U.S. patent application number 10/993765 was filed with the patent office on 2005-04-07 for headlamp control to prevent glare.
Invention is credited to Stam, Joseph S..
Application Number | 20050073853 10/993765 |
Document ID | / |
Family ID | 26928937 |
Filed Date | 2005-04-07 |
United States Patent
Application |
20050073853 |
Kind Code |
A1 |
Stam, Joseph S. |
April 7, 2005 |
Headlamp control to prevent glare
Abstract
A system for controlling at least one exterior vehicle light of
a controlled vehicle includes an array of sensors and a control
unit. The array of sensors is capable of detecting light levels in
front of the controlled vehicle. The control unit is in
communication with the array of sensors and the at least one
exterior vehicle light and determines a distance and an angle from
the at least one exterior vehicle light of the controlled vehicle
to a leading vehicle. The control unit is operable to control
operation of the at least one exterior vehicle light as a function
of the distance and angle, based on the output from the array of
sensors, and prevent the at least one exterior vehicle light from
providing a disruptive glare to a driver of the leading
vehicle.
Inventors: |
Stam, Joseph S.; (Holland,
MI) |
Correspondence
Address: |
PRICE, HENEVELD, COOPER, DEWITT, & LITTON,
LLP/GENTEX CORPORATION
695 KENMOOR, S.E.
P O BOX 2567
GRAND RAPIDS
MI
49501
US
|
Family ID: |
26928937 |
Appl. No.: |
10/993765 |
Filed: |
November 19, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10993765 |
Nov 19, 2004 |
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10235476 |
Sep 5, 2002 |
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10993765 |
Nov 19, 2004 |
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10197834 |
Jul 18, 2002 |
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6593698 |
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10197834 |
Jul 18, 2002 |
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09938774 |
Aug 24, 2001 |
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6429594 |
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09938774 |
Aug 24, 2001 |
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09546858 |
Apr 10, 2000 |
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6281632 |
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09546858 |
Apr 10, 2000 |
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09157063 |
Sep 18, 1998 |
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6049171 |
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60339762 |
Dec 10, 2001 |
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Current U.S.
Class: |
362/503 |
Current CPC
Class: |
F21Y 2115/10 20160801;
B60Q 1/085 20130101; F21W 2102/135 20180101; F21S 41/321 20180101;
F21S 41/675 20180101; B60Q 2300/332 20130101; F21S 41/25 20180101;
F21W 2102/13 20180101; F21S 41/67 20180101; B60Q 2300/122 20130101;
B60Q 2300/334 20130101; B60Q 2300/112 20130101; B60Q 2300/114
20130101; B60Q 2300/42 20130101; F21S 41/698 20180101; F21S 41/62
20180101; F21S 41/645 20180101; B60Q 2300/056 20130101; F21S 41/00
20180101; F21S 41/151 20180101; F21V 9/40 20180201; B60Q 2300/3321
20130101; B60Q 2300/312 20130101; B60Q 2300/314 20130101; B60Q
2300/322 20130101; B60Q 2300/331 20130101; B60Q 1/10 20130101; B60Q
1/18 20130101; F21S 41/692 20180101; B60Q 2300/21 20130101; B60Q
2300/054 20130101; F21S 41/148 20180101; F21S 41/43 20180101; B60Q
2300/132 20130101; B60Q 2300/41 20130101 |
Class at
Publication: |
362/503 |
International
Class: |
B60Q 001/26 |
Claims
What is claimed is:
1. A vehicle exterior light control, comprising: a controller
configure to receive at least one image and further configured to
generate at least one exterior light brightness control signal as a
function of said at least one image, said controller is further
configured to generate at least one exterior light aim control
signal as a function of at least one second sensor.
2. A vehicle exterior light control as in claim 1 wherein said at
least one second sensor is a steering wheel angle sensor.
3. A vehicle exterior light control as in claim 1 wherein said at
least one second sensor is a global positioning system sensor.
4. A vehicle exterior light control as in claim 1 wherein said at
least one second sensor is a Loran sensor.
5. A vehicle exterior light control as in claim 1 wherein said at
least one second sensor is a pitch sensor.
6. A vehicle exterior light control as in claim 2 wherein said at
least one exterior light aim control signal is configured to effect
horizontal aim.
7. A vehicle exterior light control as in claim 5 wherein said at
least one exterior light aim control signal is configured to effect
vertical aim.
8. A vehicle exterior light control as in claim 1 wherein said at
least one second sensor comprises a steering wheel angle sensor and
a pitch sensor.
9. A vehicle exterior light control as in claim 8 wherein said at
least one exterior light aim control signal is configured to effect
vertical aim and horizontal aim.
10. A vehicle exterior light control, comprising: a first
controller configured to receive at least one image and further
configured to generate at least one exterior light brightness
control signal as a function of said at least one image, a second
controller configured to generate at least one exterior light aim
control signal as a function of at least one second sensor.
11. A vehicle exterior light control as in claim 10 wherein said at
least one second sensor is a steering wheel angle sensor.
12. A vehicle exterior light control as in claim 10 wherein said at
least one second sensor is a global positioning system sensor.
13. A vehicle exterior light control as in claim 10 wherein said at
least one second sensor is a Loran sensor.
14. A vehicle exterior light control as in claim 10 wherein said at
least one second sensor is a pitch sensor.
15. A vehicle exterior light control as in claim 11 wherein said at
least one exterior light aim control signal is configured to effect
horizontal aim.
16. A vehicle exterior light control as in claim 14 wherein said at
least one exterior light aim control signal is configured to effect
vertical aim.
17. A vehicle exterior light control as in claim 10 wherein said at
least one second sensor comprises a steering wheel angle sensor and
a pitch sensor.
18. A vehicle exterior light control as in claim 17 wherein said at
least one exterior light aim control signal is configured to effect
vertical aim and horizontal aim.
19. A vehicle exterior light control as in claim 10 wherein said
first controller is associated with a rearview mirror assembly.
20. A vehicle exterior light control, comprising: a controller
configure to receive at least one image and further configured to
generate at least one exterior light brightness control signal as a
function of at least one image, said controller is further
configured to generate at least one exterior light aim control
signal as a function of at least one image.
21. A vehicle exterior light control as in claim 20 wherein said at
least one exterior light aim control signal is configured to effect
horizontal aim.
22. A vehicle exterior light control as in claim 20 wherein said at
least one exterior light aim control signal is configured to effect
vertical aim.
23. A vehicle exterior light control as in claim 20 wherein said at
least one exterior light aim control signal is configured to effect
vertical and horizontal aim.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 10/253,476, filed on Sep. 5, 2002, entitled
"HEADLAMP CONTROL TO PREVENT GLARE," which claims the benefit of
U.S. Provisional Patent Application Ser. No. 60/339,762, entitled
"HEADLAMP CONTROL TO PREVENT GLARE," which was filed Dec. 10, 2001,
and which is hereby incorporated herein by reference in its
entirety.
[0002] This application is a continuation-in-part of U.S. patent
application Ser. No. 10/197,834, entitled "CONTINUOUSLY VARIABLE
HEADLAMP CONTROL," filed Jul. 18, 2002, now U.S. Pat. No.
6,593,698, which is a continuation of U.S. patent application Ser.
No. 09/938,774, entitled "CONTINUOUSLY VARIABLE HEADLAMP CONTROL,"
filed on Aug. 24, 2001, now U.S. Pat. No. 6,429,594, which is a
continuation of U.S. patent application Ser. No. 09/546,858,
entitled "CONTINUOUSLY VARIABLE HEADLAMP CONTROL," filed on Apr.
10, 2000, now U.S. Pat. No. 6,281,632, which is a continuation of
U.S. patent application Ser. No. 09/157,063, entitled "CONTINUOUSLY
VARIABLE HEADLAMP CONTROL," filed on Sep. 18, 1998, now U.S. Pat.
No. 6,049,171. The entire disclosure of each of the above-noted
applications is incorporated herein by reference. Priority under 35
U.S.C. .sctn.120 is hereby claimed to the filing dates of each of
the above-identified applications.
[0003] This application is related to U.S. patent application Ser.
No. 10/208,142, entitled "LIGHT SOURCE DETECTION AND CATEGORIZATION
SYSTEM FOR AUTOMATIC VEHICLE EXTERIOR LIGHT CONTROL AND METHOD OF
MANUFACTURING," filed on Jul. 30, 2002, now U.S. Pat. No.
6,774,988, which is hereby incorporated herein by reference in its
entirety.
BACKGROUND OF THE INVENTION
[0004] The present invention is generally directed to controlling
exterior vehicle lights of a motor vehicle and, more specifically,
to controlling exterior vehicle lights of a motor vehicle so as to
reduce glare to occupants of other motor vehicles and/or
pedestrians, as well as providing optimal lighting for various
roads/environmental conditions.
[0005] Currently, rearview mirror glare from trailing vehicles is a
significant safety and nuisance concern, while driving at night.
Sport utility vehicles (SUVs) and trucks, which generally have
headlamps mounted much higher than passenger vehicles, may provide
a much higher level of rearview glare than typical passenger cars.
This glare may be especially disruptive in busy traffic situations
where an SUV or truck is following a small passenger car. As a
result of the glare experienced by drivers of passenger cars, when
closely followed by an SUV or truck, various solutions, such as
reducing the mounting height limit of headlamps, have been proposed
to help alleviate this problem. Unfortunately, solutions such as
reducing the mounting height limit of an SUV or truck's headlamps
may generally require an objectionable change to the front end
styling of the SUV or truck. Additionally, the physical
construction of large SUVs and trucks may make it impossible to
reduce the mounting height significantly.
[0006] Thus, what is needed is a technique for reducing the glare
caused by low-beam headlamps of SUVs and trucks that does not
involve lowering the mounting height of low-beam headlamps of the
SUV/truck. Further, it would be desirable for the technique to
function with both leading and on-coming vehicles and be applicable
to all vehicle types, roads and environmental conditions.
SUMMARY OF THE INVENTION
[0007] An embodiment of the present invention is directed to a
system for controlling at least one exterior vehicle light of a
controlled vehicle and includes an array of sensors and a control
unit. The array of sensors is capable of detecting light levels in
front of the controlled vehicle. The control unit is in
communication with the array of sensors and the at least one
exterior vehicle light and determines an approximate distance and
an angle from the at least one exterior vehicle light of the
controlled vehicle to a leading vehicle. The control unit is also
operable to control operation of the at least one exterior vehicle
light as a function of the distance and angle, based on output from
the array of sensors, and prevent the at least one exterior vehicle
light from providing disruptive glare to a driver of the leading
vehicle.
[0008] According to another embodiment of the present invention, an
illumination control system for controlling at least one exterior
vehicle light of a controlled vehicle includes an array of sensors
and a control unit. The array of sensors generates electrical
signals that are provided to the control unit, which is in
communication with the at least one exterior vehicle light. The
control unit is operable to acquire and process electrical signals
received from the array of sensors to determine an illumination
gradient associated with the at least one exterior vehicle light on
a road surface. The control unit compares a sensed illumination
range, which is based on the illumination gradient, to a desired
illumination range and is operable to control the at least one
exterior vehicle light to achieve a desired illumination range.
[0009] According to another embodiment of the present invention, an
illumination control system for controlling at least one exterior
vehicle light of a controlled vehicle includes a discrete light
sensor and a control unit. The discrete light sensor generates
electrical signals, which are provided to the control unit, which
is in communication with the at least one exterior vehicle light.
The control unit is operable to acquire and process electrical
signals from the discrete light sensor to determine when the at
least one exterior vehicle light should transition to a town
lighting mode. The discrete light sensor provides an indication of
an AC component present in ambient light, and the control unit
causes the at least one exterior vehicle light to transition to the
town lighting mode when the AC component exceeds a predetermined AC
component threshold.
[0010] According to still another embodiment of the present
invention, an illumination control system for controlling the at
least one exterior vehicle light of a controlled vehicle includes
an imaging system and a control unit. The imaging system obtains an
image to a front of the controlled vehicle and includes an array of
sensors, which each generate electrical signals that represent a
light level sensed by the sensor. The control unit is in
communication with the at least one exterior vehicle light and is
operable to acquire electrical signals received from the array of
sensors and to separately process the electrical signals. The
control unit is operable to examine a position and brightness of an
on-coming vehicle headlamp over time, as indicated by the
electrical signals provided by the array of sensors, to determine
when a median width is appropriate for the activation of a motorway
lighting mode and causes the at least one exterior vehicle light to
transition to the motorway lighting mode responsive to the
determined median width.
[0011] In another embodiment, an illumination control system for
controlling at least one exterior vehicle light of a controlled
vehicle includes an imaging system, a spatially controlled variable
attenuating filter and a control unit. The imaging system obtains
an image to a front of the controlled vehicle and includes an array
of sensors that each generate electrical signals representing a
light level sensed by the sensor. The filter is positioned
approximate the at least one exterior vehicle light and the control
unit is in communication with the at least one exterior vehicle
light and the filter. The control unit is operable to acquire
electrical signals received from the array of sensors and to
process the electrical signals and control the filter to vary an
illumination range of the at least one exterior vehicle light in
response to the electrical signals and to control the filter to
distinguish between vehicular and non-vehicular light sources.
[0012] In one embodiment, an illumination control system for
controlling at least one exterior vehicle light of a controlled
vehicle includes an imaging system, a spatially controlled
reflector and a control unit. The imaging system obtains an image
to a front of the controlled vehicle and includes an array of
sensors that each generate electrical signals representing a light
level sensed by the sensor. The reflector is positioned approximate
the at least one exterior vehicle light and the control unit is in
communication with the at least one exterior vehicle light and the
reflector. The control unit is operable to acquire electrical
signals received from the array of sensors and to process the
electrical signals and control the reflector to vary an
illumination range of the at least one exterior vehicle light in
response to the electrical signals and to control the reflector to
distinguish between vehicular and non-vehicular light sources.
[0013] In another embodiment, a system for controlling at least one
headlamp of a controlled vehicle includes an array of sensors and a
control unit. The array of sensors is capable of detecting light
levels in front of the controlled vehicle and the control unit is
in communication with the array of sensors and the at least one
headlamp. The headlamp has a high color temperature and the control
unit receives data representing the light levels detected by the
array of sensors to identify potential light sources and
distinguish light that is emitted from the headlamp and reflected
by an object from other potential light sources. The control unit
is also operable to control operation of the at least one headlamp
as a function of the light levels output from the array of
sensors.
[0014] In yet another embodiment a controllable headlamp includes
at least one light source and a spatially controlled variable
attenuating filter positioned approximate the at least one light
source. The filter is controlled to provide a variable illumination
range for the at least one light source and is controlled to
distinguish between vehicular and non-vehicular light sources.
[0015] In still another embodiment, a controllable headlamp
includes at least one light source and a spatially controlled
reflector positioned approximate the at least one light source. The
reflector is controlled to provide a variable illumination range
for the at least one light source and is controlled to distinguish
between vehicular and non-vehicular light sources.
[0016] These and other features, advantages and objects of the
present invention will be further understood and appreciated by
those skilled in the art by reference to the following
specification, claims and appended drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] In the drawings:
[0018] FIG. 1A is an electrical block diagram of an exemplary
imaging system;
[0019] FIG. 1B is a side view of a leading vehicle illustrating
various geometric considerations;
[0020] FIG. 2 is a graph depicting the illumination, as a function
of the mounting height of a trailing vehicle's low-beam headlamps,
on a surface at a rearview mirror position of the leading vehicle
of FIG. 1B;
[0021] FIG. 3 is a graph illustrating road surface illumination as
a function of distance for various headlamp mounting heights;
[0022] FIG. 4 is a side view of another leading vehicle
illustrating various geometric considerations;
[0023] FIG. 5 is a graph depicting the relationship of the position
of an on-coming headlamp image, with respect to a center of the
image, as captured by an array of sensors in a controlled vehicle,
as a function of distance to an on-coming vehicle for various
median widths;
[0024] FIG. 6A is a side view of a high-performance headlamp that
implements a mask, according to an embodiment of the present
invention;
[0025] FIG. 6B is a front view of the mask of FIG. 6A;
[0026] FIG. 6C is a side view of a high-performance headlamp that
implements a mask, according to another embodiment of the present
invention;
[0027] FIGS. 7A-7B are front views of variable transmission devices
that are used to control the illumination produced by headlamps of
a vehicle, according to an embodiment of the present invention;
[0028] FIG. 8 is a side view of a headlamp that includes a
plurality of individual light emitting diodes;
[0029] FIG. 9 is a diagram of a headlamp that utilizes a spatially
controlled reflector;
[0030] FIG. 10 depicts plots of the spectral distributions of
various vehicle exterior lights;
[0031] FIG. 11 depicts plots of the spectral reflectance ratios of
various colored road signs;
[0032] FIG. 12 depicts plots of transmission factors of red and
infrared filter material, according to an embodiment of the present
invention;
[0033] FIG. 13 depicts plots of the quantum efficiency versus
wavelength for an optical system, according to an embodiment of the
present invention;
[0034] FIG. 14 depicts a graph of red-to-clear ratios for various
light sources as detected by an optical system, according to an
embodiment of the present invention;
[0035] FIG. 15A is a side view of a headlamp that implements a
rotatable mask, according to one embodiment of the present
invention;
[0036] FIG. 15B is a front view of the mask of FIG. 15A;
[0037] FIG. 16A is a side view of a headlamp that implements a
rotatable mask, according to another embodiment of the present
invention;
[0038] FIG. 16B is a front view of the mask of FIG. 16A in a first
position; and
[0039] FIG. 16C is a front view of the mask of FIG. 16A in a second
position.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0040] The present invention is directed to a system for
controlling at least one exterior vehicle light (e.g., low-beam
headlamps, high-beam headlamps, tail lamps, fog lamps, etc.) of a
controlled vehicle and includes an array of sensors and a control
unit. The control unit is in communication with the array of
sensors and the at least one exterior vehicle light and is capable
of determining a distance and an angle from the at least one
exterior vehicle light of the controlled vehicle to a leading
vehicle. The control unit is operable to control operation of the
at least one exterior vehicle light as a function of the distance
and angle, based on the output from the array of sensors, and
prevent the at least one exterior vehicle light from providing
disruptive glare to a driver of the leading vehicle.
[0041] In another embodiment of the present invention, an
illumination control system for controlling the at least one
exterior vehicle light of a controlled vehicle includes an array of
sensors and a control unit. The control unit is operable to acquire
and process electrical signals received from the array of sensors
to determine an illumination gradient associated with the at least
one exterior vehicle light on a road surface. The control unit
compares a sensed illumination range, which is based on the
illumination gradient, to a desired illumination range and is
operable to control the at least one exterior vehicle light to
achieve a desired illumination range.
[0042] In yet another embodiment of the present invention, an
illumination control system for controlling the at least one
exterior vehicle light of a controlled vehicle includes a discrete
light sensor and a control unit. The control unit is operable to
acquire and process electrical signals from the discrete light
sensor, which provides an indication of an AC component present in
ambient light. The control unit causes the at least one exterior
vehicle light to transition to the town lighting mode when the AC
component exceeds a predetermined AC component threshold.
[0043] According to still another embodiment of the present
invention, an illumination control system for controlling the at
least one exterior vehicle light of a controlled vehicle includes
an imaging system and a control unit. The imaging system obtains an
image to a front of the controlled vehicle and includes an array of
sensors which each generate electrical signals that represent a
light level sensed by the sensor. The control unit is operable to
examine a position and brightness of an on-coming vehicle headlamp
over time, as indicated by the electrical signals provided by the
array of sensors, to determine when a median width is appropriate
for the activation of a motorway lighting mode.
[0044] Referring now to FIG. 1A, a block diagram of a control
system according to an embodiment of the present invention is
shown. A control system 40 for continuously variable headlamps
includes imaging system 42, control unit 44 and at least one
continuously variable headlamp system 46. The control unit 44 may
take various forms, such as a microprocessor including a memory
subsystem with an application appropriate amount of volatile and
non-volatile memory, an application specific integrated circuit
(ASIC) or a programmable logic device (PLD). The imaging system 42
includes vehicle imaging lens system 48 operative to focus light 50
from a region generally in front of a controlled vehicle onto image
array sensor 52. The imaging system 42 is capable of determining
lateral and elevational locations of headlamps from on-coming
vehicles and tail lamps of leading vehicles. The vehicle imaging
lens system 48 may include two lens systems, one lens system having
a red filter and one lens system having a cyan filter, which
permits the image array sensor 52 to simultaneously view a red
image and a cyan image of the same region in front of the
controlled vehicle and thereby discriminate between tail lamps and
headlamps. The image array sensor 52 may include an array of pixel
sensors.
[0045] The imaging system 42 may include an ambient light lens
system 54 operable to gather light 56 over a wide range of
elevational angles for viewing by a portion of the image array
sensor 52. Alternatively, the light 50, focused through the vehicle
imaging lens system 48, may be used to determine ambient light
levels. Additionally, a light sensor completely separate from the
imaging system 42 may be used to determine ambient light levels. In
one embodiment, the imaging system 42 is incorporated into an
interior rearview mirror mount. In this case, the imaging system 42
may be aimed through a portion of the windshield of the controlled
vehicle that is cleaned by at least one windshield wiper.
[0046] The control unit 44 accepts pixel gray scale levels 58 and
generates image sensor control signals 60 and headlamp illumination
control signals 62. The control unit 44 includes an imaging array
control and analog-to-digital converter (ADC) 64 and a processor
66. The processor 66 receives digitized image data from and sends
control information to the imaging array control and ADC 64, via
serial link 68.
[0047] The control system 40 may include vehicle pitch sensors 70,
to detect the pitch angle of a controlled vehicle relative to the
road surface. Typically, two of the vehicle pitch sensors 70 are
desired. Each of the sensors 70 is mounted on the chassis of the
controlled vehicle, near the front or rear axle, and a sensor
element is fixed to the axle. As the axle moves relative to the
chassis, the sensor 70 measures either rotational or linear
displacement. To provide additional information, the control unit
44 may also be connected to a vehicle speed sensor 72, one or more
moisture sensors 74 and may also be connected to a GPS receiver, a
compass transducer and/or a steering wheel angle sensor.
[0048] Precipitation such as fog, rain or snow may cause excessive
light from headlamps 22 to be reflected back to the driver of the
controlled vehicle. Precipitation may also decrease the range at
which on-coming vehicles and leading vehicles may be detected.
Input from the moisture sensor 74 may therefore be used to decrease
the full range of illumination.
[0049] A headlamp controller 76 controls at least one of the
continuously variable headlamps 22. When multiple headlamp
controllers 76 are utilized, each of the headlamp controllers 76
accepts the headlamp illumination control signals 62, from control
unit 44, and affects the headlamps 22 accordingly to modify an
illumination range of light 78 leaving headlamp 22. Depending on
the type of continuously variable headlamp 22 used, the headlamp
controller 76 may vary the intensity of the light 78 leaving the
headlamp 22, may vary the direction of the light 78 leaving the
headlamp 22, or both.
[0050] The control unit 44 may acquire an image covering a glare
area, which includes points at which a driver of an on-coming
vehicle or leading vehicle would perceive the headlamps 22 to cause
excessive glare. The control unit 44 processes the image to
determine if at least one vehicle is within the glare area. If at
least one vehicle is within the glare area, the control unit 44
changes the illumination range. Otherwise, the headlamps 22 are set
to a full illumination range.
[0051] The changes to illumination range and setting the headlamps
22 to a full illumination range typically occur gradually as sharp
transitions in the illumination range may startle the driver of the
controlled vehicle, since the driver may not be aware of the
precise switching time. A transition time of between one and two
seconds is desired for returning to full illumination range from
dimmed illumination range, corresponding to low-beam headlamps.
Such soft transitions in illumination range also allow the control
system 40 to recover from a false detection of an on-coming vehicle
or leading vehicle. Since image acquisition time is approximately
30 ms, correction may occur without the driver of the controlled
vehicle noticing any change.
[0052] For a controlled vehicle with both high-beam and low-beam
headlamps 22, reducing illumination range may be accomplished by
decreasing the intensity of high-beam headlamps 22 while increasing
the intensity of low-beam headlamps 22. Alternately, low-beam
headlamps can be left on continuously for ambient light levels
below a certain threshold. For a controlled vehicle with at least
one headlamp 22 having a variable horizontal aimed direction, the
aim of headlamp 22 may be moved away from the direction of an
on-coming vehicle when the illumination range is reduced or
changed. This allows the driver of the controlled vehicle to better
see the edge of the road, road signs, pedestrians, animals and the
like that may be on the curb side of the controlled vehicle. The
control unit 44 may determine if any leading vehicle is in a curb
lane on the opposite side of the controlled vehicle from on-coming
traffic. If a leading vehicle is not in the curb lane, reducing the
illumination range may include aiming headlamps 22 away from the
direction of on-coming traffic. If a leading vehicle is detected in
a curb lane, the illumination range may be reduced without changing
the horizontal aim of headlamps 22.
Automatic Aiming of Low-beam Headlamps to Prevent Glare to Other
Vehicles
[0053] Set forth below are some computational examples that
illustrate the relative rearview glare increase provided by high
mounted low-beam headlamps over standard passenger car low-beam
headlamps, as seen by a leading vehicle. These examples are
approximate computations only and are not the result of specific
measurements. The computations assume no obstruction between the
low-beam headlamp of a trailing vehicle and the rearview mirror
surface of the leading vehicle and do not account for rear window
transmission loss. FIG. 1B depicts a leading vehicle 102 that is
being followed by a trailing vehicle (not shown) at a distance of
about 15 meters, with respect to low-beam headlamps of the trailing
vehicle and an internal rearview mirror of the leading vehicle.
[0054] The illumination at the leading vehicle's interior rearview
mirror, located about 1.2 meters above the road, is determined by:
computing the horizontal and vertical angle to each of the
headlamps (assuming a headlamp separation of about 1.12 m),
determining the intensity of the headlamps at that angle and
dividing the determined intensity by the distance squared.
Information on the average position of automotive rearview mirrors
can be obtained from a paper entitled "Field of View in Passenger
Car Mirrors," by M. Reed, M. Lehto and M. Flannagan (published by
the University of Michigan Transportation Research Institute
(UMTRI-2000-23)), which is hereby incorporated herein by reference
in its entirety. Information on the intensity of average low-beam
headlamps can be obtained from a paper entitled "High-Beam and
Low-Beam Headlighting Patterns in the U.S. and Europe at the Turn
of the Millennium," by B. Schoettle, M. Sivak and M. Flannagan
(published by UMTRI (UMTRI 2001-19)), which is also hereby
incorporated herein by reference in its entirety.
[0055] FIG. 2 is a graph that depicts the illumination (as a
function of mounting height of the trailing vehicle's low-beam
headlamps) on a surface at the rearview mirror position of a
leading vehicle, assuming no obstructions and based on the
information set forth above. The graph of FIG. 2 illustrates the
low-beam headlamp mounting height over the legal range, specified
in FMVSS 108, of 0.56 meters to 1.37 meters. A typical passenger
car may have headlamps mounted at about 0.62 meters. In this case,
the glare on the rearview mirror of the leading vehicle is about
2.4 lux. For a vehicle with headlamps mounted at 1 meter, the glare
on the rearview mirror of the leading vehicle increases to 5.8 lux.
The situation becomes much more severe with large trucks and SUVs
with low-beam headlamp mounting heights higher than 1 meter. At the
current U.S. maximum headlamp mounting height, i.e., 1.37 meters,
the glare at the rearview mirror is approximately 91 lux. This
large increase is due to the fact that the intensity of low-beam
headlamps is greatest at about 1.5 degrees below horizontal and
decreases rapidly with increased vertical angle.
[0056] The problem of increased rearview mirror glare with
increased headlamp mounting height could be solved by requiring
manufacturers of larger vehicles to aim their headlamps further
downward when they are mounted above a predetermined height.
However, this solution comes at the cost of decreased illumination
range during normal driving, when no leading vehicle is present.
For example, in order for a vehicle with headlamps mounted at 1
meter to produce the glare equivalent of a vehicle with headlamps
mounted at 0.62 meters (i.e., at 15 meters), the vehicle whose
headlamps are mounted at 1 meter must be aimed downward an
additional 1.4 degrees. FIG. 3 depicts three curves of road
illumination as a function of distance for: a passenger car with
low-beam headlamps mounted at 0.62 meters, a truck or SUV with
low-beam headlamps mounted at 1 meter and a truck or SUV with
low-beam headlamps mounted at 1 meter and aimed downward an
additional 1.4 degrees. As is shown in FIG. 3, the downward aim
reduces the visibility distance of the low-beam headlamps
significantly. As a result, simply aiming the headlamps down is
generally unacceptable during normal driving conditions, when no
leading vehicle is present.
[0057] Additional information about the effects of mirror glare
resulting from different mounting heights can be found in Society
of Automotive Engineers (SAE) publication J2584 entitled "Passenger
Vehicle Headlamp Mounting Height," which is also hereby
incorporated herein by reference in its entirety. This study
recommends that headlamp mounting height be limited to 0.85 meters
to avoid projecting undue glare into leading vehicles.
[0058] A solution which limits the glare to leading vehicles, while
preserving the desired mounting height of the headlamps, involves
detecting the presence of leading vehicles and adjusting the aim of
the low-beam headlamps of the trailing vehicle, accordingly.
Systems to vary the aim of headlamps are currently commercially
available on many production vehicles. These systems typically use
sensors in the axles of a vehicle to detect changes in road pitch
and vary the aim of the headlamps to ensure a constant visibility
distance. Other systems provide motors for adjustment of the aim of
the headlamps, but rely on the driver to manually adjust the aim of
the headlamps through a manual adjustment knob located in the
vehicle. Although such systems were not designed or used in
conjunction with a means to detect a leading vehicle to
automatically reduce the angle of the headlamps, when such vehicles
are detected, such systems can be used for this purpose.
[0059] In one embodiment, such a leading vehicle detection means
may include a camera (i.e., an array of sensors) and an image
processing system as is described in U.S. Pat. No. 6,281,632
entitled "CONTINUOUSLY VARIABLE HEADLAMP CONTROL," issued Aug. 28,
2001, which is hereby incorporated herein by reference in its
entirety, and PCT Application No. PCT/US01/08912, entitled "SYSTEM
FOR CONTROLLING EXTERIOR VEHICLE LIGHTS," published Sep. 27, 2001
(WO 01/70538), which is also hereby incorporated herein by
reference in its entirety. Such systems are capable of detecting
the tail lamps of leading vehicles and may determine the
approximate distance to a leading vehicle by the brightness of the
tail lamps in an image or by the separation distance between the
two tail lamps of the leading vehicle. Since tail lamps are
typically mounted below the rear window of most vehicles, the tail
lamps' position in the image can also be used to determine if
excess glare is likely to be projected into the rearview mirror of
the leading vehicle.
[0060] FIG. 4 depicts a leading vehicle 402 (with tail lamps
located 1 meter above the road) whose rearview mirror is 15 meters
ahead of low-beam headlamps of a trailing vehicle (not shown). The
angle between the tail lamps of the leading vehicle and the camera
of the trailing vehicle can be determined from the position of the
tail lamps in the image. It should be appreciated that the
difference in mounting height between a camera mounted within a
vehicle and low-beam headlamps of the vehicle is fixed and,
therefore, can be known for any given vehicle. As mentioned above,
the distance to the leading vehicle can be determined in a number
of ways. For example, the distance to the leading vehicle can be
estimated by the brightness of the tail lamps of the leading
vehicle in the image. Alternatively, for most vehicles with two
tail lamps, the distance between the two tail lamps, which remains
within a reasonable range for production vehicles, can be used to
estimate the distance to the leading vehicle. For motorcycles or
vehicles with only one tail lamp, brightness can be used to
estimate the distance between the trailing and leading vehicles.
Finally, other devices for determining distance, such as a radar,
laser or ultrasonic sensors, may be used. Such systems are already
incorporated in many production vehicles for use in conjunction
with, for example, parking aids and adaptive cruise control
systems. For an example of one such system see U.S. Pat. No.
6,403,942, entitled "AUTOMATIC HEADLAMP CONTROL SYSTEM UTILIZING
RADAR AND AN OPTICAL SENSOR," the entire disclosure of which is
hereby incorporated herein by reference.
[0061] Once an estimate of the distance from the trailing vehicle
to the leading vehicle is determined, the angle between the
controlled vehicle's headlamps and the leading vehicle (e.g., the
rearview mirror of the leading vehicle) can be determined. A
detailed method for analyzing an image to determine the location of
light sources within an image is set forth in PCT Application No.
PCT/US01/08912. Then, if the trailing vehicle is close enough to
the leading vehicle for glare to disrupt the driver of the leading
vehicle, the aim of the headlamps can be set downward to a level
which does not cause disruptive glare (alternatively, or in
addition, the intensity of the headlamps may be adjusted). When no
leading vehicles are within a close range, the headlamps of the
trailing vehicle can be aimed normally for proper road
illumination. Modifications to the above embodiment may include a
variety of methods for reducing the intensity of light directed
towards the detected light source. These methods include, but are
not limited to: modifying the horizontal direction aim of the
headlamps, modifying the vertical direction aim of the headlamps,
modifying the intensity of the headlamps, enabling or disabling one
of a plurality of exterior lights and selectively blocking or
attenuating light from the exterior lights in the direction of the
detected light source.
Automatic Aiming of Headlamps Using an Image Sensor
[0062] As headlamp technology improves and vehicle headlamps have
become brighter, the potential for causing glare to on-coming and
leading drivers has become greater. Low-beam headlamps, which are
designed to prevent glare to on-coming drivers, are typically aimed
1.5 degrees downward and about 1.5 degrees right, with a sharp
reduction in intensity above the peak. However, variations in the
road and in vehicle loading can regularly cause the peak of these
headlamps to shine directly into the eyes of an on-coming driver.
This problem becomes much more severe with new technology
headlamps, such as high-intensity discharge (HID) headlamps, and,
as a result, various groups have attempted to design systems that
perform active leveling of these brighter headlamps. Current
automatic leveling systems provide sensors on each axle to
determine the pitch of the vehicle, relative to the road. Such
systems may also incorporate vehicle speed sensing to anticipate
variations in vehicle pitch with acceleration. These systems
require that the headlamp aiming, relative to the vehicle, be known
and calibrated to properly aim the headlamps to compensate for
vehicle pitch variations.
[0063] An embodiment of the present invention generally improves on
prior automatic headlamp leveling systems by sensing the actual
beam pattern, provided by, for example, the low-beam headlamps, on
the road separately, or in combination with the sensing of the
vehicle's pitch. By looking at the illumination gradient on the
road, it is possible to compare the actual illumination range to
the desired illumination range and compensate for variance by
adjusting the headlamp's aim. The desired illumination range may be
constant or may be a function of the current vehicle speed, ambient
light level, weather conditions (rain/fog/snow), the presence or
absence of other vehicles, the type of roadway or other vehicle
and/or environmental conditions. For example, a driver of a vehicle
traveling at a high rate of speed may benefit from a longer
illumination range, while drivers traveling in fog may benefit from
headlamps aimed lower. Because road reflectance is generally
variable, it is not normally sufficient to look only at the
illumination on the road to determine the illumination range.
Rather, it is generally useful to look at the light level gradient
with increasing distance on the road surface.
[0064] As is shown in FIG. 3, road illumination decreases as the
distance from the vehicle increases. By looking at a vertical strip
of pixels in the image corresponding to a particular horizontal
angle and a range of vertical angles and comparing the change in
brightness across this strip to an appropriate curve in FIG. 3,
based on the mounting height of the low-beam headlamps for a
particular vehicle, the current aim of the headlamps can be
determined and adjusted to provide a desired illumination range.
Alternatively, a vertical linear array of photosensors can be used
to image road illumination and, thus, provide the road illumination
gradient.
[0065] Further, in certain circumstances, reflections from lane
markings can be used to indicate when a road bend is ahead of the
controlled vehicle such that a direction of the headlamps of the
controlled vehicle can be controlled to bend with the road.
Alternatively, in vehicles that include a navigation system, e.g.,
a land-based system (such as Loran) or satellite-based system (such
as a global positioning system (GPS)), direction of the headlamps
of the controlled vehicle can be varied based on a location of the
vehicle.
Control of AFS Lighting Using an Image Sensor
[0066] Adaptive front lighting systems (AFSs) are a new generation
of forward lighting systems, which contain a variety of
technologies for improving a vehicle's forward illumination. In
addition to standard low and high beams, AFS lighting systems may
include, for example, the following illumination modes:
[0067] bending lights--lamps in which the aim is varied
horizontally or separate lamps are lit to provide better
illumination when turning;
[0068] bad weather lights--lamps which provide good spread
illumination on the road immediately in front of a vehicle to aid
the driver in seeing obstacles in rain and fog;
[0069] motorway lighting--lamps which provide a greater
illumination range at higher speeds when traveling on a motorway
(i.e., a road with lanes in opposite directions separated by a
median); and
[0070] town lighting--lamps with a shorter and wider illumination
range appropriate for driving in town and reducing glare to
pedestrians and other drivers.
[0071] The goal of a typical AFS lighting system is to provide
automatic selection of the different lighting modes. For example,
rain sensing or fog sensing can be used to activate bad weather
lights and steering wheel angle can be used to activate bending
lights. However, the activation of the other illumination modes is
not as straight forward. That is, activation of motorway lighting
modes and town lighting modes requires a knowledge of the
environment. Vehicle speed can be used to activate town lighting;
however, it is possible that the illumination range may be
unnecessarily reduced when traveling at a low speed out of town.
Also, ambient light level may be a useful indication of traveling
in a town. Finally, as is disclosed in U.S. patent application Ser.
No. 09/800,460, entitled "SYSTEM FOR CONTROLLING EXTERIOR LIGHTS,"
now U.S. Pat. No. 6,587,573, which is hereby incorporated herein by
reference in its entirety, a vehicle including a global positioning
system (GPS) with a map database indicating the types of roads on
which a vehicle is traveling may be used to determine a proper mode
of lighting. However, such systems are expensive and map data may
not be available for all areas of the world. Additionally,
inaccuracies in GPS systems may occasionally cause such a system to
incorrectly identify the road on which a vehicle is traveling.
[0072] According to the present invention, a town is detected
through the use of an optical sensor. A discrete light sensor such
as that described in PCT Application No. PCT/US00/00677, entitled
"PHOTODIODE LIGHT SENSOR," by Robert H. Nixon et al. and published
Jul. 27, 2000 (WO 00/43741), which is hereby incorporated herein by
reference in its entirety, may be utilized. This sensor may be used
to measure the ambient light and also measure the 120 Hz (or 100 Hz
in Europe) intensity ripple component, produced by discharge street
lighting powered by a 60 Hz AC source, by obtaining several light
level measurements during different phases of the intensity ripple.
If there is a significant AC component in the ambient light level
and the vehicle speed is low (for example, less than 30 mph), it is
likely that the vehicle is traveling in a town with significant
municipal lighting and town lighting can be activated. By examining
the quantity of AC lights and the vehicle's speed, town driving
conditions can be accurately determined. The magnitude of the AC
component may be used in combination with the ambient light level
and the vehicle's speed to make a proper determination of the use
of town lighting. For example, if the ambient light level is
sufficient such that there would not be a significant safety risk
from the reduced illumination range, the speed of the vehicle is
indicative of driving in a town (e.g., below about 30 mph) and
there is a significant AC component in the ambient lighting, town
lighting may be activated.
[0073] Alternatively, the transition from normal low-beam lighting
to town lighting may be continuous with the illumination range
being a continuous function of ambient lighting and vehicle speed
so as to produce a sufficient illumination range for given
conditions. This provides the benefit of ensuring a safe
illumination range and minimizing the glare to pedestrians or other
vehicles. Finally, as an alternative to the use of a discrete light
sensor, a sensor array, such as an image sensor, may be used to
identify street lamps and activate town lighting if the number of
streetlamps detected in a period of time exceeds a threshold (along
with consideration of the vehicle's speed and ambient lighting).
Methods for detecting streetlamps using an image sensor are
described in detail in the above-incorporated patent and patent
application. The light sensor may be provided in various places
throughout a motor vehicle, e.g., provided in a rearview mirror
housing. Further, such a light sensor may also be used for various
other functions (e.g., sun load), such as those set forth in U.S.
Pat. No. 6,379,013, entitled "VEHICLE EQUIPMENT CONTROL WITH
SEMICONDUCTOR LIGHT SENSORS," which is hereby incorporated herein
by reference in its entirety.
[0074] Motorway conditions can be also be determined by using an
image sensor to detect the lane separation or median of a motorway.
This can be accomplished by directly looking at the angular
movement of the headlamps of on-coming vehicles in several
subsequent images. The detection of the movement of an object in a
series of images is further described in U.S. patent application
Ser. No. 09/799,310 entitled "IMAGE PROCESSING SYSTEM TO CONTROL
VEHICLE HEADLAMPS OR OTHER VEHICLE EQUIPMENT," filed Mar. 5, 2001,
now U.S. Pat. No. 6,631,316, which is hereby incorporated herein by
reference in its entirety, FIG. 5 illustrates three curves, which
represent different motorway median widths, and how the position of
an on-coming headlamp in an image varies as a function of the
distance between two vehicles that are traveling in different
directions are converging. By examining the position and brightness
of the headlamp in an image and by examining how the position of
the headlamp image varies over time for the given controlled
vehicle's speed, the approximate spacing of the median can be
determined and motorway lighting can be activated if the median is
of a sufficient width. Finally, if no headlamps are present, and no
tail lamps of leading vehicles are present, high beams can be
activated.
Headlamp with Controllable Beam Pattern
[0075] FIG. 6A schematically illustrates an exemplary
high-performance headlamp, commonly referred to as a projector
headlamp, which is utilized in conjunction with a mask 603. A bulb
602 is placed in front of a reflector 601. The bulb 602 may be of a
conventional incandescent (e.g., tungsten-halogen) type,
high-intensity discharge (HID) type or other suitable bulb type, or
may be the output from a remote light source as is described
further below. A lens 604 directs light from the bulb 602 and
reflected by the reflector 601 down the road. The mask 603
establishes a cutoff point to prevent light above the horizon 605
from being directed down the road. The mask 603 absorbs or reflects
light rays, such as light ray 607, which would cause glare to
another vehicle. Light rays, such as light ray 606, which project
below the cutoff point, pass through lens 604 as they are not
blocked by the mask 603. The mask 603, typically, has a shape, such
as that shown in FIG. 6B, which contains a step allowing a slightly
higher cutoff point to the right of the vehicle.
[0076] A modification to this type of lamp construction includes a
solenoid to control the mask 603. Using the solenoid, the mask 603
can be removed from the position in front of the bulb 602. When
removed, rays, such as the ray 607, project through the lens 604
and down the road, thus establishing a much longer illumination
range. In this way, the lamp with mask 603 removed can function as
a high-beam headlamp.
[0077] In the present invention, the mask 603 may also be
controlled by a motor to move vertically relative to the bulb 602,
lens 604 and reflector 601, as shown in FIG. 6C. By lowering the
mask 603, the cutoff angle is raised and the illumination range is
extended. By raising the mask 603, the cutoff angle is lowered and
illumination range is reduced. The movement of the mask 603 can be
used to establish different lighting functions, such as town or
motorway lighting, or to increase the illumination range gradually
with increased speed. Additionally, the movement of the mask 603
can also be used to establish the vertical aim of the headlamp and
therefore compensate for vehicle pitch variations as described
herein above. This method of aiming the headlamp is advantageous
because only the relatively small mask 603 requires movement,
rather than the entire lamp set which is moved in some
auto-leveling systems today.
[0078] In another embodiment of the present invention, the mask 603
is replaced with a spatially controlled variable attenuating
filter. This filter can be formed as an electrochromic variable
transmission window, which has the capability to selectively darken
various regions of the window. This window may contain a liquid or
solid state (e.g., tungsten oxide) electrochromic material that is
capable of withstanding the high temperatures achieved in close
proximity to the bulb. Alternatively, this window may be a liquid
crystal device (LCD), a suspended particle device or other
electrically, chemically or mechanically variable transmission
device. A suitable electrochromic device is disclosed in U.S. Pat.
No. 6,020,987 entitled "ELECTROCHROMIC MEDIUM CAPABLE OF PRODUCING
A PRE-SELECTED COLOR," which is hereby incorporated herein by
reference in its entirety.
[0079] An example of such a variable transmission device 700 is
shown in FIGS. 7A and 7B. The device 700 is constructed using two
pieces of glass with electrochromic material contained between. On
the inner surface of each piece of glass is a transparent
conductive electrode, such as indium tin oxide (ITO), which is
patterned on at least one of the surfaces to selectively darken
different regions of the window by electronic control. In FIG. 7A,
these regions are horizontal strips 701, which may optionally
contain a slight step. By selectively darkening all of the strips
701, below a certain level, a variable cutoff can be achieved
analogous to moving the mask 603 up or down as previously described
with reference to FIG. 6C. While there is some space shown for
clarity between each of the strips 701, in practice, this spacing
is very small. Therefore, the absorbing region below the cutoff is
essentially contiguous. Finally, it is possible to only partially
darken the various stripes, thereby forming a more gradual
cutoff.
[0080] Alternatively, the window 700 may contain several
independently controlled blocks 702 as shown in FIG. 7B. There may
be any number of blocks, depending on the granularity of control
that is desired. By selectively darkening these blocks, almost any
desired beam pattern can be achieved. For example, all blocks below
a cutoff may be darkened to achieve a low-beam pattern. All blocks
may be transparent to achieve a high-beam pattern. If an on-coming
or preceding vehicle is detected by an image sensor, as previously
described, blocks can be selectively darkened to block light
corresponding to the angles at which the vehicle is detected and
thereby glare to this vehicle can be prevented without compromising
the illumination to the remainder of the forward field. Further, as
used herein, distinct beam patterns may be achieved in various
manners, e.g., changing the intensity of one or more light sources,
changing the aiming direction of one or more light sources,
changing the distribution of light provided by one or more light
sources and/or activating multiple light sources in
combination.
[0081] Yet another alternative is for mask 603 to be constructed as
a spatially controlled reflector. Such a reflector may be a
reversible electrochemical reflector, such as that described in
U.S. Pat. Nos. 5,903,382; 5,923,456; 6,166,847; 6,111,685 and
6,301,039, the entire disclosures of which are hereby incorporated
herein by reference. In such a device, a reflective metal is
selectively plated and de-plated on a surface to switch between a
reflective and transmissive state. A metal-hydride switchable
mirror, available from Philips Electronics, may also be used to
provide a spatially controlled reflector. The spatially controlled
reflector may be formed as a single contiguous reflector, allowing
for a switch from high to low beam or may be patterned, such as in
FIGS. 7A and 7B, to allow activation of individual segments of the
mirror and, thus, provide spatial control of the transmitted beam.
The use of a spatially controlled mirror provides the advantage
that a reflective device reflects light rays 607 back into
reflector 601 and, thus, these rays are conserved, rather than
absorbed and, as such, are available to be projected in other areas
of the beam. This provides a headlamp with improved efficiency, as
compared to headlamps that absorb light rays to provide a desired
illumination pattern. Additionally, by reflecting light rays,
rather than absorbing the light rays, the mask may not become as
hot and, thus, the headlamp becomes potentially more robust.
[0082] In yet another embodiment, a spatially controlled reflector
is used to construct a headlamp in accordance with FIG. 9. A bulb
901 and reflector 902 form a light source, which projects incident
rays 906 onto a spatially controlled reflector 903. The light
source may be any type of light source suitable for automotive use,
such as a halogen source, a high-intensity discharge (HID) source
or a light emitting diode (LED) source. Incident rays 906 may also
come from a remote light source through a fiber bundle or light
pipe. The spatially controlled reflector 903 contains a plurality
of switchable mirrors 905, which can be turned on and which reflect
incident rays 906 (as reflected rays 907), which are then projected
by lens 904 down the road. When turned off, the incident rays 906
are reflected away from the lens 904, transmitted through the
reflector 903 or absorbed and, thus, not projected by the lens 904.
Alternatively, the rays may be redirected to increase the
illumination of other portions of a headlamp beam.
[0083] The spatially controlled reflector may be, for example, a
custom designed digital micro-mirror device (DMD) available from
Texas Instruments. DMDs are micro-machined arrays of tiny mirrors
which can be switched between two angles and are currently widely
used for video projectors. The application of a DMD to produce a
spatially configurable headlamp is analogous to that of a video
projector. However, high resolution, variable color and video frame
rates that are necessary for video projectors are not necessary in
a headlamp that utilizes a DMD. Thus, a control system for a
headlamp can be simpler than a control system for a video
projector. However, the present invention is not limited to any
particular number of mirrors or switching rate. As few as one
mirror for switching between two beam patterns to many thousands of
mirror segments for providing a completely configurable beam
pattern may be used.
[0084] As an alternative to a DMD, the spatially controlled
reflector may be constructed as a reversible electro-chemical
reflector or a metal-hydride switchable mirror as described above.
Finally, a solid mirror with a patterned attenuating filter (such
as an electrochromic filter or LCD) placed in front of the mirror
may be used to provide the same function. It should be appreciated
that controllable reflectors and/or attenuators may be used to
select a beam pattern, based upon one or more driving conditions,
at which point a control unit (based upon input received from a
sensor array) may cause the reflector and/or attenuator to redirect
or inhibit light that would cause glare to a sensed object. As is
described herein, systems implementing a control unit in
conjunction with a sensor array are configurable to distinguish
between reflected light and light from another light source,
through manipulation of a light source or sources of a controlled
vehicle headlamp. In general, the light source(s) of the headlamp
embodiments of FIGS. 8 and 9 can be cycled such that reflected
light can be distinguished from light from another light source.
Further, depending upon the construction of the headlamp, the
embodiment of FIGS. 7A-7B may also be cycled to distinguish
reflected light from light from another light source.
[0085] The embodiment of FIG. 9 generally functions in a similar
manner as the previously described embodiments. By selecting which
mirrors or mirror segments are on, the on/off duty cycle of the
mirror segments, or if the mirror segments are continuously
variable, the reflectance levels of any conceivable beam pattern
can be achieved. The lamp can provide a basic low-beam function
and/or provide high beams, bending lamps, motorway lighting, bad
weather lighting or any intermediate state. Additionally, when used
with a camera to detect the direction to other vehicles, mirrors
can be turned off to prevent light rays in that direction from
being projected and, thus, glaring the other vehicle. Further, as
mentioned above, the mirrors may be controlled such that reflected
light, e.g., a non-vehicular light source, can be distinguished
from light provided by another light source, e.g., a vehicular
light source.
[0086] Yet another headlamp configuration suitable for use with the
present invention is described with reference to FIG. 8. In this
embodiment, the reflector 601, bulb 602, and mask 603 are replaced
by a high-intensity LED array 801, which is placed approximately in
the focal plane of the lens 604. High intensity LED arrays suitable
for use as automotive headlamps are described in PCT application
PCT/US01/08912, previously incorporated herein by reference, and in
U.S. Pat. No. 6,639,360 to Roberts et al., filed on Apr. 13, 2001.
These arrays may produce white light illumination through a
binary-complementary combination of amber and blue-green LED
emitters.
[0087] LEDs 802 or groups of LEDs 802 in the LED array 801 are
configured to be independently, and optionally variably, energized
by electronic control unit. The light from LEDs 802 (or groups of
closely spaced LEDs) is projected to a particular region in front
of the lamp by the lens 604. By selectively energizing these LEDs
802, a desired beam pattern can be achieved in a fashion similar to
that achieved by selectively darkening various blocks 702 in the
previously described embodiment of FIG. 7B. For example, all LEDs
below a cutoff point may be energized to produce a desired
illumination range. If other vehicles are identified by an imaging
system, LEDs which project light in the direction of the identified
vehicle may be shut off or reduced in intensity to prevent glare to
the vehicle. All other LEDs may remain lit to provide illumination
in regions where no vehicles are present. Further, in headlamps
incorporating LEDs, a portion of the LEDs can be dimmed or turned
off to distinguish on-coming vehicles from other light sources,
such as reflectors.
[0088] The above described embodiments provide headlamps with a
controllable and reconfigurable beam pattern. These headlamps may
be used with the methods described above to provide a fully
automatic vehicle forward light system, which can provide numerous
functions, including: low beams, high beams, motorway lighting,
town lighting, bad weather lighting, bending lamps, auto leveling
and anti-glare control to prevent glare to on-coming or preceding
drivers. These particular lighting modes are only exemplary and
control may switch between discrete modes or may be continuous.
[0089] A variety of sensors may provide input to a control system
to determine the appropriate beam pattern for the given driving
conditions. These sensors may include, for example, a camera,
ambient light sensor, speed sensor, steering wheel angle sensor,
temperature sensor, compass, a navigation system (e.g., a
land-based (such as Loran) or satellite-based (such as GPS)), pitch
sensors and various user input switches. Additionally, it is
envisioned that a driver input may be provided for setting various
preferences, such as the thresholds for switching between various
beam patterns, the brightness of the lamps, the sharpness of beam
cutoffs, the color of the lamps, the degree of bending, etc. A GPS,
user input or factory setting may be provided to indicate the
location of the vehicle to ensure compliance with various laws.
Thus, identical lamp assemblies may be used in various countries
with a simple selection of location.
[0090] The control methods described herein may be utilized with
the lamp embodiments described herein or with other lamp types.
Similarly, the lamp embodiments described herein may be controlled
by a variety of methods, including those described herein, those
described in other references incorporated herein or other methods.
Finally, the lamp embodiments described herein may be used alone,
in any number or configuration, or in conjunction with standard
lamps, fixed bending lamps, fog lamps, foul weather lamps or other
types of lamps. The control methods may control both the
configurable lamps and any other type of lamp.
[0091] In one embodiment of the present invention, various external
vehicle lights are used, such as high-intensity discharge (HID)
headlamps, tungsten-halogen and blue-enhanced halogen headlamps, to
provide greater ability to distinguish reflections from various
roadside reflectors and signs from headlamps of on-coming vehicles
and tail lamps of leading vehicles. Additionally, specific spectral
filter material may be employed in combination with the external
vehicle lights to produce desired results.
[0092] It is generally desirable for an automatic vehicle exterior
light control system to distinguish headlamps of on-coming vehicles
and tail lamps of leading vehicles from non-vehicular light sources
or reflections off of signs and roadside reflectors. The ability to
distinguish these various objects may be enhanced with an optimal
combination of various color, ultra-violet and infrared spectral
filters. FIG. 10 depicts plots of the spectral content of different
types of vehicular-related light sources and FIG. 11 depicts plots
of the spectral reflectance of various colored signs. FIG. 12
depicts plots of the percent transmission of red and infrared
spectral filters used in one embodiment of the present invention,
and FIG. 13 depicts a plot of the quantum efficiency of an optical
system in accordance with an embodiment of the present invention.
Numerical data depicted by the plots of FIGS. 10-13 is utilized, as
described in further detail below, to categorize various light
sources.
[0093] The brightness of a given detected light source can be
estimated by multiplying the spectral output of the source, as
shown in FIG. 10, by the infrared spectral filter transmission
factor, as shown in FIG. 12, multiplied by the spectral response of
the pixel array, as shown in FIG. 13. For red filtered pixels, this
value is further multiplied by the transmission factor of the red
spectral filter. The brightness of detected reflections from road
signs can be estimated by multiplying the controlled vehicle's
headlamp spectral output, as shown in FIG. 10; by the spectral
reflectance factor of the sign, as shown in FIG. 11; the infrared
spectral filter transmission factor, as shown in FIG. 12; and the
spectral response of the optical system, as shown in FIG. 13. For
red spectral filtered pixels, the preceding result is then
multiplied by the red spectral filter transmission factor, as shown
in FIG. 12.
[0094] The ratio in brightness between the object projected onto
the red filtered pixels in relation to the object projected onto
the non-red filtered pixels can be used to determine the relative
redness of an object. This ratio can then be utilized to determine
if the object is a tail lamp or a headlamp. FIG. 14 depicts the
computed ratios of the brightness of objects projected onto red
filtered pixels relative to those same objects projected onto the
non-filtered pixels. As is shown in FIG. 14, tail lamps have a much
higher red-to-clear ratio than headlamps, or most other
objects.
[0095] Discrimination between light sources can be further improved
with the use of blue-enhanced headlamps. Such headlamp bulbs are
commercially available and produce a bluer, or cooler, color light
that more closely approximates natural daylight. These headlamp
bulbs are sometimes used in combination with high-intensity
discharge (HID), low-beam lights to more closely match the color.
Finally, halogen-infrared (HIR) bulbs, which contain a coating to
reflect infrared light back into the bulb, have a cooler light
output and may be used. HIR bulbs have the advantage of emitting
less red light as a percentage of their total output, as shown in
FIG. 10. As a result, the image of signs reflecting light will have
a lower brightness on red filtered pixels than on non-red filtered
pixels. Other light sources, which emit less red light in
proportion to the total amount of light, may be advantageously used
to minimize the false detection of road signs and reflections off
of other objects; HID high-beam lights and LED headlamps are
examples of such sources.
[0096] It is common to classify the color of white light sources
(such as headlamps) by their color temperature or correlated color
temperature. Light sources with a high color temperature have a
more bluish hue and are, misleadingly, typically called "cool-white
light" sources. Light sources with a more yellow or orangish hue
have a lower color temperature and are, also misleadingly, called
"warm white light" sources. Higher color temperature light sources
have a relatively higher proportion of short wavelength visible
light to long wavelength visible light. The present invention can
benefit from the use of higher color temperature headlamps due to
the reduced proportion of red light that will be reflected by signs
or other objects that could potentially be detected.
[0097] Correlated color temperature for non-perfect Planckian
sources can be estimated by computing the color coordinates of the
light source and finding the nearest temperature value on the
Planckian locus. Calculation of color coordinates is well known in
the art. The text entitled MEASURING COLOUR, second edition, by R.
W. G. Hunt, incorporated in its entirety herein by reference, is
one source for known teachings in the calculation of color
coordinates. Using the CIE 1976 USC (u', v') color space, a
standard halogen headlamp was measured to have color coordinates of
u'=0.25 & v'=0.52. From these coordinates, a correlated color
temperature of 3100 Kelvin is estimated. The blue-enhanced headlamp
of FIG. 10 has color coordinates of u'=0.24 and v'=0.51 and, thus,
a correlated color temperature of approximately 3700 Kelvin. A
measured high-intensity discharge (HID) headlamp has color
coordinates of u'=0.21 and v'=0.50 and, thus, a correlated color
temperature of 4500 Kelvin. In general, the present invention can
benefit when the controlled vehicle is equipped with headlamps
having a correlated color temperature above about 3500 Kelvin.
[0098] FIG. 15A schematically illustrates a headlamp 1500, which
includes a rotatable mask 1503 and a bulb 1502 that is positioned
in front of a reflector 1501. The bulb 1502 may be of a
conventional incandescent (e.g., tungsten-halogen) type,
high-intensity discharge (HID) type or other suitable bulb type, or
may be the output from a remote light source as is described above.
A lens 1504 directs light from the bulb 1502 and reflected by the
reflector 1501 down the road. The mask 1503 establishes a cutoff
point to prevent light vertically above the horizon 1505 from being
directed down the road. The mask 1503 absorbs or reflects light
rays, such as light ray 1507, which may cause glare to another
vehicle and allows an illumination pattern provided by the headlamp
1500 to be changed. Light rays, such as light ray 1506, which
project below the cutoff point, pass through lens 1504 as they are
not blocked by the mask 1503.
[0099] The mask 1503, may have a number of different shapes, such
as the oval shown in FIG. 15B, and may be implemented as an
irregular cylinder that is coupled to a motor M, e.g., a
stepper-motor, off-center so as to achieve a variable illumination
pattern as the mask 1503 is rotated, i.e., the mask 1503 changes
how much light is blocked as it is rotated. In this manner, the
mask 1503 can provide an oblong profile in the vertical direction,
when the mask 1503 is implemented as an oval cylinder.
[0100] In a typical illumination system that implements the
headlamp 1500, a control unit receives electrical signals from a
sensor array and controls the rotated position of the mask 1503 by
sending control signals to the motor M to achieve a desired
illumination pattern. It should be appreciated that a homing or
feedback technique may be employed to assure that the mask 1503 is
in a known position and, thus, able to provide a desired
illumination pattern. As the mask 1503 is rotated, the amount of
light that is attenuated by the mask 1503 changes and in this
manner, the movement of the mask 1503 can be used to establish a
wide variety of different lighting functions. Since the rotation of
the mask 1503 can be used to establish a vertical aim of the
headlamp 1500, vehicle pitch variation compensation, as described
herein above, can also be achieved. This technique of aiming a
headlamp is advantageous as only the relatively small mask 1503
requires movement, rather than the entire lamp set which is moved
in some commercially available auto-leveling systems.
[0101] FIG. 16A schematically illustrates a headlamp 1600, which
includes a rotatable mask 1603 that includes a plurality of
profiles, according to another embodiment of the present invention.
These profiles allow an illumination pattern to be controlled in
both horizontal and vertical directions. The headlamp 1600 includes
a bulb 1602 that is placed in front of a reflector 1601. The bulb
1602 may be of a conventional incandescent (e.g., tungsten-halogen)
type, high-intensity discharge (HID) type or other suitable bulb
type, or may be the output from a remote light source as is
described above. A lens 1604 directs light from the bulb 1602 and
reflected by the reflector 1601 down the road. The mask 1603
establishes a cutoff point to prevent light above the horizon 1605
from being directed down the road. The mask 1603 absorbs or
reflects light rays, such as light ray 1607, which would cause
glare to another vehicle. Light rays, such as light ray 1606, which
project below the cutoff point, pass through the lens 1604 as they
are not blocked by the mask 1603.
[0102] The mask 1603 may simultaneously have a number of different
incorporated profiles, such as the profiles shown in FIGS. 16B and
16C, and is coupled to a motor M, e.g., a stepper-motor, at an end
so as to achieve a variable illumination pattern as the mask 1603
is rotated to select a desired profile. For example, by providing
different horizontal profiles one can effect where light is aimed,
e.g., left or right, and/or change the width of a light beam.
Similar to the headlamp 1500, the headlamp 1600 may function with a
control unit that receives electrical signals from a sensor array
and controls the rotated position of the mask 1603 by sending
control signals to the motor M to achieve a desired illumination
pattern. It should be appreciated that a homing or feedback
technique may also be employed to assure that the mask 1603 is in a
known position and, thus, able to provide a desired illumination
pattern.
[0103] As with the rotation of the mask 1503, the rotation of the
mask 1603 can also be used to establish different lighting
functions, such as town or motorway lighting, or to increase the
illumination range gradually with increased speed. Additionally,
the rotation of the mask 1603 can also be used to establish both
vertical and horizontal aim of the headlamp and therefore also
compensate for vehicle pitch variations, as described herein above.
This method of aiming the headlamp is also advantageous due to the
fact that only the relatively small mask 1603 requires
rotation.
[0104] The above description is considered that of the preferred
embodiments only. Modification of the invention will occur to those
skilled in the art and to those who make or use the invention.
Therefore, it is understood that the embodiments shown in the
drawings and described above are merely for illustrative purposes
and not intended to limit the scope of the invention, which is
defined by the following claims as interpreted according to the
principles of patent law, including the Doctrine of
Equivalents.
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