Persistent Link:
http://hdl.handle.net/10150/186546
Title:
COHERENT DETECTION OF SCATTERED LIGHT BY SUBMICROMETER AEROSOLS.
Author:
PETTIT, DONALD ROY.
Issue Date:
1983
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
A particle counting instrument, the Coherent Optical Particle Spectrometer (COPS) has been developed for measuring particles in aerosol systems. It optically counts and sizes single particles one at a time as they pass through an optically defined inspection region so particle size distributions can be directly measured. COPS uses the coherent nature of light available in a laser beam to measure the phase shift in the scattered light, which is fundamentally different from previous intensity based techniques. The Van-Cittert-Zernike theorem shows that scattered light from small particles will be coherent if viewed upon at the focal point of a gathering lens. Optical homodyne detection can then be used to measure the extent of the phase shift due to the particle. Scattering mechanisms can relate the phase shift to particle diameter so particle size can be determined. An optical inspection region is given by the resolution limited blur spot diameter and depth of focus of the gathering lens. Particles scattering outside this zone will not contribute to measured phase signals. Calculations show that COPS can count in concentrations of 10('9) particles per cubic centimeter with 5% coincidence error. Mie scattering calculations, coupled with homodyne theory, predict a minimum detectable particle diameter ranging from 0.03 to 0.3 micrometers, depending on optical configuration. Theory shows that small, strongly absorbing particles impart a much larger phase shift than refractive particles so a lower detection limit is predicted for particles such as soot and silicon. Particles above one micrometer show classic resonance typical of Mie calculations. An experimental COPS system verified the predicted results from the model. Resolution of particle size ranged from 25 to 60 percent of particle diameter. Preliminary experiments showed that COPS has in situ sampling possibilities and will work for liquid systems as well. Coherent detection of scattered light shows promise for in situ measurement of submicrometer aerosols in high particle laden streams with maximum sensitivity for strongly absorbing particles.
Type:
text; Dissertation-Reproduction (electronic)
Keywords:
Aerosols -- Measurement.; Aerosols -- Optical properties.; Coherence (Optics); Optical measurements.; Light -- Scattering.
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Chemical Engineering; Graduate College
Degree Grantor:
University of Arizona

Full metadata record

DC FieldValue Language
dc.language.isoenen_US
dc.titleCOHERENT DETECTION OF SCATTERED LIGHT BY SUBMICROMETER AEROSOLS.en_US
dc.creatorPETTIT, DONALD ROY.en_US
dc.contributor.authorPETTIT, DONALD ROY.en_US
dc.date.issued1983en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractA particle counting instrument, the Coherent Optical Particle Spectrometer (COPS) has been developed for measuring particles in aerosol systems. It optically counts and sizes single particles one at a time as they pass through an optically defined inspection region so particle size distributions can be directly measured. COPS uses the coherent nature of light available in a laser beam to measure the phase shift in the scattered light, which is fundamentally different from previous intensity based techniques. The Van-Cittert-Zernike theorem shows that scattered light from small particles will be coherent if viewed upon at the focal point of a gathering lens. Optical homodyne detection can then be used to measure the extent of the phase shift due to the particle. Scattering mechanisms can relate the phase shift to particle diameter so particle size can be determined. An optical inspection region is given by the resolution limited blur spot diameter and depth of focus of the gathering lens. Particles scattering outside this zone will not contribute to measured phase signals. Calculations show that COPS can count in concentrations of 10('9) particles per cubic centimeter with 5% coincidence error. Mie scattering calculations, coupled with homodyne theory, predict a minimum detectable particle diameter ranging from 0.03 to 0.3 micrometers, depending on optical configuration. Theory shows that small, strongly absorbing particles impart a much larger phase shift than refractive particles so a lower detection limit is predicted for particles such as soot and silicon. Particles above one micrometer show classic resonance typical of Mie calculations. An experimental COPS system verified the predicted results from the model. Resolution of particle size ranged from 25 to 60 percent of particle diameter. Preliminary experiments showed that COPS has in situ sampling possibilities and will work for liquid systems as well. Coherent detection of scattered light shows promise for in situ measurement of submicrometer aerosols in high particle laden streams with maximum sensitivity for strongly absorbing particles.en_US
dc.typetexten_US
dc.typeDissertation-Reproduction (electronic)en_US
dc.subjectAerosols -- Measurement.en_US
dc.subjectAerosols -- Optical properties.en_US
dc.subjectCoherence (Optics)en_US
dc.subjectOptical measurements.en_US
dc.subjectLight -- Scattering.en_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineChemical Engineeringen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.identifier.proquest8319728en_US
dc.identifier.oclc689058116en_US
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