U.S. patent application number 10/384197 was filed with the patent office on 2004-09-09 for emissive highway markers.
Invention is credited to Hunter, Charles Eric, Narayan, Drew G..
Application Number | 20040175232 10/384197 |
Document ID | / |
Family ID | 32927210 |
Filed Date | 2004-09-09 |
United States Patent
Application |
20040175232 |
Kind Code |
A1 |
Hunter, Charles Eric ; et
al. |
September 9, 2004 |
Emissive highway markers
Abstract
A highway marker comprising an emissive device positioned on a
highway, wherein said emissive device emits electromagnetic
radiation.
Inventors: |
Hunter, Charles Eric;
(Jefferson, NC) ; Narayan, Drew G.; (Durham,
NC) |
Correspondence
Address: |
Richard S. Faust
Suite 204
8384 Six Forks Road
Raleigh
NC
27615
US
|
Family ID: |
32927210 |
Appl. No.: |
10/384197 |
Filed: |
March 7, 2003 |
Current U.S.
Class: |
404/16 |
Current CPC
Class: |
E01F 9/559 20160201 |
Class at
Publication: |
404/016 |
International
Class: |
E01F 013/00 |
Claims
What is claimed is:
1. A highway marker comprising: a housing; a plurality of LED's
mounted in the housing, emitting electromagnetic radiation; a
photodetector generating a signal responsive to an ambient light
condition surrounding the housing; and a control circuit responsive
to the photodetector signal to control the electromagnetic
radiation from at east one LED to emit radiation of a predetermined
color as perceived by the human eye according to the spectral
sensitivity of the human eye for the ambient light condition.
2. A highway marker according to claim 1, further comprising a
power source integral with the housing for powering the plurality
of LED's.
3. A highway marker according to claim 1, further comprising a
cooling fin in thermal communication with at least one LED, wherein
the cooling fin dissipates LED generated heat.
4. A highway marker according to claim 1, further comprising a
thermally conductive member for mounting the housing to a surface,
wherein the thermally conductive member transfers heat between a
surface and the marker.
5. A highway marker according to claim 1, wherein at least one LED
emits electromagnetic radiation in the range of 10.sup.-2 m to
10.sup.-8 m.
6. A highway marker according to claim 1, wherein at least one LED
emits electromagnetic radiation that is filtered with tinted
material.
7. A highway marker according to claim 1, wherein at least one LED
has a substrate selected from silicon, gallium nitride, aluminum
nitride, aluminum oxide, silicon carbide, diamond, silicon
germanium, and germanium.
8. A highway marker according to claim 1, further comprising a
photovoltaic cell for generating power.
9. A highway marker according to claim 2, wherein the power source
is a battery.
10. A highway marker according to claim 2, wherein the power source
is a line power source.
11. A highway marker according to claim 1 further comprising a
power source and wherein the plurality of LED's and the power
source has a plurality of redundancies.
12. A highway marker according to claim 1 further comprising a
battery to heat the housing.
13. A highway marker according to claim 1, wherein the
photodetector is responsive to electromagnetic radiation in the
range of 10.sup.-2 m to 10.sup.-8 m.
14. A highway marker according to claim 1, wherein the LED's
transmit information regarding the location or traffic to
vehicle-mounted detection systems that receive and process the
signals.
15. A highway marker according to claim 1, including an internal
feedback providing a constant brightness of the LED's.
16. A highway marker comprising: a plurality of LED's; a
photodetector generating a signal responsive to ambient light
condition; and means for adjusting the wavelength of emitted
electromagnetic radiation of at least one LED to maintain a
predetermined color as perceived by the human eye according to the
spectral sensitivity of the human eye for the ambient light
condition.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application claims priority to U.S. Provisional
Application Serial No. 60/352,551, filed Mar. 8, 2002, which is
incorporated herein by reference in its entirety.
FIELD OF THE INVENTION
[0002] The invention relates to highway markers, more particularly
to emissive highway markers that include light sources that emit
electromagnetic radiation of desired wavelength(s) to enhance
highway safety.
BACKGROUND
[0003] Thousands of people die on America's highway each year
because of poor roadway markers. Many of these deaths occur in
accidents that are attributable to low light conditions or an
inability of the driver to adequately see curves and bends in the
approaching roadway. Driving at night can be particularly difficult
because many human beings have a lessened visual acuity in low
light conditions. Conventional highway markers that are purely
reflective do not adequately meet the needs of many people with
such lessened visual acuity.
[0004] A fundamental problem with traditional reflective highway
markers is that they reflect light in a straight path even though
many roadways are not necessarily straight. Additionally,
automotive headlights do not have consistent optical power across a
wide viewing angle. As such, optional power declines at the outer
edges of the headlight. This phenomenon is characteristic of all
back-reflective headlights.
[0005] Still another problem with conventional highway markers
commonly in use on highways today is that they reflect light of a
wavelength that is not easily detected by the human eye in low
ambient light conditions. Many reflective highway markers are
yellow. However, yellow is not necessarily the optimal color for
detection by the human eye in low light conditions. For example,
the lighting of airport runways is typically done using blue lights
because the human eye sees the wavelength of blue light better than
it can see light of the yellow wavelength. What is needed are
highway markers that can help reduce the number of injuries and
fatalities that occur on highways due to accidents precipitated by
inability to see highways, obstructions in the road, or other
dangers that drivers can encounter while traveling in low light
conditions.
SUMMARY
[0006] A highway marker system that comprises an emissive device
positioned on a highway, wherein said emissive device emits
electromagnetic radiation.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] FIG. 1A is a top view perspective of the emissive highway
marker of the present invention.
[0008] FIG. 1B is a side view perspective of the emissive highway
marker of the present invention.
[0009] FIG. 2 is an illustration of a highway equipped with
emissive highway markers.
DETAILED DESCRIPTION
[0010] Reference will now be made in detail to embodiments of the
invention, examples of which are illustrated in the accompanying
drawings. Whenever possible, the same reference numbers will be
used throughout the drawings to refer to the same or like
elements.
[0011] Emissive highway markers overcome the deficiencies of
traditional reflective highway markers illuminated by back
reflective automotive headlights because they give the driver
better opportunity to see curves and bends in a highway. Emissive
highway markers are capable of adjust the color of light emitted in
response to ambient light conditions. Various colors of light can
be used to convey information to the driver, such as the presence
of an intersection, a road hazard, inclement weather or the need to
be on a radio to receive regional or national emergency broadcast
instructions. The disclosed markers may also be equipped to monitor
the relative position and speed of passing vehicles and to
communicate that information to a computer on board the
vehicle.
[0012] Referring to FIGS. 1A and 1B, top and side views of an
emissive highway marker 100 are shown. FIG. 1A illustrates an
light-emitting diode (LED) array 110, a plurality of photodetectors
115, and a plurality of photovoltaic cells 120. FIG. 1 shows ASIC
current drivers 125, an aluminum cooling fin 130, aluminum alloy
cooling/positioning rods 135, a stress absorbing spring 140, and a
plastic or metal shell 145 which contains the assemblage. The
housing would also contain reflective materials to increase the
overall visibility of the marker (not shown). As is discussed
further below, marker 100 may further include a microprocessor and
radio transmitter and receiver.
[0013] In an embodiment, LED array 110 can be constructed of one or
more LED's that emit varying wavelengths of light. LED array 110
can include several types of LED's capable of emitting red, yellow,
green, blue, white, or other colors of light. LED array 110 may
also include LED's that emit light in the non-visible spectrum.
Some examples of LED's that would be suitable for use in the
present invention include, but are not limited to, LED's that emit
light in the blue and green portion of the electromagnetic
spectrum. These devices will, for example, typically be fabricated
from indium gallium nitride and/or gallium nitride layers with or
without suitable buffer layers on 6H or 4H silicon carbide
substrates (where 6H is the polytype or atomic arrangement),
aluminum oxide substrate, gallium nitride substrates or aluminum
nitride substrates. Typically, LED's that are suitable for use in
the present invention will be constructed from a substrate that
allows high thermal conductivity and high optical transmissivity.
While LED manufacturing techniques using aluminum nitride
substrates are still evolving, there are other commercially
available devices suitable for number 100, such as nitride devices
grown on both Al.sub.2O.sub.3 and silicon carbide substrates.
[0014] The basic function of traditional LED's is well known and
need not be discussed in great detail. In summary, applying a
voltage across the semi-conductive material of the LED induces an
electron to move from the valence band to the conduction band. When
the electron falls back down to the conduction band, it recombines
with "holes" and causes the LED to emit a photon. One drawback to
traditional LED technology is that optoelectronic devices degrade
over time and lose power efficiency. As LED's degrade, the
wavelength of the light emitted by the LED will change, causing a
shift in the color of the light produced
[0015] Marker 100 may be constructed using LED's that are not as
susceptible to degradation. For example, LED array 110 may employ
LED's fabricated from gallium nitride grown on Al silicon carbide,
gallium nitride or aluminum nitride. These devices emit
electromagnetic radiation in the ultraviolet (UV) or blue portion
of the spectrum and are coated with a phosphor. The UV emission
striking the phosphor-coated diode creates a stimulated emission of
white light that is not susceptible to color shift. The LED can in
turn be placed inside a blue or green tinted material, such as
plastic, that functions as a lens/filter to create blue or green
light that is not subject to a color shift Alternatively, the
phosphor-coated LED can itself emit light of a desired color, such
as blue, green, yellow or red. Further, other LED's systems may be
used as well.
[0016] In certain embodiments, the choice of light emitting
semiconductor device may depend on the environment in which marker
100 is intended for use. In addition, embodiments of marker 100 are
not limited by the type of LED used.
[0017] The number of LED's or other light emitting semi-conductive
devices used in the construction of marker 100 may also vary
according the environment. In addition to degradation over time,
the lifetime of an optoelectronic device is a function of the drive
current supplied to the device and the ambient temperature of the
environment in which the LED operates. For example, highway
surfaces can become very hot, and driving an optoelectronic device
at its rated current in such a hot environment may cause rapid
degradation in the device. An embodiment of marker 100 may be
constructed using a plurality LED's or other optoelectronic
devices. In this case, each emissive highway marker may be operated
at a low drive current while still providing sufficient emission of
light from the marker to be visible to the human eye in low light
conditions.
[0018] In one embodiment photodetectors 115 can be used to control
the emissions of the optoelectronic devices in response to changes
in ambient light conditions. Photodetectors 115 interface with a
microprocessor or an ASIC (not shown). Photodetectors 115 measure
ambient light conditions and provide a signal that is a function of
how many photons of light are impinging on the detector. The signal
from photodetector 115 can cause marker 100 to alter the color of
light emitted by LED array 110 in varying conditions. For example,
the human eye has a much higher responsivity to green light in high
ambient light conditions than it does to blue light, while in low
light the human eye has a higher responsivity to blue light. So in
high ambient light conditions, marker 100 may emit green light,
while in low ambient light conditions, blue light can be produced
by LED array 110. Each marker can be equipped with the necessary
optoelectronic devices for producing each different color. Markers
can also be controlled to emit other colors to signal the driver
that he is approaching a stop sign or an intersection.
[0019] Marker 100 can be controlled by a plurality of different
mechanisms. For example, marker 100 can be given a manual setting
at the time the marker is installed. Alternatively, the marker
could be controlled by an optically-activated device equipped with
a microprocessor or an ASIC that is responsive to non-visible
radiation such as IR or RF to permit remote control of the marker
in a manner similar to a TV remote control. Marker 100 may also use
a temperature measurement device that causes the marker to emit a
particular color of light in response to changes in the ambient
temperature. This embodiment would allow the motorist to be warned
that the roadway surface, in particular bridges, may have an
unusual condition, such as being icy. Similarly, detection
mechanisms for moisture on the roadway surface can be used in
conjunction with the markers, which allows the motorist to be
warned that the road surface may be wet or slippery. The color of
the markers may also change to indicate that the motorist should
tune in to an Emergency Management System radio broadcast, such as
in the event of a severe weather or other emergency.
[0020] LED arrays 110 can emit both visible and non-visible
electromagnetic radiation. The non-visible radiation can be used to
signal an enunciator device inside a vehicle to track the position
of the vehicle relative to the boundaries of the highway, such as
the median or the shoulder.
[0021] In another embodiment, optoelectronic devices such as laser
diodes in combination with a light emitting diode having a narrow
viewing angle, that emit IR or UV can be used to produce the
signal. The diodes can broadcast a multidirectional signal that is
unique to the marker. This signal can carry information regarding
the position of the individual marker and other traffic
information.
[0022] A detector system on the vehicle would receive the signal
from the marker. A computer within the vehicle will be able to
determine the exact position of the vehicle relative to the markers
by "listening" to multiple markers. This could be accomplished in
two ways. First, the marker could send information in predetermined
intervals. Second, information regarding the interval could be
incorporated in the signal. With the time interval emitted and the
time interval received, the computer would be able to determine the
vehicle's magnitude of velocity with respect to one marker. Thus
based on multiple markers, the computer could triangulate the
vehicle's position relative to the markers.
[0023] The detector system could be composed of one photodetector,
several photodetectors, or in a preferred embodiment, an array of
photodetectors. The array of photodetectors would contain a
plurality of devices tuned to specific wavelengths outside the
visible spectrum. Certain photodetectors could have bandpass
filters. These devices integrated into an array would cover large
portions of the spectrum, thereby creating a solid state
spectrographer. This would vastly increase the amount of
information that could be transmitted from the markers to the
detector system.
[0024] An enunciator in the vehicle can warn the driver and
passengers of the vehicle in the event the vehicle is traveling too
close to the shoulder or median or is traveling too fast for road
conditions, or is approaching an intersection or stop sign or some
other warning. The speed and position data gathered by a vehicle's
computer from the markers may also be used to automatically print
speeding tickets. In addition, discreet marker locations can work
in conjunction with a global positioning system (GPS) to provide
exact street and highway location, confirmation or
annunciation.
[0025] Markers 100 can also detect the presence of a stopped
vehicle or other obstruction in the roadway. The presence of a
stopped vehicle or other obstruction can cause the marker detecting
the obstruction to signal other highway markers in the proximity of
the obstruction to emit, for example, a yellow light indicating the
potential hazard. The signal may be sent between markers via any
medium, including IR and RF.
[0026] FIG. 2 shows a section of a highway equipped with markers as
described above. Markers 200 emit light according to the ambient
conditions to delineate a curve 230 in the highway. For example,
markers 200 may emit blue light at night. Alternatively, markers
2000 may emit green light during daylight hours.
[0027] In another embodiment, as a vehicle 200 approaches the inner
portion of a curve 230, the curve markers 220 and 210 clearly
delineate for the driver the curve even though markers 200 and 210
may not be directly illuminated by the headlights of vehicle 220.
In addition, as vehicle 220 rounds curve 230 and approaches a
stalled vehicle 240, markers 210 alert the driver of vehicle 220 to
the impending hazard posed by stalled vehicle 240 by emitting, for
example, yellow light. Similarly, markers 200 and 210 can detect
light from headlights of vehicle 220 and alert people around curve
230 of the approach of vehicle 220. In addition to changing colors
in response to ambient light or highway conditions, marker 200 or
210 may be directed to change the color of emitted light upon
receipt of an RF, IR, or other signal, where the signal originates
from a central station or from another marker. While performing the
above described functions, markers 200 or 210 may simultaneously
emit signals to a computer on board vehicle 220 to indicate the
relative speed and position of vehicle 220. These signals can
typically be IR or RF.
[0028] In one embodiment, the shell would be fabricated from metal.
The metal would provide flexibility and impact strength. In another
embodiment, the housing would be injection molded from a glass or
carbon reinforced plastic such as polycarbonate. This plastic is
sold under the trade names Lexan by the GE Plastics of Pittsfield,
Mass. Lexan 141 or 503 as well as several other grades would be
suitable for this application. Other plastics that would be
appropriate include Acrylonitrile Butadiene Styrene (ABS) and
Acrylic Styrene Acrylonitrile (ASA).
[0029] Other embodiments of the invention will be apparent to those
skilled in the art from consideration of the specification and
practice of the invention disclosed herein. It is intended that the
specification and examples be considered as exemplary only, with a
true scope and spirit of the invention being indicated by the
following claims.
* * * * *