Persistent Link:
http://hdl.handle.net/10150/290646
Title:
Designing a non-scanning imaging spectrometer
Author:
George, James Dalton
Issue Date:
2001
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 non-scanning imaging spectrometer simultaneously captures spatial and spectral information via multiple diffractive orders. Optics image a color scene in a field stop. A collimating lens converts the scene's spatial information into propagation angles. A diffractive disperser multiplexes the scene's spectral information into the propagation angles. A lens focused at infinity images multiple diffractive orders onto a large sensor array, which cannot distinguish the wavelength of incident light within the spectral bandpass of the instrument. The pixels of the sensor array collapse the two-spatial, one-spectral dimensions into a discrete, two-dimensional array. This collapsing of three dimensions into two is a mathematical projection. Computed tomography uses projections to reconstruct a three-dimensional object. Hence, this non-scanning imaging spectrometer has become known as the Computed-Tomography Imaging Spectrometer, or CTIS. The results imply nominal spatial and spectral resolution limits. When each projection is considered separately, the Nyquist spatial-sampling criterion provides a resolution limit. The limit cannot be achieved for an arbitrary scene. The highest spectral resolution can be obtained only if the highest spatial frequency is present. The formula that defines what each diffractive order measures is f(λ) ≈ nₓΔₓ fₓ+n(y)Δ(y)f(y) where f(λ) is a Fourier decomposition of the wavelength spectrum across the CTIS spectral bandwidth, fₓ and f(y) are the horizontal and vertical spatial frequencies, nₓ and n(y) are the diffractive-order numbers as would be obtained by crossed diffraction gratings, and Δₓ and Δ(y) are established by the optical design. Derived from a simple model of scalar diffraction, the formula is shown to be consistent with CTIS calibrations using a technique from computed tomography known as the Fourier-crosstalk matrix. The formula extends the definition of what CTIS projections measure to include cross-orders (nₓ and n(y) can both be non-zero) and anamorphic dispersion (Δₓ ≠ Δ(y)).
Type:
text; Dissertation-Reproduction (electronic)
Keywords:
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.titleDesigning a non-scanning imaging spectrometeren_US
dc.creatorGeorge, James Daltonen_US
dc.contributor.authorGeorge, James Daltonen_US
dc.date.issued2001en_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 non-scanning imaging spectrometer simultaneously captures spatial and spectral information via multiple diffractive orders. Optics image a color scene in a field stop. A collimating lens converts the scene's spatial information into propagation angles. A diffractive disperser multiplexes the scene's spectral information into the propagation angles. A lens focused at infinity images multiple diffractive orders onto a large sensor array, which cannot distinguish the wavelength of incident light within the spectral bandpass of the instrument. The pixels of the sensor array collapse the two-spatial, one-spectral dimensions into a discrete, two-dimensional array. This collapsing of three dimensions into two is a mathematical projection. Computed tomography uses projections to reconstruct a three-dimensional object. Hence, this non-scanning imaging spectrometer has become known as the Computed-Tomography Imaging Spectrometer, or CTIS. The results imply nominal spatial and spectral resolution limits. When each projection is considered separately, the Nyquist spatial-sampling criterion provides a resolution limit. The limit cannot be achieved for an arbitrary scene. The highest spectral resolution can be obtained only if the highest spatial frequency is present. The formula that defines what each diffractive order measures is f(λ) ≈ nₓΔₓ fₓ+n(y)Δ(y)f(y) where f(λ) is a Fourier decomposition of the wavelength spectrum across the CTIS spectral bandwidth, fₓ and f(y) are the horizontal and vertical spatial frequencies, nₓ and n(y) are the diffractive-order numbers as would be obtained by crossed diffraction gratings, and Δₓ and Δ(y) are established by the optical design. Derived from a simple model of scalar diffraction, the formula is shown to be consistent with CTIS calibrations using a technique from computed tomography known as the Fourier-crosstalk matrix. The formula extends the definition of what CTIS projections measure to include cross-orders (nₓ and n(y) can both be non-zero) and anamorphic dispersion (Δₓ ≠ Δ(y)).en_US
dc.typetexten_US
dc.typeDissertation-Reproduction (electronic)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.proquest3023520en_US
dc.identifier.bibrecord.b41957830en_US
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