U.S. patent application number 14/243931 was filed with the patent office on 2015-10-08 for wide angle optical system for led array.
This patent application is currently assigned to WHELEN ENGINEERING COMPANY, INC.. The applicant listed for this patent is WHELEN ENGINEERING COMPANY, INC.. Invention is credited to Kyle Shimoda.
Application Number | 20150285462 14/243931 |
Document ID | / |
Family ID | 52807571 |
Filed Date | 2015-10-08 |
United States Patent
Application |
20150285462 |
Kind Code |
A1 |
Shimoda; Kyle |
October 8, 2015 |
WIDE ANGLE OPTICAL SYSTEM FOR LED ARRAY
Abstract
An optical system includes a lens and reflector configured to
form a wide angle beam from light emitted from an array of LEDs by
modifying only the component of emitted light that diverges from a
reference plane. A central portion of the lens collimates emitted
LED light relative to the reference plane containing the optical
axes of the LEDs. A peripheral portion of the lens re-directs
emitted LED light into an orientation perpendicular to the
reference plane. The reflector surrounds the periphery of the lens
and re-directs light from the peripheral portion of the lens into a
direction parallel with the reference plane. The linear array of
LEDs may include sub arrays projecting away from a support plane to
enhance visibility of a resulting light signal from vantage points
close to or aligned with the support plane.
Inventors: |
Shimoda; Kyle; (Middletown,
CT) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
WHELEN ENGINEERING COMPANY, INC. |
CHESTER |
CT |
US |
|
|
Assignee: |
WHELEN ENGINEERING COMPANY,
INC.
CHESTER
CT
|
Family ID: |
52807571 |
Appl. No.: |
14/243931 |
Filed: |
April 3, 2014 |
Current U.S.
Class: |
362/218 |
Current CPC
Class: |
B60Q 1/2611 20130101;
F21V 13/04 20130101; F21W 2111/00 20130101; F21S 43/37 20180101;
G02B 19/0028 20130101; F21S 43/195 20180101; F21S 43/14 20180101;
F21S 43/40 20180101; F21Y 2115/10 20160801; B60Q 1/2615 20130101;
B60Q 1/2696 20130101; G02B 19/0066 20130101; B60Q 1/00 20130101;
F21S 45/50 20180101; B60Q 1/24 20130101; F21S 43/27 20180101; F21S
43/31 20180101; F21S 4/28 20160101; F21V 7/005 20130101; F21S 45/47
20180101; F21V 5/048 20130101; F21S 43/26 20180101; B60Q 1/52
20130101; F21Y 2103/10 20160801; F21S 43/15 20180101 |
International
Class: |
F21V 13/04 20060101
F21V013/04; F21V 5/04 20060101 F21V005/04; F21V 7/00 20060101
F21V007/00; F21S 4/00 20060101 F21S004/00 |
Claims
1. An LED light assembly comprising: a first support parallel with
a first plane, said support including a heat sink and a PC board to
which are mounted a first plurality of LEDs, said first plurality
of LEDs arranged along a first linear focal axis parallel with said
first plane and included in a second plane perpendicular to said
first plane, each of said first plurality of LEDs emitting light in
a hemispherical pattern directed away from said first plane, each
of said LEDs having an optical axis in said second plane and
emitting narrow angle light at angles less than a first angle with
respect to said second plane and wide angle light at angles greater
than said first angle with respect to said second plane; an optical
element arranged to collect light from said first plurality of
LEDs, said optical element comprising first, second and third light
entry surfaces and first, second and third light emission surfaces,
said first and second light entry surfaces and first and second
light emission surfaces separated by said second plane and said
third light entry surface and said third light emission surface are
bisected by said second plane, said first and second light entry
surfaces configured to cooperate with said first and second light
emission surfaces, respectively, to re-direct wide angle light
emitted from said first plurality of LEDs into a trajectory
substantially parallel with said first plane, and said third light
entry surface cooperates with said third light emission surface to
re-direct narrow angle light emitted from said first plurality if
LEDs into a trajectory substantially parallel with said second
plane; and a reflector having first and second reflecting surfaces
arranged to reflect wide angle light emitted from said first and
second light emission surfaces, respectively, into a trajectory
substantially parallel with said second plane, said first and
second reflecting surfaces separated by said second plane and
spaced apart from said first and second light emission surfaces,
wherein said first linear focal axis extends between the optical
axes of LEDs defining longitudinal ends of said first plurality of
LEDs, said first, second and third light entry surfaces and said
first, second and third light emission surfaces are defined by a
cross sectional shape of said optical element projected along said
first linear focal axis.
2. The LED light assembly of claim 1, wherein an end of said
optical element is defined by the cross sectional shape of said
optical element rotated approximately 180.degree. about the optical
axis of an LED defining a longitudinal end of said first plurality
of LEDs, resulting in end light entry and end light emission
surfaces that are surfaces of rotation extending between said first
and second light entry and said first and second light emission
surfaces.
3. The LED light assembly of claim 1, wherein said first and second
reflecting surfaces are defined by a sectional shape of said first
and second reflecting surfaces projected along said first linear
focal axis.
4. The LED light assembly of claim 1, comprising an end reflecting
surface defined by the sectional shape of said first and second
reflecting surfaces rotated approximately 180.degree. about the
focal axis of an LED defining a longitudinal end of said first
plurality of LEDs, said end reflecting surface being a surface of
rotation extending between said first and second reflecting
surfaces.
5. The LED light assembly of claim 1, wherein said first and second
reflecting surfaces each comprise a plurality of reflecting
surfaces separated by a separator surface substantially parallel
with said first plane so that said plurality of reflecting surfaces
are laterally separated from each other by said separator surface
portion.
6. The LED light assembly of claim 1, comprising at least one
support surface not parallel with said first plane and a second
plurality of LEDs on said support surface and arranged along a
second linear focal axis within said second plane and not parallel
with said first linear focal axis, said optical element including a
second segment with first second and third light entry surfaces and
first, second and third light emission surfaces, said first and
second light entry surfaces separated by said second plane and said
third light entry surface and said third light emission surface are
bisected by said second plane, said first and second light entry
surfaces configured to cooperate with said first and second light
emission surfaces, respectively, to re-direct wide angle light
emitted from said second plurality of LEDs into a trajectory
substantially parallel with said support surface, and said third
light entry surface cooperates with said third light emission
surface to re-direct narrow angle light emitted from said first
plurality if LEDs into a trajectory substantially parallel with
said second plane; and a reflector second segment having first and
second reflecting surfaces arranged to reflect wide angle light
emitted from said second plurality of LEDs through said first and
second light emission surfaces, respectively, into a trajectory
substantially parallel with said second plane, said reflector
second segment first and second reflecting surfaces separated by
said second plane and spaced apart from said optical element second
segment first and second light emission surfaces, wherein said
second linear focal axis extends between the optical axes of LEDs
defining longitudinal ends of said second plurality of LEDs, said
optical element second segment first, second and third light entry
surfaces and said first, second and third light emission surfaces
are defined by a cross sectional shape of said optical element
projected along said second linear focal axis.
7. The LED light assembly of claim 6, wherein said reflector second
segment first and second reflecting surfaces are defined by a
sectional shape of said reflector second segment first and second
reflecting surfaces projected along said second linear focal
axis.
8. The LED light assembly of claim 1, comprising second and third
support surfaces not parallel with said first plane and second and
third pluralities of LEDs on said second and third support surfaces
and arranged along second and third linear focal axes within said
second plane and not parallel with said first linear focal axis,
said optical element including second and third segments each with
first, second and third light entry surfaces and first, second and
third light emission surfaces, said first and second light entry
surfaces separated by said second plane, said third light entry
surface and said third light emission surface are bisected by said
second plane, said first and second light entry surfaces configured
to cooperate with said first and second light emission surfaces,
respectively, to re-direct wide angle light emitted from said
second plurality of LEDs into a trajectory substantially parallel
with said second and third support surfaces, respectively, and said
third light entry surface cooperates with said third light emission
surface to re-direct narrow angle light emitted from said first
plurality of LEDs into a trajectory substantially parallel with
said second plane; and reflector second and third segments having
first and second reflecting surfaces arranged to reflect wide angle
light emitted from said second and third plurality of LEDs through
said second and third optical element first and second light
emission surfaces, respectively, into a trajectory substantially
parallel with said second plane, said reflector second and third
segment first and second reflecting surfaces separated by said
second plane and spaced apart from said optical element second and
third segment first and second light emission surfaces, wherein
said second and third linear focal axes are not parallel with each
other and extend between the optical axes of LEDs defining
longitudinal ends of said second and third plurality of LEDs,
respectively, said optical element second and third segment first,
second and third light entry surfaces and said first, second and
third light emission surfaces defined by a cross sectional shape of
said optical element second and third segments projected along said
second and third linear focal axes, respectively.
Description
BACKGROUND
[0001] The present invention relates generally to optical systems
for distributing light from a light source and more particularly to
an optical system for combining the light output of a plurality of
LEDs into a wide angle beam.
[0002] Commercially available LED's have characteristic spatial
radiation patterns with respect to an optical axis which passes
through the light emitting die. A common characteristic of all of
LED radiation patterns is that light is emitted from one side of a
plane containing the light emitting die in a pattern surrounding
the LED optical axis, which is perpendicular to the plane. Light
generated by an LED is radiated within a hemisphere centered on the
optical axis. The distribution of light radiation within this
hemisphere is determined by the shape and optical properties of the
lens (if any) covering the light emitting die of the LED. Thus,
LED's can be described as "directional" light sources, since all of
the light they generate is emitted from one side of the device.
[0003] When designing light sources for a particular purpose, it is
important to maximize efficiency by ensuring that substantially all
of the generated light is arranged in a pattern or field of
illumination dictated by the end use of the device into which the
light source is incorporated. The somewhat limited overall light
output of individual LEDs frequently necessitates that several
discrete devices be cooperatively employed to meet a particular
photometric requirement. Employing LEDs in compact arrays
additionally imposes cooling, i.e., "heat sinking", requirements to
prevent heat from accumulating and damaging the LEDs.
[0004] The use of LED's in warning and signaling lights is well
known. Older models of LED's produced limited quantities of light
over a relatively narrow viewing angle centered on an optical axis
of the LED. These LED's were typically massed in compact arrays to
fill the given illuminated area and provide the necessary light
output. More recently developed, high output LED's produce
significantly greater luminous flux per component, permitting fewer
LED's to produce the luminous flux required for many warning and
signaling applications. It is known to arrange a small number of
high-output LED's in a light fixture and provide each high-output
LED with an internally reflecting collimating lens such as that
shown in FIG. 2. The collimating lens organizes light from the LED
into a collimated beam centered on the LED optical axis. Such an
arrangement typically does not fill the light fixture, resulting in
an undesirable appearance consisting of bright spots arranged
against an unlit background. Light-spreading optical features on
the outside lens/cover are sometimes employed to improve the
appearance of the light fixture.
[0005] For purposes of this application, light emitted from an LED
can be described as "narrow angle" light emitted at an angle of
less than about 35.degree. from the optical axis and "wide angle"
light emitted at an angle of more than about 35.degree. from the
optical axis as shown in FIG. 1. The initial "emitted" trajectory
of wide angle and narrow angle light may necessitate manipulation
by different portions of a reflector and/or optical element to
provide the desired illumination pattern.
[0006] This application will discuss optical arrangements for
modifying the emitted trajectory of light from an LED with respect
to a reference line or plane. For purposes of this application,
"collimated" means "re-directed into a trajectory substantially
parallel with a reference line or plane." Substantially parallel
refers to a trajectory within 5.degree. of parallel with the
reference line or plane. When discussing collimation of light with
respect to a plane, it will be understood that the component of the
emitted trajectory divergent from the reference plane is modified
to bring the divergent component of the trajectory within 5.degree.
of parallel with the reference plane, while the component of
emitted trajectory parallel with the reference plane is not
modified. For LEDs mounted to a vertical surface, light is emitted
in a hemispherical pattern centered on the optical axes of the
LEDs, which are perpendicular to the vertical surface, i.e., the
optical axis of each of the LEDs is horizontal. If the LEDs are
mounted in a row, the optical axes are included in the same
horizontal plane, which is typically the horizontal reference
plane. In this situation, "vertically collimated" means that light
which would diverge upwardly or downwardly from the horizontal
reference plane (containing the LED optical axes) is re-directed
into a direction substantially parallel to the horizontal plane.
Assuming no other obstruction or change of direction, vertically
collimated light from each LED will be dispersed across an arc of
approximately 180.degree. in a horizontal direction. The light of
adjacent LEDs overlaps to create a horizontal beam having a peak
intensity many times the peak intensity of any one of the LEDs.
[0007] FIG. 2 illustrates a prior art collimator of a configuration
frequently employed in conjunction with LED light sources. Light
from an LED positioned in a cavity defined by the collimator is
organized into a collimated beam aligned with the optical axis of
the LED. The known internally reflecting collimator for an LED is a
molded solid of light transmissive plastic such as acrylic or
polycarbonate. The radial periphery of the collimator is defined by
an aspheric internal reflecting surface flaring upwardly and
outwardly to a substantially planar light emission surface. The
bottom of the collimator includes a cavity centered over the LED
optical axis. The cavity is defined by a substantially cylindrical
side-wall and an aspheric upper surface. The aspheric upper surface
is configured to refract light emitted at small angles relative to
the LED optical axis to a direction parallel with the LED optical
axis. The shape of the aspheric upper surface is calculated from
the refractive properties of the air/solid interface, the position
of the LED point of light emission relative to the surface, the
configuration of the surface through which the light will be
emitted, and the desired direction of light emission, e.g.,
parallel to the LED optical axis. The mathematical relationship
between the angle of incidence of a light ray to a surface and the
angle of the refracted ray to the surface is governed by Snell's
Law: "The refracted ray lies in the plane of incidence, and the
sine of the angle of refraction bears a constant ratio to the sine
of the angle of incidence." (sin .theta./sin .theta.=constant,
where is the angle of incidence and .theta.' is the angle of
refraction)
[0008] For any particular point on the substantially cylindrical
side-wall, the path of light refracted into the collimator can be
calculated using Snell's law. The shape of the peripheral aspheric
internal reflecting surface is calculated from the path of light
refracted by the substantially cylindrical side-wall surface, the
configuration of the surface through which light will be emitted,
and the desired direction of light emission, e.g., parallel to the
LED optical axis. The resulting aspheric internal reflecting
surface redirects light incident upon it in a direction parallel to
the optical axis of the LED.
[0009] The result is that substantially all of the light emitted
from the LED is redirected parallel to the optical axis of the LED
to form a collimated beam. This arrangement efficiently gathers
light from the LED and redirects that light into a direction of
intended light emission. Unless the light is somehow spread, the
light from each LED appears to the viewer as a bright spot the size
and shape of the collimator. It is typically less efficient to
collimate light and then re-direct the collimated light into a
desired pattern than it is to modify only those components of the
emitted trajectory that do not contribute to the desired emission
pattern, while leaving desirable components of the emitted
trajectory undisturbed.
SUMMARY
[0010] An embodiment of a disclosed optical system employs an
optical element in combination with a reflector to produce a wide
angle beam having enhanced surface area from light emitted from a
plurality of LEDs. This arrangement expands the illuminated portion
of a light assembly incorporating the disclosed optical system.
Although not limited to such a use, the disclosed optical system
may be employed in a warning light fixed to a substantially
vertical surface of an emergency vehicle. In such an orientation,
the plurality of LEDs may be mounted to a support that extends
outwardly from the vertical surface to enhance visibility from
positions close to parallel with the surface to which the warning
light is attached. For example, if the warning light is mounted to
the side panel of the box of an ambulance, at least a portion of
the LEDs may be mounted to a support that projects away from the
side panel of the ambulance.
[0011] The illustrated embodiment of the disclosed optical system
can be described with respect to a first plane parallel with the
vehicle panel and a second plane containing the optical axes of a
plurality of LEDs arranged along a line. Each of the LEDs has an
optical axis perpendicular to a support surface to which the LED is
mounted, so the optical axes of the LEDs in each array are
contained in a second plane perpendicular to the first plane. A
single row of LEDs arranged along a line may be referred to as a
linear array. In the disclosed exemplary embodiment, the plane
containing the optical axes of the LEDs is a horizontal plane.
Those skilled in the art will understand that light generated from
such an array of LEDs will have a range of emitted trajectories,
each with a directional component parallel with the horizontal
plane and a directional component divergent (up or down) from the
horizontal plane. An illustrated embodiment of the disclosed
optical system employs an optical element (lens) configured to
re-direct specific portions of light from the linear array in a
pre-determined way. A central portion of the optical element is
configured to re-direct light with an emitted trajectory having a
relatively small divergent directional component (light emitted at
angles relatively close to the horizontal plane) into trajectories
substantially parallel with the horizontal plane. This portion of
the optical element is bisected by the horizontal plane containing
the optical axes of the LEDs. The periphery of the optical element
(surrounding the central portion) are configured to re-direct light
with an emitted trajectory having a relatively large divergent
directional component (light emitted at large angles relative to
the horizontal plane) into trajectories substantially perpendicular
to the horizontal plane.
[0012] The illustrated optical element is defined by light entry
and light emission surfaces configured to cooperatively re-direct
light emitted from the linear array of LEDs. The center of the
optical element handles light with emitted trajectories with a
divergent directional component below a pre-determined angle, while
the periphery of the optical element handles light with emitted
trajectories with a divergent directional component above the
pre-determined angle. Together, the light entry surfaces define a
pocket that fits over the linear array of LEDs. The light emission
surfaces define the top and side surfaces of the optical element.
The light entry and light emission surfaces are formed by
projecting a sectional shape of the optical element along a linear
focal axis extending between the area of light emission (die) of
the LED at each end of the linear array. An end of the optical
element may be a surface of rotation defined by rotating the
sectional shape of the optical element about the optical axis of an
LED at and end of the linear array.
[0013] The illustrated embodiment of the disclosed optical system
employs a reflector configured to surround the periphery of the
optical element and re-direct light emitted from the peripheral
light emissions surfaces. Light is emitted from the peripheral
light emission surfaces perpendicular to light emitted from the
central portion of the optical element. The reflector includes
reflecting surfaces arranged to re-direct light emitted from the
peripheral surfaces of the optical element into a direction
generally parallel with the second plane. The reflecting surfaces
are spaced apart from the periphery of the optical element, giving
added breadth and surface area to the light emission pattern from
the disclosed optical system.
[0014] The disclosed optical system is described in the context of
a particular warning light assembly intended for mounting to the
vertical surface of an emergency vehicle. The illustrated warning
light assembly includes LED arrays arranged to produce a warning
light signal and another LED array configured to provide area
illumination around the emergency vehicle. The LED arrays producing
the warning light signal are configured to meet the requirements of
SAE J845, J595, Class 1, California Title 13 or similar industry
standards relevant to zonal optical warning devices. The
illustrated warning light assembly employs the disclosed optical
system to generate a warning light signal visible over an arc of
approximately 180.degree. in a horizontal plane. A support projects
away from the base of the warning light assembly (and away from the
side of the vehicle) to enhance visibility of the resulting warning
light signal from vantage points close to parallel with the vehicle
panel to which the illustrated warning light assembly is attached.
One example of such a vantage point is a motorist or pedestrian in
front or behind an emergency vehicle path of travel when the
warning light assembly is mounted to one of the side panels of the
vehicle.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 is a representation of an LED showing a lambertian
light emission pattern with respect to a reference plane P1;
[0016] FIG. 2 is a sectional view through a prior art total
internal reflecting (TIR) optic commonly used with LED light
sources;
[0017] FIG. 3 is a perspective view (from below) of a warning light
assembly incorporating an embodiment of the disclosed optical
system;
[0018] FIG. 4 is a front plan view of the warning light assembly of
FIG. 3 with the outer lens removed to show the internal
components;
[0019] FIG. 5 is a longitudinal sectional view through the warning
light assembly of FIG. 4, taken along line 5-5 thereof;
[0020] FIG. 6 is a vertical sectional view through the warning
light assembly of FIG. 4, taken along line 6-6 thereof;
[0021] FIG. 7 is a perspective view of the optical element and
reflector of an embodiment of the disclosed optical system;
[0022] FIG. 8 is a longitudinal sectional view through the optical
element and reflector of FIG. 7;
[0023] FIG. 9 is a partial vertical sectional view through an
embodiment of the disclosed optical system in the context of the
warning light assembly of FIG. 3, with extraneous components
omitted for clarity; and
[0024] FIG. 10 illustrates the support base, main PC board, warning
array bracket, and warning array PC boards of an illustrated
embodiment of the warning light assembly for use in conjunction
with the disclosed optical system.
DETAILED DESCRIPTION OF THE DISCLOSED EMBODIMENTS
[0025] An embodiment of the disclosed optical system will now be
described with reference to FIGS. 3-10. FIG. 3 illustrates a
warning light assembly 100 incorporating an embodiment of the
disclosed optical system designated by reference number 10. The
warning light assembly also incorporates a second LED array and
optical system 200 configured to produce area and ground
illumination adjacent an emergency vehicle to which the warning
light assembly 100 is mounted. The warning light assembly 100 is
configured to be mounted to a vertical body panel of an emergency
vehicle (not shown) where the warning light assembly 10 generates a
warning light signal while the second LED array and optical system
200 provide ground and area illumination. Each of these functions
are required by state, federal, and industry standards applicable
to emergency vehicles such as fire trucks and ambulances. In the
past, warning and area illumination functions were provided by
separate light assemblies mounted at various points on the vehicle
body. Combining the warning and area illumination functions into a
single warning light assembly should reduce the cost and complexity
of installing such systems when constructing an emergency
vehicle.
[0026] As shown in FIGS. 4 and 5, the warning light assembly 100
includes a heat sink 110, a bezel 112, and a sheet metal base 114,
secured to the heat sink 110. A lens 116 (shown only in FIG. 3)
mates with a frame 122 to form an enclosure surrounding the
internal components of the warning light assembly 100. A rubber
boot 120 extends from the rear of the warning light assembly 100 to
seal against the body panel and prevent moisture from passing
through any openings in the body panel used to deliver electrical
wiring to the warning light assembly.
[0027] The disclosed optical system 10 is used in conjunction with
an array 12 of LEDs 14. As best shown in FIG. 10, the array 12 of
LEDs 14 includes six sub-arrays 16 of LEDs 14. Some of the
sub-arrays 16 are mounted to a main PC board 18, while some of the
sub-arrays 16 are mounted to a sheet metal bracket 20 that projects
away from the main PC board 18. The sub-arrays arranged on the
bracket 20 are mounted to a PC board assembly 22 including two
rigid boards connected by a flexible connector. Each PC board
assembly 22 includes an electrical connector 23 to deliver
electrical power to the sub-arrays 16. Each of the sub-arrays 16
may be energized independently of the other sub-arrays, but most
commonly all the sub-arrays 16 will be energized at the same time
to produce warning light signals. The main PC board 18 is secured
in thermal contact with a sheet metal base 114. The main PC board
18 defines openings 24 that allow the bracket 20 to be secured in
thermal contact with the sheet metal base 114. The sheet metal base
114 is mounted in thermal contact with the heat sink 110, as shown
in FIGS. 5 and 6. Together, the PC boards 18, 22, sheet metal
bracket 20, sheet metal base 110 and heat sink 114 provide a
thermal pathway for heat generated by the LEDs 14. When mounted to
a vertical body panel (not shown), the heat sink 114 fins are
vertically oriented and aligned with openings 118 at the top and
bottom of the bezel 112 to promote air flow to distribute heat from
the warning light assembly 100 to the ambient environment.
[0028] As best shown in FIG. 5, the illustrated embodiment of the
disclosed optical system 10 includes an optical element (lens) 30
and a reflector 40 configured to fit over the LED array 12,
supported by the bracket 20. Each of the optical element 30 and
reflector 40 are segmented, with each segment corresponding to a
sub-array 16 of LEDs 14. Generally, the relationship between each
segment of the optical element 30 and the reflector 40 to each
sub-array 16 is the same, so the relationship will only be
described once. The bracket 20 supports four of the sub-arrays 16
in a position extending away from the base 114. As shown in FIG. 8,
the disclosed bracket 20 supports sub-arrays 16 at angle A of
20.degree. and angle B of 70.degree. with respect to the base 116,
which is parallel with a first plane P1. The bracket 20 extends the
LED array 12 away from the base 114 and directs the light from each
sub-array 16 to produce a highly conspicuous warning light signal
extending over an arc of 180.degree.. The extended position of the
bracket 20, sub-arrays 16, optical element 30 and reflector 40
enhance visibility of the resulting light signal from vantage
points close to or aligned with the plane of the vehicle panel to
which the warning light assembly is attached.
[0029] FIG. 9 is an enlarged cross sectional view through a portion
of the warning light assembly 100, showing the optical system 10 in
functional relation to the main PC board 18, sheet metal base 114
and heat sink 110. This sectional view is taken at a position
roughly corresponding to line 6-6 of FIG. 4. LED 14 is mounted to
the main PC board 18 and the optical element 30 is aligned with
plane P1 at this position. The optical element 30 is defined by
light entry surfaces 31, 32, and 33 and light emission surfaces 34,
35, and 36. Light entry surfaces 31, 32, and 33 define a pocket 37
that receives the upper portion of the LED 14, situating the light
emitting die of the LED 14 at a focus of the optical system 10. The
surfaces defining each segment of the optical element 30 are
defined by projecting the sectional shape of the optical element
along the linear focal axis 17 of the LED sub-array 16. The linear
focal axis 17 of each sub-array extends through the light emitting
die at the center of each LED 14. The optical system 10 is
configured to combine the light from the LED array 12 into a wide
angle, vertically collimated beam. In FIG. 9, plane P1 generally
corresponds to a vertical direction and plane P2 generally
corresponds to a horizontal direction.
[0030] The light entry and light emission surfaces of the optical
element 30 are configured to cooperate to re-direct light generated
by the LED array 12 from an emitted trajectory to a pre-determined
direction. In the illustrated embodiment, light entry surface 31 is
configured to cooperate with light emission surface 34 to re-direct
light emitted to one side of plane P2 at an angle greater than C,
which in the illustrated embodiment is approximately 38.degree..
The specific configuration of each surface is dependent upon the
configuration of the paired surface and the desired direction of
emission from the optical element. Any number of surface
configuration combinations may be employed to achieve the desired
re-direction. In the disclosed embodiment, light entry surface 31
is an aspheric surface, while light emission surface is an
elliptical surface. Light entry surface 32 and light emission
surface 35 have the same relationships and configurations as light
entry surface 31 and light emission surface 34 and are mirror
images thereof.
[0031] The center of the optical element 30 is defined by light
entry surface 33 and light emission surface 36, which cooperate to
re-direct light from an emitted trajectory into a direction
generally parallel with plane P2, as shown in FIG. 9. Again, the
surfaces are configured to achieve a pre-determined re-direction of
light from the LED array 12, with any number of surface
configurations being compatible with the disclosed optical element
30 and its function. In the disclosed embodiment, light entry
surface 33 is an aspheric surface and light emission surface 36 is
an elliptical surface. Surfaces 33 and 36 are projected along the
linear focal axis 17 of the sub-array 16 until the surfaces meet
the corresponding surfaces of the next segment of the optical
element 30. In this manner, the relationship of the optical element
30 to each sub-array 16 is consistent along the length of the LED
array 12 and the disclosed optical system.
[0032] The longitudinal ends 38 of the optical element 30 are
defined by the sectional shape of the optical element 30 rotated
about the optical axis AR1 of the LED 14 at each longitudinal end
of the LED array 12. The reflector 40 is similarly rotated about
the optical axis of these LEDs to form a shape complementary to the
rotated shape of the ends 38 of the optical element 30. The optical
element 30 and reflector 40 both take a 110.degree. turn at the top
of the optical system 10, as shown in FIGS. 7 and 8. The light
entry and light emission surfaces defining the sectional shape of
the optical element 30 are rotated about an axis AR2, which forms
the curved portion 39 of the optical element 30. The curved portion
39 blends light from one side of the LED array 12 with light from
the other side to form the desired wide angle beam. Blending light
from both sides of the LED array 12 also aids in avoiding an
undesirable dark spot in the middle of the wide angle beam. Axes
AR1 and AR2 are substantially perpendicular with each other.
[0033] Reflector 40 includes reflecting surfaces 42, 44 spaced
apart from the light emission surfaces 34, 35 of the optical
element 30. Reflecting surfaces 42, 44 are configured to re-direct
light from the optical element 30 into a direction parallel with a
horizontal plane illustrated in the Figures as P2. Reflecting
surfaces 42, 44 are separated by a step 46 that serves to shorten
the height of the reflector and expand the lateral size of the
emitted light signal. The shape and orientation of the reflecting
surfaces 42, 44 are determined by the direction of light incident
upon them and the desired direction of light emission from the
optical system. In the illustrated embodiment, light leaves the
optical element light emission surfaces 34, 35 in a direction
generally parallel with plane P1 as shown in FIG. 9. The reflecting
surfaces 42, 44 are planar surfaces oriented at an angle of
45.degree. relative to the incident light and plane P1, resulting
in light emitted from the optical system 10 in the desired
direction, which is perpendicular to plane P1 and generally
parallel with plane P2. Each end of the reflector is rotated about
axis AR1 to maintain the relationship between the light emission
surface of the optical element 30 and the reflecting surfaces 42,
44. Reflecting surfaces 42, 44 and step 46 are also rotated about
axis AR2 to maintain the relationship with the optical element 30
light emission surfaces at the top of the optical system 10.
[0034] The illustrated embodiment of the disclosed optical system
10 is configured to modify the component of light emitted from the
LED array 12 that diverges from the desired horizontal beam, e.g.,
light that is emitted in directions up or down with respect to
horizontal reference plane P2. The illustrated embodiment of the
disclosed optical system 10 is configured to maintain the direction
of emitted light that reinforces the desired light emission
pattern, e.g., directional components parallel with horizontal
plane P2. The illustrated embodiment spaces the reflecting surfaces
42, 44 laterally from the LED array 12 to generate a horizontal
beam having a large surface area to enhance visibility and cover
additional area of the warning light assembly 100.
[0035] The disclosed optical system 10 has been described in the
context of a specific application, but those skilled in the art
will recognize other uses. The disclosed optical system 10 has been
described with specific surface configurations, but is not limited
to those specific shapes and those skilled in the art will
recognize simple modifications to achieve the same or similar
functionality. The description is by way of illustration and not
limitation.
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