Periscope

The periscope ( from Greek peri, "around, around " and skopein "watch", " (off) peeking " ) or periscope, also simplifies Wall gazer, is an optical instrument for observation from a fund out. The invention is based on Johannes Hevelius, who published them in 1647 in his printing Selenographia sive Lunae Descriptio under the name Polemoskop ( see drawing).

Applications

The periscope is mainly used in the war in order to safely out of bunkers, trenches (also telescope here ), and submarines can keep an eye out. Also, air-cushion vehicles make use of this technique because there is no more troubled waters is at a higher altitude, which restricts the view. In armored vehicles often comes a periscope used.

Angriffsperiskop and Nachtperiskop on a submarine

Looking through a periscope

Periscope in a bunker

Design and operation

A periscope consisting of a tube in the basic configuration, are disposed at the two openings mirrors or prisms. This guide perpendicular to the pipe running light rays into the tube and offset parallel to the original direction of incidence out again. An observer looking into the lower opening of a periscope, it gives the impression to look at the environment from above. The mirrors are aligned at an angle 45 ° to the incoming and outgoing light beam, resulting in a rectangular distraction. The reflectance of metallized mirror surfaces shall be deemed not perfect and continues to deteriorate over the course of months. The total reflective diagonal faces of prisms, however, have a better and more sustained reflectance and preferably be used.

This simple structure leads at longer periscopes to a too small field of view. With lens systems equipped periscopes can expand to many times by a suitable field lens the field of view.

Opposite, two such periscopes are shown schematically. The arrangement of the lenses corresponds in principle to that of a telescope with low magnification. Often, a magnification factor of 1.5 is chosen which gives the impression of a natural 1- times magnification for psychological reasons. Since the image in simple telescope systems, however, always rotated by 180 ° appears, is aided by the image- reversal - as in binoculars or telescopes for terrestrial observation - either a reversing prism ( g) or reverse lenses ( c).

In periscopes of the second type, a pair of inverting lenses ( C1 and C2) can be arranged such that the beam path between them is parallel. As a result, the length can be changed between c1 and c2 in wide range without affecting the image (eg for different Ausfahrhöhen a submarine periscope ).

If the second field lens ( c3/b2 ) something above the intermediate image position ( it thereby takes a part of the task of reverse lenses), at the location of the intermediate image space for a crosshair that appears sharp as a visor in the picture. For night observations, it can be illuminated from the side.

Simple operating principle of the periscope mirrors ( a) or deviating prisms (b).

Periscopes with lens system a objective lens b field lenses c Erecting lenses d e eyepiece eye lens f deviating prism g reversing prism

Variants

Panoramic telescope is called a periscope, the upper deflecting relative to the lower by 360 ° horizontally rotatable. This does not arise in the image when turning on its head, an additional prism system between the reversing lenses ( c1 and c2 ) ensures an appropriate counter-rotation of the figure.

In the ring image periscope, the horizon is completely visible with the aid of a fisheye lens. The image appears greatly reduced and distorted annular. This periscope can complement other periscopes so that the horizon ring around the actual image around is visible.