Laser rangefinder sensor

• US 9,170,096 B2
• Filed: 01/27/2014
• Issued: 10/27/2015
• Est. Priority Date: 09/13/2011
• Status: Active Grant

• Current Assignee: OSI Optoelectronics, Inc. (OSI Systems Incorporated)
• Original Assignee: OSI Optoelectronics, Inc. (OSI Systems Incorporated)
• Inventors: Fowler, Keith, Lai, Nan-Ming
• Primary Examiner(s): Punnoose, Roy M
• Application Number:
  US14/165,160
• Publication Number:
  US 20140313518A1
• Time in Patent Office: 638 Days
• Field of Search: 356/601
• US Class Current: 1/1
• CPC Class Codes: G01B 11/24 for measuring contours or curvatures
• CPC Class Codes: G01S 17/08 for measuring distance only indirect measurement G01S17/46; active triangulation systems G01S17/48
• 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 17/42 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 7/4808 Evaluating distance, position or velocity data
• CPC Class Codes: G01S 7/4817 relating to scanning
• CPC Class Codes: G01S 7/4865 Time delay measurement, e.g. time-of-flight measurement, time of arrival measurement or determining the exact position of a peak peak detection in noise, signal conditioning G01S7/487
• CPC Class Codes: G06T 2207/10028 Range image; Depth image; 3D point clouds
• CPC Class Codes: G06T 2207/30236 Traffic on road, railway or crossing
• CPC Class Codes: G06T 7/521 from laser ranging, e.g. using interferometry; from the projection of structured light
• CPC Class Codes: G06V 10/147 Details of sensors, e.g. sensor lenses fingerprint or palmprint sensors G06V40/13; vascular sensors G06V40/145; eye sensors G06V40/19
• CPC Class Codes: G06V 20/54 of traffic, e.g. cars on the road, trains or boats
• CPC Class Codes: G08G 1/04 using optical or ultrasonic detectors

Abstract

The specification discloses a pulsed time-of-flight laser range finding system used to obtain vehicle classification information. The sensor determines a distance range to portions of a vehicle traveling within a sensing zone of the sensor. A scanning mechanism made of a four facet cube, having reflective surfaces, is used to collimate and direct the laser toward traveling vehicles. A processing system processes the respective distance range data and angle range data for determining the three-dimensional shape of the vehicle.

Claims

1. A system for determining the three-dimensional shape of a vehicle, the system comprising:

a sensor for generating a plurality of laser beams and for detecting a plurality of reflected beams, each of said reflected beams corresponding to one of the plurality of generated laser beams;

a controller in data communication with said sensor to trigger the generation of the laser beams at predefined scan angles; and

a processing system to determine distance ranges from the sensor to portions of the vehicle for each of said scan angles using time-of-flight measurements derived from timings of said generated laser beams and reflected beams, when the vehicle travels within a sensing zone of the sensor and to determine a three-dimensional shape of the vehicle based on distance ranges, wherein said processing system comprises at least two time-to digital converters (TDCs) for performing said time-of-flight measurements and wherein, during a scan, said processing system is configured to switch back and forth between each of said TDCs such that eight reflected beams may be received in no more than 70 nanoseconds.

2. The system for determining the three dimensional shape of vehicle according to claim 1, further comprising a scanning mechanism, positioned relative to the sensor, for collimating each of said generated laser beams across the vehicle, wherein said scanning mechanism comprises a four facet cube, each having a reflective surface, wherein said four facet cube is positioned relative to the sensor such that it is adapted to reflect the generated laser beams.

3. The system for determining the three dimensional shape of vehicle according to claim 2, wherein the four facet cube rotates continuously in one direction at a constant speed.

4. The system for determining the three dimensional shape of vehicle according to claim 2, wherein the four facet cube enables four scans for each revolution.

5. The system for determining the three dimensional shape of vehicle according to claim 1, further comprising a scanning mechanism comprising two four facet structures capable of rotating relative to each other, wherein the first four facet structure is adapted to receive and reflect laser beams generated by the laser source and the second four facet structure is adapted to receive and reflect the reflected energy from the vehicles or road in the scanning zone.

6. The system for determining the three dimensional shape of vehicle according to claim 1, wherein each of said two TDCs is adapted to receive up to four return pulses from a single laser pulse.

7. The system for determining the three dimensional shape of vehicle according to claim 1, wherein the system generates a plurality of laser footprints and wherein said laser footprints appear as stripes that touch end to end and provide a continuous line of detection.

8. The system for determining the three dimensional shape of vehicle according to claim 1, wherein the distance range resolution of the system is +/−

1 cm.

9. A method for determining a three-dimensional shape of a vehicle passing through a sensing zone of a sensor comprising a laser transmitter and a photo detector, the method comprising:

scanning a plurality of laser beams across the vehicle using a controller that triggers the laser beams at predefined scan angles;

using a processing system, determining a distance range from the sensor to portions of the vehicle for each of said scan angles using time-of-flight measurements, wherein said processing system comprises at least two time-to digital converters (TDCs) for performing said time-of-flight measurements and wherein, during a scan, said processing system is configured to switch back and forth between each of said TDCs such that eight reflected laser beams may be received in no more than 70 nanoseconds; and

processing the distance range data for each scan angle to determine the three-dimensional shape of the vehicle.

10. The method for determining a three-dimensional shape of a vehicle according to claim 9, further comprising scanning a plurality of laser beams across the vehicle using a scanning mechanism comprising a four facet cube, said four facet cube having reflective surfaces that are used to direct the laser beams across its field of view in a straight line.

11. The method for determining a three-dimensional shape of a vehicle according to claim 10, wherein the four facet cube rotates continuously in one direction at a constant speed during scan.

12. The method for determining a three-dimensional shape of a vehicle according to claim 10, wherein the scanning cube is adapted to produce four scans for each revolution.

13. The method for determining the three dimensional shape of vehicle according to claim 9, further comprising scanning a plurality of laser beams across the vehicle using a scanning mechanism comprising two four facet structures capable of rotating relative to each other, wherein the first four facet structure is adapted to receive and reflect laser beams generated by a laser source and the second four facet structure is adapted to receive and reflect the reflected energy from the vehicles or road in the scanning zone.

14. The method for determining a three-dimensional shape of a vehicle according to claim 9, wherein each of said TDCs is adapted to receive up to four return pulses from a single laser pulse.

15. The method for determining a three-dimensional shape of a vehicle according to claim 14, wherein the system generates a plurality of laser footprints during a scan and wherein each of said laser footprints appear as stripes that touch end to end and provide a continuous line of detection.