Fluid borne particle analyzers

• US 20060250606A1
• Filed: 12/21/2005
• Published: 11/09/2006
• Est. Priority Date: 06/26/2003
• Status: Active Grant

• Current Assignee: Secretary of State For Defence
• Original Assignee: Secretary of State For Defence
• Inventors: Kaye, Paul Henry, Hirst, Edwin
• Granted Patent: US 7,436,515 B2
• Time in Patent Office: Days
• US Class Current: 356/73
• CPC Class Codes: G01J 3/4406 Fluorescence spectrometry
• CPC Class Codes: G01N 1/24 Suction devices G01N1/22 - G01N1/2294 take precedence
• CPC Class Codes: G01N 15/0211 Investigating a scatter or diffraction pattern
• CPC Class Codes: G01N 2021/6467 Axial flow and illumination
• CPC Class Codes: G01N 21/05 Flow-through cuvettes G01N21/09 takes precedence; handling fluid samples G01N1/10
• CPC Class Codes: G01N 21/53 within a flowing fluid, e.g. smoke
• CPC Class Codes: G01N 21/645 Specially adapted constructive features of fluorimeters
• CPC Class Codes: G01N 21/6486 Measuring fluorescence of biological material, e.g. DNA, RNA, cells G01N21/6428 takes precedence
• CPC Class Codes: G01N 2201/065 Integrating spheres

Abstract

This invention describes an improved method and apparatus for the analysis of fluid borne particles and which is especially suitable for the detection of airborne biological particles. In one aspect the invention provides an apparatus for the detection of fluid borne particles which comprises: a zone through which a fluid to be analysed flows, in use; a source of illumination to illuminate/irradiate fluid borne particles present in said zone; and a detector to detect light from the particles as an indicator of the presence or characteristics of the particles, wherein the apparatus comprises an integrating sphere and the zone is within the integrating sphere. The apparatus is highly sensitive and can be used for detecting airborne particles even where the particles are present at very low particle concentrations in the air.

Claims

1. An apparatus for the detection of fluid borne particles which comprises:

a zone through which a fluid to be analysed flows, in use;

a source of illumination to illuminate/irradiate fluid borne particles present in said zone; and

a detector to detect light from the particles as an indicator of the presence or characteristics of the particles, wherein the apparatus comprises a pair of opposed concave reflective surfaces and the zone is between these surfaces, the apparatus having two sources and two detectors, the first of the two detectors detecting a first wavelength band and the second of the detectors detecting a second wavelength band that is narrower than the first band and falls within the first band, the first source illuminating/irradiating within a wavelength band that is below the wavelength detecting band of the first detector but within the wavelength detecting band of the second detector.

2. An apparatus as claimed in claim 1 wherein the first of the two detectors detects a wavelength band of about 340 to about 600 nm and the second detector detects a band of 410 to 600 nm, the first source has a wavelength band of about 260 to about 290 nm.

3. An apparatus as claimed in claim 1, wherein the second source has a wavelength band of about 340 to about 380 nm.

4. An apparatus as claimed in claim 3, wherein the first and second detectors are arranged along a first axis and the first and second source are arranged along a second axis substantially orthogonal to the first axis and the fluid flow is along a third axis substantially orthogonal to the first and second axes.

5. An apparatus as claimed in claim 1, wherein the apparatus comprises a pair of opposed concave reflective surfaces and the zone is between these surfaces.

6. An apparatus for the detection of particles as claimed in claim 5, wherein each of the pair of opposed substantially concave reflective surfaces comprises a respective discrete mirror.

7. An apparatus for the detection of particles as claimed in claim 5, wherein the apparatus comprises an integrating sphere and the pair of opposed concave reflective surfaces are reflective surfaces of the integrating sphere.

8. An apparatus for the detection of particles as claimed in claim 1, wherein the fluid to be analysed flows through the zone along a flow path and the illuminations irradiation source is directed along the flow path.

9. An apparatus for the detection of particles as claimed in claim 8 as dependent on claim 7, wherein the illumination/irradiation and the fluid enter the integrating sphere by a common aperture.

10. An apparatus for the detection of particles as claimed in claim 1, having an integrating sphere and wherein the fluid is constrained to flow through a transparent tube extending through the zone and which extends along the diameter of the integrating sphere.

11. An apparatus for the detection of particles as claimed in claim 10, wherein the apparatus further comprises an optically absorbing beam-dump at the distal end of the tube to absorb the illumination/irradiation beam.

12. An apparatus for the detection of particles as claimed in claim 10, wherein the illumination/irradiation is directed along the tube as a beam and the diameter of the beam is such that the beam fills most of the tube without coming into contact with the tube walls.

13. An apparatus for the detection of particles as claimed in claim 10, wherein the apparatus incorporates a detector at the distal end of the tube to measure the power of the illumination/irradiation beam.

14. An apparatus for the detection of particles as claimed in claim 1, wherein the source is a pulsed light source.

18. An apparatus for the detection of fluid borne biological particles as claimed in claim 1, the apparatus being adapted for the detection of fluid borne biological particles, wherein the source of illumination serves to illuminate/irradiate fluid borne particles present in said zone and to excite the particles to fluoresce, and the apparatus has a detector to detect fluorescence from the particles as an indicator of the presence of biological particles, wherein the sphere has an optical detector at a detecting aperture in the sphere for sensing fluorescence radiation, the optical detector having a spectrometer or a number of different filters that are selectable between to enable a range of different wavelength bands to be monitored.

19. An apparatus for the detection of fluid borne biological particles as claimed in claim 1, wherein the apparatus further comprises a fan as the means to cause airflow through the zone.

20. An apparatus for the detection of fluid borne biological particles as claimed in claim 5, wherein each mirror is of substantially spherically concave type and the pair are substantially coaxially opposed to each other.

21. An apparatus for the detection of fluid borne biological particles as claimed in claim 5, wherein each respective substantially spherically concave mirror has a central aperture and has a respective detector to detect light received through the aperture from the other mirror.

22. An apparatus for the detection of fluid borne biological particles as claimed in claim 20, wherein the axis linking the centres of the opposed substantially spherically concave mirrors is substantially orthogonal to an axis of illumination from the source of illumination.

23. An apparatus for the detection of fluid borne biological particles as claimed in claim 1, wherein the apparatus has two or more different sources of illumination.

24. An apparatus for the detection of fluid borne biological particles as claimed in claim 23, wherein the at least two sources of illumination comprise two xenon sources each emitting a different wavelength band of light to the other.

25. An apparatus for the detection of fluid borne biological particles as claimed in claim 23, wherein the different light sources are spatially distinct from each other.

26. An apparatus for the detection of fluid borne biological particles as claimed in claim 23, wherein the apparatus has a single light source element and which is switchable between different wavelength bands of emission.

27. An apparatus for the detection of fluid borne biological particles as claimed in claim 26, wherein the light source element(s) is/are xenon light source elements having a low pass filter between the source and the zone to allow only the lower wavelengths that are in the appropriate range to excite fluorescence to pass.

28. An apparatus for the detection of fluid borne biological particles as claimed in claim 27, wherein the filter only allows radiation at or under about 370 nanometers to pass.

29. An apparatus for the detection of fluid borne biological particles as claimed in claim 23, wherein there are two xenon light source elements and each has a different respective filter.

30. An apparatus for the detection of fluid borne biological particles as claimed in claim 29, wherein one light source element/filter combination emits light up to about 290 nanometers and the other emits light from above 290 nanometers

31. An apparatus for the detection of fluid borne biological particles as claimed in claim 30, wherein the other light source element/filter combination emits light from above 290 nanometers to about 380 nanometers

32. An apparatus for the detection of fluid borne biological particles as claimed in claim 23 as dependent on claim 21, wherein the two spatially discrete light sources are spaced apart in a configuration each along an axis wherein the axis is substantially orthogonal to an axis linking the detectors.

33. An apparatus for the detection of fluid borne biological particles as claimed in claim 21, wherein an axis linking the detectors is substantially aligned with an axis linking the centres of each of the opposed spherical mirrors.

34. An apparatus for the detection of fluid borne biological particles as claimed in claim 23, wherein the apparatus further comprises a processor configured to operate the apparatus in a manner whereby the source of illumination alternately changes between two or more different band widths of wavelength.

35. An apparatus for the detection of fluid borne biological particles as claimed in claim 34, wherein the processor is further programmed to process signals sensed from the one or more detectors to provide a ratio of sensed signal for one wavelength or wavelength band of illuminating light relative to sensed signal for a different wavelength or band of wavelength of illuminating light.

36. An apparatus for the detection of fluid borne biological particles as claimed in claim 35, wherein the processor is programmed to process signals sensed from the one or more detectors to provide a ratio of sensed signal for one wavelength or wavelength band of illuminating light relative to sensed signal for a different wavelength or band of wavelength of illuminating light at each of two or more different sensed wavelengths or bands of wavelength of detected fluorescence signal.

37. An apparatus for the detection of fluid borne biological particles as claimed in claim 1, wherein the apparatus has two or more detectors each with a different wavelength pass/bandpass.

15. An apparatus for the detection of fluid borne particles which comprises:

a zone through which a fluid to be analysed flows, in use;

a source of illumination to illuminate/irradiate fluid borne particles present in said zone; and

a detector to detect light from the particles as an indicator of the presence or characteristics of the particles, wherein the apparatus comprises a pair of opposed concave reflective surfaces and the zone is between these surfaces wherein the fluid is constrained to flow through a transparent tube extending through the zone and wherein said source being a source of non-monochromatic light; and

the apparatus has a detector to detect fluorescence from the particles as an indicator of the presence of biological particles wherein the illumination/irradiation is directed along the tube as a beam and the diameter of the beam is such that the beam fills most of the tube without coming into contact with the tube walls.

16. An apparatus for the detection of fluid borne biological particles as claimed in claim 15, having an integrating sphere and wherein the sphere has a first optical detector at a first detecting aperture in the sphere for sensing the flux of scattered UV light in the sphere and a second optical detector at a second detecting aperture in the sphere having a filter to block scattered UV light but allowing longer wavelength fluorescence radiation in the sphere to be sensed.

17. An apparatus for the detection of fluid borne biological particles as claimed in claim 15 wherein the source is a pulsed light source and the apparatus incorporates a detector at the distal end of the tube to measure the energy/power of the illumination/irradiation beam, the output values from the or each scattered light or fluorescence detector being normalised, in use, by the pulse energy level as sensed by the detector at the distal end of the tube so as to mitigate against any errors that might arise from pulse to pulse energy variation.

38. A method for the detection of fluid borne particles comprising the provision of an apparatus for the detection of fluid borne particles which comprises:

a zone through which a fluid to be analysed flows, in use;

a source of illumination to illuminate/irradiate fluid borne particles present in said zone; and

a detector to detect light from the particles as an indicator of the presence or characteristics of the particles, wherein the apparatus comprises a pair of opposed concave reflective surfaces and the zone is between these surfaces,

wherein the method comprises alternately illuminating a said zone with different wavelength bandwidths of light to elicit different wavelengths of fluorescent radiation from any biological particles in said zone and monitoring for the different bandwidth wavelengths of fluorescence elicited and obtaining a ratio of the sensed signal for one wavelength or wavelength band of illuminating light relative to a corresponding signal for another wavelength or wavelength band of illuminating light as a means of facilitating characterising the identity of any biological particles within the zone.