Adaptive multiphoton endomicroscopy through a dynamically deformed multicore optical fiber using proximal detection

Abstract

This paper demonstrates multiphoton excited fluorescence imaging through a polarisation maintaining multicore fiber (PM-MCF) while the fiber is dynamically deformed using all-proximal detection. Single-shot proximal measurement of the relative optical path lengths of all the cores of the PM-MCF in double pass is achieved using a Mach-Zehnder interferometer read out by a scientific CMOS camera operating at 416 Hz. A non-linear least squares fitting procedure is then employed to determine the deformation-induced lateral shift of the excitation spot at the distal tip of the PM-MCF. An experimental validation of this approach is presented that compares the proximally measured deformation-induced lateral shift in focal spot position to an independent distally measured ground truth. The proximal measurement of deformation-induced shift in focal spot position is applied to correct for deformation-induced shifts in focal spot position during raster-scanning multiphoton excited fluorescence imaging.

Quantitative phase and polarization imaging through an optical fiber applied to detection of early esophageal tumorigenesis

“…55 Further, experimental findings using a highly spaced MCF for two-photon imaging are also encouraging. 56 These are promising indicators that experimental implementation of reflection-mode characterization is feasible. If successful, holographic endoscopy could enable retrieval of label-free quantitative phase-and polarization-resolved image metrics with the potential for application in early detection of esophageal tumors.…”

Characterizing Optical Fiber Transmission Matrices Using Metasurface Reflector Stacks for Lensless Imaging without Distal Access

“…In some cases this ambiguity reduces to an N -dimensional vector of sign errors (i.e. a vector ∈ {−1, 1} N ) for an N -pixel image, for example, when using MCF with low core-to-core coupling [17] or using an MMF that is near perfectly unitary (via the Autonne-Takagi matrix factorisation) [15]. In such cases, the ambiguity may be resolved by in situ optimisation assuming prior knowledge of the sample [17] or by treating the ambiguities as invariants of the fibre that can be measured in advance [15].…”

“…a vector ∈ {−1, 1} N ) for an N -pixel image, for example, when using MCF with low core-to-core coupling [17] or using an MMF that is near perfectly unitary (via the Autonne-Takagi matrix factorisation) [15]. In such cases, the ambiguity may be resolved by in situ optimisation assuming prior knowledge of the sample [17] or by treating the ambiguities as invariants of the fibre that can be measured in advance [15]. In practical cases, however, TMs are not unitary even in precision-manufactured MMF [18,19] because high-order modes, with more power concentrated in the fibre cladding, tend to exhibit power leakage at bends [20].…”

Two-photon lensless micro-endoscopy with in-situ wavefront correction

“…Currently, the solutions for constructing lensless endoscopes are based either on imaging fiber bundles [2] or wavefront-shaping [6][7][8][9][10]. Imaging fiber bundles consist of thousands of single-mode cores packed together, where each core functions as a single pixel.…”