CHROMATIC FLUORESCENCE IMAGING

Author:

Chen, Yizhu

Graduate Program:

Electrical Engineering

Degree:

Doctor of Philosophy

Document Type:

Dissertation

Date of Defense:

May 28, 2019

Committee Members:

Zhiwen Liu, Dissertation Advisor/Co-Advisor
Zhiwen Liu, Committee Chair/Co-Chair
Iam-Choon Khoo, Committee Member
Weihua Guan, Committee Member
Patrick James Drew, Outside Member
Siyang Zheng, Dissertation Advisor/Co-Advisor
Siyang Zheng, Committee Chair/Co-Chair

Keywords:

Fluorescence imaging
Chromatic imaging
Computational imaging

Abstract:

Fluorescence imaging has been an indispensable tool for the observation of various biological activities as the fluorophore can be designed to bind a specific target in a biological process and thus can provide distinct indication and significantly improved contrast over images obtained under white light illumination. However, the conventional laser scanning fluorescence imaging technique has unbalanced scanning speed in lateral and axial directions when imaging a three-dimensional (3D) volume. Fast lateral scanning can be implemented by using spinning Nipkow disk which enables scanning speed up to 1KHz [1]; but the axial imaging acquisition rate remains low as slow mechanical scanning of either the sample or the objective is typically required, which imposes a significant limitation on the temporal resolution and hinders us from imaging fast biological processes in three dimensions. Spectral encoding has been a useful tool for improving imaging speed, since it exploits chromatic aberration or dispersion to map different wavelengths of a polychromatic light source to different locations on a sample and enables simultaneous detection of signals from multi-areas. In Chapter 2 of the thesis, methods and applications of spectrally encoded chromatic imaging will be reviewed. The work presented in this dissertation is mainly focused on the development of new imaging techniques that can alleviate the demand for scanning, especially in the axial direction. Chapter 3 of the thesis will focus on a new axial slice light sheet two-photon fluorescence imaging technique enabled using an array of high aspect ratio micro mirrors arranged along the axial direction. With the mirror array, a two-dimensional axial cross section of a sample can be simultaneously imaged without scanning. Chapter 4 will focus on the characterization of the two-photon emission property of citric-acid-based band shifting materials. The emission spectra of the material shift with different excitation wavelengths. This unique property may be leveraged to enable spectrally encoded fluorescence imaging. In Chapter 5, a computational imaging method based on intensity correlation will be presented. The proposed imaging method can potentially enable large depth of focus and a large field of view, and can thus potentially allow for 3D imaging. The feasibility of this imaging method is numerically demonstrated with a simulated pattern and the retrieved image is in good accordance with the target. This imaging method maintains a simple lens-free setup and could potentially alleviate the relatively complex system design of imaging modalities based on the field correlation. The summary of the dissertation work will be presented in Chapter 6 and the perspective for future work will be discussed.