Active 3D monitoring system for traffic detection

• US 8,842,182 B2
• Filed: 12/22/2010
• Issued: 09/23/2014
• Est. Priority Date: 12/22/2009
• Status: Active Grant

• Current Assignee: LeddarTech, Inc.
• Original Assignee: LeddarTech, Inc.
• Inventors: Mimeault, Yvan, Perreault, Louis, Dubois, Martin
• Primary Examiner(s): Dang, Hung
• Assistant Examiner(s): Park, Sunghyoun
• Application Number:
  US13/512,407
• Publication Number:
  US 20120307065A1
• Time in Patent Office: 1,371 Days
• Field of Search: 348/149
• US Class Current: 348/149
• CPC Class Codes: G01S 17/04 Systems determining the presence of a target
• CPC Class Codes: G01S 17/86 Combinations of lidar systems with systems other than lidar, radar or sonar, e.g. with direction finders
• CPC Class Codes: G01S 17/89 for mapping or imaging
• CPC Class Codes: G08G 1/04 using optical or ultrasonic detectors

Abstract

The traffic detection system includes an optical unit having an emitter module emitting pulses; a receiver module having a field of view including a plurality of adjacent detection channels receiving pulses reflected by an object and acquiring and converting the received pulses into a corresponding plurality of a digital signal waveforms; an image sensing module providing an image. The method comprises providing a status overlay image including the image and a visual indication on the image of an outline of the plurality of adjacent detection channels; positioning the field of view to cover the detection zone using the status overlay image; obtaining the plurality of digital signal waveforms; detecting a signal echo caused by an object in one of the digital signal waveforms at a position within the field of view; determining a location for the object using the position; storing the location for the object.

Claims

1. A method for detecting the presence of an object in a detection zone using a traffic detection system, wherein said object is one of a moving object and a stationary object, the method comprising:

providing said traffic detection system including an optical unit having

an optical emitter module emitting short light pulses within a predetermined field of emission, said field of emission being a field of illumination;

an optical receiver module receiving a part of the light pulses reflected by an object in said field of emission toward a field of view of said receiver module said field of view including a plurality of adjacent detection channels, said receiver module acquiring for a period of time after the emission of said pulses and converting said received light pulses into a corresponding plurality of a digital signal waveforms, and

an image sensing module providing an image that encompasses the field of emission of the emitter module and the field of view of the receiver module;

providing a status overlay image for said field of view including said image and a visual indication on said image of an outline of said plurality of adjacent detection channels;

positioning the field of view of said receiver module to cover said detection zone using said status overlay image;

obtaining said plurality of digital signal waveforms using said traffic detection system;

detecting a signal echo in one of said digital signal waveforms at a position within said field of view, said signal echo being caused by said presence of said object in said field of view;

determining a location in said field of view for said object using said position including calculating a time taken by the emitted pulses to travel from the optical unit to the object and return back to the optical unit;

storing said location for said object, and

sending said stored location to an external processor.

2. The method as claimed in claim 1, wherein said detection zone is defined along a stop bar of an approach of a road intersection.

3. The method as claimed in claim 2, further comprising applying image processing on said image to detect candidate objects, extracting a position of said candidate objects in said field of view from said image, using said extracted position to generate said call.

4. The method as claimed in claim 1, further comprising:

identifying which detection channel produced said signal waveform in which said signal echo is detected;

using said status overlay image, determining a traffic lane corresponding to said identified detection channel;

detecting the presence of the object in the determined traffic lane.

5. The method as claimed in claim 4 further comprising:

providing a minimum and a maximum detection distances from said optical unit within said field of view for said detection channels;

generating a call if said signal echo is within said minimum and maximum detection distances for said determined traffic lane;

sending said call to a traffic controller.

6. The method as claimed in claim 5, further comprising detecting a signal echo in the signal waveform at a position closer to the optical unit than the minimum detection distance and holding said call.

7. The method as claimed in claim 1, further comprising providing a threshold amplitude for the echo, said detecting a signal echo comprises comparing an amplitude of the signal echo to the threshold amplitude, said threshold amplitude being one of an amplitude absolute value and an amplitude relative value varying as a function of said position.

8. The method as claimed in claim 1, further comprising determining an amplitude of the signal echo, grouping compatible echoes based on echo properties in an echo group, said echo group being a set of signal echoes in different channels, the echo properties being at least one of said location being substantially the same, said amplitude being substantially the same and an overall group location of said echo group including said location.

9. The method as claimed in claim 8, further comprising matching the group to an object type.

10. The method as claimed in claim 1, wherein said optical emitter module emits short pulses of light at a wavelength invisible to the human eye.

11. The method as claimed in claim 1, wherein said traffic detection system further includes a pan and tilt assembly for said optical unit, said pan and tilt assembly being adapted to pivot said optical unit in a controlled manner about at least one of three orthogonal axes;

the method further comprising orienting said pan and tilt assembly to coarsely point said optical unit toward said detection zone and using said status overlay image and said pan and tilt assembly to pivot said optical unit and allow a precise pointing of the optical unit common line of sight toward said detection zone.

12. The method as claimed in claim 11, further comprising identifying permanent markers in said status overlay image and using said identified permanent markers to precisely align said optical unit using said pan and tilt assembly.

13. The method as claimed in claim 1, further comprising providing at least one sensor, each sensor being at least one of a temperature sensor, an inclinometer, a compass, an accelerometer and a global positional system, said method further comprising using information captured by said at least one sensor for at least one of said positioning said field of view, said detecting said signal echo and said determining said location.

14. The method as claimed in claim 1, further comprising providing an angular position sensor for generating information about a current angular position of the optical unit, said method further comprising using said information about said current angular position for said positioning said field of view.

15. The method as claimed in claim 1, further comprising repeating said steps of obtaining, detecting and determining for a number of repetitions;

tracking said location of said object in said field of view in each repetition;

determining a displacement speed of said object in said field of view using successive ones of said tracked locations for said object.

16. The method as claimed in claim 1, further comprising sending said status overlay image to an external processor.

17. The method as claimed in claim 1, further comprising repeating said providing an image that encompasses the field of view by said image sensing module to obtain a sequence of images, carrying out compression on said sequence of images, generating a compressed video output and sending said compressed video output to an external processor.

18. The method as claimed in claim 1, further comprising applying image processing on said image to detect candidate objects, extracting a position of said candidate objects in said field of view from said image, using said extracted position to guide said determining said location for said object.

19. The method as claimed in claim 1, wherein said positioning the field of view of said receiver module to cover said detection zone using said status overlay image further comprises:

sending said status overlay image to an external processor;

receiving a detection zone location information;

positioning said field of view using said detection zone location information.

20. The method as claimed in claim 19, wherein said detection zone location information includes at least one of an outline for said detection zone, a width of a traffic lane, an installation height for said optical unit, said minimum distance and said maximum distance.

21. The method as claimed in claim 1, wherein said positioning the field of view of said receiver module to cover said detection zone using said status overlay image further comprises:

sending a series of said status overlay image to an external processor;

receiving a validation for a detected object located in said detection zone on at least one of status overlay image of said series;

determining said detection zone location based on said validation;

positioning said field of view using said detection zone location.

22. The method as claimed in claim 1, wherein said positioning the field of view of said receiver module to cover said detection zone using said status overlay image further comprises:

sending said status overlay image to an external processor;

storing an aerial view of an area surrounding and including said detection zone;

receiving data concerning an installation of said optical unit;

comparing said status overlay image to said aerial view and using said data to determine a detection zone location for said detection zone in said status overlay image;

positioning said field of view using said detection zone location.