Improved fast Fourier solution based on transport of intensity equation

The phase recovery algorithm based on the transport of intensity equation uses the fast Fourier solution to calculate the phase from the acquired intensity, but the solution accuracy is not high, and there will be instability caused by zero points and minimum points. Aiming at this problem, An improved fast Fourier solution based on the intensity transfer equation is proposed. By finding a suitable constant value to replace the focused intensity value in the traditional formula, the initial guess solution of the phase is solved; the initial phase and the focused intensity form a new complex amplitude, and then a new intensity differential is obtained in the form of angular spectrum propagation, and then the new The intensity differential of is substituted into the phase solution formula to obtain a new phase, so as to iteratively optimize the phase; when the iteration converges, the exact solution of the phase can be obtained. This solution can bypass the instability caused by the zero point and the minimum value point and has the advantage of high precision. Keywords: Transport of intensity equation, Intensity differential, Iterative optimization, Angular spectrum propagation, Fast Fourier solution, phase recovery.