Use of Infrared in Surveillance Abstract: This article begins with an introduction to Sir William Herschel's discovery and description of infrared radiation in 1800. It follows by describing various uses of infrared for surveillance purposes. The first application described concerns the role of infrared in active and passive night vision devices (NVDs) for both military and recreational use. Describes the basic functions of these devices and the differences between the uses and benefits of active and passive oscilloscopes. The second application is the use of infrared in early detection of missile launches and estimation of impact points. In a similar military role, infrared is also used to detect land mines hidden in various parts of the globe. Finally, infrared is used in home or business surveillance through a system that uses an infrared camera to create a thermogram. Infrared Infrared represents the portion of the electromagnetic spectrum that extends from wavelengths from 0.75 to 1000 microns. This portion of the spectrum is invisible and lies beyond the red end of the visible spectrum. Infrared rays are much longer than those of the color spectrum but shorter than radio waves and have a penetrating thermal effect. For this reason, infrared rays are often called heat rays. Infrared was accidentally discovered in 1800 by Sir William Herschel. In an experiment conducted for uses other than the discovery of infrared, Herschel used a glass prism to break light down into its component colors, a discovery already made some time ago by Newton. However, by moving a thermometer across the spectrum, Herschel noticed that the temperature increased from violet to red, reaching a maximum temperature in the dark region beyond the visible spectrum. He called this region infrared radiation. ApplicationsNight Vision Devices (NVDs) Infrared was first linked to technology during World War II with the invention of the sniper scope. The sniper scope was used to detect infrared rays coming from objects hotter than the surroundings in an attempt to "see in the dark". The invention worked from the understanding that any object with a temperature above absolute zero is a natural radiator of infrared energy. This infrared radiation results from the acceleration of electrically charged particles within the material. The hotter the object, the greater the particle emission resulting from the greater acceleration.