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Diffractive optical fluid shear stress sensor

Imported: 25 Feb '17 | Published: 06 Apr '04

Morteza Gharib, Daniel W. Wilson, Siamak Forouhar, Richard E. Muller, Dominique Fourguette, Darius Modarress, Frederic Taugwalder

USPTO - Utility Patents

Abstract

A diffractive optic sheer stress sensor operates by forming diverging fringes over a linear area of measurement. A diode laser focuses light onto a diffractive lens which focuses the light to respective slits. The slits form diverging fringes, and scattered light from the fringes is collected by a window and focused by another diffractive lens to a receiver.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects will now be described in detail with reference to the accompanying drawings, wherein:

FIG. 1 shows a schematic of the principle used according to the embodiment, to determine the shear stress;

FIG. 2 shows an illustration of the sensor assembly of a first embodiment;

FIGS. 3

a and

3

b show an exemplary fringe pattern;

FIG. 4 shows a layout of the quartz substrate used for the sensing;

FIGS. 5

a and

5

b show a first embodiment of the fringes of the diffractive optical element;

FIG. 6 shows a second embodiment of the diffractive optical element;

FIG. 7 shows a cross-sectional diagram of an isolation slot between the emitter and receiver;

FIG. 8 shows the basic packaging system of the embodiment;

FIGS. 9A-9C show positions of the optical fringes at different heights above the surface of the element;

FIGS. 10 and 11 respectively show exploded and assembled views of this shear stress sensor assembly;

FIG. 12 shows a graph of the velocity measurements outside the viscous sublayer and their relations; and

FIG. 13 shows a second embodiment for obtaining information from multiple velocity components.

Claims

1. An assembly, comprising:

2. An assembly as in claim 1, further comprising a processing element, which processes information indicative of the light collected by said light collecting part to determine information related to shear stress.

3. An assembly as in claim 1, wherein said illumination converting element is a diffractive optical element.

4. An assembly as in claim 1, wherein said optical substrate having first and second opposite surfaces, wherein said first optical surface is closer to said source of illumination, and said second optical surface is more distant from said source of illumination and adjacent maid measurement area, said optical substrate being optically transparent.

5. An assembly as in claim 4, wherein said optical substrate is formed of quartz.

6. An assembly as in claim 4, wherein said illumination converting element is located on said first surface of said optical substrate, and maid first and second slits are located on said second surface of said optical substrate.

7. An assembly as in claim 4, wherein said second surface of said optical substrate has an optical mask formed thereon of an optically blocking substance, said optical mask including slits therein forming said first and second slits.

8. An assembly as in claim 7, wherein said optical mask also includes a light collecting window therein, spaced from said first and second slits, and positioned to receive scattered light from particles in said measurement area.

9. An assembly as in claim 8, further comprising a second illumination converting element, on said first surface of said optical substrate, and positioned to receive light from said light collecting window.

10. An assembly as in claim 9, wherein said second illumination converting element includes a diffractive optical element.

11. An assembly as in claim 9, wherein said light collecting part comprises an optical detector.

12. An assembly as in claim 1, wherein said slits include 2 micron wide slits which are separated by 10 microns.

13. An assembly as in claim 4, further comprising an optical divider, dividing said optical substrate and optically isolating between a transmitting part of said optical substrate and a receiving part of said optical substrate.

14. An assembly as in claim 13, wherein said optical divider comprises a notch formed in said optical substrate, and an optically opaque device formed in said notch.

15. An assembly as in claim 1, wherein said illumination converting element includes a diffractive lens formed of PMMA.

16. An assembly as in claim 1, wherein said illumination converting element comprises a portion which is used to focus to a first slit, and another portion which is used to focus to a second slit.

17. An assembly as in claim 1, wherein said illumination converting element provides illumination to areas of both of first said second slits from a full portion of the object aperture.

18. An assembly as in claim 1, wherein said source of illumination includes a diode laser.

19. An assembly as in claim 1, wherein said source of illumination includes a fiber carrying illumination.

20. An assembly as in claim 1, wherein said source of illumination includes a fiber within a ferrule.

21. An assembly as in claim 20, wherein maid ferrule is formed of Zr.

22. An assembly as in claim 1, wherein said light collecting part includes a light detector, and a second illumination converting element, which provides scattered light from said measurement area to said light detector.

23. An assembly as in claim 22, wherein said second illumination converting element includes two separated illumination converting element, each receiving scattered light from a different location.

24. An assembly as in claim 13, wherein maid optical divider is formed of a colored epoxy.

25. A sensor, comprising:

26. A sensor as in claim 25, further comprising a laser source, providing laser light to said first diffractive lens.

27. A sensor as in claim 26, wherein said laser source includes a laser diode.

28. A sensor as in claim 26, wherein said laser source includes an optical fiber.

29. A sensor as in claim 25, wherein maid second diffractive lens includes first and second separated diffractive lenses, spaced from one another, and obtaining information from two separate locations.

30. A sensor as in claim 25, wherein said optical substrate includes a notch therein, separating an transmission area of said first diffractive lens and said slits from an collection area of said second diffractive lens and said window.

31. A sensor as in claim 30, wherein said notch is filled with an optically opaque material to optically isolating between said transmission area and said collection area.

32. A sensor as in claim 31, wherein said optically opaque material is colored epoxy.

33. A sensor as in claim 26, further comprising an optical receiver, receiving light from said second diffractive lens.

34. A sensor as in claim 33, further comprising a processing element, processing an output indicative of said light from said second diffractive lens.

35. A sensor as in claim 25, wherein said first and second diffractive lenses are formed of PMMA.

36. A sensor, comprising;

37. A sensor as in claim 36, wherein said optical substrate is formed of an optically transparent substance.

38. A sensor am in claim 37, further comprising a notch formed in said optically transparent substance, and an optically opaque substance in the notch.

39. A sensor as in claim 36, further comprising an optical source producing laser light to said first optical element.

40. A sensor as in claim 36, wherein said first and second optical elements are diffractive lenses.

41. A sensor as in claim 36, wherein said second optical element includes two separate optical elements receiving illumination from two separate locations.

42. A sensor as in claim 36, wherein there are two of said slits, and said first optical element directs separate foci to said two slits.

43. A sensor as in claim 42, wherein said first optical element includes a first portion which directs energy to one of said slits and a second portion which directs energy to another of said slits.

44. A sensor as in claim 42, wherein said first optical element uses an entire area of said element to direct energy to both of said slits.

45. A sheer stress sensor, comprising:

46. A sensor as in claim 45, wherein said optical substrate includes an optical isolator which isolates between said first area and said second area.

47. A sensor as in claim 45, wherein said first optical element is a diffractive lens.

48. A sensor as in claim 45, wherein said optical substrate includes a surface covered with an optical blocking material, and wherein said slits and said window are formed as openings in said optical blocking material.

49. A shear stress sensor, comprising:

50. A sensor as in claim 49, further comprising an optical receiver, receiving said scattered light from said second and third optical elements.

51. A sensor as in claim 50, further comprising a processor, which measures flow velocity at two points to determine said shear stress.

52. A sensor as in claim 51, further comprising an optical isolator which isolates between said first area and said second area.

53. A sensor as in claim 49, wherein said first, second and third optical elements are diffractive optical element.