Intelligent vehicle highway system multi-lane sensor and method

• US 5,793,491 A
• Filed: 10/11/1996
• Issued: 08/11/1998
• Est. Priority Date: 12/30/1992
• Status: Expired due to Term

• Current Assignee: OSI Defense Systems LLC (OSI Systems Incorporated)
• Original Assignee: Schwartz Electro-Optics Incorporated
• Inventors: Gustavson, Robert L., Wangler, Richard J., McConnell, Robert E. II, Fowler, Keith L.
• Primary Examiner(s): Hellner, Mark
• Application Number:
  US08/730,732
• Time in Patent Office: 669 Days
• Field of Search: 356/4.01, 356/5.01, 356/376, 356/398
• US Class Current: 356/613
• CPC Class Codes: G01S 17/10 using transmission of interrupted, pulse-modulated waves determination of distance by phase measurements G01S17/32
• CPC Class Codes: G01S 17/14 wherein a voltage or current pulse is initiated and terminated in accordance with the pulse transmission and echo reception respectively, e.g. using counters
• CPC Class Codes: G01S 17/18 wherein range gates are used
• CPC Class Codes: G01S 17/42 Simultaneous measurement of distance and other co-ordinates indirect measurement G01S17/46
• CPC Class Codes: G01S 17/88 Lidar systems specially adapted for specific applications
• CPC Class Codes: G01S 17/89 for mapping or imaging
• CPC Class Codes: G01S 7/4802 using analysis of echo signal for target characterisation; Target signature; Target cross-section
• CPC Class Codes: G01S 7/481 Constructional features, e.g. arrangements of optical elements
• CPC Class Codes: G01S 7/4817 relating to scanning
• CPC Class Codes: G01S 7/486 Receivers
• CPC Class Codes: G01S 7/497 Means for monitoring or calibrating
• CPC Class Codes: G08G 1/04 using optical or ultrasonic detectors

Abstract

An Intelligent Vehicle Highway System (IVHS) sensor provides accurate information on real-time traffic conditions that can be used for incident detection, motorist advisories, and traffic management via signals, ramp meters, and the like. A diode-laser-based Vehicle Detector And Classifier (VDAC) measures the presence, speed, and three-dimensional profiles of vehicles passing beneath it within its multi-lane field-of-view coverage. The sensor uses pulsed laser range imaging technology adapted for determining the three-dimensional profile of the vehicle. The VDAC employs a rotating polygon mirror to scan a pulsed laser rangefinder across three lanes of a highway in order to measure the presence, speed, and height profiles of vehicles in all three lanes simultaneously. A receiver accepts reflections from beams transmitted from the sensor and provides inputs for determining time of flight, and a time interval between interceptions of the two divergent beams for the vehicle. An encoder tracks the position of the mirror for providing angle data with associated range measurements. The VDAC high signal-to-noise ratio and good spatial resolution result in highly accurate traffic-parameter measurements.

Claims

1. A sensor useful in determining the shape of a vehicle, the sensor comprising:

laser rangefinder means for determining a range from the sensor to points on a vehicle when the vehicle travels within a sensing zone and for providing range data outputs corresponding to sensor angles for ranges from the sensor to the points on the vehicle;

means for scanning the laser means within a plane generally orthogonal to a direction of travel for the vehicle, the scanning means communicating with the laser rangefinder means for determining a range for a corresponding point on the vehicle within the transverse plane, the scanning means providing means for determining the range and a corresponding sensor angle for each point within the scanning plane;

deflecting means cooperating with the scanning means for deflecting the scanned beam from a first position to a second position, the first and second positions defining a forward beam and a backward beam through which the vehicle travels; and

means for processing the ranges, corresponding angles, and interception times for the vehicle receiving the first and second beams, the processing means providing a vehicle image profile representative of the vehicle.

2. A sensor useful in determining the shape of vehicles traveling over multiple adjacent lanes of a highway, the sensor comprising;

a housing for positioning above a highway having multiple lanes for receiving vehicles traveling thereover;

first and second laser transmitters carried by the housing, each laser transmitter transmitting a series of radiation pulses forming first and second beams respectively, the first and second transmitters each providing a trigger signal indicating the transmitting of each pulse within the series;

a beam scanner carried by the housing, the beam scanner having multiple reflective facets positioned for receiving the first and second transmitted beams and directing the beams toward the highway, the reflective facets intercepting the beams at varying incident angles for reflecting the beams through the varying angles and scanning the beams transversely across the highway, the scanned beams cooperating for providing a scan extending transversely across the multiple lanes, the reflective facets further arranged such that adjacent facets receiving the transmitted beams have differing orientations for alternately reflecting the beam from a first facet into a forward scanned beam and from a second facet into a rearward scanned beam, the forward and rearward scanned beams longitudinally divergent from each other, the beam scanner communicating with the first and second transmitters for providing an orientation signal indicating a direction of beam propagation for each transmitted pulse within the beam;

first and second laser receivers carried by the housing, each laser receiver receiving reflected first and second beams including pulses reflected back from the highway and vehicle for the respectively transmitted pulses of the first and second transmitted beam, the first and second receivers providing a return pulse signal indicating the receipt of each reflected portion of the transmitted pulse within the series; and

a processor carried by the housing for processing the signals from the transmitters, receivers and scanner for providing range measurements from the sensor to the highway, from the sensor to the vehicle, corresponding angles for each range measurement, and a time for the vehicle to cross the forward and rearward scanned beams, the processor providing vehicle information useful in classifying the vehicle.

3. The sensor according to claim 2, wherein the laser transmitters comprise InGaAs diode laser transmitters.

4. The sensor according to claim 2, wherein the laser receivers comprise silicon avalanche photodiode receivers.

5. The sensor according to claim 2, wherein the beam scanner comprises a polygon rotating about a shaft, the polygon having the facets portioned continuously about the shaft for intercepting the transmitted beams, and wherein the first and second facets are adjacent facets positioned at an offset angles to each other for providing the forward and the rearward diverging beams.

6. The sensor according to claim 5, wherein the offset angle is approximately ten degrees.

7. The sensor according to claim 5, further comprising a shaft encoder engaging the shaft for providing a signal indicative of the shaft polygon orientation and thus the beam angle, the shaft encoder providing the orientation signal.

8. The sensor according to claim 2, further comprising a folding mirror carried within the housing for directing the beams from each of the transmitters and receivers to the beam scanner.

9. The sensor according to claim 2, wherein each receiver comprises an optical detector for detection of the reflected beam, the optical detector providing the return pulse signal.

10. The sensor according to claim 2, wherein the housing includes a light transmissive window for transmitting the beams therethrough, the window having a heater for maintaining a preselected temperature of the window during varying ambient conditions.

11. A sensor useful in determining the shape of vehicles traveling over multiple adjacent lanes of a highway, the sensor comprising:

first and second laser transmitters, each transmitting a series of radiation pulses forming first and second beams respectively, the first and second transmitters providing a trigger signal indicating the transmitting of each pulse within the series;

a beam scanner having multiple reflective facets positioned for receiving the first and second transmitted beams and directing the beams toward the highway, the reflective facets intercepting the beams at varying incident angles for reflecting the beams through the varying angles and scanning the beams transversely across the highway, the scanned beams cooperating for providing a scan extending transversely across the multiple lanes, the reflective facets further arranged such that alternating facets receiving the transmitted beams have differing orientations for alternately reflecting the beam from a first facet into a forward reflected beam and from a second facet into a rearward reflected beam, the forward and rearward beams longitudinally divergent from each other, the beam scanner communicating with the first and second transmitters for providing an orientation signal indicating a propagation direction for each transmitted pulse;

first and second laser receivers, each laser receiver receiving reflected first and second beams having a portion of the respectively transmitted pulses of the first and second transmitted beam, the first and second receivers providing a return pulse signal indicating the receipt of each reflected portion of the transmitted pulse within the series; and

a processor for processing the signals from the transmitters, receivers and scanner for providing range measurements from the sensor to the highway, from the sensor to the vehicle, corresponding angles for each range measurement, and a time for the vehicle to cross the forward and rearward beams, the processor providing vehicle information useful in classifying the vehicle.

12. The sensor according to claim 11, wherein the beam scanner comprises a polygon rotating about a shaft, the polygon having the facets portioned continuously about the shaft for intercepting the transmitted beams, and wherein the first and second facets are adjacent facets positioned at an offset angle to each other for providing the forward and the rearward diverging beams.

13. The sensor according to claim 12, wherein the offset angle is approximately ten degrees.

14. The sensor according to claim 12, further comprising a shaft encoder engaging the shaft for providing a signal indicative of the shaft polygon orientation and thus the beam angle, the shaft encoder providing the orientation signal.

15. The sensor according to claim 11, wherein each receiver comprises an optical detector for detection of the reflected beam, the optical detector providing the return pulse signal.

16. A sensor useful in determining the shape of vehicles traveling over multiple adjacent lanes of a highway, the sensor comprising:

a laser transmitter for transmitting a series of radiation pulses, the transmitter providing a trigger signal indicating a transmission of each pulse;

a scanner having multiple reflective facets positioned for receiving the transmitted pulses and directing the pulses toward the highway, the reflective facets intercepting the pulses at varying incident angles for reflecting them through the varying angles and scanning the series of pulses transversely across the highway, the reflective facets further arranged such that alternating facets receiving the transmitted pulses have differing orientations for alternately reflecting the pulses from a first facet into a forward reflected series of pulses and from a second facet into a rearward reflected series of pulses, the forward and rearward transmitted series of pulses within a direction longitudinally divergent from each other, the scanner communicating with the transmitter for providing an orientation signal indicating a propagation direction for each transmitted pulse;

a receiver for receiving reflected pulses, the receiver providing a return pulse signal indicating the receipt of each reflected pulse; and

a processor for processing the signals from the transmitter, receiver and scanner for providing range measurements from the time of transmission of a transmitted pulse to the time of receipt of a corresponding reflected pulse, the range measurements made from the sensor to the highway and from the sensor to the vehicle, corresponding angles for each range measurement and a time for the vehicle to cross the forward and rearward scanning planes provide vehicle profile and speed information useful in classifying the vehicle.

17. The sensor according to claim 16, wherein the beam scanner comprises a polygon rotating about a shaft, the polygon having the facets portioned continuously about the shaft for intercepting the transmitted pulses, and wherein the first and second facets are adjacent facets positioned at an offset angle to each other for providing the forward and the rearward scanning planes.

18. The sensor according to claim 16, wherein the offset angle is approximately ten degrees.

19. The sensor according to claim 16, further comprising a shaft encoder engaging the shaft for providing a signal indicative of the shaft polygon orientation and thus a direction of propagation for the transmitted pulse, the shaft encoder providing the orientation signal.

20. The sensor according to claim 16, wherein each receiver comprises an optical detector for detection of the reflected beam, the optical detector providing the return pulse signal.

21. A sensor useful in determining the shape of vehicles traveling over multiple adjacent lanes of a highway, the sensor comprising:

a laser rangefinder for transmitting and receiving a beam of pulsed radiation for determining a range to a point on a vehicle;

a scanner having multiple reflective facets positioned for receiving the transmitted beam and directing the beam transversely across the vehicle, the reflective facets intercepting the beam at varying incident angles for reflecting them through the varying angles and scanning the beam transversely across the vehicle, the reflective facets further arranged such that alternating facets receiving the transmitted pulses have differing orientations for alternately reflecting the beam into a forward reflected beam portion and into a rearward reflected beam portion, the forward and rearward transmitted beams longitudinally divergent from each other, the scanner communicating with the laser rangefinder for providing an orientation signal indicating a propagation direction for each transmitted pulse within the beam; and

a processor for processing the signals from the laser rangefinder and scanner for providing range measurements for corresponding angles and a time for the vehicle to cross the forward and rearward scanning beams for providing vehicle profile and speed information useful in classifying the vehicle.

22. The sensor according to claim 21, wherein the beam scanner comprises a polygon rotating about a shaft, the polygon having the facets portioned continuously about the shaft for intercepting the transmitted beam, and wherein the first and second facets are adjacent facets positioned at an offset angle to each other for providing the forward and the rearward scanning beams.

23. The sensor according to claim 22, wherein the offset angle is approximately ten degrees.

24. The sensor according to claim 22, further comprising a shaft encoder engaging the shaft for providing a signal indicative of the shaft polygon orientation and thus a direction of propagation for the transmitted beam, the shaft encoder providing the orientation signal.