Excerpt from The Use of Aerial Infrared Thermography to Compare the Thermal Resistances of Roofs In conducting an aerial infrared survey, an infrared line scanning system mounted in an aircraft scans the terrain, building up a thermal image as the aircraft progresses along a flight line, as shown in figure 1. The scanner is basically an optical telescope, with its narrow field of view continuously redirected by a spinning flat mirror. The mirror causes the system to scan in a plane perpendicular to the direction of flight of the aircraft. Such systems have one or more cryogenically cooled thermal radiation detectors in the focal plane of the telescope which convert the focused thermal energy received by the detector into an electrical signal. This electrical signal can be processed into a visual image on a cathode-ray tube (crt) which can be photographically recorded or digitized and recorded on a magnetic tape recorder for future processing. About the Publisher Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com This book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully; any imperfections that remain are intentionally left to preserve the state of such historical works.