Noninterferometric phase calculation for paraxial beams using intensity distribution

The noninterferometric calculation of the phase of an optical field has been investigated assuming that intensity distribution is given in a space region. The phase was treated as obeying the system of the transport of intensity equation and an eikonal one. Under paraxial approximation the solution of the last system has been found in the form of analytical expressions for a phase gradient. It has been shown that if the intensity is known then only finite branches for a phase gradient exists.