PHASE RETRIEVAL FROM TWO DEFOCUSED IMAGES BY THE TRANSPORT OF INTENSITY EQUATION FORMALISM WITH FAST FOURIER TRANSFORM.

The problem of phase retrieval from intensity measurements plays an important role in many fields of physical research, e.g. optics, electron and x-ray microscopy, crystallography, diffraction tomography and others. In practice the recorded images contain information only on the intensity distribution I(x,y) = {Psi}*{Psi} = {vert_bar}A{vert_bar}{sup 2} of the imaging wave function {Psi} = A*exp(-i{var_phi}) and the phase information {var_phi}(x,y) is usually lost. In general, the phase problem can be solved either by special holographic/interferometric methods, or by non-interferometric approaches based on intensity measurements in far Fraunhofer zone or in the Fresnel zone at two adjacent planes orthogonal to the optical axis. The latter approach uses the transport-of-intensity equation (TIE) formalism, introduced originally by Teague [1] and developed later in [2]. Applications of TIE to nonmagnetic materials and magnetic inductance mapping were successfully made in [3,4]. However, this approach still needs further improvement both in mathematics and in practical solutions, since the result is very sensitive to many experimental parameters