Dissertation Defense: Jieun Ryu, "Estimation of Diffractive Surface Profile Using Phase Retrieval Techniques"

    Friday, August 5, 2022 - 2:00pm

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    An intraocular lens (IOL) is an artificial lens implanted in the eye as part of a treatment for cataracts or myopia. Multifocal IOLs provide good visual acuity for both distance and near vision. Especially, multifocal IOLs with a diffractive optic design have been proven to provide a significant vision for both far and near than refractive multifocal IOLs and monofocal IOLs. Methods for estimating the diffractive surface profile of a multifocal diffractive IOL are investigated. Several types of instruments have been proposed to determine the phase profile, such as conventional interferometers and Shack-Hartmann sensors, but additional optical components increase the complexity and cost of the system. Holography-based setups have also been widely used for surface profile measurement and quality control. However, conventional holography requires a reference beam and is vulnerable to external influences such as vibrations and air turbulence. In this dissertation, to avoid the limitations of the conventional system stated above phase retrieval techniques are implemented to estimate the diffractive surface profile of an IOL. A typical image sensor captures diffraction patterns and the recorded diffraction intensities are iteratively processed to reconstruct the phase of the complex wave. To obtain accuracy and convergence, multiplane phase retrieval algorithm described by Gerchberg is used. To acquire diffraction patterns of multiple intensities, some techniques were used, such as displacing the recording camera to record intensities at different planes, modulating phase in Fourier domain using spatial light modulator (SLM) to record a sequence of intensities with different image planes, and modulating phase in pupil plane using SLM to record diffraction patterns with phase diversity. Simulation and experimental results are presented for each setup.