Type of Document	Master's Thesis
Author	Shin, Dong-Ik
Author's Email Address	dshin@vt.edu
URN	etd-08072002-194429
Title	Laser Scanning Imaging for Increased Depth-Of-Focus
Degree	Master of Science
Department	Electrical and Computer Engineering
Advisory Committee	Advisor Name Title Poon, Ting-Chung Committee Chair Indebetouw, Guy J. Committee Member Stolen, Roger Hall Committee Member
Keywords	depth-of-focus microscopy difference-of-gaussians optical scanning holography
Date of Defense	2002-07-22
Availability	mixed
Abstract Throughout the decades, different techniques have been proposed to improve the depth-of-focus in optical microscopy. Common techniques like optical sectioning microscopy and scanning confocal microscopy have innate problems. By simply modifying the pupil function in microscope imaging system, we can also extend the depth-of-focus. The scanning system with a thin annular pupil has a high depth-of-focus and can scan the whole object, but the output light is too dim to be detected well by a photodetector. In this thesis, we propose a scanning technique employing an optical heterodyne scanning system using a difference-of-Gaussians (DoG) pupil. The object is illuminated by the combined beam which consists of two Gaussian beams with different waists, frequencies, and amplitudes. This system does not block most light like the annular pupil system and can obtain high depth-of-focus. The main objective of the thesis is to extend the depth-of-focus using the proposed system. The depth-of-focus characteristics of the DoG pupil function are examined and compared with those of well-known functions such as the circular, annular, and Gaussian pupils.
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