Apertures are usually placed in optical systems to reduce unwanted light, which generally comes from sources other than the intended object. However, even though geometrical rays may be blocked from the detector plane, diffraction of the unwanted radiation will produce an increase in measured irradiance. Therefore, the goal of this dissertation is to model this diffractive scatter in a system of one or two circular apertures and confirm or reject the model through comparison of theoretical and experimental results. The model is based on the Geometric Theory of Diffraction, which uses coefficients of diffraction to predict the complex amplitude of an electromagnetic field following a diffracting aperture. A near field sampling theorem is derived and applied to both one and two aperture calculations. In addition, because this theory relies on root finding techniques to determine points of diffraction, a modification is made to the one-dimensional bisection method for use as a global root-finding technique for the case of two apertures. Comparison of theoretical and experimental data confirms the validity of the model for both cases. However, because diffraction from the second aperture is so weak, results from one aperture are shown to correctly model diffraction for the two aperture case as well. Furthermore, because theoretical results for both one and two aperture cases are quite close, but agreement between theory and experiment is better for the two aperture case, the role of the second aperture is determined to be that of blocking reflective scatter from the rim of the first aperture.
| Identifer | oai:union.ndltd.org:arizona.edu/oai:arizona.openrepository.com:10150/185252 |
| Date | January 1990 |
| Creators | Griffin, DeVon Wadsworth. |
| Contributors | Wolfe, William L., Burke, James J., Palmer, James M. |
| Publisher | The University of Arizona. |
| Source Sets | University of Arizona |
| Language | English |
| Detected Language | English |
| Type | text, Dissertation-Reproduction (electronic) |
| Rights | Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author. |
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