U.S. patent application number 11/180346 was filed with the patent office on 2005-11-03 for control system to automatically control vehicle headlamps.
Invention is credited to Bechtel, Jon H., Roberts, John K., Stam, Joseph S..
Application Number | 20050242740 11/180346 |
Document ID | / |
Family ID | 25258611 |
Filed Date | 2005-11-03 |
United States Patent
Application |
20050242740 |
Kind Code |
A1 |
Stam, Joseph S. ; et
al. |
November 3, 2005 |
Control system to automatically control vehicle headlamps
Abstract
An automatic vehicle headlamp dimming system which includes an
optical system and an imaging processing system. The optical system
is configured to discriminate between headlamps and tail lamps, and
focus the light rays from the headlamps and tail lamps on different
portions of a pixel sensor array. The optical system as well as the
image processing system provides for relatively increased
discrimination of headlamps and tail lamps of other vehicles and
also enables the high beam headlamps of the control vehicle to be
controlled as a function of the distance as well as horizontal
angular position of other vehicles relative to the controlled
vehicle.
Inventors: |
Stam, Joseph S.; (Holland,
MI) ; Bechtel, Jon H.; (Holland, MI) ;
Roberts, John K.; (East Grand Rapids, MI) |
Correspondence
Address: |
BRIAN J. REES
GENTEX CORPORATION
600 NORTH CENTENNIAL STREET
ZEELAND
MI
49464
US
|
Family ID: |
25258611 |
Appl. No.: |
11/180346 |
Filed: |
July 13, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11180346 |
Jul 13, 2005 |
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10677453 |
Oct 2, 2003 |
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6919548 |
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10677453 |
Oct 2, 2003 |
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09874197 |
Jun 5, 2001 |
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6653614 |
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09874197 |
Jun 5, 2001 |
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09151487 |
Sep 11, 1998 |
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6255639 |
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09151487 |
Sep 11, 1998 |
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08831232 |
Apr 2, 1997 |
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5837994 |
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Current U.S.
Class: |
315/82 ;
315/77 |
Current CPC
Class: |
H04N 5/335 20130101;
B60Q 1/143 20130101; B60Q 1/085 20130101; B60Q 2300/333 20130101;
B60Q 2300/337 20130101; B60Q 2300/312 20130101; B60Q 2300/21
20130101; B60Q 2300/45 20130101; B60Q 1/18 20130101; B60Q 2300/114
20130101; B60Q 2300/332 20130101; G06K 9/00825 20130101; B60Q
2300/41 20130101; B60Q 2300/134 20130101; B60Q 1/1423 20130101;
B60Q 2300/116 20130101; B60Q 2300/122 20130101; B60Q 2300/322
20130101; B60Q 2300/42 20130101; B60Q 2300/3321 20130101; B60Q
2300/054 20130101; B60Q 2300/324 20130101; B60Q 2300/314 20130101;
B60Q 2300/112 20130101 |
Class at
Publication: |
315/082 ;
315/077 |
International
Class: |
B60Q 001/00 |
Claims
What is claimed is:
1. An automatic vehicle exterior light control, comprising: an
image array sensor configured to capture at least one frame; a
controller configured to identify at least one AC powered light
source; said controller is further configured to distinguish
between external sources of light and reflections from the
controlled vehicle's head lamps off of various external objects,
wherein said controller is further configured to generate either an
exterior light control, an undim counter control, a dim counter
control, a sub-combination or combination thereof.
2. An automatic vehicle exterior light control as in claim 1
wherein said controller is further configured to generate an
exterior light control signal as a function of said undim
counter.
3. An automatic vehicle exterior light control as in claim 1
wherein said controller is further configured to generate an
exterior light control signal as a function of said undim
counter.
4. An automatic vehicle exterior light control as in claim 1
wherein said controller is configured to distinguish a stationary
light source from an oncoming head lamp and, or, a leading tail
lamp.
5. An automatic vehicle exterior light control as in claim 1
configured to transfer images at a rate greater than, or equal to,
two hundred forty frames per second between said image array sensor
and said controller.
6. An automatic vehicle exterior light control as in claim 1
wherein at least one image transferred between said image array
sensor and said controller comprises fewer than a total number of
pixels within said image array sensor.
7. An automatic vehicle exterior light control, comprising: an
image array sensor configured to capture at least one frame; and a
controller configured with an undim counter, said controller is
further configured to generate an exterior light control signal as
a function of said undim counter.
8. An automatic vehicle exterior light control as in claim 7
wherein said undim counter provides verification of a particular
light source with said at least one frame.
9. An automatic vehicle exterior light control as in claim 7
wherein said undim counter is configured to increment with each
clear frame.
10. An automatic vehicle exterior light control as in claim 9
wherein said undim counter is compared to a threshold and said
exterior light control signal is an exterior light activation
signal when said undim counter is greater than and, or equal to,
said threshold.
11. An automatic vehicle exterior light control as in claim 7
wherein said undim counter is configured to be set to zero with
each frame containing an oncoming head lamp or leading tail
lamp.
12. An automatic vehicle exterior light control as in claim 7
wherein said controller is further configured to identify an AC
powered light source.
13. An automatic vehicle exterior light control as in claim 7
wherein said controller is further configured to distinguish a
stationary light source from an oncoming head lamp and, or, a
leading tail lamp.
14. An automatic vehicle exterior light control as in claim 7
wherein at least one image transferred between said image array
sensor and said controller comprises fewer than a total number of
pixels within said image array sensor.
15. An automatic vehicle exterior light control, comprising: an
image array sensor configured to capture at least one frame; and a
controller configured with a dim counter, said controller is
further configured to generate an exterior light control signal as
a function of said dim counter.
16. An automatic vehicle exterior light control as in claim 15
wherein said dim counter provides verification of a particular
light source.
17. An automatic vehicle exterior light control as in claim 15
wherein said dim counter is configured to increment with each frame
comprising a head lamp and, or, a tail lamp.
18. An automatic vehicle exterior light control as in claim 17
wherein said dim counter is compared to a threshold and said
exterior light control signal is an exterior light deactivation
signal when said dim counter is greater than and, or equal to, said
threshold.
19. An automatic vehicle exterior light control as in claim 15
wherein said dim counter is configured to be set to zero with each
clear frame.
20. An automatic vehicle exterior light control as in claim 15
wherein said controller is further configured to identify an AC
powered light source.
21. An automatic vehicle exterior light control as in claim 15
wherein said controller is further configured to distinguish a
stationary light source from an oncoming head lamp and, or, a
leading tail lamp.
22. An automatic vehicle exterior light control as in claim 15
wherein at least one image transferred between said image array
sensor and said controller comprises fewer than a total number of
pixels within said image array sensor.
23. An automatic vehicle exterior light control, comprising: a
sensor; and a controller configured to receive a signal from said
sensor, said controller is further configured to identify an AC
powered light source by detecting intensity modulation, wherein
said controller is further configured to generate either an
exterior light control, an undim counter control, a dim counter
control, a sub-combination or combination thereof as a function of
identifying at least one AC powered light source.
24. An automatic vehicle exterior light control as in claim 23
wherein said sensor is an image array sensor, wherein said
controller is configured to analyze a plurality of images acquired
from said image array sensor.
25. An automatic vehicle exterior light control as in claim 24
wherein said controller is configured to identify intensity
modulation.
26. An automatic vehicle exterior light control as in claim 23
wherein said sensor is a photodiode.
27. An automatic vehicle exterior light control as in claim 26
further comprising a low pass filter.
28. An automatic vehicle exterior light control as in claim 27
wherein said controller is further configured to determine the
ratio of modulated light versus unmodulated light in a scene.
29. An automatic vehicle exterior light control as in claim 23
wherein said controller is further configured to distinguish a
stationary light source from an oncoming head lamp and, or, a
leading tail lamp.
30. An automatic vehicle exterior light control, comprising: a
controller configured to distinguish between external sources of
light and reflections from the controlled vehicle's head lamps off
of various external objects by comparing the relative brightness of
imaged objects between two consecutive images where the brightness
of at least one of said head lamps is varied between each image,
wherein said controller is further configured to generate either an
exterior light control, an undim counter control, a dim counter
control, a sub-combination or combination thereof.
31. An automatic vehicle exterior light control as in claim 30
wherein said exterior light control signal is configured to vary
the intensity of at least one variable intensity head lamp.
32. An automatic vehicle exterior light control as in claim 30
wherein said controller is further configured to determine the
ratio of modulated light versus unmodulated light in a scene.
33. An automatic vehicle exterior light control as in claim 30
wherein said controller is further configured to distinguish a
stationary light source from an oncoming head lamp and, or, a
leading tail lamp.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 10/677,453, entitled "CONTROL SYSTEM TO
AUTOMATICALLY CONTROL VEHICLE HEADLAMPS" filed on Oct. 2, 2003, by
Joseph S. Stam et al., which is a continuation of U.S. patent
application Ser. No. 09/874,197, entitled "CONTROL SYSTEM TO
AUTOMATICALLY CONTROL VEHICLE HEADLAMPS" filed on Jun. 5, 2001, by
Joseph S. Stam et al., now U.S. Pat. No. 6,653,614, which is a
continuation of U.S. patent application Ser. No. 09/151,487,
entitled "CONTROL SYSTEM TO AUTOMATICALLY DIM VEHICLE HEADLAMPS"
filed on Sep. 11, 1998, by Joseph S. Stam et al., now U.S. Pat. No.
6,255,639, which is a continuation of U.S. patent application Ser.
No. 08/831,232, entitled "CONTROL SYSTEM TO AUTOMATICALLY DIM
VEHICLE HEADLAMPS" filed on Apr. 2, 1997, by Joseph S. Stam et al.,
now U.S. Pat. No. 5,837,994. Priority under 35 U.S.C. .sctn. 120 is
hereby claimed on all three of the above applications and the
entire disclosures of each are incorporated herein by
reference.
BACKGROUND OF THE INVENTION
[0002] The present invention relates to a system for automatically
dimming vehicle high beam headlamps.
[0003] Regulations set forth by the United States Department of
Transportation (DOT) regulate the light emissions of vehicle high
beam headlamps. Various state regulations are used to control the
amount of glare experienced by drivers of other vehicles whether
the vehicle is traveling in the same direction as the controlled
vehicle or in an opposite direction.
[0004] Known vehicle high beam headlamp emissions in accordance
with the DOT regulations provide an intensity of 40,000 cd at 0
degrees, 10,000 cd at 3 degrees, 3250 cd at 6 degrees, 1500 cd at 9
degrees, and 750 cd at 12 degrees. An example of such an emission
pattern is illustrated in FIG. 1. In order to avoid an illuminance
of 0.5 foot candles (fc) incident on another vehicle, the vehicle
high beam headlamps should be dimmed within 230 feet of another
vehicle at 0 degrees, 115 feet of another vehicle at a horizontal
position of 3 degrees relative to the datum, and 65 feet in the
position of the other vehicle is 6 degrees relative to the
controlled vehicle.
[0005] Various known head light dimmer control systems are known in
the art. In order to prevent the drivers of other vehicles from
being subjected to excessive glare levels, such automatic headlamp
dimmer systems must sense both the head lights as well as the tail
lights of other vehicles. While many known systems are adequately
able to detect headlamps of oncoming vehicles, such systems are
known to inadequately sense tail lights of vehicles traveling ahead
of the control vehicle. As such, such systems are not able to
automatically dim the high beam headlamps in time to prevent
drivers of the vehicles traveling in the same direction as the
controlled vehicle being subjected to excessive glare levels.
[0006] U.S. Pat. No. 5,537,003, assigned to the same assignee of
the present invention, discloses an automatic headlamp dimming
system which includes an optical system for sensing tail lamps as
well as headlamps. The '003 patent discloses a single photo diode
with a mechanical scanning arrangement for scanning a predetermined
field of view. Although the system provides relatively suitable
sensing of headlamps as well as tail lamps, the optical subsystem
is rather complicated and expensive to manufacture.
SUMMARY OF THE INVENTION
[0007] It is an object of the present invention to solve various
problems in the prior art.
[0008] It is yet another object of the present invention to provide
a vehicle headlamp dimming system which eliminates the need for
mechanical optical scanning systems.
[0009] It is yet another object of the present invention to provide
a headlamp dimming system that is adapted to dim the high beam head
lights at different distances as a function of the horizontal
angular position of another vehicle relative to the controlled
vehicle.
[0010] Briefly, the present invention relates to an automatic
vehicle headlamp dimming system. The system includes an optical
system and an imaging processing system. The optical system is
configured to discriminate between headlamps and tail lamps and
focus the light rays from the headlamps and tail lamps on different
portions of a pixel sensor array. The optical system, as well as
the image processing system, provides for relatively increased
discrimination of headlamps and tail lamps of other vehicles and
also enables the high beam headlamps of the control vehicle to be
controlled as a function of the distance as well as the horizontal
angular position of other vehicles relative to the controlled
vehicle.
[0011] 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
[0012] These and other objects of the present invention will be
readily understood with reference to the following specification
and attached drawing, wherein:
[0013] FIG. 1 is a top view illustrating the headlamp emission
pattern of a conventional high beam headlamp.
[0014] FIG. 2 is a side cross-sectional view of the optical system,
which forms a part of the present invention illustrating light rays
incident at a vertical angle within the desired field of view.
[0015] FIG. 3 is similar to FIG. 2 illustrating the light rays
incident at a vertical elevation angle beyond the desired field of
view.
[0016] FIG. 4 is a top cross sectional view of the optical system
illustrated in FIG. 1 illustrating the light rays at a horizontal
angle within the desired field of view.
[0017] FIG. 5 is a block diagram of the automatic head light
dimming system in accordance with the present invention.
[0018] FIG. 6 is an overall flow diagram of the image processing in
accordance with the present invention.
[0019] FIG. 7 is a flow diagram illustrating the method for
detecting tail lamps of vehicles within the desired field of
view.
[0020] FIG. 8 is a flow diagram for detecting headlamps from other
vehicles within the desired field of view.
DETAILED DESCRIPTION OF THE INVENTION
[0021] The automatic headlamp dimming system in accordance with the
present invention includes an optical system as illustrated in
FIGS. 2-4 and an image processing system as illustrated in FIGS.
5-8. In order to enable the high beam headlamps to remain on for
the longest reasonable time without subjecting the driver of
another vehicle to excessive glare, the automatic headlamp dimming
system in accordance with the present invention controls the
vehicle high beam headlamps as a function of the distance as well
as the horizontal angular position of the other vehicle relative to
the controlled vehicle. As will be discussed in more detail below,
the optical system is adapted to discriminate between headlamps and
tail lamps of other vehicles. The light rays from the headlamps and
tail lamps of other vehicles are spatially segregated on a pixel
sensor array to provide increased discrimination of headlamps and
tail lamps relative to other ambient light sources, such as road
signs and reflections from snow and the like. The optical system
enables both the horizontal and vertical position of incident
lights sources to be determined within the field of view of the
optical system. The image processing system processes the pixels to
provide for automatic control of the headlamps as a function of the
distance and horizontal angular position of another vehicle
relative to the control vehicle. As such, the system in accordance
with the present invention is adapted to provide optimal control of
the vehicle high beam headlamps by allowing the high beam headlamps
to remain on for as long as possible while preventing the driver of
the other vehicle from being subjected to an undue amount of
glare.
[0022] Optical System
[0023] Referring to FIGS. 2-4, the optical system includes a pair
of lenses 103 and 104, a lens holder 105, and an image array sensor
106. As best shown in FIGS. 2 and 3, the lenses 103 and 104 are
vertically spaced apart in order to allow imaging of substantially
the same field of view onto different portions of the same array.
The lenses 103, 104 image generally the same fields of view because
the distance between the lenses 103, 104 is relatively small
relative to the light sources within the field of view of the
device.
[0024] The lens 103 may be formed with a red filter dye for
transmitting light with wavelengths greater than 600 nm and
focusing red light rays 101 from tail lamps onto one-half of the
image array sensor 106. The red filter dye causes the lens 103 to
absorb all light rays at the blue end of the visible spectrum and
transmit light rays at the red end of the spectrum. As such, the
amount of light transmitted from non-red light sources, such as
headlamps, is greatly reduced while light rays from tail lamps are
fully transmitted through the lens 103. As such, the relative
brightness of the light rays from tail lamps imaged onto the image
array sensor 106 is greatly increased.
[0025] The lens 104 may be formed with a cyan-filtered dye for
transmitting light with wavelengths less than 600 nm. The lens 104
is used to focus the light rays onto the other half of the image
array sensor 106. The cyan filter dye has a complementary effect to
the red filter described above. In particular, the red filter dye
absorbs light from the blue end of the visible spectrum while
transmitting light from the red end of the spectrum. As such, most
of the light from sources, such as head lights, is transmitted
through the lens 104 while virtually all of the light emanating
from tail lamps is blocked.
[0026] Both headlamps and tail lamps emit a substantial amount of
infrared light. By utilizing lenses with a filter dye or separate
filters which inhibit light at wavelengths greater about 750 nm,
the infrared light transmitted by the headlamps and tail lamps will
be substantially blocked by the lenses 103 and 104. By eliminating
infrared light, the ratio between intensity between red lights
imaged through the red filter and red light imaged through the cyan
filter will be substantially increased.
[0027] The use of the red and cyan dyes for the lenses 103 and 104
is merely exemplary. The filter characteristics of the lenses 103
and 104 are selected to optimize the sensitivity of the device to
specific light sources. For example, the headlamps or tail lamps in
new vehicles may be replaced with alternative light sources with
different spectral composition, for example, with high intensity
discharge headlamps and light emitting diode tail lamps requiring
different filter characteristics. Depending on the spectral
characteristics of the headlamps and tail lamps, transparent lenses
103 and 104 may be utilized with separate color filters.
[0028] The lenses 103 and 104 may be formed as acrylic spherical
lenses. Alternatively, the lenses 103 and 104 may be formed as
aspherical lenses in order to minimize color dispersion and
spherical aberration present with spherical lenses. Complex lenses
formed from both spherical and aspherical lenses are also
contemplated.
[0029] A single lens may also be used in place of the separate
lenses 103 and 104. The use of a single lens may be used to image
the field of view onto a full or partial color image array sensor
containing pigmentation on the individual pixels in the array.
[0030] As shown best in FIGS. 2 and 3, the horizontal distance
between the two lenses 103 and 104 and the image array sensor 106
is slightly different. Offsetting of the two lenses 103 and 104
compensates for the color dispersion created as a result of the
fact that the index of refraction of materials varies with the
wavelength of light transmitted through it. Because the two lenses
103 and 104 transmit different portions of the visible spectrum,
the distance between the lenses 103 and 104 and the image array
sensor 106 is optimized to minimize the dispersion for the band of
light transmitted by each of the lenses 103 and 104.
[0031] As mentioned above, the light rays 101 transmitted through
the lens 103 are imaged onto one-half of the image array sensor 106
while the light rays 102 transmitted through the lens 104 are
imaged onto the other half of the image array sensor 106. In order
to provide such spatial segregation of the light rays transmitted
through the lenses 103 and 104, the lens holder 105 is provided
with cutouts 107 and preferably formed or coated with a light
absorbing material. These cutouts 107 prevent light rays beyond the
desired maximum vertical angle transmitted through the red lens 103
from being imaged onto the portion of the image array sensor 106
reserved for the light rays 102. Conversely, the cutouts 107 also
prevent light rays transmitted through the lens 104 from being
imaged onto the portion of the image array sensor 106 reserved for
the light rays 101.
[0032] The field of view of the optical system is defined by the
configuration of the lenses 103 and 104 and the cutouts 107
relative to the image array sensor 106. For example, an exemplary
field of view of 10 degrees in the vertical direction and 20
degrees in the horizontal directions may be created by the
configuration set forth below. In particular, for such a field of
view, the lenses 103 and 104 are selected with a diameter of 1.5 mm
with a small portion cut away to allow the lenses 103, 104 to be
positioned such that their centers are separated by 1.0 mm. The
lens 103 is positioned 4.15 mm from the image array sensor 106
while the lens 104 is positioned 4.05 mm away. Both the front and
rear surface radii of the lenses 103 and 104 are 4.3 millimeters
with a 0.2 millimeter thickness.
[0033] As best shown in FIGS. 3 and 4, circular cutouts 108 are
formed in the lens holder 105. A pair of generally rectangular
apertures 110 is formed in a rear wall 112. The rear apertures 110
are 1.6 millimeters in the horizontal direction and 0.8 millimeters
in the vertical direction. As best shown in FIG. 4, the cutouts 107
taper from the rear apertures 110 to the diameter of the front
cutouts 108 to provide the field of view discussed above.
[0034] The configuration described above is thus able to baffle
light outside of the desired horizontal and vertical field of view.
In particular, FIG. 3 illustrates how the system baffles light rays
incident at angles beyond the vertical field of view. FIG. 4
illustrates light rays being imaged onto the image array sensor 106
within the horizontal field of view.
[0035] The image array sensor 106 may be CMOS active pixel image
sensor array, for example, as disclosed in U.S. Pat. No. 5,471,515,
hereby incorporated by reference and available from Photobit LLC of
La Crasenta, Calif. CMOS active pixel image sensors provide
relatively high sensitivity and low power consumption as well as
the ability to integrate other CMOS electronics on the same chip.
The image array sensor 106 may be a 50.times.50 40 .mu.m pixel
array. The number of pixels in the image array sensor 106 is
selected such that not all pixels fall within the area that the
lenses 103 and 104 project onto. The extra pixels allow for simple
correction for mechanical misalignment by offsetting the expected
image location.
[0036] The image array sensor 106 provides spatial information
regarding light sources within the field of view. The number of
pixels present in the array is selected to obtain sufficient
spatial detail although the size of the array is not limited and
may be selected, and may even be dictated by physical and economic
limitations.
[0037] The image array sensor 106 must be sensitive to accurately
detect tail lights at several hundred feet. Such sensitivity may be
achieved by lengthening the amount of time the photosites in the
array are exposed to light during a frame period. A frame period is
selected to enable the array to capture and transfer a frame to the
image processing system in a short enough time to allow the image
processing system to detect another vehicle entering the field of
view. A short time period also limits the amount of motion within a
frame during the integration period and thus produces a relatively
more accurate instantaneous image.
[0038] The use of a pixel array also provides other benefits. For
example, as mentioned above, the light integration time to capture
a frame can be varied. Such a feature allows the system to provide
optimal results in varying degrees in darkness. Another important
aspect of an image array sensor is the ability to utilize subsets
of the pixels within the array or an individual pixel.
[0039] As such, as the window size is decreased, the readout rates
can be increased. Such a feature allows the system to discriminate
ambient light sources, such as street lamps. In particular, such a
feature allows the system to locate a light source within the frame
and capture several samples of the light sources at a rate several
times greater than 60 Hz. In particular, if the samples exhibit 120
Hz intensity modulation, the light source is likely a street lamp
or other light source powered from a 60 Hz AC power supply. If the
light source is not modulated, the light source is likely powered
by the vehicle's DC power supply.
[0040] Another potential benefit of the image array sensor is that
it allows the field of view immediately in front of the vehicle to
be imaged by a higher pixel resolution. Thus, the system may be
configured such that the effective pixel resolution decreases as
the angle of the vehicle relative to the control vehicle increases
thus reducing the amount of processing time in those areas. Such a
configuration reduces the sensitivity of the device to light
sources from reflective stationary objects on the side of the
road.
[0041] An image array sensor could be manufactured in which the
pixel pitch is varied as a function of the area in the field of
view that the pixel images. For example, pixels imaging the space
corresponding to horizontal angles within 3 degrees of the center
of the vehicle may be provided with a 10 .mu.m pixel pitch. Pixels
imaging horizontal angles between 3 and 6 degrees may be provided
with a 20 .mu.m pixel pitch, while those imaging angles greater
than 60 degrees may be provided with a 40 .mu.m pitch. While such a
configuration may not increase the sensing area, the ability to
resolve detail increases; an important aspect in considering the
relative size of a tail lamp at a relatively large distance. For
example, a 41/2 inch diameter tail light at a distance of 200 feet
subtends an angle of less than 0.11 degrees. If a 50.times.50 image
array sensor is used to image a 20 degree field of view, the tail
lamp would subtend approximately 8% of the total area imaged by the
pixel.
[0042] A tail lamp is relatively brighter than its ambient
surroundings; however, the red light contributed by the tail light
is diluted by the ambient light at such a distance. Such a factor
is critical when comparing the amount of red light in a given area
to the amount of non-red light in the same area. When the area of
space compared is large relative to the light source, the
percentage of red light is diminished. By comparison, if 10 .mu.m
pixels are used in the center of the array 106 instead of 40 .mu.m
pixels, the tail lamp would subtend 0.04% of the total areas, an
improvement of 16 times.
Image Processing System
[0043] The image processing system is illustrated in FIGS. 5-8. The
image processing system includes the image array sensor 106; a
microprocessor 204, for example, a Motorola type MC68HC08XL36; a
headlamp control unit 205; and a pair of headlamps 206. As
mentioned above, an active pixel array sensor may be utilized for
the image array sensor 106. Such an active pixel array sensor
includes an image array 201 and an analog to digital converter
(ADC) 202. A timing and control circuit is used to control the
image array 201 as well as the ADC 202 to control the integration
time, read out timing, pixel selection, gain offset and other
variables. The microprocessor 204 is used to analyze the data
collected by the image array sensor 201. The microprocessor 204 is
in communication with the headlamp control unit, a conventional
unit, implemented, for example, as a relay, which, in turn,
controls the headlamps 206. The headlamp control unit 205, in turn,
changes the voltage applied to the headlamp 206 to cause the high
beam or bright lamp to be switched on or off.
[0044] The flow chart for the headlamp control is illustrated in
FIG. 6. The system runs in a continuous cycle with occasional
interrupts for absolute light measurements, adjustments of ADC
parameters, or other functions.
[0045] At the beginning of each cycle, two images are acquired
through the lenses 103 and 104. In step 302, the images from the
lenses 103 and 104 are analyzed to detect tail lamps. Another image
is acquired in step 303 through the lens 104. The image acquired
through the lens 104 is acquired with a low enough gain to detect
oncoming head lights while rejecting lower light level reflections
and nuisance light sources. After the images are analyzed, the
system checks for very bright lights in the image indicating the
sudden appearance of vehicle headlamps or tail lamps within the
field of view, as is the case when a car turns in front of the
controlled vehicle in step 305. If bright lights are sensed, the
device dims the headlamps 206 immediately and bypasses the time
verification as discussed below. The cycle is then repeated. If
there were no bright lights, the system proceeds to step 307 to
determine if there are any headlamps or tail lamps in the
image.
[0046] In order to confirm the presence or lack of presence of a
headlamp or tail lamp in a frame, an undim counter and a dim
counter are used. These counters provide verification of a
particular light source whether from a tail lamp or headlamp from
consecutive frames before signaling the headlamp control unit 205
to dim or undim the headlamps 206, except as described above, when
a bright light is detected. By providing verification, anomalies
within the device or in the image will not cause spurious operation
of the headlamps 206.
[0047] The dim counter is incremented each time a frame with a
headlamp or tail lamp is detected until the number of required
consecutive frames to take action are reached. The dim counter is
set to 0 each time a clear frame is processed. The undim counter is
incremented with each clear frame and set to 0 with each frame
containing a headlamp or tail lamp. The actual number of
consecutive frames required to dim or undim is determined by the
overall speed of the device. The more frames used for verification,
the less susceptible the system will be to noise and anomalies.
However, the device must be able to react quickly to be effective
so the number of verification frames is kept relatively low.
Whenever a headlamp or tail lamp is detected in step 307, the undim
counter is set to 0 in step 308. In step 309, the system checks
whether the headlamp 206 high beams are on. If the high beams are
off, no further action is required and the cycle is repeated as
indicated by step 317. If the high beams are on, the dim counter is
incremented in step 310. After the dim counter is incremented in
step 310, the system checks in step 311 if the dim counter has
reached the number of consecutive frames required to dim the
headlamps 206. If so, the system proceeds to step 306 and dims the
headlamps 206 and resets both the dim and undim counters and
repeats the cycle. Otherwise, the system repeats the cycle and
proceeds to step to 317.
[0048] In step 307, if there are no headlamps or tail lamps in the
image, the dim counter is set to 0 in step 312. Subsequently, in
step 313, the system determines whether the high beams 206 are on.
If the high beams are on, the system exits repeats the cycle in
step 317. In step 313 if the brights are not on, the undim counter
is incremented. After the undim counter is incremented, the system
checks in step 315 whether the undim counter has reached the number
of consecutive clear frames required to activate the high beams
206. If so, the high beams are turned on in step 316, and the cycle
is repeated. If the undim counter is less than the required number
for activating the bright headlamps 206, the system repeats the
cycle in step 317.
[0049] The flow diagram for tail light processing is illustrated in
FIG. 7. As will be discussed in more detail below, the primary
method of identifying an object such as a tail light involves
comparing the gray scale value of a pixel through the lens 103 to a
gray scale value of the pixel representing the same space imaged
through the lens, 104. If the value of the pixel imaged through the
lens 103 is significantly higher than the value of the pixel imaged
through the lens 104, the light source is determined to be red
light. In addition to determining if the light is red, the system
also checks the brightness of the red light before deciding that
the light is a tail lamp by determining if the gray scale value of
the pixel is greater than a threshold value. As is known in the
art, the brightness of a light source varies with the square of the
distance of the light source from the observer. As such, an
approximate determination of the distance of a leading vehicle can
be made to determine the appropriate time to dim the headlamps.
[0050] The threshold value may be computed in a variety of ways.
For example, it can be a predetermined fixed number or a number
that is a function of the current image sensor and ADC settings.
The threshold value can also be determined by computing a threshold
as a factor of the average pixel intensity of the entire image
which would help eliminate variances caused by changing ambient
light sources. In addition, the pixel value may be compared to the
average of the pixels in the immediate area of the pixel of
interest. This local average method prevents relatively large,
moderately bright spots in the image from being seen as vehicle
light sources. More particularly, distant tail lamps subtend less
than one pixel and thus will only have moderate brightness. Large
spots in the image with moderate brightness are most likely caused
by reflections from large objects. Close tail lamps which subtend
many pixels will have a saturated center which will be brighter
than the surrounding pixels allowing the same method to detect them
as well.
[0051] The threshold may also be determined by varying the
threshold spatially by way of a lookup table or computation.
However, the threshold should be determined so that dimming occurs
appropriately for the dimmest tail lights allowed by the DOT
standards. Distant vehicles are subjected to the most intense
portion of the controlled vehicle high beam, thus requiring dimming
only directly in front of the controlled vehicle as indicated in
FIG. 1. Thus, a relatively low threshold may be selected for light
sources imaged directly in front of the control vehicle while a
higher threshold for light sources that are not directly in front
of the control vehicle. For example, as discussed in connection
with FIG. 1, the threshold for pixels imaging the field of view 3
degrees right and left of the center should correspond to a light
level incident on the image array sensor 106 about 4 times as
bright as the threshold for red light directly in front of the
vehicle and 12 times as bright for vehicles at 6 degrees. Such a
spatially varying threshold helps eliminate false tail lamp
detection caused by red reflectors by making the system less
sensitive to areas of the sides of the control vehicle.
[0052] A similar approach can be taken for varying the threshold
for pixels in imaging areas of space and angles above and below the
center. However, a more conservative approach can be taken when
determining the tail light sensitivity relative to the vertical
angle since vehicles tend to move more frequently and rapidly in
vertical directions due to hills and bumps in the road. Therefore,
by specifying relatively tight vertical thresholds may cause the
bright headlamps 206 to switch on and off as the vehicle moves
several degrees up and down.
[0053] A hysteresis multiplier may be applied to the threshold to
prevent oscillations of the headlamps 206 when the light source has
a gray scale value at or near the threshold. Thus, if the bright
headlamps 206 are off, the threshold will be lower for all pixels
to prevent the bright headlamps from coming back on, even if the
faintest tail lamps are present in the image. However, if the
bright headlamps 206 are on, the threshold should be higher so that
only tail lamps of sufficient brightness are sensed to indicate
that the car is within the dimming range to cause the headlamps 206
to dim.
[0054] One of the biggest problems facing the detection of the tail
lamps is the nuisance red light reflected from corner cube
reflectors commonly found as markers on the side of the road and on
mailboxes. The variable threshold method mentioned above helps
eliminate some of this noise. However, when a vehicle approaches a
reflector at the proper angles, it is relatively impossible to
distinguish a red reflector from a tail lamp. Fortunately, by
examining successive frames and investigating the motion of these
objects over time, such reflections can be filtered. By storing the
location of the tail lamps and images over time or by sensing small
regions of interest where the tail lamp is located several
consecutive times, the device can look for rightward motion and
determine if the light source is a reflector. Additionally, the
speed at which the control vehicle overtakes a stationary object is
much greater than the relative rate a vehicle would overtake
another moving vehicle. Thus, the rate of increase in brightness of
the object would be typically much greater for a stationary
reflector than for another vehicle. This rate of change in
brightness coupled with rightward horizontal motion can be used as
signatures to reduce the number of false tail lamps detected.
[0055] A computationally simpler method of analyzing spatial motion
of a light source is to simply take several consecutive regions of
the local region of interest where the light source is located.
Motion in the vertical and horizontal directions is relatively slow
for tail lamps of a leading vehicle. Simply sampling a pixel a few
consecutive times to see if the tail lamp is present in all samples
can adequately eliminate objects which rapidly move within the
image.
[0056] The flow diagram for tail lamp processing is illustrated in
FIG. 7. Initially, in step 318, the system ascertains if the pixel
is within the tail lamp window. In particular, as mentioned above,
red lights are imaged onto half of the image array sensor 106.
Thus, if the pixel is not within the appropriate half of the image
array sensor 106, the system proceeds to step 319 and moves to
another pixel. As mentioned above, there are two criteria for
ascertaining whether the image is a tail lamp. The first criteria
relates to comparing the gray scale value of the pixel image
through the lens 103 with a corresponding gray scale value for the
same area in space imaged through the lens 104. If the gray scale
value of the pixel imaged through the lens 103 is significantly
larger than the gray scale value of the corresponding pixel imaged
through the lens 104, one of the criteria for detecting a tail lamp
is met. Thus, if the pixel of interest is within the tail lamp
window as ascertained in step 318, the gray scale value of the
pixel imaged through the lens 103 is compared with the gray scale
value of a corresponding pixel imaged through the lens 104 in step
320. If the gray scale value of the pixel image through the lens
103 is not n % greater than the corresponding pixel imaged by the
lens 104, the system proceeds to step 319 and examines another
pixel. Otherwise, the system proceeds to step 321 and calculates
the threshold for the particular pixel based on the region of space
it images. For example, as discussed above, the pixel thresholds
may be varied based on their spatial relationship within the image
array sensor.
[0057] As discussed above, the other criteria for tail lamp
detection relates to the relative brightness of the pixel relative
to neighboring pixels. Thus, in step 322, the system calculates the
average gray scale value of neighboring pixels. If it is determined
in step 323 that the pixel gray scale value for the pixel imaged
through the lens 103 is n % greater than the average gray scale
value of the neighboring pixels, the system proceeds to step 324
and adds the pixel to the tail lamp list for future frames of
reference. Otherwise, the system moves to step 319 and moves the
next pixel. In steps 325 and 326, the systems determines whether or
not the red light detected is a tail lamp or a reflector, as
discussed above. If it is determined that the light is a reflector,
the system proceeds to step 327 and moves on to the next pixel.
Otherwise, the headlamps are dimmed in step 328.
[0058] The flow diagram for head light processing is illustrated in
FIG. 8. Headlamp detection is similar to tail lamp detection. The
primary difference is that only the lens 104 is utilized. As
mentioned above, the pixel integration time is shorter and the ADC
parameters are such that the image only shows very bright objects,
such as headlamps. Most reflections have low intensity light
sources which fall well below the zero threshold of the ADC. As
such, pixels are compared to the local average intensity of the
neighboring pixels. Spatial variances in the thresholds may be set
so that pixels corresponding to the center of the field of view are
more sensitive and pixels to the left of the image (left hand drive
countries) have higher thresholds. These thresholds, however,
should not vary spatially to the same degree as the threshold for
the tail lamps because of the relatively wide variance in the
emission patterns observed from headlamps. In addition, due to the
relatively higher potential for more glare to the driver of an
oncoming car, the headlamps may be controlled and dimmed relatively
more rapidly than in the case when a tail lamp from a vehicle
traveling in the same direction is detected. Similar to the tail
lamp processing circuit hysteresis may be added to prevent cycling
of the headlamps.
[0059] An additional concern with headlamp detection arises from
the rapid decrease in distance between oncoming vehicles which
becomes especially critical when an oncoming vehicle suddenly
enters the controlled vehicle's field of view, for example, when
turning a corner or in a similar situation. For this reason, an
additional flag is used to cause the vehicle to immediately dim the
bright headlamps and bypass any verification if the light source is
above certain absolute high-level brightness thresholds.
[0060] The primary nuisance light source complicating headlamp
detection comes from overhead lights, such as street lights and
electrically illuminated street signs. One method of eliminating
such nuisance light sources is to analyze their motion. In
particular, all overhead street lamps will move vertically upwards
in the image as the controlled vehicle is moving. Analyzing this
motion provides an efficient method of detecting some street lamps.
Unfortunately, distant street lamps appear to be at almost the same
elevational angles as distant head lights and the rate of vertical
climb in the image does not become great until the street lamp is
closer. However, as discussed above, street lighting is AC
controlled and thus is subject to 120 Hz intensity modulation.
Headlamps powered by DC source do not exhibit this characteristic.
Thus, the image array sensor 106 is able to utilize a small number
of pixels for taking several rapid consecutive readings in a
window. If the window is small enough, the window can read several
hundred frames per second. Once the light source is identified in
the image, several frames are read out at a rate of 240 Hz or
higher. These readings are then analyzed to detect the intensity
modulation. If modulation is present, the light source originates
from an AC source and can be ignored. Alternatively, a photodiode
can be used in conjunction with a low pass filter to determine the
ratio of light in the image that was AC modulated to the
unmodulated light. If a significant portion of the light source is
AC modulated, the light source present in the image is assumed to
be from AC light. Otherwise, the light source is assumed to be from
a DC source.
[0061] The flow diagram for headlamp processing is illustrated in
FIG. 8. Initially, the system determines in step 329 whether the
pixel is in the headlamp window (i.e., in that portion of the image
array sensor 106 reserved for light arrays imaged through the lens
104). If not, the system proceeds to step 330 and examines the next
pixel. Otherwise, the system examines the pixel in step 331 to
determine if the pixel is modulated at 120 Hz as discussed above.
If so, the light source is assumed to be a street lamp and thus,
the system proceeds to the next pixel in step 330. If the pixel is
not subject to 120 Hz intensity modulation, the system then
computes the average gray scale of neighboring pixels in step 332.
In step 333, the system determines the threshold for the particular
pixel based on the area of the space it images. The system next
compares the gray scale value of the pixel with an absolute high
level threshold in step 334, for example, to determine if any
oncoming cars suddenly come into the field of view of the
controlled vehicle. If so, the system proceeds to step 335 and sets
a flag to cause immediate dimming. Otherwise, the system proceeds
to step 336 and determines if the gray scale value of the pixel is
n % greater than the average of neighboring pixels. If not, the
system returns to step 330 and examines the next pixel. Otherwise,
the system proceeds to step 337 and adds the pixel to the headlamp
list for future frames to reference.
[0062] As discussed above, the system examines light sources as
discussed above in steps 338 and 339 to determine if the light
source is a street lamp. If the system determines that the light
source is not a street lamp, the system proceeds to step 340 and
sets a flag to cause dimming of the headlamps 206. If the system
determines that the light source is a street lamp, the system
proceeds to step 341 and moves on to the next pixel.
[0063] Traditional vehicle lamps systems have the option of the
bright lamps being either on or off. The present invention is
readily adaptable for use with a headlamp system where the brights
can be activated to vary the brightness based on the distance of
other vehicles in the field of view. In such an embodiment, the
brightness of the headlamps may be varied by various techniques
including modulating the duty cycle of the headlamp in order to
reduce or increase the overall brightness level.
[0064] Variable intensity headlamps also result in better noise
filtration. In particular, whenever a light source is detected
which causes the brightness of the controlled headlamps of the
vehicles to be decreased, other images can be detected to determine
if the intensity of these other light sources decreases by a
similar amount. If so, the system would be able to determine that
the light source is a reflection from the vehicle's headlamps. Such
information can be used as feedback to provide a relatively
efficient means for eliminating nuisance light caused by
reflections of the control vehicle headlamps. In such an
embodiment, the brightness threshold discussed above would not be
used. More particularly, the brightness of the brightest headlamp
and tail lamp in the images is used to determine the brightness of
the controlled vehicle's headlamps. The brighter the headlamps or
tail lamp in the images, the dimmer the controlled headlamps.
[0065] Obviously, many modifications and variations of the present
invention are possible in light of the above teachings. Thus, it is
to be understood that, within the scope of the appended claims, the
invention may be practiced otherwise than as specifically described
above.
[0066] The above description is considered that of the preferred
embodiments only. Modifications 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.
* * * * *