NXem_ebsd_conventions

Status:

base class, extends NXobject

Description:

Conventions for rotations and coordinate systems to interpret EBSD data.

This is the main issue which currently is not in all cases documented and thus limits the interoperability and value of collected EBSD data. Not communicating EBSD data with such contextual pieces of information and the use of file formats which do not store this information is the key unsolved problem.

Symbols:

No symbol table

Groups cited:

NXprocess

Structure:

rotation_conventions: (optional) NXprocess

Mathematical conventions and materials-science-specific conventions required for interpreting every collection of orientation data.

three_dimensional_rotation_handedness: (optional) NX_CHAR

Convention how a positive rotation angle is defined when viewing from the end of the rotation unit vector towards its origin, i.e. in accordance with convention 2 of DOI: 10.1088/0965-0393/23/8/083501. Counter_clockwise is equivalent to a right-handed choice. Clockwise is equivalent to a left-handed choice.

Any of these values: undefined | counter_clockwise | clockwise

rotation_convention: (optional) NX_CHAR

How are rotations interpreted into an orientation according to convention 3 of DOI: 10.1088/0965-0393/23/8/083501.

Any of these values: undefined | passive | active

euler_angle_convention: (optional) NX_CHAR

How are Euler angles interpreted given that there are several choices (e.g. ZXZ, XYZ, etc.) according to convention 4 of DOI: 10.1088/0965-0393/23/8/083501. The most frequently used convention is ZXZ which is based on the work of H.-J. Bunge but other conventions are possible.

Any of these values: undefined | zxz

axis_angle_convention: (optional) NX_CHAR

To which angular range is the rotation angle argument of an axis-angle pair parameterization constrained according to convention 5 of DOI: 10.1088/0965-0393/23/8/083501.

Any of these values: undefined | rotation_angle_on_interval_zero_to_pi

orientation_parameterization_sign_convention: (optional) NX_CHAR

Which sign convention is followed when converting orientations between different parameterizations/representations according to convention 6 of DOI: 10.1088/0965-0393/23/8/083501.

Any of these values: undefined | p_plus_one | p_minus_one

processing_reference_frame: (optional) NXprocess

Details about eventually relevant named directions that may give reasons for anisotropies. The classical example is cold-rolling where one has to specify which directions (rolling, transverse, and normal) align how with the direction of the base vectors of the sample_reference_frame.

reference_frame_type: (optional) NX_CHAR

Type of coordinate system and reference frame according to convention 1 of DOI: 10.1088/0965-0393/23/8/083501.

Any of these values:

  • undefined

  • right_handed_cartesian

  • left_handed_cartesian

xaxis_direction: (optional) NX_CHAR

Direction of the positively pointing x-axis base vector of the processing_reference_frame. We assume the configuration is inspected by looking towards the sample surface from a position that is located behind the detector.

Any of these values:

  • undefined

  • north

  • east

  • south

  • west

  • in

  • out

xaxis_alias: (optional) NX_CHAR

Name or alias assigned to the x-axis base vector, e.g. rolling direction.

yaxis_direction: (optional) NX_CHAR

Direction of the positively pointing y-axis base vector of the processing_reference_frame. We assume the configuration is inspected by looking towards the sample surface from a position that is located behind the detector. For further information consult also the help info for the xaxis_direction field.

Any of these values:

  • undefined

  • north

  • east

  • south

  • west

  • in

  • out

yaxis_alias: (optional) NX_CHAR

Name or alias assigned to the y-axis base vector, e.g. transverse direction.

zaxis_direction: (optional) NX_CHAR

Direction of the positively pointing z-axis base vector of the processing_reference frame. We assume the configuration is inspected by looking towards the sample surface from a position that is located behind the detector. For further information consult also the help info for the xaxis_direction field.

Any of these values:

  • undefined

  • north

  • east

  • south

  • west

  • in

  • out

zaxis_alias: (optional) NX_CHAR

Name or alias assigned to the z-axis base vector, e.g. normal direction.

origin: (optional) NX_CHAR

Location of the origin of the processing_reference_frame. This specifies the location Xp = 0, Yp = 0, Zp = 0. Assume regions-of-interest in this reference frame form a rectangle or cuboid. Edges are interpreted by inspecting the direction of their outer unit normals (which point either parallel or antiparallel) along respective base vector direction of the reference frame.

Any of these values:

  • undefined

  • front_top_left

  • front_top_right

  • front_bottom_right

  • front_bottom_left

  • back_top_left

  • back_top_right

  • back_bottom_right

  • back_bottom_left

sample_reference_frame: (optional) NXprocess

Details about the sample/specimen reference frame.

reference_frame_type: (optional) NX_CHAR

Type of coordinate system and reference frame according to convention 1 of DOI: 10.1088/0965-0393/23/8/083501. The reference frame for the sample surface reference is used for identifying positions on a (virtual) image which is formed by information collected from an electron beam scanning the sample surface. We assume the configuration is inspected by looking towards the sample surface from a position that is located behind the detector. Reference DOI: 10.1016/j.matchar.2016.04.008 The sample surface reference frame has coordinates Xs, Ys, Zs. In three dimensions these coordinates are not necessarily located on the surface of the sample as there are multiple faces/sides of the sample. Most frequently though the coordinate system here is used to define the surface which the electron beam scans.

Any of these values:

  • undefined

  • right_handed_cartesian

  • left_handed_cartesian

xaxis_direction: (optional) NX_CHAR

Direction of the positively pointing x-axis base vector of the sample surface reference frame. We assume the configuration is inspected by looking towards the sample surface from a position that is located behind the detector. Different tools assume that different strategies can be used and are perceived as differently convenient to enter details about coordinate system definitions. In this ELN users have to possibility to fill in what they assume is sufficient to define the coordinate system directions unambiguously. Software which works with this user input needs to offer parsing capabilities which detect conflicting input and warn accordingly.

Any of these values:

  • undefined

  • north

  • east

  • south

  • west

  • in

  • out

yaxis_direction: (optional) NX_CHAR

Direction of the positively pointing y-axis base vector of the sample surface reference frame. We assume the configuration is inspected by looking towards the sample surface from a position that is located behind the detector. For further information consult also the help info for the xaxis_direction field.

Any of these values:

  • undefined

  • north

  • east

  • south

  • west

  • in

  • out

zaxis_direction: (optional) NX_CHAR

Direction of the positively pointing z-axis base vector of the sample surface reference frame. We assume the configuration is inspected by looking towards the sample surface from a position that is located behind the detector. For further information consult also the help info for the xaxis_direction field.

Any of these values:

  • undefined

  • north

  • east

  • south

  • west

  • in

  • out

origin: (optional) NX_CHAR

Location of the origin of the sample surface reference frame. This specifies the location Xs = 0, Ys = 0, Zs = 0. Assume regions-of-interest in this reference frame form a rectangle or cuboid. Edges are interpreted by inspecting the direction of their outer unit normals (which point either parallel or antiparallel) along respective base vector direction of the reference frame.

Any of these values:

  • undefined

  • front_top_left

  • front_top_right

  • front_bottom_right

  • front_bottom_left

  • back_top_left

  • back_top_right

  • back_bottom_right

  • back_bottom_left

detector_reference_frame: (optional) NXprocess

Details about the detector reference frame.

reference_frame_type: (optional) NX_CHAR

Type of coordinate system/reference frame used for identifying positions in detector space Xd, Yd, Zd, according to DOI: 10.1016/j.matchar.2016.04.008.

Any of these values:

  • undefined

  • right_handed_cartesian

  • left_handed_cartesian

xaxis_direction: (optional) NX_CHAR

Direction of the positively pointing x-axis base vector of the detector space reference frame. We assume the configuration is inspected by looking towards the sample surface from a position that is located behind the detector. Different tools assume that different strategies can be used and are perceived as differently convenient to enter details about coordinate system definitions. In this ELN users have to possibility to fill in what they assume is sufficient to define the coordinate system directions unambiguously. Software which works with this user input needs to offer parsing capabilities which detect conflicting input and warn accordingly.

Any of these values:

  • undefined

  • north

  • east

  • south

  • west

  • in

  • out

yaxis_direction: (optional) NX_CHAR

Direction of the positively pointing y-axis base vector of the detector space reference frame. We assume the configuration is inspected by looking towards the sample surface from a position that is located behind the detector. For further information consult also the help info for the xaxis_direction field.

Any of these values:

  • undefined

  • north

  • east

  • south

  • west

  • in

  • out

zaxis_direction: (optional) NX_CHAR

Direction of the positively pointing z-axis base vector of the detector space reference frame. We assume the configuration is inspected by looking towards the sample surface from a position that is located behind the detector. For further information consult also the help info for the xaxis_direction field.

Any of these values:

  • undefined

  • north

  • east

  • south

  • west

  • in

  • out

origin: (optional) NX_CHAR

Where is the origin of the detector space reference frame located. This is the location of Xd = 0, Yd = 0, Zd = 0. Assume regions-of-interest in this reference frame form a rectangle or cuboid. Edges are interpreted by inspecting the direction of their outer unit normals (which point either parallel or antiparallel) along respective base vector direction of the reference frame.

Any of these values:

  • undefined

  • front_top_left

  • front_top_right

  • front_bottom_right

  • front_bottom_left

  • back_top_left

  • back_top_right

  • back_bottom_right

  • back_bottom_left

gnomonic_projection_reference_frame: (optional) NXprocess

Details about the gnomonic projection reference frame.

reference_frame_type: (optional) NX_CHAR

Type of coordinate system/reference frame used for identifying positions in the gnomonic projection space Xg, Yg, Zg according to DOI: 10.1016/j.matchar.2016.04.008.

Any of these values:

  • undefined

  • right_handed_cartesian

  • left_handed_cartesian

xaxis_direction: (optional) NX_CHAR

Direction of the positively pointing “gnomomic” x-axis base vector when viewing how the diffraction pattern looks on the detector screen. We assume the configuration is inspected by looking towards the sample surface from a position that is located behind the detector. Different tools assume that different strategies can be used and are perceived as differently convenient to enter details about coordinate system definitions. In this ELN users have to possibility to fill in what they assume is sufficient to define the coordinate system directions unambiguously. Software which works with this user input needs to offer parsing capabilities which detect conflicting input and warn accordingly.

Any of these values:

  • undefined

  • north

  • east

  • south

  • west

  • in

  • out

yaxis_direction: (optional) NX_CHAR

Direction of the positively pointing “gnomomic” y-axis base vector when viewing how the diffraction pattern looks on the detector screen. We assume the configuration is inspected by looking towards the sample surface from a position that is located behind the detector. For further information consult also the help info for the xaxis_direction field.

Any of these values:

  • undefined

  • north

  • east

  • south

  • west

  • in

  • out

zaxis_direction: (optional) NX_CHAR

Direction of the positively pointing “gnomomic” z-axis base vector when viewing how the diffraction pattern looks on the detector screen. We assume the configuration is inspected by looking towards the sample surface from a position that is located behind the detector. For further information consult also the help info for the xaxis_direction field.

Any of these values:

  • undefined

  • north

  • east

  • south

  • west

  • in

  • out

origin: (optional) NX_CHAR

Is the origin of the gnomonic coordinate system located where we assume the location of the pattern centre. This is the location Xg = 0, Yg = 0, Zg = 0 according to reference DOI: 10.1016/j.matchar.2016.04.008.

Any of these values: undefined | in_the_pattern_centre

pattern_centre: (optional) NXprocess

Details about the definition of the pattern centre as a special point in the gnomonic projection reference frame.

xaxis_boundary_convention: (optional) NX_CHAR

From which border of the EBSP (in the detector reference frame) is the pattern centre’s x-position (PCx) measured? Keywords assume the region-of-interest is defined by a rectangle. We observe this rectangle and inspect the direction of the outer-unit normals to the edges of this rectangle.

Any of these values: undefined | top | right | bottom | left

xaxis_normalization_direction: (optional) NX_CHAR

In which direction are positive values for PCx measured from the specified boundary. Keep in mind that the gnomonic space is in virtually all cases embedded in the detector space. Specifically, the XgYg plane is defined such that it is embedded/laying inside the XdYd plane (of the detector reference frame). When the normalization direction is the same as e.g. the detector x-axis direction, we state that we effectively normalize in fractions of the width of the detector.

The issue with terms like width and height is that these degenerate if the detector region-of-interest is square-shaped. This is why we should better avoid talking about width and height but state how we would measure distances practically with a ruler and how we then measure positive distances.

Any of these values: undefined | north | east | south | west

yaxis_boundary_convention: (optional) NX_CHAR

From which border of the EBSP (in the detector reference frame) is the pattern centre’s y-position (PCy) measured? For further details inspect the help button of xaxis_boundary_convention.

Any of these values: undefined | top | right | bottom | left

yaxis_normalization_direction: (optional) NX_CHAR

In which direction are positive values for PCy measured from the specified boundary. For further details inspect the help button of xaxis_normalization_direction.

Any of these values: undefined | north | east | south | west

Hypertext Anchors

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

NXDL Source:

https://github.com/FAIRmat-Experimental/nexus_definitions/tree/fairmat/contributed_definitions/NXem_ebsd_conventions.nxdl.xml