U.S. patent application number 10/372662 was filed with the patent office on 2003-10-30 for night vision arrangement.
This patent application is currently assigned to AUTOLIV DEVELOPMENT AB. Invention is credited to Eriksson, Dick, Kallhammer, Jan-Erik.
Application Number | 20030202097 10/372662 |
Document ID | / |
Family ID | 29253780 |
Filed Date | 2003-10-30 |
United States Patent
Application |
20030202097 |
Kind Code |
A1 |
Kallhammer, Jan-Erik ; et
al. |
October 30, 2003 |
Night vision arrangement
Abstract
In a night vision arrangement for a motor vehicle a camera is
provided which captures an image which is subsequently displayed on
a display arrangement which may be a head-up display arrangement.
The camera directs light on to a beam deflector which may be
constituted by a mirror which deflects the beam so that it passes
along a neck on to a sensor. The camera may relatively easily be
mounted in position in a motor vehicle.
Inventors: |
Kallhammer, Jan-Erik;
(Goteborg, SE) ; Eriksson, Dick; (Alingsas,
SE) |
Correspondence
Address: |
VENABLE, BAETJER, HOWARD AND CIVILETTI, LLP
P.O. BOX 34385
WASHINGTON
DC
20043-9998
US
|
Assignee: |
AUTOLIV DEVELOPMENT AB
Vargarda
SE
|
Family ID: |
29253780 |
Appl. No.: |
10/372662 |
Filed: |
February 25, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10372662 |
Feb 25, 2003 |
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10179035 |
Jun 26, 2002 |
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10179035 |
Jun 26, 2002 |
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PCT/SE01/02253 |
Oct 16, 2001 |
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10179035 |
Jun 26, 2002 |
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PCT/SE02/00785 |
Apr 23, 2002 |
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Current U.S.
Class: |
348/148 ;
348/164; 348/E5.09 |
Current CPC
Class: |
B60R 2300/8053 20130101;
B60R 2300/101 20130101; H04N 5/33 20130101; G02B 23/12 20130101;
B60R 2001/1253 20130101; B60R 2300/205 20130101; B60R 1/00
20130101; H04N 7/183 20130101; B60R 11/04 20130101; B60R 2300/106
20130101 |
Class at
Publication: |
348/148 ;
348/164 |
International
Class: |
H04N 007/18; H04N
009/47 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 26, 2000 |
SE |
0003942 |
Claims
What is claimed is:
1. A night vision arrangement for a vehicle, the night vision
arrangement comprising: a camera, the camera comprising an optical
element which is substantially transparent to at least infra-red
light, the optical element defining an optical axis, the camera
further comprising an infra-red sensor to capture an image received
through the optical element, and a beam deflector in alignment with
the optical axis adapted to deflect the beam received through the
optical element and to direct the deflected beam on to the sensor;
and a display unit to display the captured image to a driver of the
vehicle, part of the camera contains the sensor being mounted
within the main envelope of the vehicle in with the optical
element, when in an operative position, being beyond said
envelope.
2. The arrangement according to claim 1, wherein the optical
element is a lens.
3. The arrangement according to claim 1, wherein the optical
element is a non-distorting window.
4. The arrangement according to claim 1, wherein the beam deflector
is adapted to deflect the beam through approximately
90.degree..
5. The arrangement according to claim 1, wherein the beam deflector
comprises a mirror.
6. The device according to claim 1, wherein a part of the camera
containing the sensor is mounted within the vehicle, with the
optical element being positioned or positionable on the exterior of
the vehicle.
7. The arrangement according to claim 1, further comprising a means
for heating the optical element of the camera.
8. The arrangement according to claim 1, further comprising a means
for protecting the optical element from the environment.
9. The arrangement according to claim 8, wherein the means for
protecting the optical element from the environment comprises a
cover movable to a position in which the optical element is
covered.
10. The arrangement according to claim 8, wherein the means for
protecting the optical element comprises a means for moving the
camera and the optical element so that the optical element is in a
retracted and protected position.
11. The arrangement according to claims 1, wherein the camera is
adapted for being incorporated into a mirror housing.
12. An arrangement according to claim 1, wherein the camera is
adapted for being mounted in a fender or bumper.
13. The arrangement according to claim 12, wherein the camera is
adapted for being mountable for being moved vertically between an
operative position and a retracted position.
14. The arrangement according to claim 12, wherein the camera
includes a cover movable between a retracted position in which the
optical element is exposed and a closed position in which the
optical element is covered.
15. The arrangement according to claim 1, wherein the camera is
adapted for being mounted on the roof of a vehicle.
16. The arrangement according to claim 15, wherein the camera is
adapted for being incorporated in a roof mounted aerial.
17. The arrangement according to claim 15, wherein the camera is
adapted for being incorporated in a roof rail.
18. A device for the enhancement of night vision in a vehicle like
an automobile comprising: an infra-red camera for being mounted on
the vehicle to view an area in front of the camera, and generating
a video signal representing the thermal image of the area, the
camera comprising an optical element for passing light
therethrough, and an infra-red sensing means for sensing the light
passed through the optical element, and an optical means having an
elongated neck and conveying infra-red radiation received through
the optical element to the infra-red sensing means; a processing
unit for processing signals from the sensing means; and a display
unit coupled to the processing unit for making an image visible to
the vehicle operator.
19. The arrangement according to claim 3, wherein the camera
further comprises a separate lens for focussing light passing
through the window onto the sensor.
Description
CROSS REFERNECE TO RELATED APPICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 10/179,035 (Attorney Docket 31577-180866)
filed on Jun. 26, 2002, which is a continuation-in-part of
International Patent Application PCT/SE01/02253 filed on Oct. 16,
2001 designating the United States and claiming priority to Swedish
Application No. 0003942-0 filed on Oct. 26, 2000 and also a
continuation-in-part of International Patent Application
PCT/SE02/00785 filed on Apr. 23, 2002, designating the United
States. The disclosures of the foregoing applications and the U.S.
patents mentioned below are incoporated herein by reference in
their entirety.
BACKGROUND OF THE INVENTION
[0002] The present invention relates to a night vision arrangement
in the form of a device for the enhancement of night vision in a
vehicle, such as an automobile.
[0003] It has been proposed previously to provide a night vision
arrangement in an automobile. U.S. Pat. No. 5,414,439 discloses an
arrangement in which a vehicle is equipped with an infra-red
sensitive camera which is directed to capture an image of the
roadway in front of the vehicle. The camera provides an output in
the form of a video signal which is processed by a video processor,
and which is then passed to a head-up display. It has been known
previously to provide head-up display units in vehicles such as
combat aircraft to enable the pilots of the aircraft to view,
simultaneously, the scene on the exterior of the aircraft, and also
an image projected on to the head-up display. U.S. Pat. No.
5,414,439 utilises a head-up display of this general type to enable
the driver of the vehicle to view the road in front of the vehicle
and, simultaneously, to see an image derived from the infra-red
camera.
[0004] In the arrangement of U.S. Pat. No. 5,414,439, the
windshield is provided with a semi-transparent mirror which is
utilised as a combiner to combine the real image of the road in
front of the vehicle as viewed by the driver, and a virtual image
of the road ahead.
[0005] The infra-red sensitive camera of U.S. Pat. No. 5,414,439 is
of conventional design incorporating a lens arrangement which
serves to focus an image on a relatively large sensor element which
is located in alignment with the optical axis of the lens
arrangement. The entire camera is rather bulky and the positioning
of the camera is shown, schematically, with the camera being
mounted within the engine compartment of the vehicle.
SUMMARY OF THE INVENTION
[0006] The present invention seeks to provide an improved night
vision arrangement.
[0007] According to this invention there is provided a night vision
arrangement for a vehicle, the night vision arrangement
incorporating a camera, the camera comprising an optical element
which is substantially transparent to at least infra-red light, and
an infrared sensor to capture an image received through the optical
element, there being a display unit to display the captured image
to a driver of the vehicle, characterised in that the optical
element defines an optical axis, and within the camera a beam
deflector is provided in alignment with the optical axis adapted to
deflect the beam received through the optical element and to direct
the deflected beam on to the sensor. In one embodiment, the optical
element may comprise a light collecting lens. In an alternative
embodiment, the optical element may comprise a non-distorting
window which is substantially transparent to infra-red light.
[0008] Preferably the beam deflector is adapted to deflect the beam
through approximately 90.degree.. The angle of deflection of the
beam deflected by the beam deflector does depend upon the detailed
design of the camera, and the intended location of the camera. It
is intended that the camera should be mounted in position with only
the optical element exposed.
[0009] Conveniently the beam deflector comprises a mirror.
Alternatively the beam deflector may comprise a prism or some other
optical unit which deflects the beam. Preferably a separate,
focussing lens is located between the deflector and the sensor for
focussing light which is passed through the optical element onto
the sensor. The deflector and focussing lens may also be located
within a sealed housing, wherein the optical element comprises a
part of the sealed housing.
[0010] Advantageously a part of the camera containing the sensor is
mounted within the envelope of the vehicle, with the optical
element being positioned or positionable on the exterior of the
vehicle. If the main part of the camera, which contains the sensor,
is mounted within the envelope of the vehicle, the aerodynamic
property of the vehicle will not be influenced substantially by the
camera arrangement. Also, the mounting of the camera in position,
during the assembly of the vehicle, may be facilitated.
[0011] Conveniently means are provided to heat the optical element
of the camera. This may minimise any problems that might otherwise
arise due to condensation.
[0012] Advantageously means are provided to protect the optical
element from the environment. Thus the optical element may be
protected from the environment at times when the night vision
arrangement is not in use.
[0013] In one embodiment the means provided to protect the optical
element from the environment comprise a cover movable to a position
in which the optical element is covered.
[0014] In another embodiment the means to protect the optical
element comprise means to move the camera and the optical element
so that the optical element is in a retracted and protected
position.
[0015] Preferably the camera is mounted in position for pivotal
movement about a horizontal axis parallel with the axis of the
vehicle between an operative position and a retracted position, a
wiper being provided to wipe the optical element as the camera
moves.
[0016] In an alternative embodiment the camera is incorporated into
a mirror housing.
[0017] In another modified embodiment the camera is mounted in a
fender or bumper.
[0018] Conveniently the camera is mounted to be moved vertically
between an operative position and a retracted position.
[0019] Alternatively the camera is provided with a cover movable
between a retracted position in which the optical element is
exposed, and a closed position in which the optical element is
covered.
[0020] In another embodiment of the invention the camera is adapted
to be mounted on the roof of a vehicle.
[0021] Conveniently the cover is incorporated in a roof mounted
aerial.
[0022] Alternatively the camera is incorporated in a roof rail.
[0023] According to another embodiment of this invention there is
provided a device for the enhancement of night vision in a vehicle
like an automobile. The device comprises an infra-red camera for
being mounted on the vehicle to view an area in front of the
camera, and generating a video signal representing the thermal
image of the area, the camera comprising an optical element for
passing light therethrough, and an infra-red sensing means for
sensing the light passed through the optical element, and an
optical means having an elongated neck and conveying infra-red
radiation received through the optical element to the infra-red
sensing means. The device further comprises a processing unit for
processing signals from the sensing means; and a display unit
coupled to the processing unit for making an image visible to the
vehicle operator.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] In order that the invention may be more readily understood,
and so that further features thereof may be appreciated, the
invention will now be described by way of example, with reference
to the accompanying drawings in which:
[0025] FIG. 1 is a schematic illustration of a night vision
arrangement for a motor vehicle in accordance with the
invention,
[0026] FIG. 2 is a view similar to that of FIG. 1 illustrating a
modified embodiment of the invention,
[0027] FIG. 3 is a diagrammatic side view illustrating a camera of
one embodiment of the invention mounted in position on a motor
vehicle,
[0028] FIG. 4 is a front view of the camera of FIG. 3 in the
operative position,
[0029] FIG. 5 is a front view corresponding to FIG. 4 illustrating
the camera of FIG. 3 in a non-operative position,
[0030] FIG. 6 is diagrammatic view illustrating a camera of another
embodiment of the invention,
[0031] FIG. 7 is a diagrammatic view illustrating the camera of yet
another embodiment of the invention,
[0032] FIG. 8 is a diagrammatic side view illustrating the camera
of a further embodiment of the invention,
[0033] FIG. 9 is a diagrammatic side view of part of a motor
vehicle provided with a camera forming part of the embodiment of
the invention,
[0034] FIG. 10 is an enlarged view of part of FIG. 9, and
[0035] FIG. 11 is a side view of part of a vehicle provided with a
camera forming part of yet another embodiment of an invention.
[0036] FIG. 12 is a schematic illustration of another alternate
embodiment of a night vision arrangement for a motor vehicle in
accordance with the invention,
[0037] FIG. 13 is a view similar to that of FIG. 12 illustrating a
modified embodiment of the invention,
[0038] FIG. 14 is a diagrammatic side view illustrating a camera of
yet another embodiment of the invention mounted in position on a
motor vehicle,
[0039] FIG. 15 is a front view of the camera of FIG. 14 in the
operative position,
[0040] FIG. 16 is a front view corresponding to FIG. 15
illustrating the camera of FIG. 3 in a non-operative position,
[0041] FIG. 17 is diagrammatic view illustrating a camera of
another embodiment of the invention,
[0042] FIG. 18 is a diagrammatic view illustrating the camera of
yet another embodiment of the invention,
[0043] FIG. 19 is a diagrammatic side view illustrating the camera
of a further embodiment of the invention,
[0044] FIG. 20 is a diagrammatic side view of part of a motor
vehicle provided with a camera forming part of the embodiment of
the invention,
[0045] FIG. 21 is an enlarged view of part of FIG. 20, and
[0046] FIG. 22 is a side view of part of a vehicle provided with a
camera forming part of yet another embodiment of an invention.
DETAILED DESCRIPTION OF THE INVENTION
[0047] Referring initially to FIG. 1 of the accompanying drawings,
a night vision arrangement for a vehicle such as motor car
comprises a camera arrangement 1 to capture an image, a signal
processing unit 2 and a display arrangement 3 adapted to display an
image.
[0048] The camera arrangement 1 comprises a lens 4 through which
infra-red light, forming an image, is to pass into the interior of
the camera.
[0049] The lens 4 defines an optical axis, and, when the camera
unit 1 is positioned on a motor vehicle, the optical axis in front
of the lens is directed towards the roadway in front of the
vehicle, so that the camera can capture an image of the roadway in
front of the vehicle.
[0050] Behind the lens 4, in alignment with the optical axis, a
beam deflector 6 which, in the illustrated embodiment of the
invention, is constituted by a mirror 7 which is inclined at
substantially 45.degree. to the optical axis of the lens. Thus the
beam deflector 6 serves to deflect the beam passing through the
lens 4 by approximately 90.degree..
[0051] The beam deflector 6 is connected, by means of an elongate
hollow neck 8, to a main housing 9 of the camera 1. Contained
within the elongate neck 8 is a focusing lens 10, which serves to
focus light from the beam deflector 6 on to a sensor 11 present
within the housing 9. The sensor 11 is an infra-red sensor, and may
comprise a microbolometer. The sensor may be a charge-coupled
device. The sensor is shown mounted on an electronic unit 12 which
receives the signals from the sensor and which provides an output
on the output lead 13.
[0052] It is to be understood, therefore, that the infra-red
sensitive camera 1 is provided with a housing 9 which contains an
infra-red sensor 11 which is adapted to capture an image, and the
housing 9 is connected by means of a hollow neck 8 extending to a
beam deflector 6 which is located adjacent the lens 4. The housing
may be sealed to prevent the ingress of dirt or moisture.
[0053] In an alternative arrangement, the optical element may be
formed by one face of a prism that acts as the beam deflector.
[0054] The output 13 from the camera 1 passes through an image
processor unit 2 which provides a signal on a lead 14 which passes
to an image generator 15. The image generator 15 may be a cathode
ray tube device, or some other equivalent arrangement. The image
generator 15 is positioned at an appropriate location generally in
front of a combiner 16, which may be mounted on the windshield of a
motor vehicle, and which may be a semi-transparent aspheric
mirror.
[0055] In use of the arrangement, as shown in FIG. 1, the camera 1
will be mounted in a motor vehicle so that the optical axis of the
lens 4 is directed generally along the roadway in front of the
motor vehicle, enabling the camera 1 to generate an infra-red image
of the roadway in front of the vehicle. That image is presented on
the image generator 15. The driver of the vehicle may thus
simultaneously view, in the combiner 16, the real image of the
roadway outside the vehicle, and a virtual image of the roadway, as
presented on the image generator 15.
[0056] FIG. 2 illustrates a second embodiment of the invention in
which the camera 1 and signal processor 2 are exactly as described
above with reference to FIG. 1. These components will not be
re-described. In this embodiment the output 14 of the signal
processing unit 2 is connected directly to a monitor 17, which may
be in the form of a cathode ray tube or the like. The monitor 17 is
located at a position where it can be viewed by the driver of a
motor vehicle.
[0057] Referring now to FIGS. 3 to 5, a camera 1, as described
above, is illustrated mounted in position on a motor vehicle. The
internal components of the camera are not shown in these
figures.
[0058] Referring initially to FIG. 3, the camera 1 is mounted in
position with the main housing 9 being located within a recess
20.
[0059] The camera 1 is located in position so that the main housing
9 is located within the recess, with the neck 8 extending
vertically upwardly, so that the lens 4 is located above the
envelope of the vehicle, thus ensuring that the lens 4 has an
adequate "view" of the road in front of the vehicle. The main
housing 9 is thus located within the main envelope defined by the
vehicle, with only that part of the neck 8 carrying the lens 4
projecting beyond the envelope.
[0060] The camera 1 of the embodiment shown in FIGS. 3 to 5, is
mounted in position for pivotal movement about a substantially
horizontal pivot axis 21, the pivot axis being aligned with the
axis of the vehicle. The entire camera may thus pivot from a first
operative position, as shown in FIGS. 3 and 4, in which the lens 4
is located above the rear edge of the bonnet 22, to a retracted
position, as shown in FIG. 5, in which the lens is positioned
beneath the rear edge of the hood or bonnet 2. The lens, in this
retracted position, is somewhat protected from the environment
which may contain rain or dust.
[0061] It is to be appreciated that in the embodiment of FIGS. 3 to
5, the main housing 9 of the camera is, at all times, within the
envelope of the vehicle, with the lens 4 being movable to the
operative position where it extends beyond the envelope of the
vehicle. The optical axis of the lens 4, when the camera is in the
operative position, is very close to the actual line of sight of
the driver of the vehicle, if the camera is positioned immediately
in front of the driver. This serves to minimise any parallax error
which might otherwise arise.
[0062] The camera of the embodiment of FIGS. 3 to 5 may be driven
about the pivot axis 21 by means of an appropriate electric or
hydraulic motor. The motor may be controlled so that the camera is
only moved to the operative position when the night vision
arrangement is actuated, although the driver may have a control
which can be actuated to cause the camera to move from the
operative position to the retracted position, and back again, so
that the driver may effect a cleaning of the lens of the
camera.
[0063] FIG. 6 illustrates another embodiment of the invention in
which a camera 1 as described above is mounted in a motor vehicle,
with the camera being mounted in position to form part of a wing
mirror unit 30. Again, the internal components of the camera are
not shown. The wing mirror unit 30 has a base portion 31 connected
to part 32 of the door of a vehicle, and has an extension portion
33 which contains the actual mirror 34. In this embodiment the
camera 1 is mounted in position with the main housing 9 being
located within the door, and with the neck 8 extending horizontally
into the base portion 31 of the wing mirror unit 30. The lens 4 is
positioned in an appropriate aperture formed in the forward facing
part of the base portion 31 of the wing mirror unit 30. The camera
may easily be mounted in this position as the motor vehicle is
fabricated.
[0064] Referring now to FIG. 7 of the accompanying drawings, a
camera 1 of the type described above is shown mounted in position
within the bumper or fender 40 of the motor vehicle. Again, the
internal components of the camera are not shown. The camera 1 is
shown in position beneath a headlight 41. The camera is mounted in
position within a recess 42 formed in the bumper or fender with the
housing 9 within the envelope of the vehicle. The camera is located
in position with the neck 8 extending vertically upwardly so that
the lens 4 is positioned immediately above the top surface of the
bumper or fender 40. Preferably the camera is positioned
immediately in front of the driver in order to minimise any
parallax problems. In the illustrated embodiment, the camera may
move vertically from an upper or elevated position, as shown in
solid line, to a lower or retracted position as shown in dotted
lines 43. When the camera is in the lower position the lens is
retracted into the recess 42 formed in the bumper or fender 40,
thus protecting the lens from the environment.
[0065] FIG. 8 illustrates a further embodiment in which a camera 1
of the type described above is mounted in position within a bumper
or fender 50 and in this figure the internal components of the
camera are not shown. Again, the camera 1 is located adjacent a
headlight 51. In this embodiment of the invention, the bumper or
fender 50 defines a recess 52, and the camera 1 is mounted at a
fixed position within the recess 52, with the housing 9 within the
envelope of the vehicle. The neck 8 of the camera extends upwardly
so that the lens 4 is positioned above the upper edge of the bumper
or fender. Mounted within the bumper or fender is a pivotally
movable cover 53. The cover 53 is adapted to pivot about a pivot
axis 54. The cover may move from a retracted position, as shown in
solid lines in FIG. 8, in which the lens 4 is exposed has a clear
view across the top part of the bumper or fender 50, to a closed
position, as shown in dotted lines 54 in FIG. 8, in which the cover
53 extends in front of and above the lens to cover and protect the
lens 4.
[0066] Reference is now made to FIGS. 9 and 10 of the accompanying
drawings in which an aerial unit 60 is shown mounted on the roof 61
of a motor vehicle. The internal components of the aerial unit are
not shown in FIG. 9. The aerial unit 60 incorporates an aerial or
antenna 62 mounted on an upper housing 63. The front part of the
upper housing 63 is provided with a lens 64, similar to the lens 4
of the camera described above, the lens 64 having an optical axis
aligned with a beam deflector 65 contained within the upper housing
63. The upper housing 63 is connected by means of a neck 66 which
extends from the lower part of the upper housing 63, to a lower
housing 67. Contained within the lower housing 67 is an image
detector 68, corresponding to the image detector 11 described
above. The beam deflector 65 deflects the beam entering the camera
through the lens 64 by approximately 90.degree. so that the
deflected beam impinges on the image detector 68. Thus the upper
housing 63 and the lower housing 67 together constitute a camera
which is, effectively, of the same operative design as the camera 1
described above. It is to be noted that the camera of the
embodiments of FIGS. 9 and 10 is mounted in position with the neck
66 passing through an aperture 69 formed in the roof sheet of the
vehicle. Thus the lower housing 67, containing the sensor 68, is
mounted within the envelope of the vehicle. The lower housing 67 is
larger than the aperture 69, and so the aerial unit 60 cannot
easily be removed from the vehicle.
[0067] FIG. 11 illustrates a further embodiment of the invention in
which a camera is incorporated within a roof rail of the motor
vehicle. Referring to FIG. 11, a roof rail 70 of a motor vehicle
has, at its forward-most end, a chamber 71, the front part of the
chamber being provided with a lens 72. The lens 72 corresponds with
the lens 4 as described above. Contained within the chamber 71 in
alignment with the optical axis of the lens 72 is a beam deflector
constituted, in this embodiment, by an inclined mirror 73. The
lower part of the chamber 71 is connected, by means of a relatively
narrow neck 74 which passes through an aperture 75 formed in the
roof of the vehicle, the neck 74 terminating in an enlarged lower
housing 76 which contains an infra-red sensor of the type described
above. The beam entering the camera through the lens 72 is focussed
onto the infra-red sensor. It is to be appreciated that in this
embodiment the housing containing the sensor is within the envelope
of the vehicle.
[0068] FIG. 12 shows an alternative embodiment of the invention
wherein the lens 4 of FIG. 1 is replaced with a non-distorting
window 4 which is substantially transparent to infra-red light. The
window is perpendicular to an optical axis, the optical axis being
in front of the window and directed towards the roadway when the
camera is positioned on a motor vehicle.
[0069] FIGS. 13-19 are similar to FIGS. 2-8 except that the lens 4
has been replaced with a non-distorting window 4' which is
substantially transparent to infra-red light.
[0070] FIG. 20 is similar to FIG. 9 except that the lens 60 has
been replaced with a non-distorting window 60' which is
substantially transparent to infra-red light.
[0071] FIG. 21 shows yet another alternative embodiment of the
invention wherein the lens 64 of FIG. 10 is replaced with a
non-distorting window 64' which is substantially transparent to
infra-red light. For convenience, all features common to both FIGS.
10 and 21 are identified by common reference numbers. In this
embodiment, a focussing lens 70 is positioned between the beam
deflector 65 and the image detector 68. The beam deflector 65
deflects the beam entering the camera through window 64' by
approximately 90.degree. so that the deflected beam is passed
through the lens 70 and is focused onto the image detector 68.
[0072] FIG. 22 shows another alternative embodiment of the
invention wherein the lens 72 of FIG. 11 is replaced with a window
72' which is substantially transparent to infra-red light. For
convenience, all features common to both FIGS. 11 and 22 are
identified by common reference numbers. In this embodiment, the
lower housing 76 contains an infra-red sensor 77 of the type
described above. The beam entering the camera through window 72 is
focused onto the infra-red sensor by a lens 78 located between the
mirror 73 and the sensor 77.
[0073] In all of the described embodiments of the invention, a
heater may be provided to heat the optical element of the camera to
minimise or obviate condensation on the optical element. The heater
may be an electric heater or may be means to direct heated air from
the vehicle heating system on to the optical element.
[0074] The invention has been described in detail with respect to
preferred embodiments, and it will now be apparent from the
foregoing to those skilled in the art, that changes and
modifications may be made without departing from the invention in
its broader aspects, and the invention, therefore, as defined in
the appended claims, is intended to cover all such changes and
modifications that fall within the true spirit of the
invention.
* * * * *