Seeing in the dark

Lynn Poole tells how the tenth century Islamic scholar Alhazan described the workings of the camera obscura. Later, Frenchman Niepce discovered an emulsion that could retain a photographic image. Dr. Walter Driscoll, director of research at Baird-Atomic Inc., then shows a chart of the electromagnetic spectrum and notes that while x-rays yield only shadowy pictures and radar waves detect but don't create pictures, germanium and silicon filters block radiated energy and allow infrared light to pass through to form an image. Dr. Driscoll displays a scanning bolometer, which can see in the dark, but the shapes it creates need to be interpreted. He also shows a snooperscope and a film clip of a sniperscope with infrared scope. Previous research on infrared or thermal detection was done by Sir John Frederick William Herschel. Potter Trainer demonstrates and explains the Evaporagraph (EVA), which is based on the principle that all things radiate heat as infrared rays, and shows some of the actual pictures made from heat rather than light. Dr. Walter Baird describes applications of EVA to industry, such as detecting problem-causing hot spots in electronic equipment or indicating heat escape or insulation deficiency in a building. EVA's resolution is 10 lines/mm at best, and it shows temperature contrast of .2 degree. The machine's weakness is the slow speed of response to small temperature differences and the inability to obtain the temperature scale of the item viewed. Nonetheless, Mr. Poole says EVA could play a vital role in civil defense and medicine.