2.3.3.2.23. NXtomo¶
Status:
application definition, extends NXobject
Description:
This is the application definition for x-ray or neutron tomography raw data. ...
This is the application definition for x-ray or neutron tomography raw data.
In tomography a number of dark field images are measured, some bright field images and, of course the sample. In order to distinguish between them images carry a image_key.
Symbols:
These symbols will be used below to coordinate datasets with the same shape.
nFrames: Number of frames
xSize: Number of pixels in X direction
ySize: Number of pixels in Y direction
- Groups cited:
NXdata, NXdetector, NXentry, NXinstrument, NXmonitor, NXsample, NXsource
Structure:
entry: (required) NXentry
start_time: (optional) NX_DATE_TIME ⤆
end_time: (optional) NX_DATE_TIME ⤆
definition: (required) NX_CHAR ⤆
Official NeXus NXDL schema to which this file conforms ...
Official NeXus NXDL schema to which this file conforms
Obligatory value:
NXtomo
instrument: (required) NXinstrument ⤆
detector: (required) NXdetector ⤆
data: (required) NX_INT (Rank: 3, Dimensions: [nFrames, xSize, ySize])
image_key: (required) NX_INT (Rank: 1, Dimensions: [nFrames]) ⤆
In order ...
In order to distinguish between sample projections, dark and flat images, a magic number is recorded per frame. The key is as follows:
projection = 0
flat field = 1
dark field = 2
invalid = 3
x_pixel_size: (optional) NX_FLOAT {units=NX_LENGTH} ⤆
y_pixel_size: (optional) NX_FLOAT {units=NX_LENGTH} ⤆
distance: (optional) NX_FLOAT {units=NX_LENGTH} ⤆
Distance between detector and sample
x_rotation_axis_pixel_position: (optional) NX_FLOAT
y_rotation_axis_pixel_position: (optional) NX_FLOAT
Descriptive name of sample
rotation_angle: (required) NX_FLOAT (Rank: 1, Dimensions: [nFrames]) {units=NX_ANGLE} ⤆
In practice this axis is always aligned along one pixel direction on the d ...
In practice this axis is always aligned along one pixel direction on the detector and usually vertical. There are experiments with horizontal rotation axes, so this would need to be indicated somehow. For now the best way for that is an open question.
x_translation: (optional) NX_FLOAT (Rank: 1, Dimensions: [nFrames]) {units=NX_LENGTH} ⤆
y_translation: (optional) NX_FLOAT (Rank: 1, Dimensions: [nFrames]) {units=NX_LENGTH}
z_translation: (optional) NX_FLOAT (Rank: 1, Dimensions: [nFrames]) {units=NX_LENGTH}
control: (optional) NXmonitor ⤆
Hypertext Anchors¶
List of hypertext anchors for all groups, fields, attributes, and links defined in this class.