3.3.3.30. NXimage_set_em_kikuchi

Status:

base class, extends NXobject

Description:

Electron backscatter diffraction (EBSD) Kikuchi pattern.

The container can also store data related to a post-processing of these Kikuchi pattern, which is the backbone of orientation microscopy especially in materials science and materials engineering.

Based on a fuse of the M. A. Jackson et al. of the DREAM.3D community and the open H5OINA format of Oxford Instruments P. Pinard et al.

EBSD can be used, usually with FIB/SEM microscopes, for three-dimensional orientation microscopy. So-called serial section analyses. For a detailed overview of these techniques see e.g.

With serial-sectioning this involves however always a sequence of measuring, milling. In this regard, each serial section (measuring) and milling is an own NXevent_data_em instance and thus there such a three-dimensional characterization should be stored as a set of two-dimensional data, with as many NXevent_data_em instances as sections were measured.

These measured serial sectioning images need virtually always post-processing to arrive at the aligned and cleaned image stack respective digital microstructure representation as (a representative) volume element. Several software packages are available for this post-processing. For now we do not consider metadata of these post-processing steps as a part of this base class.

Symbols:

n_p: Number of scan points, one pattern per scan point.

n_y: Number of pixel per Kikuchi pattern in the slow direction

n_x: Number of pixel per Kikuchi pattern in the fast direction

Groups cited:

NXcollection, NXdata, NXprocess

Structure:

grid_type: (optional) NX_CHAR

Which pixel primitive shape is used.

Any of these values: square | hexagon

step_size: (optional) NX_NUMBER (Rank: 1, Dimensions: [2]) {units=NX_LENGTH}

The prescribed step size. First value is for the slow changing, second value is for the fast changing dimension.

DATA: (optional) NXdata

Collected Kikuchi pattern as an image stack.

intensity: (optional) NX_NUMBER (Rank: 3, Dimensions: [n_p, n_y, n_x]) {units=NX_UNITLESS}

@long_name: (optional) NX_CHAR

Kikuchi pattern intensity

image_id: (optional) NX_NUMBER (Rank: 1, Dimensions: [n_p]) {units=NX_UNITLESS}

@long_name: (optional) NX_CHAR

Kikuchi pattern identifier

ypos: (optional) NX_NUMBER (Rank: 1, Dimensions: [n_y]) {units=NX_LENGTH}

@long_name: (optional) NX_CHAR

Label for the y axis

xpos: (optional) NX_NUMBER (Rank: 1, Dimensions: [n_x]) {units=NX_LENGTH}

@long_name: (optional) NX_CHAR

Label for the x axis

calibration: (optional) NXprocess

oim: (optional) NXprocess

OIM, orientation imaging microscopy. Post-processing of the Kikuchi pattern to identify orientations.

pattern_quality: (optional) NX_FLOAT (Rank: 1, Dimensions: [n_p]) {units=NX_UNITLESS}

pattern_center: (optional) NX_NUMBER (Rank: 1, Dimensions: [n_p]) {units=NX_LENGTH}

detector_distance: (optional) NX_FLOAT (Rank: 1, Dimensions: [n_p]) {units=NX_LENGTH}

background_correction: (optional) NXprocess

Details about the background correction applied to each Kikuchi pattern.

band_detection: (optional) NXprocess

mode: (optional) NX_CHAR

How are Kikuchi bands detected

Obligatory value: center

band_contrast: (optional) NX_NUMBER (Rank: 1, Dimensions: [n_p]) {units=NX_UNITLESS}

band_slope: (optional) NX_NUMBER (Rank: 1, Dimensions: [n_p]) {units=NX_UNITLESS}

bands: (optional) NX_NUMBER (Rank: 1, Dimensions: [n_p]) {units=NX_UNITLESS}

How many bands were detected in the pattern.

indexing: (optional) NXprocess

mode: (optional) NX_CHAR

How are pattern being indexed?

Obligatory value: optimize_bd

min_bands: (optional) NX_NUMBER (Rank: 1, Dimensions: [n_p])

Minimum number of bands required to index the pattern

status: (optional) NX_NUMBER (Rank: 1, Dimensions: [n_p]) {units=NX_UNITLESS}

Which return value did the indexing algorithm yield for each pattern.

  • Details about bad pixels

  • Too high angular deviation

  • No solution

  • Not analyzed

  • Success

  • Unexpected errors

phase_identifier: (optional) NX_UINT (Rank: 1, Dimensions: [n_p]) {units=NX_UNITLESS}

Labels referring to the phase_identifier for each pattern (from reflectors) that matched best.

mean_angular_deviation: (optional) NX_FLOAT (Rank: 1, Dimensions: [n_p]) {units=NX_ANGLE}

confidence_index: (optional) NX_FLOAT (Rank: 1, Dimensions: [n_p]) {units=NX_UNITLESS}

reflector: (optional) NXcollection

Lattice planes used as reflectors for indexing pattern in electron-backscatter diffraction (EBSD). One collection for each reflector.

unit_cell_abc: (optional) NX_FLOAT (Rank: 1, Dimensions: [3]) {units=NX_LENGTH}

Crystallography unit cell parameters a, b, and c

unit_cell_alphabetagamma: (optional) NX_FLOAT (Rank: 1, Dimensions: [3]) {units=NX_ANGLE}

Crystallography unit cell parameters alpha, beta, and gamma

unit_cell_class: (optional) NX_CHAR

Any of these values:

  • triclinic

  • monoclinic

  • orthorhombic

  • tetragonal

  • rhombohedral

  • hexagonal

  • cubic

space_group: (optional) NX_CHAR

Crystallographic space group

laue_group: (optional) NX_CHAR

Laue group

phase_identifier: (optional) NX_UINT {units=NX_UNITLESS}

Numeral identifier for each phase. The value 0 is reversed for the unknown phase.

phase_name: (optional) NX_CHAR

Name of the phase/alias.

number_of_reflectors: (optional) NX_UINT

miller_indices: (optional) NX_NUMBER (Rank: 2, Dimensions: [number_of_reflectors, 6]) {units=NX_UNITLESS}

Miller indices \((hkl)[uvw]\).

binning: (optional) NXcollection

mode: (optional) NX_CHAR

Free-text description for instrument specific settings

binning: (optional) NX_UINT (Rank: 1, Dimensions: [2]) {units=NX_UNITLESS}

How is the camera signal binned. First the number of pixel along the slow direction. Second the number of pixel along the fast direction.

hough_transformation: (optional) NXprocess

resolution: (optional) NX_NUMBER {units=NX_UNITLESS}

profiling: (optional) NXcollection

acquisition_speed: (optional) NX_FLOAT {units=NX_FREQUENCY}

Average number of patterns taken on average.

acquisition_time: (optional) NX_FLOAT {units=NX_TIME}

Wall-clock time the acquisition took.

hit_rate: (optional) NX_FLOAT {units=NX_DIMENSIONLESS}

Fraction of successfully indexed pattern of the set.

Hypertext Anchors

List of hypertext anchors for all groups, fields, attributes, and links defined in this class.

NXDL Source:

https://github.com/nexusformat/definitions/blob/main/contributed_definitions/NXimage_set_em_kikuchi.nxdl.xml