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A periscope, is a optical device for conducting observations from a concealed or protected position. Simple periscopes consist of reflecting mirrors and/or prisms at opposite ends of a tube container. The reflecting surfaces are parallel to each other and at a 45° angle to the axis of the tube. The Navy attributes the invention of the periscope (1902) to Simon Lake and the perfection of the periscope to Sir Howard Grubb.

For all its innovations, USS Holland had at least one major flaw; lack of vision when submerged. The submarine had to broach the surface so the crew could look out through windows in the conning tower. Broaching deprived the Holland of one of the submarine’s greatest advantages – stealth. Lack of vision when submerged was eventually corrected when Simon Lake used prisms and lenses to develop the omniscope, forerunner of the periscope. Sir Howard Grubb, designer of astronomical instruments, developed the modern periscope that was first used in Holland-designed British Royal Navy submarines. For more than 50 years, the periscope was the submarine’s only visual aid until underwater television was installed aboard the nuclear powered submarine USS Nautilus.

Periscope, optical instrument for conducting observations from a concealed or protected position. A simple periscope consists essentially of reflecting mirrors or prisms at opposite ends of a tube with the reflecting surfaces parallel to each other, and at a 45° angle to the axis of the tube. The so-called field or tank periscope has been commonly used in trenches, behind parapets and earthworks, and in tanks to provide protected vision for the user. The submarine periscope is a larger and more complex instrument. It consists of reflecting prisms at top and bottom of the vertical periscope tube, with two telescopes and several lenses between them, and an eyepiece at the lower end (see Prism; Telescope). The submarine periscope is contained in a strong, thick casing tube, 10 to 15 cm (4 to 6 in) in diameter, to stand the pressure of the water at great depths. The only part of the outer tube that turns is the head, and this is attached to the inner tube, which can be turned by means of a lever or a crank and gearing. The field of a simple periscope is small, but several recent improvements have extended it somewhat. The magnification of distant objects is from 1.5 to 6 diameters.

Periscopes are also used as viewing devices in military aircraft, in nuclear physics laboratories to observe radioactive reactions, and in particle accelerators.

Periscope Submarine

A periscope is an optical device that provides a view of an otherwise obstructed scene. A simple periscope consists of a tube equipped with a set of reflecting prisms or mirrors that redirect light from objects out of the observer’s line of sight. Each placed at 45-degree angles to the direction of view, the prisms function together to allow a user to observe a scene from the point of view of the top of the periscope while remaining concealed. The top prism receives light and directs it down to the lower prism, close to the eye of the observer. Submarine periscopes, as shown here, are more complex. A series of lenses, two telescopes, and two reflecting prisms are used to bring a distant island into focus.

Sir Howard Grubb

Thomas Grubb (1800-1878) founded a telescope making firm in Dublin. Sir Howard Grubb's father was noted for inventing and constructing machinery for printing. In the early 1830s, he made an observatory for his own use equipped with a 9-inch (23cm) telescope. Thomas Grubb's youngest son Howard (1844-1931) joined the firm in 1865, under his hand the company gained a reputation for the first-class Grubb telescopes. During the First World War, demand was on Grubb's factory to make gunsights and periscopes for the war effort and it was during those years that Grubb perfected the periscope's design. ©2021.