how do i simulate a 4f correlator

im trying to simulate a 4f correlator, and for some reason i cant get it to work. The code that simulates the 4f correlator is this:

     [xgrid ygrid]=meshgrid(1:1024);
     grid=(xgrid-512).^2 +(ygrid-512).^2;

     lens=exp((1i*pi*(pixsize^2)/((-f)*w)).*grid);
     move=fft2(exp((1i*pi*(pixsize^2)/(f*w)).*grid));

    img=padarray(h1cof,[pf pf]);
    bl1=ifftshift(ifft2(fft2(img).*move));
    al1=bl1.*lens;
    bh2=ifftshift(ifft2(fft2(al1).*move));
    ah2=bh2.*padarray(h2ft,[pf pf]);
    bl2=ifftshift(ifft2(fft2(ah2).*move));
    al2=bl2.*lens;
    rescof=ifftshift(ifft2(fft2(al2).*move));

where f is the focal length and w the wavelength

Answer 1

[eden london]

I think the problem might be due to scaling in the fourier domain. can't seem to solve it though..