EP0426341A2
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Particle size and velocity determination
Assignee: United Kingdom Atomic Energy Authority
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Filing: 1990-10-19
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Granted: —
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Expires: 2010-10-19
Abstract
Abstract A laser Doppler anemometry apparatus comprises means (12,14,16,20) to create two coherent light beams which intersect to define a probe volume (18), and at least two sensors to detect light scattered in different directions by a particle traversing the probe volume. The light beams are orthogonally polarized; and each sensor comprises a beam splitter (30) arranged to split the scattered light into two orthogonally plane polarized components at 45° and 135°, and two photo-detectors (34) to detect these components. For a pair of photo-detectors the pedestal signals are the same but the Doppler signals are of opposite phase; the detected signals are added (to give the pedestal) and are subtracted (to give the Doppler). The Doppler frequency indicates particle velocity, while the phase difference between Doppler signals at the two sensors indicates particle size. The pedestal signals may be utilized as trigger signals.
Inventors
- 👤 Robert Frew Gillespie
- 👤 Stefan Richard Martin
- 👤 Graham Robin Wallace-Sims
- 👤 David John Hemsley
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-04 13:12
CPC Classifications
G; G01; G01P; G01P5/00; G01P5/26; G01N; G01N15/00; G01N15/02; G01N15/0205; G01N2015/0007; G01N2015/0011; G01N2015/0023; G01N2015/0026; G01N2015/0042; G01N2015/0053; G01N2015/0238; G01N21/00; G01N21/17; G01N21/47; G01N2021/4792
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
173 words
An apparatus (10) for monitoring discrete particles, the apparatus comprising means (12, 16) for generating two coherent light beams of the same wavelength, and means (20) to cause the light beams to intersect and so to define a probe volume (18), and at least one sensor arranged to receive light scattered by a particle in the probe volume, characterised by each sensor comprising means (30) to split the scattered light into two differently polarized components and two detectors (34) arranged to receive the two components and to generate two corresponding electrical signals, the polarization of the intersecting light beams and of the received components being arranged such that the Doppler signals in the two components are 180° out of phase, and means (38) to generate a first output signal corresponding to the difference between the two electrical signals, and the apparatus also comprising means (46, 48) responsive to the first signals from the sensor (30, 34, 38), or from two of the sensors (30, 34, 38), to determine the size of the particle.
Claim 2
Independent Claim
173 words
An apparatus (10) for monitoring discrete particles, the apparatus comprising means (12, 16) for generating two coherent light beams of the same wavelength, and means (20) to cause the light beams to intersect and so to define a probe volume (18), and at least one sensor arranged to receive light scattered by a particle in the probe volume, characterised by each sensor comprising means (30) to split the scattered light into two differently polarized components and two detectors (34) arranged to receive the two components and to generate two corresponding electrical signals, the polarization of the intersecting light beams and of the received components being arranged such that the Doppler signals in the two components are 180° out of phase, and means (38) to generate a first output signal corresponding to the difference between the two electrical signals, and the apparatus also comprising means (46, 48) responsive to the first signals from the sensor (30, 34, 38), or from two of the sensors (30, 34, 38), to determine the size of the particle.
Claim 3
Dependent Claim
27 words
An apparatus as claimed in Claim 1 also comprising means (42, 44) to determine from the frequency of the first output signal the velocity of the particle.
Claim 4
Dependent Claim
55 words
An apparatus as claimed in Claim 1 or Claim 2 wherein at least one sensor also comprises means (36) to generate a second output signal corresponding to the sum of the two electrical signals, and the size-determining means determines the particle size from the ratio of the first output signal to the second output signal.
Claim 5
Dependent Claim
54 words
An apparatus as claimed in Claim 1 or Claim 2 wherein the apparatus comprises at least two sensors (30, 34, 38) arranged to receive light scattered in different directions by a particle, and the size-determining means (46, 48) determines the particle size from the phase difference between the first output signals from two sensors.
Claim 6
Dependent Claim
54 words
An apparatus as claimed in Claim 4 wherein at least one sensor (30, 34, 38) also comprises means (36) to generate a second output signal corresponding to the sum of the two electrical signals, and the apparatus is arranged such that the size-determining means (46, 48) operates in response to the second output signal.
Claim 7
Dependent Claim
31 words
An apparatus as claimed in Claim 5 with Claim 4 dependent upon Claim 2, wherein the velocity-determining means (42, 44) is arranged to operate in response to the second output signal.
Claim 8
Independent Claim
36 words
An apparatus as claimed in any one of Claims 4 to 6 wherein the apparatus comprises three sensors (30, 34, 38) whereby ambiguities in particle size due to phase differences in excess of 360° are eliminated.
Claim 9
Independent Claim
46 words
An apparatus as claimed in any one of the preceding Claims wherein the two intersecting light beams are plane polarized in orthogonal directions, and the received components are plane polarized in orthogonal directions mid-way between the directions of the planes of polarization of the intersecting beams.
Claim 10
Dependent Claim
182 words
A sensor unit for use in an apparatus for monitoring discrete particles, the apparatus comprising means (12, 16) for generating two coherent light beams of the same wavelength, and means (20) to cause the light beams to intersect and so to define a probe volume (18), the sensor unit comprising at least one sensor arranged to receive light scattered by a particle in the probe volume, characterised by each sensor comprising means (30) to split the scattered light into two differently polarized components and two detectors (34) arranged to receive the two components and to generate two corresponding electrical signals, the polarization of the intersecting light beams and of the received components being arranged such that the Doppler signals in the two components are 180° out of phase, and means (38) to generate a first output signal corresponding to the difference between the two electrical signals, and the unit also comprising means (46, 48) responsive to the first output signals from the sensor (30, 34, 38), or from two of the sensors (30, 34, 38), to determine the size of the particle.
Claim 11
Dependent Claim
182 words
A sensor unit for use in an apparatus for monitoring discrete particles, the apparatus comprising means (12, 16) for generating two coherent light beams of the same wavelength, and means (20) to cause the light beams to intersect and so to define a probe volume (18), the sensor unit comprising at least one sensor arranged to receive light scattered by a particle in the probe volume, characterised by each sensor comprising means (30) to split the scattered light into two differently polarized components and two detectors (34) arranged to receive the two components and to generate two corresponding electrical signals, the polarization of the intersecting light beams and of the received components being arranged such that the Doppler signals in the two components are 180° out of phase, and means (38) to generate a first output signal corresponding to the difference between the two electrical signals, and the unit also comprising means (46, 48) responsive to the first output signals from the sensor (30, 34, 38), or from two of the sensors (30, 34, 38), to determine the size of the particle.
Claim 12
Independent Claim
134 words
A method of monitoring discrete particles, the method comprising generating two coherent light beams of the same wavelength, causing the light beams to intersect and so to define a probe volume (18), and arranging at least one sensor to receive light scattered by a particle in the probe volume, at each sensor (30, 34) splitting the scattered light into two differently polarized components and generating two corresponding electrical signals, the polarization of the intersecting light beams and of the two components being arranged such that the Doppler signals in the two components are 180° out of phase, and generating a first output signal (38) corresponding to the difference between the two electrical signals, and determining the size of the particle from the first output signals from the sensor or from two of the sensors.
Claim 13
Independent Claim
134 words
A method of monitoring discrete particles, the method comprising generating two coherent light beams of the same wavelength, causing the light beams to intersect and so to define a probe volume (18), and arranging at least one sensor to receive light scattered by a particle in the probe volume, at each sensor (30, 34) splitting the scattered light into two differently polarized components and generating two corresponding electrical signals, the polarization of the intersecting light beams and of the two components being arranged such that the Doppler signals in the two components are 180° out of phase, and generating a first output signal (38) corresponding to the difference between the two electrical signals, and determining the size of the particle from the first output signals from the sensor or from two of the sensors.
Claim 14
Dependent Claim
50 words
A method as claimed in Claim 10 also comprising generating a second output signal corresponding to the sum of the two electrical signals, and either using the second output signal in determining the particle size, or using the second output signal to control the operation of determining the particle size.
References Cited (Backward Citations)
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