Publication Date

2018-05-09

Availability

Embargoed

Embargo Period

2019-05-09

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PHD)

Department

Electrical and Computer Engineering (Engineering)

Date of Defense

2018-04-19

First Committee Member

Michael Renxun Wang

Second Committee Member

Kamal Premaratne

Third Committee Member

Fulin Zuo

Fourth Committee Member

Sung Jin Kim

Fifth Committee Member

Onur Tigli

Abstract

Optical coherence tomography (OCT) is a noninvasive, cross-sectional, and three-dimensional (3D) tomographic imaging modality. It offers subsurface deeper penetration depth and larger scan area than confocal microscopy as well as higher resolution than ultrasound imaging, very suitable for 3D in vivo imaging of eyes, skins, blood vessels, and other non-biomedical samples. However, there is a trade-off problem among lateral resolution, lateral field of view (FOV), and axial imaging depth, limiting the performance of OCT systems. In this dissertation, we report our studies to solve these problems and to make the OCT a competitive tool for a variety of 3D imaging applications. Firstly, we have successfully demonstrated the lateral resolution and image quality improvement of a spectral domain OCT by multi-frame superresolution technique for in vitro imaging. Through superresolution processing a series of low density C-scans images with intended sub-spot-spacing shifts, about 3 times lateral resolution improvement has been achieved along with background noise reduction and image quality doubling without sacrificing the axial FOV. Next, with unintended minor motion and vibration of live body, axial motion shift estimation and compensation has been performed. Multi-volume registration algorithm is used to estimate the translational shifts in the lateral plane without artificially introducing sub-spot-spacing shifts. Similar superresolution processing is then applied to multiple C-scans for lateral resolution improvement. 3D images, layered 2D lateral images, and B-scan images of in vivo skin tissues, fingerprints, and retina layers have all shown remarkable lateral resolution and image quality improvement. It is known that the lateral FOV is inversely proportional to lateral resolution owing to optical aberrations. To enlarge the FOV and maintain the high lateral resolution, a customized 3D image stitching method is introduced to improve the lateral FOV from 1300×1300 μm2 to 3.2×2.3 mm2 and from 500×500 μm2 to 2.10×1.15 mm2, without hardware change or edge resolution reduction. The lateral FOV can be enlarged as long as nearby OCT scan areas have partial areal overlapping. The axial resolution of OCT is dependent on the coherence length of the light source. To improve the axial resolution, we report our initial study on exploring of novel PbS quantum dots based single-mode light emitting polymer waveguides with only cm device length and adjustable center wavelength with ~200 nm broad spectral bandwidth. The broad spectral bandwidth would benefit OCT axial resolution improvement. Future researches including improving axial resolution by digital deconvolution, enhancing the depth dependent image quality by high dynamic range technique, and 3D fingerprints imaging for security applications have been summarized at the end of the dissertation.

Keywords

Optical Coherence Tomography; Superresolution; 3D Imaging; Image Stitching; Quantum Dot; Deconvolution

Available for download on Thursday, May 09, 2019

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