A direct-view thermal imaging tube

Abstract

This paper describes the pyroelectric electron-mirror tube, which is a thermal imaging tube working in the 8-14 pm band of the infrared. The principle of operation is that an image of the thermal scene is formed on a pyroelectric target and a representation of the resulting voltage pattern is formed on a phosphor screen using the principle of the electron mirror. This results in a direct-view tube requiring no mechanical scanning, cryogenic cooling, or TV circuitry.The tube construction and target preparation are described. The basic theory of the tube is presented, dealing with the voltage response of the target to the thermal radiation, the action of the electron mirror, and the role of the electron optics in generating an image on the screen.Experimental measurements show a minimum resolvable temperature difference of 0.4 K at a spatial frequency of 1 cycle mm-l at the target. A prototype system is described, based on the tube. It weighs 4.7 kg and is powered by a pack having a life of 5 h from rechargeable batteries. Prospects for future development of the tube are discussed.