SYSTEM AND METHOD FOR MONITORING VEHICULAR TRAFFIC WITH A LASER RANGEFINDING AND SPEED MEASUREMENT DEVICE UTILIZING A SHAPED DIVERGENT LASER BEAM PATTERN

• US 20130229644A1
• Filed: 03/02/2012
• Published: 09/05/2013
• Est. Priority Date: 03/02/2012
• Status: Active Grant

• Current Assignee: Kama-Tech (HK) Limited, Laser Technology Incorporated (Laser Technology)
• Original Assignee: Kama-Tech (HK) Limited, Laser Technology Incorporated (Laser Technology)
• Inventors: Chung, Jiyoon, Dunne, Jeremy G.
• Granted Patent: US 9,576,484 B2
• Time in Patent Office: Days
• US Class Current: 356/5.01
• CPC Class Codes: G01P 3/68 using optical means, i.e. using infrared, visible, or ultraviolet light G01P3/80 takes precedence ; by reflection of waves G01S17/58
• CPC Class Codes: G01S 17/58 Velocity or trajectory determination systems; Sense-of-movement determination systems
• CPC Class Codes: G01S 17/88 Lidar systems specially adapted for specific applications
• CPC Class Codes: G01S 7/481 Constructional features, e.g. arrangements of optical elements
• CPC Class Codes: G08G 1/052 with provision for determining speed or overspeed speed measuring in general G01P

Abstract

A system and method for monitoring vehicular traffic with a laser rangefinding and speed measurement device utilizing a shaped divergent laser beam pattern. In accordance with the present invention, a traffic monitoring device is disclosed which comprises a light emitting diode having a die element producing an asymmetric beam pattern, an aperture for at least partially precluding some portion of the beam pattern in a first direction while allowing the beam pattern in a second orthogonal direction to pass therethrough and a lens associated with the aperture for causing the laser beam exiting the aperture to diverge providing a cone-like beam of laser energy.

Claims

1. A traffic monitoring device comprising:

a source of laser light;

a lens for causing said laser light to diverge toward said target; and

a mask associated with said source of laser light and said lens for at least partially precluding some portion of said laser light from exiting said lens.

2. The traffic monitoring device of claim 1 wherein said source of laser light comprises a laser diode.

3. The traffic monitoring device of claim 2 wherein said laser diode is positioned with its die in a generally horizontally disposed position.

4. The traffic monitoring device of claim 1 wherein said mask comprises a slot having substantially parallel and spaced apart side potions disposed laterally of said source of laser light.

5. The traffic monitoring device of claim 1 wherein said lens comprises a plano-concave lens.

6. The traffic monitoring device of claim 1 wherein said lens comprises a plano-convex lens.

7. The traffic monitoring device of claim 1 further comprising a receive aperture for reception of at least a portion of said projected laser light reflected from a target.

8. The traffic monitoring device of claim 7 wherein said device is operative to calculate a distance of said target based on a time elapsed between emission of said projected laser light and reception of said projected laser light reflected from said target.

9. The traffic monitoring device of claim 8 wherein said distance is calculated by selectively ignoring any intervening precipitation or particles interposed between said target and said device.

10. The traffic monitoring device of claim 8 wherein said device is operative to calculate a speed of said target based upon a plurality of distance calculations over a given time interval.

11. The traffic monitoring device of claim 1 wherein said projected laser light directed toward said target presents a generally vertical angle of substantially on the order of 50 to 100 milliradians.

37. The traffic monitoring device of claim 1 wherein said exiting laser beam directed toward said target presents a generally vertical angle of substantially on the order of 50 to 100 milliradians.

12. A method for monitoring moving objects comprising:

projecting a divergent laser beam toward said moving object;

measuring a round trip flight time of said laser beam to and from said moving object; and

determining said distance to said moving object based upon one half of said round trip flight time.

13. The method of claim 12 comprising:

repeating said steps of measuring and determining; and

calculating a speed of said moving object based upon a plurality of said distance determinations over a time interval between said repeated steps of measuring and determining.

14. The method of claim 12 wherein said step of projecting comprises:

providing a source of laser light; and

causing said source of laser light to diverge toward said moving object.

15. The method of claim 14 wherein said step of causing said laser light to diverge is carried out by a plano-convex lens.

16. The method of claim 14 wherein said step of causing said laser light to diverge is carried out by a plano-concave lens.

17. The method of claim 14 further comprising:

attenuating portions of said laser light prior to said step of causing said laser light to diverge.

18. The method of claim 17 wherein said step of attenuating portions of said laser light is carried out by a mask.

19. The method of claim 18 wherein said mask comprises a slot having substantially parallel and spaced apart side potions disposed laterally of said source of laser light.

20. The method of claim 12 further comprising:

selectively ignoring any precipitation or particles.

21. The method of claim 12 wherein said step of projecting a divergent laser beam toward said moving object is carried out by a laser beam having a generally vertical angle of substantially on the order of 50 to 100 milliradians.

22. A method for calculating the speed of a moving object comprising:

successively measuring distances to said moving object;

if the time between successive measurements is greater than a determined time interval, calculating a speed of said moving object based upon said time between said successive measurements and said distance traveled there between; and

if the distance to said moving object between said successive measurements is greater than a determined distance, calculating said speed of said moving object based upon said distance traveled between said successive measurements and said time between said successive measurements.

23. The method of claim 22 wherein said speed of said moving object is determined by either said time between said successive measurements being greater than a determined time interval or said distance to said moving object between said successive measurements being greater than a determined distance.

24. The method of claim 22 wherein said step of successively measuring distances is carried out by a laser distance measuring device.

25. The method of claim 24 wherein said laser distance measuring device emits a shaped divergent beam pattern.

26. The method of claim 22 wherein said step of successively measuring distances is carried out by at least two laser distance measuring devices.

27. The method of claim 26 wherein said at least two laser distance measuring devices are configured in a master/slave relationship.

28. The method of claim 26 wherein said at least two laser distance measuring devices are positioned at an angle of substantially 3.5 degrees from one another.

29. A traffic monitoring device comprising:

a light emitting diode having a die element producing an asymmetric beam pattern of greater divergence in a first direction than in a second orthogonal direction; and

a lens associated with said light emitting diode for causing said laser beam to diverge toward a target.

30. The traffic monitoring device of claim 29 wherein said laser diode is positioned with its die element in a generally horizontally disposed position.

31. The traffic monitoring device of claim 29 wherein said lens comprises a plano-concave lens.

32. The traffic monitoring device of claim 29 wherein said lens comprises a plano-convex lens.

33. The traffic monitoring device of claim 29 further comprising a receive aperture for reception of at least a portion of said exiting laser beam reflected from said target.

34. The traffic monitoring device of claim 33 wherein said device is operative to calculate a distance of said target based on a time elapsed between emission of said exiting laser beam and reception of said exiting laser beam reflected from said target.

35. The traffic monitoring device of claim 34 wherein said distance is calculated by selectively ignoring any intervening precipitation or particles interposed between said target and said device.

36. The traffic monitoring device of claim 34 wherein said device is operative to calculate a speed of said target based upon a plurality of distance calculations over a given time interval.