Science: Electronic Peeping Tom

Japanese nightcrawlers, toward the end of the war, often crawled in vain. They would sneak toward U.S. lines, trusting the friendly night. Then out of the silent darkness, a well-aimed bullet would pick them off. Could U.S. snipers see in the dark? Last week, the Army said yes and told how.

The U.S. sniper, looking through a fat telescope (“sniperscope”) mounted on his carbine, saw a bright green picture of everything in front of him. The gadget flooded his field of fire with invisible infra-red light. Jap uniforms showed up clearer than in daytime. Any attempt at camouflage was a dead giveaway.

There is no known way to turn infrared light directly into visible light. But it can be done indirectly by a complicated electronic device which closely resembles a television tube. The infra-red rays from the black-shielded spotlight hit the target and are reflected back (see diagram). Entering the telescope, they are focused by lenses on a special screen at the forward end of the tube. This “image” is not itself visible, but it knocks streams of electrons out of the screen.

The electrons are concentrated on a second screen, at the rear end of the tube, forming an “electron image.” This-screen is covered with a substance which glows green when hit by electrons. So a visible copy of the invisible infra-red image appears on it. When the sniper looks at the glowing image through a proper lens system, he sees in visible light the target which his sniperscope is watching in infrared.

In peacetime, the sniperscope has a dubious future. Cops and G-men might use it. Peeping Toms and gangsters might find it helpful too.