Persistent Link:
http://hdl.handle.net/10150/288965
Title:
Computed-tomography imaging spectropolarimeter (CTISP)
Author:
Miles, Brian Herndon
Issue Date:
1999
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 complete Stokes imaging spectropolarimeter has been developed based on the principles of computed-tomography, spectrometry and polarimetry. The Computed-Tomography Imaging SpectroPolarimeter (CTISP) is a polarization extension to the Computed Tomography Imaging Spectrometer (CTIS)¹. Imaging spectrometers estimate the object cube (x,y, λ), whose smallest subdivision is a voxel, while Stokes imaging spectrometers estimate four Stokes object cubes (x,y, Sp(λ); p = 0,1,2,3), one for each Stokes parameter. CTISP uses a two-dimensional disperser to diffract the image in the field stop into a 5-by-5 array of diffraction orders. As in computed tomography, each focal plane array (FPA) pixel effectively integrates a different path through the object cube, and when all pixels are recorded, a significant portion of the object cube's information is obtained. The frequency space representation of the object cube, however, indicates that two conical regions of information are not recorded, thereby limiting the reconstruction accuracy. CTISP scans only in the polarization domain (not spectral or spatial domains), acquiring four FPA frames, one behind each of the four polarization analyzers. Currently, CTISP's resolution is 33 by 33 spatially over a 3.5 degrees full angle field of view with 16 spectral bands of 20nm width covering 440nm-740nm. CTISP acquisition is modeled using the linear imaging equation gₐ=Hₐfₐ+ξₐ, which is inverted using the iterative expectation-maximization algorithm to solve for fₐ, the object cube as seen through analyzer a. The recorded diffraction images gₐ and the empirically determined calibration matrices Hₐ, are each acquired using analyzer a. The nth voxel reconstruction result is extracted from each of the four fₐ vectors to form a four element vector f(n) which is then multiplied by the inverse of the voxel characteristic matrix W(n) to obtain the estimate of the Stokes vector S(n). W(n) is derived from the four Hₐ matrices. A fully computer-controlled calibration facility and a suite of programs are used to calibrate CTISP. CTISP was validated using synthetically generated and real objects. Spectral agreement is consistent with CTIS, while Stokes parameter polarization errors were typically 0.04-0.07 for this instrument. Errors are most significant at the spectral limits of CTISP. An object dependent correction reduces these errors to below one percent.
Type:
text; Dissertation-Reproduction (electronic)
Keywords:
Engineering, Electronics and Electrical.; Physics, Astronomy and Astrophysics.; Physics, Optics.
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Graduate College; Optical Sciences
Degree Grantor:
University of Arizona
Advisor:
Dereniak, Eustace L.

Full metadata record

DC FieldValue Language
dc.language.isoen_USen_US
dc.titleComputed-tomography imaging spectropolarimeter (CTISP)en_US
dc.creatorMiles, Brian Herndonen_US
dc.contributor.authorMiles, Brian Herndonen_US
dc.date.issued1999en_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 complete Stokes imaging spectropolarimeter has been developed based on the principles of computed-tomography, spectrometry and polarimetry. The Computed-Tomography Imaging SpectroPolarimeter (CTISP) is a polarization extension to the Computed Tomography Imaging Spectrometer (CTIS)¹. Imaging spectrometers estimate the object cube (x,y, λ), whose smallest subdivision is a voxel, while Stokes imaging spectrometers estimate four Stokes object cubes (x,y, Sp(λ); p = 0,1,2,3), one for each Stokes parameter. CTISP uses a two-dimensional disperser to diffract the image in the field stop into a 5-by-5 array of diffraction orders. As in computed tomography, each focal plane array (FPA) pixel effectively integrates a different path through the object cube, and when all pixels are recorded, a significant portion of the object cube's information is obtained. The frequency space representation of the object cube, however, indicates that two conical regions of information are not recorded, thereby limiting the reconstruction accuracy. CTISP scans only in the polarization domain (not spectral or spatial domains), acquiring four FPA frames, one behind each of the four polarization analyzers. Currently, CTISP's resolution is 33 by 33 spatially over a 3.5 degrees full angle field of view with 16 spectral bands of 20nm width covering 440nm-740nm. CTISP acquisition is modeled using the linear imaging equation gₐ=Hₐfₐ+ξₐ, which is inverted using the iterative expectation-maximization algorithm to solve for fₐ, the object cube as seen through analyzer a. The recorded diffraction images gₐ and the empirically determined calibration matrices Hₐ, are each acquired using analyzer a. The nth voxel reconstruction result is extracted from each of the four fₐ vectors to form a four element vector f(n) which is then multiplied by the inverse of the voxel characteristic matrix W(n) to obtain the estimate of the Stokes vector S(n). W(n) is derived from the four Hₐ matrices. A fully computer-controlled calibration facility and a suite of programs are used to calibrate CTISP. CTISP was validated using synthetically generated and real objects. Spectral agreement is consistent with CTIS, while Stokes parameter polarization errors were typically 0.04-0.07 for this instrument. Errors are most significant at the spectral limits of CTISP. An object dependent correction reduces these errors to below one percent.en_US
dc.typetexten_US
dc.typeDissertation-Reproduction (electronic)en_US
dc.subjectEngineering, Electronics and Electrical.en_US
dc.subjectPhysics, Astronomy and Astrophysics.en_US
dc.subjectPhysics, Optics.en_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.disciplineOptical Sciencesen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorDereniak, Eustace L.en_US
dc.identifier.proquest9927468en_US
dc.identifier.bibrecord.b39560181en_US
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