simulation of fully developed speckle pattern

speckle_pattern.m

L = 400;
D = 80;
speckleSize = L/D
img = zeros(L, L);
pad = L/2; % padding
for k=pad-D:D+pad
  for l=pad-D:D+pad
    if abs((pad-k)^2+(pad-l)^2) < D^2/4
      img(k,l) = exp(unifrnd(-pi,pi));
    end
  end
end
mfft = fft2(img);
img = mfft.*conj(mfft);
subimg = img(20:380, 20:380);
figure; imshow(subimg, []);