Video-rate two-photon microendoscopy using second harmonic resonance fiber scanning.

We present a 2.5-mm-diameter resonant fiber scanning two-photon microendoscope with a 30-mm long forward-viewing rigid probe tip that enables video-rate imaging (20 Hz frame rate) suitable for hand-held imaging of tissues without motion artifacts. Higher-order harmonic oscillation scanning techniques are developed to significantly increase the frame rate compared to prior published fiber scanning microendoscopy designs while maintaining the field-of-view (∼125 µm), the optical resolution (1.