LumiSpy metadata structure

LumiSpy extends the HyperSpy metadata structure with conventions for metadata specific to its signal types. Refer to the HyperSpy metadata documentation for general metadata fields.

The metadata of any signal objects is stored in the metadata attribute, which has a tree structure. By convention, the node labels are capitalized and the ones for 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.

Besides directly accessing the metadata tree structure, e.g. s.metadata.Signal.signal_type, the HyperSpy methods set_item(), has_item() and get_item() can be used to add to, search for and read from items in the metadata tree, respectively.

The luminescence specific 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. Note that not all types of leaves will apply to every type of measurement. For example, while parallel acquisition with a CCD is characterized by the central_wavelength, a serial acquisition with a PMT will require a start_wavelength and a step_size.

├── General
│   └── # see HyperSpy
├── Sample
│   └── # see HyperSpy
├── Signal
│   ├── signal_type
│   ├── quantity
│   └── # otherwise see HyperSpy
└── Acquisition_instrument
    ├── Laser / SEM / TEM
    │   ├── laser_type
    │   ├── model
    │   ├── wavelength (nm)
    │   ├── power (mW)
    │   ├── objective_magnification
    │   ├── Filter
    │   │   ├── filter_type
    │   │   ├── position
    │   │   ├── optical_density
    │   │   ├── cut_on_wavelength (nm)
    │   │   └── cut_off_wavelength (nm)
    │   └── # for SEM/TEM see HyperSpy
    ├── Spectrometer
    │   ├── model
    │   ├── acquisition_mode
    │   ├── entrance_slit_width (mm)
    │   ├── exit_slit_width (mm)
    │   ├── central_wavelength (nm)
    │   ├── start_wavelength (nm)
    │   ├── step_size (nm)
    │   ├── Grating
    │   │   ├── groove_density (grooves/mm)
    │   │   ├── blazing_angle (º)
    │   │   └── blazing_wavelength (nm)
    │   └── Filter
    │       ├── filter_type
    │       ├── position
    │       ├── optical_density
    │       ├── cut_on_wavelength (nm)
    │       └── cut_off_wavelength (nm)
    ├── Detector
    │   ├── detector_type
    │   ├── model
    │   ├── frames
    │   ├── integration_time (s)
    │   ├── saturation_fraction
    │   ├── binning
    │   ├── processing
    │   ├── sensor_roi
    │   └── pixel_size (µm)
    └── Spectral_image
        ├── mode
        ├── drift_correction_periodicity
        └── drift_correction_units (s)


See HyperSpy-Metadata-General.


See HyperSpy-Metadata-Sample.



type: string

String that describes the type of signal. The LumiSpy specific signal classes are summarized under Signal types.


type: string

The name of the quantity of the “intensity axis” with the units in round brackets if required, for example ‘Intensity (counts/s)’.

See HyperSpy-Metadata-Signal for additional fields.

Acquisition Instrument

Laser / SEM / TEM

For SEM or TEM see HyperSpy-Metadata-SEM or HyperSpy-Metadata-TEM.



type: string

The type of laser used, e.g. ‘HeCd’.


type: string

Model of the laser (branding by manufacturer).


type: float

Emission wavelength of the exciting laser in nm.


type: float

Measured power of the excitation laser in mW.


type: int

Magnification of the microscope objective used to focus the beam to the sample.


Information about additional filters entered into the lightpath before the sample. In case multiple filters are used, they should be numbered Filter_1, etc.


type: string

Type of filter (e.g. ‘optical density’, ‘short pass’, ‘long pass’, ‘bandpass’, ‘color’).


type: string

Position in the beam (e.g. ‘excitation’ vs. ‘detection’ in case of optical excitation).


type: float

Optical density in case of an intensity filter.


type: float

Cut on wavelength in nm in case of a long-pass or bandpass filter.


type: float

Cut off wavelength in nm in case of a short-pass or bandpass filter.


Contains information about the spectrometer, configuration and grating used for the measurement. In case multiple spectrometers are connected in series, they should be numbered Spectrometer_1, etc.


type: string

Model of the spectrometer (branding by manufacturer).


type: string

Acquisition mode (e.g. ‘Parallel dispersive’, versus ‘Serial dispersive’).


type: float

Width of the entrance slit in mm.


type: float

Width of the exit slit (serial acquisition) in mm.


type: float

Central wavelength during acquisition (parallel acquisition).


type: float

Start wavelength in nm (serial acquisition).


type: float

Step size in nm (serial acquisition).


Information of the dispersion grating employed in the measurement.


type: int

Density of lines on the grating in grooves/mm.


type: int

Angle in degree (º) that the grating is blazed at.


type: int

Wavelength that the grating blaze is optimized for in nm.


Information about additional filters entered into the lightpath after the sample. In case multiple filters are used, they should be numbered Filter_1, etc. See Filter above for details on items that may potentially be included.


Contains information about the detector used to acquire the signal. Contained leaves will differ depending on the type of detector.


type: string

The type of detector used to acquire the signal (CCD, PMT, StreakCamera, TCSPD).


type: string

The model of the used detector.


type: int

Number of frames that are summed to yield the total integration time.

integration_time (s)

type: float

Time over which the signal is integrated. In case multiple frames are summed, it is the total exposure time. In case of serial acquisition, it is the dwell time per data point.


type: float

Fraction of the signal intensity compared with the saturation threshold of the CCD.


type: tuple of int

A tuple that describes the binning of a parallel detector such a CCD on readout in x and y directions.


type: string

Information about automatic processing performed on the data, e.g. ‘dark subtracted’.


type: tuple of int

Tuple of length 2 or 4 that specifies range of pixels on a detector that are read out: (offset x, offset y, size x, size y) for a 2D array detector and (offset, size) for a 1D line detector.


type: float or tuple of float

Size of a pixel in µm. Tuple of length 2 (width, height), when the pixel is not square.


Contains information about mapping parameters, such as step size, drift correction, etc.


type: string

Mode of the spectrum image acquisition such as ‘Map’ or ‘Linescan’.


type: int/float

Periodicity of the drift correction in specified units (standard s).


type: string

Units of the drift correction such as ‘s’, ‘px’, ‘rows’.