Method and apparatus for measuring particle motion optically

• US 20060152722A1
• Filed: 02/17/2006
• Published: 07/13/2006
• Est. Priority Date: 07/31/2002
• Status: Active Grant

• Current Assignee: Jan Arwood Northby
• Original Assignee: Jan Arwood Northby
• Inventors: Northby, Jan Arwood
• Granted Patent: US 7,453,569 B2
• Time in Patent Office: Days
• US Class Current: 356/337
• CPC Class Codes: G01P 5/20 using particles entrained by a fluid stream G01P5/22 takes precedence
• CPC Class Codes: G01P 5/22 using auto-correlation or cross-correlation detection means
• CPC Class Codes: G01S 17/58 Velocity or trajectory determination systems; Sense-of-movement determination systems
• CPC Class Codes: G01S 17/87 Combinations of systems using electromagnetic waves other than radio waves
• CPC Class Codes: G01S 7/4912 Receivers

Abstract

A method and apparatus for measuring particle motion using electromagnetic radiation uses beams of radiation modulated with a distinct frequency and/or phase. A particle traversing these beams scatters a portion of the radiation. Scattered radiation, which retains its modulation information, is then detected, and a cross-correlation technique is used to quantify the particle'"'"'s motion, for example, particle velocity.

Claims

1. An apparatus for measuring particle motion, the apparatus comprising:

a plurality of beams of radiation, each of said plurality of beams modulated at a respective, pre-determined frequency and a respective, pre-determined phase, said plurality of beams of radiation directed to at least one particle;

a detector positioned to receive radiation scattered from each of said plurality of beams by said at least one particle;

a processor in electrical communication with said detector, said processor cross-correlating radiation scattered from at least two of said plurality of beams by said at least one particle.

2. The apparatus of claim 1, wherein said radiation scattered comprises a random component and at least one modulation frequency, the random component having at least one of its characteristic frequencies lower than the modulated frequency of any of said plurality of beams.

3. The apparatus of claim 1, further comprising a phase sensitive detection circuit in electrical communication with said detector.

4. The apparatus of claim 1, wherein said plurality of beams of radiation comprises planes of radiation.

5. The apparatus of claim 1, wherein the apparatus is adapted to measure a time-of-flight distribution.

6. The apparatus of claim 5, wherein the apparatus is adapted to measure an aerodynamic size distribution of particles.

7. The apparatus of claim 1, wherein the apparatus is adapted to measure fluorescent emission.

8. The apparatus of claim 1, wherein at least one particle is a cell.

9. The apparatus of claim 1, wherein the apparatus is adapted to measure pollution.

10. The apparatus of claim 5, wherein the apparatus is adapted to measure a particle property related TOF distribution.

11. The apparatus of claim 1, wherein at least one of said plurality of beams of radiation is adapted for traversing a detection region.

12. The apparatus of claim 1, wherein the apparatus is adapted to measure velocity derivatives.

13. The apparatus of claim 1, wherein said plurality of beams of radiation form a beam pattern.

14. The apparatus of claim 13, wherein the beam pattern is adapted to measure properties of particles at rest.

15. The apparatus of claim 1, wherein the detector is a segmented detector.

16. The apparatus of claim 1, wherein the apparatus is adapted to measure particle velocity at a point in space.

17. The apparatus of claim 1, wherein the apparatus is adapted to measure a particle selected from the group consisting of a biological particle, a cell, dust, a pollutant, a contaminant, a portion of a blood sample, a surface imperfection, and a pathogen.

18. A method of measuring motion of a particle, the method comprising:

directing radiation from a plurality of beams to at least one particle, each of said plurality of beams modulated at a respective, pre-determined frequency and a respective, pre-determined phase;

detecting radiation scattered from each of said plurality of beams by said at least one particle; and

cross-correlating said radiation scattered from at least two of said plurality of beams by said at least one particle to measure the motion of said at least one particle.

19. The method of claim 18, wherein said radiation scattered comprises a random component and at least one modulation component, the random component having at least one of its characteristic frequencies lower than the modulation frequency of any of said plurality of beams.

20. The method of claim 18, wherein said plurality of beams comprises planes of radiation.

21. The method of claim 18, wherein separation of said at least two of said plurality of beams is determined by the distance over which the velocity of said particle is substantially unchanged.

22. The method of claim 18, further comprising the step of moving at least one of the plurality of beams.

23. The method of claim 18 further comprising modulating at least one of said plurality of beams with a square wave.

24. The method of claim 23, further comprising modulating at least one of said plurality of beams at a frequency between about 20 kHz and 100 MHz.

25. The method of claim 18, further comprising modulating at least one of the plurality of beams at a frequency different from another of said plurality of beams.

26. The method of claim 18, wherein said plurality of beams comprises two orthogonal beam pairs.

27. The method of claim 18, wherein said plurality of beams comprises three orthogonal beam pairs.

28. The method of claim 18, wherein said plurality of beams comprises a plurality of non-orthogonal beam pairs.

29. The method of claim 18, further comprising calculating particle velocity.

30. The method of claim 18, further comprising calculating particle size.

31. The method of claim 18, wherein the pre-determined frequency of a first beam of the plurality of beams is substantially similar to the pre-determined frequency of a second beam of the plurality of beams, and the pre-determined phase of the first beam of the plurality of beams is substantially orthogonal to the pre-determined phase of the second beam of the plurality of beams.

32. The method of claim 18, wherein the at least one particle is contained in a fluid.

33. The method of claim 32, wherein particle velocity corresponds to velocity of said fluid.

34. An apparatus for measuring particle motion, the apparatus comprising:

two beams of radiation, each of said beams modulated at a respective, pre-determined frequency and a respective, pre-determined phase, said beams of radiation directed on at least one particle;

a detector positioned to receive radiation scattered from said beams by said at least one particle;

a processor in electrical communication with said detector, said processor cross-correlating radiation scattered from said beams by said at least one particle.

35. The apparatus of claim 34, wherein said radiation scattered comprises a random component and at least one modulation frequency, the random component having at least one of its characteristic frequencies lower than the modulated frequency of any of said plurality of beams.

36. The apparatus of claim 34, wherein the at least one particle is contained in a fluid.

37. A method of measuring a plurality of particles, the method comprising the steps of:

directing radiation from a plurality of beams to at least one particle, each of the plurality of beams modulated at a respective, pre-determined frequency and a respective, pre-determined phase;

detecting radiation scattered from each of the plurality of beams by the at least one particle as a single signal, and

extracting information associated with each of the plurality of beams from the single signal.

38. The method of claim 37 wherein the extracted information is processed using separate electrical channels.