000203608 001__ 203608
000203608 005__ 20190601123804.0
000203608 0247_ $$2doi$$a10.5075/epfl-thesis-6457
000203608 02470 $$2urn$$aurn:nbn:ch:bel-epfl-thesis6457-4
000203608 02471 $$2nebis$$a10286727
000203608 037__ $$aTHESIS
000203608 041__ $$aeng
000203608 088__ $$a6457
000203608 245__ $$aOptical microscopy for imaging through scattering media
000203608 269__ $$a2014
000203608 260__ $$bEPFL$$c2014$$aLausanne
000203608 336__ $$aTheses
000203608 502__ $$aProf. O. Martin (président) ;  Prof. D. Psaltis, Y. Pu (directeurs) ;  Prof. C.-L. Hsieh,   Prof. C. Moser,   Prof. K. Stankovic (rapporteurs)
000203608 520__ $$aOptical microscopy has been widely used in the life sciences and biological research for several decades. It possesses many advantages over x-ray radiography, computed tomography, ultrasound imaging and magnetic resonance imaging, in terms of being low cost, high resolution, harmless and capable of multiple contrast mechanism, etc. However, the weakness of optical microscopy is the inability to perform deep tissue imaging. Owing to the short wavelength of optical waves, it experiences much more scattering than longer waves in inhomogeneous materials such as biological tissues. Scattering scrambles the wavefront and limits the penetration depth of optical microscopy to only hundreds of microns. We explore in this thesis, novel optical approaches to image through scattering media. There are two main categories of the state of art techniques: imaging with ballistic photons, which requires separation of ballistic photons from the sneak or multiple scattered ones; and imaging with scattered photons, which relies on manipulation of the scattered photons according to the specific scattering properties. We primarily focus on the second category in this thesis. Taking advantage of the reversibility of light, phase conjugation has a long history in aberration compensation. A deterministic wave is incident on a scattering medium and results in a random scattered field. If we record the full information of the scattered field (amplitude and phase) and generate a phase conjugated replica of it, the phase conjugated wave can follow the same path and reconstruct the original deterministic wave after passing back through the scattering medium. In this work, phase conjugation is achieved using digital method, called digital phase conjugation. The scattered field is recorded through digital holography, and a spatial light modulator is applied to construct the phase conjugated wave. Second harmonic radiation imaging probes are used as the original light source, rendering the generation of a focus behind the scattering medium. The memory effect, which indicates the correlation between speckles with different incident angles, is exploited to move the focus around and obtain three-dimensional scanning microscopy behind scattering medium. Speckle scanning microscopy is the second method demonstrated in this thesis for imaging through turbid media. In contrast to digital phase conjugation, which requires access from both sides of the scatterers to measure the scattered field, in speckle scanning microscopy, excitation and collection can be achieved from the same side. The specific scattering events are not taken into account, instead, the statistic property of the scatterers plays a major role. This technique makes full use of two facts: 1. The statistically averaged autocorrelation of speckle fields approaches a delta function; 2. When a speckle pattern scans across a fluorescence object, the collected fluorescence intensity is proportional to the convolution of the speckle field and the object. Linking these two facts with delicate calculation, we can eventually minimize the influence of the speckle, and reconstruct two-dimensional images of objects behind turbid medium. Encouraged by the success of two-dimensional speckle scanning microscopy, we investigate more advanced possibilities by simulation, including three-dimensional speckle scanning and reference based speckle scanning techniques. [...]
000203608 6531_ $$adigital phase conjugation
000203608 6531_ $$asecond harmonic radiation imaging probes
000203608 6531_ $$aspeckle scanning microscopy
000203608 6531_ $$awavefront shaping
000203608 6531_ $$amultiphoton microscopy
000203608 6531_ $$aintra-cochlear imaging
000203608 700__ $$0(EPFLAUTH)198550$$g198550$$aYang, Xin
000203608 720_2 $$0(EPFLAUTH)174684$$g174684$$edir.$$aPsaltis, Demetri
000203608 720_2 $$0(EPFLAUTH)188551$$g188551$$edir.$$aPu, Ye
000203608 8564_ $$uhttps://infoscience.epfl.ch/record/203608/files/EPFL_TH6457.pdf$$zn/a$$s6397555$$yn/a
000203608 909C0 $$xU11723$$0252333$$pLO
000203608 909CO $$pthesis$$pthesis-bn2018$$pDOI$$ooai:infoscience.tind.io:203608$$qDOI2$$qGLOBAL_SET$$pSTI
000203608 917Z8 $$x108898
000203608 917Z8 $$x108898
000203608 917Z8 $$x108898
000203608 917Z8 $$x108898
000203608 918__ $$dEDPO$$cIMT$$aSTI
000203608 919__ $$aLO
000203608 920__ $$b2014$$a2014-12-2
000203608 970__ $$a6457/THESES
000203608 973__ $$sPUBLISHED$$aEPFL
000203608 980__ $$aTHESIS