U.S. patent application number 17/080542 was filed with the patent office on 2021-02-18 for device for converting electromagnetic radiation into electricity, and related systems and methods.
This patent application is currently assigned to LaserMotive, Inc.. The applicant listed for this patent is LaserMotive, Inc.. Invention is credited to David Bashford, Jordin T. Kare, Thomas J. Nugent, JR..
Application Number | 20210050465 17/080542 |
Document ID | / |
Family ID | 1000005197045 |
Filed Date | 2021-02-18 |
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United States Patent
Application |
20210050465 |
Kind Code |
A1 |
Kare; Jordin T. ; et
al. |
February 18, 2021 |
Device for Converting electromagnetic Radiation into Electricity,
and Related Systems and Methods
Abstract
A device for converting electromagnetic radiation into
electricity comprises an expander that includes a conical shape
having an axis and a curved surface that is configured to reflect
electromagnetic radiation away from the axis to expand a beam of
the electromagnetic radiation; and one or more energy conversion
components configured to receive a beam of electromagnetic
radiation expanded by the expander, and to generate electricity
from the expanded beam of electromagnetic radiation. With the
expander's curved surface, a beam of electromagnetic radiation that
is highly concentrated--has a large radiation flux--may be
converted into a beam that has a larger cross-sectional area.
Moreover, one can configure, if desired, the curved surface to
provide a substantially uniform distribution of radiation across
the expanded cross-sectional area. With such an expanded beam the
one or more energy conversion components can efficiently convert
some of the electromagnetic radiation into electricity.
Inventors: |
Kare; Jordin T.; (Seattle,
WA) ; Nugent, JR.; Thomas J.; (Bellevue, WA) ;
Bashford; David; (Kent, WA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
LaserMotive, Inc. |
Kent |
WA |
US |
|
|
Assignee: |
LaserMotive, Inc.
Kent
WA
|
Family ID: |
1000005197045 |
Appl. No.: |
17/080542 |
Filed: |
October 26, 2020 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
14263858 |
Apr 28, 2014 |
10825944 |
|
|
17080542 |
|
|
|
|
61816784 |
Apr 28, 2013 |
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L 31/042 20130101;
G02B 19/0028 20130101; G01S 3/78 20130101; G02B 19/0038 20130101;
G02B 27/0983 20130101; G02B 17/084 20130101; H02S 20/32 20141201;
F21S 11/00 20130101; H01L 31/0521 20130101; G02B 17/086 20130101;
H01L 31/0232 20130101; H01L 31/0543 20141201; G01S 3/7861 20130101;
Y02E 10/52 20130101; G02B 19/0023 20130101; G02B 5/001 20130101;
G02B 19/009 20130101; G02B 19/0033 20130101; H02S 20/00 20130101;
H01L 31/0547 20141201; G02B 3/08 20130101; G02B 27/0911 20130101;
G02B 21/04 20130101 |
International
Class: |
H01L 31/054 20060101
H01L031/054 |
Claims
1. A device for converting electromagnetic radiation into
electricity, the device comprising: an expander having an axis and
a curved surface that is configured to reflect electromagnetic
radiation away from the axis to expand a beam of the
electromagnetic radiation, the curved surface including at least
two conical segments each shaped as a truncated cone and having a
common axis, each conical segment having a selected angle of
incidence to the common axis, wherein the at least two conical
segments have different angles of incidence to the common axis; and
an energy conversion component disposed to receive the expanded
beam and configured to generate electricity from the expanded
beam.
2. The device of claim 1, further comprising a reflective surface
disposed between the expander and the energy conversion component
and configured to further reflect electromagnetic radiation
reflected from the expander toward the energy conversion
component.
3. The device of claim 1, further comprising a heat sink configured
to conduct heat away from the energy conversion component.
4. The device of claim 1, wherein: the energy conversion component
includes a height measured along the direction of the common axis,
and the expander includes a height measured along the direction of
the common axis that is longer than the height of the energy
conversion component.
5. The device of claim 1, further comprising one or more additional
energy conversion components, wherein the energy conversion
component and the additional energy conversion components are
disposed symmetrically around the common axis.
6. The device of claim 5, wherein the energy conversion component
and the additional energy conversion components, together, form a
polygonal prism shape that surrounds the expander.
7. The device of claim 1, further comprising an optical component
configured to modify electromagnetic radiation before the expander
expands the electromagnetic radiation.
8. The device of claim 7, wherein the optical component includes at
least one of the following: a lens, a prism, a diffuser, a filter,
and a mirror.
9. The device of claim 1, wherein the selected angles of incidence
of the at least two conical segments are selected to create an
overlapping vertical distribution of irradiance at the energy
conversion component.
10. A device for converting electromagnetic radiation into
electricity, comprising: an expander having a shape symmetric about
a rotational axis and a reflective surface, wherein the reflective
surface includes multiple angles relative to a line parallel to the
axis, the multiple angles selected to expand a beam of
electromagnetic radiation into an expanded beam; and a plurality of
energy conversion components disposed to receive the expanded beam
and configured to generate electricity from the expanded beam,
wherein the multiple angles are selected to change a spatial
distribution of electromagnetic energy of the beam between the
reflective surface and a member of the plurality of energy
conversion components.
11. The device of claim 10, wherein the multiple angles are
selected to cause two portions of the expanded beam to overlap at
the member of the plurality of energy conversion components.
12. The device of claim 10, wherein a cross-section of the expander
through the axis has a shape including curved sides, the curved
sides being part of the reflective surface.
13. The device of claim 10, wherein a cross-section of the expander
through the axis has a shape including sides having a plurality of
straight line segments, the sides having a plurality of straight
line segments being part of the reflective surface.
14. The device of claim 10, further comprising a reflective surface
disposed between the expander and the plurality of energy
conversion components and configured to further reflect
electromagnetic radiation reflected from the expander toward the
plurality of energy conversion components.
15. The device of claim 10, further comprising a heat sink
configured to conduct heat away from at least one of the plurality
of energy conversion components.
16. The device of claim 10, wherein the expander is shaped to
compress the height of the reflected light beam transverse to its
direction of travel between leaving the expander and reaching a
member of the plurality of energy conversion components.
17. The device of claim 10, wherein the plurality of energy
conversion components are arranged in a polygonal prism shape.
18. The device of claim 10, further comprising an optical component
configured to modify electromagnetic radiation before the expander
expands the electromagnetic radiation.
19. The device of claim 18, wherein the optical component includes
at least one of the following: a lens, a prism, a diffuser, a
filter, and a mirror.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS AND PRIORITY CLAIMS
[0001] This application claims priority under 35 U.S.C. .sctn. 121
as a divisional of commonly owned U.S. patent application Ser. No.
14/263,858, filed Apr. 28, 2014, issuing Nov. 3, 2020 as U.S. Pat.
No. 10,825,944, which claimed priority under 35 U.S.C. .sctn.
119(e) to commonly owned U.S. Provisional Patent Application No.
61/816,784, filed Apr. 28, 2013. Each of these previous patent
applications is incorporated by reference herein.
BACKGROUND
[0002] Laser light or other monochromatic light sources can be
converted into electricity using photovoltaic converters comprising
an array of photovoltaic cells. Multiple cells or groups of cells
may be connected in series, to raise the output voltage of the
array compared to the output voltage of one cell.
[0003] When laser power is transmitted through free space,
photovoltaic receivers may be physically configured similarly to
solar photovoltaic arrays, using essentially flat panels of cells.
In some cases, reflectors or lenses may be used to concentrate the
received light onto a smaller area, increasing the light intensity
and reducing the size and/or number of cells needed.
[0004] Transmission of laser power over an optical fiber to a
photovoltaic receiver presents an additional challenge. The light
emerging from an optical fiber is typically very intense, and forms
a conical beam with a centrally-peaked, nonuniform brightness
(power per unit solid angle). Systems which transmit low power
(.about.2 W or less electrical output) over fiber have used simple
planar arrays of, typically, 1-4 photovoltaic cells arranged around
the beam center, so that light is evenly divided among cells (but
unevenly distributed over each cell). However, this approach is
practical only for small numbers of cells which can be arranged
radially around a point.
[0005] Various means of expanding a laser beam from a fiber to
larger area and generating a uniform intensity "top hat" beam of a
desired shape are known, using, for example, axicon lenses or
lenslet arrays. However, these tend to require large transmissive
optical elements and long optical paths within the receiver, and in
many cases yield a circular beam which is not well matched to
typically square or rectangular arrays of PV cells.
[0006] It is known to focus light through an aperture into an
approximately spherical cavity lined with photovoltaic cells, such
that light which is reflected from or re-emitted by one cell may be
captured by another cell. However, this results in highly
non-uniform illumination of cells, is bulky and difficult to
fabricate, and tends to require a large number of cells to cover
the inside of an entire sphere.
SUMMARY
[0007] In an aspect of the invention, a device for converting
electromagnetic radiation into electricity comprises an expander
that includes a conical shape having an axis and a curved surface
that is configured to reflect electromagnetic radiation away from
the axis to expand a beam of the electromagnetic radiation; and one
or more energy conversion components configured to receive a beam
of electromagnetic radiation expanded by the expander, and to
generate electricity from the expanded beam of electromagnetic
radiation. With the expander's curved surface, a beam of
electromagnetic radiation that is highly concentrated--has a large
radiation flux--may be converted into a beam that has a larger
cross-sectional area. Moreover, one can configure, if desired, the
curved surface to provide a substantially uniform distribution of
radiation across the expanded cross-sectional area. With such an
expanded beam the one or more energy conversion components can
efficiently convert some of the electromagnetic radiation into
electricity.
[0008] In another aspect of the invention a method for converting
electromagnetic radiation into electricity comprises reflecting a
beam of electromagnetic radiation from a curved surface of an
expander's conical shape away from an axis of the expander's
conical shape to expand the beam of electromagnetic radiation; one
or more energy conversion components receiving the reflected
electromagnetic radiation; and one or more energy conversion
components absorbing some of the energy in the reflected
electromagnetic radiation to generate an electric potential across
the energy conversion component.
BRIEF DESCRIPTION OF THE FIGURES
[0009] FIG. 1 illustrates a perspective, cutaway view of a device,
according to an embodiment of the invention.
[0010] FIG. 2A illustrates a partial cross-section of a device, a
partial cross-section of an electromagnetic radiation beam
approaching the expander of the device, and a partial cross-section
of the electromagnetic beam reflected by the expander, according to
an embodiment of the invention.
[0011] FIG. 2B graphically illustrates the distribution of the
radiation within the partial cross-section of the electromagnetic
radiation approaching the expander in FIG. 2A, according to an
embodiment of the invention.
[0012] FIG. 2C graphically illustrates the distribution of the
radiation flux of the partial cross-section of the electromagnetic
radiation approaching the expander in FIG. 2A, according to an
embodiment of the invention.
[0013] FIG. 3A illustrates a partial cross-section of a device, a
partial cross-section of an electromagnetic radiation beam
approaching the expander of the device, and a partial cross-section
of the electromagnetic beam reflected by the expander, according to
another embodiment of the invention.
[0014] FIG. 3B graphically illustrates the distribution of the
radiation within the partial cross-section of the electromagnetic
radiation approaching the expander in FIG. 3A, according to an
embodiment of the invention.
[0015] FIG. 3C graphically illustrates the distribution of the
radiation flux of the partial cross-section of the electromagnetic
radiation approaching the expander in FIG. 3A, according to an
embodiment of the invention.
[0016] FIG. 4A illustrates a partial cross-section of a device, a
partial cross-section of an electromagnetic radiation beam
approaching the expander of the device, and a partial cross-section
of the electromagnetic beam reflected by the expander, according to
yet another embodiment of the invention.
[0017] FIG. 4B graphically illustrates the distribution of the
radiation within the partial cross-section of the electromagnetic
radiation approaching the expander in FIG. 4A, according to an
embodiment of the invention.
[0018] FIG. 4C graphically illustrates the distribution of the
radiation flux of the partial cross-section of the electromagnetic
radiation approaching the expander in FIG. 4A, according to an
embodiment of the invention.
[0019] FIG. 5A illustrates a partial cross-section of a device, a
partial cross-section of an electromagnetic radiation beam
approaching the expander of the device, and a partial cross-section
of the electromagnetic beam reflected by the expander, according to
still another embodiment of the invention.
[0020] FIG. 5B graphically illustrates the distribution of the
radiation within the partial cross-section of the electromagnetic
radiation approaching the expander in FIG. 5A, according to an
embodiment of the invention.
[0021] FIG. 5C graphically illustrates the distribution of the
radiation flux of the partial cross-section of the electromagnetic
radiation approaching the expander in FIG. 5A, according to an
embodiment of the invention.
[0022] Each of FIGS. 6A-6D illustrates a partial view of a device
that includes an optical component, each according to a respective
embodiment of the invention.
[0023] FIG. 7 illustrates a partial cross-section of a device,
according to another embodiment of the invention.
[0024] FIG. 8A illustrates a partial cross-section of a device, a
partial cross-section of an electromagnetic radiation beam
approaching the expander of the device, and a partial cross-section
of the electromagnetic beam reflected by the expander, according to
another embodiment of the invention.
[0025] FIG. 8B graphically illustrates the distribution of the
radiation within the partial cross-section of the electromagnetic
radiation approaching the expander in FIG. 8A, according to an
embodiment of the invention.
[0026] FIG. 8C graphically illustrates the distribution of the
radiation flux of the partial cross-section of the electromagnetic
radiation approaching the expander in FIG. 8A, according to an
embodiment of the invention.
[0027] FIGS. 9A and 9B illustrate a device that incorporates an
optical component for transmitting or receiving a secondary
wavelength of electromagnetic radiation, according to another
embodiment of the invention.
[0028] FIG. 10 illustrates a device, according to another
embodiment of the invention.
[0029] FIG. 11 illustrates a device, according to yet another
embodiment of the invention.
DETAILED DESCRIPTION
[0030] FIG. 1 illustrates a perspective, cutaway view of a device
100 for converting electromagnetic radiation into electricity,
according to an embodiment of the invention. The device 100
comprises an expander 120 that includes a conical shape having an
axis 122 (here an axis of symmetry for the conical shape) and a
curved surface 124 that is configured to reflect a beam of
electromagnetic radiation 132 (here emanating from the optical
fiber 130) away from the axis 122 to expand the beam of
electromagnetic radiation (also not shown). The device 100 also
includes one or more energy conversion components 110 configured to
receive the expanded beam of electromagnetic radiation, and to
generate electricity from the expanded beam.
[0031] With the expander's curved surface 124, a beam of
electromagnetic radiation that is highly concentrated--has a large
radiation flux--can be converted into a beam that has a larger
cross-sectional area. Moreover, one can configure, if desired, the
curved surface 124 to provide a substantially uniform distribution
of radiation across the expanded cross-sectional area. With such an
expanded beam the one or more energy conversion components 110 can
efficiently convert some of the electromagnetic radiation into
electricity.
[0032] In this and other embodiments, the receiver 100 comprises a
generally cylindrical array of energy conversion components 110
that include photovoltaic cells, arranged around a central
reflective expander 120. In other embodiments, the energy
conversion components 110 may include other means of converting
light to electricity, such as thermoelectric or thermo-photovoltaic
converters. The expander 120 receives light from an optical fiber
130 aligned with the axis 122 of the expander 120 and the
photovoltaic array. An input optical assembly 140 may be used to
couple light out of the optical fiber 130 and/or to shape the beam
from the fiber 130, for example to increase its divergence. In some
embodiments the assembly 140 may also comprise a connector allowing
the optical fiber 130 to be detached from the receiver, and/or a
bearing to allow the optical fiber 130 to rotate about an axis such
as the axis 122 without becoming twisted.
[0033] Photovoltaic cells, as an example of an energy conversion
component 110, operate most efficiently when the incident intensity
of the electromagnetic radiation is even across the cell's surface.
Laser sources often deliver electromagnetic radiation with an
intensity profile that is not uniform, for example a Gaussian
profile. In some embodiments, the expander shape may be designed to
modify the electromagnetic radiation to a desired intensity profile
at the surface of the energy conversion component 110, for example
a flat (uniform) intensity profile. Other profiles are possible,
depending on the configuration of the energy conversion component
110. For example, a gradient in intensity from top to bottom may be
desired.
[0034] The expander 120 is configured to reflect the beam 132 from
the fiber 130 onto the photovoltaic cells. The receiver 100 may be
enclosed in a housing 150, which may comprise various elements such
as the photovoltaic array support 152, a heat sink 154, and top and
bottom covers 156 and 158.
[0035] In some embodiments, the energy conversion components 110
may be rigid, flat, and essentially rectangular, and the array of
components may form a polygonal approximation to a section of a
cylinder. In other embodiments, the components 110 may be
rectangular and flexible, and may thus be curved into a true
cylinder or close approximation thereto. In still other
embodiments, the components 110 may have other shapes, for example
triangular or hexagonal, and may tile the inner surface of the
receiver 100 to form an approximation of a cylinder segment. In yet
other embodiments, the array of components 110 may approximate a
segment of a cone or a sphere. In such embodiments the components
110 may have shapes which efficiently cover the array area, e.g.,
trapezoidal shapes which fit into a section of a cone, or
alternating rectangular and triangular components 110.
Alternatively, the array area may be incompletely covered, e.g., by
rectangular components 110 with triangular gaps between them.
[0036] Still referring to FIG. 1, the covers 156 and 158 are shown
as conical but may be flat, dome-shaped, or some other shape suited
to the optical and mechanical requirements of the receiver 100.
Some fraction of electromagnetic radiation usually reflects off
nearly any surface. In the case of an energy conversion device,
reflected electromagnetic radiation would normally be lost and not
available for conversion. In this and other embodiments, other
surfaces in the vicinity of the expander 120 and energy conversion
component 110 are reflective so that electromagnetic radiation
which is not initially captured by the energy conversion component
110 can be reflected and have another chance to intersect the
energy conversion component 110. For example, the interiors of the
covers 156 and 158 may be partly or entirely reflective, either
specularly reflective or diffusely reflective at the
electromagnetic radiation's wavelength. Alternatively, part or all
of the covers 156 and 158 may be covered with energy conversion
components 110, such as photovoltaic cells that are either of the
same type as the main energy conversion components 110, or of a
different type, e.g., thin film photovoltaic cells. These
components (or any sub-section of the components) may be connected
electrically to the main receiver array of components 110, or may
be coupled to a separate electrical output, for example to drive a
fan or cooling pump attached to the receiver 100.
[0037] Still referring to FIG. 1, the conical shape of the expander
120 has a profile (height y as a function of radius r) which is
selected to produce a desired vertical distribution of irradiance
on the energy conversion components 110, such as an approximately
uniform distribution. This profile may depend on the distribution
of the electromagnetic radiation within the beam 132 striking the
expander 120, and the size, orientation, and location of the energy
conversion components 110. While the receiver 100 is not limited to
any particular size, typical dimensions for an energy conversion
component 110 that includes a photovoltaic cell may range from 0.1
cm.sup.2 (e.g., 3 mm.times.3.3 mm) to 100 cm.sup.2 (e.g.,
10.times.10 cm), with the overall radius R between roughly 1 and 10
times the width of a photovoltaic cell.
[0038] The heat sink 154 is exemplary, and may be any desired heat
sink capable of cooling the energy conversion components 110,
including forced-air cooling in a duct or ducts, liquid cooling, or
cooling via heat pipes. Energy conversion devices often require
cooling in order to maintain an appropriate temperature. Flat
energy conversion receivers are limited in the amount of heat sink
area per unit area of receiver because only the axis perpendicular
to the plane of the receiver is available. In some embodiments of
the current invention, the cylindrically symmetric receiver surface
can be coupled to a heat sink that can extend in two dimensions
(when the height of the cylinder is less than its diameter).
[0039] FIGS. 2A-4C illustrate the effect of a conical shape 128 of
an expander 120 on the distribution of irradiance (flux) on the
energy conversion components 110. Each of the conical shapes 128
shown in FIGS. 2A, 3A and 4A are half of the expander's conical
shape; the half of the shape not show is simply a mirror image of
the shape 128 shown about the axis 122 which in these embodiments
also is an axis of symmetry for the expander's conical shape. Also,
in each of the FIGS. 2A, 3A and 4A, the electromagnetic radiation
133 shown approaching the expander 120 is half of the beam that the
whole expander 120 expands.
[0040] FIG. 2A-2C show the effect of reflecting a uniform "top hat"
beam from a uniform cone. Each ring of radius r to r+dr illuminates
an equal area of the energy conversion component 110, so the
irradiance on the array goes to zero for the part illuminated by
the tip 127 of the cone and is highest for the base 125 of the
cone.
[0041] FIGS. 3A-3C show the effect of reflecting a divergent,
centrally-peaked beam (approximating a Gaussian or Airy beam) from
a uniform cone 128. The irradiance still goes to zero for the
energy conversion component area illuminated by the tip 127 of the
cone, but also falls off for the base 125 of the cone, with a
maximum in between.
[0042] FIGS. 4A-4C illustrate an approach to making the array
irradiance more uniform. By making the expander's conical shape 128
out of two or more conical segments 123a and 123b, with a total
height greater than the height of the energy conversion component
110, the vertical distribution of the irradiance on the component
110 can be rearranged. As an example, the irradiance from the upper
conical segment 123b (which decreases with height) can be overlaid
with the irradiance from the lower conical segment 123a. To
minimize the angle of incidence of the light on the energy
conversion component 110, the base 125 of the expander 120 may be
positioned lower than the bottom 131 of the energy conversion
component 110. Depending on the divergence of the input beam 133
and the radius of the receiver 100, the height of the energy
conversion component 110 may be less than, equal to, or greater
than the height of the expander 120.
[0043] Still referring to FIG. 4A, the expander 120 may have three
or more conical segments, allowing greater control over the
irradiance distribution on the energy conversion component 110. In
addition, the conical segments may be made individually convex or
concave, to increase or decrease the height of the illuminated
region.
[0044] In some embodiments, reflective surfaces may be used above
and/or below the energy conversion component 110 to capture
electromagnetic radiation, which would otherwise miss the component
110, and redirect it toward the component 110. These surfaces may
be specular or diffuse reflectors. In some embodiments they may be
used only to capture stray electromagnetic radiation, i.e.,
radiation scattered by outside of the main ray paths, e.g., by
surface roughness on the expander 120. In other embodiments the
main beam 133 path may be deliberately arranged to illuminate areas
above and below the actual energy conversion component 110, and the
reflectors may serve to redirect this light onto the components
110. In some embodiments, this may serve to further improve the
uniformity of the component 110 illumination. In some embodiments,
these reflective surfaces may be part of the top and/or bottom
covers of the receiver housing.
[0045] The height, angles, and (if desired) curvatures of the
individual cone segments can be found by trial and error, or by any
of a variety of optimization techniques known in the art. Such
optimizations may consider constraints on, for example, maximum and
minimum irradiance on the energy conversion components 110, and may
optimize for a variety of properties such as uniformity of
illumination or insensitivity to misalignment of the input beam
133.
[0046] FIGS. 5A-5C illustrate an alternative approach to defining
the profile of the expander 120. In this approach, the profile is
locally curved to increase or decrease the vertical divergence of
the radial beam 137 so that, at the energy conversion component 110
location, the irradiance is uniform (FIG. 5C) over the height of
the component 110. Unlike the conical-segment approach (FIG. 4A),
this approach is capable of producing a precisely-uniform
distribution of irradiance of any desired height, provided the
incident beam 133 profile is known.
[0047] The profile of an ideal curved expander 120 is defined by a
second order differential equation. For a continuous profile and a
continuous distribution of irradiance on the energy conversion
component 110 (and assuming a fixed radial position R for the
component 110, i.e., the component 110 is vertical) a given segment
of the expander's conical shape 128 at (r.sub.e, y.sub.e) reflects
electromagnetic radiation onto a segment of the component 110 at a
height y.sub.ecc=f1(r.sub.e, y.sub.e, y'.sub.e) where
y'.sub.e=dy.sub.e/dr.sub.e). For any particular expander profile,
r.sub.e can be expressed as a function of y.sub.e, or vice versa.
The corresponding irradiance on the component 110 is a function of
the input irradiance 133 striking the expander 120 at r.sub.e, and
the vertical focusing or defocusing of the beam 137 by the expander
120 (corresponding to increasing or decreasing the irradiance at
the component 110). This focusing is a function of the local
curvature of the expander 120, proportional to
y''.sub.e=d.sup.2y.sub.e/dr.sub.e.sup.2, and of the distance
between the point of reflection and the component 110, which
depends on r.sub.e. In general form,
.PHI..sub.pv[f1(r.sub.e,y.sub.e,y'.sub.e)]=.PHI..sub.in(r.sub.e,y.sub.e)-
*f2(r.sub.e,y''.sub.e)
[0048] Straightforward generalizations apply if the component 110
and/or the expander 120 are non-circular (R or r not constant with
angle around the axis 122) or the component 110 is not vertical (R
depends on y.sub.ecc). This can be solved for any given expander
120 profile and input beam 133. However, inverting this to
determine the expander 120 profile for a given input beam 133 and a
desired .PHI..sub.ecc is complex, and must in general be done
numerically.
[0049] Any suitable technique may be used to fabricate the expander
120. For example, the conical-segment expander can be fabricated
using conventional machining and polishing techniques suitable for
flat-sided cylinders and cones. The expander 120 can also be
fabricated in two or more separate pieces, each with a flat or
simply-curved profile, which are then fastened (e.g., glued and/or
screwed) together.
[0050] The arbitrarily-curved expander 120 may be fabricated in a
variety of ways, including separately fabricating and then stacking
multiple disks with appropriate diameters and flat angled or
simply-curved rims. A single-piece expander 120 can also be readily
fabricated using a computer-controlled lathe. The resulting part
may be polished after cutting or it may have adequate surface
quality as-cut.
[0051] An expander 120 may be molded in its entirety, or may be
replicated using a layer of moldable material over a rigid core. A
single piece mold may be used, or a two-piece mold may be used, as
small seams or other imperfections will in general have little
effect on the overall operation of the receiver.
[0052] Referring now to FIGS. 6A-6D, the electromagnetic radiation
from the optical fiber 130 may be coupled onto the expander 120
using a variety of optical configurations. FIG. 6A illustrates an
embodiment using a simple diverging lens 410, which increases the
divergence of the beam 400 from the fiber 405 and thereby shortens
the distance between the fiber 405 and the expander 120 for a given
expander diameter. FIG. 6B illustrates an embodiment using a
collimating lens 420, which decreases the angle of incidence of the
electromagnetic radiation on the base 125 of the expander 120. FIG.
6C illustrates an embodiment using a combination of a collimating
lens 430 and a converging lens 440 which refocuses the
electromagnetic radiation from the fiber, allowing the
electromagnetic radiation to enter the receiver proper through a
small aperture 445. FIG. 6D illustrates an embodiment using an
optical element 450 fused directly to the end of the optical fiber,
eliminating the exposed fiber end and the associated reflection of
electromagnetic radiation back down the fiber, along with the risk
of damage to or contamination of the fiber end. Alternatively,
element 450 may be butt-coupled to the fiber, or coupled via an
index-matching fluid.
[0053] FIG. 7 illustrates an embodiment where the fiber 510 enters
from the bottom of the receiver (100 in FIG. 1), and the beam 515
passes through a hole in the expander [0050] 520. Electromagnetic
radiation is reflected from a shallow conical reflector 550 to
create a hole in the reflected beam, avoiding reflection of
electromagnetic radiation back down the fiber or onto the fiber
end. This also reduces the maximum intensity of electromagnetic
radiation on the expander 520 itself. In other embodiments, the
fiber may enter the receiver at a point other than the center of
the bottom cover, and the reflector 550 may be, for example, a
tilted flat reflector.
[0054] FIGS. 8A-8C illustrate an embodiment in which the beam of
electromagnetic radiation is redistributed radially allowing the
expander 120 to include a conical shape that is a simple
straight-sided cone. Any combination of optical elements and
expander shaping may be used to produce the desired vertical
distribution of flux on the energy conversion component 110. For
example, in some embodiments axicon optical elements 610 and 620
may be used. In other embodiments, lenses, mirrors, optical filters
(wavelength filters or polarizing filters), diffusers, prisms (such
as Risley prisms to steer the beam, or anamorphic prisms to change
the beam diameter or shape), each of which may be fixed and/or
adjustable, may be used.
[0055] Referring now to FIGS. 9A and 9B, in some cases it may be
desirable to transmit or receive a second wavelength of
electromagnetic radiation over the optical fiber, separate from the
first wavelength being received by the energy conversion component,
e.g., for communications or data transmission. In some embodiments,
as shown in FIG. 9A, this second wavelength may be separated from
or combined with the first wavelength by a dichroic reflector 710
incorporated into some part of the beam path. The second wavelength
may be emitted or received by device 720 and focused by
representative optical element 730. In other embodiments, as shown
in FIG. 9B, a portion of the expander itself may be a dichroic
element 740, which at least partly transmits the second wavelength
while reflecting the first wavelength. Other possible optical
configurations for transmitting or receiving a second wavelength
will be apparent to those skilled in the art.
[0056] FIG. 10 illustrates a top view of a non-circular array of
energy conversion components 110 and a corresponding non-circular
expander 120. Such a non-circular array may arise because the array
comprises a small number of rigid cells, or due to other
constraints, for example on the space available for the receiver.
The non-circular expander 120 has a radius which varies as a
function of both height and rotational angle, typically with
greater curvature where the array is closer to the axis, and
smaller curvature where the array is farther from the axis, to
provide a desired flux distribution on the energy conversion
components. Such complex shapes may be fabricated by, for example,
computer-controlled milling.
[0057] FIG. 11 illustrates a receiver using a pyramidal expander
910, which yields a high irradiance over a portion of the receiver
circumference and negligible irradiance elsewhere. Such a
configuration may be used with energy conversion components 930
which are optimized for comparatively high flux, and/or are high
cost. The generally circular or polygonal configuration of the
receiver allows efficient cooling of such components 930, and the
expander profile may still be selected to provide uniform
irradiance of the component array in the vertical direction. The
space between components 930 may be filled with reflective material
920, so that light reflected or scattered from one component 930
will reflect within the receiver until it is absorbed by the same
or another component 930. In some embodiments, components 930 may
be deliberately oriented away from perpendicular to the receiver
axis so that electromagnetic radiation 935 reflected from one
component 930 will strike another component 930, or a wall of the
receiver, rather than striking the expander 910 and being reflected
back toward the optical fiber.
[0058] Combinations of the different expander configurations
discussed above may also be used.
[0059] The preceding discussion is presented to enable a person
skilled in the art to make and use the invention. Various
modifications to the embodiments will be readily apparent to those
skilled in the art, and the generic principles herein may be
applied to other embodiments and applications without departing
from the spirit and scope of the present invention. Thus, the
present invention is not intended to be limited to the embodiments
shown, but is to be accorded the widest scope consistent with the
principles and features disclosed herein.
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