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How do Binoculars Work?

Dhanya Joy Oct 6, 2018
This treatise provides detailed information regarding various parts and the mechanism of working of a binocular. Also described are the different types of these devices.
Binoculars are also known as binocular telescopes, and have been used for hundreds of years for various purposes. They have made it easy to closely view distant objects. They are defined as handheld magnifying devices, which are made of two similar telescopes attached side by side.
Understanding their working can be helpful in case you decide to buy one. Though there are various types of binoculars available, the basic mechanism remains the same for all.

Binocular Parts

This device has three important components - a large lens known as the objective, a smaller lens, and a prism that functions as a mirror.

Lenses: The lenses used in binoculars are convex, and they may have two or more in number. Greater the number, higher is their magnification power.
Eyepiece: It performs the function of bringing the image into focus, and making it visible.

Prism: It is located between the lenses and the eyepieces, and performs two functions - bending of the light rays that enter the binoculars, and magnification and flipping of the image. If a prism is not present in the device, the image would appear upside down.

Working of Binoculars

The functioning of these devices is based on the principles of light refraction, distance, and light reflection. When a binocular is pointed at a distant object, the light rays from the object falls on the objective lens, which picks up these rays and forms a focused image of the object.
This image is picked up by the smaller lens, and is then magnified, which is further sent to the prism. It flips the image, and sends it to the eyepiece to make a three-dimensional picture, available for viewing by the human eye. Some binoculars also permit focusing adjustments through a 'center focus wheel', a movable dial, located between the eyepieces.
The magnification can be adjusted, and a sharper image can be viewed. A binocular may also consist of more than one prism to increase its functionality. They may consist of porro prisms or roof prisms. The magnification of the image would depend on the size and placement of the lenses.
For example, a binocular rated 7x50 would mean that the image can be magnified up to 7 times, and the size of the objective lens is 50 millimeters. The lenses should be aligned appropriately to obtain a clear and bright image. A larger objective lens would be able to collect more light rays, and present a brighter image.
Binoculars are usually made up of plastic, but may be reinforced using metal. They are used for various purposes like birdwatching, safaris, military purposes, hunting, etc. These devices should be selected according to the purpose for which they would be used.