1. A method for deriving a quantitative phase contrast tomographic image of a specimen, the method comprising steps of: a. illuminating the specimen with illuminating light characterized by a coherence length substantially shorter than a dimension of a feature of the specimen to be resolved; b. scanning a focus of the illuminating light to a plurality of depths within the specimen; c. spatially Fourier transforming light transmitted through the specimen at each of the plurality of depths to form a spatially Fourier transformed image; d. spatially modulating at least one of the phase and amplitude of a plurality of spatial frequency components of the spatially Fourier transformed image; e. detecting an intensity image of the specimen plane as modulated with respect to spatial frequency components and as interfered with an unscattered component of the illuminating light; f. deconvolving the intensity image at a plurality of spatially modulated instances to obtain a three-dimensional phase representation of the specimen at each of the plurality of distances relative to a fiducial plane; and g. further deconvolving a modeled point spread function from the three-dimensional phase representation to obtain at least one slice of the quantitative phase contrast tomographic image at a specified depth into the specimen.