“…In all experiments, prior to measuring and correcting aberrations of the GRIN lens, system aberrations from all other components of the microendoscope were obtained by measuring the 3D point spread function of 200-nm-diameter fluorescent beads and then a phase retrieval procedure based on the Gerchberg-Saxon algorithm [5] and corrected with the DM. Intrinsic aberrations of the GRIN lens were then measured via direct wavefront sensing [6,7]. An isolated 2-µm-diameter fluorescent bead on a microscope slide was excited with widefield illumination, and the wavefront aberrations experienced by its fluorescence through the GRIN lens were measured with a Shack-Hartmann sensor (Fig.…”