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101 lines
4.6 KiB
Matlab
101 lines
4.6 KiB
Matlab
% PROP_TILTED_PLANE Near field propagation into a surface tilted with respect to the beam
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%
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% [u_1, H, h_tilted] = prop_free_tilted_plane(u_0, z, lambda, pixel_size, ax=1)
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% returns the propagated wavefield
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% Inputs:
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% **u_0 stack of images
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% **rotation [alpha, beta] - along first, second axis [deg]
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% **lambda wavelenght [m]
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% **pixel_size pixel size [m] - in the rotated coordinates, ie. pixel size can be anisotropic
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% *returns*
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% ++u_1 propagated stack of images
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%
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% see utils.prop_free_tilted_plane for more details
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%*-----------------------------------------------------------------------*
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%| |
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%| Except where otherwise noted, this work is licensed under a |
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%| Creative Commons Attribution-NonCommercial-ShareAlike 4.0 |
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%| International (CC BY-NC-SA 4.0) license. |
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%| |
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%| Copyright (c) 2017 by Paul Scherrer Institute (http://www.psi.ch) |
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%| |
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%| Author: CXS group, PSI |
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%*-----------------------------------------------------------------------*
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% You may use this code with the following provisions:
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%
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% If the code is fully or partially redistributed, or rewritten in another
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% computing language this notice should be included in the redistribution.
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%
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% If this code, or subfunctions or parts of it, is used for research in a
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% publication or if it is fully or partially rewritten for another
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% computing language the authors and institution should be acknowledged
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% in written form in the publication: “Data processing was carried out
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% using the “cSAXS matlab package” developed by the CXS group,
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% Paul Scherrer Institut, Switzerland.”
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% Variations on the latter text can be incorporated upon discussion with
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% the CXS group if needed to more specifically reflect the use of the package
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% for the published work.
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%
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% A publication that focuses on describing features, or parameters, that
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% are already existing in the code should be first discussed with the
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% authors.
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%
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% This code and subroutines are part of a continuous development, they
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% are provided “as they are” without guarantees or liability on part
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% of PSI or the authors. It is the user responsibility to ensure its
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% proper use and the correctness of the results.
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function [fwd_propag, back_propag] = get_tilted_plane_propagators(img_sample, rotation, lambda, pixel_size)
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%% nearfield propagator into tilted plane
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import utils.*
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fwd_propag = @(x)x;
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back_propag = @(x)x;
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if all(rotation == 0)
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return
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end
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Npix = size(img_sample);
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if any(rotation(1:2)~= 0 )
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% provide tilt of the sample
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assert(sum(rotation(1:2)~=0) < 2, 'Only rotation along one axis is supported')
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ax = find(rotation(1:2)~=0);
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% propagation distance for each row / column to reach the tilted plane
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% extend * cosd(alpha) * tand(alpha)
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grid = ((-Npix(ax)/2+1):Npix(ax)/2)*pixel_size(min(ax,end)) * sind(rotation(ax));
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[~, H, h_tilted] = prop_free_nonparallel_plane(zeros(Npix(1:2), 'like', img_sample), grid, lambda, pixel_size, ax);
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% precalculate conjuged and transposed matrices
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H_t = H.'*1; % enforce copy
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Hc = conj(H);
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Hc_t = Hc.'*1;
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h_tilted_t = h_tilted'*1; % enforce copy
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%%%%%%%%%%%%%% propagate the image, see utils.prop_free_tilted_plane for more details %%%%%%%%%%%%%%%%%%%%%
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if ax == 1
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fwd_propag = @(x)(utils.mtimes_stack(h_tilted,ifft(H_t .* fft(x,[],2),[],2)));
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back_propag = @(x)(ifft(Hc_t.*fft(utils.mtimes_stack(h_tilted_t,x),[],2),[],2));
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else
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fwd_propag = @(x)(utils.mtimes_stack(ifft(H .* fft(x,[],1),[],1),h_tilted));
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back_propag = @(x)(ifft(Hc.*fft(utils.mtimes_stack(x,h_tilted_t),[],1),[],1));
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end
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end
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if rotation(3)~= 0
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% rotate image around beam axis
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fwd_propag = @(x)fwd_propag(utils.imrotate_ax_fft(x, rotation(3), 3));
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back_propag = @(x)back_propag(utils.imrotate_ax_fft(x, -rotation(3), 3));
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end
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end
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