Object images and lens-based imaging results in Figs. 2, 3, and 5 were acquired using a biconvex lens (LB1630-A, Thorlabs). The lens-based microendoscope for comparison is home-built using the biconvex lens, and the identical multicore fiber (FIGH-06-300S, Fujikura) was used for the lensless microendoscope. The lens was used to demagnify and relay the scene by a factor of 980 μm/270 μm = 3.6 to relay the 980-μm-wide field of view to the multicore fiber’s image circle diameter of 270 μm. Note that the lens-based microendoscope does not use a microlens and therefore represents the best-case imaging performance with minimal optical aberrations.