Study of Laser Speckle Scattering in Vitreous Humor Models

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Oh, Wanseok
Laser Speckle Scattering; Vitreous Humor Models; Engineering; Optics; Physical Sciences and Mathematics; Physics
thesis / dissertation description
When a highly high coherent light propagates through a medium, interactions between light and the medium produces a unique intensity speckle pattern that is dependent on several factors such as particle size in the medium, wavelength of the light, concentration of medium, and scattering angle. Speckle patterns from either static or dynamic specimens have been studied using optical techniques due to its non-invasive nature. Speckle patterns from biological specimens (dynamic) are different from that of the static specimens since random movement of molecules (Brownian motion) in the biological specimen affect the light interactions and thereby the intensity of the speckles in the speckle pattern. Several studies have shown the optical properties of the biological specimen can be characterized using statistical properties from the speckle pattern. A histogram of intensity distribution of the speckle pattern can be used to extract certain optical properties of the specimen such as bioactivity, blood flow, and skin perfusion. In this thesis, a new approach for analyzing biological specimens is presented utilizing a peak shift in the histogram plot (called the Histogram Wavelength Analysis Method) of the intensity of the speckles when changing the wavelength of the incident light. Five different wavelengths were used in a modified slit-lamp equipment for the experiment. Also six different sizes of nanobeads embedded in vitreous humor (biological specimen) were studied. The theory developed for this experimental method matches well with the results and will be presented in the thesis