U.S. patent application number 10/766988 was filed with the patent office on 2004-12-16 for method of providing modulated illumination of a road, and a vehicle headlight for performing the said method.
Invention is credited to Albou, Pierre, Brun, Norbert, De Lamberterie, Antoine, Leleve, Joel.
Application Number | 20040252516 10/766988 |
Document ID | / |
Family ID | 32605968 |
Filed Date | 2004-12-16 |
United States Patent
Application |
20040252516 |
Kind Code |
A1 |
Brun, Norbert ; et
al. |
December 16, 2004 |
Method of providing modulated illumination of a road, and a vehicle
headlight for performing the said method
Abstract
The invention relates to a method of lighting a road with a
vehicle headlight, in which the projected light is modulated in
response to the presence of any persons on the road. The method
comprises the following operations: detecting in the road scene at
least one person, pinpointing the location of the person in the
road scene, creating on an imager a mask having dimensions and
position corresponding to the person, and lighting the road through
the imager, to create a projected shadow around the person. The
invention also provides a headlight for performing this method and
having a first light source, an imager, a light guide for carrying
the light from the light source towards the imager, and an
electronic system for generating light-occulting masks on the
imager.
Inventors: |
Brun, Norbert; (Guermantes,
FR) ; Albou, Pierre; (Paris, FR) ; De
Lamberterie, Antoine; (Paris, FR) ; Leleve, Joel;
(Epinay Sur Seine, FR) |
Correspondence
Address: |
MORGAN & FINNEGAN, L.L.P.
3 WORLD FINANCIAL CENTER
NEW YORK
NY
10281-2101
US
|
Family ID: |
32605968 |
Appl. No.: |
10/766988 |
Filed: |
January 28, 2004 |
Current U.S.
Class: |
362/465 |
Current CPC
Class: |
G02B 26/005 20130101;
B60Q 1/0011 20130101; B60Q 2300/334 20130101; B60Q 2300/054
20130101; B60Q 2300/312 20130101; B60Q 1/085 20130101; B60Q 2300/45
20130101 |
Class at
Publication: |
362/465 |
International
Class: |
B60Q 001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 30, 2003 |
FR |
0301083 |
Claims
What is claimed is:
1. A method of lighting a road scene with a vehicle headlight,
including the following operations: detecting in the road scene at
least one person, pinpointing the location of this person in the
road scene, creating, on an imager, a mask having dimensions and
position corresponding to the person, and illuminating the road
through the imager, so creating a projected shadow around the
person.
2. A method of lighting according to claim 1 which illuminates a
zone of the road scene situated above a cut-off line.
3. A method of lighting according to claim 1, wherein the detection
of the person comprises taking an image of the road scene with
thermal detection of the person.
4. A method of lighting according to claim 1, wherein detection of
the person comprises taking an image of the road scene with
detection of movement of the person.
5. A method of lighting according to claim 1, wherein the
pinpointing of location, and mask creation, are obtained by image
processing.
6. A method of lighting according to claim 1, wherein the
pinpointing of location consists in applying a threshold-value
technique to the image of the road scene.
7. A method of lighting according to claim 6, wherein the
application of threshold value comprises forming an image at two
levels, black and white, of the image of the road scene.
8. A method of lighting according to claim 7, wherein the creation
of the mask comprises applying, in inverse video on the imager, the
image to which the threshold-value technique has been applied.
9. A method of lighting according to claim 6, wherein the creation
of the mask includes convolution, by means of a convoluting
element, of the image to which the threshold-value technique has
been applied.
10. A method of lighting according to claim 1, wherein creation of
the mask is performed in real time.
11. A main beam headlight for a vehicle, comprising a first light
source and a system for modulating the light therefrom, wherein the
modulating system comprises an imager, a light guide for
transporting the light from the light source to the imager, and an
electronic system for generating masks on the imager for blocking
light.
12. A headlight according to claim 11, wherein the imager comprises
a matrix of liquid crystal systems which are electrically
controllable, or a matrix of lenses, the focal length of which is
capable of being modulated by electrical control.
13. A headlight according to claim 11, wherein the light guide
comprises at least one matrix of optical fibres or an optical fibre
of large cross section.
14. A headlight according to claim 11, wherein the light guide
comprises a first light path for guiding the light towards the
imager, and a second light path for guiding the light towards an
optic adapted for diffusing the light.
15. A main beam headlight for a vehicle, comprising a first light
source and a system for modulating the light therefrom, wherein the
modulating system comprises an imager comprising a matrix of
lenses, the focal length of which is able to be modulated by
electrical control, and an electronic system for generating masks
on the imager for blocking light.
16. A headlight according to claim 11, including a second light
source independent of the first light source and providing main
beam or cruising illumination.
17. A headlight according to claim 11, wherein the electronic
system is controlled by a means for detecting persons.
18. A headlight according to claim 17, wherein the detection means
is a thermal camera.
19. A headlight according to claim 17, wherein the detection means
is an infrared camera.
20. A headlight according to claim 11, wherein the light guide
includes, upstream of the imager, means for making the distribution
of the light in the imager homogeneous.
21. A headlight according to claim 20, wherein the means for making
the light homogeneous is a block or bar of quartz or glass.
22. A headlight according to claim 11, including a lens for
diffusing the light downstream of the imager.
23. A headlight according to claim 11, wherein the first light
source is located in a housing outside the modulating system.
Description
FIELD OF THE INVENTION
[0001] This invention relates to a method of lighting a road, in
which the light projected is modulated according to the presence of
one or more living beings in the road scene which appears ahead of
the vehicle. The invention also relates to a vehicle headlight for
performing the said lighting method.
[0002] The invention is applicable in the field of vehicles
travelling on roads, such as, for example, motor vehicles or heavy
goods vehicles. In particular, it is applicable in the field of
projection of light by such vehicles.
STATE OF THE ART
[0003] In view of the great number of vehicles travelling on the
roads, it is necessary to obtain, for these vehicles and their
drivers, lighting which is adapted in the best possible way to
reduce the risks of accidents. In particular, at night it is
important that the driver should be able to have optimum vision of
the road that extends in front of him, as well as the areas to
either side of the road. In other words, for safety reasons it is
desirable to improve lighting of the road ahead of the vehicle, and
therefore to improve the vision of the road scene by the driver of
the vehicle.
[0004] At the present time, all vehicles travelling on the road
have a means for lighting the road which is used in particular at
night or in bad weather. There exist conventionally on motor
vehicles two types of lighting:
[0005] so-called main beam or cruising lighting, which illuminates
the road comprehensively over a long distance, of about 200 metres,
which is considered as being infinity for the driver, and
[0006] so-called dipped beam or passing lighting, which illuminates
the road over a short distance of the order of 60 metres, so as to
avoid dazzling of people who may be situated on the road or in
roadside areas.
[0007] Main beam lighting is obtained by means of main beam
headlights each of which delivers a light beam which is directed
towards the horizon.
[0008] Passing or dipped beam lighting is obtained by means of
passing headlights, also called dipped headlights, each of which
directs a sheet of light downwards so as to give visibility over a
distance of the order of 60 to 80 metres. This patch of descending
light has the object of avoiding dazzling of anybody, on foot or in
a vehicle travelling in the opposite direction, who may be within
the road scene which extends ahead of the is vehicle. However, such
a patch of downwardly directed light offers only reduced visibility
to the driver of the vehicle ahead of the vehicle. This lighting is
often insufficient to enable the driver to have good visibility of
the whole of the road scene in order that he is able to anticipate
any bends or any possible obstacles.
[0009] On the other hand, main beam lighting enables the road ahead
of the vehicle to be lit as far as the horizon. For this purpose,
main beam lighting delivers a light beam which is directed towards
the horizon, that is to say it extends straight in front of the
vehicle, and this does not fail to dazzle those people who are on
the road or on the roadside areas, because they receive the light
head-on.
[0010] At the present time, there is no known device which enables
the road to be lit to infinity or over a long distance without
dazzling people who are on the road.
[0011] However, there does exist a headlight which enables the main
lighting beam of the vehicle to be modulated on the road. Such a
headlight is described in patent applications DE 199 07943 and U.S.
Pat. No. 5,938,319. This headlight enables there to be projected on
the road a light indication such as an arrow, in order to indicate
for example the direction that the driver must follow. This
indication is then lit while the zone that surrounds it is dark,
that is to say it is unlit. Such a light indication is produced by
means of a headlight which includes a plurality of micromirrors
having dimensions of the order of one tenth or one hundredth of a
millimetre. In other words, the headlight enables the light
projected on the road to be modulated. However, it only permits
modulation of the light over part of the main beam. It does not
permit control of the modulation of the whole of the light beam
emitted by a conventional main beam lighting system.
[0012] In addition, such a headlight is very expensive to
manufacture, its cost being of the order of one half of the price
of the whole vehicle. It is therefore difficult to envisage that
such headlights would be fitted on mass-produced motor vehicles,
for which the manufacturers are constantly seeking to reduce
manufacturing costs.
[0013] Another motor car headlight with light modulation is
described in patent application EP 0 266 908. This headlight with
modulated light has the object of enabling dipped beam or main beam
lighting to be obtained with only a single light source. To this
end, it includes, between a reflector and a single light source, an
occulting screen which is interposed in the path of the light rays
and which includes occulting zones consisting of liquid crystals,
which are adapted to confer on these zones several states of
transparency. Thus where lighting is in the main beam mode, the
occulting screen is totally transparent, enabling the whole of the
light beam to be projected on the road. In the passing beam mode,
the occulting screen is partly occulting, thereby enabling only a
part of the light beam emitted by the light source to be projected,
and in particular the part which is situated below a line of the
illumination pattern which is called the "cut-off line" and which
is defined by a regulation. This cut-off line is a line defining an
upper limit of the lighting, above which it is forbidden to
transmit light in the passing or dipped beam mode. In countries
where they drive on the right, it is horizontal over the whole
width of the road and on the roadside area to the left of the road,
and it defines an angle of 15.degree. above the horizontal on the
right hand roadside area.
[0014] However, in practice such a headlight cannot be achieved. In
this connection, a liquid crystal occulting screen such as that
described in the said patent application is very sensitive to
received energy, and in particular to the temperature to which it
is subjected. Thus, a liquid crystal occulting screen subjected to
energy which is too powerful is necessarily faulty. Now, the light
source used for main beam lighting is a powerful light source, too
powerful for a liquid crystal occulting screen to be able to resist
it physically.
DISCUSSION OF THE INVENTION
[0015] More precisely, an object of the invention is to provide a
remedy for the drawbacks of the techniques discussed above. To this
end it proposes a headlight for a vehicle, for dipped or passing
beam illumination, in which the light is modulated in response to
the presence of any persons who may be on the road. The invention
also proposes a method of lighting which is performed by such a
headlight. The said lighting method has the object of detecting
persons and other living beings who are in the road scene, to
create a screen which corresponds to those persons both in
dimension and in position, and to illuminate the road with this
screen in such a way that a projected shadow is created all around
the person. The person is thus within the shadow of the screen, so
that the shadow covers the whole of the person, and possibly
somewhat more: the shadow may have the shape and/or contours of the
person, or it may extend slightly beyond the outline of the person
for greater safety.
[0016] More precisely, the invention provides a method of lighting
a road scene with a vehicle headlight, characterised in that it
includes the following operations:
[0017] detecting in the road scene at least one person,
[0018] pinpointing the location of this person in the road
scene,
[0019] creating, on an imager, a mask having dimensions and
position corresponding to the person, and
[0020] illuminating the road through the imager, so creating a
projected shadow around the person.
[0021] Preferably, the method is applied to a zone of the road
scene situated above a cut-off line.
[0022] The invention also provides a headlight which performs this
method. This main beam headlight for a vehicle, comprises a first
light source and a system for modulating the light therefrom, and
is characterised by the fact that the modulating system comprises
an imager, a light guide for transporting the light from the light
source to the imager, and an electronic system for generating masks
on the imager for blocking light.
[0023] The invention proposes two variants, which are however not
limiting as regards choice of the imager: the imager may comprise a
matrix or a set of electrically controllable liquid crystal
systems. It may also comprise a matrix or set of lenses, the focal
length of which is capable of being modulated by electrical
control. This type of lens is described in particular in patent
application EP 1 019 758, and its operation is based on the
phenomenon of electro-wetting. Generally, each of these lenses
comprises a chamber filled with a first liquid, a drop of a second
liquid being disposed on a zone of a first face of an insulating
wall of the chamber, the two liquids being non-miscible and having
different optical indices and similar densities. The first liquid
is conductive, the second insulating, and means are employed to
apply an electrical voltage between the conductive liquid and an
electrode which is disposed on the second face of the said wall.
Reference should be made to the above mentioned patent for more
details. Within the scope of the present invention, the focal
length is adjusted by applying the appropriate voltage for the lens
to allow all or part of the light to pass, or no light at all.
[0024] This electrically controllable type of lens may preferably
be used in a matrix or by itself in numerous applications in
headlights or indicating lights for motor vehicles.
[0025] The headlight according to the invention is preferably
associated with a camera, for example a thermal camera, which
controls the electronic system.
BRIEF DESCRIPTION OF THE DRAWINGS
[0026] FIG. 1 shows diagrammatically a road illuminated by
conventional cruising lighting combined with lighting according to
the invention.
[0027] FIG. 2 shows the various elements constituting a headlight
according to the invention, controlled by a camera.
[0028] FIG. 3 shows a first embodiment of the optical system of the
headlight of the invention.
[0029] FIG. 4 shows an imager in the headlight of the
invention.
[0030] FIG. 5 shows a second embodiment of the optical system of
the headlight of the invention.
[0031] FIGS. 6 to 9 illustrate a third embodiment of the invention,
which makes use of an imager which employs lenses, the focal length
of which is adjustable by electrical control.
DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION
[0032] The invention proposes a method for illuminating a road
scene, as a complementary addition to conventional main beam or
cruising lighting. This method offers an extent of lighting which
is greater than for the usual cruising type lighting, without any
risk of dazzling people situated on the road or on roadside
areas.
[0033] To this end, the method of the invention proposes to
illuminate the road above the cut-off line by generating a
projected shadow around the person or persons who happen to be in
the said zone. This projected shadow is generated by forming, for
example on a liquid crystal imager, a mask corresponding to the
position and dimension of the person, and covering a zone of the
imager such that a part of the light beam emitted by a light source
does not pass through the imager and is not projected on the road.
The mask thus created enables a projected shadow to be formed
around the person while the road scene is being illuminated beyond
the cut-off line. The projected shadow corresponds to the
silhouette of the person. It may correspond exactly to their
silhouette, or it may include a zone surrounding their silhouette.
In the present case, the use of a liquid crystal imager is possible
without any danger of premature deterioration of the liquid
crystals, because the optical system employed is preferably not an
elliptical module. It is effectively in elliptical modules that the
danger of heating is greatest, because it needs a lens which
creates a point of convergence of the rays reflected by the
reflector, thereby producing a hot point within the headlight.
[0034] FIG. 1 shows one example of a road scene. In this example,
the road is referenced R. It has a left-hand roadside area BC1 and
a right-hand roadside area BC2. A first person P1 is on the
right-hand area beside the road. He is situated in the zone of
usual illumination by a main beam, namely zone H, that is to say
the zone of illumination situated below the cut-off line C. He is
not dazzled by the main beam lighting emitted by the headlights of
the vehicle. A second person P2 is situated in the zone of
illumination above the cut-off line C, indicated as zone 1, that is
to say the zone of the road scene which is lit by the headlight of
the invention.
[0035] This zone is lit above the cut-off line by a beam which is
additional to that from a standard main beam light. This additional
beam is generally quite wide, its intensity being of a mean value
with respect to an ordinary cruising beam (for example 5 to 30 lux,
or 10 to 20 lux intensity, as compared to intensity of the order of
40 to 80 lux for a standard cruising beam), and it has a range
which is for example of the order of 50 to 80 metres. It is
conventionally designated by the term "complementary main beam" or
"ambient main beam".
[0036] The person P2 who is situated in the zone of lighting
extending to infinity is surrounded by a projected shadow OP which
enables him to avoid being dazzled.
[0037] In general terms, in the invention, all the living beings
who are situated within the road scene are detected, whether they
are humans or animals. As will be seen later herein, this detection
can for example be obtained by temperature difference, or by
detecting movements. In general terms, the term "person" is used
herein to mean every living being detectable according to the
invention.
[0038] FIG. 2 shows functionally the headlight of the invention
with one example of illumination of the road scene. The example of
road scene in FIG. 2 shows the person P2 with a projected shadow OP
around him, in the lighting zone 1. The projected shadow OP is
created by means of an optical system 1 associated with a person
detection system 2 and an electronic image processing system 3. The
optical system 1 and the electronic image processing system 3
together constitute a system for modulating the light emitted by a
light source 10.
[0039] In accordance with the invention, the person detection
system 2 may be a camera, for example a thermal camera, which takes
images of the road scene situated in front of the vehicle. These
images of the road scene, which are called natural images, are
transferred to the electronic system 3 as indicated
diagrammatically by the arrow 4, and the latter then carries out
electronic processing of these images. This processing enables the
position of the person P2 in the road scene to be pinpointed. As
will be seen later herein, the image processing also enables a
mask, or light trap, to be created on the imager 12 of the optical
system 1. This mask is transmitted to the imager 12, as indicated
diagrammatically by the arrow 5. When the light source 10 is
emitting a light beam, this beam is directed towards the imager 12
by means of a light guide 11. The zones of the imager 12 which
constitute the screen are opaque and do not allow light to pass
through. On the other hand, the zones of the imager 12 which do not
include the mask are transparent to light; the light beam emitted
by the source 10 then passes through the imager and is projected
outside the headlight, that is to say on the road scene. The mask
which is produced on the imager 12 prevents the light beam from
passing through, which generates a projected shadow OP about the
person P2.
[0040] As described above, the method is carried out in real
time.
[0041] FIG. 2 shows the electronic system 3 and the optical system
1 as being independent of each other. In practice, the electronic
system 3 may be incorporated within the optical system 1, as will
be understood from the description below.
[0042] FIG. 3 shows one embodiment of the optical system 1 for the
headlight according to the invention. This optical system 1
comprises a light generator or light source 10. This light source
10 may for example be a discharge lamp or an elliptical source,
such as a xenon lamp such as is conventionally found in current
vehicles. The light source 10 is connected to the imager 12 through
a light guide 11. The light guide may be an optical fibre of large
cross section. The guide may also, as in the preferred embodiment
of the invention, be a matrix of optical fibres carrying the light
from the light source to the imager 12. The light guide may also be
used for the purpose of reducing the quantity of infrared light
issued by the light source, for the purpose of limiting heating of
the imager. It may also be used for the purpose of making the light
drawn from the light source uniform in front of the imager. The
imager either does or does not pass light, according to whether the
light beam reaches a zone of the imager that is with or without a
screen. Once the light has passed through the imager 12, it is then
transmitted through an optic 13 of the headlight towards the road
to be lit. The optic 13 may be a light diffusing lens.
[0043] The form of the lighting zone I which is obtained depends in
particular on the optic 13 which is chosen.
[0044] In FIG. 3, the light beam projected on the road is shown in
a random form with the reference numeral 14. The references 14' and
14" represent two projected shadows which are obtained in the light
projected on the road. In practice, these projected shadows 14' and
14" are seen by the driver as black patches. Thus, when the driver
sees one or more black patches on the road scene in front of him,
he knows that there are living beings there.
[0045] FIG. 4 shows an imager 12 comprising a matrix of image
elements of pixels. These image elements are given the reference
numerals e1, e2, e3 . . . en.
[0046] In a preferred embodiment of the invention, the imager 12 is
a liquid crystal imager, in which each crystal forms an image
element.
[0047] In the imager of FIG. 4 one example of a mask is indicated
at M. The image elements that constitute the mask are shown in
black. These black image elements are occulting. They accordingly
prevent light from passing through the imager 12. On the other
hand, the image elements which do not constitute the mask M are
shown in clear. They are transparent and allow light through. The
resulting light beam, that is to say the light beam which is
obtained as the output from the imager 12, therefore has zones
without any light, which constitute a projected shadow around the
person.
[0048] In the example shown in FIG. 4, the mask M is rectangular.
In order to obtain such a mask of a particular form, for example
rectangular, the mask initially calculated is put through a
convolution by a convoluting element, which is for example
rectangular. This convoluting element may of course have any other
form, and may for example be oval. The convolution enables the form
and/or dimensions of the mask to be modified, the object of which
is to adjust the size of the projected shadow around the
person.
[0049] The mask produced on the imager of FIG. 4 is created by the
electronic system 3. The method of creating this mask is as
follows: when the camera 2 detects a person P2 in the road scene
situated in front of the vehicle, and in particular in the zone I
above the cut-off line C, the image captured by the camera 2 is
transmitted to the electronic system 3. The latter, using suitable
image processing, pinpoints the position of the person P2 in the
road scene, and also his dimensions. After the location of the
person P2 is identified, the electronic system 3 generates a mask,
still using image processing. The mask is passed to the imager 12
in inverse video with respect to the mask calculated by the
electronic system. In this connection, in the image captured by the
camera (in the case of a thermal camera), the zones detected (which
correspond to a person) are white, whereas the undetected zones are
black. The electronic system processes the natural image taken by
the camera and obtains a final mask which consists of white
elements. It therefore effects a video inversion of the mask
obtained and transmits this mask "in inverse video" to the imager.
In the imager, the mask is therefore composed of black elements,
that is to say those opaque to light, the zone which does not form
part of the mask consisting of white elements, that is to say those
transparent to light.
[0050] More precisely, in the case in which the camera 2 is a
thermal camera capable of detecting a living being, that is to say
a 10 micron thermal camera, the camera detects heat sources which
appear brighter on the image than the remainder of the image of the
road scene. What is called a thermal image is thereby obtained.
Subsequently, for this thermal image, a zone is selected for
processing, that is to say the brightest zone of the image. This
selection is determined as a function of a pre-defined brightness
threshold value. Beyond this threshold value, it is considered that
the matrix element of the camera corresponds to a hot zone and
therefore to the presence of a person. Each micro-bolometric
element of the camera matrix is thus given a threshold value for
determining whether there is a hot zone or not in the camera. The
hot zones correspond to a person, while the non-hot zones
correspond to the absence of any living being.
[0051] In other words, the image processing performed by the
electronic system 3 consists in selecting the zones of the thermal
image beyond a certain temperature, that is to say a predetermined
threshold value. An image over this value is therefore obtained
which causes only the person in the road scene to appear. This
image has two levels, that is to say a white level and a black
level. The person preferably appears in a pure white level, while
the rest of the image appears on a pure black level. This image is
then transmitted in inverse video to the imager 12, and is applied
on the imager. An inverted image, above the threshold value and
comprising a screen formed by black image elements, is thereby
obtained on the imager. This screen corresponds to the dimensions
and location of the person in the road scene. Thus, by lighting the
road with the light source 10 through the imager 12, only that part
of the light beam that passes through the imager beyond the mask is
projected on the road. The light beam on the road is thus modulated
by the mask applied on the imager 12. A projected shadow is thus
created around the person concerned.
[0052] A similar method may be used with a sensitive camera working
in the visible waveband or the near-infrared waveband.
[0053] In another version of the invention, the electronic system 3
may refine the formation of the mask, for example, by looking for
the contour of the person P2 before determining the image beyond
the threshold.
[0054] In a further version, already described, the mask may be
subjected to convolution with a suitable convoluting element which
enables the size and form of the mask to be modified.
[0055] The electronic system 3 just described may for example be an
integrated circuit or a DSP (digital signal processor). It may then
be incorporated very easily into the optical system 1 of the
headlight of the invention.
[0056] FIG. 5 shows a second embodiment of the optical system of
the headlight of the invention. Those elements of this optical
system which are identical to those of the optical system of FIG. 3
carry the same references.
[0057] In this embodiment, the optical system 1 comprises a light
source 10 and an imager 12, which are joined together through a
light guide 11 having two light paths 16 and 17. These two light
paths may be two matrices of optical fibres, or two optical fibres
of large cross section. The first optical fibre matrix 16 is
adapted to guide the light from the light source to the imager 12.
That part of the light beam which has passed through the imager 12
is then broadcast outside the headlight through an output optic
15a, which may for example be a diffusing lens similar to the lens
13 in FIG. 3.
[0058] The second optical fibre matrix 17 is adapted to lead the
light from the light source 10 directly to an output optic of the
headlight, which has the reference numeral 15b. This optic 15b may
be identical to the optic 15a.
[0059] This version, having two light guides, has an advantage in
energy terms, because it enables a dipped beam to be generated with
a maximum amount of energy without passing through the imager
which, in the passing state, has a transmission of about 80%. It is
only the 20%, approximately, of the light beam which is to form the
zone I and is liable to dazzle the target person that is controlled
by the modulator, that is to say transmitted through the
imager.
[0060] Thus, in this embodiment, the headlight is able to generate,
at the same time, a cruising beam illuminating the zone H and a
supplementary beam which illuminates the zone I and which is
produced by the method of the invention. The optical system then
enables illumination of the zone H with a main beam to be achieved
at the same time as lighting of the zone I to infinity, with a
common light source 10. In another embodiment of the invention, the
light source 10 may be adapted by itself to constitute the zone I
of lighting to infinity. In that case, the conventional lighting of
the vehicle can be used to form the main beam lighting zone H. The
headlight of the invention which lights the zone I can then be
placed within the vehicle headlight itself; the main beam headlight
of the vehicle then has two light sources, one of which projects
light directly to the output optic, while the other projects light
through the imager. The headlight of the invention can also be
mounted in a different place from the vehicle headlight within the
radiator grille of the vehicle. A motor vehicle could thus have
three headlights for example, namely two conventional main beam
driving lights (also referred to as main headlights), and a
headlight according to the invention which is located for example
in the middle of the front of the vehicle.
[0061] In the case of FIG. 5 as in the case of FIG. 3, the
electronic system 3 is arranged upstream of the imager 12, so as to
create a mask to be applied on the imager 12, the light emitted by
the light source 10 being projected outside the headlight as
explained above.
[0062] In the embodiment of FIG. 5, the light beam is transmitted
through optical fibres from the light source 10 to the imager 12
through a block or bar 18 of quartz or glass, the purpose of which
is to make the light beam homogeneous and to reduce its infrared
radiation. In other words, this quartz or glass block or bar 18
prevents the imager 12 from receiving excessive energy which would
be detrimental to the way it works.
[0063] Such a quartz or glass block or bar 18 may also be inserted
between the optical fibre matrix 11 and the imager 12, in the
optical system of FIG. 3.
[0064] It should also be noted that the use of a discharge lamp as
the light source 10 enables problems due to excessive temperature
on the imager to be avoided, since a discharge lamp is a cold
source. Moreover, transport of the light through optical fibres
also enables any heat to be diminished in the light emitted by the
light source 10.
[0065] In the embodiment of FIG. 5, the greater part of the optical
system 1 is incorporated in a headlight housing 15. This housing
may then be located outside the headlight, which enables a
headlight of reduced size and without any thermal stress to be
obtained. The optical connections 11 must in this case be longer.
This separation of the light source 10 can also be made in the
embodiment of FIG. 3. In parallel, in the embodiment of FIG. 5, the
light source 10 may be incorporated in the housing 15 with the
optical system 1.
[0066] In the whole of the foregoing description, the means for
detecting a person is described as being a thermal camera. This
detection means may also be an infrared camera associated with a
movement detector. In that case, the camera ensures capture of the
image of a road scene and the electronic system 3 detects and
pinpoints the position of persons by detecting movement. In another
version of the invention, thermal detection may be coupled with
movement detection in order to make detection of living beings more
secure.
[0067] In a further embodiment of the invention, it is arranged
that the optical fibres are displaced vertically by a small
distance in the focal plane of the optic 13, so as to modulate the
light and thereby form light beams which are compatible with the
"adverse weather lighting" or "motorway lighting" functions, that
is to say the functions of lighting in rain or lighting on
motorways.
[0068] FIGS. 6 to 9 illustrate a further version of the invention,
which makes use of an imager 12 consisting of a matrix of lenses,
the focal length of which is electrically controllable. Its
principle is as follows: as shown in FIG. 6, a lens is formed by
placing between two walls 21, of glass or transparent plastics
material, a liquid conductor 20 (water) and a drop of a liquid 23
which is non-miscible with water (an oil). YY represents the
optical axis, and a support 22 is provided. Under the effect of an
electric field which is applied in an appropriate way, the drop of
oil has a variable profile, because it moistens in a differing way
the wall on which it has been deposited, and this modifies the
focal length of the lens which itself consists of this oil drop.
Two possible profiles are shown respectively by a continuous line
and a broken line. FIG. 7 shows the variation in lens power (in
dioptres) of the lens as a function of the applied voltage: the
amplitude of variation is very high. FIGS. 8 and 9 represent the
whole of the optical system in a similar way to FIG. 5 and with the
same references: an optical fibre system 17 is used in association
with the imager 12, using a matrix of lenses the same as in FIG. 6.
FIG. 9 shows how one of the lenses changes shape according to
whether the voltage applied to it is 0 or 10 volts.
[0069] The method according to the invention which has just been
described enables main beam lighting to be obtained which is
superior to the usual lighting situated above the cut-off line,
while ensuring that this additional lighting will not dazzle any
living beings who happen to be in the field of illumination. This
supplementary lighting obtained in the zone I enables the driver to
see the road scene beyond the cut-off line C. The black patches
which can be seen by the driver in this additional lighting warn
him of the presence of living beings in the road scene. The method
of the invention thus enables any obstacles for the driver to be
detected.
[0070] Whatever embodiment is adopted, the headlight of the
invention ensures improved perception and improved visibility of
the road by the driver. In this connection, this headlight permits
conventional lighting of the road scene and also more remote
illumination beyond the cut-off line. Even if this more remote
illumination includes black patches, and even if these black
patches are numerous, for example in the case of a group of people
to one side of the road, the driver does of necessity have better
visibility than with conventional lighting, because this more
remote lighting is additional lighting.
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