OPTICAL LEVEL MEASUREMENT DEVICE AND METHOD

• US 20110026015A1
• Filed: 04/03/2009
• Published: 02/03/2011
• Est. Priority Date: 04/04/2008
• Status: Active Grant

• Current Assignee: LeddarTech, Inc.
• Original Assignee: LeddarTech, Inc.
• Inventors: Perreault, Louis, Mimeault, Yvan
• Granted Patent: US 8,159,660 B2
• Time in Patent Office: Days
• US Class Current: 356/139.1
• CPC Class Codes: G01F 23/292 Light , e.g. infrared or ultraviolet
• CPC Class Codes: G01F 23/2928 using light reflected on the material surface
• 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 17/87 Combinations of systems using electromagnetic waves other than radio waves
• CPC Class Codes: G01S 17/88 Lidar systems specially adapted for specific applications
• CPC Class Codes: G01S 7/4866 by fitting a model or function to the received signal

Abstract

A method and system for determining a level of a substance in a container, the method comprises emitting one pulse from a light source in a field of illumination toward a surface of said substance in said container. A backscatter signal of said pulse is detected by an optical detector. A lidar trace is created from said backscatter signal, said lidar trace including at least one reflection peak; A surface reflection is identified among said at least one reflection peak in said lidar trace, said surface reflection being a reflection of said pulse from said surface. The surface reflection is signal-fitted to provide a fitted surface trace. A level of said substance is determined in said container using said fitted surface trace.

Claims

1. A method for determining a level of a substance in a container, the method comprising:

emitting one pulse from a light source in a field of illumination toward a surface of said substance in said container;

detecting a backscatter signal of said pulse by an optical detector;

creating a lidar trace from said backscatter signal, said lidar trace including at least one reflection peak;

identifying a surface reflection among said at least one reflection peak in said lidar trace, said surface reflection being a reflection of said pulse from said surface;

signal-fitting said surface reflection to provide a fitted surface trace; and

determining a level of said substance in said container using said fitted surface trace.

2. The method as claimed in claim 1, wherein said identifying said surface reflection comprises signal-fitting each of said at least one reflection peak and determining a best matched reflection peak to be said surface reflection.

3. The method as claimed in claim 1, wherein said identifying said surface reflection comprises identifying a last one of said at least one reflection peak to be said surface reflection.

4. The method as claimed in claim 1, wherein said substance is a transparent liquid and wherein said identifying said surface reflection comprises eliminating a container bottom reflection from said at least one reflection peak using a known shape for a reflection from a bottom of said container.

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

detecting a reference backscatter signal of said pulse by a reference optical detector at said emission of said pulse thereby acquiring a reference zero value and a reference trace for said pulse;

comparing said reference trace for said pulse to said combined trace; and

determining a distance traveled by said pulse based on said comparison.

9. The method as claimed in claim 1, wherein said signal-fitting comprises curve-fitting a non-symmetrical quasi-Gaussian function on said trace.

10. The method as claimed in claim 9, wherein said curve-fitting uses the point corresponding to the peak of the curve as the reference position, wherein the curve is quasi-Gaussian in that the exponent is not 2, the equation being:

11. The method as claimed in claim 10, wherein finding the values of the parameters A, μ

and v, comprises plugging the combined trace in the equation f(x) and a minimization algorithm is used with the following equations;

12. The method as claimed in claim 11, wherein finding the value comprises using the following starting point:

A=the highest value of y, μ

=the x position of the highest value and v=5.8.

13. The method as claimed in claim 1, wherein said detecting further comprises

using at least one other optical detector for detecting at least one other backscatter signal of said pulse;

and

multiplexing said backscatter signal with said at least one other backscatter signal.

16. The method as claimed in claim 1, wherein said determining the level comprises determining the level of one of a liquid, a paste and a solid.

20. The method as claimed in claim 1, further comprising controlling said light source by a pulse driver to modify an output power of said light source.

21. The method as claimed in claim 20, further comprising providing a detection parameter and wherein said controlling uses said detection parameter.

22. The method as claimed in claim 21, wherein said providing said detection parameter comprises providing a reflectivity parameter, said reflectivity parameter being indicative of a reflectivity of at least one of said substance and walls of said container.

23. The method as claimed in claim 21, wherein said providing said detection parameter comprises providing a range parameter, said range parameter being indicative of a level of said substance in said container.

24. The method as claimed in claim 21, wherein said providing said detection parameter comprises providing a clarity parameter, said clarity parameter being indicative of a dust density inside the container.

6. (canceled)

7. (canceled)

8. (canceled)

14. (canceled)

15. (canceled)

17. (canceled)

18. (canceled)

19. (canceled)

25. A fill-level sensing device for determining a level of a substance in a container comprising:

a light source for emitting light in a field of illumination toward a surface of said substance in said container;

a pulse driver for driving the light source into emitting one pulse;

an optical detector adapted to detect a backscatter signal of said pulse; and

a data/signal processor for creating a lidar trace from said backscatter signal, said lidar trace including at least one reflection peak, for identifying a surface reflection among said at least one reflection peak in said lidar trace, said surface reflection being a reflection of said pulse from said surface;

for signal-fitting said surface reflection to provide a fitted surface trace; and

for determining a level of said substance in said container using said fitted surface trace.

26. The fill-level sensing device according to claim 25, wherein the light source is one of a light-emitting diode (LED) and a laser.

27. The fill-level sensing device according to claim 25, further comprising a timer, the timer being triggered by the data/signal processor to calculate a time elapsed between said emission of said pulse and said detection of said backscatter signal, the data/signal processor determining a distance traveled by said pulse based on said time elapsed.

33. The fill-level sensing device according to claim 25, further comprising an analog-to-digital converter for sampling the backscatter signal of said pulse, and a pre-processing and synchronisation unit for controlling parameters of said pulse from the analog-to-digital converter.

34. The fill-level sensing device according to claim 33, wherein the parameters are at least one of the optical power of the light pulse, the number of pulses used for pre-process operation, a gain of amplifier, a synchronization between the pulse driver and the analog-to-digital converter, and a sample rate of analog-to-digital converter.

28. (canceled)

29. (canceled)

30. (canceled)

31. (canceled)

32. (canceled)

35. (canceled)

36. (canceled)