Transport of intensity equation based photon-counting phase imaging

In low light conditions, such as in astronomy and non-invasive bio-imaging applications, the imaging performance is mostly degraded due to noise. In this paper, we demonstrate a transport of intensity equation based technique that uses photon-counting phase imaging. To achieve the phase imaging in a photon starved condition, a method proposed by Paganin et al. [J. Micros. 214, 51 (2004)] has been used. The method uses the fact that the magnitude of the wavefront curvature determines the quality of the recovered phase image for a given noise level and defocus distance. The effectiveness of the proposed method has been illustrated through simulations and experimental results using inexpensive partially coherent illumination. The study can find applications in non-invasive phase imaging. (C) 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement