Quantitative analysis of phase retrieval with the transport of intensity equation under low-light conditions

We demonstrate low-light quantitative phase imaging using the transport of intensity equation. The incident numbers of photons are experimentally determined using an optical power meter. Although the low-light phase imaging condition is vulnerable to noise, its application in astronomy and imaging of biological samples draws the attention of researchers. Low light is treated as a Poisson noise. We explore the method as an opportunity to study low-light phase imaging conditions and the possible potential to go toward ultra-low-light conditions. We have illustrated the same with the help of numerical simulation and experimental results.