Toward a miniature endomicroscope: pixelation-free and diffraction-limited imaging through a fiber bundle

Abstract

A fiber bundle is widely used for endoscopic imaging due to its direct image delivery capability. However, there exists an inevitable pixelation artifact, which limits spatial resolution to the diameter of individual fibers. In this Letter, we present a method that can eliminate this artifact and achieve diffraction-limited spatial resolution. We exploited the binary control of a digital micromirror device to measure a transmission matrix of a fiber bundle and to subsequently control mode mixing among individual fibers. In doing so, we achieved a 22 kHz scanning rate of a diffraction-limited focused spot and obtained fluorescence endoscope imaging (58 μm × 58 μm) with near video-rate (10.3 Hz) acquisition. Our study lays a foundation for developing an ultrathin and high-resolution microendoscope.

Ultrathin endoscopes based on multicore fibers and adaptive optics: a status review and perspectives

“…45,47,[58][59][60][61] The SLM plane can be placed in a plane that is conjugated with the MCF proximal end face, which was done in the early reports. 44,59 However, it is advantageous to offset the SLM from the conjugate plane, as in Fig.…”

Digital confocal microscopy through a multimode fiber

“…Once the fiber is calibrated, a light modulator is used to shape the input wavefront sent to the fiber, so that it creates spots or other known patterns at the opposite end; these spots or patterns are used to probe the sample. The scanning rate is currently in the kilohertz range in fastest implementations [19,21,24], yielding an effective frame rate of about 1Hz for highresolution scans. Most implementations to date were based on narrowband lasers, but extension to broadband pulsed lasers is underway [15,18].…”

“…Currently, two such imaging mechanisms have been successfully implemented: non-confocal fluorescence imaging [17,19,20,24] and wide field reflection imaging [21,22]. In these demonstrations, modal scrambling was compensated either on the way in or on the way out of the fiber, but not both at the same time.…”

“…Faster modulators can be used, such as digital micromirror devices or a combination of an acousto-optic deflector with a spatial light modulators. These have been shown to work for similar applications [14,19,24,34], and reach speeds over 20kHz.…”

Lensless two-photon imaging through a multicore fiber with coherence-gated digital phase conjugation

“…11,12 These devices scan light through many cores of the fiber to sample the image at each core position at the distal end. The resolution of core-by-core scanning MCF endoscopes is limited by the core spacing, 13 which must be kept sufficiently large to limit coreto-core coupling. 14,15 The resolution can be improved with a graded index (GRIN) lens that demagnifies the fiber facet; however, this improvement comes at the expense of a reduced field of view, and the resolution is still limited by core spacing.…”