As disclosed, the light conversion element is
substantially solid, and includes an annular outer surface, wherein
light is emitted through the annular outer surface in a generally
toroidal pattern. Additionally, the light conversion element
preferably includes a cylindrical portion or a frusto-conical
portion being coaxial with the first and second conic
reflectors.
[0008] In another aspect of the invention, the first conic
reflector is elliptical and the second conic reflector is
parabolic. The volumetric light emitter includes a negative minor
adjacent the vertex of the second conic reflector. Additionally,
the volumetric light emitter includes an elliptical element
adjacent the first conic reflector, wherein the first conic
reflector and the elliptical element define a coextensive aperture
for the light source.
[0009] The volumetric light emitter can be optically bonded to one
or more emitter junctions as a final step, thus creating a simple
volumetric light engine wherever a light filament or arc may be
used. This invention acts as a bridging technology between LED
junction manufacturers and luminaire manufacturers, which delivers
the lighting requirements to the end user. This allows for a common
design to be implemented with a variety of LED junctions and heat
sink arrangements. Another benefit of this invention lies in
integrating three specific optical tasks into one simple and
manufacturable form. The three optical tasks are: 1) light
gathering and placement from emitter junctions, 2) improving
utilization and containment of pump light, and 3) down conversion
and emission of white light. This integration opens up new designs
for luminaires and possesses the benefit of ease of retrofitting
older structures with LED sources.
[0010] These and other advantages and features of the invention
will be more fully understood and appreciated by reference to the
drawings and the description of the current embodiments.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 is a perspective view of a first embodiment of the
invention.
[0012] FIG. 2 is a cross-sectional view of the volumetric light
emitter in FIG. 1.
[0013] FIG. 3 is an optical ray trace of a cross-sectional view of
a variation of the volumetric light emitter in FIG. 1.
[0014] FIG. 4 is an optical ray trace of a cross-sectional view of
a variation of the volumetric light emitter in FIG. 1.
[0015] FIG. 5 is an optical ray trace of a cross-sectional view of
the volumetric light emitter in FIG. 1.
[0016] FIG. 6 is an optical ray trace of a cross-sectional view of
the volumetric light emitter in FIG. 1 illustrating a ray trace
impinging a convex mirror.
[0017] FIG. 7 is an optical ray trace of the volumetric light
emitter in FIG. 1 illustrating a ray trace impinging the outer
annular surface of the light conversion element.
[0018] FIG. 8 is an optical ray trace of a cross-sectional view of
a variation of the volumetric light emitter in FIG. 1.
[0019] FIG. 9 is an optical ray trace of a cross-sectional view of
a second embodiment of the present invention.
[0020] FIG. 10 is an optical ray trace of a cross-sectional view of
a third embodiment of the present invention.
[0021] FIG. 11 is an optical ray trace of a cross-sectional view of
a fourth embodiment of the present invention.
[0022] FIG. 12 is a graph illustrating the output spectral
distribution of a phosphor light conversion element within a
Constrained Folded Path Cavity in accordance with an embodiment of
the present invention.
DESCRIPTION OF THE CURRENT EMBODIMENT
[0023] A main focus of conventional LED research is to maximize
luminosity while reducing the energy consumption, i.e., luminous
efficacy. Even though this seems to be the best path to success, it
is fraught with gains in luminosity which are not practical for the
mass production environment that white LED-based luminaries will
need to be at. A wiser approach is to look at the costs of
producing white luminosity. These costs break down to operational
costs and implementation costs. It is the great savings in
operational costs to our society that is driving the development of
this technology. However it is the implementation cost that becomes
the biggest barrier to moving forward. The present invention
addresses this cost barrier--the implementation cost barrier. This
is the problem we as a society are trying to solve; the
maximization of white luminosity while reducing the number of
manufacturing steps involved in reaching the end use luminaire. As
explained herein, the present invention can perform three distinct
optical functions in a single molded component. The first optical
task is to gather the light from the LED junction source and
convert it to a more usable format. The second optical task is to
create a gain function in the intensity of the Deep Blue Light
(DBL) while constraining the DBL losses. The third optical task is
to create an optical environment for best down conversion
efficiency. As explained below, the three optical functions lead to
improvements on seven parameters which cause the luminosity to
produce high performance and which offer a simple manufacturable
design. Due to its single piece layout, the present invention also
lends itself to cost effective manufacturing.
[0024] With the above optical tasks in mind, the present invention
provides a volumetric light emitter which constrains DBL into a
light conversion chamber to thereby control losses and maximize the
probability of white light generation via phosphorescence. This is
achieved, in part, by making use of a concept from laser physics:
the resonant cavity. The purpose of a resonant cavity is to confine
the DBL such that the only loss in the DBL is from the excitation
of the phosphors within the resonator structure. The Applicant
acknowledges that the requirements of an operational laser resonant
cavity--High Q status, cavity length=N.times.Wavelength, Spectral
Line width of 1 nm, etc--cannot be achieved from an LED source. The
terms `resonant cavity` and `resonant structure` are used as a
descriptor in creating a visual reference for describing the
present invention. This resonant structure, or Constrained Folded
Path Cavity (CFPC), possesses reflectors at opposite ends. One
purpose of the CFPC is to cause the DBL to repeat its path of
propagation a number of times over, while reducing the number of
exit paths that allow the DBL to escape. Current repeat
propagations vary between 4 and 40, depending on the resonant model
chosen, not in the thousands or millions as required for a laser
resonant cavity. This will increase the intensity of DBL while
keeping it contained within a known volume. One embodiment of the
resonant structure is the hemi-confocal cavity structure as shown
in FIGS. 1-8, though the invention may utilize other forms of
multi-pass folded structures.
[0025] In addition to constraining DBL in a resonant cavity, the
volumetric light emitter radiates Down-Converted White Light (DCWL)
in a toroidal or a spherical pattern. This is accomplished by using
a remote phosphor blended into a resin material, which forms a
three-dimensional or volumetric light conversion element in the
resonant structure of the CFPC, thus creating a volumetric white
light radiator In the present embodiment, a phosphor, such as
EY4453 by Intematix, is premixed into an acrylic, polycarbonate,
Nylon, or polystyrene resin for injection molding, such as Nylon
6/66 by BASF (marketed as ULTRAMID.RTM.). The phosphor-doped light
conversion element can optionally be molded with the curvatures of
the reflectors of the CFPC. Additionally, the density of the
phosphor is such that the volumetric light conversion element is
translucent to the DBL, not opaque. For example, if the DBL will
make 6 reflections within the CFPC, then it is desirable to absorb
16.67% per pass with total absorption at 100% for 6 reflections. It
is also possible to utilize this technology with castings,
extruding, press forms, or machining to achieve the desired
form.
[0026] The volumetric white light emitter of the present invention
may also be used in conjunction with an optical coupler, such as
the optical coupler disclosed in U.S. patent application Ser. No.
12/405,398 to Bourget, filed on Mar. 17, 2009, and titled "High
Efficiency Optical Coupler," which is incorporated herein by
reference. In particular, a High Efficiency Optical Coupler (HEOC)
can convert a Lambertian source into a non-Lambertian radiator to
reduce the Numerical Aperture (N.A.) of the source light. This
improves the "usability" of the DBL. By choosing the correct radii
and conics, a bi-modal intensity pattern output can be created, and
the HEOC can to collect up to 98% of all DBL and place it where it
is most likely that blue photons will interact with phosphor
materials. Accordingly, the present invention combines a HEOC, a
constrained folded path cavity, and a toroidal radiator into a
single element. Several benefits can accrue from the present
invention:
[0027] (1) more efficient transfer (up to 98%) of DBL into the
phosphorescence region;
[0028] (2) "resonant" coupling within the phosphorescence region
for multi-pass intensity gain of DBL;
[0029] (3) reduced white light loss due to reabsorption at the
emission junction(s);
[0030] (4) less complex heat sink and heat sink costs due to heat
flow improvement attributed to the flexibility of location of the
emitter junction(s);
[0031] (5) improved temperature stability and less temperature
light output degradation due to remote phosphor effect;
[0032] (6) fine tuning of chromaticity based on cavity length;
and
[0033] (7) reduced manufacturing loss yields due to fewer
mechanical operations at the emitter junction(s).
[0034] Accordingly, the embodiments of present invention provide
multiple improvements.
I. First Embodiment
[0035] A volumetric white light emitter in accordance with an
embodiment of the present invention is illustrated in FIGS. 1-8 and
generally designated 20. The volumetric white light emitter 20
includes a first conic reflector 22, a second conic reflector 24,
and a volumetric light conversion element 26 extending between the
first conic reflector 22 and the second conic reflector 24. The
first conic reflector 22 defines an aperture 28 for a light source
or emitter junction (not shown), and the second conic reflector 24
is orientated opposite the first conic reflector for reflecting
light from the light source toward the first reflector 22. A convex
minor 32 is positioned adjacent the vertex 34 of the second conic
reflector 24. The second conic reflector 24 is shown as parabolic
with a focus at the aperture 28 of the first conic reflector 22.
Additionally, an elliptical element 38 is positioned adjacent the
first conic reflector 22. The elliptical element 38 defines an
aperture 40 coincident with the first reflector aperture 28 to
direct light from the light source toward the second conic
reflector 24. The volumetric light conversion element 26 includes
phosphor particles dispersed in a hardened resin to convert light
emitted by the light source from a first wavelength to a second
wavelength, the second wavelength being longer than the first
wavelength. The volumetric light conversion element 26 also
includes an outer annular surface 30 to radiate converted light in
a generally toroidal pattern. As also shown in FIGS. 1-2, the
volumetric light conversion element 26 is generally frusto-conical
or cylindrical, and is coaxial with the first and second conic
reflectors 22, 24.
[0036] As explained below, the volumetric white light emitter 20
can be adapted to accommodate a specific LED based on its peak
emission wavelength. For example, the volumetric white light
emitter 20 of the present embodiment is configured to down-convert
DBL light from an LED junction having a DBL emission wavelength of
455 nm. The volumetric light conversion element 26 includes a
phosphor chosen with a main radiation peak of 570 nm (Yellow) and a
FWHM of 90 nm--a typical "off the shelf" phosphor material. The
design goal is to convert at least 80% of the emitted blue light
into the yellow light output. The blending of the remaining blue
light and the phosphorescent yellow light creates to the human eye
a lower Color Rendering Index (CRI) of white light (while lower CRI
light is not accurate for color measurement, it is adequate for
many general illumination applications). For a single junction
system with an emission area of 1.3 mm sq. having 1.14 mm on a
side, typical operational parameters include an operating current
(lop) of 350 mAmps with a voltage drop of 3.4 Vdc for a power
consumption of 1.2 Watts. A typical output conversion efficiency of
25% yields a radiant power of 0.3 Watts. Expressed as luminosity,
the value at 455 nm with 36.5 lm/Watt.times.0.3 Watts equals 11
lumens of blue light.
[0037] The second conic reflector 24 is selected to have a diameter
about ten times larger than the baseline of the emitter. In the
present embodiment, this sets the operational diameter of the
second conic reflector 24 at 11. mm. For a surface mount junction,
the angle for the FWHM of the Lambertian intensity distribution is
typically 60 degrees, corresponding to an N.A. of 0.866. For light
propagating through an acrylic resin medium (Index of
Refraction=1.497), this same N.A. creates the angle of intensity of
35.4 degrees. This angle is used in combination with the
operational diameter to calculate the radius of the second
reflector 24 and the cavity length. As noted above, one purpose of
the second conic reflector 24 is to collimate the reflected rays
and direct them toward the first conic reflector 22. From the Minor
Formula, a mirror's radius being equal to twice the focal length,
sets the radius of the second conic reflector 24 equal to the twice
the length from the emitter junctions to the second conic reflector
24:
Radius of Second Reflector=2.times.(11.4 mm/2)/Tan
35.4.degree.=16.0 mm.
This suggests that the cavity volume be roughly 0.82 cm.sup.3 from
the following formula:
V=Pi.times.R.sup.2.times.L
While the second conic reflector 24 is parabolic with a numerical
conic value of -1.00, it is also possible to make variations in the
conic, thus changing the shape from hyperbolic to spherical based
on the desired cavity constraints.
[0038] The purpose of the first conic reflector 22 is to gather the
collimated light from the second conic reflector 24 and bring it to
a focal plane. It is desirable, however, to set the focal plane to
intersect a point on the second conic reflector 24 such that the
ray path of the DBL crosses the main Z axis 42 and retraces its
path back to the emitter junctions. The choice here is how many
reflective paths to have between the first and second conic
reflectors 22, 24. In the current embodiment we have 6 reflections
as illustrated in FIG. 3, however some models have demonstrated up
to 40 reflections as illustrated in FIG. 4. The number of
reflective paths is based on the phosphor density appropriate to
create the down converted white light. More reflective paths will
mean more DBL will be absorbed for a given density of phosphor.
This implies a warmer 3000 k type of light will be generated. In
the current embodiment, the first conic reflector 22 is an ellipse
with a conic value of -0.8., though a range from -0.7 to -0.9 is
appropriate depending on the design of resonator. As mentioned
above with the second conic reflector 24, the first conic reflector
22 may take any conic form where the refocus conditions allow a
retrace over previous paths As shown in FIG. 5, a small positive
element, for example an elliptical minor 38, is placed at the
vertex of the first conic reflector 22. The elliptical mirror 38
gathers DBL that is emitted at or near 90.degree. to the surface of
the emitter junctions. Another benefit is the reduction of the
coupler outside diameter which can be achieved by breaking the
first conic reflector 22 into two discontinuous elliptical curves.
The conic constant of the first conic reflector 22 is maintained
while the radius of curvature and the diameter are significantly
reduced. The curves can be produced as separate components or as a
single molded or machined element.
[0039] It is preferable to add a small negative element, for
example a convex minor 32, placed at or adjacent the vertex 34 of
the second conic reflector 24 to diverge the near axial propagated
light emitted from the emitter junction(s). Without this negative
element 32, reflected DBL off of the second conic reflector 24 can
retrace its path along the main axis 42 and intersect the
junction(s) surface. The diameter of the negative element 32 will
normally not be greater than one-third of the diameter of the
second conic reflector 24. As shown in FIG. 6, the vertex 44 of the
negative element 32 is located before the vertex 34 of the second
conic reflector 34 along the main Z axis 42. The radius of the
negative element is chosen so as to transfer the reflected rays to
the outside of the first conic reflector 22. As shown in FIG. 7,
the rays will normally reflect off of the first conic reflector 22
and intersect the outside wall 30 of the resonant cavity 20 with a
shallow angle of incidence to have substantial internal reflection,
assisting in keeping the DBL confined within the cavity structure.
After the placement of the negative surface a refocusing of the
first conic reflector 22 may be required. The focal point of the
first conic reflector 22 can be on the surface of the negative
element 32 to facilitate the retracing of the optical path.
[0040] The luminous output spectral distribution of the volumetric
white light generator of FIGS. 1-8 is illustrated in FIG. 12. The
solid line represents the luminous output from a known phosphor,
and the broken line represents the same phosphor operating within a
constrained folded path cavity. The difference in the output
illustrates increased lumens produced by the cavity structure in
accordance with the present embodiment. Though shown above in
connection with an LED having a DBL emission wavelength of 455 nm,
the volumetric toroidal radiator 20 can also be adapted to
accommodate an LED with an emission wavelength of 405 nm, for
example. The phosphor blend may have a broadband radiation peak
from 480 nm (cyan) to 630 nm (red) and a FWHM 200 nm--a custom
blended phosphor material. Again, the goal is to convert up to 100%
of the emitted blue light into a broadband white light output by
constraining the DBL in the volumetric white light radiator 20 and
down-converting DBL light via the phosphorescent element 26. This
brings forth a phosphorescent white light which to the human eye
has a higher CRI rating. To accommodate the DBL wavelength of 405
nm, the length of the volumetric toroidal radiator 20 is increased
to allow more absorption of the DBL on a per reflection basis as
shown in FIG. 8. This is in combination with more reflections, for
example 8 or 10, within the resonant cavity. This will dictate a
longer radius on the first and second reflectors 22, 24 as well as
on the negative element 32. The conic constant of the first conic
reflector 22 may also increase to drive the ellipse to act more as
a parabolic form.
II. Second Embodiment
[0041] A folded spherical cavity 50 in accordance with another
embodiment of the present invention is shown in FIG. 9. The folded
spherical cavity 50 includes a spherical reflector 52, a planar
reflector 54 opposite the spherical reflector 52, and a volumetric
light conversion element 56 extending between the spherical
reflector 52 and the planar reflector 54. The spherical reflector
52 defines an aperture or seat (not shown) for a light source or
emitter junction. Though not shown, a convex minor can be
positioned adjacent the planar reflector 54. Additionally, an
elliptical element (not shown) can be positioned adjacent the
spherical reflector 52. The elliptical element can also include an
aperture coincident with the spherical reflector aperture to direct
light from the light source toward the planar reflector 54. The
volumetric light conversion element 56 includes phosphor particles
dispersed in a resin to convert light emitted by the light source
from a first wavelength to a second wavelength, the second
wavelength being longer than the first wavelength. The volumetric
light conversion element 56 also includes an outer annular surface
60 to radiate converted light in a generally toroidal pattern. As
also shown in FIG. 9, the volumetric light conversion element 56
includes a generally frusto-conical portion 58 proximate the planar
reflector 54 and coaxial with the spherical reflector 52.
III. Third Embodiment
[0042] A folded transverse cavity 70 in accordance with an
embodiment of the present invention is shown in FIG. 10. The folded
transverse cavity 70 includes a frusto-conical reflector 72, a
conic reflector 74 opposite the frusto-conical reflector 72, and a
volumetric light conversion element 76 extending between at least a
portion of the frusto-conical reflector 72 and at least a portion
of the conic reflector 74. The frusto-conical reflector 72 defines
an aperture or seat (not shown) for a light source or emitter
junction (not shown). The conic reflector 74 is orientated opposite
the frusto-conical reflector 72 for reflecting light from the light
source toward the frusto-conical reflector 72. A convex minor 78 is
positioned adjacent the vertex 80 of the conic reflector 74. The
conic reflector 74 is shown as parabolic with a focus at the
aperture of the frusto-conical reflector 72. Though not shown, an
elliptical element can be positioned adjacent the frusto-conical
reflector 72, including an aperture coincident with the first
reflector aperture to direct light from the light source toward the
conic reflector 74. The volumetric light conversion element 76
includes phosphor particles dispersed in a resin to convert light
emitted by the light source from a first wavelength to a second
wavelength, the second wavelength being longer than the first
wavelength. The volumetric light conversion element 76 also
includes an outer annular surface 82, radiating converted light
through the outer annular surface 82 in a generally toroidal
pattern. As also shown in FIG. 10, the volumetric light conversion
element 76 is generally cylindrical and coaxial with the conic
reflector 74.
IV. Fourth Embodiment
[0043] A folded confocal cavity 90 in accordance with an embodiment
of the present invention is shown in FIG. 11. The folded confocal
cavity 90 includes a planar reflector 92, a conic reflector 94
opposite the planar reflector 92, and a volumetric light conversion
element 96 extending between at least a portion of the planar
reflector 92 and a portion of the conic reflector 94. The planar
reflector 92 defines an aperture or seat (not shown) for a light
source or emitter junction (not shown). The conic reflector 94 is
orientated opposite the planar reflector 92 for reflecting light
from the light source toward the planar reflector 92. A convex
minor 98 is positioned adjacent the vertex 100 of the conic
reflector 94. The conic reflector 94 is shown as parabolic with a
focus at the aperture of the planar reflector 92. Though not shown,
an elliptical element can be positioned adjacent the planar
reflector 92, including an aperture coincident with the planar
reflector aperture to direct light from the light source toward the
conic reflector 94. The volumetric light conversion element 96
includes phosphor particles dispersed in a hardened resin to
convert light emitted by the light source from a first wavelength
to a second wavelength, the second wavelength being longer than the
first wavelength. The volumetric light conversion element 96 also
includes an outer annular surface 102, radiating converted light
through the outer annular surface 102 in a generally toroidal
pattern. As also shown in FIG. 11, the volumetric light conversion
element 96 is generally cylindrical and coaxial with the conic
reflector 94.
V. Conclusion
[0044] The above embodiments include a volumetric light emitter
that can be manufactured independently of the emitter junction or
other light source. The volumetric light emitter can be optically
bonded to the emitter junctions or other light source as a final
step, thus creating a simple volumetric light engine to radiate
down-converted white light in a toroidal, spherical, or other
pattern.
[0045] The above descriptions are those of current embodiments of
the invention. Various alterations and changes can be made without
departing from the spirit and broader aspects of the invention as
set forth in the following claims, which are to be interpreted in
accordance with the principles of patent law including the Doctrine
of Equivalents.
* * * * *