U.S. patent application number 12/951275 was filed with the patent office on 2012-05-24 for method for reducing glare from light sources through windscreens.
This patent application is currently assigned to GM GLOBAL TECHNOLOGY OPERATIONS, INC.. Invention is credited to Rohit Gupta, Chandra S. Namuduri, Asim Tewari.
Application Number | 20120126099 12/951275 |
Document ID | / |
Family ID | 46021560 |
Filed Date | 2012-05-24 |
United States Patent
Application |
20120126099 |
Kind Code |
A1 |
Tewari; Asim ; et
al. |
May 24, 2012 |
METHOD FOR REDUCING GLARE FROM LIGHT SOURCES THROUGH
WINDSCREENS
Abstract
A method of reducing glare may include sensing a first light
source with a second vehicle, and sensing a second light source
with a first vehicle and oscillating a first light source ICF
between a substantially opaque state and a substantially clear
state on a first schedule. A second windscreen ICF may be
oscillating between the substantially opaque state and the
substantially clear state on a second schedule different from the
first schedule. A position of the light source may be sensed and an
eye position of the occupant estimated. An intersecting region of
the selectively-darkenable ICF, which is located substantially
along a line from the position of the light source to the eye
position, is calculated. The intersecting region of the ICF is
darkened, such that a reduced amount of light from the light source
passes through the intersecting region.
Inventors: |
Tewari; Asim; (Bangalore,
IN) ; Gupta; Rohit; (Bangalore, IN) ;
Namuduri; Chandra S.; (Troy, MI) |
Assignee: |
GM GLOBAL TECHNOLOGY OPERATIONS,
INC.
Detroit
MI
|
Family ID: |
46021560 |
Appl. No.: |
12/951275 |
Filed: |
November 22, 2010 |
Current U.S.
Class: |
250/214D ;
250/214AL |
Current CPC
Class: |
B60R 1/00 20130101; B60J
3/00 20130101; G02B 26/02 20130101; B60J 3/02 20130101; Y02T 10/88
20130101; B60J 3/04 20130101 |
Class at
Publication: |
250/214.D ;
250/214.AL |
International
Class: |
G01J 1/44 20060101
G01J001/44; B60J 3/04 20060101 B60J003/04 |
Claims
1. A method for reducing glare through a windscreen from a light
source to an occupant's eye, wherein the windscreen is covered with
a selectively-darkenable intensity control film (ICF), the method
comprising: sensing a position of the light source; estimating an
eye position of the occupant; calculating an intersecting region of
the selectively-darkenable ICF, wherein the intersecting region is
located substantially along a line from the position of the light
source to the estimated eye position; and darkening the
intersecting region, such that a reduced amount of light from the
light source passes through the intersecting region.
2. The method of claim 1, further comprising: sensing the eye
position of the occupant; and wherein the intersecting region of
the windscreen is calculated based upon the sensed eye position
instead of the estimated eye position.
3. The method of claim 2, wherein the selectively-darkenable ICF
further includes a matrix of selectively-darkenable ICF cells;
determining which of the ICF cells has a center nearest to the
intersecting region; and wherein darkening the intersecting region
includes darkening the ICF cell determined to be nearest to the
intersecting region.
4. The method of claim 2, wherein darkening the intersecting region
includes darkening a plurality of the ICF cells encompassing the
intersecting region.
5. The method of claim 4, wherein the light source is moving
relative to the windscreen, and further comprising: sensing a new
position of the light source; calculating a new intersecting region
of the selectively-darkenable ICF, wherein the new intersecting
region is located substantially along a line from the new position
of the light source to the sensed eye position; and darkening the
new intersecting region by darkening a plurality of the ICF cells
encompassing the new intersecting region, such that a reduced
amount of light from the light source passes through the new
intersecting region.
6. A method for reducing glare between a first vehicle and a second
vehicle, wherein the first vehicle has a first light source with a
first light source intensity control film (ICF) and a first
windscreen with a first windscreen ICF, and the second vehicle has
a second light source with a second light source ICF and a second
windscreen with a second windscreen ICF, the method comprising:
sensing the first light source with the second vehicle, and sensing
the second light source with the first vehicle; oscillating the
first light source ICF between a substantially opaque state and a
substantially clear state on a first schedule; and oscillating the
second windscreen ICF between the substantially opaque state and
the substantially clear state on a second schedule different from
the first schedule.
7. The method of claim 6, wherein the second schedule is one
hundred eighty degrees out of phase from the first schedule, such
that the first light source ICF is in the substantially opaque
state while the second windscreen ICF is in the substantially clear
state.
8. The method of claim 7, further comprising: oscillating the first
windscreen ICF between the substantially opaque state and the
substantially clear state on the first schedule; and oscillating
the second light source ICF on the second schedule, such that the
first windscreen ICF is in the substantially opaque state while the
second light source ICF is in the substantially clear state.
9. The method of claim 8, further comprising: sensing magnetic
north; determining a first offset angle for the first vehicle
relative to magnetic north; determining a second offset angle for
the second vehicle relative to magnetic north; calculating the
first schedule as a function of the first offset angle; and
calculating the second schedule as a function of the second offset
angle.
10. The method of claim 9, further comprising: monitoring a common
clock cycle; wherein calculating the first schedule includes phase
lagging the first offset angle from the common clock cycle; and
wherein calculating the second schedule includes phase lagging the
second offset angle from the common clock cycle.
11. The method of claim 6, wherein the first schedule has a first
frequency and the second schedule has a second frequency different
from the first frequency; and wherein the second frequency is
between one to thirty percent different from the first frequency.
Description
TECHNICAL FIELD
[0001] This disclosure relates to reducing glare between light
sources and vehicles or vehicle occupants using intensity control
films.
BACKGROUND
[0002] Many vehicles include one or more headlamps (also referred
to as headlights) usually attached to the front of the vehicle.
Headlamps usually have the purpose of illuminating the road ahead
during periods of low visibility, such as darkness or
precipitation, but also serve to alert or signal the location of
the vehicle to other vehicles and pedestrians.
[0003] When two or more vehicles approach each other, their
respective headlamps may cause glare to the driver of the opposing
vehicle. Depending upon the brightness of the headlamps, the glare
may reduce visibility for one or both of the drivers, especially at
night. Headlamps are often configured to operate with more than one
level of brightness or intensity, often referred to as low beams
and high beams. Operation of the vehicle with high beams may
increase glare to the driver of the oncoming vehicle.
[0004] Other sources of light may also cause glare to the driver of
the vehicle. For example, and without limitation, road-side signage
may incorporate bright lights projecting onto the roadway, spot
lights may be used for numerous purposes on or near roadways, or
the sun may be positioned in the view of drivers--especially during
early morning or late afternoon driving.
SUMMARY
[0005] A method for reducing glare is provided. The glare may occur
between a first vehicle and a second vehicle or between a light
source and an occupant's eye. The first vehicle has a first light
source with a first light source intensity control film (ICF) and a
first windscreen with a first windscreen ICF, and the second
vehicle has a second light source with a second light source ICF
and a second windscreen with a second windscreen ICF. Each
respective ICF is selectively changeable between a substantially
opaque state and a substantially clear state.
[0006] The method may include: sensing the first light source with
the second vehicle, and sensing the second light source with the
first vehicle; oscillating the first light source ICF between the
substantially opaque state and the substantially clear state on a
first schedule; and oscillating the second windscreen ICF between
the substantially opaque state and the substantially clear state on
a second schedule different from the first schedule.
[0007] The method may also include sensing a position of the light
source and estimating an eye position of the occupant. An
intersecting region of the selectively-darkenable ICF is
calculated. The intersecting region being located substantially
along a line from the position of the light source to the estimated
eye position. The intersecting region of the ICF is then darkened,
such that a reduced amount of light from the light source passes
through the intersecting region. Instead of estimating the eye
position of the occupant, the method may include sensing the eye
position of the occupant, and calculating the intersecting region
of the windscreen based upon the sensed eye position.
[0008] The above features and advantages, and other features and
advantages, of the present invention are readily apparent from the
following detailed description of some of the best modes and other
embodiments for carrying out the invention, as defined in the
appended claims, when taken in connection with the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1 is a schematic diagram of anti-glare systems for two
vehicles;
[0010] FIG. 2 is a schematic flow chart of an algorithm or method
for reducing glare from light sources;
[0011] FIG. 3 is a schematic flow chart of a subroutine of the
method shown in FIG. 2;
[0012] FIG. 4 is a schematic flow chart of another subroutine of
the method shown in FIG. 2;
[0013] FIG. 5 is a schematic front view of one of the windscreens
shown in FIG. 1, shown with a matrix of selectively-darkenable
intensity control film (ICF) cells;
[0014] FIG. 6 is a schematic diagram showing the directions of
travel of two vehicles relative to magnetic north (upward, as
viewed in FIG. 6); and
[0015] FIG. 7 is a schematic chart showing the oscillating
schedules for controlling the ICF of each of the two vehicles shown
in FIG. 6.
DETAILED DESCRIPTION
[0016] Referring to the drawings, wherein like reference numbers
correspond to like or similar components throughout the several
figures, there is shown in FIG. 1 a schematic diagram of two
anti-glare systems. The diagram shown in FIG. 1 is highly schematic
and many elements of the system may have been omitted in order to
clarify the diagram. A first anti-glare system 10 for a first
vehicle (not separately shown) is represented on the left side of
FIG. 1. The first vehicle may be a sedan, a convertible, an SUV, a
pickup truck, a motor cycle, or any other vehicle. The first
anti-glare system 10 includes a first windscreen 12, which may be a
glass windshield, a plastic windscreen for motorcycles, a helmet
visor, eye glasses, or other components through which the driver or
occupants of the first vehicle view light.
[0017] While the present invention is described in detail with
respect to automotive applications, those skilled in the art will
recognize the broader applicability of the invention. Those having
ordinary skill in the art will recognize that terms such as
"above," "below," "upward," "downward," et cetera, are used
descriptively of the figures, and do not represent limitations on
the scope of the invention, as defined by the appended claims.
[0018] The first windscreen 12 includes a selectively-darkenable
intensity control film (ICF), which may be referred to as a first
windscreen ICF 13. Generally intensity control films are thin
substances which may be attached to transparent objects (such as
the first windscreen 12) and may be controlled to selectively, and
variably, adjust the amount of light which is able to pass through
the ICF and the transparent object. The first windscreen ICF 13
covers much of the first windscreen 12. By controlling either a
voltage across the first windscreen ICF 13 or a current which
passes through the first windscreen ICF 13, a controller (not
separately shown) may change the first windscreen ICF 13 from
substantially transparent to substantially opaque, or may levels of
opacity therebetween.
[0019] The first anti-glare system 10 also includes a first light
source 14, which may be a headlamp, headlight, spot light, or other
source of projecting light. The first light source 14 is also
covered with a first light source ICF 15, which may be selectively
darkened to prevent escape of light (especially bright light) from
the first light source 14.
[0020] A first light sensor 18 is configured to sense the existence
of oncoming light sources and may also sense the intensity of light
sources. The first light sensor 18 is shown mounted on the first
windscreen 12, but the first light sensor 18 may be mounted
elsewhere. The first light sensor 18 may also be integrated with
the controller (not separately shown) to process signals from the
first light sensor 18 and control the first windscreen ICF 13.
Sensing the light source may also include sensing a light source
position.
[0021] In FIG. 1, an eye position 20 is a schematic representation
of the location of an occupant's eyes--such as the driver of the
vehicle. An eye position sensor 22 is configured to determine the
eye position 20 and signal the controller. Alternatively, the eye
position 20 may be estimated, instead of sensed by the eye position
sensor 22. For example, and without limitation, the eye position 20
may be estimated based upon known characteristics (such as height)
or biometric data of the driver or drivers, average population
characteristics, the position of an adjustable head rest, or
sensors located within the vehicle seat, seat back, or
headrest.
[0022] Once the eye position 20 and the position of an oncoming
light source, such as a third light source 44, are both known, an
intersecting region 24 can be determined. The third light source 44
may be a non-vehicular source, such as, and without limitation: a
bright road-side light, sign, or billboard; a spot light; or the
sun. The intersecting region 24 is located substantially along a
line from the third light source 44 position to the estimated eye
position 20
[0023] The first windscreen ICF 13 may include a matrix of ICF
cells (not shown in FIG. 1, but shown and described in as ICF cells
526 in FIG. 5), each of which may be selectively controlled.
Therefore, portions or regions of the first windscreen ICF 13 may
be made opaque while other regions remain transparent.
[0024] A second anti-glare system 30 for a second vehicle (not
separately shown) is represented on the right side of FIG. 1, and
may be a motorcycle or any other vehicle. The second anti-glare
system 30 includes a second windscreen 32, which may be a helmet
visor. The second windscreen 32 is covered with a second windscreen
ICF 33, which is in communication with a controller (not shown)
configured to selectively change the second windscreen ICF 33
between transparent, opaque, and semi-opaque states.
[0025] The second anti-glare system 30 also includes a second light
source 34, this light source may be the headlight or headlights of
the second vehicle. As shown in FIG. 1, the second light source 34
projects light toward the first vehicle and the first light source
14 projects light toward the second vehicle. The second light
source 34 is also covered with a second light source ICF 35, which
is controllable to selectively (and possibly variably) prevent
escape of light (especially bright light) from the second light
source 34.
[0026] A second light sensor 38 is shown mounted near the second
windscreen 32, but may be located else where on the second vehicle.
The second light sensor 38 may also be integrated with the
controller (not separately shown) to process signals from the
second light sensor 38 and to control the second windscreen ICF
33.
[0027] Referring now to FIGS. 2-4, and with continued reference to
FIG. 1, there is shown a schematic flow chart of an algorithm or
method 200 for reducing glare through a windscreen (such as the
first windscreen 12) of a vehicle (such as the first vehicle) from
a light source (such as the third light source 44) to an occupant.
The method 200 utilizes windscreens covered with a
selectively-darkenable ICF (such as the first windscreen ICF 13).
FIG. 3 shows a subroutine 300 of the method 200, and FIG. 4 shows a
subroutine 400 of the method 200.
[0028] For illustrative purposes, much of the method 200 may be
described with reference to many of the elements and components
shown and described in relation to FIG. 1. However, other
components may be used to practice the method 200 and the invention
defined in the appended claims. The exact order of the steps of the
algorithm or method 200 shown in FIGS. 2-4 is not required. Steps
may be reordered, steps may be omitted, and additional steps may be
included. As viewed in FIG. 2, decision steps answered positively
(as a yes) follow the path labeled with a "+" sign (the
mathematical plus or addition operator). Similarly, decision steps
answered negatively (as a no) follow the path labeled with a "-"
sign (the mathematical minus or subtraction operator).
[0029] Step 210: Sense Light Source(s).
[0030] The method 200 begins as the first light sensor 18 senses a
light source, such as the third light source 44. The first light
sensor 18 may be operating continually, such that any time a
sufficient light source is sensed the method 200 may be
initiated.
[0031] Step 212: Sense Intensity.
[0032] In order to determine whether or not the anti-glare system
needs to be implemented, the method 200 may sense the intensity of
the third light source 44. This functionality may be incorporated
into the first light sensor 18, such that only lights of sufficient
intensity (or brightness) will be registered by the first light
sensor 18 and trigger the method 200. Sensing the intensity of the
potential source of glare may include factoring in ambient light
conditions. For example, and without limitation, headlights of the
oncoming vehicle may not be registered by the first light sensor 18
during bright daylight but may be sufficiently intense to start the
method 200 during the evening or nighttime, or when weather
conditions cause low ambient light conditions.
[0033] The method 200 may be occurring on either or both of the
first vehicle and the second vehicle. The method 200 is described
largely in relation to the first anti-glare system 10 of the first
vehicle, but execution of the method 200 on the second anti-glare
system 30 of the second vehicle may be very similar, depending upon
the components with which each vehicle is equipped.
[0034] Step 214: Another Equipped Vehicle?
[0035] The method 200 then determines whether the oncoming light
source is from another vehicle which is equipped with a similar
anti-glare system. In FIG. 1, this may include determining whether
the sensed light source is from the second vehicle (the second
light source 34) or is an extraneous source, such as the third
light source 44. If the oncoming light source is from another
equipped vehicle, the two vehicles may cooperate in reducing the
glare from each other's light sources. However, if the oncoming
light source is not from an equipped vehicle, then the first
anti-glare system 10 will have to reduce glare with its own
components.
[0036] If step 214 determines that the sensed light source is not
emanating from another equipped vehicle, the method 200 proceeds to
a subroutine 300, the intersecting region subroutine. If the step
214 determines that the sensed light source is emanating from
another equipped vehicle (such as the second vehicle having the
second anti-glare system 30), the method 200 proceeds to a
subroutine 400, the switching system subroutine. Either of the
subroutines 300 or 400 may be implemented as independent
algorithms, separate from each other and separate from the
remainder of the method 200.
[0037] Subroutine 300: Intersecting Region Subroutine.
[0038] Generally, the intersecting region subroutine 300 looks to
create a small region of opacity with the first windscreen ICF 13
on the first windscreen 12. Therefore, the source of glare--either
the third light source 44 or the second light source 34--may be
blocked without blocking the whole range of the driver's vision.
The subroutine 300 may be used to reduce glare to the eyes of the
driver, to other occupants of the vehicle, or to both. For
illustrative purposes, the subroutine 300 is described in relation
to reducing glare from the third light source 44, which may be the
sun or a bright spot light located in the driver's field of vision
through the first windscreen 12.
[0039] Step 310: Source Position.
[0040] The subroutine 300 includes sensing a light source position.
The first light sensor 18 determines the position of the third
light source 44 relative to the first vehicle and the first
windscreen 12. Because the source of the glare--in this example the
third light source 44--may vary considerably, the location of the
third light source 44 may also vary considerably. The subroutine
300 may only be determining or sensing the direction of the third
light source 44. Therefore, the subroutine 300 may not be concerned
as to whether the source is 200 yards or 92 million miles away, but
is concerned with the direction and intensity of the third light
source 44.
[0041] Step 312: Eye Position.
[0042] The subroutine 300 includes either estimating the eye
position 20 of the occupant or sensing the eye position 20 of the
occupant. The eye position sensor 22 may determine the actual
location of each of the driver's eyes, the general location of the
driver's eyes, or of the driver's head (which provides an
approximation for the eyes).
[0043] Step 314: Calculate Intersecting Region.
[0044] The subroutine 300 also includes calculating the
intersecting region 24 of the first windscreen ICF 13. The
intersecting region 24 is located substantially along a line from
the position of the third light source 44 to the (estimated or
sensed) eye position 20.
[0045] Step 316: Match Intersecting Region to ICF Cells.
[0046] As shown in FIG. 5, the first windscreen ICF 13 may be
formed from the matrix of selectively-darkenable ICF cells 526. The
subroutine 300 includes matching the intersecting region 24 to one
or more of the ICF cells 526. The subroutine 300 may select the ICF
cell 526 whose center is nearest to the intersecting region 24, or
may select a plurality of ICF cells 526 which encompass or surround
the intersecting region 24. Therefore, the controller will be
configured to determine which ICF cell 526 or plurality of ICF
cells 526 are nearest to the intersecting region 24.
[0047] Step 318: Activate ICF Cells.
[0048] The subroutine 300 then includes darkening the intersecting
region 24, such that a reduced amount of light from the third light
source 44 passes through the intersecting region 24. If the first
windscreen ICF 13 includes the matrix of ICF cells 526, then step
318 would change the plurality of the ICF cells 526 encompassing
the intersecting region 24 to become sufficiently opaque to block
the glare from the third light source 44 from reaching the driver's
eyes. Therefore, the glare is reduced in the intersecting region
24, but the remainder of the first windscreen ICF 13 is
substantially transparent and the driver's field of vision is not
significantly reduced (the driver would not likely be looking at
the bright light emanating from the third light source 44
anyway).
[0049] Depending upon the intensity of the third light source 44,
the first windscreen ICF 13 may not need to be changed to
completely opaque in order to reduce the glare to the driver's
eyes. In an alternative configuration, the first windscreen ICF 13
may be capable of increasing the opacity without
separately-controllable ICF cells 526. The first windscreen ICF 13
may be composed of a single membrane or film, but still be capable
of selectively darkening regions or portions thereof, or the first
windscreen ICF 13 may be composed of an infinite number of very
small ICF cells 526.
[0050] Subroutine 400: Switching System Subroutine.
[0051] Generally, the switching system subroutine looks to make the
whole first windscreen ICF 13 opaque for short, oscillating periods
of time. The subroutine 400 may control both the first windscreen
ICF 13 and the first light source ICF 15 between a substantially
opaque state and a substantially clear state. On its own, this
oscillation reduces to the total passage of light and glare to the
eyes of occupants. When combined with a similar system on the
second vehicle, the drivers and occupants of both the first vehicle
and the second vehicle may be nearly-completely shielded from the
glare produced by the oncoming vehicle. Both the first anti-glare
system 10 and the second anti-glare system 30 are running the
subroutine 400, such that the subroutine may be considered to
include both vehicles or to be operating substantially
simultaneously, but separately, in both vehicles.
[0052] Step 410: Adjustable Schedules?
[0053] The method 200 has included sensing the first light source
14 with the second anti-glare system 30 of the second vehicle, and
sensing the second light source 34 with the first anti-glare system
10 of the first vehicle, and has already determined that both the
first anti-glare system 10 and the second anti-glare system 30 are
capable of running the switching system subroutine 400. Decision
step 410 determines if the vehicles are both capable of altering
the schedules of oscillation for the first windscreen ICF 13 and
the second windscreen ICF 33 between the opaque and transparent
states. This determination may be made by communication between the
first anti-glare system 10 and the second anti-glare system 30 or
by the first light sensor 18 and the second light sensor 38.
[0054] Step 412: Initiate Fixed Schedule A.
[0055] If both the first anti-glare system 10 and the second
anti-glare system 30 are not configured to adjust to each other's
schedules, the subroutine 400 proceeds to step 412. The first
anti-glare system 10 is equipped with its own fixed schedule (a
first schedule) and the controller begins oscillating the first
light source ICF 15 between the substantially opaque state and the
substantially clear state on the first schedule. Step 412 also
includes oscillating the first windscreen ICF 13 between the
substantially opaque state and the substantially clear state on the
first schedule. Therefore, the first anti-glare system 10 is
switching between states of blocking both incoming light with the
first windscreen ICF 13 and blocking outgoing light with the first
light source ICF 15.
[0056] Step 414: Initiate Fixed Schedule B.
[0057] The second anti-glare system 30 is equipped with its own
fixed schedule (a second schedule) and the controller begins
oscillating the second light source ICF 35 between the
substantially opaque state and the substantially clear state on the
second schedule. Step 414 also includes oscillating the second
windscreen ICF 33 between the substantially opaque state and the
substantially clear state on the second schedule. Therefore, the
second anti-glare system 30 is switching between states of blocking
both incoming light with the second windscreen ICF 33 and blocking
outgoing light with the second light source ICF 35. Both the first
and second schedules operate at high frequencies.
[0058] Step 416: Harmonic Beat.
[0059] The second schedule is different from the first schedule
because the first schedule has a first frequency and the second
schedule has a second frequency, which is different from the first
frequency. Therefore, as the first anti-glare system 10 oscillates
at the first schedule and the second anti-glare system 30
oscillates at the second schedule, a harmonic beat occurs between
the anti-glare systems of the two vehicles. The drivers of both the
first vehicle and the second vehicle may perceive the harmonic beat
as a fluctuating or pulsating of the oncoming light source, but
both drivers will also be exposed to significantly reduced amounts
of glare from the oncoming light source.
[0060] Depending upon the configuration of the first anti-glare
system 10 and the second anti-glare system 30, the second frequency
may be between one to thirty percent different from the first
frequency. Reducing the glare to the drivers of the first vehicle
and the second vehicle may be especially important in low light
conditions, such as night time driving, or when one or both of the
first vehicle and the second vehicle has its high beams on.
[0061] If both the first anti-glare system 10 and the second
anti-glare system 30 are configured to adjust to each other's
schedules, the subroutine 400 proceeds to steps 420 and 422. In
this situation, the subroutine 400 establishes oscillation
schedules for the first anti-glare system 10 and the second
anti-glare system 30 which allow the first windscreen ICF 13 to be
opaque and blocking glare from the second light source 34 when the
second light source ICF 35 is transparent. These schedules operate
on a common frequency. As used herein, opaque refers to any level
of opacity of the ICF which sufficiently reduces the passage of
light through the ICF to benefit vehicle occupants by reducing
glare. Depending upon the lighting conditions, this may be only
slightly opaque to simply reduce passage of light, or may be nearly
blackening the ICF to prevent all light passage.
[0062] In order to similarly block glare to both vehicles, the
second schedule is one hundred eighty degrees out of phase from the
first schedule, such that the first light source ICF 15 is in the
substantially opaque state while the second windscreen ICF 33 is in
the substantially clear state. Alternatively expressed, the second
schedule may be offset by .pi. radians from the second
schedule.
[0063] Steps 420 and 422: Determine Common Frequency.
[0064] The first anti-glare system 10 and the second anti-glare
system 30 select a common frequency for oscillating between the
opaque and the transparent states of the respective ICFs.
Therefore, if no harmonic beat will be established and, if the
phase lag for each vehicle is correctly established, the first
anti-glare system 10 and the second anti-glare system 30 will
operate in concert to reduce glare to and from the other, on-coming
vehicle.
[0065] Steps 424 and 426: Sense Angle to Magnetic North.
[0066] One mechanism for correctly establishing the phase lag is
for both the first anti-glare system 10 and the second anti-glare
system 30 to be sensing magnetic north. Referring to FIG. 6, and
with continued reference to FIGS. 1-5, there is shown a diagram 600
showing the direction of travel of the first vehicle and the second
vehicle relative to magnetic north, which is illustrated by a
double arrow 602.
[0067] An arrow 610 shows the direction of travel of the first
vehicle and an arrow 630 shows the direction of travel of the
second vehicle. The first anti-glare system 10 determines a first
offset angle 611 relative to magnetic north, and the second
anti-glare system 30 determines a second offset angle 631 relative
to magnetic north. As shown, the second offset angle 631 is
approximately 180 degrees rotated from the first offset angle 611.
The subroutine 400 includes calculating the first schedule as a
function of the first offset angle 611 and calculating the second
schedule as a function of the second offset angle 631.
[0068] Alternatively, when the vehicles are equipped with GPS
devices, the vehicles may sense geographic north and calculate the
offset angle relative to geographic north instead of magnetic
north. The first vehicle and the second vehicle may not always be
traveling exactly 180 degrees (head on) relative to each other.
However, this will often be the case, and when one or both of the
vehicles is rounding a corner, the offset angles will become closer
to 180 degrees as the glare from the oncoming light sources becomes
more intense.
[0069] Steps 428 and 430: Phase Lag from Common Clock.
[0070] The subroutine 400 may also include monitoring a common
clock cycle, such that calculating the first schedule includes
phase lagging the first offset angle 611 from the common clock
cycle, and calculating the second schedule includes phase lagging
the second offset angle 631 from the common clock cycle. The common
clock cycle provides a constant reference point for beginning the
schedules for the first anti-glare system 10 and the second
anti-glare system 30, respectively. Therefore, the first anti-glare
system 10 and the second anti-glare system 30 have a common
reference to allow scheduling ICF oscillations which allow the
second light source ICF 35 to be projecting light only while the
first windscreen ICF 13 is blocking light, and the first light
source ICF 15 to be projecting light only while the second
windscreen ICF 33 is blocking light.
[0071] Steps 432 and 434: Initiate First Schedule and Second
Schedule.
[0072] Referring to FIG. 7, and with continued reference to FIGS.
1-6, there is shown a schematic chart 700 illustrating the
oscillating schedules for controlling the ICFs on each of the first
anti-glare system 10 and the second anti-glare system 30, as
calculated relative to magnetic north in FIG. 6. A y-axis 710
represents the control state for the first windscreen ICF 13 and
the first light source ICF 15. When the control state is 1, the
first windscreen ICF 13 and the first light source ICF 15 are
active and opaque, such that a reduced amount of light passes
through. Similarly, when the control state is 0, the first
windscreen ICF 13 and the first light source ICF 15 are inactive
and transparent, such that most light passes through.
[0073] An x-axis 712 represents the passage of time for the first
anti-glare system 10 relative to the common clock cycle. Each
dashed line division along the x-axis 712 represents one half cycle
of the frequency, which may is equal to 180 degrees or .pi.
radians. A line 714 shows the first schedule for the first
windscreen ICF 13 and the first light source ICF 15. A first phase
lag 716 is calculated from the first offset angle 611, and either
delays or adjusts the first schedule by the first offset angle
611.
[0074] Similarly, a y-axis 720 represents the control state for the
second windscreen ICF 33 and the second light source ICF 35, and an
x-axis 722 represents the passage of time for the second anti-glare
system 30 relative to the common clock cycle. A line 724 shows the
second schedule for the second windscreen ICF 33 and the second
light source ICF 35. A second phase lag 726 is calculated from the
second offset angle 631, and either delays or adjusts the second
schedule by the second offset angle 631.
[0075] Steps 436 and 438: Near Complete Reduction in Glare.
[0076] As shown in FIG. 7, because the first offset angle 611 is
180 degrees from the second offset angle 631, the first phase lag
716 adjusts the first schedule (shown as line 714) to be
approximately 180 degrees different from the second schedule (shown
as line 724). Therefore, the first schedule is oscillating the
first windscreen ICF 13 between the substantially opaque state and
the substantially clear state while the second schedule 724 is
oscillating the second light source ICF 35 between the
substantially clear state and the substantially opaque state on the
second schedule 724. The first windscreen ICF 13 is in the
substantially opaque state during periods when the second light
source ICF 35 is in the substantially clear state. To the driver of
the first vehicle, the second light source 34 will be seen as a
very low-intensity source, and to the driver of the second vehicle,
the first light source 14 will be seen as a very low-intensity
source.
[0077] The detailed description and the drawings or figures are
supportive and descriptive of the invention, but the scope of the
invention is defined solely by the claims. While some of the best
modes and other embodiments for carrying out the claimed invention
have been described in detail, various alternative designs and
embodiments exist for practicing the invention defined in the
appended claims.
* * * * *