A periscope uses two mirrors to reflect the object light twice and then redirect it toward the eye. The reason why the periscope can see the top clearly from below is because the two plane mirrors are parallel to each other and both form an angle of 45 degrees with the horizontal direction. The scene is reflected and imaged twice by the plane mirror, so that the top can be seen from below. scene.
The only way for a submarine traveling underwater to observe the sea level and air conditions is with the help of a periscope. Most submarines are equipped with two periscopes - an attack periscope and an observation periscope. The former is used to discover and aim at water targets, while the latter is mainly used to observe sea and air conditions and navigation observations.
Before a submarine surfaces, the captain must instruct the submarine to use the periscope to conduct a 360-degree observation of the sea level at the periscope depth in order to detect possible enemy situations as early as possible. The submarine will only surface if it is confirmed that there is no threat.
Extended information
There are two obvious problems with the use of periscopes.
1. The most important thing is the vibration problem. When the periscope is fully raised, the slender periscope mast will affect the submarine's normal navigation and cause lateral instability. When the submarine speed exceeds 6 knots, the periscope mast will cause huge vibrations and become completely unusable.
Later, additional mast brackets were installed on the submarine, and the shape of the periscope tip was redesigned and improved to reduce water wave resistance. Although the vibration was not completely eliminated, it was a big improvement after all.
2. Another important issue is the fog produced by the periscope lens. Because the air inside the submarine is humid, the periscope lenses often produce fog, so the periscope must be designed and manufactured to be as waterproof and sealed as possible. When a submarine is attacked by a depth bomb, it is easy for the sealing structure of the periscope to be damaged, resulting in the generation of fog.
The observation periscope has a seat and pedal that can cooperate with the movement of the periscope lifting rod. It is mainly used for sea and air observation and course confirmation before the submarine floats up. There is no attack periscope, which is mainly used for enemy situation observation, target ranging and attack azimuth angle calculation. At the same time, observation telescopes are also superior in nighttime observation capabilities.
Baidu Encyclopedia-Periscope