ISO 24173:2024

International
Standard
ISO 24173
Second edition
Microbeam analysis — Guidelines
2024-02
for orientation measurement using
electron backscatter diffraction
Analyse par microfaisceaux — Lignes directrices pour la mesure
d'orientation par diffraction d'électrons rétrodiffusés
Reference number
© ISO 2024
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ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Equipment for EBSD. 6
5 Operating conditions . 7
5.1 Specimen preparation .7
5.2 Specimen alignment.7
5.3 Common steps in collecting an EBSP .7
5.3.1 Setting the microscope operating conditions .7
5.3.2 Detector and working distances .8
5.3.3 Camera integration/exposure time .8
5.3.4 Binning .8
5.3.5 EBSP averaging .9
5.3.6 EBSP background correction/EBSP signal correction .9
5.3.7 Band detection .10
6 Calibrations required for indexing of EBSPs .11
7 Analytical procedure . 14
7.1 Operating conditions .14
7.2 Equipment stability check . 15
7.3 EBSD analysis . 15
8 Measurement uncertainty .15
8.1 General . 15
8.2 Uncertainty of crystal orientation measurement . 15
8.3 Absolute orientation . 15
8.4 Relative orientation. 15
9 Reporting the results . 16
Annex A (informative) Principle of EBSD . 17
Annex B (informative) Specimen preparation for EBSD .18
Annex C (informative) Brief introduction to crystallography and EBSP indexing, and other
information useful for EBSD .24
Bibliography .39

iii
Foreword
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The procedures used to develop this document and those intended for its further maintenance are described
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This document was prepared by Technical Committee ISO/TC 202, Microbeam analysis.
This second edition cancels and replaces the first edition (ISO 24173:2009) which has been technically
revised.
The main changes are as follows:
— Clause 3 has been updated;
— “in the working position” is changed to “in the detector position” [see 6.6 (d)];
— subclause “7.1 Pre-test preparation” in the previous edition is omitted;
— “Annex B (normative)” is changed to “Annex B (informative)”;
— changes have been made to align this document with ISO rules.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.

iv
Introduction
Electron backscatter diffraction (EBSD) is a technique that is used with a scanning electron microscope
(SEM), a combined SEM-FIB (focussed-ion beam) microscope or an electron probe microanalyser (EPMA) to
[1],[2]
measure and map local crystallography in crystalline specimens.
Electron backscatter patterns (EBSPs) are formed when a stationary electron beam strikes the surface of
a steeply inclined specimen, which is usually tilted at ≈ 70° from normal to the electron beam. EBSPs are
imaged via an EBSD detector, which comprises a scintillator (such as a phosphor screen or a YAG single
crystal) and a low-light-level camera (normally a charge-coupled device, CCD). Patterns are occasionally
imaged directly on photographic film.
By analysing the EBSPs, it is possible to measure the orientation of the crystal lattice and, in some cases, to
also identify the phase of the small volume of crystal under the electron beam. EBSD is a surface diffraction
effect where the signal arises from a depth of just a few tens of nanometres, so careful specimen preparation
[3]
is essential for successful application of the technique.
In a conventional SEM with a tungsten filament, a spatial resolution of about 0,25 µm can be achieved;
however, with a field-emission gun SEM (FEG-SEM), the resolution limit is 10 nm to 50 nm, although the
value is strongly dependent on both the material being examined and the instrument operating parameters.
[4] [5]
A new method termed as transmission Kikuchi diffraction (TKD) or transmission EBSD (t-EBSD)
in SEM has been proved to improve spatial resolutions better than 10 nm and is suited for routine EBSD
characterization of both nano-structured and highly deformed samples.
Orientation measurements in test specimens can be carried out with an accuracy of ≈ 0,5°. By scanning the
electron beam over a region of the specimen surface whilst simultaneously acquiring and analysing EBSPs,
it is possible to produce maps that show the spatial variation of orientation, phase, EBSP quality and other
related measures. These data can be used for quantitative microstructural analysis to measure, for example,
the average grain size (and in some cases the size distribution), the crystallographic texture (distribution
of orientations) or the amount of boundaries with special characteristics (e.g. twin boundaries). EBSD
can provide three-dimensional microstructural characterization by combining with an accurate serial
[6]
sectioning technique, such as focussed-ion beam milling.
It is strongly recommended that EBSD users should be well acquainted with both the principles of
crystallography and the various methods for representing orientations (both of which are described in the
[7],[8]
existing literature in this field) in order to make best use of the EBSD technique and the data.

v
International Standard ISO 24173:2024(en)
Microbeam analysis — Guidelines for orientation
measurement using electron backscatter diffraction
1 Scope
This document gives guidance on how to generate reliable and reproducible crystallographic orientation
measurements using electron backscatter diffraction (EBSD). It addresses the requirements for specimen
preparation, instrument configuration, instrument calibration and data acquisition.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements of this document. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
ISO/IEC 17025, General requirements for the competence of testing and calibration laboratories
ISO/IEC Guide 98-3, Uncertainty of measurement — Part 3: Guide to the expression of uncertainty in
me a s ur ement (GUM: 1995)
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
crystal
entity consisting of a regular, repeated arrangement of atoms in space and usually described by a space
group, a crystal system, unit cell parameters (including the lengths and angles between the unit cell axes)
[9],[10]
and the positions of the atoms inside the unit cell
Note 1 to entry: For example, an aluminium crystal can be represented by a cube (unit cell) of length 0,404 94 nm
along each edge and with atoms at the corners and centres of the cube faces.
Note 2 to entry: Simulations of the atomic arrangement in a small (4 × 4 × 4 unit cells) aluminium crystal, as viewed
along the [1 0 0], [1 1 1] and [1 1 0] directions, are shown in Figure 1, together with the associated spherical Kikuchi
patterns for each crystal orientation. The 4-fold, 3-fold and 2-fold crystal symmetries are easily seen, as are the mirror
planes.
Note 3 to entry: For those unfamiliar with crystallography, it is recommended that a standard textbook be consulted
(see for example References [9], [10] and [11]).
Note 4 to entry: Annex C contains a brief introduction to crystallography and a guide to the indexing of EBSPs for
materials with cubic crystal symmetry.

Figure 1 — Simulations of a small aluminium crystal (top) as viewed along the [1 0 0], [1 1 1] and [1
1 0] directions, with their associated spherical Kikuchi patterns (bottom). The symmetry is clearly
shown.
3.2
crystal plane
plane, usually denoted as (h k l), representing the intersection of a plane with the a-, b- and c-axes of the unit
cell at distances of 1/h, 1/k and 1/l, where h, k, and l are the minimum mutual integers
Note 1 to entry: The integers h, k, and l are usually referred to as the Miller indices of a crystal plane.
Note 2 to entry: See Annex C for more information.
3.3
crystal direction
direction, usually denoted as [u v w], representing a vector direction in multiples of the basis vectors
describing the a, b and c crystal axes
Note 1 to entry: See Annex C for more information.
3.4
crystallographic orientation
alignment of the crystal coordinate system (for example, [1 0 0], [0 1 0], [0 0 1] for a cubic crystal) in relation
to the specimen coordinate system
Note 1 to entry: The specimen coordinate system can be denoted as X, Y, Z. When EBSD is applied to the study of rolled
materials, it is often denoted as RD, TD, ND [RD = reference (or rolling) direction, TD = transverse direction and ND =
normal direction].
3.5
EBSD detector
detector used to capture the backscatter electron signal and convert it to an visible image on the display
device (computer screen) via a video-camera, which is commonly a high-sensitivity charge-coupled device
(CCD), or complementary metal-oxide-semiconductors (CMOS)

3.6
electron backscatter diffraction
EBSD
diffraction process that arises between the backscattered electrons and the atomic planes of a highly tilted
crystalline specimen when illuminated by a stationary incident electron beam
Note 1 to entry: Commonly used alternative terms for EBSD are “EBSP” (or more usually the “EBSP technique”), “BKD”
(backscattered Kikuchi diffraction), “BKED” (backscattered Kikuchi electron diffraction) and “BKDP” (backscattered
Kikuchi diffraction pattern).
Note 2 to entry: See Annex A for more information.
3.7
electron backscatter pattern
EBSP
intersecting array of quasi-linear features, known as Kikuchi bands (see Figure 2), produced by electron
backscatter diffraction and recorded using a suitable detector, for example observed on a phosphorescent
screen or, less commonly, on photographic film
Figure 2 — Examples of EBSPs showing arrays of overlapping Kikuchi bands
3.8
pattern centre
PC
point in the plane of the detector screen on a line normal to the plane of the screen and passing through the
point where the electron beam strikes the specimen
3.9
Euler angles
set of three rotations for representing the orientation of a crystal relative to a set of specimen axes
Note 1 to entry: The Bunge convention (rotations about the Z, X'and Z"directions) is most commonly used for describing
EBSD data. The Euler angles give the rotation needed to bring the specimen coordinate system into coincidence with
the crystal coordinate system. It should be noted that there are equivalent sets of Euler angles, depending on crystal
[8]
symmetry .
3.10
Hough transform
mathematical technique of image processing which allows the automated detection of features of a particular
shape within an image
Note 1 to entry: In EBSD, a linear Hough transform is used to identify the position and orientation of the Kikuchi bands
in each EBSP (3.7), which enables the EBSP to be indexed. Each Kikuchi band is identified as a maximum in Hough
space. The Hough transform is essentially a special case of the Radon transform. Generally, the Hough transform is for
[12],[13]
binary images, and the Radon transform is for grey-level images. See 5.3.7 for more details.

3.11
indexing
process of identifying the crystallographic orientation corresponding to the features in a given EBSP, for
example, determining which crystal planes correspond to the detected Kikuchi bands or which crystal
directions match the Kikuchi band intersections (zone axes) and thereby determining the orientation (and
phase)
3.12
orientation
alignment of a crystal axes relative to a set of specimen axes
Note 1 to entry: It is usually represented by Euler angles (ϕ , Φ, ϕ ) or a 3 × 3 orientation matrix of direction cosines
1 2
between the crystal and specimen axes and/or a Rodrigues-Frank vector.
3.13
orientation map
OM
map-like display of crystal orientation data derived from the sequential measurement of the crystal
orientation at each point in a grid
Note 1 to entry: See Reference [14] for more information.
Note 2 to entry: Alternative terms are crystal orientation map (COM), automated crystal orientation map and
orientation imaging microscopy map.
3.14
misorientation
difference in the orientation of two crystallites, usually expressed as an angle/axis pair
Note 1 to entry: Misorientation is the rotation required to bring one crystal grain into coincidence with another. It can
be described by a rotation matrix, a set of Euler angles, an axis/angle pair or a Rodriguez vector. The axis/angle pair is
most common, but the smallest angle description is generally used.
Note 2 to entry: The EBSD software calculates the crystal orientation of a particular point on the specimen surface
based on the EBSP (3.7) acquired at that point. The software can then calculate the misorientation between any two
[15]
chosen acquisition pixels (which can or cannot be neighbours in the orientation map) .
3.15
transmission Kikuchi diffraction
TKD
SEM-based electron-transparent diffraction applies conventional EBSD hardware to a sample
[5]
Note 1 to entry: Commonly used alternative terms for TKD are “t-EBSD” .
Note 2 to entry: It has been proven to enable spatial resolutions better than 10 nm. This technique is ideal for routine
EBSD characterisation of both nanostructured and highly deformed samples.
3.16
phase identification
crystallographic identification of an unknown phase in a specimen by comparing the features of the acquired
[16],[17],[18]
EBSP (3.7) with those simulated or calculated from a set of possible candidate phases
Note 1 to entry: This can be an automatic process in which the EBSD software searches a preselected set of crystal
phase databases and determines the phase whose simulated EBSP (3.7) best matches the acquired EBSP. In this
situation, the procedure is referred as phase discrimination. Alternatively, it can be a manual process in which
features of the EBSP (3.7), such as its symmetry, band widths and HOLZ (higher-order Laue zone) lines are used in the
identification procedure. In either case, information about the chemical composition obtained using energy-dispersive
X-ray spectrometry (EDX) or wavelength-dispersive X-ray spectrometry (WDX) can be additionally used to reduce the
list of possible phases, thereby speeding up the process and providing an increased level of confidence in the results.

3.17
phosphor screen
screen used to convert the electron signal to a visible light signal which can be detected with a low-light-
level camera
Note 1 to entry: Most EBSD phosphors are made of a thin layer of phosphor particles, ≈ 4 µm to 10 µm in size, held
together with a binder and having a final aluminium coating that both dissipates charge and acts as a mirror to
increase the EBSP (3.7) signal but is thin enough to be relatively electron-transparent.
3.18
specimen-to-screen distance
SSD
distance between the pattern centre in the detector screen and the point where the electron beam strikes
the specimen
Note 1 to entry: If the specimen-to-screen distance decreases, then the EBSP (3.7) will appear to zoom out about the
pattern centre, i.e. more Kikuchi bands will be seen.
3.19
spherical Kikuchi map
SKM
representation of the EBSP (3.7) diffraction pattern projected on to the surface of a sphere, as shown in
Figure 3, the diffracted signal emanating spherically from a point source on the specimen surface
Note 1 to entry: Spherical Kikuchi maps are useful in that they avoid the distortions associated with the gnomonic
projection of the EBSD signal onto the flat phosphor screen used to capture each EBSP (3.7).
Note 2 to entry: The spherical Kikuchi map is centred about the specimen and aligned with the crystallographic
directions of the crystal being examined. As the crystal is rotated, the spherical Kikuchi map moves in synchrony.
NOTE This orientation is the standard silicon calibration orientation for a 70° tilted specimen; the incident
electron beam direction is shown.
Figure 3 — Schematic diagram showing a silicon unit cell (right) with the main crystal directions
labelled and, on the left, a spherical Kikuchi map of silicon at the same orientation
3.20
symmetry
property an object has if it looks the same when rotated with a certain angle, translated or mirrored in a
certain way
Note 1 to entry: For further information, see Annex C.

3.21
zone axis
point in an EBSP (3.7) where the centres of several Kikuchi bands intersect
Note 1 to entry: It corresponds to a low-index crystal direction in the EBSP (3.7).
3.22
Bravais lattice
three-dimensional geometric arrangement of the atoms or molecules or ions making up a crystal
4 Equipment for EBSD
4.1 SEM, EPMA or FIB instrument, fitted with an electron column and including controls for beam
position, stage, focus and magnification (see Figure 4).
4.2 Accessories, for detecting and indexing electron backscatter diffraction patterns, including:
4.2.1 Phosphorescent (“phosphor”) screen, which is fluoresced by electrons from the specimen to form
the diffraction pattern.
4.2.2 Video camera, with low light sensitivity, for viewing the diffraction pattern produced on the screen.
4.2.3 Computer, with image processing, computer-aided pattern indexing, data storage and data
processing, and SEM beam (or stage) control to allow mapping.
NOTE 1 Modern systems generally use charge-coupled devices (CCDs) or complementary metal-oxide-
semiconductors (CMOS).
NOTE 2 Some systems incorporate detector(s) mounted around the phosphor screen to detect electrons scattered
in the forward direction from the specimen; the detectors are usually silicon diodes, similar to those used in solid-state
backscatter detectors. The images (orientation and atomic number contrast) give a rapid overview of the specimen
[19]
microstructure .
Key
1 EBSD instrument 5 chamber
2 SEM 6 EBSD computer
3 EDX (energy-dispersive spectrometer) (optional) 7 beam control
4 tilted specimen 8 SEM and stage control
Figure 4 — Diagram of an experimental EBSD arrangement

4.3 If specimens need to be prepared for EBSD, the following equipment can be required (depending
on the types of specimen to be prepared — see Annex B): cutting and mounting equipment, mechanical
grinding and polishing equipment, electrolytic polisher, ultrasonic cleaner, ion-sputtering equipment and
coating equipment.
5 Operating conditions
5.1 Specimen preparation
The volume of material sampled by the electron beam during EBSD analysis shall be crystalline. The crystal
features (e.g. grain size, deformation state) of this volume should be representative of the bulk specimen or
part of the specimen about which the nature of the microstructure will be inferred in the case of segmented
microstructures (e.g. layered thin films or heat-affected/non-heat-affected zones near welds). Since the
EBSP is generated by electron diffraction within a few tens of nanometres of the specimen surface, very
good preparation of the specimen surface is required to prevent the EBSD data from being deleteriously
affected by inadequate preparation. The top layer under investigation shall be free from deformation due
to specimen preparation and flat. Poor specimen preparation can leave deformation at, or just below, the
surface or can leave contaminants, oxides or reaction product layers on the specimen surface. Due to the
high tilt of the specimen surface (typically 70°) with respect to the electron beam, minimizing surface relief
is also an important part of good specimen preparation. Guidelines on specimen preparation for EBSD are
given in Annex B.
5.2 Specimen alignment
Accurate calibration (see Clause 6) and measurement using EBSD requires careful specification of the
alignment between the coordinate systems of the specimen, the SEM scanning coils, the stage and the
EBSD detector. The specimen shall be aligned in the microscope such that the normal to the acquisition
surface is at a chosen tilt angle (typically ≈ 70°) to the electron beam and such that a reference direction
on the acquisition surface, often a specimen edge, is parallel to both the stage tilt axis and, in the case of
beam scanning, to one axis of the beam-scanning system. Accurate alignment can be achieved more easily
when the specimen is mounted on a stage that allows rotation of the specimen within the tilted acquisition
plane, since fine adjustment can be performed with the specimen inside the microscope. First, the specimen
reference direction shall be aligned with the stage tilt axis. This alignment can be verified by moving the
stage back and forth along the tilt axis and checking in the electron image that the specimen reference
direction moves back and forth through a fixed point on the display, such as a particular intersection point
on a grid overlay. The long axis of the beam scan can then be aligned with the tilt direction by adjusting the
scan rotation until these two directions appear aligned in the electron image. If a pre-tilted specimen holder
is being used (or the stage does not allow rotation within the acquisition plane), then it is critical that the
specimen be mounted with the specimen reference direction as close as possible to one of the orthogonal
SEM stage axes. With a manual-tilt stage, a mechanical end-stop at the desired tilt angle is recommended so
that the stage can be tilted to the desired tilt angle with better reproducibility.
5.3 Common steps in collecting an EBSP
5.3.1 Setting the microscope operating conditions
5.3.1.1 Accelerating voltage
To contribute to the formation of the pattern, the electrons must have sufficient energy so that, when
backscattered, they retain enough energy to cause scintillation in the phosphor screen. This also increases
the number of electrons falling on the screen and thus the brightness of the diffraction pattern. This allows
the integration time of the camera to be reduced but will make the spatial resolution poorer by increasing
the electron beam size. Note, however, that this reduced resolution is typically only a small effect. An
accelerating voltage ranging between 15 kV and 30 kV is recommended for most applications. Increasing
the accelerating voltage reduces the electron wavelength and hence reduces the width of the Kikuchi bands
in the diffraction pattern. Lower accelerating voltages within this range are beneficial for analysing the

material below a very thin (up to approximately 10 nm) conducting coating or very thin layer of surface
deformation.
5.3.1.2 Probe current
Increasing the probe current will increase the number of electrons contributing to the diffraction pattern
and so allow the camera integration time to be reduced, allowing faster mapping. However, this advantage
shall be balanced against the associated loss of spatial resolution because increasing the probe current
results in the EBSD signal being generated from a larger volume in the specimen and also increases problems
due to both charging and contamination effects.
The electron beam shall be focussed on the specimen surface and dynamic focussing used, if available, to
compensate for the tilted specimen.
5.3.2 Detector and working distances
For general use, the ideal working distance for EBSD is the working distance at which the brightest region of
the raw EBSP (i.e. without background correction) is in the centre of the phosphor screen. Other experiments
can dictate a different position. Pattern intensity can be increased by increasing the camera gain but at the
expense of increasing noise levels. Short working distances will generally improve the spatial resolution of
EBSD measurements, although additional care has to be taken to avoid collisions between the specimen and
the SEM pole-piece or the backscatter detector (if present).
The ideal detector (specimen-to-screen) distance for EBSD depends on the size of the phosphor screen and
on the nature of the analysis being conducted. For a typical EBSD investigation, the phosphor screen is placed
approximately 15 mm to 25 mm from the intersection point between the electron beam and the specimen.
With a smaller specimen-to-screen distance, more bands are captured in each EBSP, which can be useful for
improving the indexing of low-symmetry phases and for improving discrimination between phases or of
orientations with similar (pseudosymmetric) EBSPs. With a larger specimen-to-screen distance, a smaller
region of diffraction space is imaged on the phosphor screen, and the bands in each captured EBSP are
wider. Automated indexing might, however, not be possible if the detector distance is increased beyond a
certain value.
At low magnifications, the pattern centre position will move significantly during beam scanning, and this
will affect the accuracy of the orientation data collected. Some systems have calibration and indexing
routines that account for this movement. Some systems allow for calibrations at different working distances
and interpolate between these for intermediate working distances. The range of working distances for
which the EBSD system remains accurately calibrated shall be determined.
5.3.3 Camera integration/exposure time
Most modern CCD cameras have the ability to control the amount of time that the camera pixels are exposed
to light. This parameter is usually referred to as the camera integration or exposure time. Long exposure
times will generally give better-quality EBSPs with lower noise levels; however, if the exposure time is too
long, parts of the image can become saturated (i.e. completely white).
The integration time should be set so that the raw EBSP (i.e. without background correction) is as bright as
possible without any portion of the EBSP becoming over-saturated. The integration time required to achieve
this condition will be smaller with higher atomic number of the phase being examined, higher accelerating
voltage, higher probe current, smaller detector distance, lower camera resolution (higher binning levels)
and higher gain setting. The integration time shall be optimized for the specific conditions used in each
experiment to make full use of the dynamic range of cameras (CCD or CMOS). A useful check is to examine
the grey-level histogram of the raw, unprocessed EBSP and to adjust the settings so that approximately 75 %
of the range is being used.
5.3.4 Binning
Most modern of cameras (CCD or CMOS) are capable of combining blocks of pixels to give an enhanced, i.e.
brighter, signal and higher camera sensitivity, at the cost, however, of a lower-resolution image. Binning can

be used to increase the speed of EBSP mapping as the increased binning results in a faster camera (CCD or
CMOS) readout speed. Binning also increases the effective sensitivity of the detector.
The series of images in Figure 5 shows the effects of binning on the EBSP signal and speed as the binning
factor is repeatedly doubled. Each doubling corresponds to a halving of the EBSP image width in pixel units.
Figure 5 — Schematic diagram showing the effect of camera binning on image size, intensity and
speed
5.3.5 EBSP averaging
Digital averaging of several EBSPs gathered from the same crystal volume is sometimes carried out to
reduce the noise level in the final EBSP. EBSP averaging leads to higher-quality EBSPs but slows down the
EBSD mapping speed. The total camera time is the product of the camera integration time (time per frame)
and the number of frames used to obtain the averaged EBSP but can improve indexing rates and indexing
quality in some applications. Averaging between 1 frame (i.e. no averaging) and 3 frames is typical for
mapping. Higher levels of averaging can be used for some applications, such as difficult phase identification.
5.3.6 EBSP background correction/EBSP signal correction
EBSPs generally have a bright centre and become much darker near the corners. Background correction
should be used to convert the “raw” EBSPs into ones with more uniform average brightness across them
and with better local contrast near the edges and corners. Background correction involves collecting
a background signal and then removing it from an EBSP by subtraction, division or a mixture of the two.
(Division usually improves the contrast in the corners of the EBSP and, in image-processing terms, is called
“flat-fielding”.) Two methods are generally used to obtain a signal for the background correction. In the first
method, an EBSP is collected while the beam is scanned over a large number of grains in a polycrystalline
specimen. Since a large number of EBSPs has been averaged, the resulting pattern has no bands but retains
the brightness gradient from centre to corners that is present in raw EBSPs . This pattern with no bands is
used as a background to enhance the contrast in all subsequently collected EBSPs. In the second method, a
background is created from each collected EBSP by using a mathematical “blurring” function to smooth out
the short-range contrast (i.e. the bands). This background is then used to enhance the contrast in the EBSP
from which it was created. This method tends to accentuate flaws in the scintillator (phosphor) or abnormal
pixels in the CCD, so its use should be avoided on a system with these problems. The time taken for pattern
processing is also slightly greater when using this method.

For many applications, particularly the analysis of deformed materials, it is advisable to use a combination
of both methods. For some applications, one method can be preferable. The second method is very useful
for single-crystal specimens and for specimens with very large grain sizes, where it can be difficult or
impossible to scan the beam over a sufficiently large number of grains. If the first method is used for such
specimens, the specimen should, if possible, be continuously rotated while the background is being acquired;
this will smear out the EBSP and produce a better background than digital smoothing of the EBSP.
5.3.7 Band detection
Band detection during EBSD refers to the automatic detection of Kikuchi bands in an EBSP via use of a Hough
[12],[13]
transform, as depicted in Figure 6 .
a) b)
c) d)
Key
r radius of area of interest
ρ distance of a specimen line from the origin
θ inclination of the specimen line
Figure 6 — Schematic diagram showing a) a downsized EBSP of ≈ 100 pixels in width; b) a Hough
space parameterization; c) a Hough transform of the EBSP shown in a); d) the original EBSP with the
detected bands 1 to 7, corresponding to the numbered peaks in c), superposed
Note the following.
a) At the user's discretion, the resolution of the EBSP can be reduced by binning, to increase speed.

b) Hough space is parameterized in terms of ρ and θ which represent the distance of each specimen
line from the origin and the inclination of the line, respectively (see Figure 6). A point in Hough space
transforms to a straight line in the EBSP. Correspondingly, a point in each EBSP transforms to a
sinusoidal curve in Hough space that defines each specimen line that passes through the point.
c) Once the Hough space transformation has been carried out (in practice, this is achieved using an
accumulation algorithm) and, optionally, normalized (to correct for the variation of specimen line length
with position in Hough space), the Hough image can be filtered to highlight the peaks that correspond
to the Kikuchi band. This is normally done using a so-called “butterfly” filter. In Hough space, each
Kikuchi band appears as a bright peak with a pair of darker valleys above and below. The bright peak
corresponds to the Kikuchi band centre, and the dark valleys to the two edges of the Kikuchi band.
d) The Kikuchi bands detected can optionally be displayed on top of the original EBSP.
e) The quality of indexing for given settings of the Hough transform shall be checked (see Clause 8). If the
indexing is poor, the suitability of the settings for the Hough transform should be investigated.
Care is required in setting the parameters for the Hough transform, and the effects of changing them on the
indexing of patterns of materials similar to those of interest should be observed.
6 Calibrations required for indexing of EBSPs
6.1 Calibration of the EBSD system geometry is required to measure accurately the relationship between
the specimen and the crystallographic axes (the crystal orientation). For this, it is necessary to be able to
determine the (x, y) position of the pattern centre (PC) on the phosphor screen and the specimen-to-screen
distance (SSD) (see Figure 7).
6.2 The calibration applies to a fixed tilt angle of the specimen, a fixed position of the screen or camera
assembly and a fixed working distance of the microscope. Any alteration of these parameters can affect the
result of pattern indexing and requires a recalibration.
In systems where magnetic fields are present near the specimen, calibration shall also include measurement
of the effects of distortions in the EBSP caused by these magnetic fields.
6.3 At any magnification, the PC position will move as the beam is scanned over the specimen. At low
magnification, the PC motion can be significant and might affect the accuracy and results of the indexing
routines. Some systems have calibration and indexing routines that allow for this movement. Some systems
allow calibration at different working distances and interpolation for intermediate working distances. It is
important that the range of working distances for which the EBSD system were accurately calibrated.

6.4 The EBSP is a gnomonic projection of the diffraction sphere on to the detector screen; points furthest
from the PC are distorted/stretched the most. The PC and the SSD are the most important calibration
parameters and, for accurate absolute orientation measurements, the PC shall be accurately determined.
Key
1 pattern centre (PC)
2 specimen-to-screen distance (SSD)
Figure 7 — Schematic diagram showing the main EBSD geometry calibration parameters
6.5 If the PC is displaced, then the centre of the EBSP diffraction sphere will also be displaced by the same
amount. For small displacements, this will appear in certain parts of each pattern to be a rotation, hence it
can be difficult to accurately fit the PC position using iterative fitting of the Kikuchi bands.
NOTE The images in Figure 8 show a silicon EBSP a) correctly calibrated (note how well the simulated black lines
match the Kikuchi bands), b) with the PC displaced horizontally and c) with the PC displaced vertically.
a) b) c)
Figure 8 — Example of EBSP indexing as a function of PC position: a) correct indexing with an
accurate PC (white cross) — the simulated bands (black) align with the real Kikuchi bands; b) the
PC is displaced horizontall
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