U.S. patent application number 17/002147 was filed with the patent office on 2021-03-04 for lighting device.
This patent application is currently assigned to Lumileds Holding B.V.. The applicant listed for this patent is Lumileds Holding B.V.. Invention is credited to Floris Maria Hermansz Crompvoets, Barbara Muelders, Benno Spinger.
Application Number | 20210062990 17/002147 |
Document ID | / |
Family ID | 1000005058680 |
Filed Date | 2021-03-04 |
United States Patent
Application |
20210062990 |
Kind Code |
A1 |
Muelders; Barbara ; et
al. |
March 4, 2021 |
Lighting Device
Abstract
A lighting device according to the invention comprises at least
one semiconductor layer; at least one light emission surface
comprising an array of high luminance areas configured to emit
light at a first local luminance level and low luminance areas
configured to emit no light or to emit light at a second local
luminance level lower than the first local luminance level; a
plurality of semiconductor light emitting devices formed in the
semiconductor layer to define the plurality of high luminance
areas; wherein the high luminance areas and the low luminance areas
are arranged in accordance with a predefined light emission profile
of the light emission surface.
Inventors: |
Muelders; Barbara; (Aachen,
DE) ; Crompvoets; Floris Maria Hermansz; (Bunde,
NL) ; Spinger; Benno; (Aachen, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Lumileds Holding B.V. |
Schipol |
|
NL |
|
|
Assignee: |
Lumileds Holding B.V.
Schipol
NL
|
Family ID: |
1000005058680 |
Appl. No.: |
17/002147 |
Filed: |
August 25, 2020 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F21Y 2115/10 20160801;
F21Y 2105/16 20160801; F21S 41/153 20180101; F21K 9/90
20130101 |
International
Class: |
F21S 41/153 20060101
F21S041/153; F21K 9/90 20060101 F21K009/90 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 26, 2019 |
EP |
19193525.3 |
Claims
1. A lighting device comprising: at least one semiconductor layer;
at least one light emission surface comprising an array of high
luminance areas configured to emit light at a first local luminance
level and of at least one low luminance area configured to emit no
light; and a plurality of semiconductor light emitting devices
formed in the semiconductor layer to define the plurality of high
luminance areas, wherein the high luminance areas and the low
luminance areas configured to emit no light are arranged in
accordance with a predefined light emission profile of the light
emission surface and wherein the low luminance area configured to
emit no light corresponds to a portion of the semiconductor layer
comprising an n-doped region and a p-doped region, wherein at least
one of the n-doped region and the a p-doped region is configured
not to be electrically connected to a power source.
2. The lighting device of claim 1, further comprising a plurality
of trenches formed in the at least one semiconductor layer defining
the high luminance areas and the low luminance areas configured to
emit no light.
3. The lighting device of claim 1, wherein the array further
comprises at least one low luminance area configured to emit light
at a second local luminance level lower than the first local
luminance level.
4. The lighting device of claim 3, wherein a low luminance area
configured to emit light at a second local luminance level is
configured to be electrically connected to a power source in
parallel with a further low luminance area configured to emit light
at a second local luminance level and wherein the high luminance
areas are configured to be electrically connected in series to the
power source.
5. The lighting device of claim 1, further comprising first contact
elements respectively arranged in correspondence with the low
luminance areas configured to emit no light and second contact
elements respectively arranged in correspondence with the high
luminance areas and the low luminance area configured to emit light
at a second local luminance level.
6. The lighting device of claim 5, wherein the first contact
elements are configured not to be electrically connected with at
least one of the n-doped region and the p-doped region of
respective low luminance areas configured to emit no light.
7. The lighting device of claim 4, wherein segments of an
insulating layer are respectively interspaced in between the first
contact elements and corresponding low luminance areas configured
to emit no light.
8. The lighting device of claim 1, wherein the high luminance areas
and low luminance areas form a two-dimensional rectangular or
square array.
9. The lighting device of claim 1, wherein the high luminance areas
and the low luminance area configured to emit light at a second
local luminance level correspond to pixels of a matrix light
emitting diode arrangement.
10. The lighting device of claim 1, wherein the predefined light
emission profile is an inhomogeneous light emission profile which
varies in correspondence with a predefined pattern across the light
emission surface.
11. The lighting device of claim 1, wherein the predefined light
emission profile has a maximum at or close to one edge of the light
emission surface, whereby a local luminance level of the light
emission surface decreases towards a minimum at or close to an
opposing edge of the light emission surface.
12. A method of producing a lighting device, the method comprising:
providing at least one semiconductor layer; providing at least one
light emission surface with an array of high luminance areas
configured to emit light at a first local luminance level and low
luminance areas configured to emit no light; forming a plurality of
semiconductor light emitting devices in the semiconductor layer to
define the plurality of high luminance areas; arranging the high
luminance areas and the low luminance areas configured to emit no
light in accordance with a predefined light emission profile of the
light emission surface; arranging first contact elements
respectively in correspondence with the low luminance areas
configured to emit no light and second contact elements
respectively in correspondence with the high luminance areas; and
arranging the first contact elements respectively to be not in
electrical contact with at least one of the n-doped region and the
p-doped region of respective low luminance areas configured to emit
no light.
13. The method of claim 12, further comprising providing low
luminance areas configured to emit light at a second local
luminance level lower than the first local luminance level.
14. An automotive lighting device comprising the lighting device of
claim 1.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of European Patent
Application No. 19193525.3, filed on Aug. 26, 2019, the contents of
which are hereby incorporated by reference herein.
FIELD OF THE INVENTION
[0002] The present disclosure relates to a lighting device
comprising at least one semiconductor layer, and at least one light
emission surface, wherein high luminance areas and low luminance
areas of the light emission surface are arranged in accordance with
a predefined light emission profile.
BACKGROUND OF THE INVENTION
[0003] Lighting devices comprising semiconductor light emitting
devices such as light-emitting diodes (LEDs) may form advantageous
light sources in many fields of applications including hand-held
battery powered devices, such as cameras and cell phones,
automotive applications including automotive head or tail lights,
etc. Semiconductor light emitting devices can be arranged in one or
two-dimensional arrays, where individual semiconductor light
emitting devices act as individual pixels. Examples of such
arrangements include micro LED arrays or matrices (two-dimensional
arrays) typically including pixels with a width of about 100 .mu.m
or less (for example 40 m). Such pixels may for example be
separated by recesses, trenches or gaps with a width of e.g. 20
.mu.m or less (for example 5 .mu.m). An exemplary micro LED array
is disclosed in US 2019/0198564 A1.
[0004] When used for example for automotive headlight applications,
semiconductor light emitting devices are usually combined with
optical elements such as collimating lenses to direct light into
desired directions and to avoid e.g. upward projection of light,
thereby avoiding undesirable glare to oncoming road users.
Headlight beam distributions may be shaped by mapping multiple
luminance images of the light source onto one another (within a
Fourier plane of the optics) using dedicated and specifically
tailored optical elements.
[0005] However, while such optical elements may be tailored to
satisfactory quality, there is still room for improvement.
SUMMARY
[0006] It is an object of the present invention to provide a
lighting device that allows for an improved light emission enabling
improved mapping of light source images for example for automotive
headlight applications. The invention further relates to a method
of producing a lighting device and to a use of a lighting
device.
[0007] According to a first aspect of the present invention a
lighting device is provided comprising at least one semiconductor
layer; at least one light emission surface comprising an array of
high luminance areas configured to emit light at a first local
luminance level and low luminance areas configured to emit no light
and/or to emit light at a second local luminance level lower than
the first local luminance level; a plurality of semiconductor light
emitting devices formed in the semiconductor layer to define the
plurality of high luminance areas; wherein the high luminance areas
and the low luminance areas are arranged in accordance with a
predefined light emission profile of the light emission
surface.
[0008] According to a second aspect of the present invention, a
method of producing a lighting device is provided, the method
comprising: providing at least one semiconductor layer; providing
at least one light emission surface with an array of high luminance
areas configured to emit light at a first local luminance level and
low luminance areas configured to emit no light or to emit light at
a second local luminance level lower than the first local luminance
level; forming a plurality of semiconductor light emitting devices
in the semiconductor layer to define the plurality of high
luminance areas; arranging the high luminance areas and the low
luminance areas in accordance with a predefined light emission
profile of the light emission surface.
[0009] According to a third aspect of the present invention, a use
of a lighting device according to the first aspect for automotive
lighting is provided, in particular for automotive headlight
applications.
[0010] Exemplary embodiments of the first, second and third aspect
of the invention may have one or more of the properties described
below.
[0011] According to an exemplary embodiment, the at least one
semiconductor layer may be a layer, for example an epitaxial layer,
formed on a suitable substrate from a suitable material to emit
photons when excited. Suitable materials include sapphire, GaN, or
silicon. In an exemplary embodiment, the semiconductor layer
comprises an n-type region (a region doped with n-type dopants), a
p-type region (a region doped with p-type dopants) and an active
layer in between the n-type and the p-type region.
[0012] In an exemplary embodiment, a semiconductor light emitting
device (e.g. each of the plurality of semiconductor light emitting
devices) is formed in the semiconductor layer for example by
suitably electrically contacting the n-type region e.g. with an
n-contact formed in a corresponding trench that separates the high
luminance area defined by the semiconductor light emitting device
from a neighboring high luminance area (neighboring semiconductor
light emitting device) or neighboring low luminance area (e.g. a
non-electrically-contacted semiconductor light emitting device or
one of multiple semiconductor light emitting devices connected in
parallel to a power source) and by suitably electrically contacting
the p-type region with a suitable p-contact.
[0013] According to the first aspect, the light emission surface
comprises an array of high luminance areas (e.g. active pixels) and
low luminance areas (e.g. low luminance pixels or inactive pixels).
In an exemplary embodiment, the high luminance areas respectively
correspond to light emitting surfaces of corresponding
semiconductor light emitting devices. Further, in the exemplary
embodiment, the low luminance areas may respectively correspond to
surfaces of corresponding semiconductor light emitting devices that
are not electrically connected (not connectable) to a power source
and/or that are connected in parallel to a power source. In the
latter case, by electrically connecting the respective
semiconductor light emitting devices in parallel, while connecting
the semiconductor light emitting devices of the high luminance
areas in series, a luminance of the low luminance areas may be
adjusted to be considerably lower (e.g. equal to or close to zero)
as compared to the high luminance areas. In other words, the first
local luminance level of the high luminance areas is in an
exemplary embodiment considerably higher than the second local
luminance level of the low luminance areas. In a preferred
embodiment, the first local luminance level of the high luminance
areas is higher than the second local luminance level of the low
luminance areas at least by a factor of 3 to 10, e.g. by a factor
selected from the group of factors 3, 4, 5, 6, 7, 8, 9, 10. Given
the difference in luminance, by arranging the high luminance areas
and the low luminance areas in accordance with a predefined light
emission profile, it becomes possible to advantageously tailor a
light emission profile for example of a light source used in an
automotive headlight. Thus, a lighting device according to the
first aspect of the present invention advantageously allows to
tailor a light emission pattern by arranging high and low luminance
areas and thus allows to optimize emission characteristics of a
corresponding light source in accordance with a given application.
For example, it becomes possible to tailor the emission
characteristics to be optimized for automotive headlight
applications where for example an upward projection of light is to
be avoided in order to prevent undesirable glare to oncoming road
users. While thus, use of a light source with improved emission
profile according to the first aspect may even further improve
quality and efficiency using existing optical elements, at the same
time, a quality requirement regarding the used optical elements may
be moderated such that suitable results may be achieved even with
optical elements of lower quality and cost.
[0014] In an exemplary embodiment, the array of high luminance
areas and low luminance areas comprises low luminance areas
configured to emit no light and low luminance areas configured to
emit light at a second local luminance level lower than the first
local luminance level. For example, by providing low luminance
areas configured to emit light at a second local luminance level at
a transition between high luminance areas and low luminance areas
configured to emit no light, a smooth luminance transition can be
generated which in some applications may support a an advantageous
image in a corresponding Fourier plane.
[0015] In an exemplary embodiment, the lighting device according to
the first aspect further comprises a plurality of trenches (or
recesses or gaps) formed in the at least one semiconductor layer
defining or separating the high luminance areas and the low
luminance areas. Such trenches may for example be formed by
suitable etching techniques and may be formed partially into or
completely through the semiconductor layer. Such trenches are
advantageous in that they allow to provide a clear separation
between individual high luminance areas (active pixels) and
individual low luminance areas (low luminance or inactive
pixels).
[0016] In an exemplary embodiment, a low luminance area of the low
luminance areas (e.g. each of the low luminance areas) corresponds
to a portion of the semiconductor layer comprising an n-doped
region and a p-doped region, wherein at least one of the n-doped
region and the p-doped region is configured not to be electrically
connected to a power source. In other words, the n-doped region
and/or the p-doped region is not connectable to a power source such
that the corresponding low luminance area corresponds to a
permanently inactive pixel configured to not emit light. Likewise,
in an exemplary embodiment, a high luminance area (e.g. each of the
high luminance areas) corresponds to a portion of the semiconductor
layer comprising an n-doped region and a p-doped region, wherein
both the n-doped region and the p-doped region are electrically
connectable to a power source. In other words, the high luminance
areas (active pixels) can be turned on and off by connecting the
same to the power source, while in this embodiment, the low
luminance areas (inactive pixels) cannot be turned on.
[0017] In an exemplary embodiment, a low luminance area of the low
luminance areas (e.g. each of the low luminance areas) is
configured to be electrically connected (e.g. is electrically
connected) in parallel with a further low luminance area of the low
luminance areas to a power source, and wherein the high luminance
areas are configured to be electrically connected (e.g. are
electrically connected) in series to the power source. While in
this embodiment, it may be possible to electrically connect the low
luminance areas to a power source, by connecting the parallel
connection of the low luminance areas allows to keep a local
luminance level (the second local luminance level) emitted from
these pixels considerably lower than the first local luminance
level of the high luminance areas. As mentioned, in an exemplary
embodiment, the second local luminance level is lower than the
first local luminance level at least by a factor of 3 to 10.
[0018] In an exemplary embodiment, the lighting device further
comprises first contact elements (in particular an array of first
contact elements) respectively arranged in correspondence (in
particular in a one-to-one correspondence) with the low luminance
areas (in particular in direct or indirect mechanical contact
therewith) and second contact elements (in particular an array of
second contact elements) respectively arranged in correspondence
(in particular in a one-to-one correspondence) with the high
luminance areas (in particular in direct or indirect mechanical
contact therewith). In other words, even in embodiments in which
the low luminance areas are not connectable to a power source, in
particular the second contact elements are provided e.g. in direct
or indirect mechanical contact with the low luminance areas. For
example, the first and second contact elements may correspond to
respective segments of a segmented conductivity layer arranged in
mechanical contact with the lighting device. It was found that
providing the first and second contact elements irrespective of
whether or not the low luminance areas are connectable with a power
source, the provision of the first and second contact elements
advantageously supports structural integrity of the lighting
device.
[0019] In an exemplary embodiment, the first contact elements and
the second contact elements are arranged as an array in
correspondence with the array of high luminance areas and low
luminance areas. In particular in this form, the first and second
contact elements help to advantageously support structural
integrity of the lighting device.
[0020] In an exemplary embodiment, the first contact elements are
configured not to be electrically connected with at least one of
the n-doped region and the p-doped region of respective low
luminance areas. In this embodiment, the low luminance areas are
not configured to emit light thus providing a most noticeable
difference in luminance level as compared to the luminance level of
the high luminance areas.
[0021] In an exemplary embodiment, segments of an insulating layer
are respectively interspaced in between the first contact elements
and corresponding low luminance areas. For example, the insulating
layer may comprise a dielectric material, e.g. SiO.sub.2,
configured to inhibit an electrical connection between the first
contact elements and the corresponding low luminance areas. In an
exemplary embodiment, each of the low luminance areas is in direct
mechanical contact with a corresponding segment of the insulating
layer, the corresponding segment of the insulating layer being in
direct mechanical contact with a corresponding first contact
element.
[0022] In an exemplary embodiment, the high luminance areas and low
luminance areas form a two-dimensional rectangular or square array.
In this embodiment, the lighting device may advantageously employed
in applications using for example matrix light emitting device,
LED, arrangements to replace conventional matrix LED arrangements
by an inventive lighting device with suitably tailored light
emission or local luminance profile.
[0023] In an exemplary embodiment, the high luminance areas
correspond to pixels of a matrix light emitting diode arrangement.
In this embodiment, the lighting device may correspond to a matrix
LED arrangement with active pixels, inactive pixels and/or low
luminance pixels, where the high luminance areas correspond to the
active pixels and the low luminance areas correspond to the
inactive and/or low luminance pixels. As mentioned the provision of
such matrix arrangement is advantageous in particular in
applications already employing matrix LED arrangements which can be
easily replaced, whereby the replacement does not require
modifications to a remaining system which is advantageous in terms
of cost and complexity.
[0024] In an exemplary embodiment, the predefined light emission
profile is an inhomogeneous light emission profile which varies (in
particular spatially, e.g. across the light emission surface) in
correspondence with a predefined pattern across the light emission
surface. The predefined pattern may be determined in accordance
with a given application to optimize a light source emission
profile e.g. based on existing optics. In an exemplary embodiment,
the predefined light emission profile has a maximum at or close to
one edge of the light emission surface, whereby a local luminance
level of the light emission surface decreases towards a minimum at
or close to an opposing edge of the light emission surface.
[0025] The latter light emission profile turned out to be in
particular advantageous for automotive headlight applications. With
the high luminance edge of the lighting device being oriented
upwards (away from a ground on which a car using the lighting
device is places), the lighting device emits light according to an
inhomogeneous pattern which, in combination with typical headlight
optics helps to prevent upward projection of light to prevent
undesirable glare to oncoming road users.
[0026] It is noted that while the lighting device according to the
invention may be advantageously applicable in automotive
applications, further applications where an inhomogeneous emission
profile is of advantage include projection systems, hand-held
battery powered devices, cameras, cell phones, camera flash lights,
spot lights, etc.
[0027] The features and example embodiments of the invention
described above may equally pertain to the different aspects
according to the present invention. In particular, with the
disclosure of features relating to the lighting device according to
the first aspect, also corresponding features relating to a method
of producing a lighting device according to the second aspect and
to the use according to the third aspect are disclosed.
[0028] It is to be understood that the presentation of embodiments
of the invention in this section is merely exemplary and
non-limiting.
[0029] Other features of the present invention will become apparent
from the following detailed description considered in conjunction
with the accompanying drawings. It is to be understood, however,
that the drawings are designed solely for purposes of illustration
and not as a definition of the limits of the invention, for which
reference should be made to the appended claims. It should be
further understood that the drawings are not drawn to scale and are
merely intended to conceptually illustrate the structures and
procedures described herein.
BRIEF DESCRIPTION OF THE DRAWINGS
[0030] Exemplary embodiments will now be described in detail with
reference to the accompanying drawings, in which:
[0031] FIG. 1 shows exemplary stages of a process of producing a
lighting device according to an exemplary embodiment;
[0032] FIG. 2 shows a plan view of a light emission surface of a
lighting device according to an exemplary embodiment;
[0033] FIG. 3 shows part of a plan view of a light emission surface
of a lighting device according to an exemplary embodiment;
[0034] FIG. 4 shows an example of a light emission surface of a
lighting device according to an exemplary embodiment; and
[0035] FIG. 5 shows an intensity distribution within a Fourier
plane resulting from a light emission profile of a lighting device
according to an exemplary embodiment.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0036] FIG. 1 shows exemplary stages A to C of a process of
producing a lighting device 100 according to an exemplary
embodiment.
[0037] At stage A, an epitaxial layer 120 (an example of a
semiconductor layer), for example comprising or consisting of GaN,
is provided on a substrate 110. In further examples, epitaxial or
semiconductor layer 120 may comprise or consist of InGaN and/or
AlInGaP. Segments of a p-conductivity layer 130 are provided on
epitaxial layer 120. While p-conductivity layer 130 is shown as a
single layer, one or more layers may be formed as suitable
conductivity region, e.g. depending on used materials and
application. In the shown example, the substrate 110 is a patterned
sapphire substrate (PSS) and the p-conductivity layer may be an
aluminum layer, the corresponding segments formed in contact with a
p-doped region of epitaxial layer 120. It is noted that the
polarity of regions (e.g. layers) of epitaxial/semiconductor layer
120 is exemplary and can be reversed e.g. depending on material or
application.
[0038] At stage B in FIG. 1, trench 125 is formed in epitaxial
layer 120 e.g. using a suitable etching process and/or masking
process. A depth of trench 125 is adjusted such that bottom of
trench 125 reaches an n-doped region (or layer) of epitaxial layer
120. As can be taken from the figure, a corresponding trench is not
formed in a portion of epitaxial layer 120 to the right of line
510, i.e. in a pixel portion of epitaxial layer 120 corresponding
to a low luminance area (inactive pixel) of a light emission
surface 101 of lighting device 101. It is noted that line 510 used
in FIG. 1 merely illustrates the corresponding principle and does
not necessarily imply a technical barrier within semiconductor
layer 120 exactly at the indicated position.
[0039] Further at stage B in FIG. 1, a dielectric layer 150 (an
example of an insulating layer) is provided on epitaxial layer 120,
in the shown example on and in contact with conductivity layer 130.
Dielectric layer 150 may for example be a 200 nm thick layer of
SiN. As can be taken from the figure, dielectric layer 150 serves
to provide insulation at predefined portions over epitaxial layer
120. While dielectric layer 150 is not provided in regions 126 and
127 within the pixel portion (active pixel portion) to the left of
line 510 in FIG. 1B to keep conductivity layer 130 in direct
contact with the p-portion of epitaxial layer 120 exposed, the
corresponding electrically conductive layer 130 of the pixel
portion (inactive pixel portion) to the right of line 510 in FIG.
1B is fully covered by insulating dielectric layer 150. In this
way, the p-doped region of epitaxial layer 120 within the inactive
pixel portion is configured not to be electrically connected (is
not connectable) to a power source.
[0040] At stage C in FIG. 1, a layer 160 of electrical contact
material (e.g. of gold or copper) is provided on epitaxial layer
120, in particular on portions of dielectric layer 150 and on the
exposed portions of conductivity layer 130. In this way, p-contact
element 160a and n-contact element 160b are formed in the active
pixel region to the left of line 510, which are respectively in
electrical contact with the p-doped region and the n-doped region
of epitaxial layer 120. Thus, the corresponding n-doped region and
p-doped region of epitaxial layer 120 are configured to be
connected with an electrical power source to cause an active region
between the n-doped region and the p-doped region to emit light.
Conversely, contact elements 160c and 160d provided in mechanical
contact with the inactive pixel region (with insulating layer 150)
to the right of line 510 are not in electrical contact with
epitaxial layer 120, which is thus not connectable to a power
source and is configured not to emit light. It turned out that by
nevertheless providing contact elements 160c and 160d on a surface
of the inactive pixel region, structural integrity of the overall
lighting device can be advantageously improved.
[0041] It is noted that while in the example of FIG. 1, layer 130
is provided on epitaxial layer 120 also in the inactive pixel
region to the right of line 510, for example respective masks used
when depositing the respective layers upon fabricating the lighting
device may be adjusted such that in exemplary embodiments, no
electrically conductive layers are provided within low luminance
areas such as the inactive pixel region of FIG. 1. Such embodiment
is advantageous in terms of material efficiency and helps to save
costs.
[0042] In a further exemplary embodiment, alternatively or in
addition, no insulating layer such as dielectric layer 150 is
provided within low luminance areas such as the inactive pixel
region of FIG. 1. While in this embodiment, contact elements 160c
and 160d may be in electrical contact with the epitaxial layer 120,
contact elements 160c and 160d are both in electrical contact only
with a single region of epitaxial layer 120 of a same polarity (in
the example of FIG. 1 a p-doped region). Thus, also in this
embodiment, contact elements 160c and 160d are thus configured not
to be electrically connected with at least one of the n-doped
region and the p-doped region of respective low luminance areas, in
this example are not configured to be connected with the n-doped
region.
[0043] It is further noted that at a stage following stage C in
FIG. 1 (not illustrated), substrate 110 may be removed and may e.g.
be replaced by a wavelength conversion layer, e.g. a phosphor layer
to convert part of light emitted from semiconductor layer 120 into
a suitable different wavelength e.g. to achieve a desired light
color of the lighting device. Thus, either a surface of such
wavelength conversion layer, a surface of substrate 110 (a lower
surface in FIG. 1) or a surface of a different layer provided on or
instead of substrate 110 forms part of light emission surface
101.
[0044] As a result, the lighting device 100 shown at stage C of
FIG. 1 has a light emission surface 101 comprising a high luminance
area formed by a light emission surface of the semiconductor light
emitting device (the active pixel) to the left of line 510 in FIG.
1 and a low luminance area formed by the electrically
non-connectable portion of semiconductor layer 120 to the right of
line 510 in FIG. 1.
[0045] It is noted that in an alternative embodiment (not
illustrated), a low luminance area may be achieved by providing the
portion to the right of line 510 similar to the portion to the left
of line 510, whereby in this embodiment, contact elements connected
to the portion to the left of line 510 are connected in series with
contact elements of similar portions (not shown in the simplified
figure), while contact elements connected to the portion to the
right of line 510 are connected in parallel with contact elements
of similar portions (not shown in the simplified figure). In this
way, corresponding low luminance areas may only emit light at a
lower luminance (e.g. lower by a factor of 3 to 10) as compared to
the active pixels that are connected in series to the power source.
Such pixels of reduced luminance may be provided in addition or
alternatively to inactive pixels in a light emitting device. For
example, such pixels of reduced local luminance may be provided in
between active pixels and inactive pixels to achieve a smooth local
luminance transition at the light emission surface 101.
Accordingly, a corresponding intensity distribution within a
Fourier plane of corresponding optics may be improved.
[0046] FIG. 2 shows a plan view of light emission surface 101 of
lighting device 100. As can be taken from this figure, pixels 105
form a matrix arrangement where each pixel corresponds to a high
luminance area (such pixel e.g. corresponding to a semiconductor
light emitting device of semiconductor light emitting devices
connected in series to a power source) or to a low luminance area
(such pixel e.g. corresponding to a semiconductor light emitting
device of semiconductor light emitting devices connected in
parallel to a power source, or to a portion of a semiconductor not
or only partially connectable to a power source).
[0047] As conceptually illustrated in FIG. 3, which shows part of a
plan view of a light emission surface 101 of a lighting device 100,
it thus becomes possible to tailor desired light emission profiles
of a light emission surface 101 by arranging high luminance areas
105b and low luminance areas 105a in accordance with a predefined
pattern across the light emission surface 101.
[0048] FIG. 4 shows an example of a light emission surface 101 of a
lighting device 100, where such predefined light emission profile
has a maximum at or close to an upper edge of the light emission
surface 101. As illustrated by the density of dots in the figure
and the accompanying emission intensity (or local luminance)
profile 503, a local luminance level of the light emission surface
101 decreases towards a minimum at or close to a lower edge of the
light emission surface 101. Such intensity profile is in particular
advantageous for applications in the automotive field, in
particular for automotive headlights as in combination with typical
headlight optics, it helps to avoid undesirably upwardly projecting
light beams.
[0049] FIG. 5 illustrates an intensity distribution within a
Fourier plane resulting from a light emission profile 503 of the
lighting device 100 according to an exemplary embodiment. Hereby, a
density of dots in the figure conceptually illustrates the
corresponding magnitude of light intensity as also shown in the
corresponding scale in arbitrary units. Contour lines 600 to 604
respectively indicate corresponding levels of light intensity
within the Fourier plane. As can be taken from FIG. 5, a lighting
device 100 with a light emission surface 101 with this light
emission profile enables an intensity distribution within the
Fourier plane (of optics typically used for automotive headlights)
which is more concentrated towards an upper edge while avoiding
disturbing upwardly projecting beams and disturbing sidewards
projecting beams.
LIST OF REFERENCE SIGNS
[0050] 100 Lighting device [0051] 101 Light emission surface [0052]
105 High/low luminance area (Pixel) [0053] 105a Low luminance area
[0054] 105b High luminance area [0055] 110 Substrate [0056] 120
Semiconductor/epitaxial layer [0057] 125 Trench [0058] 126 Exposed
region [0059] 127 Exposed region [0060] 130 Conductivity layer
[0061] 150 Dielectric layer [0062] 160 Contact layer [0063] 160a
p-contact element [0064] 160b n-contact element [0065] 160c Contact
element [0066] 160d Contact element [0067] 503 Emission intensity
profile [0068] 510 Line [0069] 600-604 Light intensity within the
Fourier plane
* * * * *