Compressive Electron Backscatter Diffraction Imaging

TL;DR

This paper introduces a novel EBSD imaging method that uses subsampling and inpainting with dictionary learning to reconstruct high-quality crystallographic data from significantly fewer probe positions, enabling faster analysis and application to beam-sensitive samples.

Contribution

The paper presents a new subsampling and inpainting approach using BPFA for EBSD, reducing data acquisition requirements while maintaining data quality, which is a significant advancement over traditional methods.

Findings

High-quality reconstruction from only 10% of probe positions

Potential to reduce data acquisition to 5% for inverse pole figure maps

Effective inpainting of unindexed pixels improves data interpretability

Abstract

Electron backscatter diffraction (EBSD) has developed over the last few decades into a valuable crystallographic characterisation method for a wide range of sample types. Despite these advances, issues such as the complexity of sample preparation, relatively slow acquisition, and damage in beam-sensitive samples, still limit the quantity and quality of interpretable data that can be obtained. To mitigate these issues, here we propose a method based on the subsampling of probe positions and subsequent reconstruction of an incomplete dataset. The missing probe locations (or pixels in the image) are recovered via an inpainting process using a dictionary-learning based method called beta-process factor analysis (BPFA). To investigate the robustness of both our inpainting method and Hough-based indexing, we simulate subsampled and noisy EBSD datasets from a real fully sampled Ni-superalloy dataset for different subsampling ratios of probe positions using both Gaussian and Poisson noise models. We find that zero solution pixel detection (inpainting un-indexed pixels) enables higher quality reconstructions to be obtained. Numerical tests confirm high quality reconstruction of band contrast and inverse pole figure maps from only 10% of the probe positions, with the potential to reduce this to 5% if only inverse pole figure maps are needed. These results show the potential application of this method in EBSD, allowing for faster analysis and extending the use of this technique to beam sensitive materials.