nabu.preproc.ctf module¶
- class nabu.preproc.ctf.GeoPars(z1_vh=None, z2=None, pix_size_det=1e-06, wavelength=None, magnification=True, length_scale=1e-05, logger=None)[source]¶
Bases:
object
A class to describe the geometry of a phase contrast radiography with a source obtained by a focussing system, possibly astigmatic, which is at distance z1_vh from the sample. The detector is at z2 from the sample
- Parameters:
z1_vh (None, a float, or a sequence of two floats) – the source sample distance (meters), if None the parallel beam is assumed. If two floats are given then they are taken as the distance of the vertically focused source (horizontal line) and the horizontaly focused source (vertical line) for KB mirrors.
z2 (float) – the sample detector distance (meters).
pix_size_det (float or tuple) – pixel size in meters. If a tuple is passed, it is interpreted as (horizontal_size, vertical_size)
wavelength (float) – beam wave length (meters).
magnification (boolean defaults to True) – if false no magnification is considered
length_scale (float) – rescaling length scale, meant to avoid having too big or too small numbers. defaults to 10.0e-6
logger (Logger, optional) – A logging object
- class nabu.preproc.ctf.CTFPhaseRetrieval(shape, geo_pars, delta_beta, padded_shape='auto', padding_mode='reflect', translation_vh=None, normalize_by_mean=False, lim1=1e-05, lim2=0.2, use_rfft=False, fftw_num_threads=None, fft_num_threads=None, logger=None)[source]¶
Bases:
object
This class implements the CTF formula of [1] in its regularised form which avoids the zeros of unregularised_filter_denominator (unreg_filter_denom is the so here named denominator/delta_beta of equation 8).
References
[1] B. Yu, L. Weber, A. Pacureanu, M. Langer, C. Olivier, P. Cloetens, and F. Peyrin, “Evaluation of phase retrieval approaches in magnified X-ray phase nano computerized tomography applied to bone tissue”, Optics Express, Vol 26, No 9, 11110-11124 (2018)
Initialize a Contrast Transfer Function phase retrieval.
- Parameters:
geo_pars (GeoPars) – the geometry description
delta_beta (float) – the delta/beta ratio
padded_shape (str or tuple, optional) – Padded image shape, in the form (num_rows, num_columns) i.e (vertical, horizontal). By default, it is twice the image shape.
padding_mode (str) – Padding mode. It must be valid for the numpy.pad function
translation_vh (array, optional) – Shift in the form (y, x). It is used to perform a translation of the image before applying the CTF filter.
normalize_by_mean (bool) – Whether to divide the (padded) image with its mean before applying the CTF filter.
lim1 (float >0) – the regulariser strenght at low frequencies
lim2 (float >0) – the regulariser strenght at high frequencies
use_rfft (bool, optional) – Whether to use real-to-complex (R2C) FFT instead of usual complex-to-complex (C2C).
fftw_num_threads (bool or None or int, optional) – DEPRECATED - please use fft_num_threads instead.
fft_num_threads (bool or None or int, optional) – Number of threads to use for FFT. If a number is provided: number of threads to use for FFT. You can pass a negative number to use N - fft_num_threads cores.
logger (optional) – a logger object
- nabu.preproc.ctf.CtfFilter¶
alias of
CTFPhaseRetrieval