2. Electron backscatter diffraction (EBSD) is a common laboratory based tool used to
measure crystal orientations from crystalline sam-ples.
The emergence of the technique can be traced to rapid image anal-ysis (or)
pattern analysis routines to produce extremely rich data sets that can be
interro- gated for
1. crystallographic texture,
2. grain orientation,
3. grain shape, and
4. local deformation structure.
Frames of reference
Establishing a consistent coordinate frame, with appropriate trans- formations
between the sample, the crystal structure, and the diffrac- tion pattern is at the
heart of successful and confident use of EBSD orientation data.
3. Electron backscatter diffraction (EBSD) is
an automated technique that can
measure the orientation of crystals in a
sample very rapidly. There are many
sophisticated software packages that
present measured data. Unfortu- nately,
due to crystal symmetry and differences in
the set-up of microscope and EBSD
software, there may be ac-curacy issues
when linking the crystal orientation to a
particular microstructural feature.
4. A natural choice of coordinate system is based
upon the gnomonic projection used to capture
the angular diffraction data on a flat phos-
phor screen, starting with the source point at
the electron beam position on the sample, and
the central Z-axis of the gnomonic projection
meet- ing the detector plane at the point that
is called the “pattern centre” (PC). The
gnomonic projection transforms polar angles θ
into radial dis- tances ρ = tan (θ) measured
from the pattern centre. This is why, for the
detector plane, we define a gnomonic, two-
dimensional (Xg, Yg) coordi- nate system with
(0, 0) at the pattern centre, where (xg, yg) are
the re- spective components of the radial
distance ρ.
