Pattern Matching Analysis of Electron Backscatter Diffraction Patterns for Pattern Centre, Crystal Orientation and Absolute Elastic Strain Determination: Accuracy and Precision Assessment

TL;DR

This paper presents a pattern matching method using dynamic simulations to accurately determine pattern centre, crystal orientation, and strain in electron backscatter diffraction patterns, outperforming traditional methods in precision.

Contribution

It introduces a global optimisation-based pattern matching approach for EBSD analysis, demonstrating high accuracy and robustness against noise and distortions.

Findings

Error in pattern centre < 10^-5 of pattern width

Orientation error < 0.01 degrees

Better angular resolution than Hough transform-based analysis

Abstract

Pattern matching between target electron backscatter patterns (EBSPs) and dynamically simulated EBSPs was used to determine the pattern centre (PC) and crystal orientation, using a global optimisation algorithm. Systematic analysis of error and precision with this approach was carried out using dynamically simulated target EBSPs with known PC positions and orientations. Results showed that the error in determining the PC and orientation was < 10$^{-5}$ of pattern width and < 0.01{\deg} respectively for the undistorted full resolution images (956x956 pixels). The introduction of noise, optical distortion and image binning was shown to have some influence on the error although better angular resolution was achieved with the pattern matching than using conventional Hough transform-based analysis. The accuracy of PC determination for the experimental case was explored using the High Resolution (HR-) EBSD method but using dynamically simulated EBSP as the reference pattern. This was demonstrated through a sample rotation experiment and strain analysis around an indent in interstitial free steel.