Fourier ptychography and its extensions into 3D polarimetry (Invited Paper)

Due to the optically transparent nature of many biological specimens, high-resolution microscopic bio-imaging often requires the use of dyes or fluorescent labels which are not ideal for many in vivo experiments. By measuring the optical phase delay introduced by semi-transparent tissue, quantitative phase imaging methods like ptychography offer an effective label-free imaging platform. Many transparent specimens also exhibit alternative endogenous optical contrast mechanisms, such as anisotropic properties such as material birefringence and orientation. Here, we describe several relatively straightforward extensions of Fourier Ptychography that allow us to measure this phase-sensitive anisotropic information in 3D. We then extend the standard Fourier ptychography model and inverse solver to account for the vectorial nature of light, the sample, and the microscope itself. This allows us to remove polarization-dependent imaging system aberrations computationally. We demonstrate and validate large-area, high-resolution volumetric reconstructions of specimen refractive index, birefringence, and orientation for various biological samples.