Hao Xie

BME PhD Defense Presentation

Date: Friday, November 18

Time: 8:30 a.m.(Atlanta) /9:30 p.m.(Beijing)

Location: 3115 McIntire room, Whitaker(Atlanta)/ Room 210, New COE 1st building

Advisor:

Peng Xi, PhD (Peking University, BME)

Co-advisor:

Philip J Santangelo, PhD (Georgia Institute of Technology, BME)

Committee:

Changhui Li, PhD (PKU, BME)

Tianyu Xie, PhD (PKU, BME)

Juntao Gao, PhD (THU, National Laboratory for Information Science and Technology) 

Sectioning optical microscopy with spatial modulated excitation laser

Abstract: 

Optical microscopy is one of the most widely used tools in biomedical researches. However, in the observation of thick biological samples, conventional optical microscopes suffer from background from out-of-focus structures. For example, in conventional epi-fluorescence microscopy, the whole sample is illuminated and the out-of-focus light contributes a strong background to the image, thus obscuring the in-focus details. Confocal microscopy and light sheet microscopy are the popular techniques for sectioning imaging. In this dissertation, excitation patterns are designed to improve optical sectioning capacity for point scanning and volumetric imaging systems.

In the first part we improved the point scanning microscopy with excitation laser modulations. We used a mirror to reflect the incident laser to produce the interference in the focal region. It is found both the sectioning capacity and peak intensity of excitation and depletion beam in STED are improved and the signal to noise ratio is enhanced. This dissertation also developed a point scanning based phase contrast microscopy: Schlieren confocal microscopy. We found incident laser refracts due to the local gradient of sample, and the detected fluorescence intensity could quantitatively reflect the local gradient of sample. This method keeps the optical sectioning capacity of confocal, and is fully compatible with confocal.  In the third part, this dissertation applied excitation modulation to inhibit the background in light field microscopy. We combined light sheet illumination with micro lens array coupled detection. It is demonstrated this method could significantly reduce the background in conventional light field microscopy and faster speed compared to light sheet.

This work succeed to apply spatial modulated excitation to point scanning and volume imaging systems, and improved their sectioning ability.