U.S. patent application number 16/063453 was filed with the patent office on 2019-11-07 for reducing thermal sensitivity of a lighting arrangement.
This patent application is currently assigned to Lumileds LLC. The applicant listed for this patent is Lumileds LLC. Invention is credited to Juergen MERTENS, Florent MONESTIER, Benno SPINGER.
Application Number | 20190338930 16/063453 |
Document ID | / |
Family ID | 57123842 |
Filed Date | 2019-11-07 |
![](/patent/app/20190338930/US20190338930A1-20191107-D00000.png)
![](/patent/app/20190338930/US20190338930A1-20191107-D00001.png)
![](/patent/app/20190338930/US20190338930A1-20191107-D00002.png)
![](/patent/app/20190338930/US20190338930A1-20191107-D00003.png)
![](/patent/app/20190338930/US20190338930A1-20191107-D00004.png)
![](/patent/app/20190338930/US20190338930A1-20191107-D00005.png)
![](/patent/app/20190338930/US20190338930A1-20191107-D00006.png)
![](/patent/app/20190338930/US20190338930A1-20191107-D00007.png)
United States Patent
Application |
20190338930 |
Kind Code |
A1 |
SPINGER; Benno ; et
al. |
November 7, 2019 |
REDUCING THERMAL SENSITIVITY OF A LIGHTING ARRANGEMENT
Abstract
The invention relates to a lighting arrangement with at least
one LED lighting element (15) arranged on a support member (12). An
optical element (16) is arranged spaced from the LED lighting
element (15) in a first direction O. A holder (14) is provided to
hold the optical element (16) in a position relative to the LED
lighting element (15). The holder (14) comprises at least a first
holding portion (24a) extending from the support member (12) into
the first direction O and a second holding portion (24b) connected
to the optical element (16). The second holding portion (24b) is
arranged such that at least a part extends into the first direction
O. The second holding portion (26b) is spaced from the first
holding portion (24a) in a direction traverse to the first
direction O. In the case of distortions due to temperature changes
and a mismatch of the coefficient of thermal expansion, the
lighting arrangement minimizes variations in the displacement of
the optical element (16) relative to the LED lighting element
(15).
Inventors: |
SPINGER; Benno; (Aachen,
DE) ; MONESTIER; Florent; (Aachen, DE) ;
MERTENS; Juergen; (Aachen, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Lumileds LLC |
San Jose |
CA |
US |
|
|
Assignee: |
Lumileds LLC
San Jose
CA
|
Family ID: |
57123842 |
Appl. No.: |
16/063453 |
Filed: |
September 27, 2017 |
PCT Filed: |
September 27, 2017 |
PCT NO: |
PCT/EP2017/074532 |
371 Date: |
June 18, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G02B 7/028 20130101;
F21V 14/006 20130101; F21S 41/153 20180101; H01S 5/02288 20130101;
F21V 17/10 20130101; F21V 5/007 20130101; F21S 41/143 20180101;
F21Y 2115/10 20160801; G02B 7/008 20130101; F21V 19/0015 20130101;
F21S 41/663 20180101; F21Y 2105/10 20160801; F21S 41/29
20180101 |
International
Class: |
F21V 19/00 20060101
F21V019/00; G02B 7/02 20060101 G02B007/02; F21V 14/00 20060101
F21V014/00; H01S 5/022 20060101 H01S005/022 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 4, 2016 |
EP |
16192238.0 |
Claims
1. A lighting arrangement comprising: at least one light emitting
diode (LED) lighting element arranged on a support member; an
optical element arranged spaced from the LED lighting element in a
first direction; and a holder to hold the optical element in a
position relative to the LED lighting element, the holder
comprising at least a first holding portion extending from the
support member into the first direction and a second holding
portion connected to the optical element arranged such that at
least a part of the second holding portion extends into the first
direction, wherein the second holding portion is spaced from the
first holding portion in a direction traverse to the first
direction, wherein the first holding portion and the second holding
portion are connected by a first connecting portion arranged to
form an angle with both the first holding portion and the second
holding portion, wherein the first connecting portion is a plane
wall element having a greater thickness than the first holding
portion and the second holding portion, and wherein the optical
element is one piece with the first holding portion and the second
holding portion.
2. The lighting arrangement of claim 1, wherein the first holding
portion extends into the first direction beyond the optical
element.
3. The lighting arrangement of claim 1, wherein the first holding
portion and the second holding portion are substantially in
parallel to each other.
4. The lighting arrangement of claim 1, wherein the first
connecting portion extends substantially perpendicular to the first
direction.
5. The lighting arrangement of claim 1, wherein the second holding
portion is connected to the optical element by a second connecting
portion extending substantially perpendicular to the first
direction.
6. The lighting arrangement of claim 1, further comprising: a
plurality of LED lighting elements arranged on the support member
spaced apart from each other; and a plurality of optical elements
arranged spaced apart from the plurality of LED lighting elements
in the first direction, wherein the plurality of optical elements
are connected to each other.
7. The lighting arrangement of claim 1, wherein the first holding
portion and the second holding portion are plane wall elements.
8. The lighting arrangement of claim 1, wherein the first holding
portion and the second holding portion to surround the optical
element.
9. The lighting arrangement of claim 1, wherein the holder is a box
shaped housing comprising at least a pair of first housing walls
parallel to each other and a pair of second housing walls parallel
to each other, first housing walls and the second housing walls
substantially perpendicular to each other.
10. The lighting arrangement of claim 1, wherein the holder element
comprises a base portion, and a clamp element affixing the base
portion to the support member.
11. The lighting arrangement of claim 1, wherein the optical
element comprises one or more of a collimator element and a lens
element.
Description
FIELD OF THE INVENTION
[0001] The invention relates to the field of lighting, and more
specifically to a lighting arrangement comprising at least one LED
lighting element and an optical element.
BACKGROUND OF THE INVENTION
[0002] Lighting arrangements with LEDs are used for an ever
increasing number of lighting applications. In many cases, an
optical element is arranged in front of an LED to alter the light
emission, such as e.g. a lens, a reflector and/or a collimator to
obtain an emitted light beam of desired properties.
[0003] The properties of the emitted light may depend on the exact
positioning of the optical element relative to the LED. An exact
positioning of the optical element is therefore advantageous.
[0004] DE 10 2008 047 277 A1 shows a device having a carrier
arrangement holding an objective to change a focal plane relative
to a charge coupled device chip. The objective is arranged in a
section of a compensation body that extends along an optical axis,
wherein the compensation body is connected in another section with
the carrier arrangement. The compensation body includes a material
with a thermal expansion coefficient, which is measured such that a
temperature-dependent change of the arrangement of the focal plane
to the optical component is balanced.
[0005] U.S. Pat. No. 5,270,870 A discloses an athermalized beam
source and collimator assembly includes a collimator lens spaced
from a circular foldback flexure plate by a lens barrel. The
circular foldback flexure plate incorporates a circular foldback
flexure adjacent the beam source mount to isolate the beam source
from the ambient environment and to athermalize the assembly. The
beam source mount and circular foldback flexure plate are composed
of a material that is identical in composition and CTE as the
portion of the beam source that is attached to the beam source
mount.
[0006] EP 2 884 157 A2 shows a motor vehicle headlamp with at least
one semiconductor light source and a primary optical system which
collects light emitted from the semiconductor light source and is
directed to a secondary optical system, wherein the primary optical
system receives the light from the light source via a light entry
surface and the light is emitted out via a light exit surface,
wherein the primary optical system has a connecting flange with
which the primary optical system is kept in a holder in at least
two fixed bearings, wherein a first section of the connecting
flange is curved like a dome.
SUMMARY OF THE INVENTION
[0007] It may be considered an object to achieve stable positioning
of an optical element over a wide range of operating
conditions.
[0008] This may be achieved by a lighting arrangement according to
claim 1. Dependent claims refer to preferred embodiments.
[0009] The present inventors have considered that thermal changes,
e.g. due to a change in ambient temperature or due to LED
electrical operating power dissipated as heat, may significantly
influence a holding structure provided to mount an optical element
relative to an LED. In particular, if the structure supporting the
LED and the optical element is comprised of different parts or
different materials with a differing coefficient of thermal
expansion (CTE), the structure may undergo distortions with
increasing temperature that could lead to variations in the
relative arrangement of the LED and the optical element. In order
to improve the thermal stability of the positioning of the optical
element, the inventors have proposed a special structure which has
proven to have relatively low temperature sensitivity even for
significant CTE mismatch.
[0010] The lighting arrangement according to the invention
comprises at least one LED lighting element. The term LED lighting
element should be understood to comprise any type of solid state
lighting element, such as e.g. light emitting diodes, organic light
emitting diodes, laser diodes, etc. An LED lighting element may
comprise a single one or a plurality of several of such solid state
lighting elements, e.g. one or a plurality of light emitting diodes
arranged in close proximity.
[0011] One or several of such LED lighting elements may be arranged
on a support member, and at least one optical element may be
arranged spaced from the LED lighting element in a first direction,
e.g. along an optical axis. Preferably, the optical element may be
arranged directly in front of the LED lighting element,
particularly preferred in the main light emission direction, e.g.
perpendicular to a light emitting surface of the LED lighting
element.
[0012] The optical element may be any type of element with an
optical function, in particular to alter the beam of light emitted
from the LED lighting element. The optical element may thus
comprise or be comprised of a reflector, a collimator, a lens, an
optical filter, a baffle, etc, or a combination of such elements.
Preferably, it is made of or at least comprises a transparent or
translucent material. The optical element preferably receives light
from the LED lighting element and emits a modified beam, which may
be e.g. focussed, collimated, redirected, filtered etc.
[0013] A holder is provided to hold the optical element in a
position relative to the LED lighting element. The holder according
to the invention has a specially designed structure, such that it
comprises at least a first and a second holding portion. The first
holding portion extends from the support member into the first
direction and the second holding portion, which is connected
directly or indirectly to the optical element, is arranged such
that at least a part of it also extends into the first direction.
The second holding portion is spaced from the first holding portion
in a traverse direction, e. g. perpendicular to the first
direction.
[0014] The holder proposed for the lighting arrangement according
to the invention has a structure designed to be able to achieve
stable positioning of the optical element even in cases of severe
CTE mismatch, e.g. between the support member and the holder. The
first and second holding portions are not aligned, but offset in
the traverse direction, thus being able to e.g. form a loop-like
structure. A section of the holder in the shape of a loop may act
as a spring, i.e. deform. In cases of severe CTE mismatch, the
position of the optical element relative to the first direction,
e.g. the optical axis, can remain relatively stable, because
thermal expansion can be at least partly compensated in the first
direction by the first and second holding portions.
[0015] According to preferred embodiments, the first holding
portion may extend into the first direction beyond the optical
element. The second holding portion may then extend from its
connection to the optical element also into the first direction.
Thus, a loop may be formed.
[0016] As explained above, at least a part of the second holding
portion extends into the first direction. This should be understood
to cover also inclined arrangements, where e.g. the second holding
portion forms an angle of, for example, 25-65.degree. to the first
direction. Also, this comprises non-angular, e.g. bent or rounded
shapes of the second holding portion, as long as they at least
partially extend into the first direction. However, it is preferred
to provide the first and/or the second holding portions to extend
at least substantially straight. In particular, it is preferred
that the first and second holding portions may be arranged at least
substantially in parallel to each other. The term "at least
substantially" should be understood to cover minor variations, such
as e.g. +/-15.degree. or less, preferably +/-5.degree. or less.
[0017] According to one aspect of the invention, the first and
second holding portions are connected by a first connection portion
and the first connection portion is arranged to form an angle with
both the first and second holding portions. The angle may be e.g.
greater than 30.degree., preferably greater than 60.degree.. In a
particularly preferred embodiment, the first and second holding
portions are arranged at least substantially at right angles to the
first connecting portion.
[0018] The second holding portion may be directly attached to the
optical element, or the connection may be indirect through one or
more intervening elements. In a preferred embodiment, the second
holding portion may be connected to the optical element by a second
connecting portion. The second connecting portion may extend at
least substantially perpendicular (i.e. 90.degree.+/-15.degree.,
preferably 90.degree.+/-5.degree.) to the first direction.
[0019] The holder may comprise one or more further holding portions
besides the first and second holding portions. In some embodiments,
the further holding portions may extend into the first direction
and be arranged at least substantially in parallel to each other
and to the first and second holding portions. The holding portions
may be interconnected by connecting portions, which may be arranged
perpendicularly. In one embodiment, the lengths of the holding
portions differ. Shorter holding portions may be arranged closer to
the optical element. The holding portions may be arranged such that
each is shorter than the holding portion next to it into the
direction away from the optical element.
[0020] While the lighting arrangement may offer great advantages
already for a single LED lighting element and corresponding optical
element, it is particularly preferred to provide a plurality of LED
lighting elements and corresponding optical elements arranged
relative thereto. In particular, a plurality of LED lighting
elements may be arranged on the same support member spaced from
each other, e. g. in a line or matrix. The optical elements may be
arranged spaced from the LED lighting elements in the same
direction. In particular, the optical elements may be connected to
each other. The holder may be provided to hold two or more,
preferably all of the optical elements in a position relative to
the support member to thus ensure exact positioning for all optical
elements.
[0021] The holder may have many different shapes. Its main function
is to define the position of the optical element relative to the
support member, i.e. to lock its displacement. Any type, shape or
construction of a holder which serves this function, i.e. locks the
position of the optical element with respect to at least one,
preferably two, further preferably all three of x, y, and z
directions may be used.
[0022] In preferred embodiments, the holder may be comprised e.g.
of a plurality of bars, beams or other structures. Preferably, at
least the first and second holding portions may be provided as
plane wall elements. The holder may be comprised of a plurality of
such plane wall elements. The first connecting portion is provided
as a plane wall element having a greater thickness than the first
and second holding portions.
[0023] In a preferred embodiment, the first and second holding
portions may be arranged to surround the optical element. Thus, at
least a portion of the holder may be arranged as a housing
surrounding the optical element. In particular, the holder may be a
box-shaped housing with at least a pair of first housing walls
arranged in parallel to each other and a pair of second housing
walls arranged in parallel to each other. The first and second
housing walls are preferably arranged at least substantially
perpendicular to each other.
[0024] In a further preferred embodiment, the holder may comprise a
base portion, which is e.g. in contact with the support member. A
clamp element may be arranged to fix the base portion to the
support member. The holder may comprise a flange for engagement
with the clamp element.
[0025] It is particularly preferred to provide the first and second
holding portions of the holder in one piece, e.g. manufactured
together in injection moulding. According to one aspect of the
invention, the optical element is provided as one piece with both
the first and second holding portions, as well as optionally and
preferably any connection portions. A holder with an optical
element provided in one piece is particularly simple and efficient
to manufacture.
[0026] These and other aspects of the invention will be apparent
from and elucidated with reference to the embodiments described
hereinafter.
BRIEF DESCRIPTION OF THE DRAWINGS
[0027] In the drawings:
[0028] FIG. 1 shows a perspective view of a first embodiment of a
lighting arrangement;
[0029] FIG. 2, 3 show a side view and a top view of the lighting
arrangement of FIG. 1;
[0030] FIG. 4 shows a longitudinal sectional view along B-B in FIG.
3;
[0031] FIG. 5 shows a cross-sectional view along A-A in FIG. 2;
[0032] FIG. 6 shows an enlarged view of the portion C in FIG.
5;
[0033] FIG. 7 shows a partial cross-sectional view of a second
embodiment of a lighting arrangement;
[0034] FIG. 8 shows a partial cross-sectional view of a third
embodiment of a lighting arrangement;
[0035] FIG. 9a, 9b schematically show the structure of a holder
according to a generic embodiment;
[0036] FIG. 10a, 10b show the structure of a holder according to a
comparative example,
[0037] FIG. 11 shows a partial cross-sectional view of a fourth
embodiment of a lighting arrangement.
DETAILED DESCRIPTION OF EMBODIMENTS
[0038] A first embodiment of a lighting arrangement 10 shown in
FIG. 1-3 comprises a support member, in the present example a base
plate 12, onto which a plurality of light emitting diodes 15 see
(FIG. 6--not visible in FIGS. 1-5) and a holder 14 for a number of
optical elements 16 are mounted. As the skilled person will
understand, the base plate 12 shown is a simple an example of a
support member suited for illustration of the holding function of
the optical elements 16 relative to the base plate 12. In actual
embodiments, the base plate 12 may e.g. be a circuit board. In more
detailed embodiments, further components, not shown in the figures,
may be arranged on the base plate 12, such as e.g. electronic
components, conductor tracks, thermal interface elements and/or one
or more heat sinks.
[0039] As shown, the holder 14 is box-shaped to surround the
optical elements 16. It has a surrounding flange 22, which is held
down by a clamp 18 which may be fixed to the base plate 12 e.g. by
a screw connection.
[0040] FIGS. 4-6 show sectional views of the lighting arrangement
10. As shown in the enlarged view of FIG. 6, LEDs 15 are arranged
on the base plate 12. Spaced by a small distance d in the direction
of an optical axis O, the optical elements 16 are positioned. A
plurality of LED elements 15 are arranged in a line on top of the
base plate 12. As shown in FIG. 4, the optical elements 16 are each
arranged in front of the individual LED elements 15.
[0041] Each optical element 16 comprises a TIR collimator portion
16a arranged towards the LED elements 15 for receiving light
therefrom and a lens portion 16b to emit the light as a shaped
illumination beam into the direction of the optical axis O. In the
example shown, the holder 14 is manufactured in one piece with the
optical elements 16, made from a transparent material e.g.
silicone.
[0042] The LED elements 15 of the lighting arrangement 10 form an
LED matrix, which may be e.g. used in automotive front lighting. In
particular, the lighting arrangement 10 may be used for adaptive
driving lighting, where the LEDs may be operated independently or
in segments in order adjust the beam to a specific driving
situation. As shown in the figures, in particular FIGS. 4-6, the
optical elements 16 are each arranged in front of the LED elements
15. Distance d is preferably very small to allow good coupling of
light from the LED element 15 into the TIR collimator portion 16a
of each optical element 16.
[0043] However, variations of the arrangement of the optical
element 16 relative to the LED element 15, and in particular
variations to the distance d, can significantly alter the output
beam. A variation of the distance d may in particular alter the
intensity of the output beam.
[0044] FIG. 10a shows a schematic representation of a simple
box-shaped holder 14' for positioning the optical element 16
relative to the LED element 15. In this comparative example, the
holder 14' comprises on each side a first portion 24a extending
straight into the direction of the optical axis O and a second
portion 26 extending from the end of the first portion 24a at right
angles up to the optical element 16.
[0045] Assuming a significant CTE mismatch between the material of
the holder 14' and the base plate 12 in the comparative example, a
raised temperature will lead to distortions schematically shown in
FIG. 10b. As illustrated, this will lead to a significant change in
the relative arrangement of the LED element 15 and optical element
16, in particular with regard to the distance between these two
elements.
[0046] FIGS. 9a, 9b show a generic embodiment of a holder 14 for
comparison. In the generic embodiment, the holder 14 comprises on
both sides of the optical element 16 a first portion 24a extending
into the direction of the optical axis O and a second portion 24b
extending parallel thereto, but offset in traverse direction. The
first and second holding portions 24a, 24b are connected by a first
connection portion 26a extending at right angles to both the first
and second holding portions 24a, 24b. The second holding portion
24b is connected to the optical element 16 by a second connecting
portion 26b, also arranged at right angles with both the first and
second holding portions 24a, 24b.
[0047] As shown in FIG. 10a, the first holding portion 10a extends
into the direction of the optical axis O beyond the optical element
16. The second holding portion 24b is arranged at a certain
distance from the first holding portion 24a, but parallel thereto.
The second holding portion 24b, the first connecting portion 26a
and the upper part of the first holding portion 24a form a
loop-like or spring structure on both sides of the optical element
16.
[0048] In a case of increased temperature and severe CTE mismatch
as shown in FIG. 9b, the holder 14 undergoes significant
distortion, but this does not result in substantial changes in the
positioning of the optical element 16. The angular relationship of
the holding portion 24a, 24b and the connecting portions 26a, 26b
may change and compressive stress in traverse direction may be
generated in the optical element 16, but positioning of the optical
element 16 with regard to the optical axis O remains relatively
constant. The spring/loop structure at least partly compensates the
deformation in the first holding portion.
[0049] In the first embodiment of a lighting arrangement 10 shown
in the sectional views of FIG. 4, 5, the holder 14 is comprised of
plane wall elements comprising first (outer) holding portions 24a
which extend straight into the direction of the optical axis O and
second (inner) holding portions 24b arranged spaced therefrom in
parallel. As in the generic embodiment of FIG. 9a, 9b, first
connecting portions 26a are arranged in traverse direction to
connect the first and second holding portions 24a, 24b, and second
connection portions 26b are arranged to connect the second holding
portions 24b to the optical element 16.
[0050] FIG. 7, 8, 11 show alternative embodiments of lighting
arrangements 10, which differ from the lighting arrangement 10
according to the first embodiment by the shape and arrangement of
the first and second holding portions 24a, 24b.
[0051] In the second embodiment according to FIG. 7, the first and
second holding portions 24a, 24b are arranged at an angle of e. g.
30.degree.. In the third embodiment according to FIG. 8, the first
and second holding portions 24a, 24b are connected by a curved
portion.
[0052] In the fourth embodiment according to FIG. 11, there are
further holding portions 24c, 24d extending in parallel into the
direction of the optical axis O besides the first and second
holding portions 24a, 24b. All holding portions 24a-24d are
arranged spaced from each other and are interconnected by
perpendicular connecting portions. The holding portions 24a-24d are
of different length, being shorter the closer they are to the
optical element 16. Thus, a plurality of loop/spring structures is
formed, which in the event of distortion due to CTE mismatch
effectively compensates displacement in the direction of the
optical axis O.
[0053] For a CTE mismatch between the material of the base plate 12
with the material of the holder 14 and optical element 16, all of
the described holding structures show an improved behaviour over
the comparative example of FIG. 10a, 10b. Best results have been
obtained with the holder 14 according to the first embodiment.
[0054] While the invention has been illustrated and described in
detail in the drawings and forgoing description, such illustration
and description are to be considered illustrative or exemplary and
not restrictive; the invention is not limited to the disclosed
embodiments.
[0055] For example, while the above embodiments show a plurality of
LEDs 15 in a line and correspondingly aligned optical elements 16,
embodiments with only a single LED or optical element 16, or with
other arrangements such as two-dimensional matrices of LED's and
corresponding optical elements 16 may be provided. While the holder
14 and optical element 16 in the embodiments are provided as one
piece, to be manufactured e.g. by injection moulding, alternative
embodiments are conceivable with separate parts. Also, as
illustrated by the different shapes shown in FIG. 7, 8, the
specific shape of the first and second holding portions 24a, 24b
may vary as long as at least a portion of both extends into the
direction of the optical axis O, even if it is bent, rounded or
inclined. Other variations to the disclosed embodiment can be
understood and effected by those skilled in the art in practicing
the claimed invention, from a study of the drawings, the disclosure
and the appended claims.
[0056] In the claims, the word "comprising" does not exclude other
elements, and the indefinite article "a" or "an" does not exclude a
plurality.
[0057] The mere fact that certain measures are recited in mutually
different dependent claims or embodiments does not indicate that a
combination of these measures cannot be used to advantage.
[0058] Any reference signs in the claims should not be construed as
limiting the scope.
* * * * *