# Source code for qpsphere.models

```
import numbers
import numpy as np
from .mod_mie import mie
from .mod_mie_avg import mie_avg
from .mod_proj import projection
from .mod_rytov import rytov
from .mod_rytov_sc import rytov_sc
model_dict = {"mie": mie,
"mie-avg": mie_avg,
"projection": projection,
"rytov": rytov,
"rytov-sc": rytov_sc,
}
#: available light-scattering models
available = sorted(list(model_dict.keys()))
[docs]def simulate(radius=5e-6, sphere_index=1.339, medium_index=1.333,
wavelength=550e-9, grid_size=(80, 80), model="projection",
pixel_size=None, center=None):
"""Simulate scattering at a sphere
Parameters
----------
radius: float
Radius of the sphere [m]
sphere_index: float
Refractive index of the object
medium_index: float
Refractive index of the surrounding medium
wavelength: float
Vacuum wavelength of the imaging light [m]
grid_size: tuple of int
Resulting image size in x and y [px]
model: str
Sphere model to use (see :const:`available`)
pixel_size: float or None
Pixel size [m]; if set to `None` the pixel size is
chosen such that the radius fits at least three to
four times into the grid.
center: tuple of floats or None
Center position in image coordinates [px]; if set to
None, the center of the image (grid_size - 1)/2 is
used.
Returns
-------
qpi: qpimage.QPImage
Quantitative phase data set
"""
if isinstance(grid_size, numbers.Integral):
# default to square-shape grid
grid_size = (grid_size, grid_size)
if pixel_size is None:
# select simulation automatically
rl = radius / wavelength
if rl < 5:
# a lot of diffraction artifacts may occur;
# use 4x radius to capture the full field
fact = 4
elif rl >= 5 and rl <= 10:
# linearly decrease towards 3x radius
fact = 4 - (rl - 5) / 5
else:
# not many diffraction artifacts occur;
# 3x radius is enough and allows to
# simulate larger radii with BHFIELD
fact = 3
pixel_size = fact * radius / np.min(grid_size)
if center is None:
center = (np.array(grid_size) - 1) / 2
model = model_dict[model]
qpi = model(radius=radius,
sphere_index=sphere_index,
medium_index=medium_index,
wavelength=wavelength,
pixel_size=pixel_size,
grid_size=grid_size,
center=center)
return qpi
```