What is the wavelength? And can you post the code used to calculate the scattering in both cases?

from holopy.

The wavelength I am using is 465 nm for a sphere with a radius 7.5 micrometres.
I used this code to simulate scattering pattern just I changed the z parameter in both cases:

import holopy as hp
from holopy.scattering import calc_holo, Sphere
from holopy.scattering import Mie
import matplotlib.pyplot as plt

sphere = Sphere(n=1.6, r=7.5, center=(100.0, 100.0, 1000.0))## (Refractive index, Radius in microns, Position in micron)

medium_index = 1.33
illum_wavelen = 0.465
illum_polarization = (1.0, 1.0)
detector = hp.detector_grid(shape=200, spacing=1.0)

Create the scattering theory object

mie = Mie()

holo = calc_holo(detector, sphere, medium_index, illum_wavelen,
illum_polarization, theory='auto')
hp.show(holo)

from holopy.

@BnM-BnM sorry for the late reply. Because you're calculating the hologram at a distance many times the wavelength, you can use the far-field approximations to the Mie solutions to calculate the hologram, which will avoid the numerical issues you're seeing, and save time and computational effort.

import holopy as hp
from holopy.scattering import calc_holo, Sphere
from holopy.scattering import Mie
import matplotlib.pyplot as plt

sphere = Sphere(n=1.6, r=7.5, center=(100.0, 100.0, 1500.0))## (Refractive index, Radius in microns, Position in micron)

medium_index = 1.33
illum_wavelen = 0.465
illum_polarization = (1.0, 1.0)
detector = hp.detector_grid(shape=200, spacing=1.0)

# use far-field solutions
far_field_mie = Mie(compute_escat_radial=False, full_radial_dependence=False)

# make sure to specify the far-field theory; don't use 'auto' here
holo = calc_holo(detector, sphere, medium_index, illum_wavelen,illum_polarization, theory=far_field_mie)

hp.show(holo)

from holopy.

Leaving issue open because documentation should be updated to reflect this advice.

from holopy.