Emissive highway markers
A highway marker and vehicle mounted detection system in which the highway marker includes LEDs of different colors that can be selected under different conditions, and non-visible light LEDs for transmitting information to passing vehicles and between highway markers.
1. A highway marker comprising:
a housing;
a plurality of LED's mounted in the housing, at least two of the LEDs being operational to emit electromagnetic radiation at different frequencies to each other to produce different colors;
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 the LEDs so as to control the overall color of the highway marker 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 extending through the surface on which the marker is mounted and into a cooler region beyond the surface to provide thermal communication between the LEDs and the cooler region.
5. A highway marker according to claim 1 , wherein at least one LED emits electromagnetic radiation in the range of 10 −2 m to 10 −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 −2 m to 10 −8 m.
14. A highway marker according to claim 1 , wherein the LEDs include LEDs operating in at least one of the ultraviolet (UV) and infra red (IR) range.
15. A highway marker according to claim 1 , including an internal feedback providing a constant brightness of the LED's.