Periscope

A periscope is an instrument for observation around or through an object in presence of an obstacle or condition that prevents generally the direct line-of-sight observation from an observer's current position. In its simplest form, it generally consists of an outer case with the mirrors at each end set parallel to each other at the angle of  45°. This is said to be a form of periscope with the addition of two simple lenses that are generally said to be served for observation purposes in the trenches during World War I. The military personnel are also said to use periscopes in some gun turrets and in armoured vehicles.

Uses of Periscopes

More complex periscopes are generally using the prisms or advanced fibre optics instead of mirrors and providing magnification required on submarines and in various fields of science. Overall, we can conclude that the design of the classical submarine periscope is very simple, that is two telescopes pointed at each other. If the two telescopes that we have seen have different individual magnification, the difference which is between them causes an overall magnification or reduction.

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History of Periscope

In 1647 the one and only Johannes Hevelius has described in his early periscope which he called a "polemoscope" with lenses, in his work ‘Selenographia’, Sive Lunae description Selenography, or an account of the Moon. Hevelius saw military applications for his invention.

In 1902 Sir Simon Lake generally used periscopes in his submarines. Sir Howard Grubb generally is said to have perfected the device in World War I. Morgan Robertson that is from 1861–1915 claimed to have tried to patent the periscope. The periscopes were in some cases fixed to rifles that served in World War I from 1914–1918 to enable soldiers to see over the tops of trenches thus avoiding exposure to enemy fire especially from snipers. Some of them also allowed estimating the distance to a target as they were designed as stereoscopic rangefinders.

Periscopes generally 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. We can say that when not in use then a submarine's periscope retracts into the hull. A submarine commander in tactical conditions must exercise discretion when using his periscope since it creates a visible wake and may also become detectable by radar which is giving away the submarine's position.

In 1861-65, Marie-Davey generally built a simple fixed naval periscope using mirrors. Sir Thomas H. Doughty of the US Navy which was later said to be invented a prismatic version that is said to be for use in the American Civil War of 1861–65.

Working of Periscope

Tanks and armoured vehicles that use periscopes enable drivers or tank commanders and other vehicle occupants to inspect their situation through the vehicle roof. Periscopes generally permit view outside of the vehicle without needing to cut these weaker vision openings in the front and side armour protecting the vehicle and occupants.

A proctoscope is a related periscopic vision device designed to provide a window in an armoured plate similar to a direct vision slit.  A compact periscope can be said as that it is inside the protector scope which generally allows the vision to be blanked off with the spaced armoured plate. So we can say that this prevents a potential ingress that is a point for small arms fire which is with only a small difference that is in the vision height but still it requires the armour to be cut.

In the context of all those things which we have learnt of armoured fighting vehicles such as tanks, a periscopic vision device may also be referred to as an episcope. In this context, we can say that a periscope refers to a device that can rotate to provide a wider field of view or at times it is fixed into an assembly that can that is while an episcope is fixed into position.