Overview of the system architecture of the PESCC. A focal-plane coronagraph (in this example a charge two vortex mask) diffracts the starlight out of the geometric pupil. A reference hole (RH) with polarizer is placed in the Lyot stop and lets a polarized reference beam through. The polarization state of the reference beam is pointing away from the page. Prior to the focal-plane, a Wollaston prism (or any other polarizing beamsplitter) splits the two orthogonal polarization states. The image with a polarization state that matches the RH polarizer has fringes that encode the wavefront information, while the orthogonal polarization state remains unmodulated by fringes.