.. _metadata_structure: Metadata structure ****************** The :class:`~.signal.BaseSignal` class stores metadata in the :attr:`~.signal.BaseSignal.metadata` attribute that has a tree structure. By convention, the nodes labels are capitalized and the leaves are not capitalized. When a leaf contains a quantity that is not dimensionless, the units can be given in an extra leaf with the same label followed by the "_units" suffix. The metadata structure is represented in the following tree diagram. The default units are given in parentheses. Details about the leaves can be found in the following sections of this chapter. :: ├── Acquisition_instrument │ ├── SEM │ │ ├── Detector │ │ │ └── EDS │ │ │ ├── azimuth_angle (º) │ │ │ ├── elevation_angle (º) │ │ │ ├── energy_resolution_MnKa (eV) │ │ │ ├── live_time (s) │ │ │ └── real_time (s) │ │ ├── beam_current (nA) │ │ ├── beam_energy (keV) │ │ ├── convergence_angle (mrad) │ │ ├── microscope │ │ └── tilt_stage (º) │ └── TEM │ ├── Detector │ │ ├── EDS │ │ │ ├── azimuth_angle (º) │ │ │ ├── elevation_angle (º) │ │ │ ├── energy_resolution_MnKa (eV) │ │ │ ├── live_time (s) │ │ │ └── real_time (s) │ │ └── EELS │ │ ├── collection_angle (mrad) │ │ ├── dwell_time (s) │ │ ├── exposure (s) │ │ └── spectrometer │ ├── acquisition_mode │ ├── beam_current (nA) │ ├── beam_energy (keV) │ ├── convergence_angle (mrad) │ ├── microscope │ └── tilt_stage (º) ├── General │ ├── date │ ├── original_filename │ ├── time │ └── title ├── Sample │ ├── description │ ├── elements │ ├── thickness │ └── xray_lines └── Signal ├── Noise_properties │ ├── Variance_linear_model │ │ ├── correlation_factor │ │ ├── gain_factor │ │ ├── gain_offset │ │ └── parameters_estimation_method │ └── variance ├── binned ├── record_by ├── signal_type └── signal_origin General ======= title type: Str A title for the signal, e.g. "Sample overview" original_filename type: Str If the signal was loaded from a file this key stores the name of the original file. time type: datetime.time The acquistion or creation time. date type: datetime.time The acquistion or creation date. Acquisition_instrument ====================== TEM --- Contain information relevant to transmission electron microscope signals. microscope type: Str The microscope model, e.g. VG 501 acquisition_mode type: Str Either 'TEM' or 'STEM' convergence_angle type: Float The beam convergence semi-angle in mrad. beam_energy type: Float The energy of the electron beam in keV beam_current type: Float The beam current in nA. dwell_time type: Float The dwell time in seconds. This is relevant for STEM acquisition exposure type: Float The exposure time in seconds. This is relevant for TEM acquistion. tilt_stage type: Float The tilt of the stage in degree. SEM --- Contain information relevant to scanning electron microscope signals. microscope type: Str The microscope model, e.g. VG 501 convergence_angle type: Float The beam convergence semi-angle in mrad. beam_energy type: Float The energy of the electron beam in keV beam_current type: Float The beam current in nA. tilt_stage type: Float The tilt of the stage in degree. Detector -------- All instruments can contain a "Detector" node with information about the detector used to acquire the signal. EDX and EELS detectors should follow the following strcture: EELS ^^^^ This node stores parameters relevant to electron energy loss spectroscopy signals. spectrometer type: Str The spectrometer model, e.g. Gatan 666 collection_angle type: Float The collection semi-angle in mrad. dwell_time type: Float The dwell time in seconds. This is relevant for STEM acquisition exposure type: Float The exposure time in seconds. This is relevant for TEM acquistion. EDS ^^^ This node stores parameters relevant to electron X-ray energy dispersive spectroscopy data. azimuth_angle type: Float The azimuth angle of the detector in degree. If the azimuth is zero, the detector is perpendicular to the tilt axis. elevation_angle type: Float The elevation angle of the detector in degree. The detector is perpendicular to the surface with an angle of 90. energy_resolution_MnKa type: Float The full width at half maximum (FWHM) of the manganese K alpha (Mn Ka) peak in eV. This value is used as a first approximation of the energy resolution of the detector. real_time type: Float The time spent to record the spectrum in second. live_time type: Float The time spent to record the spectrum in second, compensated for the dead time of the detector. Sample ====== description type: Str A brief description of the sample elements type: list A list of the symbols of the elements composing the sample, e.g. ['B', 'N'] for a sample composed of Boron and Nitrogen. xray_lines type: list A list of the symbols of the X-ray lines to be used for processing, e.g. ['Al_Ka', 'Ni_Lb'] for the K alpha line of Aluminum and the L beta line of Nickel. thickness type: Float The thickness of the sample in m. Signal ====== signal_type type: Str A term that describes the signal type, e.g. EDS, PES... This information can be used by HyperSpy to load the file as a specific signal class and therefore the naming should be standarised. Currently HyperSpy provides special signal class for photoemission spectroscopy, electron energy loss spectroscopy and energy dispersive spectroscopy. The signal_type in these cases should be respectively PES, EELS and EDS_TEM (EDS_SEM). signal_origin type: Str Either 'simulation' or 'experiment'. record_by type: Str One of 'spectrum' or 'image'. It describes how the data is stored in memory. If 'spectrum' the spectral data is stored in the faster index. Noise_properties ---------------- variance type: float or Signal instance. The variance of the data. It can be a float when the noise is Gaussian or a :class:`~.signal.BaseSignal` instance if the noise is heteroscedastic, in which case it must have the same dimensions as :attr:`~.signal.BaseSignal.data`. Variance_linear_model ^^^^^^^^^^^^^^^^^^^^^ In some cases the variance can be calculated from the data using a simple linear model: ``variance = (gain_factor * data + gain_offset) * correlation_factor``. gain_factor type: Float gain_offset type: Float correlation_factor type: Float parameters_estimation_method type: Str _Internal_parameters ==================== This node is "private" and therefore is not displayed when printing the :attr:`~.signal.BaseSignal.metadata` attribute. For example, an "energy" leaf should be accompanied by an "energy_units" leaf. Stacking_history ---------------- Generated when using :py:meth:`~.utils.stack`. Used by :py:meth:`~.signal.BaseSignal.split`, to retrieve the former list of signal. step_sizes type: list of int Step sizes used that can be used in split. axis type: int The axis index in axes manager on which the dataset were stacked. Folding ------- Constains parameters that related to the folding/unfolding of signals.