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ptycho/utils/get_tilted_plane_propagators.m

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