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The analysis of limits for multimode fibre imaging
Štolzová, Hana ; Kozubek, Michal (oponent) ; Dostál, Zbyněk (vedoucí práce)
Multimode fibers are the imaging tool of a significant potential in in-vivo microendoscopy. Recently, this method has seen a great development, thanks to the improvements in computational and other technologies, such as digital spatial light modulation. The aim of this work was to find specific limits of multimode fiber imaging and to present their computer simulation. The effect of illumination of the optical system containing the multimode fiber on its focussing and imaging capability was investigated. By analysing the data obtained from simulations and experiments, it has been found that the various levels of the Gaussian beam truncation by a projected multimode fiber numerical aperture results in a significant variance in the imaging capabilities of the system. Therefore, it seems that the multimode optical fibers are not a completely random medium. Observing the quality of the focusing, it was found that low truncated beams (beam-waist around 50% of the projected fiber numerical aperture), have the highest performance. This fact was verified by experimental measurements. Imaging using similarly truncated beams showed the best contrast transmission capability. However, when analysing the resolution of two pointlike objects, the beams with a significantly larger waist and a higher degree of truncation, of 100% or more, were most appropriate. The presence of this difference forces the person using the imaging system containing the multimode fiber to consider several aspects, in what environment the particular optical system will be used and which imaging quality indicator will be considered the most important.
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Advancements of Holographic endoscopy for in-vivo observations
Michálková, Ivana ; Tyc, Tomáš (oponent) ; Čižmár, Tomáš (vedoucí práce)
In recent years, a novel technique called holographic endoscopy has been developed and systematically improved. This unique technology utilizes a single hair-thin optical multimode fiber as a minimally invasive probe for deep tissue in vivo microscopy. A major milestone was reached last year when near-perfect focusing through a multimode fiber was achieved with the holographic endoscope. This breakthrough is significant for adapting scanning fluorescent microscopy techniques because it allows for more precise imaging with lower unwanted noise, thanks to the purity and fidelity of the focused excitation light. The achievement led to a new question: is it possible to generate more complex optical fields than diffraction-limited foci through the multimode fiber with comparable quality? This thesis aims to investigate this issue by producing Airy beams at the tip of the multimode fiber using the holographic endoscope setup. Two methods were used to produce Airy beams in this study: Fourier domain and direct field synthesis. The quality of the resulting beams was evaluated by comparing them to simulations. The propagation of the generated beams was also recorded and observed, and the potential of Fourier domain synthesis to control and modify the propagation characteristics of an Airy beam was explored. The analysis revealed that using the holographic endoscope setup, it is possible to create more complex optical fields, such as Airy beams, at the tip of a multimode fiber with an accuracy that matches the high-quality diffraction-limited foci produced in 2022. It is hoped that this work will serve as another stepping stone for the holographic endoscope's ability to work in microscopy regimes that utilize more complex light fields, such as structured illumination microscopy or stimulated emission depletion microscopy.
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The analysis of limits for multimode fibre imaging
Štolzová, Hana ; Kozubek, Michal (oponent) ; Dostál, Zbyněk (vedoucí práce)
Multimode fibers are the imaging tool of a significant potential in in-vivo microendoscopy. Recently, this method has seen a great development, thanks to the improvements in computational and other technologies, such as digital spatial light modulation. The aim of this work was to find specific limits of multimode fiber imaging and to present their computer simulation. The effect of illumination of the optical system containing the multimode fiber on its focussing and imaging capability was investigated. By analysing the data obtained from simulations and experiments, it has been found that the various levels of the Gaussian beam truncation by a projected multimode fiber numerical aperture results in a significant variance in the imaging capabilities of the system. Therefore, it seems that the multimode optical fibers are not a completely random medium. Observing the quality of the focusing, it was found that low truncated beams (beam-waist around 50% of the projected fiber numerical aperture), have the highest performance. This fact was verified by experimental measurements. Imaging using similarly truncated beams showed the best contrast transmission capability. However, when analysing the resolution of two pointlike objects, the beams with a significantly larger waist and a higher degree of truncation, of 100% or more, were most appropriate. The presence of this difference forces the person using the imaging system containing the multimode fiber to consider several aspects, in what environment the particular optical system will be used and which imaging quality indicator will be considered the most important.
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