Central band suppression using non-linear filters

[paulmueller]

This is interesting when the sideband filter is large and thus the interference pattern becomes visible in the phase/amplitude data.

literature e.g.

• Pavillon et al. 2009
  https://doi.org/10.1364/AO.48.00H186

[paulmueller]

This could be combined with a sinc filter:

cutoff = 1/fsize/2
afilter = 2 * cutoff * np.sinc(2 * cutoff * fx) * np.sinc(2 * cutoff * fy)
afilter /= afilter.max()