Retinal directionality and wavefront sensing using a digital micromirror device

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Title: Retinal directionality and wavefront sensing using a digital micromirror device
Authors: Carmichael Martins, Alessandra
Permanent link: http://hdl.handle.net/10197/11655
Date: 2020
Online since: 2020-11-04T05:26:30Z
Abstract: In the recent years, light modulation has been achieved by an array of binary-positioning micromirrors, namely Digital Micromirror Devices (DMD), which have gained popularity in vision science, such as in retinal imaging, psychophysical vision testing or coded wavefront sensing. In this thesis, a DMD is used to measure two aspects of vision characterization: a) retinal directionality through the Stiles-Crawford effect of the first kind (SCE-I) and b) crosstalk-free wavefront sensing for large ocular aberrations. For the first part of this work, a DMD is used as a key component in a uniaxial flicker system to characterize the SCE-I in Maxwellian view, capable of controlling pupil aperture size and location, as well as field intensity by adjusting the duty cycle of the micromirrors. The SCE-I is tested under different conditions including foveal and parafoveal retinal locations, different luminance levels ranging from scotopic to photopic conditions, wavelength dependence through the visible spectrum and into the near infrared, as well as differences for myopic subjects. The SCE-I is also characterized in normal viewing conditions (Newtonian view) by scanning of the pupil with small apertures, where the influence of the SCE-I on visual acuity is analysed. Furthermore, a method to directly measure the integrated SCE-I is described and analysed using a geometrical optics absorption model based on volumetric overlap of incident light with photoreceptor outer segments, without accounting for photoreceptor waveguiding. In the second part, a wavefront sensing system using a digital micromirror device is implemented to achieve a wavefront sensor with high dynamic range and speed, without the use of a lenslet array which, in turn, avoids crosstalk. By sequential scanning of the wavefront, very high sampling densities can be achieved when compromising speed. The system is tested by measuring aberrations in an artificial eye and extended to the human eye.
Type of material: Doctoral Thesis
Publisher: University College Dublin. School of Physics
Qualification Name: Ph.D.
Copyright (published version): 2020 the Author
Keywords: Digital micromirror deviceStiles-Crawford effectMyopiaWavefront sensor
Language: en
Status of Item: Peer reviewed
Appears in Collections:Physics Theses

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