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Acousto-optic lens microscopy: modelling and development

Evans, GJ; (2016) Acousto-optic lens microscopy: modelling and development. Doctoral thesis , UCL (University College London). Green open access

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Abstract

Understanding how sensory information is processed in neural net- works would mark a great leap forward for neuroscience. This has sparked a race to develop new technologies for performing 3D in-vivo brain imaging at high spatio-temporal resolution. A spherical acousto-optic lens (AOL) consisting of four acousto- optic deflectors (AODs) can rapidly steer and focus the laser beam of a two-photon microscope in 3D space. AOLs use acoustic waves to de- flect and focus an optical beam, enabling fast random-access imaging. This is well-suited to measuring sparsely-distributed brain activity us- ing fluorescent reporter dyes. However, to date AOL-based imaging has been performed using only linearly-chirped acoustic frequency drives. Here I develop new wavefront propagation theory and demon- strate AOL microscope imaging using nonlinearly-chirped drives for the first time. Nonlinear drives enable focal trajectories to be more closely fitted to structures of interest, offering new approaches to high-speed imaging of neuronal structures. A complete theoretical description of light propagation through an AOL has been missing, with only simplified principles to guide AOL design. To address this, I develop ray and wave models of op- tical transmission through an AOL. Using a ray model, I examine transmission efficiency and optimise the size of an AOL microscope’s imaging volume. With a wave-based model, I show an alternative de- sign of AOL using six AODs (6-AOD AOL) can theoretically correct spherical aberration, which is a major limitation of AOL microscopes. I further derive the drive equations needed by a 6-AOD AOL for ba- sic microscope operation, opening the possibility of high-speed 3D deep-tissue imaging with diffraction limited resolution.

Type: Thesis (Doctoral)
Title: Acousto-optic lens microscopy: modelling and development
Event: UCL
Open access status: An open access version is available from UCL Discovery
Language: English
Keywords: acousto-optic lens, microscopy, neuroscience, optics, functional imaging, two-photon
UCL classification: UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Life Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Life Sciences > Div of Biosciences
URI: http://discovery.ucl.ac.uk/id/eprint/1521116
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