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Illumination and Visibility of Radar and Sonar Displays Proceedings of a Symposium Sponsored by the ARMED FORCES NRC COMMITTEE ON VISION Held at the Smithsonian Auditorium, Washington, D. C. March 31 and April 1, 1958 ROBERT H. BROWN, EDITOR PUBLICATION 5 95 NATIONAL ACADEMY OF SCIENCES-NATIONAL RESEARCH COUNCIL WASHINGTON' D. C. 1958

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Library of Congress Catalog Card Number: 58-60044 Reproduction in whole or in part is permitted for any use of the United States Government

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PREFACE Among the activities of the Armed Forces NRC Committee on Vision is its sponsoring of vision research symposia devoted to areas of special interest to the military. The third such symposium since the reconstitution of the Commit- tee in the fall of 1956 was the symposium on Illumination and Visibility of Radar and Sonar Displays' held in conjunction with the 1958 annual meeting of the Committee on Vision, on March 31 and April 1. A business and technical session occupied the first morning, and the following afternoon and full day were devoted to the symposium. Considerable interest had been evidenced in the topic, and invitations and notices had been sent to many individuals and organizations. The total number of persons attending part or all of the sym- posium was 250. Dr. Robert H. Brown was a key figure in the planning of the symposium, and he acted for the Program Committee in selecting many of the speakers and In issuing invitations. He participated vigorously in the symposium itself, and subsequently he was prevailed upon to undertake the technical editorship of the proceedings volume. A considerable debt of gratitude is owed Dr. Brown for these fine accomplishments. Appreciation is expressed to the many others who helped make the symposium a success: the speakers and their co-authors' the chairmen of the several sessions and the participants in the discussion periods. Assistance was given by the Naval Research Laboratory in tape-record- ing the meeting so that discussion items could be transcribed' and by NRL and the Academy-Research Council in providing young ladies to operate the registration-information desk. Staff members of the Smithsonian Institution were most cooperative in assisting with the many administrative and housekeeping details, which assume magnified proportions when a meeting is held away from home base. Stanley S. Ballard, Executive Secretary Armed Forces- NRC Committee on Vision . . .

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FOREWORD World War II was fought with men using radarscopes in darkness or semi- darkness. The flashlight was an indispensable source of illumination. Since then, different methods for illuminating electronic displays have developed rapidly. The common objective of a mushrooming group of techniques has been to pro- vide adequate illumination in the area around a display without interfering with its essential function. In the past five years alone, techniques have been developed with an assortment of names: sodium yellow; mercury minus red; minus yellow, broad-band blue; localized polarization. Although these techniques have re- moved electronic displays from the darkroom, their use has been accompanied by the lack of communication frequently found in rapidly growing fields of science and engineering. Communication does not keep pace with the research and development occurring independently in different laboratories and in the final testing ground of the operational situation. One example, expressed in economic terms, illustrates the significance of orderly and planned communication. In a certain large installation, electrical power of 12 w per sq It produces an illuminance of 3 ft-c. In another installation, only 0.65 w per sq It is required for approximately the same illuminance. Does improved visibility of the displays in the first installation iustifv the greater :~: : _ 1 ~1 . 1 ~ ~ ~ J J - -- C~ ~ Cal close and tne ~ncreasec~ operating expenditures' the answer to this ques- tion. and to many similar questions, requires communication between men familiar with the different installations and, also, between men with different scientific and engineering backgrounds. Even more marked than the growth of methods for illumination has been the accelerating invention of new displays. These include transparent phosphors which provide images of excellent contrast and resolution, regardless of the illumination incident upon them. Direct-view storage tubes yield traces of con- trollable persistence and adequate luminance for use even in sunlight. Electro- luminescent panels are emerging from several laboratories. Bright displays are obtained by scan conversion. And so it goes. New displays are being continuously invented and improved in commercial, government, and university laboratories. At the same time, there has been unremitting research concerned with the effect of variation in basic parameters upon the use of presently available and widely used displays. For cathode-ray tubes, grid bias and receiver gain have received the most attention. Marked interest has been shown in other factors: number of signal pulses, pulse length, pulse repetition frequency, scan rate, size of display, geometrical and chromatic characteristics of the pip, cursor char- acteristics. This research has been directed toward the objective of utilizing dis ~1 _~^ ~_~ :_ _1_ : ~ . . 1 A - plays mc,re eIIecllvely In an environment With an ever-lncreaslng 1lluminance. During the symposium, the proceedings of which this volume presents, the first panel discussant noted the value of cross-fertilization between disciplines. Cross-fertilization requires a common medium, and in this case the medium is the operational setting. The output from the electronic displays in an illuminated environment must provide sufficient input to the operator's eyes to satisfy

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specified requirements of a combat-information center, a sonar system, an air- traffic-control center, an interceptor weapon system, etc. Operational require- ments constitute a final area involved in the illumination and visibility of radar and sonar displays. Consideration of operational requirements is basic to dis- cussion of the three areas already outlined: methods of illumination, new displays under development, and basic parameters imposed on present displays by visual factors. These areas of research activity cut across scientific and engineering fields: physiological optics and visual psychophysiology; illuminating engineer- ing and production engineering; naval science and aeronautics; solid-state physics and electronics; ophthalmology and the psychology of training and selection. They also involve contributions by men in commercial, government' and uni- versity laboratories; by administrators in the Armed Forces, the CAA, and other agencies; and by the operators themselves who use the displays and determine their effectiveness at widely varying levels of pragmatic sophistication. It is not too surprising that developments in the four areas have proceeded independently. Communication between individuals has been a function of the accident of an occasional task performed together. The symposium was organized on the assumption that communication on other than an accidental basis is essential to the most adequate solution of common problems. Deliberately, representation at the symposium was sought from leading workers in the four areas, from men who, in some cases, might be completely unfamiliar with three areas although expert in one. It was convenient, therefore, to schedule presentations in four subject-matter sessions: Operational Requirements for Cathode Tubes and Displays in Relation to Illumination Problems, Methods for controlling Ambient Illumination, Display Requirements Imposed by Visual Factors, and New Techniques under Development. A discussion session concluded the symposium. The symposium originated in the 1957 Human Engineering Conference sponsored by the Office of Naval Research in Tulsa. During that well-attended meeting, C. H. Baker, R. H. Brown, S. A. Francis, F. G. Henry, C. L. Kraft, R. T. Mitchell, and C. T. White discussed methods for the illumination of radar spaces. Following the meeting, discussions at the Naval Research Laboratory and at the Office of Naval Research indicated the desirability of a more extensive meeting with broader coverage of closely related topics. Since the hard core of topics involved the visual process, the Armed Forces-NRC Committee on Vision appointed a subcommittee to prepare the program. Members were S. S. Ballard, R. H. Brown, G. Finch, C. H. Roadman' P. I. Sperling, R. Tousey, and R. Trum bull. Editorial responsibilities for preparing the proceedings were divided. S. S. Ballard insisted on the role of an impatient, but zestful, publisher. Josephine Williams of the Academy Research Council has smoothed each rough passage to double its meaning while halving the eye movements, while R. H. Brown has been responsible for technical content and correspondence with the most co- operative speakers, now become authors. Robert Heath Brown -vie