Methods and apparatus for three-dimensional imaging of a sample. A source is provided of a beam of substantially collimated light characterized by a temporally dependent spectrum. The beam is focused in a plane characterized by a fixed displacement along the propagation axis of the beam, and scattered light from the sample is superposed with a reference beam derived from the substantially collimated source onto a focal plane detector array to provide an interference signal. A forward scattering model is derived relating measured data to structure of an object to allow solution of an inverse scattering problem based upon the interference signal so that a three-dimensional structure of the sample may be inferred in near real time.