Rapid quantitative phase imaging using the transport of intensity equation

A method for digital phase imaging is proposed. It requires the measurement of intensity in two adjacent planes orthogonal to the optical axis. The phase is subsequently recovered by a Fast Fourier Transform of the Transport of Intensity Equation. The algorithm can be used when the illuminating beam has an arbitrary intensity distribution and is limited by a rectangular aperture. The phase retrieval formulae take on an especially simple and numerically efficient form in the case of uniform illumination. Several simulated examples are presented to confirm the viability of the algorithm.