Extended field-of-view ultrathin microendoscopes with built-in aberration correction for high-resolution imaging with minimal invasiveness

We present a novel approach to correct optical aberrations in ultrathin gradient-index rod lens-based endoscopes using microfabricated aspherical lenses. Corrected microendoscopes have up to 9 folds larger field-of-view compared to uncorrected probes. Using extended field-of-view ( eFOV ) microendoscopes, we report two-photon imaging of GCaMP6 signals in the mouse hippocampus in vivo with unprecedented combination of high spatiotemporal resolution and minimal invasiveness.