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Proceedings Paper

Criteria for Specifying Projectors for the Photo-Interpreter
Author(s): J. E. Davis
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Paper Abstract

A practical, approach to specifying and designing large format rear screening projectorc for aerial reconnaissance photography is outlined. Unique brightness control methods are discussed in terms of their proper use to keep the interpreter's pupillary diameter at a size to allow maximum visual acuity. Methods of keeping a uniform brightness over the screen for different viewing positions are described. Solutions are out-lined for factors contributing to uneven screen brightness such as the observation angle with the principal axis of the diffusion lobe of the screen, system vignetting, and cosine effects. These solutions include the use of large diameter Fresnel lenses, strategically placed apodizing filters, and a discussion of the Luneburg criteria for condenser lens design. Characteristics of rear projection screening materials are discussed in terms of their performance in the projection of high definition (100 to 200 medium contrast lines per millimeter) photographic records. A system of evaluating screening materials by their modulation transfer runction is pioposed. Measurement of the imagery by moving reticles in the projected field is discussed and problems associated with obtaining sharp, fine lines on the screen with this type of system are summarized. Various light sources and their effects on interpretation, good and bad, are described. The use of image rotators, both optical and mechanical, as an aid in angular measurement of the imagery is outlined. A formula is developed from an empirical formula for determining the minimum magnification of a projector based on the resolution capability of all of the elements in the system from film to and including the eye. Also, a method of designing projection systems using the modulation transfer function of each element, including the eye, is analyzed.

Paper Details

Date Published: 1 June 1966
PDF: 10 pages
Proc. SPIE 0005, The Human in the Photo-Optical System, (1 June 1966); doi: 10.1117/12.946685
Show Author Affiliations
J. E. Davis, Hughes Aircraft Company (United States)

Published in SPIE Proceedings Vol. 0005:
The Human in the Photo-Optical System
Robert L. Minter, Editor(s)

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