US4338030A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Dispersive instrument for measurement of particle size distributions
Assignee: Individual
•
Filing: 1980-03-18
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Granted: 1982-07-06
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Expires: 2000-03-18
Abstract
Abstract A method for measurement of the size distribution of particles suspended in a gas or in a liquid. The particle suspension is illuminated by a collimated beam of substantially white light. Part of the light scattered by the particles is collected by a lens and is passed through a slit placed in the focal plane of the lens. The light transmitted by the slit is made to pass through a dispersive element which causes spectral decomposition of the processed light in a direction perpendicular to the slit. A spatial filter is placed in the exit plane of the dispersive element; the transmittance of this filter is a function of position on the filter. The light transmitted by the filter is measured by a photodetector. The photodetector output is measured as different spatial filters are switched in place. A computer, microprocessor, or analog device acts on the measured values and produces the particle size distribution as an output. The data reduction algorithm consists of a linear transformation of the measured data vector, followed by the construction of a linear combination of basis functions for the size distribution. One of the spatial filters has uniform transmittance for the purpose of background light subtraction, and to provide a bias in order to allow effectively indefinite filter transmittance functions.
Inventors
- 👤 Hendricus G. Loos
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 19:29
CPC Classifications
G; G01; G01N; G01N15/00; G01N15/02; G01N15/0205; G01N15/0211
Claims Analysis
Total Claims: 50
Claim 1
Independent Claim
194 words
A method for measurement of the size distribution of particles suspended in a gas or a liquid, comprising: passing into the particle suspension an illuminating beam comprising a substantially collimated beam of substantially white light; with a lens collecting part of the light scattered by the particles; passing the collected light through a slit in an opaque screen located in the focal plane of said lens; passing the light transmitted by said slit through a dispersive element such as to produce, in the exit plane of the dispersive element, a spectral decomposition in a direction perpendicular to said slit, and such that a monochromatic point source in said slit produces a sharp image in said exit plane; sequentially placing the members of a set of spatial filters in an image window located in said exit plane; collecting the light transmitted by each of said spatial filters sequentially by a photodetector to produce a signal substantially proportional to light transmitted by respective filters; acting on the resulting photodetector signal sequence by a linear transformation; and using the resulting data sequence a coefficients in a linear combination of basis functions to yield the particle size distribution.
Claim 2
Independent Claim
194 words
A method for measurement of the size distribution of particles suspended in a gas or a liquid, comprising: passing into the particle suspension an illuminating beam comprising a substantially collimated beam of substantially white light; with a lens collecting part of the light scattered by the particles; passing the collected light through a slit in an opaque screen located in the focal plane of said lens; passing the light transmitted by said slit through a dispersive element such as to produce, in the exit plane of the dispersive element, a spectral decomposition in a direction perpendicular to said slit, and such that a monochromatic point source in said slit produces a sharp image in said exit plane; sequentially placing the members of a set of spatial filters in an image window located in said exit plane; collecting the light transmitted by each of said spatial filters sequentially by a photodetector to produce a signal substantially proportional to light transmitted by respective filters; acting on the resulting photodetector signal sequence by a linear transformation; and using the resulting data sequence a coefficients in a linear combination of basis functions to yield the particle size distribution.
Claim 3
Dependent Claim
49 words
A method according to claim 1 in which the spatial filters have a non-uniform transmittance which at any point P of the filters is a function of λ and θ, where λ is the wavelength at P and θ is the scattering angle of rays that pass through P.
Claim 4
Dependent Claim
19 words
A method according to claim 1 in which one of the filters of the set has a uniform transmittance.
Claim 5
Dependent Claim
64 words
A method according to claim 3 in which the said acting by a linear transformation step comprises an optical process, and is followed by a step of subtracting the scaled photodetector signal for the uniform filter from the scaled signals for the non-uniform filters, followed by the step of using using the resulting data sequence as coefficients in a linear combination of basis functions.
Claim 6
Dependent Claim
19 words
A method according to claim 3 in which said uniform transmittance filter is used for subtraction of background light.
Claim 7
Dependent Claim
36 words
A method according to claim 1 in which said set of spatial filters moves continuously, and the light source is flashed when a member of the set of spatial filters is aligned with said image window.
Claim 8
Dependent Claim
17 words
A method according to claim 6 in which synchronous detection is used to process the photodetector signal.
Claim 9
Dependent Claim
21 words
A method according to claim 1 in which a polarizing element is placed in the path of the said scattered light.
Claim 10
Dependent Claim
48 words
A method according to claim 8 in which spatial filters have a non-uniform transmittance which at any point P of the filter is a function of λ and θ, where λ is the wavelength at P and θ is the scattering angle of rays that pass through P.
Claim 11
Dependent Claim
22 words
A method according to claim 8 in which one of the filters of the set of spatial filters has a uniform transmittance.
Claim 12
Dependent Claim
63 words
A method according to claim 10 in which the said acting by a linear transformation step comprises an optical process, and is followed by a step of subtracting the scaled photodetector signal for the uniform filter from the scaled signals for the non-uniform filters, followed by the step of using the resulting date sequence as coefficients in a linear combination of basis functions.
Claim 13
Dependent Claim
19 words
A method according to claim 10 in which said uniform transmittance filter is used for subtraction of background light.
Claim 14
Dependent Claim
36 words
A method according to claim 8 in which said set of spatial filters moves continuously, and the light source is flashed when a member of the set of spatial filters is aligned with said image window.
Claim 15
Dependent Claim
17 words
A method according to claim 13 in which synchronous detection is used to process the photodetector signal.
Claim 16
Dependent Claim
17 words
A method according to claim 8 in which a light chopper is placed in the illuminating beam.
Claim 17
Dependent Claim
17 words
A method according to claim 15 in which synchronous detection is used to process the photodetector signal.
Claim 18
Dependent Claim
17 words
A method according to claim 1 in which a light chopper is placed in the illuminating beam.
Claim 19
Dependent Claim
17 words
A method according to claim 17 in which synchronous detection is used to process the photodetector signal.
Claim 20
Dependent Claim
14 words
A method according to claim 1 in which said substantially collimated beam is polarized.
Claim 21
Dependent Claim
47 words
A method according to claim 19 in which the spatial filters have a non-uniform transmittance which at any point P of the filter is a function of λ and θ, where λ is the wavelength and θ is the scattering angle of rays that pass through P.
Claim 22
Dependent Claim
19 words
A method according to claim 19 in which one of the filters of the set has a uniform transmittance.
Claim 23
Dependent Claim
62 words
A method according to claim 21 in which the said acting by a linear transformation step comprises an optical process, and is followed by a step of subtracting the scaled photodetector signal for the uniform filter from the scaled signals for the non-uniform filters, followed the step of using the resulting data sequence as coefficients in a linear combination of basis functions.
Claim 24
Dependent Claim
19 words
A method according to claim 21 in which said uniform transmittance filter is used for subtraction of background light.
Claim 25
Dependent Claim
36 words
A method according to claim 19 in which said set of spatial filters moves continuously, and the light source is flashed when a member of the set of spatial filters is aligned with said image window.
Claim 26
Dependent Claim
17 words
A method according to claim 24 in which synchronous detection is used to process the photodetector signal.
Claim 27
Dependent Claim
17 words
A method according to claim 19 in which a light chopper is placed in the illuminating beam.
Claim 28
Dependent Claim
17 words
A method according to claim 26 in which synchronous detection is used to process the photodetector signal.
Claim 29
Dependent Claim
187 words
Apparatus for measurement of the size distribution of particles suspended in a gas or liquid comprising: a source of substantially collimated beam of substantially white light, which illuminates the particle suspension; a lens for collecting part of the light scattered by the particles; an opaque screen with a slit, said screen being located in the focal plane of said lens; a dispersive element through which the light transmitted by said slit is passed, and which in its exit plane produces a spectrally decomposed image of said slit, the spectral decomposition encompassing the dimension of the exit plane perpendicular to the slit; a set comprising a plurality of spatial filters; means to present filters of said set sequentially in an image window located in said exit plane of the dispersive element; a photodetector to produce a sequence of signals each of which is substantially proportional to light transmitted by a respective filter; means for acting on the resulting photodetector signal sequence by a linear transformation; and means for using the resulting data sequence as coefficients in a linear combination of basis functions to yield the particle size distribution.
Claim 30
Dependent Claim
187 words
Apparatus for measurement of the size distribution of particles suspended in a gas or liquid comprising: a source of substantially collimated beam of substantially white light, which illuminates the particle suspension; a lens for collecting part of the light scattered by the particles; an opaque screen with a slit, said screen being located in the focal plane of said lens; a dispersive element through which the light transmitted by said slit is passed, and which in its exit plane produces a spectrally decomposed image of said slit, the spectral decomposition encompassing the dimension of the exit plane perpendicular to the slit; a set comprising a plurality of spatial filters; means to present filters of said set sequentially in an image window located in said exit plane of the dispersive element; a photodetector to produce a sequence of signals each of which is substantially proportional to light transmitted by a respective filter; means for acting on the resulting photodetector signal sequence by a linear transformation; and means for using the resulting data sequence as coefficients in a linear combination of basis functions to yield the particle size distribution.
Claim 31
Dependent Claim
15 words
Apparatus according to claim 28 in which the filters are mounted on a rotatable disc.
Claim 32
Dependent Claim
15 words
Apparatus according to claim 28 in which the filters are comprised of a film strip.
Claim 33
Dependent Claim
48 words
Apparatus according to claim 28 in which the filters comprise transparencies which have a non-uniform transmittance which at any point P of the filter is a function of λ and θ, where λ is the wavelength and θ is the scattering angle of rays that pass through P.
Claim 34
Dependent Claim
21 words
Apparatus according to claim 28 in which polarizing means is placed in the path of the beam provided by said source.
Claim 35
Dependent Claim
24 words
Apparatus according to claim 28 in which chopper means, synchronized with the spatial filter set, intermittently impedes the passage of light into the suspension.
Claim 36
Dependent Claim
18 words
Apparatus according to claim 33 in which means for synchronous detection is used to process the photodetector signal.
Claim 37
Dependent Claim
16 words
Apparatus according to claim 28 in which means is provided for flashing said light source intermittently.
Claim 38
Dependent Claim
17 words
Apparatus according to claim 35 in which means for synchronous detection is used for the photodetector signal.
Claim 39
Dependent Claim
21 words
Apparatus according to claim 28 in which polarizing means is placed on the axis of said lens, ahead of said filters.
Claim 40
Dependent Claim
216 words
Apparatus for measurement of the size distribution of particles suspended in a gas or liquid comprising: a source of substantially collimated beam of substantially white light, which illuminates the particle suspension; a lens for collecting part of the light scattered by the particles; an opaque screen with a slit, said screen being located in the focal plane of said lens; a dispersive element consisting of an entrance lens, a set of η prisms, η≧1, and an exit lens, such that the said opaque screen is in the focal plane of the entrance lens, the light transmitted by the slit and the entrance lens traverses the said set of prisms as well as the exit lens, and the prism generators are substantially parallel to the said slit; an image window located in the rear focal plane of said exit lens; a set comprising a plurality of spatial filters; means to present filters of said set sequentially in said image window; a photodetector to produce a sequence of signals each of which is substantially proportional to light transmitted by a respective filter; means for acting on the resulting photodetector signal sequence by a linear transformation; and means for using the resulting data sequence as coefficients in a linear combination of basis functions to yield the particle size distribution.
Claim 41
Dependent Claim
216 words
Apparatus for measurement of the size distribution of particles suspended in a gas or liquid comprising: a source of substantially collimated beam of substantially white light, which illuminates the particle suspension; a lens for collecting part of the light scattered by the particles; an opaque screen with a slit, said screen being located in the focal plane of said lens; a dispersive element consisting of an entrance lens, a set of η prisms, η≧1, and an exit lens, such that the said opaque screen is in the focal plane of the entrance lens, the light transmitted by the slit and the entrance lens traverses the said set of prisms as well as the exit lens, and the prism generators are substantially parallel to the said slit; an image window located in the rear focal plane of said exit lens; a set comprising a plurality of spatial filters; means to present filters of said set sequentially in said image window; a photodetector to produce a sequence of signals each of which is substantially proportional to light transmitted by a respective filter; means for acting on the resulting photodetector signal sequence by a linear transformation; and means for using the resulting data sequence as coefficients in a linear combination of basis functions to yield the particle size distribution.
Claim 42
Dependent Claim
15 words
Apparatus according to claim 38 in which the filters are mounted on a rotatable disc.
Claim 43
Dependent Claim
12 words
Apparatus according to claim 38 in which the filters comprise a filmstrip.
Claim 44
Dependent Claim
48 words
Apparatus according to claim 38 in which the filters comprise transparencies which have a non-uniform transmittance, which at any point P of the filters is a function of λ and θ, where λ is the wavelength and θ is the scattering angle of rays that pass through P.
Claim 45
Dependent Claim
21 words
Apparatus according to claim 38 in which polarizing means is placed in the path of the beam provided by said source.
Claim 46
Dependent Claim
24 words
Apparatus according to claim 38 in which chopper means, synchronized with the spatial filter set, intermittently impedes the passage of light into the suspension.
Claim 47
Dependent Claim
18 words
Apparatus according to claim 43 in which means for synchronous detection is used to process the photomultiplier signal.
Claim 48
Dependent Claim
16 words
Apparatus according to claim 38 in which means is provided for flashing said light source intermittently.
Claim 49
Dependent Claim
18 words
Apparatus according to claim 45 in which means for synchronous detection is used to process the photodetector signal.
Claim 50
Dependent Claim
21 words
Apparatus according to claim 38 in which polarizing means is placed on the axis of said lens, ahead of said filters.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1985-07-05 | 1986-01-04 | 1986-07-06 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1989-07-05 | 1990-01-04 | 1990-07-06 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1993-07-05 | 1994-01-04 | 1994-07-06 | $7700.00 | Window Closed / Lapsed |