U.S. patent application number 13/717242 was filed with the patent office on 2013-07-04 for light collection apparatus, system and method.
This patent application is currently assigned to THE REGENTS OF THE UNIVERSITY OF CALIFORNIA. The applicant listed for this patent is THE REGENTS OF THE UNIVERSITY OF CALIFORNIA. Invention is credited to Roland Winston, Weiya Zhang.
Application Number | 20130170046 13/717242 |
Document ID | / |
Family ID | 43526761 |
Filed Date | 2013-07-04 |
United States Patent
Application |
20130170046 |
Kind Code |
A1 |
Winston; Roland ; et
al. |
July 4, 2013 |
LIGHT COLLECTION APPARATUS, SYSTEM AND METHOD
Abstract
An optical collector is disclosed which includes an imaging,
aplanatic optical element having a front surface with a one-way
light admitting portion, a back surface with a reflective portion,
and an interior region of refractive material disposed between the
front and backs surfaces.
Inventors: |
Winston; Roland; (Merced,
CA) ; Zhang; Weiya; (Merced, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
THE REGENTS OF THE UNIVERSITY OF CALIFORNIA; |
Oakland |
CA |
US |
|
|
Assignee: |
THE REGENTS OF THE UNIVERSITY OF
CALIFORNIA
Oakland
CA
|
Family ID: |
43526761 |
Appl. No.: |
13/717242 |
Filed: |
December 17, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
12846710 |
Jul 29, 2010 |
8355214 |
|
|
13717242 |
|
|
|
|
61230054 |
Jul 30, 2009 |
|
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Current U.S.
Class: |
359/641 ;
359/839 |
Current CPC
Class: |
G02B 17/006 20130101;
G02B 19/008 20130101; G02B 19/0028 20130101; G02B 19/0042 20130101;
G02B 19/0085 20130101 |
Class at
Publication: |
359/641 ;
359/839 |
International
Class: |
G02B 17/00 20060101
G02B017/00 |
Claims
1. An apparatus for collecting light from a source into a beam of
light, said apparatus comprising: a front surface comprising a
selectively light transmitting portion; a back surface comprising a
reflecting portion; and an internal region disposed between the
front surface and back surface; said selectively light transmitting
portion comprising a side facing the internal region which
selectively reflects light incident from the source back through
the internal region towards the reflecting portion of the back
surface; said reflecting portion of the back surface reflecting the
light from the front surface back through the internal region
towards the front surface; and said selectively light transmitting
portion selectively transmitting at least a portion of light
incident from the reflecting portion of the back surface out of the
internal region to form the beam of light.
2. The apparatus of claim 1, wherein the internal region comprises
a refractive material.
3. The apparatus of claim 2 wherein the refractive material
comprises dielectric material.
4. The apparatus of claim 2, wherein the selectively light
transmitting portion comprises an interface between the refractive
material in the internal region and a material outside the internal
region having a differing index of refraction, and wherein the
light selectively reflected from the selectively light transmitting
portion is reflected due to total internal reflection.
5. The apparatus of claim 4, wherein the material outside the
internal region having a differing index of refraction has an index
of refraction which is less that the index of refraction of the
refractive material in the internal region.
6. The apparatus of claim 5, wherein the material outside the
internal region comprises a fluid having an index of refraction of
about n=1.
7. The apparatus of claim 2, wherein the refractive material in the
internal region comprises a fluid.
8. The apparatus of claim 7, wherein the refractive material
comprises a material selected from the list consisting of: water,
oil, mineral oil.
9. The apparatus of claim 7, further comprising a shell surrounding
the internal region, said shell comprising the front and back
surfaces.
10. The apparatus of claim 7, further comprising a circulator for
circulating the fluid through the internal region.
11. The apparatus of claim 10, wherein the circulator is adapted to
remove heat from the internal region.
12. The apparatus of claim 2, having a focal point located in a
focal plane, and wherein the source is located proximal to the
focal point, and the front and back surfaces are configured to
cooperate to collect light from the source and substantially
collimate the light into the beam.
13. The apparatus of claim 12, wherein the front surface and back
surface are aspherical surfaces adapted to substantially eliminate
spherical and comatic aberration associated with light collected
from the source located proximal to the focal point.
14. The apparatus of claim 13, wherein light rays collected from
the focal point and collimated into the beam substantially satisfy
the Abbe sine condition.
15. The apparatus of claim 2, wherein the reflecting portion of the
back surface comprises a metalized surface portion.
16. The apparatus of claim 2, wherein the front surface comprises a
centrally located reflector comprising a reflective side facing
towards the internal region and a light blocking side facing away
from the internal region; wherein the selectively light
transmitting portion of the front surface substantially surrounds
the centrally located reflector.
17. The apparatus of claim 16, wherein the centrally located
reflector provides a central obscuration of less than about 3%.
18. The apparatus of claim 16, wherein the centrally located
reflector provides a central obscuration of less than about 7%.
19. The apparatus of claim 16, wherein the centrally located
reflector provides a central obscuration of less than about
10%.
20. The apparatus of claim 12, wherein the apparatus is disposed
about an optical axis extending normal to the focal plane, and
wherein light emitted from the source at angles less than 60
degrees from the optical axis are collected into the beam.
21. The apparatus of claim 20, wherein at least 80% of the light
power emitted from the source is collected into the beam.
22. The apparatus of claim 20, wherein at least 70% of the light
power emitted from the source is collected into the beam.
23. The apparatus of claim 12, wherein the apparatus is disposed
about an optical axis extending normal to the focal plane, and
wherein light emitted from the source at angles less than 60
degrees from the optical axis are collected into the beam.
24. The apparatus of claim 12, wherein the apparatus is disposed
about an optical axis extending normal to the focal plane, and
wherein light emitted from the source at angles less than 80
degrees from the optical axis are collected into the beam.
25. The apparatus of claim 1, having an f/number of about 1.0 or
less.
26. A method comprising: providing an apparatus for collecting
light from a source into a beam of light, said apparatus
comprising: a front surface comprising a selectively light
transmitting portion; a back surface comprising a reflecting
portion facing the internal region; and an internal region disposed
between the front surface and back surface, said selectively light
transmitting portion comprising a side facing the internal region;
using the side selectively light transmitting portion facing the
internal region to selectively reflect light incident from the
source back through the internal region towards the reflecting
portion of the back surface; using the reflecting portion of the
back surface to reflect the light from the front surface back
through the internal region towards the front surface; and using
the selectively light transmitting portion to selectively transmit
at least a portion of light incident from the reflecting portion of
the back surface out of the internal region to form the beam of
light.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. application Ser.
No. 12/846,710, filed Jul. 29, 2010, which in turn claims priority
under 35 U.S.C. .sctn.119(e) to U.S. Provisional Application No.
61/230,054, filed Jul. 30, 2009, the entire content of each of
which is hereby incorporated by reference into the present
disclosure.
BACKGROUND
[0002] This disclosure relates to the concentration or collection
of light, and, more particularly, the concentration or collection
of light using an optical element.
[0003] Typically, light concentrators operate to receive light
incident over a range of angles less than an acceptance angle at an
aperture. The light is concentrated onto a region (e.g. on an
absorber) with an area smaller than the area of the aperture. The
ratio of the aperture area to the smaller area is known as the
geometric concentration C. The laws of thermodynamics set a
theoretical upper bound, known in the art as the "thermodynamic
limit," to the concentration for a given concentrator
configuration.
[0004] Many types of solar concentrators have been studied
including reflective and refractive devices. Concentrators may be
imaging or non-imaging, and may be designed to correct for various
types of optical aberration (spherical aberration, coma,
astigmatism, chromatic aberration, etc.). For example, D.
Lyndon-Bell, Monthly Notices of the Royal astronomical Society,
vol. 334, pp. 787-796 (2002), describes an aplanatic concentrator
featuring primary and secondary reflectors. However, the efficiency
of such concentrators is limited by the obscuration of the primary
reflector by the secondary reflector.
[0005] Optical concentrators may be applied, for example, in the
conversion of solar energy to electricity (or other form of
energy). The power that a photovoltaic solar cell can produce is a
function of the incident sunlight. A typical solar cell can utilize
efficiently many times the un-concentrated incident sunlight in
typical settings, provided that the temperature of the solar cell
does not increase excessively. Therefore, an optical concentrator
can be employed to concentrate sunlight onto a photovoltaic cell to
improve the output of the photovoltaic cell. The output will
increase with the concentration factor. At appreciable
concentration factors, cooling may be required, since the
efficiency of some photovoltaic cells may decrease rapidly with
increasing temperatures.
[0006] Optical concentrators may be applied in a variety of other
applications including, for example, imaging, photography,
concentration of light from sources such as lasers or light
emitting diodes (LEDs), etc.
SUMMARY
[0007] The inventors have realized that a multiple surface optical
concentrator may be used to concentrate light. At least one of the
surfaces includes a one-way light admitting portion which
selectively admits light through the surface into the concentrator
while reflecting (e.g. via total internal reflection) light
impinging on the surface from within the concentrator. Such a
concentrator may provide excellent concentration while reducing or
avoiding obscuration of further surfaces by the surface which
includes the one-way light admitting portion. In some embodiments,
the concentrator may be an imaging aplanatic concentrator (i.e.
substantially free of spherical and comatic aberration.) Such
concentrators may be used in numerous applications including the
collection of solar energy.
[0008] The inventors have also realized that an imaging aplanatic
multiple surface optical concentrator of the type described herein
may be designed using a flexible, convenient, and computationally
straightforward iterative method. Any number of techniques may then
be used to manufacture the concentrator based on the design.
[0009] In one aspect, an apparatus for concentrating light from a
source is disclosed including: a front surface including a one-way
light admitting portion; a back surface including a reflecting
portion; and an internal region disposed between the front surface
and back surface. The one-way light admitting portion admits at
least a portion of light incident from the source from outside of
the internal region into the internal region and onto the
reflecting portion of the back surface. The reflecting portion of
the back surface reflects the portion of light back through the
internal region towards the front surface facing the internal
region. The front surface includes a side facing the internal
region which reflects light incident from the back surface and
concentrates the light to a concentration region. At least a
portion of the reflected and concentrated light is reflected from
the one-way light admitting portion of the front surface.
[0010] In some embodiments, the internal region includes a
refractive material. In some embodiments, the refractive material
includes dielectric material.
[0011] In some embodiments, the one-way light admitting portion
includes an interface between the refractive material in the
internal region and a material outside the internal region having a
differing index of refraction, and where the portion of light
reflected from the one-way light admitting portion is reflected due
to total internal reflection.
[0012] In some embodiments, the material outside the internal
region having a differing index of refraction has an index of
refraction which is less that the index of refraction of the
refractive material in the internal region. In some embodiments,
the material outside the internal region includes a fluid having an
index of refraction of about n=1.
[0013] In some embodiments, the refractive material in the internal
region includes a fluid.
[0014] In some embodiments, the refractive material includes a
material selected from the list consisting of: water, oil, mineral
oil. Some embodiments further include a shell surrounding the
internal region, where the shell may include the front and back
surfaces. Some embodiments include a circulator for circulating the
fluid through the internal region. The circulator may be adapted to
remove heat from the internal region. Some embodiments include an
absorber located proximal to the concentration region, and the
circulator may be adapted to remove heat from the absorber. In some
embodiments, the circulator includes a heat exchanger in thermal
communication with the fluid and configured to remove heat from the
fluid. Some embodiments include a heat converter which converts
heat from the fluid to another form of energy.
[0015] In some embodiments, material outside the internal region
includes a fluid, e.g., water, oil, and/or mineral oil. Some
embodiments include a circulator for circulating the fluid outside
the internal region. The circulator may be adapted to remove heat
from the internal region. In some embodiments, the circulator
includes a heat exchanger in thermal communication with the fluid
and configured to remove heat from the fluid.
[0016] In some embodiments, the front surface, back surface, and
internal region are adapted to form an image of the source at the
concentration region. In some embodiments, the front surface and
back surface are aspherical surfaces adapted to substantially
eliminate spherical and comatic aberration of the image of the
source. In some embodiments, light rays forming the image of the
source substantially satisfy the Abbe sine condition.
[0017] In some embodiments, the reflecting portion of the back
surface includes a metalized surface portion.
[0018] In some embodiments, the front surface includes a centrally
located reflector including a reflective side facing towards the
internal region and a light blocking side facing away from the
internal region. The one-way light admitting portion of the front
surface may substantially surround the centrally located reflector.
In some embodiments, the centrally located reflector provides a
central obscuration of less than about 10%, 7%, 3%, or less.
[0019] In some embodiments, light from the source incident on the
front surface at an angle of incidence less than about 2 degrees is
concentrated to the concentration region with an efficiency of
greater than 70%, 80%, 90% or more.
[0020] In some embodiments, light from the source incident on the
front surface at an angle of incidence less than about 2 degrees is
concentrated to the concentration region with a geometrical
concentration ratio of about 500 or greater, 1,000 or greater,
1,200 or greater, 2000 or greater, or even more.
[0021] In some embodiments, light from the source incident on the
front surface at an angle of incidence less than about 1.5 degrees
is concentrated to the concentration region with a geometrical
concentration ratio of about 500 or greater, or 1,000 or greater,
or 2,000 or greater.
[0022] In some embodiments, light from the source incident on the
front surface at an angle of incidence less than about 1 degrees is
concentrated to the concentration region with a geometrical
concentration ratio of about 500 or greater, 1,000 or greater,
2,000 or greater, 3,000 or greater, or 4,000 or greater.
[0023] In some embodiments, the source is imaged at an image plane
in the concentration region, and where the light forming the image
of the source is incident on the image plane at angles less than
about 60 degrees.
[0024] In some embodiments, light from the source incident on the
front surface at an angle of incidence less than about 2 degrees is
concentrated to the concentration region at about the thermodynamic
limit.
[0025] In some embodiments, the dielectric material includes at
least one chosen from the group consisting of: glass, plastic,
quartz, and transparent fluid.
[0026] In some embodiments, the dielectric material has an index of
refraction greater than about 1.3.
[0027] Some embodiments further include the source. In some
embodiments, the source includes at least one chosen from the group
consisting of: a light emitting diode; an organic light emitting
diode, a laser; and a lamp.
[0028] In another aspect, a system is disclosed including: an
optical concentrator of the type described herein; and a light
receiving element located proximal to the concentration region. The
optical concentrator is adapted to concentrate light from the
source onto the energy absorbing element.
[0029] In some embodiments, the light receiving element includes an
energy converting element adapted to absorb light concentrated at
the concentration region and output energy in response to the
absorbed light.
[0030] In some embodiments, the energy converting element outputs
electrical energy in response to the concentrated light.
[0031] In some embodiments, the light receiving element includes a
photovoltaic cell.
[0032] In some embodiments, the energy converting element produces
thermal energy in response to the concentrated light.
[0033] In some embodiments, the light receiving element includes a
photodiode, a laser gain medium, a photographic medium, or a
digital imaging sensor. In some embodiments, the digital imaging
sensor includes at least one selection from the group consisting
of: a CCD, a multi-pixel array of photodetectors, a CMOS detector.
In some embodiments, the light receiving element includes a digital
light processor or a MEMs device.
[0034] In another aspect, an optical imaging system is disclosed
including a plurality of optical elements adapted to image light
from an image plane onto an object plane, the plurality of lenses
including the optical concentrator of the type described herein. In
some embodiments, the plurality of optical elements include a
telephoto lens system.
[0035] In another aspect, a method is disclosed for designing an
imaging, aplanatic optical concentrator including a front surface
with a one-way light admitting portion, a back surface with a
reflective portion, and an interior region of refractive material
disposed therebetween, the method including: determining the shape
of the front and back surfaces by: defining an Abbe sphere with
radius b; defining an initial ray parallel to an optical axis of
the concentrator which is incident upon the front surface at an
initial front surface point located on the Abbe sphere; selecting a
position along the optical axis for an initial back surface point;
determining the surface tangent slope at each of the initial front
surface point and the initial back surface point by requiring that
light from the initial ray refracts at the initial front surface
point, propagates along a propagation path through the interior
region to the initial back surface point, reflects from the initial
back surface point, propagates back along the same propagation path
to the initial front surface point, reflects from the initial front
surface point due to total internal reflection, and propagates to
the center of the Abbe sphere. The method further includes
iteratively determining the position and tangent slopes at
additional front and back surfaces points based on the positions of
and surface tangent slopes at the initial front and back surface
points.
[0036] In some embodiments, determining the shape of the front and
back surfaces includes: determining cross sectional shapes of the
front and back surfaces; and defining the shape of the front and
back surfaces as the rotation of the cross sectional shapes about
the optical axis.
[0037] In some embodiments, the method includes defining a
coordinate system with orthogonal axes Y and Z and intersecting at
point P, where Z corresponds to an optical axis of the
concentrator; defining an Abbe sphere with radius b centered at P;
defining a series of N light rays Ray #i, where i=0, 1, 2, . . .
N-1, the rays traveling parallel to the Z axis to intersect the
front surface of the concentrator, and where A.sub.i is a point
where parallel Ray #i intersects the Abbe sphere; R.sub.i is a
point where parallel Ray #i intersects front surface and refracts;
B.sub.i is a point where Ray #i intersects rear surface and
reflects; X.sub.i is the point where Ray #i intersects front
surface the second time and reflects; kB.sub.i is the slope of the
surface tangent at B.sub.i; and kX.sub.i: is the slope of the
surface tangent at X.sub.i. The method includes selecting an angle
.theta.; requiring that the (Y,Z) coordinates of R.sub.0 be (b
cos(.theta.), b sin(.theta.)) such that R.sub.0 lies in the Abbe
sphere and A.sub.0 and X.sub.0 coincide with R.sub.0; selecting the
Z coordinate of B.sub.0; determining kX.sub.0 based on the relation
kX.sub.0=tan(.alpha.)=((n.sub.0/n.sub.1)+cos(.theta.))/sin(.theta.),
where n.sub.0 is the index of refraction of a media surrounding the
concentrator and n.sub.1 is the index of refraction of the
refractive material; determining kB.sub.0 based on the relation
kB.sub.0=(c tan(2 .alpha.)c tan(.theta.)-1)/(c tan(.theta.)+c tan(2
.alpha.)); constructing the front and back surfaces by iteratively
determining X.sub.i and B.sub.i for i=1, 2, . . . , N-1. The
iterative determination includes the steps of: determining
X.sub.i+1 by extending the front surface along kX.sub.i direction
for a small step; determining A.sub.i+1 as the intersection of the
line from point P to point X.sub.i+1 with the Abbe sphere;
determining R.sub.i+1 as the intersection of Ray #(i+1) passing
through the Abbe sphere at A.sub.i+1 with the front surface;
determining the path of propagation of light from Ray #(i+1) from
point R.sub.i+1 through the interior region to the back surface;
determining B.sub.i+1 by intersecting the path of propagation of
light from Ray #(i+1) from point R.sub.i+1 with a line extending
along the kB.sub.n direction; determining kB.sub.n+i such that the
ray of light from R.sub.i+1 to B.sub.i+1 reflects at B.sub.i+1 back
towards X.sub.n+1; determining kX.sub.i+1 such that the ray of
light from B.sub.i+1 to X.sub.i+1 reflects at X.sub.i+1 towards
P.
[0038] Some embodiments include, for each point on the front
surface, providing reflective material on the side of the front
surface facing the interior region if the ray of light reflected
from the back surface through the interior region onto the point
does not meet the condition for total internal reflection.
[0039] In another aspect, an optical concentrator is disclosed
including: an imaging, aplanatic optical element including a front
surface with a one-way light admitting portion, a back surface with
a reflective portion, and an internal region of refractive material
disposed between the front and backs surfaces. In some embodiments,
the one way light admitting portion selectively admits light
incident from outside the internal region while reflecting light
incident from the internal region. In some embodiments, the one way
light admitting portion reflects light incident from the internal
region by total internal reflection.
[0040] In some embodiments, the optical element has an acceptance
angle of about 2 degrees or greater. In some embodiments, the
optical element concentrates light incident at less than the
acceptance angle with a concentration ratio of about 1000 or
greater. In some embodiments, the optical element concentrates
light incident at less than the acceptance angle with an efficiency
of about 70% or greater. In some embodiments, the optical element
concentrates light at about the thermodynamic limit.
[0041] In some embodiments, the internal region includes a
refractive fluid. Some embodiments include a circulator configured
to circulate the refractive fluid. In some embodiments, the optical
element includes a shell defining the internal region, the shell
including the front and back surfaces.
[0042] In another aspect, a method of concentrating light from a
source is disclosed including: providing a concentrator of the type
disclosed herein; directing light from the source to the
concentrator; and using the concentrator, concentrating light in
the concentration region. Some embodiments include providing an
absorber at the concentration region; and using the absorber,
absorbing optical energy from the source. Some embodiments include
converting absorbed optical energy into another form of energy.
[0043] In another aspect, an apparatus for collecting light from a
source into a beam of light, the apparatus including: a front
surface including a selective light transmitting portion; a back
surface including a reflecting portion; and an internal region
disposed between the front surface and back surface. The
selectively light transmitting portion includes a side facing the
internal region which selectively reflects light incident from the
source back through the internal region towards the reflecting
portion of the back surface. The reflecting portion of the back
surface reflects the light from the front surface back through the
internal region towards the front surface. The selectively light
transmitting portion selectively transmitting at least a portion of
light incident from the reflecting portion of the back surface out
of the internal region to form the beam of light.
[0044] In some embodiments, the internal region includes a
refractive material. In some embodiments, the refractive material
includes dielectric material.
[0045] In some embodiments, the selectively light transmitting
portion includes an interface between the refractive material in
the internal region and a material outside the internal region
having a differing index of refraction, and where the light
selectively reflected from the selectively light transmitting
portion is reflected due to total internal reflection. In some
embodiments, the material outside the internal region having a
differing index of refraction has an index of refraction which is
less that the index of refraction of the refractive material in the
internal region. In some embodiments, the material outside the
internal region includes a fluid having an index of refraction of
about n=1.
[0046] In some embodiments, the refractive material in the internal
region includes a fluid. In some embodiments, the refractive
material includes a material selected from the list consisting of:
water, oil, mineral oil. Some embodiments include a shell
surrounding the internal region, the shell including the front and
back surfaces. Some embodiments include a circulator for
circulating the fluid through the internal region. In some
embodiments, the circulator is adapted to remove heat from the
internal region.
[0047] In some embodiments, the device includes a focal point
located in a focal plane. The source is located proximal to the
focal point, and the front and back surfaces are configured to
cooperate to collect light from the source and substantially
collimate the light into the beam.
[0048] In some embodiments, the front surface and back surface are
aspherical surfaces adapted to substantially eliminate spherical
and comatic aberration associated with light collected from the
source located proximal to the focal point.
[0049] In some embodiments, light rays collected from the focal
point and collimated into the beam substantially satisfy the Abbe
sine condition.
[0050] In some embodiments, the reflecting portion of the back
surface includes a metalized surface portion.
[0051] In some embodiments, the front surface includes a centrally
located reflector including a reflective side facing towards the
internal region and a light blocking side facing away from the
internal region. The selectively light transmitting portion of the
front surface substantially surrounds the centrally located
reflector. In some embodiments, the centrally located reflector
provides a central obscuration of less than about 3%, or less than
about 7%, or less than about 10%.
[0052] In some embodiments, the apparatus is disposed about an
optical axis extending normal to the focal plane, and where light
emitted from the source at angles less than 60 degrees from the
optical axis, less than 70 degrees, less than 80, degrees, less
than 90 degrees, etc. are collected into the beam. In some
embodiments, at least 70%, at least 80%, or at least 90% or more of
the light energy or power emitted from the source is collected into
the beam.
[0053] Some embodiments include the source. In some embodiments,
the source includes at least one chosen from the group consisting
of: a light emitting diode; an organic light emitting diode, a
laser; a lamp.
[0054] In another aspect, a method is disclosed including:
providing an apparatus for collecting light from a source into a
beam of light, the apparatus including: a front surface including a
selectively light transmitting portion, a back surface including a
reflecting portion facing the internal region; and an internal
region disposed between the front surface and back surface, the
selectively light transmitting portion including a side facing the
internal region. The method further includes using the side
selectively light transmitting portion facing the internal region
to selectively reflect light incident from the source back through
the internal region towards the reflecting portion of the back
surface; using the reflecting portion of the back surface to
reflect the light from the front surface back through the internal
region towards the front surface; and using the selectively light
transmitting portion to selectively transmit at least a portion of
light incident from the reflecting portion of the back surface out
of the internal region to form the beam of light.
[0055] Some embodiments include directing the beam to illuminate a
target. In some embodiments, the source includes at least one
chosen from the group consisting of: a light emitting diode; an
organic light emitting diode; a laser; a lamp.
[0056] In various embodiments, the concentrators and collectors
described herein may be fast concentrators, e.g. having an f/number
of 1.5 or less, 1 or less, 0.5 or less, 0.4 or less, or even
faster. As used herein, the f/number of an optical element is
defined as one half times the inverse of the numerical aperture NA
of the element. For an optical element having an acceptance angle
.theta., and working in a media having an index of refraction n,
the numerical aperture is given by NA=n sin .theta..
[0057] Various embodiments may include any of the above described
features, either alone, or in combination.
BRIEF DESCRIPTION OF THE DRAWINGS
[0058] FIG. 1A shows a perspective view of a concentrator.
[0059] FIG. 1B shows a cross section of the concentrator of FIG.
1A.
[0060] FIG. 2 is a ray trace diagram of the concentrator of FIG.
1A.
[0061] FIG. 2A is a ray trace diagram of a concentrator showing
axial and off-axial rays.
[0062] FIG. 2B is a perspective view of the concentrator shown in
FIG. 2A.
[0063] FIG. 3A shows a two reflector concentrator of the type known
in the art.
[0064] FIG. 3B shows a cross section of the concentrator of FIG.
1A.
[0065] FIG. 4 shows exemplary parameters for the concentrator of
FIG. 1B.
[0066] FIG. 5 shows a plot of efficiency vs. incident angle for a
concentrator.
[0067] FIG. 6 shows plots of intensity vs radial angle for a
concentrator.
[0068] FIG. 7 shows exemplary performance parameters for
concentrators having various design parameters.
[0069] FIG. 8 shows a concentrator featuring a fluid filled
internal region and circulation system.
[0070] FIG. 9 shows a system featuring a concentrator with an
absorber.
[0071] FIG. 10 shows a system featuring a light source and a
concentrator.
[0072] FIG. 11 shows an optical system featuring a
concentrator.
[0073] FIG. 12 shows a solar panel featuring a concentrator.
[0074] FIG. 13 shows solar energy collection system featuring a
concentrator.
[0075] FIG. 14 is a flowchart illustrating steps for designing a
concentrator.
[0076] FIG. 15 is a graphical ray illustration of the steps of FIG.
14.
[0077] FIG. 16 is an illuminator featuring a concentrator used in a
light collection configuration.
DETAILED DESCRIPTION
[0078] FIG. 1A shows a perspective view of concentrator 100. FIG.
1B shows a cross section of concentrator 100 taken along diameter
AA. Concentrator 100 includes front surface 102 and back surface
104 positioned along optical axis Z. Surfaces 102 and 104 define an
internal region 106 containing a refractive material with index of
refraction n.
[0079] Front surface 102 includes one way light admitting portion
108, described in greater detail below. Front surface 102 may
optionally include central reflector portion 110. Central reflector
portion 110 is opaque to light impinging from outside of internal
region 106 and reflective to light impinging from within internal
region 106. For example, central reflector portion 110 may be a
metalized mirror coating on front surface 102.
[0080] Back surface 104 is reflective (e.g. having a metallized
mirror coating). Light passing through front surface 102 and
internal region 106 onto back surface 104 is reflected back towards
front surface 102.
[0081] Concentrator 100 operates to concentrate light incident on
front surface 102 to concentration region 112 located along optical
axis Z at or near back surface 104. An absorber 114 (e.g. a
photovoltaic cell) may optionally be positioned at or near
concentration region 112 to absorb concentrated light. Concentrator
100 may optionally include cover glass 116.
[0082] FIG. 1B shows a number of suitable exemplary dimensions for
concentrator 100. As shown, concentrator 100 has an outer diameter
of 34.4 mm. The minimum distance between front surface 102 and back
surface 104 along optical axis Z is 6 mm while the maximum distance
between the surfaces is 10 mm. Central reflecting portion 110
extends 5.5 mm radially from optical axis Z. It is to be understood
that the above dimensions are exemplary in nature, and that any
suitable dimensions may be used.
[0083] FIG. 2 is a ray trace diagram of concentrator 100 showing
the propagation of parallel rays 200 through the concentrator. A
first group of rays 200 propagate through collector 100 and are
reflected from the interior side of front surface 102 by total
internal reflection (TIR) from one-way light admitting portion 108.
For example, ray 200A is incident on front surface 102 at a point
within one-way light admitting portion 108. One-way light admitting
portion 108 is transparent to light incident from outside of
internal region 106. Accordingly, ray 200A passes through front
surface 102. At front surface 102, ray 200A is refracted by the
refractive material within internal region 106 and directed towards
a point on back surface 104. Ray 200A is reflected from back
surface 104 towards front surface 102 and towards optical axis Z.
Ray 200A impinges point 202 on the interior side of front surface
102. The shapes of surfaces 102 and the refractive properties of
the material in internal region 106 are chosen to ensure that ray
200A meets the condition for TIR at point 202. Accordingly, ray
200A reflects from point 200 and is directed back towards
concentration region 112 located at or near back surface 104 near
optical axis Z.
[0084] A second group of rays 200 propagate through collector 100
and are reflected from the interior side of front surface 102 by
reflector portion 110 instead of by TIR from one-way light
admitting portion 108. For example, ray 200B is incident on front
surface 102 at a point within one-way light admitting portion 108.
Ray 200B passes through front surface 102, is refracted by the
refractive material within internal region 106 and directed towards
a point on back surface 104. Ray 200B is reflected from back
surface 104 towards front surface 102 and towards optical axis Z.
Ray 200A impinges point 204 on the interior side of front surface
102 within central reflector portion 110. Central reflector portion
110 includes a reflective surface (e.g. a metalized mirror surface)
on the interior side of front surface 102 which reflects ray 200B
back towards concentration region 112 located at or near back
surface 104 near optical axis Z.
[0085] A third group of rays, for example ray 200C, are incident on
front surface 102 within central reflector portion 110. Such rays
are blocked by central reflector portion 110, creating central
obscuration 206. Note however, that central obscuration 206 is
small compared to the remainder of front surface 102, such that the
vast majority of light incident on surface 102 passes into the
concentrator to be concentrated to region 112. For example, in some
embodiments the central obscuration may be about 3% or less.
[0086] As shown, concentrator 100 provides aplanatic imaging.
Concentrator 100 forms an image of a light source at region 112
which is free from comatic aberration. In other words, concentrator
100 obeys the well known Abbe sine condition. For example, for a
source located at "infinity", the sine condition requires that each
ray incident from the source in the direction parallel to the
optical axis of the concentrator intersects its conjugate ray on a
sphere having a radius equal to the focal length of the
concentrator and centered at the focal point (referred to as the
"Abbe sphere").
[0087] FIG. 2A shows a ray trace of diagram of the propagation of
parallel rays 200 and off-axial rays 200D through the concentrator
100. Off axial rays 200D are incident at on concentrator 100 at an
angle of 2 degrees from parallel with the optical axis. As shown,
the rays that would have hit the central obscuration 206 are
blocked by a screen for illustration purpose. Also shown in inset
is a close-up on the concentration region 116, where sharp focusing
of both on-axial and off-axial rays indicates the aplanatic nature
of the design.
[0088] As shown in FIG. 2A, concentrator 100 has an angular
aperture of 60 degrees (0=60 degree), indicative of a very fast
system. The sharp focusing of both on-axial and off-axial (2
degree) rays indicates the aplanatic nature of the design. The
central reflector portion 110 is coated with reflective material,
but the obscuration of the input light is only less than 4%. In
other words, most area of the front surface acts as a "one-way"
mirror, as described above. In the embodiment shown, the aspect
(height:diameter) of this aplanat is approximately 1:3.
[0089] FIG. 2B is a perspective view of the concentrator shown in
FIG. 2A
[0090] FIG. 3A shows a prior art two surface imaging aplanatic
concentrator 300 of the type described in D. Lyndon-Bell, Monthly
Notices of the royal astronomical society, vol. 334, pp. 787-796
(2002). Concentrator 300 includes primary reflector and secondary
reflector 304. Light incident on primary reflector 302 through
opening 306 is reflected back onto secondary reflector 304 and
concentrated at region 308. The concentration obtained by
concentrator 300 tends to increase with an increase in size of
secondary reflector 304. However, secondary reflector 304 acts to
obscure primary reflector 302 (i.e. by reducing the size of opening
306). Thus, increasing the size of secondary reflector 304 results
in an unavoidable trade off between (unwanted) central obscuration
and (desired) concentration.
[0091] Referring to FIG. 3B, concentrator 100 does not suffer from
the above described trade off. Substantially all of the interior
side of front surface 102 is available to reflect light incident
from back surface 104 (either from central reflection portion 110
or one-way light admitting portion 108). However, as noted above,
because one-way light admitting portion 108 is transparent to light
impinging on the outer-facing side of front surface 102, collector
100 suffers only from a small central obscuration 206 caused by
central reflector portion 110. Accordingly, collector 100 provides
good performance and flexibility of design.
[0092] FIG. 4 shows exemplary parameters for a concentrator of the
time shown in FIG. 1B with a concentrator diameter of about 34 mm,
thickness of about 10 mm, and index of refraction n of about 1.52.
Such concentrator may provide geometrical concentration C=1,200 or
greater, near the thermodynamic limit. The optical efficiency may
be 87% or greater with no cover glass, and 79% or greater with a
cover glass. In this example, the reflectivity of back surface 102
is about 95%, and the central obscuration 206 about 3%.
[0093] The acceptance angle of the concentrator may be +/-2 degrees
or greater. For example, FIG. 5 shows an exemplary plot of optical
efficiency vs. incident angle for concentrator 100 with no cover
glass. As shown, optical efficiency may be high and nearly constant
for acceptance angles of +/-2 degrees or more.
[0094] Still referring to the example of FIG. 4, absorber 114 was a
photovoltaic cell with a radius of about 1 mm. In typical
applications, such a cell can only effectively convert light
incident at an angle less than a maximum cell acceptance angle. In
the current example, concentrator 100 concentrates, substantially,
light on the cell at angles of incidence less than about 60
degrees. For example, FIG. 6 shows exemplary plots 600A and 600B of
the intensity of encircled energy incident on the cell vs. the
radial angle (i.e. angle of incidence). Plot 600A refers to source
light striking concentrator 100 at normal incidence while plot 600B
refers to source light striking concentrator 100 at 2 degrees off
axis. As indicated by the sharp inflection points 602A and 602B in
plots 600A and 600B, substantially all of the light striking the
cell may do so at angles less than 60 degrees.
[0095] Although specific exemplary parameters are given above, it
is to be understood that other configurations may be used and even
tailored to a particular application. For example, FIG. 7 shows
exemplary performance characteristics for a variety of possible
configurations of concentrator 100, each having index of refraction
n of about 1.52. For example, for a concentrator with an acceptance
angle of about +/-1 degree, a geometrical concentration C up to
about 4,100 or greater may be provided. For a concentrator with an
acceptance angle of about +/-1.5 degrees, a geometrical
concentration C up to about 2,048 or greater may be provided. For a
concentrator with an acceptance angle of about +/-2 degrees, a
geometrical concentration C up to about 1,200 or greater may be
provided. For a concentrator with an acceptance angle of about
+/-2.5 degrees, a geometrical concentration C up to about 770 or
greater may be provided. Note, in each case the available
concentration compares favorably with the theoretical maximum.
[0096] If one considers the image generated by concentrator 100 as
pixels at the focal plane, an important property is the amount of
light on each pixel. This is called the speed of the optical system
and is related to the angular cone of light on the pixel; the
larger the angle, the faster the system. In various embodiments,
the concentrators described herein may be highly compact and fast
aplanatic singlets. In some embodiments, the f/number (defined as
the ratio of the focal length of the concentrator divided by the
diameter of the entrance pupil) is approximately 1, 0.5, 0.4 or
less, while the aspect (height:diameter) of this aplanat is
approximately 1:1, 1:2, 1:3 or even less.
[0097] In various embodiments, concentrator 100 may be constructed
of any suitable materials. For example, concentrator 100 may be
formed from refractive material such as glass, plastic, quartz,
etc. The material may include any suitable type of material
including dielectrics, semiconductors, non linear optical (NLO)
materials, active gain media, graded index of refraction (GRIN)
materials, photonic crystals, nano-structured materials, etc.
[0098] Referring to FIG. 8, in some embodiments, concentrator 100
may include a shell 801 formed from surfaces 102 and 104. Internal
region 106 is at least partially filled with a refractive fluid 800
(indicated with wavy lines). The fluid may be, for example, a
liquid (e.g. water or mineral oil), gas, gel, or a mixture thereof.
Shell 801 may be formed of any suitable material, e.g. plastic,
glass, quartz, etc. In some embodiments, the fluid 800 may have an
index of refraction which is substantially the same as that of
shell 801. In other embodiments, the indices of refraction may
differ.
[0099] Fluid 800 may be circulated (as indicated by broad arrows)
through internal region 106 using pump 802. This circulation may
operate to remove unwanted heat generated by the concentration of
light onto absorber 114. Fluid 800 may also flow through heat
exchanger 804 for cooling. In various embodiments, heat exchanger
804 may convert heat energy from fluid 800 into other forms of
energy, e.g. electricity, using any suitable technique. Pump 802
and heat exchanger 804 may communicate with one or more sensors
(not shown) either internal to or external from concentrator 100 in
order to maintain the temperature of the concentrator within an
acceptable temperature range (e.g. the preferred operating range of
absorber 114). Note that although a closed circulation system is
shown, other suitable types of fluid flow systems may be used.
[0100] In some embodiments, concentrator 100 may be situated in an
external fluid medium. This medium may be circulated using
techniques similar to those described above to remove heat from
concentrator 100 or parts thereof. In various embodiments, this
heat may be converted to other types of energy using any suitable
technique.
[0101] Referring to FIG. 9, concentrator 100 concentrates light
from a source (not shown) onto absorber 114. Absorber 114 converts
energy from the incident light into another form, and transmits
this energy to module 900. Module 900 may, e.g., store the energy,
use the energy to perform a function, further convert the energy,
and/or transmit the energy to another location. For example, as
noted above, absorber 114 may be a photovoltaic cell which converts
solar energy to electrical energy (i.e. by producing a current or
voltage). In some embodiments, the photovoltaic cell may be a high
efficiency multi junction cell.
[0102] However, absorber 114 may take any suitable form including,
for example: a photo cell, a photodetector, photodiode, a charge
coupled device, a multi-pixel array of photodetectors, a CMOS
detector, a scintillator, a digital camera, a digital light
projector, a recording media such as photographic film, a
photo-sensitive chemical, a thermocouple, a heatable thermal mass,
a MEMs device, a laser gain media, etc.
[0103] Note that although FIG. 9 graphically represents the link
between absorber 114 and module 900 with a wire, any suitable link
may be used. For example, energy may be transmitted wirelessly from
absorber 114 to module 900 in the form of inductive coupling, a
laser or other light beam, RF energy, microwave energy, etc. The
link may be a direct physical link. For example, absorber 114 may
convert light energy to heat to boil water and transmit energy to
module 900 via a steam pipe system or similar techniques.
[0104] In some embodiments, the shape of the distribution of light
concentrated by concentrator 100 may fail to match the shape of the
operating surface of absorber 114. For example, absorber 114 may be
a square shaped photocell while concentrator 100 may concentrate
solar light to a circular spot, leading to inefficiency in
absorption/conversion of solar energy. To correct such mismatch, in
some embodiments one or more optical elements may be used to adjust
the distribution of concentrated light produced by concentrator 100
at absorber 114.
[0105] Referring to FIG. 10, concentrator 100 concentrates light
from source 902 to region 100 onto absorber 114 located on or near
concentration region 112. For example, source 902 may be a light
emitting diode and absorber 114 a diode pumped laser gain medium.
In such a case, concentrator 100 may operate to concentrate light
from the light emitting diode onto the gain medium to achieve
efficient pumping of the laser. As will be understood by those
skilled in the art, any of a variety of light sources may benefit
from concentration of output light by concentrator 100. Such
sources include: light emitting diodes, organic light emitting
diodes, lasers (e.g. diode lasers), lamps (incandescent,
fluorescent, etc.), fluorescent or phosphorescent materials,
amplified stimulated emission sources, etc.
[0106] In various embodiments, concentrator 100 may be included in
an optical system with one or more other optical elements
(refractive, reflective, or otherwise). For example, FIG. 11 shows
a telephoto lens 1100 which includes an aperture 1102, telephoto
lens group and concentrator 100 arranged along an optical axis. In
various embodiments lens 1100 may include additional optical
elements, aperture stops, and so forth (not shown). Concentrator
100 may operate to image and concentrate light from lens group 1104
onto photographic media 1106. Such concentration may provide for
very fast exposure photographic media 1106. Concentrator 100 may
similarly be employed in any number of other optical applications
including, for example, microscopy, photolithography, telescopes
(e.g. for astronomical observation, etc.)
[0107] Referring to FIG. 12, in one embodiment, solar panel 1200
includes an array 1202 of concentrators 100 of the type described
herein. Each concentrator 100 concentrates sunlight onto an
absorber 114 (e.g. a photovoltaic cell or thermal cell) which in
turn converts the concentrated solar energy into another form (e.g.
electrical or thermal energy). Panel 1200 may include one or more
connections between absorbers 114 for collecting the converted
energy and directing it to output 1204. Note that although, as
shown, panel 1200 features a flat regular, two dimensional array of
collectors 100, in various embodiments other configurations may be
used, including, for example one or three dimensional arrays,
irregular patterns in any number of dimensions, curved arrays,
etc.
[0108] Referring to FIG. 13, in one embodiment, solar energy
collector 1300 moves solar panel 1200 to track the movement of the
sun 1301 across the sky in order to maximize the energy obtained
(e.g. by maximizing the light incident on collectors 100 at angles
less than the associated acceptance angle). Controller 1302
controls motorized mount 1304 to move panel 1200 along one or more
degrees of freedom. Controller 1302 may monitor the output of panel
1200, thereby providing a feedback mechanism for positioning the
panel. Of course it is to be understood that a similar collector
system could be employed to track other (non-solar) light
sources.
[0109] The above described devices and systems may be designed and
manufactured using any suitable technique known in the art. The
following describes exemplary convenient methods for concentrator
design and construction.
[0110] In general, an imaging, aplanatic (i.e. substantially
obeying the Abbe sine condition) may be easily designed using a
"seed ray" approach. An Abbe sphere is defined for the concentrator
along an optical axis. A seed ray parallel to the optical axis is
defined which intersects the front surface of the concentrator on
the Abbe sphere. The seed ray refracts from the front surface,
propagates to the back surface, where it is required to
retroreflect back along its path towards the front surface. The
retroreflector ray strikes the front surface again at the same
point on the Abbe sphere and is reflected by TIR (or another
process) and directed towards the center of the Abbe sphere. Based
on the above conditions, and on the index of refraction of the
concentrator and the media in which it is situated, the positions
and surface tangents of points on the front and back surfaces may
be obtained. This information may then be utilized to iteratively
determine the total shapes of the front and back surfaces.
[0111] For example, Referring to FIG. 14, process 1400 may be used
to determine the shapes of front and back surfaces 102 and 104 of
an imaging, aplanatic embodiment of concentrator 100. In the
interest of clarity, FIG. 15 provides an exemplary graphical
representation of process 1400. Initially, assume that the
concentrator lies along an optical axis Z, and is composed of a
material with index of refraction n.sub.1 and is situated in a
medium (e.g. air) having index of refraction n.sub.0. As explained
in detail below, process 1400 traces a number of rays parallel to
the optical axis and incident on concentrator 100 to iteratively
determine the shapes of front surface 102 and back surface 104 of
concentrator 100 (as they lie in a Y-Z plane arranged along a
diameter of the concentrator). In the following discussion, define
the variables below, where the index i runs over 0, 1, 2, 3 . . . ,
N. The upper limit N may be chosen based on design requirements
(i.e. a larger N will provide a finer design surface output, but
will make the iterative process more computationally
expensive).
[0112] P: the center of an Abbe Sphere of radius b, also is the
origin of the Y-Z coordinate system shown in FIG. 15;
[0113] A.sub.i: the point where parallel Ray #i intersects the Abbe
sphere;
[0114] R.sub.i: the point where parallel Ray #i intersects front
surface and refracts;
[0115] B.sub.i: the point where Ray #i intersects rear surface and
reflects;
[0116] X.sub.i: the point where Ray #i intersects front surface 102
the second time and reflects (by TIR or mirror);
[0117] kB.sub.i: the slope of the surface tangent at B.sub.i;
[0118] kX.sub.i: the slope of the surface tangent at X.sub.i.
[0119] In step 1402 of process 1400, define an Abbe sphere of
radius b equal to the focal length of the concentrator. The Abbe
sphere is centered at the focal point of the concentrator. In step
1404 define a parallel "seed" ray (Ray #0).
[0120] In step 1406 intersect the seed Ray #0 with the front
surface at point A.sub.0 on the Abbe sphere. As shown in FIG. 15,
this may be accomplished by choosing an angle .theta. and letting
the (Y,Z) coordinates of point R.sub.0, where seed Ray #0
intersects front surface 102 and refracts, be (-b cos(.theta.), b
sin(.theta.)), such that R.sub.0 lies in the Abbe sphere. Then
A.sub.0 and X.sub.0 must necessarily coincide with R.sub.0.
[0121] In step 1408, choose the Z position along the optical axis
by choosing the Z coordinate Z.sub.2 of B.sub.0. In step 1410,
propagate Ray #0 (i.e., based on Snell's law and the principals of
ray optics) from A.sub.0 to intersect with the back surface. In
step 1412, determine the Y coordinate of point B.sub.0 where Ray #)
intersects rear surface and reflects. In step 1414, require that
the seed ray retroreflects from the back surface towards the front
surface. In step 1416, determine kB.sub.0, the slope of the surface
tangent at B.sub.0. For example, in terms of the angles shown in
FIG. 15, kB.sub.0=tan(.beta.)=(c tan(2 .alpha.)c tan(.theta.)-1)/(c
tan(.theta.)+c tan(2 .alpha.)).
[0122] In step 1418, propagate the seed ray back to the front
surface and, in step 1420, require total internal reflection of the
seed ray from the front surface toward P the center of the Abbe
sphere. Based on this requirement, in step 1422 determine X.sub.0
the slope of the surface tangent at X.sub.0. For example, in terms
of the angles shown in FIG. 15,
kX.sub.0=tan(.alpha.)=((n.sub.0/n.sub.1)+cos(.theta.))/sin(.theta.).
[0123] In step 1424, based on X.sub.0, B.sub.0, and kX.sub.0,
kB.sub.0, extend the front and back surfaces at points X.sub.0,
B.sub.0 a small distance along the surface tangents. In step 1426,
propagate N additional parallel rays to iteratively determine the
complete shapes of the front and back surface. For example, in a
first iteration:
[0124] a. Determine X.sub.n+1 by extending the front surface along
kX.sub.n direction for a small step;
[0125] b. Determine An.sub.+1 by intersecting line PX.sub.n+1 with
the Abbe sphere;
[0126] c. Determine R.sub.n+1 by interesting Ray #(n+1) with the
front surface;
[0127] d. Using Snell Law to determine Ray R.sub.n+1B.sub.n+1;
[0128] e. Determine B.sub.n+1 by intersecting Ray
R.sub.n+1B.sub.n+1 with the extension of the rear surface along the
kB.sub.n direction;
[0129] f. Determine B.sub.n+1 such that Ray R.sub.n+1B.sub.n+1
reflects back towards X.sub.n+1;
[0130] g. Determine kX.sub.n+1 such that Ray B.sub.n+1X.sub.n+1
reflects towards P;
[0131] These steps may then be repeated until the whole surfaces
are constructed. Once the complete surfaces are determines in the
Y-Z plane, they may be rotated about the optical Z axis to provide
a complete three dimensional shape for the concentrator.
[0132] Note that the above process provides a number of free
parameters (e.g., b, .theta., Z.sub.2). This provides a great deal
of flexibility in choice of design parameters. Further, the process
is straightforward and not computationally intensive. For example,
Table 1 contains a simple exemplary script for implementing a
process of the type described above in the well known Scilab
scientific computing environment (available at
"http://www.scilab.org").
TABLE-US-00001 TABLE 1 Exemplary Script
//***********************************************************
************************************************************
************************ //******** This program is to construct a
TIR aplanatic CPV according to the algorithm developed by UCM
group. //******** The construction is simply on a 2D surface (XY
plane) due to rotational symmetry. //******** The convention used
in the codes for the two constructed surfaces are as following:
//******** (Xc3, Rc3) and kc3 are the XY coordinates and the slope
of the front surface (corrector), respectively; //******** (Xp3,
Rp3) and kp3 are the XY coordinates and the slope of the back
surface (primary mirror), respectively. //******** Users can assign
values to the following two free parameters: //******** (1) u:
initial separation of the front and back surface along the X
direction; //******** (2) phim: maximum acceptance angle that the
cell can take. //******** The resolution of the built surfaces is
controlled by NumProfile (default is 1000), which specifies how
dense the surfaces would be sampled. //******** The result is
plotted as a graph by default (pfile=0), user can choose to also
output the results to a txt file by letting pfile=1. //********
------------------------------------------------------
----------------------------------------------------------------- -
//***********************************************************
************************************************************
************************ // Display mode mode(0); // Display
warning for floating point exception ieee(1); //****** define
functions ********* //given two lines (y-y1)=k1*(x-x1),
(y-y2)=k2*(x-x2), return the cross point of the two lines (x3,y3)
function [x3,y3]=linecross(x1,y1,k1,x2,y2,k2)
x3=-(-y2+y1+k2*x2-k1*x1)/(k1-k2);
y3=-(k1*(k2*x2-y2)+k2*y1-k1*k2*x1)/(k1-k2); endfunction //given two
points (x1,y1),(x2,y2), return slope k of the line that connects
the two points function [k]=slope2p(x1,y1,x2,y2) k=(y2-y1)/(x2-x1);
endfunction //given two points (x1,y1),(x2,y2), return the slope k
of the line perpendicular to the line that connects the two points
function [k]=nslope2p(x1,y1,x2,y2) k=-(x2-x1)/(y2-y1); endfunction
//given the slope k1,k2 of two rays, return the slope km of a
mirror that reflects one ray to the other function
[km]=mirrorslope10(k1,k2) alfa1=atan(k1); alfa2=atan(k2);
bia=alfa2-alfa1; km=tan(alfa1+bia/2+%pi/2); endfunction //*******
end of define functions ******** // *** program control variables
***// pfile=0; //weather to print the results to a txt file. 0:no,
1:yes NumProfile = 1000; //how many points on the constructed
surfaces // *** end of control variables ***// // *****constants
******** n0=1; //refractive index of air n1=1.5249; //refractive
index of Schott BK270 at 550 nm b=1; // radius of Abbe sphere //
***** end of constants ***** // ****** free parameters *******
u=b*0.0065; // u: initial separation of the front and back surface
along the X direction phim=61/180*%pi; // maximum acceptance angle
v=b*cos(phim); // v: front surface initial displacement along X
direction // ***** end of free parameters ****** //***** increment
of each step in y direction *****// phiMin=1e-20; phiMax=phim;
SinPhiMin=sin(phiMin);SinPhiMax=sin(phiMax);
SinPhiStep=(SinPhiMax-SinPhiMin)/NumProfile; // *** the starting
points and the initial slope of both surfaces
ka=(n0/n1+cos(phim))/sin(phim); alfa=atan(ka);
ku=tan(2*alfa+phim-%pi/2); Xc3(NumProfile)=-v;
Rc3(NumProfile)=SinPhiMax; Xp3(NumProfile)=Xc3(NumProfile)+u;
Rp3(NumProfile)=SinPhiMax-u/ku; kc3(NumProfile)=ka;
kp3(NumProfile)=ku; // iterates to construct the new portions for
i=(NumProfile-1):-1:1 hhh=SinPhiMin+(i)*SinPhiStep; //y coord of
the new front portion //coords of the new front portion
[Xc3(i),Rc3(i)]=linecross(Xc3(i+1),Rc3(i+1),kc3(i+1),0,hhh,0);
//Abbe angle phi=-atan(Rc3(i)/Xc3(i)); //height of Abbe ray
h=b*sin(phi); //find the place where the Abbe ray interacts the
front surface for j=NumProfile:-1:i if h>Rc3(j) then hpl=j;
break; end; end; auxs=kc3(hpl+1);
hx=Xc3(hpl+1)+(h-Rc3(hpl+1))/auxs; // x coord, y is h // refraction
on the front surface, determine the slope of the refracted ray
auxs=-1/kc3(hpl+1); alfai=atan(auxs);//incident angle
alfao=asin(n0*sin(alfai)/n1); // refraction angle
kRefractedRay=tan(atan(auxs)-alfao); //slope of the refracted ray
// coord of the new back portion is determined by extending the
existing portion (slope) and then intersecting with the refracted
ray
[Xp3(i),Rp3(i)]=linecross(hx,h,kRefractedRay,Xp3(i+1),Rp3(i+1),kp
3(i+1)); // Determine the slope of the back portion and the front
portion klink=slope2p(Xc3(i),Rc3(i),Xp3(i),Rp3(i));//klink is the
slope of the line connects the two points
[kp3(i)]=mirrorslope10(kRefractedRay,klink);
[kc3(i)]=mirrorslope10(-tan(phi),klink); end //*********** plot the
profiles******************* plot(Xc3, Rc3, Xp3,Rp3); set(gca(
),"isoview","on"); mtlb_grid; //***********output to a txt file
*********************** if pfile==1 then BacksurfaceShift=0.2;
//**********accomodate to lightool lens spline sweep
u=file(`open`,`.\result.txt`,`unknown`);
fprintf(u,`%f,%f,%f,%f\n`,0,-Xc3(1),0,Xp3(1)-BacksurfaceShift); for
i=1:(NumProfile/500):NumProfile
fprintf(u,`%f,%f,%f,%f\n`,Rc3(i),-Xc3(i),Rp3(i),Xp3(i)-
BacksurfaceShift); end; i=NumProfile;
fprintf(u,`%f,%f,%f,%f\n`,Rc3(i),-Xc3(i),Rp3(i),Xp3(i)-
BacksurfaceShift); file(`close`,u); end;
[0133] It is to be understood that, while the above described
design method may be employed in some embodiments to design
concentrators (or equivalent collectors, as described below) of the
type described herein, other designs methods may be used. For
example, in some embodiments, an edge ray approach may be used, in
which both edges of the image formed by the concentrator is
required to be bound by rays from opposite edges of the source
(i.e., incoming rays at the edges of the input pupil of the
concentrator incident at angles corresponding to the acceptance.) A
general treatment of edge ray design techniques may be found, e.g.,
in Roland Winston et al, Nonimaging Optics, Academic Press
(Elsevier) 2005. In typical embodiments, such edge ray techniques
do not result in a perfectly aplanatic device, but instead present
a trade off between acceptance angle and spot size at the image
plane. However, in many cases, for relatively small acceptance
angles (e.g., less than 5.0 degrees, less than 2.5 degrees, less
than 1.0 degrees, les than 0.5 degrees, or smaller), the spot size
increases only slowly (e.g., quadratically) as a function of
acceptance angle. Accordingly, for may applications, the edge ray
design may result in a concentrator having a suitable acceptance
angle while suffering from only slight spherical aberration.
[0134] Any suitable manufacturing technique may be employed to
manufacture concentrators based on designs produced using the above
described techniques. For example, process 1400 may output the
concentrator design in the form of computer instructions to be
implemented on one or more automated manufacturing devices.
[0135] It is to be understood that the above described devices may
include any suitable materials. Surfaces of concentrator 100 may
include any suitable optical coating (e.g. anti-reflective coating)
or other treatment. Although one-way light admitting surface
portions which employ TIR have been described, any other suitable
techniques known in the art may be employed to selectively provide
one-way light admission.
[0136] Also disclosed herein is a method of concentrating light
using a concentrator of the type disclosed herein. In various
embodiments include directing light from a source onto the
concentrator to be concentrated in a concentration region. An
absorber may be positioned in or near the concentration region to
absorb concentrated light. The absorber may be used to convert the
concentrated light energy to another form of energy, e.g.
electrical, thermal, chemical, or mechanical energy. Various
embodiment may include cooling the concentrator or absorber, e.g.,
by circulation of fluid.
[0137] Although the above examples have shown a concentrator 100
which operates to receive light from a source incident on the front
surface and concentrate the light to a concentration region, it is
to be understood that the same device may also be used "in reverse"
to collect light from source located at the concentration region
and form a collimated beam from the collected light which is output
from the front surface. For example, referring to FIG. 16,
concentrator 100 is employed as a light collector. A light source
1600 (e.g. an LED, OLED, laser, lamp, filament, infrared source,
etc.) is located at or near the focal point in the focal plane of
the concentrator 100. As illustrated by rays 200, light from source
1600 is collected from the source and collimated to form beam 1601.
Beam 1601 is output from front surface 102. Beam 1601 may be
directed (directly or using any suitable optical elements) to a
target (not shown) to provide illumination. In some embodiments,
several source/collector devices may be used, e.g. arranged in an
array to provide a combined output beam.
[0138] Various embodiments of concentrator 100, when used in the
above described collector configuration, may have any of the
optical characteristics of concentrators described herein. For
example, in some embodiments, the concentrator can be imaging and
aplanatic, as described above. In some embodiments, the collector
can operate to collect substantially all of the light emitted from
the source at angles ranging from 0 to 30 degrees, 0 to 40 degrees,
0 to 50 degrees, or even 0 to 60 degrees or greater from the
optical axis. In various embodiments, at least 50%, 60%, 70%, 80%,
or even more of the light energy or power (i.e., energy per unit
time) emitted from the source is collected into the beam.
[0139] As will be understood by one skilled in the art, a collector
of this type may be used advantageously in any application where
efficient collection of light into a well collimated beam is
desired. For example, in some embodiments, the collector may be
used in a flashlight to collect light from an led source into an
intense, well collimated beam. One or more collectors of this type
may be used in other types of illumination devices including, for
example, illuminated signs, traffic signals, lighting fixtures,
etc. One or more collectors of this type may be included in any
know detector device or system which employs a collimated beam,
including, for example a position or motion detector (e.g. as used
for range finding, security applications, speed detection, etc.)
One or more collectors of this type may be included in any know
optical communication device or system, e.g., an optical switch. In
some embodiments, the output beam of the collector may be coupled
into an optical fiber, wave guide, etc.
[0140] In some embodiments, a method may include the step of
providing a device for collecting light from a source into a beam
of light (e.g., concentrator 100, operating in the collector
configuration, henceforth a "collector"). As described in detail
above, in some embodiments, collector 100 includes a front surface
including a selectively light transmitting portion, a back surface
including a reflecting portion facing the internal region; and an
internal region disposed between the front surface and back
surface. The selectively light transmitting portion includes a side
facing the internal region.
[0141] The method may further include the step of using the side of
the selectively light transmitting portion facing the internal
region to selectively reflect light incident from the source back
through the internal region towards the reflecting portion of the
back surface.
[0142] The method may further include the step of using the
reflecting portion of the back surface to reflect the light from
the front surface back through the internal region towards the
front surface.
[0143] The method may further include using the selectively light
transmitting portion to selectively transmit at least a portion of
light incident from the reflecting portion of the back surface out
of the internal region to form the beam of light.
[0144] One or more or any part thereof of the techniques described
herein can be implemented in computer hardware or software, or a
combination of both. The methods can be implemented in computer
programs using standard programming techniques following the method
and figures described herein. Program code is applied to input data
to perform the functions described herein and generate output
information. The output information is applied to one or more
output devices such as a display monitor. Each program may be
implemented in a high level procedural or object oriented
programming language to communicate with a computer system.
However, the programs can be implemented in assembly or machine
language, if desired. In any case, the language can be a compiled
or interpreted language. Moreover, the program can run on dedicated
integrated circuits preprogrammed for that purpose.
[0145] Each such computer program is preferably stored on a storage
medium or device (e.g., ROM or magnetic diskette) readable by a
general or special purpose programmable computer, for configuring
and operating the computer when the storage media or device is read
by the computer to perform the procedures described herein. The
computer program can also reside in cache or main memory during
program execution. The analysis method can also be implemented as a
computer-readable storage medium, configured with a computer
program, where the storage medium so configured causes a computer
to operate in a specific and predefined manner to perform the
functions described herein. In some embodiments, the computer
readable media is tangible and substantially non-transitory in
nature, e.g., such that the recorded information is recorded in a
form other than solely as a propagating signal.
[0146] A number of embodiments of the invention have been
described. Nevertheless, it will be understood that various
modifications may be made without departing from the spirit and
scope of the invention.
[0147] As used herein the term "light" and related terms (e.g.
"optical") are to be understood to include electromagnetic
radiation both within and outside of the visible spectrum,
including, for example, ultraviolet and infrared radiation.
* * * * *
References