U.S. patent application number 15/890806 was filed with the patent office on 2019-05-16 for low profile multi-lens tir.
This patent application is currently assigned to FRAEN CORPORATION. The applicant listed for this patent is FRAEN CORPORATION. Invention is credited to Brien Housand, James Preston, Michael Zollers.
Application Number | 20190145605 15/890806 |
Document ID | / |
Family ID | 48985840 |
Filed Date | 2019-05-16 |
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United States Patent
Application |
20190145605 |
Kind Code |
A9 |
Preston; James ; et
al. |
May 16, 2019 |
LOW PROFILE MULTI-LENS TIR
Abstract
In one aspect, an optical lens assembly (herein referred to also
as an optic) is provided that comprises a plurality of lenses (or
lens segments) adapted to receive light from a light source, each
of said lenses (or lens segments) having an input surface and an
output surface and a lateral surface extending between the input
and output surfaces. The lenses are arranged relative to one
another and positioned relative to the light source such that each
of the lenses receives at its input surface a different portion of
light emitted by the source, e.g., each lens receives at its input
surface light emitted by the source into an angular subtense (solid
angle) different than an angular subtense associated with another
lens. Each lens (or lens segment) guides at least a portion of the
received light to its output surface via reflection, e.g., via
total internal reflection (TIR).
Inventors: |
Preston; James; (Malden,
MA) ; Housand; Brien; (Worcester, MA) ;
Zollers; Michael; (Burlington, MA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
FRAEN CORPORATION |
Reading |
MA |
US |
|
|
Assignee: |
FRAEN CORPORATION
Reading
MA
|
Prior
Publication: |
|
Document Identifier |
Publication Date |
|
US 20180195686 A1 |
July 12, 2018 |
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|
Family ID: |
48985840 |
Appl. No.: |
15/890806 |
Filed: |
February 7, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13955839 |
Jul 31, 2013 |
9890926 |
|
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15890806 |
|
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61809631 |
Apr 8, 2013 |
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61678781 |
Aug 2, 2012 |
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Current U.S.
Class: |
362/296.01 ;
362/309; 362/311.01; 362/327 |
Current CPC
Class: |
G02B 5/09 20130101; F21V
5/008 20130101; F21V 5/004 20130101; F21V 17/002 20130101; F21V
5/00 20130101; G02B 19/0019 20130101; G02B 19/0061 20130101; F21V
7/0091 20130101; G02B 19/0028 20130101; F21V 13/04 20130101; G02B
19/0023 20130101 |
International
Class: |
F21V 7/00 20060101
F21V007/00; G02B 19/00 20060101 G02B019/00; G02B 5/09 20060101
G02B005/09; F21V 5/00 20180101 F21V005/00; F21V 13/04 20060101
F21V013/04; F21V 17/00 20060101 F21V017/00 |
Claims
1. An optical lens assembly, comprising a plurality of lenses
adapted to receive light from a light source, each of said lenses
having an input surface and an output surface and a lateral surface
extending between said input surface and output surface, said
lenses being arranged relative to one another such that each of the
lenses receives at its input surface light emitted by the source
into an angular subtense different than a respective angular
subtense associated with another lens, wherein each of said lenses
guides at least a portion of the received light to its output
surface via total internal reflection at the lateral surface
thereof.
2. The optical lens assembly of claim 1, wherein at least one of
said lenses is configured to collimate at least a portion of the
light it receives from the light source.
3. The optical lens assembly of claim 1, wherein the lateral
surfaces of at least two adjacent lenses of said lens assembly are
separated from one another by an airgap.
4. The optical lens assembly of claim 1, wherein said lenses are
configured to collectively receive at least about 80% of the light
emitted by said light source.
5. The optical lens assembly of claim 1, wherein said lenses are
configured to collectively receive at least about 90% of the light
emitted by said light source.
6. The optical lens assembly of claim 1, wherein said lens assembly
exhibits an aspect ratio less than about 1.
7. The optical lens assembly of claim 1, wherein the input surface
of at least one of said lenses is configured such that the light
from the light source incident thereon is substantially orthogonal
thereto.
8. The optical lens assembly of claim 1, wherein at least of said
lenses exhibits a flat output surface.
9. The optical lens assembly of claim 1, wherein the plurality of
lenses comprises an inner lens, a middle lens, and an outer
lens.
10. The optical lens assembly of claim 9, wherein the plurality of
lenses are removably and replaceably coupled to one another.
11. The optical lens assembly of claim 1, wherein each of said
lenses is selectively removable and replaceable independent of the
other lenses.
12. The optical lens assembly of claim 1, further comprising a lens
cap configured to receive light from one or more of the output
surfaces of the plurality of lenses.
13. The optical lens assembly of claim 12, wherein said lens cap
comprises a textured surface.
14. The optical lens assembly of claim 12, wherein said lens cap
comprises a plurality of microlenses.
15. The optical lens assembly of claim 12, wherein said lenses are
fixedly coupled to one another with each lens disposed in a cavity
of an adjacent outer lens.
16. The optical lens assembly of claim 15, further comprising a
retaining ring for fixating the lenses in a defined relationship
relative to one another.
17. The optical lens assembly of claim 15, wherein at least one of
said lenses comprises an annular shoulder seated in an annular
recess of an outer adjacent lens such that a lateral surface of
said at least one lens is separated by a gap from a respective
lateral surface of said outer adjacent lens.
18. The optical lens assembly of claim 16, wherein at least one of
said lenses comprises a lateral surface configured to redirect
light incident thereon via specular reflection.
19. The optical lens assembly of claim 18, wherein said lateral
surface providing specular reflection is metalized.
20. The optical lens assembly of claim 19, wherein said metalized
surface comprises a metal layer having a thickness in a range of
about 10 micrometers to about 100 micrometers.
21. An optical system, comprising a light source, an optical lens
assembly optically coupled to the light source to receive light
therefrom, said optical lens assembly comprising a central lens,
and a plurality of outer lenses disposed about the central lens,
wherein the lenses of the optical lens assembly are arranged
relative to one another and relative to the light source such that
each lens receives light emitted by the source into a different
angular subtense.
22. The optical system of claim 21, wherein the outer lenses are
annulus shaped lenses that circumferentially surround the central
lens at progressively increasing radial distance from the central
lens.
23. The optical system of claim 21, wherein said optical lens
assembly is configured to redirect at least a portion of the light
received from the light via total internal reflection.
24. The optical system of claim 21, wherein each of the lenses of
the optical assembly comprises an input surface, an output surface
and a lateral surface that extends between the input and the output
surface.
25. The optical system of claim 23, wherein the lateral surface of
at least one of said lenses is configured to reflect light incident
thereon via total internal reflection.
26. The optical system of claim 21, wherein the input surface of
said central lens is a convex surface adapted to collimate light it
receives from the light source.
27. The optical system of claim 26, wherein each of said outer
lenses comprises a concave input surface configured as a section of
a putative sphere centered on the light source.
28. The optical system of claim 21, wherein the lateral surface of
each of said lenses is separated by a gap from a lateral surface of
an adjacent lens.
29. The optical system of claim 21, wherein said lenses are
removably and replaceably coupled to one another.
30. The optical system of claim 21, wherein said optical lens
assembly has an aspect ratio in a range of about 0.1 to about
1.
31. A kit, comprising a plurality of lenses configured to removably
and replaceably couple to one another to form a lens assembly
configured to receive light from a light source, wherein the lenses
of the lens assembly are arranged relative to one another such that
each of said lenses can receive at it input surface light emitted
by the source into an angular subtense different from a respective
angular subtense associated with another lens.
32. The kit of claim 31, wherein at least one of the lenses guides
at least a portion of the received light to its output surface via
total internal reflection at a lateral surface thereof extending
between the input and the output surface.
Description
RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 13/955,839, filed Jul. 31, 2013, which claims
the benefit of and priority to U.S. Provisional Application No.
61/809,631, filed Apr. 8, 2013 and U.S. Provisional Application No.
61/678,781, filed on Aug. 2, 2012. The entire teachings of these
earlier applications are incorporated by reference herein.
BACKGROUND
[0002] The present invention is generally directed to a lens
assembly, and particularly to a lens assembly in which a plurality
of lenses collimate light received from a light source via total
internal reflection (TIR) as well as optical systems employing such
a lens assembly.
[0003] In many lighting applications, the light source, e.g., a
light emitting diode (LED), can be large. The use of large
traditional TIR lenses to collimate light from such large light
sources can be problematic. For example, manufacturing such TIR
lenses, e.g., via molding, can be difficult. Further, many lighting
applications can impose spatial constraints that can render the use
of such traditional TIR lenses impractical.
[0004] Accordingly, there is a need for improved lenses, optics and
lens assemblies for redirecting, e.g., collimating, light emitted
by a light source, particularly a large light source.
SUMMARY
[0005] In one aspect, an optical lens assembly (herein referred to
also as an optic) is provided that comprises a plurality of lenses
(or lens segments) adapted to receive light from a light source,
each of said lenses (or lens segments) having an input surface and
an output surface and a lateral surface extending between the input
and output surfaces. The lenses are arranged relative to one
another and positioned relative to the light source such that each
of the lenses receives at its input surface a different portion of
light emitted by the source, e.g., each lens receives at its input
surface light emitted by the source into an angular subtense (solid
angle) different than an angular subtense associated with another
lens. Each lens (or lens segment) guides at least a portion of the
received light to its output surface via reflection, e.g., via
total internal reflection (TIR).
[0006] In some embodiments, the lenses are arranged relative to one
another and the light source such that they collectively receive at
least about 80 percent, or at least about 90 percent, or 100
percent, of the light energy emitted by the source.
[0007] In some embodiments, at least one of the lenses in
configured to collimate the light it receives from the light
source. In some embodiments, all of the lenses are configured to
collimate the light they receive from the light source.
[0008] In some embodiments, each of the lenses is rotationally
symmetric about an optical axis. In some embodiments, the optical
axis of the lenses can coincide with an optical axis of the light
source. In some other embodiments, the optical axis of the lenses
can be offset relative to an optical axis of the light source.
[0009] In some embodiments, the plurality of lenses comprises an
inner lens, a middle lens, and an outer lens.
[0010] In some embodiments, at least a portion of the lateral
surface of at least one of the lenses is separated by an airgap
from at least a portion of the lateral surface of an adjacent lens.
As discussed in more detail below, such an airgap can allow
redirection, via TIR, of the light incident on those portions of
the lateral surfaces. In such cases, the lateral surface can be
configured in a manner known in the art such that the incident
light (or a substantial portion thereof) is incident on the surface
at an angle that exceeds the critical angle associated with the
interface between the lens body and air so as to cause total
internal reflection of the incident light. In some embodiments, at
least one of the lenses includes a lateral surface configured to
redirect light incident thereon via specular reflection. For
example, at least a portion of such a lateral surface can be
metalized, e.g., via a metal layer having a thickness in a range of
about 10 micrometers to about 100 micrometers, to cause specular
reflection of light incident thereon.
[0011] In some embodiments, the lateral surface of at least one of
the lenses includes two portions forming a non-zero angle, e.g., an
acute angle, relative to one another.
[0012] In some embodiments, the optical lens assembly can exhibit
an aspect ratio, as defined below, that is equal to or less than
about 1, e.g., in a range of about 0.1 to about 1.
[0013] In some embodiments, at least one of the lenses (or the lens
segments) includes input surfaces with the input surface configured
to be substantially orthogonal to light rays it receives from the
light source. In some embodiments, a central lens (or lens segment)
can include a curved surface for collimating the received light via
refraction. In some embodiments, at least one, or all, of the outer
lenses surrounding the central lens an include a concave input
surface configured as a section of a putative sphere centered on
the light source.
[0014] In related aspects, the plurality of lenses are removably
and replaceably coupled to one another. For example, in some
embodiments, each of the lenses is selectively removable and
replaceable independent of the other lenses.
[0015] In some aspects, the optical lens assembly can further
comprise a lens cap configured to receive light from one or more of
the output surfaces of the plurality of lenses and from the light
source. In some embodiments, the cap includes a textured surface,
e.g., a plurality of microlenses.
[0016] In some embodiments of the above optical lens assembly, the
lenses are fixedly coupled to one another with each lens at least
partially disposed in a cavity of an adjacent outer lens. In some
such embodiments, at least one of the lenses includes an annular
shoulder seated in an annular recess of an outer adjacent lens such
that a lateral surface of that lens is separated by a gap from a
respective lateral surface of the outer adjacent lens. In some
embodiments, the optical lens assembly can further include a
retaining ring for fixating the lenses in a defined relationship
relative to one another.
[0017] In further aspects, an optical system is disclosed, which
comprises a light source, and an optical lens assembly that is
coupled to the light source to receive light therefrom. The optical
lens assembly includes a central lens, and a plurality of outer
lenses disposed about the central lens, where the lenses of the
optical lens assembly are arranged relative to one another and
relative to the light source such that each lens receives light
emitted by the source into a different angular subtense.
[0018] In some embodiments, the outer lenses are annulus-shaped
lenses that circumferentially surround the central lens at
progressively increasing radial distances from the central lens. In
some embodiments, a lateral surface of each of the lenses is
separated by a gap from a lateral surface of an adjacent lens.
[0019] In some embodiments, the lenses can be removably and
replaceably coupled to one another. In some embodiments, each lens
can be selectively removed and replaced independent of the other
lenses.
[0020] In some embodiments of the above optical system, the optical
lens assembly can have an aspect ratio in a range of about 0.1 to
about 1.
[0021] In some embodiments, in the above optical system, the
optical lens assembly is configured to redirect at least a portion
of the light received from the light source via total internal
reflection. For example, in some such embodiments, each of the
lenses includes an input surface, an output surface and a lateral
surface that extends between the input and the output surfaces,
where the lateral surface of at least one of the lenses is
configured to reflect the light from the source incident thereon
via total internal reflection.
[0022] In some embodiments of the above optical system, the input
surface of the central lens is a convex surface adapted to
collimate light (i.e., it generates a set of substantially parallel
light rays) it receives from the light source and each of the outer
lenses includes a concave input surface configured as a section of
a putative sphere centered on the light source.
[0023] In other aspects, a kit is disclosed that includes a
plurality of lenses configured to removably and replaceably couple
to one another to form a lens assembly configured to receive light
from a light source. The lenses of the lens assembly are arranged
relative to one another such that such that each of the lenses can
receive at input surface light emitted by the source into an
angular subtense different from a respective angular subtense
associated with another lens. In some embodiments, at least one of
the lenses guides at least a portion of the received light to its
output surface via total internal reflection at a lateral surface
that extends between the input surface and the output surface.
[0024] Various features of each embodiment described above can be
combined with one or more features of the other embodiments.
Further understanding of various aspects of the invention can be
obtained by reference to the following detailed description in
conjunction with associated drawings, which are described briefly
below.
BRIEF DESCRIPTION OF THE DRAWINGS
[0025] FIG. 1A schematically depicts a cross-sectional view of a
lens assembly according to an embodiment of the invention,
[0026] FIG. 1B schematically depicts exemplary ray traces through
some lenses of the lens assembly of FIG. 1A,
[0027] FIG. 2A is an elevation view of the lens assembly of FIG. 1A
depicting its output surface,
[0028] FIG. 2B is an elevation view of the lens assembly of FIG. 1A
depicting its input surface,
[0029] FIG. 3A is a view of the output surface of the lens assembly
of FIG. 1A,
[0030] FIG. 3B is a view of the input surface of the lens assembly
of FIG. 1A,
[0031] FIGS. 4 and 5 schematically depict one way of assembling the
lenses of a lens assembly according to an embodiment of the
invention,
[0032] FIG. 6 is a schematic cross-sectional view of a lens
assembly according to another embodiment of the invention,
[0033] FIG. 7A is an exemplary distribution pattern of light
exiting a lens assembly based on an implementation of the
embodiment of FIG. 6,
[0034] FIG. 7B shows the light intensity along the y-axis of the
distribution pattern shown in FIG. 7A,
[0035] FIG. 7C shows the light intensity along the x-axis of the
distribution pattern shown in FIG. 7A,
[0036] FIG. 8 is a schematic cross-sectional view of another lens
assembly according to another embodiment of the invention,
[0037] FIG. 9 is a schematic cross-sectional view of another lens
assembly according to another embodiment of the invention,
[0038] FIG. 10A is an exemplary distribution pattern of light
exiting a lens assembly based on an implementation of the
embodiment of FIG. 9,
[0039] FIG. 10B shows the light intensity along the y-axis of the
distribution pattern shown in FIG. 10A,
[0040] FIG. 10C shows the light intensity along the x-axis of the
distribution pattern shown in FIG. 10A,
[0041] FIG. 11 is a schematic cross-sectional view of another lens
assembly according to another embodiment of the invention,
[0042] FIG. 12A is an exemplary distribution pattern of light
exiting a lens assembly based on an implementation of the
embodiment FIG. 11,
[0043] FIG. 12B shows the light intensity along the y-axis of the
distribution pattern shown in FIG. 12A,
[0044] FIG. 12C shows the light intensity along the x-axis of the
distribution pattern of FIG. 12A,
[0045] FIG. 13 is a schematic cross-sectional view of another lens
assembly according to another embodiment of the invention,
[0046] FIG. 14A is an exemplary distribution pattern of light
exiting an implementation of the lens assembly of FIG. 11 without
the lens cap,
[0047] FIG. 14B is another example of distribution pattern of light
exiting an implementation of the lens assembly of FIG. 11 without
the lens cap,
[0048] FIG. 14C is another example of distribution pattern of light
exiting an implementation of the lens assembly of FIG. 11 without
the lens cap, and
[0049] FIG. 15 is a schematic cross-sectional view of a lens
assembly according to another embodiment of the invention.
DETAILED DESCRIPTION
[0050] The present invention is generally directed to a lens
assembly (herein also referred to as an optic) that includes a
plurality of lenses arranged to receive light from a light source
such that each lens receives at its input surface light emitted by
the source into a different angular subtense associated with that
lens. Each lens is configured to redirect at least a portion of the
received light to an output surface via total internal reflection
(TIR), or in some cases via specular reflection. In many
embodiments, an airgap can separate lateral surfaces of adjacent
lenses to allow those surfaces to function as TIR surfaces for
redirecting, e.g., collimating, the light incident thereon. This in
turn allows achieving a high level of redirection (collimation)
while keeping the height of the lens assembly at a desired level.
The lens assemblies according to various embodiments can be used in
a variety of lighting applications, and particularly in those in
which mechanical geometry requires minimal optic height and a high
level of collimation. For example, they can be particularly useful
in applications in which large light emitting diodes (LEDs) are
employed.
[0051] The phrase an "angular subtense" is used consistent with its
meaning in the art. For example, an angular subtense associated
with a lens refers to a region of space defined by a solid angle
that has its apex at the light source and that subtends an input
surface of the lens (See, e.g., FIG. 1B).
[0052] The terms "about" is used herein to mean a deviation of at
most 5 percent, e.g., between 1 and 5 percent, in a value.
[0053] The phrase "substantially orthogonal" as used herein refers
to an angle of 90 degrees within a deviation of at most 5-degrees,
e.g., 1, 2 or 5-degrees.
[0054] The phrase "substantially parallel to the optical axis" as
used herein refers to a direction that is parallel to the optical
axis with a deviation, if any, of at most 5-degrees from
parallelism.
[0055] FIGS. 1A, 1B, 2A, 2B, 3A and 3B schematically depict a lens
assembly 10 according to an embodiment of the invention that
includes a plurality of lenses 12, 14, 16, 18, 20, and 22 (herein
collectively referred to as lenses 24) that are adapted to receive
light emitted from a light source 26. In this embodiment, the
lenses 24 are rotationally symmetric about the optical axis OA,
which coincides with the optical axis of the light source 26. In
this embodiment, the lens 12 is a central lens that is
circumferentially surrounded by annulus-shaped lenses 14, 16, 18,
20, and 22 (herein referred to collectively as the outer lenses),
which are disposed progressively at greater radial distances from
the optical axis (OA) (the radial distance refers to a distance
perpendicular to the optical axis). In other embodiments, the
optical axis of the lenses, e.g., an axis about which the lenses
exhibit a rotational symmetry, may be offset relative to a
respective optical axis of the light source. Further, in some
embodiments, one or more of the lenses may not be rotationally
asymmetric.
[0056] In this embodiment, the lenses are arranged relative to one
another such that each lens receives light emitted by the source
into a different angular subtense (solid angle). By way of example,
with reference to FIG. 1B, in this embodiment, the central lens 12
receives light emitted by the light source into an angular subtense
.gamma. while the lenses 18 and 22 receive light emitted by the
source into different angular subtenses .alpha. and .beta.,
respectively. In this manner, the lenses collectively receive light
emitted by the source into different solid angles. In some
embodiments, the lenses collectively receive at least about 80
percent, or at least about 85 percent, or at least about 90
percent, or at least about 95 percent, or 100 percent, of the light
energy emitted by the source.
[0057] As discussed in more detail below, each of the lenses 24
includes an input surface for receiving light from the light source
and an output surface through which light exits the lens and a
lateral surface that extends between the input surface and the
output surface. At least a portion of the light that is coupled
into the lens body via the input surface is incident on the lateral
surface so as to be totally internally reflected at that surface
toward the output surface for exiting the lens. In this manner, the
lens assembly 10 redirects, e.g., collimates, via total internal
reflection at least a portion of the light it receives.
[0058] By way of example, the lens 14 includes an input surface
14a, an output surface 14b, and a lateral surface 14c that extends
between the input surface 14a and the output surface 14b. In this
embodiment, the input surface 14a is a concave surface that is
shaped as a section of a putative sphere centered at the light
source such that the light from the source (i.e., the light emitted
by the source into the angular subtense associated with the lens
14) is incident thereon in a substantially orthogonal direction (as
discussed below, in this embodiment, the input surfaces of the
other lenses 16, 18, 20, and 22 are also shaped as sections of the
putative spherical surface centered on the light source). In this
manner, the light enters the lens without much deviation from its
propagating direction to be incident on the lateral surface 14c.
The lateral surface 14c is separated from a respective lateral
surface of adjacent lenses 12 and 16 by airgaps 1 and 2. As air has
an index of refraction that is lower than that of the material
forming the lenses, the lateral surface 14c can be configured in a
manner known in the art to cause total internal reflection of the
light incident thereon, or at least a portion of that light (e.g.,
at least about 80% or 90%, or 100%). In this embodiment, the
lateral surface is configured to collimate the light incident
thereon via TIR along a direction that is substantially parallel to
the optical axis (OA) (i.e., parallel to the optical axis (OA)
within a deviation of at most 5-degrees, e.g., 1, 2, or 5 degrees).
The collimated light then exits the lens through the output surface
14b, which is substantially flat and orthogonal to the optical axis
OA. In other embodiments, one or both of the input and output
surfaces 14a and 14b can have other shapes.
[0059] In this embodiment, the lenses 16, 18, 20 and 22 also
include concave input surfaces (e.g., input surface 20a of the lens
20) that are configured as sections of a putative sphere centered
on the light source so as to be substantially orthogonal to the
light incident thereon, and further include flat output surfaces
(e.g., the output surface 20b of the lens 20) that are
substantially orthogonal to the optical axis (OA). In these lenses,
the outer segment of the lateral surface (e.g., the portion 22co of
the lateral surface 22c of the lens 22) can be formed of two
portions that form an angle relative to one another (e.g., portions
22coi and 22coii, where the segment 22coii does not participate in
light redirection) so as to ensure that the input surface is
substantially orthogonal to the light it receives from the light
source. Similar to the lens 14, the lateral surfaces of these
lenses are also separated by airgaps from lateral surfaces of
adjacent lenses and are configured to redirect incident light via
TIR.
[0060] In contrast to the outer lenses, the inner central lens 12
includes a generally convex curved input surface 12a that
substantially collimates the light it receives from the light
source via refraction to redirect that light to its flat output
surface 12b, which is orthogonal to the optical axis (OA), for
exiting the lens. While the outer lenses redirect the received
light substantially via TIR for exiting their output surfaces in a
direction substantially parallel to the optical axis, the inner
lens redirects the received light substantially via refraction
(e.g., refraction at its input surface) for exiting its output
surface in a direction parallel to the optical axis. In this
manner, the lens assembly collectively collimates the light
received from the source. It should be understood that some light
rays may strike the lateral surface of the inner lens 12 to be
reflected via TIR (an airgap separates the lateral surface of lens
12 relative to that of lens 14).
[0061] In other embodiments, the central lens 12 can be configured
to redirect the received light, e.g., to collimate the received
light, primarily via TIR, e.g., in a manner discussed above in
connection with the outer lenses.
[0062] With reference to FIG. 1B, the lens assembly 10 can have an
aspect ratio equal to or less than about 1, e.g., in a range of
about 0.1 to about 1, where the aspect ratio is defined herein as
the ratio of the height (H) of the assembly (in this case, the
linear extent of the lens assembly along the optical axis OA)
relative to the largest linear dimension of a putative surface that
comprises all the output surfaces of the lenses and airgaps, if
any, separating them; in this case, the diameter (D). In many
embodiments, this aspect ratio allows an efficient redirection,
e.g., collimation, of the light emitted by the source, particularly
a large source such as a large LED, while ensuring that the height
of the lens assembly remains below a desired value. In particular,
a putative parabola (a geometry most associated with light
collection) centered on the light source and having a similar
diameter D of the optic's aperture would have an aspect ratio, as
defined above, that can be represented by the following
mathematical relation:
Aspect ratio = Bx 2 + C x ##EQU00001##
where x denotes the radius of the aperture (x=D/2), and B and C are
constant.
[0063] The above relation shows that as x increases, the aspect
ratio of such a putative parabola increases rapidly such that it
would be greater than 1 in many practical applications. In
contrast, the lens assembly according to the invention can provide
redirection (e.g., collimation) performance that is at least equal
to, and in many cases better than, the respective performance of
such a parabolic reflector while exhibiting a smaller aspect ratio,
e.g., an aspect ratio less than 1.
[0064] The lenses 24 can be made from a variety of different
materials. Some examples of such materials include, without
limitation, poly methyl methacrylate (PMMA), poly methyl
methacrylimide (PMMI), cyclic olefin copolymer (COC), among others.
In some embodiments, each of the lenses 24 can be molded
individually (e.g., via injection molding) and then assembled. Many
manufacturing methods are available for assembling the lenses. Some
examples of such methods include, without limitation, ultra-sonic
welding, gluing, heat-stacking, snap fitting, force fitting,
etc.
[0065] As noted above, the lenses 24 of the lens assembly 10 can be
fixated relative to one another in a variety of different ways. By
way of example, FIGS. 4 and 5 schematically depict one way of
stacking three of such lenses and fixating them relative to one
another such that airgaps separate lateral surfaces of adjacent
lenses. In particular, in this example, an outermost lens 30
includes a central cavity into which a lens 32 can be inserted. The
lens 32 includes a shoulder 32a surrounding its output surface that
can be seated in a recess 30a of the lens 30 such that an airgap
separates the lateral surfaces of the lenses 30 and 32. A central
lens 34 can then be received by a central cavity of the lens 32.
Again, a shoulder 34a of the lens 34 can be seated in a recess 32b
of the lens 32 such that the lateral surfaces of the two lenses are
separated by an airgap. A retaining ring 36 can then hold the
lenses in place.
[0066] In some embodiments, the output surfaces of one or more of
the lenses can include a textured surface, e.g., a plurality of
microlenses, to alter the light incident on the output surface(s),
e.g., the collimated light, to achieve specific beam angles.
[0067] In some embodiments, the lenses 24 of the lens assembly 10
can be selectively removable and/or replaceable so as to allow the
configuration of the lens assembly 10 to be altered so as to
control the far-field illumination pattern, for example. For
example, each of the lenses can be removed and replaced independent
of the other lenses, i.e., without a need to remove any of the
other lenses.
[0068] Additionally or alternatively, a lens cap can be configured
to couple to the output end of the lens assembly 10 for altering
(e.g., diffusing) the light exiting the lens assembly 10 and/or
preventing a person from receiving light directly from the light
source. In such a manner, the user can selectively couple the
lenses and/or lens cap in various combinations such that the lens
assembly 10 produces a specified beam angle or far-field
illumination pattern.
[0069] For example, with reference now to FIGS. 6-13, an exemplary
lighting assembly 10 is depicted in which various lenses can be
selectively coupled to one another and/or to which a lens cap 40
can be selectively applied so as to control the distribution of
light exiting the lens assembly 10. With specific reference first
to FIG. 6, the exemplary lighting system 10 includes an annular
outer lens 30 defining a central cavity 42 and having two annular
recesses 30a,b surrounding the central cavity adjacent the output
end of the outer lens 30, for example, as described above with
reference to FIGS. 4 and 5. As shown in FIG. 6, however, a lens cap
40 can be configured to be disposed within the recess 30a and
across the central cavity such that light emitted by the source
through the central cavity 42 is diffused by the lens cap 40. As
such, a user can configure the lens assembly 10 as shown in FIG. 6
to produce a very wide beam far-field distribution pattern (e.g., a
flood pattern), e.g., such as that depicted in FIGS. 7A, 7B, and
7C.
[0070] The lens cap 40 can have a variety of configurations so as
to control the distribution of light. By way of example, the lens
cap 40 can have a textured surface, e.g., a plurality of
microlenses, to alter the light incident on the lens cap 40 to
achieve specific beam angles. Rather than rest within the recess
30a, it will be appreciated that the lens cap 40 can alternatively
be coupled to the lens assembly such that light exiting the output
surface of the outer lens 30 also passes through the lens cap 40,
as depicted in FIG. 8, for example.
[0071] With reference now to FIG. 9, in another exemplary
configuration of the lens assembly 10, the lens cap 40 of FIG. 6
can be removed and replaced with an inner lens 34 having a shoulder
34a configured to engage the recess 30a of the outer lens 30
(alternatively, the lens cap 40 of FIG. 8, can be disposed on or
coupled to the output surface of both the outer lens 30 and inner
lens 34). As discussed otherwise herein, the input surface, the
output, and the lateral surfaces of the inner lens 34 can be
configured so as to control the beam angle of the light exiting the
output surface of the inner lens 34. In such a manner, the user can
generate a wide beam output via the light exiting the outer lens 30
and inner lens 34, for example, as depicted in FIGS. 10A, 10B, and
10C. It will further be appreciated that in some embodiments, the
shoulder 34a of the inner lens 34 can diffuse the light impinging
thereon from the source or have a textured surface (e.g., a
microlens array) so as to control the distribution of light exiting
therefrom.
[0072] With reference now to FIG. 11, another exemplary
configuration of the lens assembly 10 is depicted which can be used
to provide a medium beam lens that can produce, e.g., the exemplary
light distribution depicted in FIGS. 12A, 12B, and 12C. The
configuration of the lens assembly 10 in FIG. 11 is like that
depicted in FIG. 9 but differs in that a middle lens 32 is disposed
within the central cavity and between the outer lens 30 and the
inner lens 34. As will be appreciated by a person skilled in the
art, the middle lens 32 can also include a shoulder 32a and can be
dimensioned so as to engage the recess 30b of the outer lens 30,
with the shoulder 34a of the lens 34 extending over the middle lens
32 and remaining in engagement with the recess 30a of the outer
lens.
[0073] Similar to the discussion above in which the inner lens 34
and middle lens 32 can be selectively replaced, the outer lens 30
can also be removable and replaceable in the lens assembly 10 so as
to control the output pattern of light. By way of example, the
outer lens 30 can be replaced by one of a similar size but having
different output characteristics so as to generate a more narrow
beam (e.g., without a microlens array on its output surface).
Alternatively, the lens cap 40 described above with reference to
FIG. 8, which can be disposed over the outer lens 30, middle lens
32, and inner lens 34 (i.e., medium beam pattern) as shown in FIG.
13, can be removed as shown in FIG. 11 such that the output beam
becomes narrow, for example, as depicted in FIGS. 14A, 14B, and
14C.
[0074] It will thus be appreciated in light of the present
teachings that there exits many variations and configurations for
the output surfaces of the various lenses and their nesting
configurations with or without a lens cap 40 that can be used to
tailor the output of the lens assembly 10 to a particular
application.
[0075] Further, in some embodiments, one or more of the lenses can
employ specular reflection, rather than total internal reflection,
for redirecting, for example, collimating, at least a portion of
the light received from the light source. For example, in some such
embodiments, at least a portion (and in some cases the entire)
lateral surface of one or more of the lenses can be metalized to
provide specular reflection of the light incident thereon. In some
embodiments, a combination of specular and total internal
reflection can be employed for redirecting the light received from
the light source.
[0076] By way of example, FIG. 15 schematically depicts a lens
assembly 10' according to another embodiment of the invention that
includes a plurality of lenses 12', 14', 16', 18', 20' and 22'
arranged in a fixed relationship relative to one another to receive
light from the light source 26. Similar to the lens assembly 10
discussed above, each of the lenses of the lens assembly 10' is
configured and positioned relative to the light source so as to
receive light emitted by the source into a different solid angle
(angular subtense). While the lenses in the lens assembly 10 rely
on total internal reflection to redirect at least some of the
received light, the lenses in the lens assembly 10' rely on
specular reflection for redirecting at least a portion of the
received light. In particular, at least a portion of the lateral
surface of each of the lenses of the lens assembly 10' is metalized
(e.g., a thin metal layer having a thickness in a range of about 10
micrometers (.mu.m) to about 100 .mu.m is deposited on the surface)
to provide a reflective surface for redirecting the incident light
to the output surface. In this embodiment, the lenses 12', 14',
16', 18', 20' and 22' include, respectively, thin metal coatings
12'a, 14'a, 16'a, 18'a, 20'a, and 22'a on at least a portion of
their lateral surfaces for reflecting and thereby redirecting at
least a portion of the received light. In some such embodiments,
the use of metal coating obviates the need to have airgaps between
the lateral surfaces of adjacent lenses and hence allows those
surfaces to be in contact with one another.
[0077] Those having ordinary skill in the art will appreciate that
various changes can be made to the above embodiments without
departing from the scope of the invention. For example, the output
surface of the lens assembly (e.g., a putative surface comprising
the output surface of the lenses of the lens assembly and airgaps,
if any, separating the lenses) can have a shape other than
circular, such as square, rectangular, elliptical, etc.
* * * * *