holopy.scattering package

Scattering calculations

The scattering package provides objects and methods to define scatterer geometries, and theories to compute scattering from specified geometries. Scattering depends on holopy.core, and certain scattering theories may require external scattering codes.

The HoloPy scattering module is used to:

Describe geometry as a scatterer object
Define the result you want as a xarray.DataArray xarray.DataArray
Calculate scattering quantities with an theory appropriate for your scatterer

Subpackages

Submodules

holopy.scattering.errors module

Exceptions used in scatterpy module. These are separated out from the other exceptions in other parts of HoloPy to keep things modular.

exception AutoTheoryFailed(scatterer): Bases: Exception

exception InvalidScatterer(scatterer, message): Bases: Exception

exception MissingParameter(parameter_name): Bases: Exception

exception MultisphereFailure: Bases: Exception

exception OverlapWarning(scatterer, overlaps): Bases: UserWarning

exception ParameterSpecificationError: Bases: Exception

exception TheoryNotCompatibleError(theory, scatterer, reason=None): Bases: Exception

exception TmatrixFailure(logfilestr): Bases: Exception

holopy.scattering.imageformation module

class ImageFormation(scattering_theory)

Bases: HoloPyObject

Calculates fields, holograms, intensities, etc.

calculate_cross_sections(scatterer, medium_wavevec, medium_index, illum_polarization)

calculate_scattered_field(scatterer, schema)

Parameters:: scatterer (scatterer object) – (possibly composite) scatterer for which to compute scattering
Returns:: e_field – scattered electric field
Return type:: VectorGrid

calculate_scattering_matrix(scatterer, schema)

Compute scattering matrices for scatterer

Parameters:: scatterer (holopy.scattering.scatterer object) – (possibly composite) scatterer for which to compute scattering
Returns:: scat_matr – Scattering matrices at specified positions
Return type:: Marray

get_wavevec_from(schema)

select_scatterer_by_illumination(scatterer, illum)

holopy.scattering.interface module

Base class for scattering theories. Implements python-based calc_intensity and calc_holo, based on subclass’s calc_field

calc_cross_sections(scatterer, medium_index=None, illum_wavelen=None, illum_polarization=None, theory='auto')

Calculate scattering, absorption, and extinction cross sections, and asymmetry parameter <cos heta>.

Parameters:

scatterer (scatterer object) – (possibly composite) scatterer for which to compute scattering
medium_index (float or complex) – Refractive index of the medium in which the scatter is imbedded
illum_wavelen (float or ndarray(float)) – Wavelength of illumination light. If illum_wavelen is an array result will add a dimension and have all wavelengths
theory (theory object (optional)) – Scattering theory object to use for the calculation. This is optional if there is a clear choice of theory for your scatterer. If there is not a clear choice, calc_cross_sections will error out and ask you to specify a theory

Returns:

cross_sections – Dimensional scattering, absorption, and extinction cross sections, and <cos theta>

Return type:

array (4)

calc_field(detector, scatterer, medium_index=None, illum_wavelen=None, illum_polarization=None, theory='auto')

Calculate the scattered fields from a scatterer illuminated by a reference wave.

Parameters:

detector (xarray object) – The detector points and calculation metadata used to calculate the scattered fields.
scatterer (scatterer object) – (possibly composite) scatterer for which to compute scattering
medium_index (float or complex) – Refractive index of the medium in which the scatter is imbedded
illum_wavelen (float or ndarray(float)) – Wavelength of illumination light. If illum_wavelen is an array result will add a dimension and have all wavelengths
theory (theory object (optional)) – Scattering theory object to use for the calculation. This is optional if there is a clear choice of theory for your scatterer. If there is not a clear choice, calc_field will error out and ask you to specify a theory

Returns:

e_field – Calculated hologram from the given distribution of spheres

Return type:

Vector object

calc_holo(detector, scatterer, medium_index=None, illum_wavelen=None, illum_polarization=None, theory='auto', scaling=1.0)

Calculate hologram formed by interference between scattered fields and a reference wave

Parameters:

detector (xarray object) – The detector points and calculation metadata used to calculate the hologram.
scatterer (scatterer object) – (possibly composite) scatterer for which to compute scattering
medium_index (float or complex) – Refractive index of the medium in which the scatter is imbedded
illum_wavelen (float or ndarray(float)) – Wavelength of illumination light. If illum_wavelen is an array result will add a dimension and have all wavelengths
theory (theory object (optional)) – Scattering theory object to use for the calculation. This is optional if there is a clear choice of theory for your scatterer. If there is not a clear choice, calc_holo will error out and ask you to specify a theory
scaling (scaling value (alpha) for amplitude of reference wave)

Returns:

holo – Calculated hologram from the given distribution of spheres

Return type:

xarray.DataArray

calc_intensity(detector, scatterer, medium_index=None, illum_wavelen=None, illum_polarization=None, theory='auto')

Calculate intensity from the scattered field at a set of locations

Parameters:

detector (xarray object) – The detector points and calculation metadata used to calculate the intensity.
scatterer (scatterer object) – (possibly composite) scatterer for which to compute scattering
medium_index (float or complex) – Refractive index of the medium in which the scatter is imbedded
illum_wavelen (float or ndarray(float)) – Wavelength of illumination light. If illum_wavelen is an array result will add a dimension and have all wavelengths
theory (theory object (optional)) – Scattering theory object to use for the calculation. This is optional if there is a clear choice of theory for your scatterer. If there is not a clear choice, calc_intensity will error out and ask you to specify a theory

Returns:

inten – scattered intensity

Return type:

xarray.DataArray

calc_scat_matrix(detector, scatterer, medium_index=None, illum_wavelen=None, theory='auto')

Compute farfield scattering matrices for scatterer

Parameters:

detector (xarray object) – The detector points and calculation metadata used to calculate the scattering matrices.
scatterer (holopy.scattering.scatterer object) – (possibly composite) scatterer for which to compute scattering
medium_index (float or complex) – Refractive index of the medium in which the scatter is imbedded
illum_wavelen (float or ndarray(float)) – Wavelength of illumination light. If illum_wavelen is an array result will add a dimension and have all wavelengths
theory (theory object (optional)) – Scattering theory object to use for the calculation. This is optional if there is a clear choice of theory for your scatterer. If there is not a clear choice, calc_scat_matrix will error out and ask you to specify a theory

Returns:

scat_matr – Scattering matrices at specified positions

Return type:

Marray

determine_default_theory_for(scatterer)

finalize(detector, result)

interpret_theory(scatterer, theory='auto')

prep_schema(detector, medium_index, illum_wavelen, illum_polarization)

scattered_field_to_hologram(scat, ref)

Calculate a hologram from an E-field

Parameters:

scat (VectorGrid) – The scattered (object) field
ref (xarray[vector]]) – The reference field

validate_scatterer(scatterer)