Laser ranging over-height vehicle detector system (LARA-OHVD)
A device for producing a triangular laser sheet. The device has an optical transmitter with a pair of plano-convex cylindrical lenses for circularizing infrared laser light and a plano-concave cylindrical lens for shaping the circularized light to produce a triangular laser sheet. A tilt sensor measures departure of the triangular laser sheet from a horizontal reference. The device projects a triangular sheet of infrared light that is useful for detecting over-height vehicles that are approaching a structure, such as a bridge.
1. A device for producing a triangular laser sheet, the device comprising:
an infrared laser source for emitting an infrared laser;
an optical transmitter comprising:
collimating optics comprising a first plano-convex cylindrical lens and a second plano-convex cylindrical lens that is disposed orthogonal to the first plano-convex cylindrical lens;
beam shaping optics comprising a plano-concave cylindrical lens;
wherein the collimating optics and the beam shaping optics are arranged such that the infrared laser sequentially passes through the first plano-convex cylindrical lens, the second plano-convex cylindrical lens and the plano-concave cylindrical lens, thereby producing a triangular laser sheet of infrared laser light;
an optical receiver for receiving reflected infrared laser light;
a processor for processing the reflected infrared laser light.
2. The device as recited in claim 1 , where in the infrared laser source, the optical transmitter, the tilt sensor, the optical receiver and the processor are housed within a single housing.
3. The device as recited in claim 1 , wherein the optical transmitter produces an output with a divergence between 0.2 mrad and 0.4 mrad.
4. The device as recited in claim 1 , further comprising a tilt sensor for measuring a tilt angle.
5. A laser ranging over-height vehicle detector system, the system comprising:
an overhead structure with a road traversing under the overhead structure;
a device disposed proximate the overhead structure, the device comprising:
an infrared laser source for emitting an infrared laser;
an optical transmitter comprising:
collimating optics comprising a first plano-convex cylindrical lens and a second plano-convex cylindrical lens that is disposed orthogonal to the first plano-convex cylindrical lens;
wherein the collimating optics is arranged such that the infrared laser sequentially passes through the first plano-convex cylindrical lens and the second plano-convex cylindrical lens;
a tilt sensor for providing a tilt angle;
an optical receiver for receiving reflected infrared laser light;
a processor for processing the tilt angle and the reflected infrared laser light.
6. The system as recited in claim 5 , wherein the device is disposed on a vertical surface of the overhead structure.
7. The system as recited in claim 6 , further comprising beam shaping optics comprising a plano-concave cylindrical lens, wherein the collimating optics and the beam shaping optics are arranged such that the infrared laser sequentially passes through the first plano-convex cylindrical lens, the second plano-convex cylindrical lens and the plano-concave cylindrical lens, thereby producing a triangular laser sheet of infrared laser light downward toward the road.
8. The system as recited in claim 7 , wherein the overhead structure has a desired clearance height and the device is installed at the height greater than the desired clearance height.
9. The system as recited in claim 7 , wherein the triangular laser sheet has a beam spread is that user adjustable in a horizontal direction.
10. The system as recited in claim 5 , wherein the device is disposed on a pole, wherein the pole is disposed adjacent the road.
11. A method for identifying an over-height vehicle, the method comprising steps of:
projecting, onto a road, a triangular laser sheet of infrared laser light with a device, wherein the device comprises
an infrared laser source for emitting an infrared laser;
an optical transmitter comprising:
collimating optics comprising a first plano-convex cylindrical lens and a second plano-convex cylindrical lens that is disposed orthogonal to the first plano-convex lens;
beam shaping optics comprising a plano-concave cylindrical lens;
wherein the collimating optics and the beam shaping optics are arranged such that the infrared laser sequentially passes through the first plano-convex cylindrical lens, the second plano-convex cylindrical lens and the plano-concave cylindrical lens, thereby producing a triangular laser sheet of infrared laser light;
a tilt sensor for providing a tilt angle between the triangular laser sheet and the road;
an optical receiver for receiving reflected infrared laser light;
wherein the device is disposed on an overhead structure with the road traversing under the overhead structure;
calculating a height for a vehicle that is approaching the overhead structure on the road, the calculating using installed height of the device, a measured distance to the vehicle and the tilt angle, thereby producing a calculated height of the vehicle.
12. The method as recited in claim 11 , wherein the overhead structure has a clearance height, the method further comprising comparing with the calculated height of the vehicle to the clearance height.
13. The method as recited in claim 12 , further comprising activating an alarm if the calculated height is more than the clearance height.