EP0289200A2
Expired / Lapsed
EP
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Apparatus and method for particle analysis
Assignee: Laser Sensor Tech Inc
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Filing: 1988-04-20
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Granted: —
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Expires: 2008-04-20
Abstract
Abstract Apparatus for analyzing particles contained in a fluent medium (12). The apparatus includes a body (20) having a window (30), an optical source preferably comprising a laser diode (100) having a small light emitting area (140), and an optical system (102) for focusing the light from the laser diode at a focal spot (84) such that the size of the focal spot is approximately equal to the size of the light emitting area of the laser diode. A photodetector (106) is mounted in the body and detects light backscattered from the focal spot by particles in the fluent medium, and produces an electrical signal that comprises a series of pulses associated with the particles. The electrical signal is input to a detector that counts the pulses and indicates the number of particles in the fluent medium. The detector includes discrimination means for preventing the counting of a pulse that has a rise or fall time above a predetermined threshold, thereby discriminating against particles that are not at the focal spot. Means are provided for measuring the integrated amplitude of the electrical signal, and for varying the distance between the focal spot and the window to maximize such integrated amplitude. An intrinsically safe embodiment is also disclosed in which the probe positioned at the measuring site does not include any electrical components. This embodiment may be implemented using light of multiple wavelengths for characterizing individual particles.
Inventors
- 👤 Fritz K. Preikschat
- 👤 Ekhard Preikschat
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-28 18:49
CPC Classifications
G; G01; G01N; G01N15/00; G01N15/10; G01N15/14; G01N15/1404; G01N15/02; G01N15/0205; G01N2015/0238; G01N21/00; G01N21/17; G01N2021/1757; G01N2021/1759; G01N21/47; G01N2021/4704; G01N2021/4709; G01N2021/4711; G01N2021/4716; G01N2201/00; G01N2201/08
Claims Analysis
Total Claims: 24
Claim 1
Independent Claim
114 words
An apparatus for analyzing particles contained in a fluent medium, the apparatus comprising: illumination means comprising an optical source and an optical system for receiving light from the optical source and focusing the light at a focal spot in the fluent medium; photodetector means for detecting pulses of light resulting from the backscattering of light by particles in the focal spot, and for producing a corresponding electrical signal; and detection means connected to receive the electrical signal, the detection means including size measurement means for measuring the length of time that individual particles are in the focal spot and for thereby providing an indication corresponding to the size of particles in the fluent medium.
Claim 2
Independent Claim
114 words
An apparatus for analyzing particles contained in a fluent medium, the apparatus comprising: illumination means comprising an optical source and an optical system for receiving light from the optical source and focusing the light at a focal spot in the fluent medium; photodetector means for detecting pulses of light resulting from the backscattering of light by particles in the focal spot, and for producing a corresponding electrical signal; and detection means connected to receive the electrical signal, the detection means including size measurement means for measuring the length of time that individual particles are in the focal spot and for thereby providing an indication corresponding to the size of particles in the fluent medium.
Claim 3
Dependent Claim
48 words
The apparatus of Claim 1, wherein the optical source comprises a laser diode having a light emitting area, wherein the optical system focuses the light from the laser diode such that the size of the focal spot is approximately equal to the size of the light emitting area.
Claim 4
Dependent Claim
61 words
The apparatus of Claim 1, wherein the photodetector means includes means for producing an electric signal comprising a series of electrical pulses corresponding to the pulses of light, and wherein the detection means comprises counting means for counting the electrical pulses and discrimination means for preventing the counting of an electrical pulse that has a rise time above a predetermined threshold.
Claim 5
Dependent Claim
37 words
The apparatus of Claim 1, further comprising a body to which the illumination means is mounted, the body including a window, and wherein the illumination means positions the focal spot outside the body adjacent to the window.
Claim 6
Dependent Claim
31 words
The apparatus of Claim 4, wherein the illumination means includes means for varying the position of the focal spot with respect to the body in a direction parallel to the window.
Claim 7
Dependent Claim
57 words
The apparatus of Claim 4, wherein the detection means includes means for producing an integrated amplitude signal having a magnitude corresponding to the average amplitude of the electrical signal, and wherein the illumination means includes means for adjusting the distance between the focal spot and the window such that the integrated amplitude signal is at a maximum.
Claim 8
Dependent Claim
47 words
The apparatus of Claim 1, further comprising a body to which the illumination means and photodetector means are mounted, the illumination means comprising means for varying the position of the focal spot with respect to the body, whereby the focal spot is scanned through the fluent medium.
Claim 9
Dependent Claim
63 words
The apparatus of Claim 1, wherein the optical system comprises a beamsplitter and optical conveyance means for conveying light along a path from the beamsplitter and for focusing the light at the focal spot, and for receiving light backscattered at the focal spot and returning the backscattered light to the beamsplitter, the photodetector means being positioned to receive backscattered light from the beamsplitter.
Claim 10
Dependent Claim
62 words
The apparatus of Claim 1, wherein the photodetector means includes means for producing an electric signal comprising a series of electrical pulses corresponding to the pulses of light, and wherein the detection means includes means for separately counting the electrical pulses in a plurality of ranges of pulse length, whereby the numbers of particles in a plurality of size ranges are determined.
Claim 11
Dependent Claim
94 words
The apparatus of Claim 9, wherein the detection means comprises a plurality of first counters, each first counter being associated with a particular range of pulse lengths, means responsive to each electrical pulse for determining the pulse length and providing a signal to a selected first counter in whose range the pulse length falls, and enable means for providing an enable signal operative to enable the selected first counter to increment its count, the enable means providing the enable signal if the rise or fall time of a pulse is below a predetermined threshold.
Claim 12
Independent Claim
65 words
A method for analyzing particles contained in a fluent medium, the method comprising: producing illumination light; focusing the illumination light at a focal spot in the fluent medium; detecting illumination light that is backscattered by particles at the focal spot, and producing a corresponding electrical signal; and processing the electrical signal to produce an indication corresponding to the number of particles in the fluent medium.
Claim 13
Independent Claim
65 words
A method for analyzing particles contained in a fluent medium, the method comprising: producing illumination light; focusing the illumination light at a focal spot in the fluent medium; detecting illumination light that is backscattered by particles at the focal spot, and producing a corresponding electrical signal; and processing the electrical signal to produce an indication corresponding to the number of particles in the fluent medium.
Claim 14
Dependent Claim
29 words
The method of Claim 11, wherein the illumination light is focused to a focal spot having a size approximately equal to the size of the source of illumination light.
Claim 15
Dependent Claim
66 words
The method of Claim 11, wherein the step of detecting light includes detecting pulses of light resulting from the backscattering of light by particles in the focal spot and producing an electric signal comprising a corresponding series of electrical pulses, wherein the processing step includes counting the electrical pulses, and preventing the counting of an electrical pulse that has a rise time above a predetermined threshold.
Claim 16
Dependent Claim
61 words
The method of Claim 13, wherein the processing step includes producing an integrated amplitude signal having a magnitude corresponding to the average amplitude of the electrical signal, and wherein the method comprises the further step of varying the position of the focal spot along a longitudinal axis of the illumination light such that the integrated amplitude signal is at a maximum.
Claim 17
Dependent Claim
72 words
The method of Claim 11, wherein the step of detecting light includes detecting pulses of light resulting from the backscattering of light by particles in the focal spot and producing an electric signal comprising a corresponding series of electrical pulses, and wherein the processing step comprises separately counting the electrical pulses in a plurality of ranges of pulse length, to thereby determine the number of particles in a plurality of size range.
Claim 18
Dependent Claim
26 words
The method of Claim 11, comprising the further step of varying the position of the focal spot to scan the focal spot through the fluent medium.
Claim 19
Dependent Claim
60 words
The apparatus Claim 1, wherein the illumination means comprises a monomode fiber optic cable having first and second ends, and a laser diode including means for coupling light from the laser diode into the first end of the monomode fiber optic cable, the optical system being positioned to receive light from the second end of the monomode fiber optic cable.
Claim 20
Dependent Claim
89 words
The apparatus of Claim 17, wherein the photodetector means comprises a photodetector and a return fiber optic cable having a first end positioned to receive light backscattered by particles at the focal spot from the optical system, and a second end coupled to the photodetector, and wherein the apparatus is physically divided into a probe and a controller, the probe comprising the optical system and the controller comprising the laser diode, the photodetector and the detection means, whereby an intrinsically safe probe having no electrical components may be provided.
Claim 21
Dependent Claim
59 words
The apparatus of Claim 18, wherein the probe comprises a body to which the optical system is mounted, wherein the optical system includes pneumatic scanning means for varying the position of the focal spot with respect to the body at a scanning frequency such that the focal spot is scanned through the fluent medium with respect to the body.
Claim 22
Dependent Claim
76 words
The apparatus of Claim 19, wherein the probe includes reflector means for producing an optical timing signal in the fiber optic return cable having a frequency that varies with the scanning frequency, such that the photodetector produces a corresponding electrical timing signal, and wherein the detection means include means for receiving the electrical timing signal and for providing an indication corresponding to the number of particles in the fluent medium only from predetermined focal spot positions.
Claim 23
Dependent Claim
40 words
The apparatus of Claim 1, further including a body within which the optical system is mounted, the body including a window positioned between the optical system and the focal spot, the window comprising synthetic sapphire mounted in a titanium holder.
Claim 24
Dependent Claim
136 words
The apparatus of Claim 17, wherein the illumination means comprises a monomode fiber optic cable having first and second ends, first and second laser diodes adapted to emit light at respective first and second wavelengths, and means for coupling light from the laser diodes into the first end of the monomode fiber optic cable, and wherein the photodetector means comprises first and second photodetectors, a return fiber optic cable having a first end positioned to receive light backscattered by particles at the focal spot from the optical system, and means for spectrally dividing the light received from the second end of the return fiber optic cable such that light at the first wavelength band is substantially coupled only to the first photodetector, and light at the second wavelength is substantially coupled only to the second photodetector.
References Cited (Backward Citations)
No citation records indexed.
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