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Periscope

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A periscope is a specialized optical device used for observation. It allows a person to see over, around, or through obstacles. This is essential when a direct line-of-sight is blocked.

Periscope simple
Periscope simple

In its most basic form, a periscope uses an outer case with two parallel mirrors. These mirrors are set at a 45° angle to reflect light. More advanced versions use prisms or fiber optics to provide better images. These complex systems can also provide magnification to see distant objects clearly.

The mechanism of a periscope relies on the path of light. In a simple mirror-based model, light hits the top mirror at a 45° angle. This causes the light to bounce downward through the tube. The light then hits the bottom mirror, which is also at 45°. This second reflection directs the light into the observer's eye.

Periskop linsen
Periskop linsen

More sophisticated designs use lenses or prisms to manipulate light. A lens periscope uses an objective lens to collect light. It may also use a field lens and an image-erecting lens. These components ensure the image appears upright and clear to the viewer.

Periscopes can be categorized by their design and specific function. Simple periscopes use mirrors, while naval or scientific models often use prisms. Prisms are glass shapes that use total internal reflection to move light. This method is much more rugged than using mirrors. Submarine periscopes are often described as two telescopes pointed at each other. If the telescopes have different magnification levels, the image will be magnified or reduced. Some specialized versions, like the Embedded Image Periscope, use digital sensors to project images onto a screen.

The history of the periscope spans several centuries of invention. In 1647, Johannes Hevelius described an early version called a "polemoscope" in his work *Selenographia*. Mikhail Lomonosov later invented an "optical tube" that functioned similarly. In 1854, Hippolyte Marié-Davy created the first naval periscope using two small mirrors. Simon Lake improved submarine technology in 1902 with a collapsible "omniscope." During World War I, Sir Howard Grubb worked to perfect the device for military use.

Military applications have driven much of the periscope's development. During World War I, soldiers used periscopes in trenches to avoid enemy fire. Some infantry rifles were even fitted with periscopes so shooters could aim from safety. In tanks, periscopes protect occupants by removing the need for vision slits in the armor. A related device called a protectoscope allows a vision slit to be covered by armored plate.

1889 Arthur Krebs & Jean Rey periscope for the french Gymnote submarine
1889 Arthur Krebs & Jean Rey periscope for the french Gymnote submarine

In 1936, Rudolf Gundlach patented a rotating periscope. This allowed tank commanders to achieve a 360-degree field of view without moving their seats.

Submarines rely heavily on periscopes for survival and combat. A submarine can use a periscope to search for targets while remaining submerged. Because the periscope creates a visible wake, commanders must use them with great discretion. Traditionally, submarines carried two different types of scopes. An observation periscope provides a wide field of view for scanning the surface. A targeting periscope provides high magnification to help aim torpedoes. Modern submarines are now transitioning to photonics masts, which use electronic sensors instead of long physical tubes.

Periscopes have also found use in aviation and specialized vehicles. The *Spirit of St. Louis* was the first known aircraft to use a periscope. Other aircraft, such as the Vickers VC10 and the B-52, used them for various sighting or navigation needs. In the past, B-52 crews used sextant periscopes for celestial navigation. Even high-speed aircraft like the North American X-15 have utilized periscopes. These tools show how the science of light can be applied to many different environments.

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File:Periscope simple.svg
Periscope simple.svg
File:Periskop linsen.svg
Periskop linsen.svg
File:1889 Arthur Krebs & Jean Rey periscope for the french Gymnote submarine.jpg
1889 Arthur Krebs & Jean Rey periscope...
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