Fig. 22: Optical performances of metalens-based endoscopes.

MTF diagrams at different AOIs of the traditional bulky lens endoscopy: (a) sagittal beams and (b) tangential beams, the orange dashed lines indicate the diffraction-limited MTF. c, d MTF diagrams at different AOIs (32 nm bandwidth) of the metalens endoscopy: (a) sagittal beams and (b) tangential beams, the orange dashed lines indicate the diffraction-limited MTF. The calculated MTFs for sagittal (e) and tangential (f) directions, respectively. For each wavelength, four lines are presented, corresponding to the four measured AOIs: 0°, 5°, 10°, and 15°. g The beam profile of the GRIN lens-based, the ball lens-based, and the metalens-based endoscopy. h–k Measured MTF diagrams at different depth points in the tangential and sagittal planes of the metalens-based endoscopy. l Measured (solid line) and simulated (dashed line) FWHM beam of the metalens and the refractive lens doublet as a function of the projection angle. a–d Reprinted with permission from ref. ²⁸³. Copyright 2024 De Gruyter. e, f Reprinted with permission from ref. ⁵⁴. Copyright 2023 Springer Nature. g–k Reprinted with permission from ref. ²⁸⁰. Copyright 2018 Springer Nature. l Reprinted with permission from ref. ²⁸⁵. Copyright 2023 Society of Photo-Optical Instrumentation Engineers