Optical fiber bundles: Ultra-slim light field imaging probes

Abstract

Optical fiber bundle microendoscopes are widely used for visualizing hard-to-reach areas of the human body. These ultrathin devices often forgo tunable focusing optics because of size constraints and are therefore limited to two-dimensional (2D) imaging modalities. Ideally, microendoscopes would record 3D information for accurate clinical and biological interpretation, without bulky optomechanical parts. Here, we demonstrate that the optical fiber bundles commonly used in microendoscopy are inherently sensitive to depth information. We use the mode structure within fiber bundle cores to extract the spatio-angular description of captured light rays—the light field—enabling digital refocusing, stereo visualization, and surface and depth mapping of microscopic scenes at the distal fiber tip. Our work opens a route for minimally invasive clinical microendoscopy using standard bare fiber bundle probes. Unlike coherent 3D multimode fiber imaging techniques, our incoherent approach is single shot and resilient to fiber bending, making it attractive for clinical adoption.

Establishment of a guided, in vivo, multi-channel, abdominal, tissue imaging approach

“…Unfortunately, it is currently not possible to acquire three dimensional z-stacks with our setup or to visualize cell structures in deeper layers. Recently, Orth et al demonstrated the feasibility of depth visualization in a single exposure by analyzing the transmitted light field through a fiber-bundle 28 . This would allow to visualized tissue down to approximately 80 µm depth with the option of refocusing.…”

Overcoming the Abbe Diffraction Limit Using a Bundle of Metal‐Coated High‐Refractive‐Index Sapphire Optical Fibers

“…Both parameters are normalized by the operation wavelength, which is assumed to be λ = 600 µm and corresponds to the lowest possible operation frequency ν ≈ 0.5 THz, as discussed in the previous section. The proposed approach of fiber bundle resolution estimation is quite general and can be used with any disordered fiber bundle, regardless of its operation frequency, [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] as well as with a disordered wire medium. [25][26][27][28][29] Thereby, using only the geometrical data for the underlying lattice of fiber positions, one can predict the bundle spatial resolution, assuming that there is no cross talk between fibers.…”

“…With a rapid progress in fiber optics, fiber bundles attract increasing attention in imaging and sensing applications. [1][2][3] Particularly, bundles of fibers (either surrounded with a lower-refractive-index dielectric or metal-coated) already found their applications in such diverse areas as endoscopic biomedical imaging, [4][5][6] thermography, [7] photoacoustic, [8] fluorescence, [9] twophoton, [10] and Raman microscopy, [11] holography, [12] low-coherence interferometry and depth-resolved imaging, [13][14][15] and embedded equipment (including biomedical). [16][17][18][19] The high demand for compliant and small form factor optical systems capable of high resolution imaging and sensing pushes further development of the novel materials, designs, image processing algorithms, and fabrication techniques, aimed at enhancing of the spatial resolution [20] and reduction of imaging artifacts inherent to the fiber bundles.…”

Phonon imaging in 3D with a fibre probe

“…On the other hand, a single multi-mode fibre is less dependent on scanning since each mode within the fibre acts as a pixel; the caveat is that mode dispersion scrambles the image information and must be empirically compensated 8 . Once unscrambled, the multi-mode fibre empowers lensless endoscopy with qualities such as high numerical aperture (NA) 9 , wide field 10 , 3D imaging 11 and even super-resolution 12 .…”