title: A Dictionary Approach to Electron Backscatter Diffraction Indexing.
abstract: We propose a framework for indexing of grain and subgrain structures in electron backscatter diffraction patterns of polycrystalline materials. We discretize the domain of a dynamical forward model onto a dense grid of orientations, producing a dictionary of patterns. For each measured pattern, we identify the most similar patterns in the dictionary, and identify boundaries, detect anomalies, and index crystal orientations. The statistical distribution of these closest matches is used in an unsupervised binary decision tree (DT) classifier to identify grain boundaries and anomalous regions. The DT classifies a pattern as an anomaly if it has an abnormally low similarity to any pattern in the dictionary. It classifies a pixel as being near a grain boundary if the highly ranked patterns in the dictionary differ significantly over the pixel's neighborhood. Indexing is accomplished by computing the mean orientation of the closest matches to each pattern. The mean orientation is estimated using a maximum likelihood approach that models the orientation distribution as a mixture of Von Mises-Fisher distributions over the quaternionic three sphere. The proposed dictionary matching approach permits segmentation, anomaly detection, and indexing to be performed in a unified manner with the additional benefit of uncertainty quantification.
authors.affiliation: Department of Electrical Engineering and Computer Science,University of Michigan,Ann Arbor,MI 48109,USA.
authors.forename: Yu H
authors.initials: YH
authors.lastname: Chen
authors.affiliation: Schlumberger Research,Cambridge,MA 02139,USA.
authors.forename: Se Un
authors.initials: SU
authors.lastname: Park
authors.affiliation: Thomas J. Watson Research Center, IBM Research,Yorktown Heights,NY 10598,USA.
authors.forename: Dennis
authors.initials: D
authors.lastname: Wei
authors.affiliation: Department of Electrical Engineering and Computer Science,University of Michigan,Ann Arbor,MI 48109,USA.
authors.forename: Greg
authors.initials: G
authors.lastname: Newstadt
authors.affiliation: BlueQuartz Software,Dayton,OH 45066,USA.
authors.forename: Michael A
authors.initials: MA
authors.lastname: Jackson
authors.affiliation: Materials and Manufacturing Directorate,AFRL/MLLMD,Wright-Patterson AFB,OH 45433,USA.
authors.forename: Jeff P
authors.initials: JP
authors.lastname: Simmons
authors.affiliation: Department of Materials Science and Engineering,Carnegie Mellon University,5000 Forbes Avenue,Pittsburgh,PA 15213,USA.
authors.forename: Marc
authors.initials: M
authors.lastname: De Graef
authors.affiliation: Department of Electrical Engineering and Computer Science,University of Michigan,Ann Arbor,MI 48109,USA.
authors.forename: Alfred O
authors.initials: AO
authors.lastname: Hero
keywords: EBSD; Von Mises–Fisher mixture distribution; dictionary matching; dynamical electron scattering; electron backscatter diffraction pattern; maximum likelihood orientation estimates