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dc.contributor.authorPalkki, Ryan D.en_US
dc.date.accessioned2013-01-17T22:06:09Z
dc.date.available2013-01-17T22:06:09Z
dc.date.issued2011-11-14en_US
dc.identifier.urihttp://hdl.handle.net/1853/45935
dc.description.abstractRaman spectroscopy provides a powerful means of chemical identification in a variety of fields, partly because of its non-contact nature and the speed at which measurements can be taken. The development of powerful, inexpensive lasers and sensitive charge-coupled device (CCD) detectors has led to widespread use of commercial and scientific Raman systems. However, relatively little work has been done developing physics-based probabilistic models for Raman measurement systems and crafting inference algorithms within the framework of statistical estimation and detection theory. The objective of this thesis is to develop algorithms and performance bounds for the identification of chemicals from their Raman spectra. First, a Poisson measurement model based on the physics of a dispersive Raman device is presented. The problem is then expressed as one of deterministic parameter estimation, and several methods are analyzed for computing the maximum-likelihood (ML) estimates of the mixing coefficients under our data model. The performance of these algorithms is compared against the Cramer-Rao lower bound (CRLB). Next, the Raman detection problem is formulated as one of multiple hypothesis detection (MHD), and an approximation to the optimal decision rule is presented. The resulting approximations are related to the minimum description length (MDL) approach to inference. In our simulations, this method is seen to outperform two common general detection approaches, the spectral unmixing approach and the generalized likelihood ratio test (GLRT). The MHD framework is applied naturally to both the detection of individual target chemicals and to the detection of chemicals from a given class. The common, yet vexing, scenario is then considered in which chemicals are present that are not in the known reference library. A novel variation of nonnegative matrix factorization (NMF) is developed to address this problem. Our simulations indicate that this algorithm gives better estimation performance than the standard two-stage NMF approach and the fully supervised approach when there are chemicals present that are not in the library. Finally, estimation algorithms are developed that take into account errors that may be present in the reference library. In particular, an algorithm is presented for ML estimation under a Poisson errors-in-variables (EIV) model. It is shown that this same basic approach can also be applied to the nonnegative total least squares (NNTLS) problem. Most of the techniques developed in this thesis are applicable to other problems in which an object is to be identified by comparing some measurement of it to a library of known constituent signatures.en_US
dc.publisherGeorgia Institute of Technologyen_US
dc.subjectSpectral unmixingen_US
dc.subjectMinimum description length (MDL)en_US
dc.subjectNonnegative matrix factorization (NMF)en_US
dc.subjectClassificationen_US
dc.subjectIteratively reweighted least squaresen_US
dc.subjectErrors-in-variables (EIV) modelingen_US
dc.subjectDetectionen_US
dc.subject.lcshRaman spectroscopy
dc.subject.lcshParameter estimation
dc.subject.lcshAlgorithms
dc.titleChemical identification under a poisson model for Raman spectroscopyen_US
dc.typeDissertationen_US
dc.description.degreePhDen_US
dc.contributor.departmentElectrical and Computer Engineeringen_US
dc.description.advisorCommittee Chair: Lanterman, Aaron; Committee Member: Blair, W. Dale; Committee Member: Citrin, David; Committee Member: McLaughlin, Steven; Committee Member: Vidakovic, Branien_US


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