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QC 351 A7 no. 54 / It is possible to use a target of two coherent point sources, with a separation much greater than the resolution limit of a diffraction -limited lens, to determine the best focus of a photographic system. The interference pattern formed is a function of the focus error. Measurement of its characteristics (fringe period, fringe number, etc.) for different focus errors should indicate the best focus. Since the measurement is made at a long distance from focus, there is no ambiguity as to the direction of the best focus position relative to the film. An experiment, in which known focus errors were introduced on both sides of a visual best focus for a two -coherent -point- sources target, was designed and carried out for a 35 -mm camera system to determine the usefulness of such a method of determining best focus. A comparison test was made against a standard resolution vs focus error method. The experiment showed an unambiguous best focus within an error of 10 pm. The focus position was unambiguous because the final relationship studied was linear, and only one value was obtained. In general the new method appears to be faster, simpler, cheaper, and more accurate than the standard resolution method, and it requires no special instrumentation on the camera being tested.

Thesis (M.Eng.(Electronic Engineering))--University of Pretoria, 2007. / Summaries in Afrikaans and English. Includes bibliographical references (leaves 75-78).

Thesis (Ph.D.) - University of St Andrews, May 2008.

published_or_final_version / abstract / Electrical and Electronic Engineering / Master / Master of Philosophy

Thesis (M. Phil.)--University of Hong Kong, 2007. / Title proper from title frame. Also available in printed format.

This research examined two issues. First, it tested whether accurate map position-finding could be performed in a photographically simulated environment. Test subjects were asked to locate map position sites represented by color 35mm slides encompassing a 360-degree panoramic view for the corresponding ground location. Second, it tested if the perspective imparted by the lens type used to photograph the panoramic views had a significant effect on the accuracy of location selection by the subjects. The two lenses tested were a 50mm (normal perspective) lens and a 28mm (moderately wide-angle) lens which distorted distance, but provided a wider field-of-view. Results indicated that: 1) subjects were able to locate a specific map position by viewing color slides; 2) map position-finding accuracy performance was more dependent on the site itself than on the 35mm slide presentation; and, 3) there appeared to be no significant difference in map position-finding accuracy performance between using views photographed with a 50mm lens and a 28mm lens. / M.S.