Multifocal multiphoton endoscope

We report a miniaturized resonant/non-resonant multi-fiber raster scanner that is paired with a gradient-index lens assembly to achieve a compact and flexible multifocal multiphoton endoscope capable of longitudinal parallel image acquisition. Multiphoton images are obtained simultaneously at three axial depths, separated by ≥4.8 μm, by incorporating three axially offset double clad optical fibers into the miniaturized scanner. The fabricated endoscope has an outer diameter of 3 mm, a rigid length of 4 cm, and acquires images at 4 frames/s per focal plane, with lateral and axial resolutions for two-photon imaging of 0.8 and 10 μm, respectively.