Abstract: Systems and methods for quantitative phase imaging are disclosed. In one embodiment, a method includes acquiring a through-focal series of defocused images of an object illuminated with a partially coherent light source; calculating a plurality of estimates of longitudinal intensity derivatives for respective fittings of the series of defocused images; recovering a phase estimate for each respective estimate of the longitudinal intensity derivative by solving a transport of intensity (TIE) equation; filtering the recovered phase estimates to produce component parts of an overall phase estimate; and forming an overall phase image by addition of the filtered phase estimates.