Light reflected from an object enables us to see the object when it is in the line of sight. Periscopes have long been used in order to see the objects that are not in direct line of sight. Periscopes are optical devices that use the laws of reflection.
Simple periscopes use two mirrors inclined at an angle of 45 degrees while complex ones use prisms instead of mirrors providing magnification as well. The mirrors are placed at 45 degrees facing each other. When light falls on one mirror, it is reflected back and falls on the other mirror and gets reflected to the observer’s eyes. It helps view over, around or through an object.
The most common use of periscopes is inside the submarine and military mainly for observation from concealed positions. From inside the submarine which is deep under water, objects above water (ships, boats etc) cannot be viewed without the help of periscopes.
A new technology has been developed by the US Navy to replace the traditional periscopes in the submarines. The new device called ‘photonics mast’ has been planned to use in the most advanced and automated submarines. Few important drawbacks of using the periscopes are its size, height and that it can allow only one person to view at a time. Photonics mast overcomes these defects. It basically consists of arrays of high resolution cameras which would do the surveillance tasks and images sent to the control room where anyone can view them.