Periscope

[1] More complex periscopes using prisms or advanced fiber optics instead of mirrors and providing magnification operate on submarines and in various fields of science.

Johannes Hevelius described an early periscope (which he called a "polemoscope") with lenses in 1647 in his work Selenographia, sive Lunae descriptio [Selenography, or an account of the Moon].

[3] In 1854, Hippolyte Marié-Davy invented the first naval periscope, consisting of a vertical tube with two small mirrors fixed at each end at 45°.

Periscopes, in some cases fixed to rifles, served in World War I (1914–1918) to enable soldiers to see over the tops of trenches, thus avoiding exposure to enemy fire (especially from snipers).

During World War II (1939–1945), artillery observers and officers used specifically manufactured periscope binoculars with different mountings.

[7] An important development, the Gundlach rotary periscope, incorporated a rotating top with a selectable additional prism which reversed the view.

This allowed a tank commander to obtain a 360-degree field of view without moving his seat, including rear vision by engaging the extra prism.

The Gundlach-Vickers technology was shared with the American Army for use in its tanks including the Sherman, built to meet joint British and US requirements.

This saw post-war controversy through legal action: "After the Second World War and a long court battle, in 1947 he, Rudolf Gundlach, received a large payment for his periscope patent from some of its producers.

The FV4201 Chieftain used the TESS (TElescopic Sighting System) developed in the early 1980s that was later sold as surplus for use on the RAF Phantom aircraft.

Periscopes allow a submarine, when submerged at a relatively shallow depth, to search visually for nearby targets and threats on the surface of the water and in the air.

(Peral also developed a primitive gyroscope for submarine navigation and pioneered the ability to fire live torpedoes while submerged.

While the cables carrying the signal must penetrate the submarine's hull, they use a much smaller and more easily sealed—and therefore less expensive and safer—hull opening than those required by periscopes.

Eliminating the telescoping tube running through the conning tower also allows greater freedom in designing the pressure hull and in placing internal equipment.

The Vickers VC10 had a periscope that could be used on four locations of the aircraft fuselage,[15] V-Bombers such as the Avro Vulcan and Handley Page Victor[16] and the Nimrod MR1 as the "on top sight".

[19][20] An emergency periscope was used on all Boeing 737 models manufactured before 1997 found under "Seat D" behind the over wing exit row to regulate the landing gear.