Traditional laser scanning systems, such as those used for microscopy, typically image objects of finite thickness. If the depth-of-focus of such systems is low, as is the case when a simple clear pupil is used, the object must be very thin or the image will be distorted. Several methods have been developed to deal with this problem. A microscope with a thin annular pupil has a very high depth-of-focus and can image the entire thickness of a sample, but most of the laser light is blocked, and the image shows poor contrast and high noise. In confocal laser microscopy, the depth-of-focus problem is eliminated by using a small aperture to discard information from all but one thin plane of the sample. However, such a system requires scanning passes at many different depths to yield an image of the entire thickness of the sample, which is a time-consuming process and is highly sensitive to registration errors.
In this thesis, a novel type of scanning system is considered. The sample is simultaneously scanned with a combination of two Gaussian laser beams of different widths and slightly different temporal frequencies. Information from scanning with the two beams is recorded with a photodetector, separated electronically, and processed to form an image. This image is similar to one formed by a system using a difference-of-Gaussians pupil, except no light has been blocked or wasted. Also, the entire sample can be scanned in one pass. The depth-of-focus characteristics of this synthesized difference-of-Gaussians pupil are examined and compared with those of well-known / Master of Science
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/33091 |
| Date | 25 May 1999 |
| Creators | Kourakos, Alexander William |
| Contributors | Electrical and Computer Engineering, Poon, Ting-Chung, Brown, Gary S., Indebetouw, Guy J. |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Detected Language | English |
| Type | Thesis |
| Format | application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
| Relation | ETD.pdf |
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