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2026-09-17 22:59:07 +09:00 · 2026-08-07 15:56:42 +09:00
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+%PROP2FOCUS propagate img to focus
+%   prop2focus uses 'phase detection autofocus' to find the focus
+%   
+%   img...          complex-valued object
+%   lam...          wavelength
+%   dx...           pixel size
+%
+%   optional parameters
+%   d_start...      initial guess of propagation distance to focus
+%   fov...          crop to fov and apodize edges
+
+%*-----------------------------------------------------------------------*
+%|                                                                       |
+%|  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 [ d, img_prop ] = prop2focus(img, lam, dx, varargin)
+import utils.*
+
+img_sz = size(img);
+
+% defaults
+fov = img_sz(1)*0.6;
+d_start = 0;
+
+% parse the variable input arguments vararg = cell(0,0);
+for ind = 1:2:length(varargin)
+    name = varargin{ind};
+    value = varargin{ind+1};
+    switch lower(name)
+        case 'd_start'
+            d_start = value;
+        case 'fov'
+            fov = value;
+        otherwise
+            error('Unknown parameter %s', name)
+    end
+end
+
+% prepare fov mask with apodization
+fov_mask = fftshift(fract_hanning_pad(img_sz, round(fov*1.2), round(fov)));
+img = img.*fov_mask;
+
+
+% create masks for autofocus
+mask = fract_hanning_pad(img_sz,round(img_sz(1)/5),round(img_sz(1)/5*0.9));
+
+mask1 = abs(shiftpp2(fftshift(mask),round(img_sz(1)/20),0));
+mask2 = abs(shiftpp2(fftshift(mask),-round(img_sz(1)/20),0));
+
+
+% minimize difference between the 2 images
+fun = @(d)sum(sum(abs(abs(fft2(ifftshift(fftshift(fft2(prop_free_nf(img,lam,d,dx))).*mask2)))-(abs(fft2(ifftshift(fftshift(fft2(prop_free_nf(img,lam,d,dx))).*mask1)))))));
+
+d = fminsearch(fun,d_start);
+
+% propagate to focus
+img_prop = prop_free_nf(img, lam, d, dx);
+
+
+end