U.S. patent application number 11/350627 was filed with the patent office on 2006-08-24 for led illumination devices.
Invention is credited to Mark S. Olsson.
Application Number | 20060187653 11/350627 |
Document ID | / |
Family ID | 36912470 |
Filed Date | 2006-08-24 |
United States Patent
Application |
20060187653 |
Kind Code |
A1 |
Olsson; Mark S. |
August 24, 2006 |
LED illumination devices
Abstract
A lens element has a curved surface mounted adjacent an LED for
improving the light transmission efficiency and the dispersal
pattern of radiation emitted by the LED.
Inventors: |
Olsson; Mark S.; (La Jolla,
CA) |
Correspondence
Address: |
MICHAEL H JESTER
505 D GRAND CARIBE CAUSEWAY
CORONADO
CA
92118
US
|
Family ID: |
36912470 |
Appl. No.: |
11/350627 |
Filed: |
February 9, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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60652317 |
Feb 10, 2005 |
|
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Current U.S.
Class: |
362/111 ;
257/E33.073 |
Current CPC
Class: |
F21Y 2115/10 20160801;
F21K 9/69 20160801; G03B 2215/0567 20130101; F21W 2107/20 20180101;
F21V 5/041 20130101; H01L 33/58 20130101; H01L 2924/0002 20130101;
H01L 2924/0002 20130101; H01L 2924/00 20130101 |
Class at
Publication: |
362/111 |
International
Class: |
F41G 1/34 20060101
F41G001/34 |
Claims
1. An illumination device, comprising: an LED; a lens element with
a curved surface positioned opposite a light emitting surface of
the LED; and a quantity of transparent material joining the lens
element and light emitting surface of the LED.
2. The illumination device of claim 1 and further comprising a
second lens element mounted adjacent the lens element positioned
opposite the light emitting surface of the LED.
3. The illumination device of claim 1 wherein the lens element is
made of Cubic Zirconia.
4. The illumination device of claim 1 wherein a distance between a
light emitting surface of the LED and the curved surface of the
lens element is less than about two times a longest dimension of
the light emitting surface of the LED.
5. The illumination device of claim 1 wherein the lens element is
generally spherical and has a diameter greater than about three
times a longest dimension of a light emitting surface of the
LED.
6. The illumination device of claim 1 wherein the lens element has
an index of refraction greater than about 1.65 and the silicone gel
has an index of refraction less than about 1.50.
7. An illumination device, comprising: a substrate; a least one LED
mounted on the substrate and having an exposed metal heat
conduction surface; at least one aperture formed in the substrate
adjacent to the exposed metal heat conduction surface of the diode;
and a heat sink mounted in the aperture.
8. The illumination device of claim 7 and further comprising a
clamp structure for biasing the metal heat conduction surface
against the heat sink.
9. A method of fabricating an illumination device, comprising the
steps of: removing a top section of an optically transparent cover
of a high intensity LED and lens assembly leaving a remaining lower
section having a height dimension less than about twice a longest
dimension of a light emitting surface of the LED; and mounting a
lens element on top of the lower section, the lens element having a
curved surface that faces the light emitting surface of the
LED.
10. The method of claim 9 and further comprising the step of
leaving a sufficient amount of transparent silicone gel to serve as
an optical interface joining the light emitting surface and the
generally spherical lens element.
11. An illumination device, comprising: a light emitting diode; a
generally spherical lens mounted adjacent to a light emitting
surface face of the light emitting diode and positioned no further
away from the light emitting surface than twice the longest
dimension of the light emitting surface; the spherical lens having
an index of refraction relative to light emitted by the diode
greater than about 1.65; the spherical lens having a diameter
greater than three times the longest dimension of the light
emitting surface; and a space between the spherical lens and the
light emitting surface being filled with an intervening optically
transparent material selected from the group consisting of fluid,
grease, gel and elastomer having an index of refraction less than
about 1.50.
12. The illumination device of claim 11, wherein the spherical lens
is made of Cubic Zirconia.
13. The illumination device of claim 11, wherein the spherical lens
is made of Sapphire.
14. The illumination device of claim 11, wherein the spherical lens
is made of SF8 Optical Glass.
15. The illumination device of claim 11, wherein the intervening
optically transparent material is silicone gel.
16. The illumination device of claim 11, wherein the intervening
optically transparent material is silicone rubber.
17. The illumination device of claim 11 wherein the spherical lens
is press fit into a thermally conductive metal support
structure.
18. An illumination device, comprising: a substrate; a light
emitting diode having an exposed metal heat conduction surface
mounted on the substrate; an aperture formed in the substrate
adjacent to the metal heat conduction surface; and heat sink means
extending through the aperture for dissipating heat from the
exposed diode metal heat conduction surface.
19. The illumination device of claim 18 wherein the heat sink means
is made of anodized Aluminum.
20. The illumination device of claim 18 wherein the heat sink means
is made of a material selected from the group consisting of Copper
and Copper alloy.
21. The illumination device of claim 18 wherein the heat sink means
is made of an insulated Copper alloy.
22. The illumination device of claim 18 wherein the heat sink means
is made of a Copper alloy insulated with a diamond film.
23. The illumination device of claim 18 and further comprising
means for clamping the metal heat conduction surface against the
heat sink means.
24. The illumination device of claim 18 wherein the heat sink means
includes an anodized Aluminum pin press fit into a second heat
sink.
25. The illumination device of claim 18 wherein the metal heat sink
means includes an anodized Aluminum pin that extends into the
aperture.
26. An illumination device, comprising: a surface mounted light
emitting diode with an exposed metal heat conduction surface; a
heat sink; and a spring clamp for holding the metal heat conduction
surface against the heat sink.
27. The illumination device of claim 26 wherein the spring clamp
includes a metal disc spring.
28. The illumination device of claim 26 wherein the spring clamp
includes a Beryllium Copper metal disc spring.
29. A illuminated device, comprising: a light emitting diode; a
generally spherical lens element mounted adjacent to a light
emitting surface of the light emitting diode; the spherical lens
element having an index of refraction relative to light emitted by
the diode that is greater than about 1.65; and a side of the
spherical lens element opposite the light emitting surface being in
contact with an optically transparent material with an index of
refraction greater than about 1.20.
30. The illumination device of claim 29 wherein the optically
transparent material is water.
31. The illumination device of claim 29 wherein the optically
transparent material is mineral oil.
32. The illumination device of claim 29 wherein the optically
transparent material is a 3M Fluorinert.TM. fluid.
33. The illumination device of claim 29 wherein the optically
transparent material is a 3M Novec.TM. fluid.
34. The illumination device of claim 29 wherein the optically
transparent material is silicone rubber.
35. The illumination device of claim 29 wherein the optically
transparent material is silicone grease.
36. The illumination device of claim 29 wherein the optically
transparent material is polyurethane rubber.
37. An illumination device, comprising: a light emitting diode; a
spherical lens element mounted adjacent a light emitting surface of
the light emitting diode; the spherical lens element having an
index of refraction relative to light emitted by the diode of
greater than about 1.80; and a negative focal length optical
element placed in front of the spherical lens element to form the
light into a beam having a predetermined shape.
38. The illumination device of claim 37 wherein the negative
optical element has a prismatic component to redirect the light
beam off axis.
39. The illumination device of claim 37 wherein the negative focal
length optical element has a cylindrical component to change an
aspect ratio of the light beam.
40. A method of constructing an illumination device, comprising the
steps of: cutting off a section of an optically transparent cover
that encapsulates a light emitting diode, leaving a remaining
section above a light emitting surface of the diode no greater than
twice the longest dimension of the light emitting surface; and
mounting a generally spherical Cubic Zirconia lens element having
an index of refraction relative to the diode emitted light greater
than about 1.65, and having a diameter greater than about three
times the longest dimension of the light emitting surface.
41. The method of constructing an illumination device of claim 40
wherein the optically transparent cover is made of silicone
rubber.
42. The method of constructing an illumination device of claim 40
wherein the optically transparent cover is made of a silicone
rubber dome-like cover that encloses a silicone gel filled volume
surrounding the light emitting diode.
43. A method of controlling the output light pattern of a light
emitting diode source, comprising the steps of: using a Cubic
Zirconia spherical lens element to converge the light from a light
emitting diode; and using a second diverging optical element to
diverge the light by a predetermined amount.
44. The method of claim 43 wherein the diverging optical element is
a molded transparent plastic.
45. The method of claim 43 wherein the diverging optical element is
a molded acrylic plastic.
46. The method of claim 43 wherein an aperture of predetermined
size is placed between the Cubic Zirconia spherical lens element
and the second diverging optical element to remove light from the
edges of the beam.
47. The method of claim 43 wherein a space between the spherical
lens element and the diverging optical element is filled with a
transparent incompressible material selected from the group
consisting of fluid, grease, gel, elastomer and rubber-like
material.
48. The method of claim 46 wherein a space between the spherical
lens element and the diverging optical element is filled with a
transparent incompressible material from the group of fluid,
grease, gel or elastomer or rubber-like material.
49. An illumination device, comprising: a light emitting diode; a
generally spherical lens element mounted adjacent a light emitting
surface face of the light emitting diode and placed no further away
from said light emitting surface than about twice the longest
dimension of said light emitting surface; the spherical lens
element having an index of refraction relative to light emitted by
the diode of greater than about 1.80 to converge the light to a
focus; the spherical lens element having a diameter greater than
about three times the longest dimension of the light emitting
surface; a light path optical space between the spherical lens
element and the light emitting surface being filled with an
intervening optically transparent material selected from the group
consisting of fluid, grease, gel elastomer and rubber-like material
having an index of refraction less than about 1.60; and an aperture
placed approximately at a plane of focus smaller than a diameter of
the spherical lens.
50. The illumination device of claim 49 wherein the spherical lens
element is made of Cubic Zirconia.
51. An illumination device, comprising: a light emitting diode; a
generally spherical lens element mounted adjacent to a light
emitting surface face the light emitting diode and placed no
further away from the light emitting surface than about twice a
longest dimension of the light emitting surface; the spherical lens
element having an index of refraction relative to light emitted by
the diode greater than about 1.80 to converge the light to a focus;
the spherical lens element having a diameter greater than about
three times the longest dimension of the light emitting surface; a
light path optical space between the spherical lens element and the
light emitting surface being filled with an intervening optically
transparent material selected from the group consisting of fluid,
grease, gel, elastomer or rubber-like material having an index of
refraction less than about 1.60; and a spacer to set the distance
between the spherical lens element and the light emitting surface
to a predetermined distance.
52. The illumination device of claim 51 wherein the inside surface
of the spacer is reflectorized.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims benefit under 35 USC Sections 119(e)
and 120 to the filing date of U.S. Provisional Application Ser. No.
60/652,317 filed by Mark S. Olsson on Feb. 10, 2005.
FIELD OF THE INVENTION
[0002] The present invention relates to lighting, and more
particularly, to illumination devices that use light emitting
diodes (LEDs) as a source of light.
BACKGROUND OF THE INVENTION
[0003] Semiconductor LEDs have replaced conventional incandescent,
fluorescent and halogen light sources in many applications due to
their small size, reliability, relatively inexpensive cost, long
life and compatibility with other solid state devices. In a
conventional LED, an N-type gallium arsenide substrate that is
properly doped and joined with a P-type anode will emit light in
visible and infrared wavelengths under a forward bias. In general,
the brightness of the light given off by an LED is contingent upon
the number of photons that are released by the recombination of
carriers inside the LED. The higher the forward bias voltage, the
larger the current and the larger the number of carriers that
recombine. Therefore, the brightness of an LED can be increased by
increasing the forward voltage. However due to many limitations,
including the ability to dissipate heat, conventional LEDs are only
capable of producing about six to seven lumens.
[0004] Recently a new type of LED has been developed for use as a
flash in camera phones. The Luxeon.RTM. Flash LXCL-PWF1 and
LXCL-PWF2 LEDs commercially available from Lumileds Lighting of San
Jose, Calif., USA are capable of producing forty lumens at one
ampere, and eighty lumens at one ampere, respectively. These
surface mounted LEDs are only one millimeter in height and they
have a very small footprint (2.0.times.1.6 mm or 3.2.times.1.6 mm,
respectively). They are rated for 100,000 flashes at one ampere,
and one hundred and sixty-eight hours of DC (flashlight/torch mode)
at 350 milliamperes.
[0005] While these new flash LEDs offer increased brightness over
conventional LEDs they still suffer from problems associated with
heat dissipation and inefficient distribution of light.
SUMMARY OF THE INVENTION
[0006] In accordance with an embodiment of the invention an
illumination device includes an LED and a lens element with a
curved surface positioned opposite a light emitting surface of the
LED. A quantity of transparent material joins the lens element and
the light emitting surface of the LED.
[0007] In accordance with another embodiment of the invention an
illumination device includes at least one LED mounted on a
substrate and having an exposed metal heat conduction surface. At
least one aperture is formed in the substrate adjacent to the
exposed metal heat conduction surface of the LED and a heat sink is
mounted in the aperture.
[0008] In accordance with another embodiment of the invention a
method of fabricating an illumination device includes the steps of
removing a top section of an optically transparent cover of a high
intensity LED package and leaving a remaining lower section having
a height dimension less than about twice a longest dimension of a
light emitting surface of an LED in the LED package. The method
further includes the step of mounting a lens element on top of the
lower section, the lens element having a curved surface that faces
the light emitting surface of the LED.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] Throughout the drawing figures, like numerals refer to like
parts.
[0010] FIG. 1 is a diagrammatic side view of an embodiment of the
present invention.
[0011] FIG. 2 illustrates the light focusing properties of the
embodiment of FIG. 1.
[0012] FIG. 3 illustrates another embodiment in which the LED and
the transparent element are surrounded by a metal face plate.
[0013] FIG. 4 illustrates another embodiment similar to that of
FIG. 3 except that the transparent element is formed as a truncated
ball lens.
[0014] FIG. 5 illustrates another embodiment similar to that of
FIG. 3 except that the face plate has a spherical ball support.
[0015] FIG. 6 illustrates another embodiment with reflectors.
[0016] FIG. 7 illustrates another embodiment with a thermal
fluid.
[0017] FIG. 8 illustrates another embodiment with an anodized
Aluminum face plate.
[0018] FIG. 9 illustrates another embodiment with a thermal
cup.
[0019] FIG. 10 illustrates another embodiment with a steerable
beam.
[0020] FIG. 11 illustrates an alternate embodiment with a steerable
beam.
[0021] FIG. 12 illustrates another embodiment with a hemispherical
lens.
[0022] FIG. 13 is an isometric view of a prior art LED and lens
assembly.
[0023] FIG. 14 is a vertical sectional view through the prior art
LED and lens assembly of FIG. 13.
[0024] FIG. 15 is an isometric view of an LED and spherical lens
assembly in accordance with another embodiment of the present
invention.
[0025] FIG. 16 is a vertical sectional view through the LED and
spherical lens assembly of FIG. 15.
[0026] FIG. 17 is an isometric view of another embodiment of the
present invention similar to FIG. 15 in which the top of the
spherical lens has been truncated.
[0027] FIG. 18 is a vertical sectional view of the embodiment of
FIG. 17.
[0028] FIG. 19 is an isometric view of another embodiment of the
present invention in which the lens comprises half of a sphere,
with a flat surface facing upwardly.
[0029] FIG. 20 is a vertical sectional view through the embodiment
of FIG. 19.
[0030] FIG. 21 is an isometric view of another embodiment in which
the lens comprises half of a sphere, with the flat surface facing
downwardly.
[0031] FIG. 22 is a vertical sectional view of the embodiment of
FIG. 21.
[0032] FIG. 23 is an isometric view illustrating the manner in
which a portion of a commercially available high intensity LED
assembly may be removed.
[0033] FIG. 24 is a vertical sectional view illustrating the
removal of a part of a commercially available high intensity LED
with a blade.
[0034] FIG. 25 is a side-elevation view illustrating the
dimensional relationships of another embodiment of the present
invention that employs a spherical lens element.
[0035] FIG. 26 is a vertical sectional view through another
embodiment of the present invention similar to the embodiment of
FIG. 25 and in addition, employing heat sinks.
[0036] FIG. 27 is a part vertical section, part side elevation view
of the embodiment of FIG. 26.
[0037] FIG. 28 is a part vertical section, part side elevation view
illustrating another embodiment of the present invention
particularly suited for underwater use.
[0038] FIG. 29 is a part vertical section, part side elevation view
of another embodiment of the present invention employing a
diverging optical element having a negative focal length.
[0039] FIG. 30 is a part vertical section, part side elevation view
of another embodiment of the present invention employing a second
optical element in the form of a prismatic lens.
[0040] FIG. 31 is a part vertical section, part side elevation view
of another embodiment of the present invention suited for a hidden
flush mount application.
[0041] FIG. 32 is a part vertical section, part side elevation view
of another embodiment of the present invention with a second
optical element having a hemispherical socket for receiving a
spherical lens element.
[0042] FIG. 33 is an isometric view of a thru-hull light
constructed in accordance with the present invention.
[0043] FIG. 34 is a side elevation view of the thru-hull light of
FIG. 33.
[0044] FIG. 35 is an exploded isometric view of the thru-hull light
of FIG. 33.
[0045] FIG. 36 is a vertical section view of the thru-hull light of
FIG. 33, taken along line 36-36 of FIG. 34.
[0046] FIG. 37 is a top plan view illustrating the arrangement of
LED light assemblies within the thru-hull light of FIG. 33.
[0047] FIG. 38 is an isometric view of another embodiment of the
present invention that utilizes a rod lens element.
[0048] FIG. 39 is a vertical section view through the embodiment of
FIG. 38.
[0049] FIG. 40 is an isometric view of another embodiment of the
present invention that utilizes a rod lens element with rounded
upper and lower ends.
[0050] FIG. 41 is a vertical section view through the embodiment of
FIG. 40.
DETAILED DESCRIPTION
[0051] The entire disclosure of Provisional Application Ser. No.
60/652,317 of Mark S. Olsson filed Feb. 10, 2005, is hereby
incorporated by reference.
[0052] Referring to FIG. 1, a flash LED 10 is surface mounted on a
circuit supporting element 14 in the form of a planar printed
circuit board (PCB). A flat facet (not visible) of a substantially
spherical optically transparent element 12 measuring approximately
3/16 inches in diameter is bonded to the active upper face of the
flash LED 10. One suitable commercially available adhesive is
transparent, high temperature adhesive designated Loctite 382 (Tak
Pak). The flash LED 10 is preferably the previously identified
Luxeon.RTM. Flash LXCL-PWF1 LED or LXCL-PWF2 LED commercially
available from Lumileds Lighting. Further details ofthese LEDs may
be found in the list of issued U.S. Patents and pending U.S. patent
applications set forth in Appendix A of the aforementioned
provisional application, the entire disclosures of which are hereby
incorporated by reference. The optically transparent element 12 is
preferably made of sapphire. The total light output of the device
illustrated in FIG. 1 was found to be approximately fifteen percent
greater than the flash LED 10 by itself. It is believed that this
increase in total light output is due to improved heat dissipation
from the front side of the emitter of the flash LED 10 and the
region immediately around the emitter due to the proximity of the
sapphire element 12, which is an excellent conductor of heat.
Unlike conventional LEDs, the flash LED 10 is not bonded directly
to a massive metal substrate so the sapphire element 12 provides
alternate means of heat removal from the flash LED 10. In addition,
the sapphire element 12 can affect the radiation emitted by the
flash LED 10 by focusing the same into a beam.
[0053] Besides sapphire, transparent ceramics such as Magnesia
(MgO), magnesium aluminate spinel (Mg Al2O4), aluminum oxynitride
spinel (AlON), cubic zirconia (ZRO2Si), spinel (MgO.times.Al2O3)
and rutile (TiO2) can also be used for the transparent element 12
due to their a high thermal conductivity. It is preferable that the
transparent element 12 be made of a material that has at least half
or more of the thermal conductivity of sapphire. Sapphire has an
additional advantage of having a high index of refraction, such
that when element 12 is made of properly shaped sapphire, it can
focus the radiation emitted by the flash LED 10 into a highly
useful slightly diverging beam
[0054] Heat transfer is improved by using a body 16 of an optically
transparent material to thermally couple the flash LED 10 and the
transparent element 12. The body 16 may be transparent fluid,
grease, gel or polymer. One suitable material is DOW CORNING.RTM.
compound 4 (DC 4) which is stable up to four hundred degrees F (204
C.) which is above the maximum operating temperature of the flash
LED 10. Certain fluorocarbon thermal management fluids such as 3M
Novec.RTM. Engineered Fluids (HFE-7200) or 3M Fluorinertg
Electronic Liquids. HFE-7000 has a boiling point of 76 C., which is
well below the operating temperature of the flash LED 10. Boiling
off of the cooling fluid, on and adjacent to the flash LED 10 can
provide significant additional cooling. For additional cooling
forced fluid flow and channels can be provided adjacent the flash
LED 10. The flash LED 10 and body 16 can be pressed against the
base of the transparent element 12 with a spring or using the
resilience of the PCB 14, as indicated by the arrows 18.
[0055] FIG. 2 illustrates the manner in which the generally
spherical transparent element 12 forms the radiation emitted by the
flash LED 10 into a beam represented by light rays 30. The gap
between the face of the flash LED 10 and the underside of the
transparent element 12 is filled with a transparent grease or gel
32.
[0056] A low melting point metal could also be used as a heat
conducting element all around the sides of the flash LED 10. Metals
such as bismuth or gallium with a melting point well below the
maximum operating temperature of the flash LED 10 can be used.
Among these are ten specialty solders commercially available from
Indium Corporation of America having melting points below 140
degrees C.
[0057] Another aspect of the present invention involves press
fitting a sapphire sphere or a modified sapphire sphere into a
surrounding metal structures. High thermal conductivity metals such
as copper, brass, bronze and aluminum are particularly suitable in
this application, but other metals such as stainless steel and
titanium may suffice in particular environments. A press fit
provides an optimal thermal coupling between the sapphire element
and the metal structure. The metal structure may be in thermal
contact with other structures to provide greater heat sink
capabilities. Referring now to FIG. 3, a sapphire sphere 12 is
press fit into a cylindrical bore in a metal face plate 40.
Optionally, a sealant 42 fills the peripheral gap between the upper
side of the sapphire sphere 12 and the upper surface of the face
plate 40. At its largest outside diameter 44 the sapphire sphere 12
engages the wall of the bore in the metal faceplate 40, the
tolerances being controlled to provide a snug fit. The sapphire
sphere 12 is press fit into close proximity with the upper active
face of the flash LED 10, but not in contact therewith. The region
of the bore in the metal faceplate 40 beneath the sapphire sphere
12 and between the sphere 12 and the flash LED 10 are filled with
transparent grease or gel 16. Arrows 46 illustrate the flow of heat
from the flash LED 10 into the sapphire sphere 12 and from the
sapphire sphere 12 into the surrounding metal face plate 40. Arrows
48 illustrate the flow of heat through the front or upper side of
the sapphire sphere 12, which acts as both a heat sink and a lens,
into the gas or liquid above the sapphire sphere 12.
[0058] FIG. 4 illustrates another embodiment similar to that of
FIG. 3 except that the transparent element is formed as a truncated
ball lens 50. Its upper flat surface forms a wider beam of
radiation.
[0059] FIG. 5 illustrates another embodiment similar to that of
FIG. 3 except that the bore in the metal face plate 60 is formed
with a curved shoulder 61 that supports the underside of the
sapphire sphere 12 in precise position in close proximity to the
flash LED 10. Thus a so-called "ball mill plunge cut" in the metal
face plate 60 can provide an advantageous mounting for the sapphire
sphere 12. The curved shoulder 61 provides a matched radius surface
that increases the area of contact between the sapphire sphere 12
and the metal face plate 60. This type of mounting also allows the
sapphire sphere 12 to withstand high loads and pressures on the
outside face and remain fully supported, as might be encountered in
undersea applications. In this embodiment a quantity of a suitable
transparent potting material 62 completely covers the upper side of
the sapphire sphere 12 and has an upper surface flush with the
upper surface of the metal face plate 60. Various other methods can
be used to seal the bore, including glues, adhesives, potting
compound, rubber gaskets, and elastomeric O-rings.
[0060] While press fitting the sapphire sphere has certain
advantages, it is not essential to the present invention. Other
means for holding the transparent element 12 in place can be used,
be they mechanical or adhesive. A thermal shrink fit can also be
employed. By way of example only, mounting a sapphire sphere 12 in
a bore in an aluminum alloy (7075, 6061 or 6262) or brass alloy (CA
360 ) with a press fit of about one percent smaller than the
diameter of the pressed sphere has produced good results. With
softer materials press fits as high as two percent have been
successful.
[0061] FIG. 6 illustrates an alternate embodiment in which metal
face plate 70 has a counter-sunk bore, the outwardly tapered part
71 of which forms a reflector. The sapphire sphere 12 is press fit
into the lower cylindrical segment of the bore and has a flat
underside or facet 74 that is in direct physical contact with the
upper active face of the flash LED 10. This maximizes heat
extraction. A thermally conductive reflector 72 is inserted into
the lower cylindrical part of the bore before the sapphire sphere
12 is inserted.
[0062] In the embodiment of FIG. 7, the sapphire sphere 12 is
snugly inserted into a hole in a thin metal face plate 80, and sits
on top of the flash LED 10. A thermally conductive fluid 82,
preferably with a low viscosity, is circulated via pump means (not
illustrated) in a channel or conduit formed between the face plate
80 and the PCB 14. The fluid flows around the sides of the sapphire
sphere 12 as indicated by the arrows 84, providing a heat
exchanger. The flash LED 10 can be supported on a pair of either
separate or insulatively joined posts (not illustrated) to maximize
convective or forced flow of cooling fluid past the flash LED 10.
The cooling fluid can flow by convection instead of active pumping.
The embodiment of FIG. 7 can provide enhanced performance of the
flash LED 10 even where the sapphire sphere 12 is eliminated and
replaced with a window having minimal heat transfer properties.
[0063] Referring to FIG. 8, the sapphire sphere 12 is first press
fit into a bore in an aluminum face plate 92, which is thereafter
anodized to provide protective anodize layers 90. However,
importantly there is no anodize layer 90 where the face plate 92
contacts the sapphire sphere 12 to ensure maximum heat transfer.
The growth of the anodize layer 90 helps lock the sapphire sphere
12 in position at lock points 94. The face plate 92 is in direct
thermal contact with, but electrically insulated from, Copper
traces 96 on PCB 14 by direct contact with anodized surface 98. A
metal plate 100 backs the PCB 14 to provide further heat transfer.
In the preferred embodiment, a hard type III anodize surface is
used for greater corrosion resistance, using any of the known
sealing methods such as dichromate, nickel acetate and hot
water.
[0064] A further aspect of the present invention involves the use
of the anodized coating as an electrical insulating layer between
the conductive traces 96 on the PCB 14 and the anodized aluminum
face plate 92. Bare, large surface area conductors can be used on
the LED side of the PCB 14 and held in mechanical contact with the
insulating surface of the face plate 92 to maximize thermal
contact. The anodized layers 90 can be made very thin and therefore
provide very good thermal conductors. The thermal grease 16
provides even further heat transfer efficiency. Extra thick copper
traces 96 can further enhance heat extraction.
[0065] Conventional techniques to remove backside heat from the PCB
14 can also be used in addition to those illustrated. The
efficiency and operating life of the flash LED 10 are improved if
its operating temperature can be reduced. Conventional techniques
include heavy copper traces, metal cores in the PCB 14, the
inclusion of thermal vias, thermal fillers (T-Lam), multi-layer
PCBs with copper flood planes, and conventional heat sinks.
[0066] Referring to FIG. 9, the sapphire sphere 12 is supported on
the concave upper reflective surface 112 of a thermal cup 110. The
flash LED 10 is mounted in receptacle in the thermal cup 110 and is
held via solder joints 114. A wire 118 is held by a solder joint
116 to the underside of the flash LED 10. The wire has an optional
insulator jacket 120 and extends through a central hole in the
thermal cup 110 and is soldered to the PCB 14. A metal filler 122,
which may be low melting point metal or solder, may join the
periphery of the flash LED 10 and the walls of the receptacle in
the thermal cup 110.
[0067] The shape of the beam formed by the transparent element 12
can be adjusted by various means. Where the transparent element 12
is a sapphire sphere and mounted completely or partially in a
socket or recess in a front plate such as 80, the region above the
transparent element 12 can be filled with a transparent compound.
If this compound has a flat outer surface the beam will be spread
into a wider, less focused beam. The higher the index of refraction
of the potting material, the less focused, and hence the wider the
beam will be. Alternately, a polished flat or facet can be ground
or otherwise formed on the upper side of the sapphire sphere 12
before installation into the face plate 80. Generally, although not
necessarily, the plane of this facet would be parallel with the
outer plane of the face plate 80. The facet could be a small area
at the apex of the sapphire sphere or a much larger facet if the
sapphire is a hemisphere. The larger the area of the facet, the
less focused the beam will be. The upper and/or lower surfaces of
the transparent element 12 could be frosted by chemical etching or
mechanical techniques such as sandblasting to diffuse and soften
the beam. The lower apex of the transparent element 12 can be
ground or polished to provide a small facet having an area that is
approximately the same as the emitter area of the flash LED. In
general, it has been found that larger diameter sapphire spheres
provide higher optical coupling efficiencies (brighter beams) and
smaller sapphire spheres produce more tightly focused beams. It is
preferable to remove the reverse voltage protection die on the
flash LED 10 in order to achieve maximum thermal coupling.
[0068] Over a range of about thirty to forty-five degrees, from the
normal (Z-axis) to the face plate 80, the beam can be steered
simply by laterally shifting (in X and Y) the position of the flash
LED 10 relative to the central axis of the bore in the face plate
80. This results in greater de-focusing and an increasing
separation between the sapphire sphere 12 and the flash LED 10.
This may impair heat transfer, but this can be offset by
introducing a component of Z axis movement in combination with X-Y
scanning to keep the flash LED 10 as close as possible to the
surface of the sapphire sphere 12.
[0069] Referring to FIG. 10, the sapphire sphere 12 is mounted on a
thermal reflector cup 130 supported on PCB 14 which is carried by a
mechanical pivot (not illustrated). This construction allows the
sapphire sphere 12 to swivel inside the bore or socket formed in
face plate 80 as indicated by the arrow 134. Tilt angle 132 is the
angle between light rays 30 and the plane of the upper surface of
the face plate 80, also indicated as theta. A spring 136 biases the
sapphire sphere 12 to a pre-determined angular orientation.
[0070] A pair of oppositely wound, flat spiral springs (not
illustrated) can provide compliant mounting force needed to hold
the flash LED 10 against the sapphire sphere 12, while at the same
time providing an electrical connection to the PCB 14.
[0071] A larger sapphire sphere could be combined with a plurality
of flash LEDs 10 (not illustrated) mounted in an array on one
hemisphere or a section of the hemisphere. The beam projected from
each flash LED may or may not overlap the beam from an adjacent LED
10.
[0072] RGB arrays of flash LEDs 10 can be employed to allow
multi-colored beams to be produced. While presently only available
in white, it is anticipated that flash LEDs of the type identified
herein will be available that emit light in various colors. The
phosphor coating on the commercially available flash LED 10 can be
removed after SMT to PCB to produce a blue light emitting
device.
[0073] Referring to FIG. 11, the sapphire sphere 12 is supported on
the upper end of a thermal cup 146, whose hollow post is received
in a hole in the PCB 14 that is slidable transversely as indicated
by arrows 140. A spring 142 surrounding the post biases the
sapphire sphere 12 against the walls of the hole in the face plate
148. A wire 144 connects to the flash LED 10 and extends through
the center of the post so that its other end can be connected to
the PCB 14.
[0074] Referring to FIG. 12, an embodiment is illustrated in which
a hemispherical transparent element 150, which may be made of
sapphire, is bonded on top of the flash LED 10 and the PCB 14 via
adhesive 152. A layer of potting compound 154 surrounds the
transparent element 152, further solidifying the position and
attachment of the transparent element 150 to the PCB 14.
[0075] FIGS. 13 and 14 illustrate a commercially available high
intensity LED and lens assembly 160 available in the United States
from Lumileds Lighting US, LLC under the designation LUXEON.RTM.
K2. The LED 162 (FIG. 14) is mounted on top of a small block
portion 164 that supports leads 166. The LED is enclosed in a
somewhat rigid, but still pliant, transparent dome-like cover 168
made of silicone rubber (FIG. 14). A quantity 170 of a transparent
silicone gel encases the LED 162 and is constrained within the
cover 168. A solid frusto-conical lens 172 fits over the cover 168.
A central passage 174 in the lens 162 forms a convex lens 176 which
is used for beam formation.
[0076] Referring to FIGS. 23 and 24, the high intensity LED and
lens assembly 160, without the lens 172, can be placed in a pocket
176 (FIG. 24) formed in the underside of a holder 178 which allows
the cover 168 to project through a central circular aperture. A
sharp blade 179 may then be used to cut off the upper section of
the cover 168, without damaging the underlying LED 162. Other
techniques for safely removing the cover 168 without damaging the
LED 162 will occur to those skilled in the art, such as laser
trimming, water jet cutting, hot wire cutting, and slicing. Once
the upper section of the cover 168 has been removed, the remaining
portion of the LED and lens assembly 160 can be used to construct
the LED and lens assemblies illustrated in FIGS. 15-22.
[0077] The embodiment 180 of FIGS. 15 and 16 utilizes a spherical
sapphire lens element 182 which can be held in position above the
LED 162 the remaining lower section of the cover 168. The remaining
portion of the transparent liquid gel 170 provides a thermal and
optical interface between the LED 162 and the spherical lens
element 182. Referring to FIGS. 17 and 18, the embodiment 184 is
similar to the embodiment of FIGS. 15 and 16, except that in the
embodiment 184 a truncated, spherical sapphire lens element 186 is
utilized. The lens element 186 has an upwardly facing facet 188.
Referring to FIGS. 19 and 20, another embodiment 190 has a
hemispherical sapphire lens element 192 with an upwardly facing
facet 194. Referring to FIGS. 21 and 22, another embodiment 196 has
a hemispherical sapphire lens element 198 with a downwardly facing
facet 200 (FIG. 22).
[0078] The high intensity LED and lens assemblies of FIGS. 15-22
provide enhanced heat dissipation from the upper side of the LED
162. Furthermore, the sapphire lens element in each of these
embodiments provides improved beam patterns, particularly when
these high intensity LED and lens assemblies are immersed in a
fluid such as water. This makes them particularly suited for
underwater applications. The gel 170 must be a thermally
conductive, transparent material with suitable viscosity. However,
this material must not change color in the presence of high
temperatures, such as 180.degree. Centigrade. Silicone gel or
grease has been found to be particularly suited for providing the
thermal and optical interface between the LED 162 and the sapphire
lens element.
[0079] The spherical lens element may also be made of Cubic
Zirconia with a high index of refraction, such as N=2.17. Whereas a
spherical sapphire lens may create some secondary rings of light in
the beam outside of the main central focus, the beam produced by a
spherical lens element made of high index of refraction Cubic
Zirconia is much cleaner. The Cubic Zirconia spherical lens element
produces a high efficiency beam of light with superior control.
More particularly, the use of such a Cubic Zirconia spherical lens
element with a high lumen LED produces a focused convergent beam
that allows one to easily add a molded plastic optic to collimate
or diverge the beam to essentially any beam angle from a narrow
spot to a wide flood.
[0080] Regardless of what material the spherical lens element is
made of, preferably the surface of the spherical lens element is
mounted adjacent the light emitting surface of the LED no further
than twice the longest dimension of the light emitting surface. In
addition, the spherical lens element should have an index of
refraction relative to the light emitted by the high lumen LED
greater than about 1.65. Moreover, excellent results can be
achieved by using a spherical lens element having a diameter D
greater than about three times the longest dimension of the light
emitting surface. The light path optical space between the
spherical lens element and the light emitting surface of the
adjacent high lumen LED is preferably filled with an intervening
optically transparent material selected from the group consisting
of fluid, gel, elastomer or rubber-like material, having an index
of refraction less than about 1.50.
[0081] A high index of refraction lens element material is
particularly suited for underwater lighting applications using LED
light sources, where, for example, N should be greater than about
1.6. When a spherical lens element is submerged in a fluid or
plotting compound its refractive power is greatly reduced and
therefore, the spherical lens element should be made of a material
having a much higher index of refraction. A high index of
refraction material is needed when a rear or lower side of a
spherical lens element is pressed against silicone gel or other
interface material covering the face of the LED.
[0082] Referring to FIG. 25, another embodiment of an LED
illumination device 202 utilizes a LEXEON LED 204 including a block
portion 206. A generally spherical lens element 208 is supported on
top of the remaining section 210 of the dome-shaped cover resulting
from the fabrication process illustrated in FIGS. 23 and 24. The
spherical lens element 208 is preferably made of Cubic Zirconia
having an index of refraction which is greater than about 1.65. A
quantity of an intervening optically transparent incompressible
material 212 joins an upper light emitting surface of the LED 204
with the underside of the spherical lens element 208. This
optically transparent material is preferably selected from the
group consisting of fluid, gel, elastomer or other rubber-like
material, and preferably has an index of refraction of less than
about 1.50. Where the illumination device 202 is fabricated in
accordance with the process illustrated in FIGS. 23 and 24, the
intervening optically transparent material 212 is silicone gel
which is suitable for high temperature applications, i.e.,
180.degree. Centigrade or higher, because it does not discolor.
Furthermore, silicone gel has desirable optical transmission
characteristics. In addition, the intervening optically transparent
material 212 helps draw heat from the LED 204 to the spherical lens
element 208 for dissipation therefrom. The spherical lens element
208 could also be made of Zircon, Sapphire or SF8 Optical Glass.
The spacing or distance Y between the spherical lens element 208
and the light emitting surface of the LED 204 is important in
determining the efficiency in gathering of light from the LED 204.
Preferably, the distance Y is less than twice the longest dimension
of the light emitting surface of the LED 204. In addition, the
diameter of the spherical lens element 208 is also important in
terms of the efficiency of dissemination of light from the LED 204.
Preferably, the diameter should be greater than about three time
the longest dimension of the light emitting surface of the LED 204.
In actual devices constructed with LUXEON LEDs a suitable diameter
is about 9.5 millimeters. A second optical element such as lens 260
(FIG. 32) can be mounted adjacent the spherical lens element 208 to
form a collimated beam. Lens 260 can be molded out of acrylic or
other suitable material. The second optical element can take a wide
variety of configurations, as is well known to those skilled in
optics, depending on the beam pattern desired.
[0083] Referring to FIGS. 26 and 27, another embodiment of an LED
illumination device 214 includes a substrate 216 such as a printed
circuit board, ceramic substrate, polyamide substrate, etc., with
at least one aperture formed therein through which a metal heat
sink 218 extends. The metal heat sink 218 contacts an exposed metal
heat conduction surface 220 on the underside of block portion 206.
One or more metal disc springs 222 are compressed between a lens
retaining plate 211 and a cylindrical collar 224. The collar 224 is
compressed against block portion 206 to maintain the heat
conduction surface 220 in contact with heat sink 218. Any known
means such as machine screws maybe used to load plate 211 against
the disc springs 222. The heat sink 218 may be made of insulating
anodized Aluminum, Copper, Copper alloy or insulated Copper alloy.
The LUXEON K2 LEDs require that heat sink surface 220 be
electrically insulated from LED connections 207 and 209 as well as
any other adjacent LEDs in the array. The insulation on the Copper
alloy may take the form of a diamond film. The disc springs 222 and
collar 224 provide a mechanism that clamps the heat conduction
surface 220 against the heat sink 218 to ensure that the maximum
amount of heat is dissipated from the LED 204. The heat sink 218
may take the form of an anodized Aluminum pin press fit into a
larger planar heat sink 228 through a suitably sized clearance
aperture in the substrate 216. Preferably, the disc springs 222 are
made of Beryllium Copper. The insulation barrier may be formed by
an anodized layer on the sides and bottom of pin 218 allowing the
top of pin 218 that is in contact with surface 220 to be bare
Aluminum for improved heat conduction. Similarly, an insulating
layer on the sides and bottom of a Copper pin may be used and
thermal conduction surface 220 may be soldered to the top of the
Copper pin.
[0084] The substrate 216 (FIGS. 26 and 27) can support multiple
surface mounted LEDs each having their own associated spherical
lens elements 208 and heat sink pins 218 extending through
corresponding apertures in the substrate 216. Each of these
multiple heat sink pins 218 can be press fit into a corresponding
socket in the larger underlying heat sink 228.
[0085] Referring to FIG. 28, another embodiment of an LED
illumination device 230 is specially adapted for immersion in a
body 232 of fresh water or salt water. The spherical lens element
208 is mounted in an hemispherical socket of an acrylic window 234.
The window 234 preferably has an index of refraction greater than
about 1.20. An intervening optically transparent material such as
silicon gel 236 joins the upper surface of the spherical lens
element 208 to the walls of the hemispherical socket in the window
234. Instead of water or seawater 232, the fluid in which the
embodiment 230 is immersed could comprise other optically
transparent liquids such as mineral oil, FluorinertTm fluid
manufactured by 3M, or Novec.TM. fluid manufactured by 3M. The
refraction of light from the LED 204 by the various optical
elements and media is illustrated diagrammatically in FIG. 28 by a
pair of light rays.
[0086] Referring to FIG. 29, another embodiment of an LED
illumination device 238 has a spherical lens element 240 preferably
made of Cubic Zirconia and arranged with a modified Luxeon LED
package 242 fabricated in accordance with FIGS. 23 and 24, along
with a second optical element 243. The second optical element 243
has a negative focal length in order to form the light into a light
beam with a pre-determined pattern as indicated diagrammatically in
FIG. 29 by the light rays. The negative focal length optical
element may have a cylindrical component to change an aspect ratio
of the light beam. Preferably, the spherical lens element 240 has
an index of refraction greater than about 1.80. It is also possible
to have a plurality of different optical elements in front of a
single spherical lens element 240, or in front of a plurality of
spherical lens elements 240 each having their own associated LED
packages 242. The space between lens element 240 and second optical
element 243 may be filled with a transparent fluid, gel, grease or
potting compound (not shown), to improve optical coupling and
provide further refractive control of the output light beam.
[0087] Referring to FIG. 30, another embodiment of an illumination
device 244 is similar to embodiment 238, except that the former
employs a prismatic lens element 246 for bending the light as
indicated diagrammatically in FIG. 30 by the light rays. The
embodiment 244 is particularly suited for use in automobile
headlight assemblies. The light is re-directed from the LED 242 off
of the vertical axis extending through the spherical lens element
240.
[0088] Referring to FIG. 31, another embodiment of an LED
illumination device 248 is designed to provide nearly hidden flush
mount light sources. The spherical lens element 208 preferably has,
again, an index of refraction of greater than about 1.80 to
converge the light to a focus. A hemispherical second optical
element 250 fits on top of the spherical optical element 208.
Planar member 252 is placed above the hemispherical optical element
250 leaving an air gap having an index of refraction of about 1.00.
Light emitted by LED 204 is collected by the spherical lens element
208 and focused by the optical element 250 through a pin hole
aperture 254 in the planar member 252. The embodiment 248 is
particularly suited for ceiling lighting, security lighting,
illuminating wall art, etc. Element 250 serves to prevent total
internal reflect (TIR) of the light exiting element 208. TIR light
trapping inside the spherical lens element 208 can reduce the light
transfer efficiency of the LED lighting system.
[0089] Referring to FIG. 32, another embodiment of an LED
illumination device 256 includes a metal sleeve or spacer 258
between the LED device 242 and the spherical lens element 208. The
inside circular wall of the sleeve 258 is reflectorized with
suitable material (not illustrated) to reduce light loss. A second
optical element 260 in the form of a circular or rectangular
plastic lens has a hemispherical socket in optical contact with the
spherical lens element 208. The second optical element 260 is made
of a suitable material having an index of refraction of greater
than about 1.50.
[0090] FIGS. 33-37 illustrate a thru-hull light assembly 262
utilizing various concepts previously described. A plurality of LED
assemblies 264 (FIG. 37) are mounted behind a transparent window
266 (FIGS. 33 and 36). Each of the LED assemblies 264 is
constructed in accordance with embodiment 226 of FIGS. 26 and 27.
The LED assemblies 264 are mounted within a generally cylindrical
housing 228 (FIGS. 35 and 36). The window 266 is sealed to the
housing 228 via O-ring 270. Housing 228 and window 266 are mounted
inside and held by flange ring 268. Housing 228 is in turn
supported on threaded shaft 278 for external mounting on the hull
273 of the vessel. A central drum of the housing 228, as well as
threaded shaft 278, passes through a small hole in the hull of the
vessel. A nut 276 can be tightened on a threaded shaft 278 to press
washers 280, 282, 284 and 286 against the inside surface of the
vessel hull. The threaded shaft 278 is forced through the small
hole in the vessel hull to press hull insulator 272 (FIGS. 34-36)
against the external surface and the small hole in the vessel hull.
The hull insulator 272 serves to both thermally and electrically
isolate light assembly 262 from the vessel hull. The threaded shaft
278 is sealed into the drum on cylindrical housing 228 and provides
a water-tight pathway for electrical conductors 289 that supply
power to the LED assemblies 264. Screws 213 (FIG. 35) hold plate
211 against housing 228.
[0091] The thru-hull illumination device 262 (FIGS. 33-37) has the
advantage of being low profile, permitting it to be mounted to the
outside surface of the vessel hull without creating undo drag. The
LED assemblies 264 provide substantial underwater lighting for
purposes of photography, observing submerged obstacles, attracting
fish, aesthetic qualities and so forth. The LED assemblies 264 may
produce all white light, or they may be red, green and blue, which,
in various combinations of energization, can produce a beam of
light of a desired color.
[0092] FIGS. 38 and 39 illustrate a preferred embodiment of an LED
illumination device 288 which is similar to the embodiment 202 of
FIG. 25, except that in the former a rod lens element 290 is used
in place of the spherical lens element 208. The rod lens element
290 has a curved lower surface 292 (FIGS. 39) which gathers light
from the LED device 242. The rod lens element 290 has a flat upper
surface 294.
[0093] Referring to FIGS. 40 and 41, another embodiment of an
illuminating device 296 is similar to the embodiment 288 of FIGS.
38 and 39, except that the former utilizes a rod lens element 298
with curved upper and lower surfaces 300 and 302.
[0094] While various embodiments of improved LED illumination
devices have been described in detail, it will be apparent to those
skilled in the art that the invention can be modified in both
arrangement and detail. For example, the lens element that directly
gathers light from the high intensity LED 204 can have varying
shapes and configurations; however, preferably the underside
surface is round, ellipsoid, parabolic or some other curved surface
for gathering the light. As another example, the embodiments of
FIGS. 1-12 and 15-22 could have optical elements adjacent the LEDs
that are made of Sapphire, Cubic Zirconia, Zircon or SF8 optical
glass. The heat sinks that extend through the apertures in the PCB
substrate can be made by any known means. For example, rather than
being pressed into place, these can be raised machined or formed
features in a solid metal plate. TIR in a Cubic Zirconia spherical
lens or ball can be reduced or eliminated by coating the surfaces
with a material with an index of refraction intermediate between,
for example, air with an index of refraction of 1.0 and the Cubic
Zirconia at 2.17. E-Beam Quartz is an example of such a coating.
LUXEON K2 LEDs are available in green, cyan blue and royal blue
colors. Various proportions of each color may be used to maximize
the attraction of marine life. Therefore, the protection afforded
the invention should only be limited in accordance with the
following claims.
* * * * *