If you wanted to see over a short wall without being detected, what could you do? If you've seen spy movies or movies featuring submarines or army tanks, then you are probably aware of a tool called a periscope.
Periscope comes from two Greek words, "peri," meaning "around," and "scopus," meaning "to look." A periscope lets you look around walls, corners, or other obstacles without being seen. Submarines have periscopes so the sailors inside can see what's on the surface of the water, even if the ship itself is far below the surface. Periscopes can provide valuable visual data during battle and when determining the ship's position. Periscopes on newer submarines can take photographs with a 70-mm digital camera and then display those images on a television monitor. Some periscopes also have night vision, a still camera, and a video camera and can magnify images being viewed.
A simple periscope requires a vertical tube with mirrors placed at a 45-degree angle at the top and bottom of the tube. These devices basically collect light from an image and direct that light from one mirror at the top of the periscope to the mirror at the bottom of the periscope.
Despite its valued service for more than 80 years, the U.S. Navy will soon retire the conventional periscope, replacing it with non-penetrating imaging devices called "photonics masts." These are basically high-resolution cameras that capture and send visual images to flat panel displays in a submarine's control room.
Picture an antenna rising up from the submarine like it does from a car. Instead of using prisms and lenses, the new devices will use electronic imaging equipment. They will have three cameras a color camera, a high-resolution black-and-white camera, and an infrared camerato provide imaging for the submarine. One of the cameras will be highly sensitive and will be protected in a separate, pressure-proof and shock-hardened housing. There is also a range finder that uses lasers to find targets.
Though the military is saying goodbye to the original periscope, new periscopes have been developed that allow doctors to view inside the human body without having to resort to major surgery. What other uses do you see for the periscope?