Particle analysis system and method
First Claim
1. A method of particle analysis, comprising:
- (a) exposing a number of particles in suspension to an incident light with a predetermined time-varying intensity, the particles being sufficiently close to one another to multiply scatter light;
(b) detecting multiply scattered light from the particles in response to the incident light to determine a first value corresponding to an observed isotropic scattering coefficient of the particles;
(c) establishing an estimate corresponding to at least one of volume fraction or size distribution of the particles;
(d) calculating a second value from the estimate, the second value corresponding to a calculated isotropic scattering coefficient;
(e) comparing the first and second values to establish an error;
(f) changing the estimate;
(g) repeating said calculating, comparing, and changing until the error reaches a desired minimum and;
(h) controlling a process as a function of the estimate.
3 Assignments
0 Petitions
Accused Products
Abstract
A system (20) and method are disclosed for the self-calibrating, on-line determination of size distribution f(x) and volume fraction φ of a number of particles (P) dispersed in a medium (M) by detecting one or more propagation characteristics of multiply scattered light from the particles (P). The multiply scattered light is re-emitted in response to exposure to a light source (21) configured to provide light at selected wavelengths. The determination includes calculating the isotropic scattering and absorption coefficients for the particles (P) by comparing the incident and detected light to determine a measurement corresponding to the propagation time through the scattering medium (M), and iteratively estimating the size distribution f(x) and volume fraction φ as a function of the coefficients for each of the wavelengths. An estimation approach based on an expected form of the distribution and the mass of the particles is also disclosed. Furthermore, techniques to determine a particle structure factor indicative of particle-to-particle interactions which vary with particle concentration and influence light scattering at high concentrations is disclosed.
97 Citations
48 Claims
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1. A method of particle analysis, comprising:
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(a) exposing a number of particles in suspension to an incident light with a predetermined time-varying intensity, the particles being sufficiently close to one another to multiply scatter light; (b) detecting multiply scattered light from the particles in response to the incident light to determine a first value corresponding to an observed isotropic scattering coefficient of the particles; (c) establishing an estimate corresponding to at least one of volume fraction or size distribution of the particles; (d) calculating a second value from the estimate, the second value corresponding to a calculated isotropic scattering coefficient; (e) comparing the first and second values to establish an error; (f) changing the estimate; (g) repeating said calculating, comparing, and changing until the error reaches a desired minimum and; (h) controlling a process as a function of the estimate. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A system for analyzing a number of particles suspended in a medium in sufficient concentration to multiply scatter light comprising:
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a light source with a predetermined time-varying intensity configured to expose the medium to a number of different predetermined wavelengths of incident light; a first sensor spaced apart from said source, said first sensor being configured to provide a first detection signal corresponding to detected light, the detected light being multiply scattered by the particles; a processor responsive to the first detection signal and being configured to receive an exposure signal corresponding to said incident light, said processor being configured to generate;
(a) a number of comparison signals each corresponding to a difference with respect to time between the detected light and the incident light for a corresponding one of the wavelengths, (b) a number of scattering signals each correspondingly determined from the comparison signals and each corresponding to an observed isotropic scattering coefficient of the medium for a different one of the wavelengths, and (c) an output signal indicative of one of size distribution or volume fraction of the particles, said output signal being determined as a function of said scattering signals; andan output device responsive to said output signal to provide an output corresponding to the size distribution or volume fraction of the particles. - View Dependent Claims (8, 9, 10, 11, 12)
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13. A system for analyzing a number of particles suspended in a medium in sufficient concentration to multiply scatter light, comprising:
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(a) a light source with a predetermined time-varying intensity configured to expose the medium to a number of different wavelengths of light; (b) a sensor spaced apart from the source, said sensor being configured to provide a detected light signal corresponding to multiply scattered light from the particles at the different wavelengths in response to exposure to said source; (c) a processor responsive to said detected light signal, said processor including a calculation means for generating an output signal corresponding to at least one of particle size distribution or volume fraction in accordance with an observed isotropic scattering coefficient of the medium determined from said detected light signal, said calculation means including a means for iteratively determining a structure factor from an estimate corresponding to at least one of said particle size distribution or said volume fraction, said structure factor being representative of particle interactions that influence light scattering behavior of said particles; and (d) an output device responsive to said output signal to provide an output corresponding to at least one of said size distribution or said volume fraction. - View Dependent Claims (14, 15, 16, 17)
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18. A method of particle analysis, comprising:
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(a) exposing a medium with a number of suspended particles to a number of light wavelengths, the wavelengths each being intensity-modulated at a predetermined frequency; (b) detecting multiply scattered light from the medium in response to said exposing to characterize propagation of the multiply scattered light through the medium with a number of values, the values each corresponding to a different one of the wavelengths and each being representative of at least one of a phase or an amplitude of the multiply scattered light relative to the predetermined frequency; and (c) providing an output determined from the values, the output corresponding to at least one of a particle size distribution, particle volume fraction, or a particle interaction parameter, the particle interaction parameter corresponding to a nonlinear relationship between particle concentration and an isotropic scattering coefficient for the particles. - View Dependent Claims (19, 20, 21, 22, 23, 24)
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25. A method of particle analysis, comprising:
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(a) exposing a number of particles to a number of light wavelengths of predetermined time-varying intensity; (b) detecting multiply scattered light from the particles in response to said exposing to determine a number of values each corresponding to a different one of the wavelengths, the values each being representative of a time-of-flight characteristic of the particles; and (c) providing an output determined from the values, the output corresponding to at least one of a particle size distribution or volume fraction and being determined in accordance with a particle interaction parameter, the particle interaction parameter being representative of a nonlinear relationship between particle concentration and an isotropic scattering coefficient for the particles. - View Dependent Claims (26, 27, 28, 29, 30)
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31. A method of analysis, comprising:
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(a) exposing a fluid to an incident light, the fluid having a number of suspended particles therein, the suspended particles being sufficiently concentrated in the fluid to scatter light; (b) detecting multiply scattered light in response to said exposing to determine a time-based value characteristic of propagation time of the multiply scattered light through the fluid; (c) determining a quantity as a function of the value, the quantity corresponding to an isotropic scattering coefficient; and (d) providing an output corresponding to at least one of volume fraction, particle size distribution, or a particle interaction parameter, the particle interaction parameter corresponding to particle-to-particle interactions influencing light scattering behavior of the particles, said providing including calculating a number representative of the isotropic scattering coefficient as a function of an estimate corresponding to the volume fraction and the size distribution. - View Dependent Claims (32, 33, 34, 35, 36, 37, 38)
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39. A system for analyzing a number of particles suspended in a medium in sufficient concentration to multiply scatter light, comprising:
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a light source configured to expose the medium to a number of different predetermined wavelengths of incident light each having a predetermined time-varying intensity; a first sensor spaced apart from said source, said first sensor being configured to provide a first detection signal corresponding to detected light, the detected light being multiply scattered by the particles; a processor responsive to said first detection signal and being configured to receive an exposure signal corresponding to said incident light, said processor being configured to generate;
(a) a number of propagation signals by comparing said first detection signal and said exposure signal for each of said wavelengths, said propagation signals each characterizing time of flight of the detected light through the medium resulting from multiple scattering by the particles for a corresponding one of said wavelengths, (b) a number of scattering signals each corresponding to an isotropic scattering coefficient of the medium and being determined from a corresponding one of said propagation signals, and (c) an output signal indicative of at least one of size distribution or volume fraction of the particles, said output signal being determined from said scattering signals and a structure factor, said structure factor accounting for particle-to-particle interactions influencing light scattering behavior of the particles; andan output device responsive to said output signal to provide an output corresponding to said size distribution or said volume fraction of the particles. - View Dependent Claims (40, 41, 42, 43)
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44. A method of particle analysis, comprising:
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(a) exposing a number of particles to a number of light wavelengths of predetermined time-varying intensity; (b) detecting multiply scattered light from the particles in response to said exposing to determine a number of time-based propagation characteristics of the particles each corresponding to a different one of the wavelengths; and (c) calculating an observed isotropic scattering coefficient for each of the wavelengths from the characteristics; (d) determining a calculated isotropic scattering coefficient for each of the wavelengths from an estimate of at least one of particle size distribution or particle volume fraction; (e) comparing the observed isotropic scattering coefficient and calculated isotropic scattering coefficient for each of the wavelengths to establish and error; (f) adjusting the estimate and repeating said determining and said comparing until the error reaches a desired minimum; and (g) providing an output corresponding to at least one of the particle size distribution, particle volume fraction, or a particle interaction parameter. - View Dependent Claims (45, 46, 47, 48)
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Specification