Two-dimensional optical imaging methods and systems for particle detection

• US 8,154,724 B2
• Filed: 12/02/2008
• Issued: 04/10/2012
• Est. Priority Date: 12/04/2007
• Status: Active Grant

• Current Assignee: Particle Measuring Systems Incorporated (Spectris PLC)
• Original Assignee: Particle Measuring Systems Incorporated (Spectris PLC)
• Inventors: Mitchell, John, Sehler, Dwight A., Williamson, Michael, Rice, David, Sandberg, Jon
• Primary Examiner(s): Chowdhury, Tarifur
• Assistant Examiner(s): Pajoohi, Tara S
• Application Number:
  US12/326,577
• Publication Number:
  US 20090244536A1
• Time in Patent Office: 1,225 Days
• Field of Search: 3562431-2438, 356337-343
• US Class Current: 356/343
• CPC Class Codes: G01N 15/1433 using image recognition
• CPC Class Codes: G01N 15/1459 the analysis being performed on a sample stream
• CPC Class Codes: G01N 2015/0038 Investigating nanoparticles
• CPC Class Codes: G01N 2015/025 Methods for single or grouped particles
• CPC Class Codes: G01N 2015/1402 Data analysis by thresholding or gating operations performed on the acquired signals or stored data

Abstract

The present invention provides methods and systems for particle detection and analysis using two-dimensional optical imaging to access enhanced detection sensitivity and expanded sensing functionality relative to conventional point and array detection-based optical particle counters. Methods and systems of the present invention provide a two-dimensional optical imaging-based particle sensing platform wherein system components and specifications are selected to generate reproducible and readily identifiable signals, including particle detection signatures, from optical scattering or emission from particles provided to the system. Systems and methods of the present invention are capable of accurately and sensitively detecting, identifying, and characterizing (e.g., determining the size of) particles in liquid phase or gas phase samples.

Claims

1. A method for detecting a single particle in a fluid flow, said method comprising the steps:

providing said fluid flow having said particle, said flow having a flow direction;

exposing said fluid flow to a beam of electromagnetic radiation, wherein interaction between said single particle and said beam of electromagnetic radiation generates scattered or emitted electromagnetic radiation from said single particle;

directing at least a portion of said scattered or emitted electromagnetic radiation from said single particle onto a plurality of detector elements provided in an array of a two-dimensional detector;

detecting at least a portion of said scattered or emitted electromagnetic radiation directed onto said plurality of detector elements, wherein at least a portion of said detector elements of said array generate output signals corresponding to intensities of said scattered or emitted electromagnetic radiation from said single particle;

measuring output signals for at least a portion of said detector elements of said array;

identifying a particle detection signature for said single particle comprising a pattern of a plurality of output signals of detector elements each having an output signal greater than or equal to a threshold value for a given detector element;

wherein the threshold value for each detector element of said particle detection signature is greater than or equal to 2.5 times a standard deviation of noise for that detector element;

wherein said particle detection signature comprises a longitudinal component corresponding to a distribution of intensities of said scattered or emitted electromagnetic radiation along said flow direction;

said longitudinal component comprising 2 or more directly neighboring detector elements provided along a longitudinal axis corresponding to said flow direction; and

analyzing the particle detection signature to provide an indication or measurement of a characteristic of the particle, thereby detecting said single particle in said fluid flow.

2. The method of claim 1 wherein said particle detection signature comprises a pattern of output signals from between 2 and 20 neighboring or directly neighboring detector elements of said array.

3. The method of claim 1 wherein said particle detection signature comprises a pattern of output signals of between 2 and 7 neighboring or directly neighboring detector elements of said array.

4. The method of claim 1 wherein the threshold values vary for different detector elements in said array.

5. The method of claim 1 wherein said threshold value for a given detector element is equal to or greater than 3 times the standard deviation of the noise of the given detector element of said array or is equal to or greater than 3 times the standard deviation of output values of the given detector element of said array in the absence of electromagnetic radiation scattered or emitted from said particle.

6. The method of claim 1 wherein said threshold value for a given detector element is equal to 2.5 to 7 times the standard deviation of the noise of the given detector element of said array or is equal to 2.5 to 7 times the standard deviation of output values of the given detector element in the array in the absence of electromagnetic radiation scattered or emitted from said particle.

7. The method of claim 1 wherein each of said output signals has a background value subtracted for a given detector element.

8. The method of claim 1 wherein said pattern of output signals of said particle detection signature has an elongated shape.

9. The method of claim 1 wherein said longitudinal component comprises output signals from between 2 and 20 directly neighboring detector elements.

10. The method of claim 1 wherein said particle detection signature further comprises a lateral component corresponding to a distribution of intensities of said scattered or emitted electromagnetic radiation along an axis orthogonal to said flow direction.

11. The method of claim 10 wherein said lateral component comprises output signals from between 2 and 10 directly neighboring detector elements along an axis orthogonal to said longitudinal axis.

12. The method of claim 1 further comprising the step of imaging said scattered or emitted electromagnetic radiation onto said detector elements of said array.

13. The method of claim 1 further comprising identifying positions in said array of said detected elements providing said output signals of said particle detection signature.

14. An optical particle analyzer comprising:

an optical source for generating a beam of electromagnetic radiation;

a flow chamber for flowing a fluid containing particles along a flow direction and through the beam of electromagnetic radiation, thereby generating scattered or emitted electromagnetic radiation from a single particle in said fluid;

an optical collection system for collecting and directing at least a portion of the scattered or emitted electromagnetic radiation from said single particle onto a plurality of detector elements of an array of a two-dimensional detector, wherein at least a portion of the detector elements of the array generate output signals corresponding to intensities of the scattered or emitted electromagnetic radiation; and

a processor operationally connected to the two-dimensional detector capable of identifying and analyzing a particle detection signature for said single particle comprising a pattern of a plurality of output signals of detector elements each having an output signal greater than or equal to a threshold value for a given detector element;

wherein the threshold value for each detector element of said particle detection signature is greater than or equal to 2.5 times a standard deviation of noise for that detector element;

wherein said particle detection signature comprises a longitudinal component corresponding to a distribution of intensities of said scattered or emitted electromagnetic radiation along said flow direction;

said longitudinal component comprising 2 or more directly neighboring detector elements provided along a longitudinal axis corresponding to said flow direction.

15. The optical particle analyzer of claim 14 wherein said processor is also capable of analyzing a shape of the particle detection signature and/or intensities of the output signals of the detector elements having an output signal greater than or equal to a threshold value for a given detector element, so as to determine a size of the particle.

16. A method of distinguishing a single particle scattering event from other electromagnetic radiation generation or detection processes in an optical particle analyzer, said method comprising the steps of:

providing a fluid flow having said particle to said optical particle analyzer, said fluid flow having a flow direction;

exposing said fluid flow to a beam of electromagnetic radiation, wherein interaction between said single particle and said beam generates scattered or emitted electromagnetic radiation from said single particle;

directing at least a portion of said scattered or emitted electromagnetic radiation onto a plurality of detector elements provided in an array of a two-dimensional detector of said optical particle analyzer;

detecting at least a portion of said scattered or emitted electromagnetic radiation directed onto said plurality of detector elements, wherein at least a portion of said detector elements of said array generate output signals corresponding to intensities of said scattered or emitted electromagnetic radiation from said single particle;

measuring output signals for at least a portion of said detector elements of said array; and

sensing a particle detection event upon identification of a particle detection signature for said single particle comprising a pattern of a plurality of output signals of detector elements each having an output signal greater than or equal to a threshold value for a given detector element;

wherein the threshold value for each detector element of said particle detection signature is greater than or equal to 2.5 times a standard deviation of noise for that detector element;

wherein said particle detection signature comprises a longitudinal component corresponding to a distribution of intensities of said scattered or emitted electromagnetic radiation along said flow direction;

said longitudinal component comprising 2 or more directly neighboring detector elements provided along a longitudinal axis corresponding to said flow direction;

thereby distinguishing said single particle scattering event from other electromagnetic radiation generation or detection processes in said optical particle analyzer.

17. A method for detecting a single particle in a fluid flow, said method comprising the steps:

providing said fluid flow having said single particle, said fluid flow having a flow direction;

exposing said fluid flow to a beam of electromagnetic radiation, wherein interaction between said single particle and said beam generates scattered or emitted electromagnetic radiation from said single particle;

directing at least a portion of said scattered or emitted electromagnetic radiation onto a plurality of detector elements provided in an array of a two-dimensional detector;

detecting at least a portion of said scattered or emitted electromagnetic radiation, wherein at least a portion of said detector elements of said array generate output signals corresponding to intensities of said scattered or emitted electromagnetic radiation from said single particle;

measuring output signals for at least a portion of said detector elements of said array;

identifying a particle detection signature for said single particle comprising a pattern of a plurality of output signals of detector elements each having an output signal greater than or equal to a threshold value for a given detector element;

wherein the threshold value for each detector element of said particle detection signature is greater than or equal to 2.5 times a standard deviation of noise for that detector element;

wherein said particle detection signature comprises a longitudinal component corresponding to a distribution of intensities of said scattered or emitted electromagnetic radiation along said flow direction;

said longitudinal component comprising 2 or more directly neighboring detector elements provided along a longitudinal axis corresponding to said flow direction;

determining a subset of said detector elements of said array, said subset comprising a plurality of detector elements receiving scattered or emitted electromagnetic radiation from said single particle, wherein each detector element of said subset has an output signal greater than or equal to said threshold value for a given detector element;

transmitting to a processor only the output signals of said subset; and

analyzing the output signals transmitted to said processor, thereby detecting said single particle.

18. The method of claim 17 wherein said subset further comprises from 0 to 10 detector elements neighboring or directly neighboring each of the detector elements having an output signal greater than or equal to a threshold value for a given detector element.

19. The method of claim 17 wherein said subset comprises 2 to 10 detector elements of said array.

20. The method of claim 17 wherein each of said output signals has a background value subtracted for a given detector element in said array;

wherein each of said background values correspond to an average output signal for a given detector element in said array for detection conditions in the absence of electromagnetic radiation scattered or emitted by said particle.

21. A method for detecting a single particle in a fluid flow, said method comprising the steps:

providing said fluid flow having said single particle, said fluid flow having a flow direction;

exposing said fluid flow to a beam of electromagnetic radiation, wherein interaction between said single particle and said beam generates scattered or emitted electromagnetic radiation from said single particle;

directing at least a portion of said scattered or emitted electromagnetic radiation onto a plurality of detector elements provided in an array of a two-dimensional detector;

detecting at least a portion of the scattered or emitted electromagnetic radiation directed onto said plurality of detector elements, wherein at least a portion of said detector elements of said array generate output signals corresponding to intensities of said scattered or emitted electromagnetic radiation from said single particle;

measuring output signals for at least a portion of said detector elements of said array;

identifying a particle detection signature for said single particle comprising a pattern of a plurality of output signals of detector elements each having an output signal greater than or equal to a threshold value for a given detector element;

wherein the threshold value for each detector element of said particle detection signature is greater than or equal to 2.5 times a standard deviation of noise for that detector element;

wherein said particle detection signature comprises a longitudinal component corresponding to a distribution of intensities of said scattered or emitted electromagnetic radiation along said flow direction;

said longitudinal component comprising 2 or more directly neighboring detector elements provided along a longitudinal axis corresponding to said flow direction;

generating a plurality of detection frames, wherein each detection frame comprises a plurality of said output signals of said detector elements for a given time interval;

combining a plurality of detection frames having output signals corresponding to detected intensities of said scattered or emitted electromagnetic radiation to generate a composite image of a particle detection event for said single particle;

analyzing said composite image, thereby detecting said single particle.

22. The method of claim 21 further comprising identifying detection frames having output signals corresponding to detected intensities of electromagnetic radiation scattered or emitted by said particle.

23. The method of claim 21 wherein said detection frames are generated at a rate of 0.1 kHz to 20 kHz.

24. The method of claim 21 wherein each detection frame corresponds to a time interval of 50 μ

s to 10 ms.

25. The method of claim 21 wherein 1 to 100 detection frames are combined to generate the composite image.

26. The method of claim 21 further comprising the step of subtracting a reference frame from each of said detection frames;

wherein the reference frame comprises background output signals for the detector elements in said array;

wherein each background output signal is an average output signal for a given detector element in said array for detection conditions in the absence of electromagnetic radiation scattered or emitted by said particle.

27. The method of claim 26 wherein the reference frame is continuously updated.

28. A method for detecting a single particle in a fluid flow, said method comprising the steps:

providing said fluid flow having said single particle, said fluid flow having a flow direction;

exposing said fluid flow to a beam of electromagnetic radiation, wherein interaction between said single particle and said beam generates scattered or emitted electromagnetic radiation from said single particle;

directing at least a portion of said scattered or emitted electromagnetic radiation onto a plurality of detector elements provided in an array of a two-dimensional detector;

detecting at least a portion of said scattered or emitted electromagnetic radiation directed onto said plurality of detector elements, wherein at least a portion of said detector elements of said array generate output signals corresponding to intensities of said scattered or emitted electromagnetic radiation from said single particle;

measuring output signals for at least a portion of said detector elements of said array;

identifying a particle detection signature for said single particle comprising a pattern of a plurality of output signals of detector elements each having an output signal greater than or equal to a threshold value for a given detector element;

wherein the threshold value for each detector element of said particle detection signature is greater than or equal to 2.5 times a standard deviation of noise for that detector element;

wherein said particle detection signature comprises a longitudinal component corresponding to a distribution of intensities of said scattered or emitted electromagnetic radiation along said flow direction;

said longitudinal component comprising 2 or more directly neighboring detector elements provided along a longitudinal axis corresponding to said flow direction;

detecting at least a portion of said scattered or emitted electromagnetic radiation using a sub-array of said two-dimensional detector, wherein at least a portion of said detector elements of said sub-array generate output signals corresponding to intensities of said scattered or emitted electromagnetic radiation from said single particle;

transmitting to a processor only output signals of said detector elements corresponding to said sub-array or a portion thereof; and

analyzing the output signals transmitted to said processor, thereby detecting said single particle.

29. The method of claim 28 wherein the sub-array comprises 0.2% to 25% of the detector elements of the two-dimensional detector.

30. The method of claim 28 wherein the sub-array comprises 1000 to 100000 detection elements.

31. The method of claim 28 wherein the two-dimensional detector is a CMOS detector having 400000 to 1300000 detection elements.

32. A method for detecting a single particle in a fluid flow, said method comprising the steps:

providing said fluid flow having said single particle, said fluid flow having a flow direction;

exposing said fluid flow to a beam of electromagnetic radiation, wherein interaction between said single particle and said beam generates scattered or emitted electromagnetic radiation from said single particle;

directing at least a portion of said scattered or emitted electromagnetic radiation onto a plurality of detector elements provided in an array of a two-dimensional detector;

detecting at least a portion of said scattered or emitted electromagnetic radiation directed onto said plurality of detector elements, wherein at least a portion of said detector elements of said array generate output signals corresponding to intensities of said scattered or emitted electromagnetic radiation from said single particle;

measuring output signals for at least a portion of said detector elements of said array;

identifying a particle detection signature for said single particle comprising a pattern of a plurality of output signals of detector elements each having an output signal greater than or equal to a threshold value for a given detector element;

wherein the threshold value for each detector element of said particle detection signature is greater than or equal to 2.5 times a standard deviation of noise for that detector element;

wherein said particle detection signature comprises a longitudinal component corresponding to a distribution of intensities of said scattered or emitted electromagnetic radiation along said flow direction;

said longitudinal component comprising 2 or more directly neighboring detector elements provided along a longitudinal axis corresponding to said flow direction;

detecting at least a portion of said scattered or emitted electromagnetic radiation using a sub-array of said two-dimensional detector, wherein at least a portion of said detector elements of said sub-array generate output signals corresponding to intensities of said scattered or emitted electromagnetic radiation;

determining a subset of said detector elements of said sub-array, said subset comprising a plurality of detector elements, wherein each detector element of said subset has an output signal greater than or equal to said threshold value for a given detector element;

transmitting to a processor only the output signals of said subset; and

analyzing the output signals transmitted to said processor, thereby detecting said single particle.

33. The method of claim 32 wherein said determining step comprises analyzing the output signals of the sub-array;

and identifying detector elements of the sub-array having an output signal greater than the threshold value for a given detector element.

34. The method of claim 32 wherein said subset further comprises from 0 to 100 detector elements neighboring or directly neighboring each of the detector elements having an output signal greater than or equal to a threshold value for a given detector element.