Bullseye

class abtem.transfer.Bullseye(num_spokes, spoke_width, num_rings, ring_width, semiangle_cutoff, energy=None, extent=None, gpts=None, sampling=None, edge_softness=0.0, corner_radius=0.0)

Bases: BaseAperture

Bullseye aperture.

The aperture is divided radially into num_rings periods, each consisting of an open annulus followed by an opaque gap; ring_width is the open fraction of each period. The open annulus width is ds = semiangle_cutoff * ring_width / (ring_width + num_rings - 1), and a ring_width of 1 gives a fully open disk. Opaque spokes cross all rings except the central disk; each spoke is a straight bar of constant linear width spoke_width * ds (in the same reciprocal-angle units as ds), not a wedge of constant angular width. Consequently spoke_width has no meaningful upper bound of 1 the way ring_width does: a fixed spoke_width blocks a larger angular fraction of rings closer to the center than rings farther out, so increasing it reduces transmission monotonically but not linearly, with rings saturating to fully blocked from the center outward. The central disk is never affected by spokes, so transmission approaches (but never reaches) “central disk only” as spoke_width grows.

Parameters:

• num_spokes (int) – Number of spokes.

• spoke_width (float) – Width of the opaque spokes, as a multiple of the open annulus width ds (see above) rather than an angular fraction. Must be non-negative; unlike ring_width, values greater than 1 are valid and simply widen the spokes further.

• num_rings (int) – Number of rings.

• ring_width (float) – Open fraction of each radial ring period. Must be in the interval (0, 1], where 1 gives a fully open disk.

• semiangle_cutoff (float) – The cutoff semiangle of the aperture [mrad].

• energy (float, optional) – Electron energy [eV]. If not provided, inferred from the wave functions.

• extent (float or two float, optional) – Lateral extent of wave functions [Å] in x and y directions. If a single float is given, both are set equal.

• gpts (two ints, optional) – Number of grid points describing the wave functions.

• sampling (two float, optional) – Lateral sampling of wave functions [1 / Å]. If ‘gpts’ is also given, will be ignored.

• edge_softness (float, optional) – Edge softness in mrads. Default value is 0.0.

• corner_radius (float, optional) – Corner radius in mrads. Default value is 0.0

__init__(num_spokes, spoke_width, num_rings, ring_width, semiangle_cutoff, energy=None, extent=None, gpts=None, sampling=None, edge_softness=0.0, corner_radius=0.0)

Methods

__init__(num_spokes, spoke_width, num_rings, ...)
apply(waves[, max_batch])
copy()	Make a copy.
ensemble_blocks([chunks])	Split the ensemble into an array of smaller ensembles.
generate_blocks([chunks])	Generate chunks of the ensemble.
match_grid(other[, check_match])	Match the grid to another object with a Grid.
show([max_angle])
to_diffraction_patterns([max_angle, gpts])	Converts the transfer function instance to DiffractionPatterns.

Attributes

accelerator	Accelerator object describing the acceleration energy.
angular_sampling	The sampling in scattering angles of the transfer function [mrad].
axes_metadata	List of AxisMetadata.
base_axes_metadata	List of AxisMetadata of the base axes.
base_shape	Shape of the base axes.
corner_radius	Corner radius [mrads]
distributions
edge_softness	Edge softness [mrads]
energy	Electron acceleration energy in electron volts.
ensemble_axes_metadata	Axes metadata describing the ensemble axes added to the waves when applying the transform.
ensemble_shape	The shape of the ensemble axes added to the waves when applying the transform.
extent	Extent of grid for each dimension in Ångstrom.
gpts	Number of grid points for each dimension.
grid	Simulation grid.
in_place	The array representing the waves may be modified in-place.
metadata	Metadata added to the waves when applying the transform.
num_rings	Number of rings.
num_spokes	Number of spokes.
nyquist_sampling	Nyquist sampling corresponding to the semiangle cutoff of the aperture [Å].
reciprocal_space_sampling	Reciprocal-space sampling in reciprocal Ångstrom.
ring_width	Open fraction of each radial ring period.
sampling	Grid sampling for each dimension in Ångstrom per grid point.
semiangle_cutoff	Semiangle cutoff of the aperture [mrad].
shape	Shape of the ensemble.
soft	True if the aperture has a soft edge
soft_edges	True if using soft edges
spoke_width	Width of the opaque spokes as a multiple of the open annulus width.
wavelength	Relativistic wavelength in Ångstrom.

property accelerator: Accelerator

Accelerator object describing the acceleration energy.

property angular_sampling: tuple[float, float]

The sampling in scattering angles of the transfer function [mrad].

property axes_metadata: AxesMetadataList

List of AxisMetadata.

property base_axes_metadata: list[AxisMetadata]

List of AxisMetadata of the base axes.

property base_shape: tuple[int, ...]

Shape of the base axes.

copy()

Make a copy.

Return type:

Self

property corner_radius: float

Corner radius [mrads]

property edge_softness: float

Edge softness [mrads]

property energy: float | None

Electron acceleration energy in electron volts.

property ensemble_axes_metadata: list[AxisMetadata]

Axes metadata describing the ensemble axes added to the waves when applying the transform.

ensemble_blocks(chunks=None)

Split the ensemble into an array of smaller ensembles.

Parameters:

chunks (iterable of tuples) – Block sizes along each dimension.

Return type:

Array

property ensemble_shape: tuple[int, ...]

The shape of the ensemble axes added to the waves when applying the transform.

property extent: tuple[float, float] | None

Extent of grid for each dimension in Ångstrom.

generate_blocks(chunks=1)

Generate chunks of the ensemble.

Parameters:

chunks (iterable of tuples) – Block sizes along each dimension.

Return type:

Generator[tuple[tuple[int, ...], tuple[slice, ...], ndarray], None, None]

property gpts: tuple[int, int] | None

Number of grid points for each dimension.

property grid: Grid

Simulation grid.

property in_place: bool

The array representing the waves may be modified in-place.

match_grid(other, check_match=False)

Match the grid to another object with a Grid.

property metadata: dict

Metadata added to the waves when applying the transform.

property num_rings: int

Number of rings.

property num_spokes: int

Number of spokes.

property nyquist_sampling: float

Nyquist sampling corresponding to the semiangle cutoff of the aperture [Å].

property reciprocal_space_sampling: tuple[float, float]

Reciprocal-space sampling in reciprocal Ångstrom.

property ring_width: float

Open fraction of each radial ring period.

property sampling: tuple[float, float] | None

Grid sampling for each dimension in Ångstrom per grid point.

property semiangle_cutoff: float | BaseDistribution

Semiangle cutoff of the aperture [mrad].

property shape: tuple[int, ...]

Shape of the ensemble.

property soft: bool

True if the aperture has a soft edge

property soft_edges: bool

True if using soft edges

property spoke_width: float

Width of the opaque spokes as a multiple of the open annulus width.

to_diffraction_patterns(max_angle=None, gpts=None)

Converts the transfer function instance to DiffractionPatterns.

Parameters:

• max_angle (float, optional) – The maximum diffraction angle in radians. If not provided, the maximum angle will be determined based on the self._max_semiangle_cutoff attribute of the instance. If neither max_angle nor self._max_semiangle_cutoff is available, a RuntimeError will be raised.

• gpts (int | tuple[int, int], optional) – The number of grid points in reciprocal space for performing Fourier Transform. If not provided, a default value of 128 will be used.

Returns:

The diffraction patterns obtained from the conversion.

Return type:

abtem.measurements.DiffractionPatterns

property wavelength: float

Relativistic wavelength in Ångstrom.