GS algorithm phase retrieval: when the amplitudes of the image and Fourier planes are well defined, the phase information can be found
Starting from a random phase mask, perform FFT and IFFT back and forth. During this procedure, enforce the measured amplitudes from the image plane and the Fourier plane. The phase retrieval happens because the results of FFT and IFFT are in complex form, so by considering the real and imaginary parts of the result, we can update the phase.





