Ph.D. Dissertation Defense: Chensheng Wu

Tuesday, July 5, 2016
10:00 a.m.
Room 2460 A.V. Williams Building
Emily Irwin
301 405 3682
eirwin@umd.edu

ANNOUNCEMENT: Ph.D. Dissertation Defense

NAME: Chensheng Wu

Advisory Committee:
Prof. Christopher C. Davis, Chair
Prof. Thomas Murphy
Prof. Phillip A. Sprangle
Prof. Jeremy Munday
Prof. Douglas Currie, Dean's representative

Date/Time: Tuesday, July 5, 2016 at 10:00am

Place: Room 2460 A.V. Williams Building

Title: The Plenoptic Sensor

In this thesis, we will introduce the innovation of a plenoptic sensor that can determine the phase and amplitude distortion in a coherent beam, for example a laser beam that has propagated through the turbulence atmosphere.. The plenoptic sensor can be applied to situations involving strong or deep atmospheric turbulence. This can improve free space optical communications by stabilizing optical links more intelligently and efficiently. Also, in directed energy applications, the plenoptic sensor and its fast reconstruction algorithm can give instantaneous instructions to an adaptive optics (AO) system to create intelligent corrections in directing a beam through atmospheric turbulence. The hardware structure of the plenoptic sensor uses an objective lens and a microlens array (MLA) to form a mini “Keplerian” telescope array that shares the common objective lens. In principle, the objective lens helps to detect the phase gradient of the distorted laser beam and the microlens array (MLA) helps to retrieve the geometry of the distorted beam in various gradient segments. The software layer of the plenoptic sensor is developed based on different applications. Intuitively, since the device maximizes the observation of the light field in front of the sensor, different algorithms can be developed, such as detecting the atmospheric turbulence effects as well as retrieving undistorted images of distant objects. Efficient 3D simulations on atmospheric turbulence based on geometric optics have been established to help us perform optimization on system design and verify the correctness of our algorithms. A number of experimental platforms have been built to implement the plenoptic sensor in various application concepts and show its improvements when compared with traditional wavefront sensors. These platforms include: (1) an intelligent AO system that uses the plenoptic sensor to guide its deformable mirror in correcting laser beam distortion; (2) a plenoptic sensor integrated telescope system that helps to reconstruct images that are severely distorted by atmospheric turbulence; (3) a compact scintillometer in the form of the plenoptic sensor; (4) an independent phase conjugation mirror that can observe the incident beam and instantaneously transmit a beam that contains its phase conjugation. As a result, the plenoptic sensor brings revolutions to the study of atmospheric turbulence and generates new approaches to handle turbulence effect better.

Audience: Graduate  Faculty 

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