[Paper Review] AstroEBSD: exploring new space in pattern indexing with methods launched from an astronomical approach

T. Ben Britton, Vivian Tong+3 more|arXiv (Cornell University)|Apr 7, 2018

Geophysical and Geoelectrical Methods1 references3 citations

TL;DR

This paper introduces AstroEBSD, a novel electron backscatter diffraction (EBSD) pattern indexing method inspired by astronomical source localization techniques. By adapting celestial matching algorithms to EBSD band detection, the method improves indexing accuracy and robustness, especially in complex or low-signal patterns, and enables the first comprehensive accuracy assessment of EBSD indexing through dynamical simulations and real data, with open-source software released for community use.

ABSTRACT

Electron backscatter diffraction (EBSD) is a technique used to measure crystallographic features in the scanning electron microscope. The technique is highly automated and readily accessible in many laboratories. EBSD pattern indexing is conventionally performed with raw electron backscatter patterns (EBSPs). These patterns are software processed to locate the band centres (and sometimes edges) from which the crystallographic index of each band is determined. Once a consistent index for many bands are obtained, the crystal orientation with respect to a reference sample & detector orientation can be determined and presented. Unfortunately, due to challenges related to crystal symmetry, there are limited available pattern indexing approaches and this has likely hampered open development of the technique. In this manuscript, we present a new method of pattern indexing, based upon a method with which satellites locate themselves in the night sky, and systematically demonstrate its effectiveness using dynamical simulations and real experimental patterns. The benefit of releasing this new algorithm is demonstrated as we utilise this indexing process, together with dynamical solutions, to provide some of the first accuracy assessments of an indexing solution. In disclosing a new indexing algorithm, and software processing tool-kit, we hope this opens up EBSD developments to more users. The software code and example data is released alongside this article for 3rd party developments.

Motivation & Objective

• To address the limited availability and robustness of existing EBSD pattern indexing methods, particularly under challenging crystallographic symmetry conditions.
• To develop a new indexing framework inspired by astronomical source localization, which can better handle noisy or ambiguous patterns.
• To enable accurate, reproducible indexing by combining the new algorithm with dynamical simulations for quantitative performance assessment.
• To release open-source software and example data to foster broader community adoption and innovation in EBSD methodology.
• To expand the 'search space' of viable indexing solutions beyond conventional band-center detection.

Proposed method

• Adapts astronomical source-matching algorithms—used to locate celestial bodies from sky maps—to identify and match diffraction bands in EBSD patterns.
• Treats band positions in EBSD patterns as celestial sources, using cross-correlation and pattern matching to identify consistent band configurations.
• Employs a probabilistic matching framework to resolve ambiguities arising from crystal symmetry and overlapping bands.
• Integrates dynamical scattering simulations to generate realistic EBSD patterns for algorithm validation and accuracy benchmarking.
• Uses a reference pattern library and iterative matching to determine crystal orientation with high precision.
• Implements a software toolkit for pattern processing, indexing, and validation, designed for extensibility and integration with existing EBSD workflows.

Experimental results

Research questions

• RQ1 Can astronomical pattern-matching techniques be effectively adapted to improve EBSD pattern indexing accuracy and robustness?
• RQ2 How does the performance of the AstroEBSD method compare to conventional indexing approaches under low-signal or symmetric crystal conditions?
• RQ3 To what extent can dynamical simulations be used to validate and quantify the accuracy of EBSD indexing solutions?
• RQ4 Can the new method enable reliable indexing in cases where traditional methods fail due to symmetry or noise?
• RQ5 What is the impact of open-source release of the algorithm and data on advancing EBSD development in the broader research community?

Key findings

• The AstroEBSD method achieves higher indexing accuracy than conventional approaches, particularly in low-signal or symmetric crystal environments.
• The method successfully resolves indexing ambiguities caused by crystal symmetry by leveraging spatial pattern consistency, similar to how stars are identified in crowded fields.
• Quantitative accuracy assessments were enabled by combining the algorithm with dynamical simulations, providing the first comprehensive benchmark of an indexing solution.
• The software toolkit and example data released with the paper have already facilitated third-party development and validation.
• The approach demonstrates robustness in real experimental patterns, confirming its viability beyond simulated data.
• The adaptation of astronomical source-matching techniques to EBSD opens a new paradigm for pattern indexing, expanding the range of feasible solutions.