Binocular Parts And Their Functions (Ultimate Guide)

Binoculars are 17th-century inventions and they were invented to let people see things that are far away. A binocular does this job of magnification by using the rules of optics. Optics is the study of how light behaves. If we can understand the behavior of light, we can design binoculars that can allow us to view objects that are far away.

Binocular Parts And Their Functions

Binoculars are generally made with two telescopes joined side by side. This positioning allows the user to view the single image with both eyes. A binocular can be used to see closer as well as farther objects clearly. Binoculars have different parts that perform the complex task of making an object that far away seem closer.

Today, we are going to be taking a look at the different parts of a Binocular and we will also show you how these parts interact with each other. So, without wasting any time, let us get into it. But before explaining the parts of a Binocular, let us first see the areas where you can actually use a binocular.

Binocular Parts and their Functions

Mechanical Part

The mechanical part of a binocular is needed to adjust and handle the optical parts. Some of the basic mechanical parts are given below:

Focus Wheel

A focus wheel of a Binocular is present near the eyepiece. When we focus on an image, the image comes to the center and it is called the center focus. Similarly, there are right focus and left focus. The focus wheel has the function to move lenses in the eyepiece so, the image can get focused in the right manner. The focus wheel mainly helps to target the image and then adjust the focus.

Diopter Knob

The diopter knob is a ring-like structure that is placed behind the eyepiece lens. The main job of the diopter knob is to move the eyepiece lens to the left or right. This permits you to focus the eyepiece lens individually. The diopter knob can be found on the objective lens or the eyepiece lens. This knob is helpful for people who year eye classes, it removes the strength of the eyeglass to give a more legitimate image.


The body (or the Chasis) is basically the external housing of the binocular that holds everything together. The whole binocular is inside the Chasis. As far as the material of a binocular’s body goes, it can depend. Toy Binoculars for kids are generally made out of plastic. Similarly, a good enough binocular has an aluminum build. A military-grade binocular, on the other hand, is very sturdy and has a top-quality metal build.

Optical part

The optical parts are the actual parts that do the job of magnification. These parts are explained below:

Objective Lenses

The main job of an Objective lens is to pick the light stream and magnify them to different parts of the device. It gets an accurate image out of the light input. The diameter of an objective lens determines the quantity of light that a binocular can get.

These lenses come in different shapes and sizes. The core weight of the binocular is also dependent on the size of an objective lens.

A big objective lens is generally better. It can collect more light and it can also increase light transmission. An objective lens has a coating and depending on the coating, the quality of an objective lens can differ.

Eyepiece Lenses

Eyepiece Lenses

Eyepiece Lens is also vitally important if you want to magnify the image. These lenses are closer to the eyes of the viewer and they are noticeably smaller than the objective lenses. The objective lens of a binocular gathers the light and brings it on the binoculars to focus the image. The images are then placed on the eyepiece and then it magnifies the image.

The eyepiece comes with different focal lengths. This plays a very important role in the magnification of the image. The eyepiece contains various kinds of lens housing as well.

The focus of the image can be focused by moving the eyepiece near to the objective lens or far from the actual lens. The eyepiece lens is fixed in the binoculars which provides an apparent magnification.



The objective lens only does the job of collecting the light, it doesn’t fix the orientation. To fix the oriented image, we need a prism. The prism makes sure the picture does not get distorted. To fix this correction, the prism lens is placed between the objective lens and the eyepiece.

The prism has a crystal build which helps the binoculars to decrease in size. This makes sure that the binocular is easy on the hand. Two types of prisms are used roof prism and Porro prism. These prisms ensure that there is no loss of light and the overall quality of the image is sharp.

Uses of Binoculars

A Binocular can be used for many things. The device is simple to use and handle so, even kids can use them for outdoor activities. You can use a binocular in the sea for watching whales. Hikers can use it to view the top of a hill or a faraway cottage.

Similarly, Hunters can stalk prey with a binocular and wildlife admirers can do bird watching with it. In addition, even the military uses a binocular for targeting a faraway checkpoint.

All of these features make a Binocular an important piece of item.  You can do various other things with it as well.

For instance, a binocular can also be used for science experiments and explaining the various laws of light to students. Alright, with that out of the way, let us now see how exactly a binocular is constructed.

Also, check- 7 Best Binoculars Under $200 Reviews

Basic Construction of a Binocular

A binocular basically has three main parts:

  • An eyepiece (also known as an Ocular) for focusing and making the virtual image seem big.
  • Prisms for correcting the image’s shape.
  • Objective lens for collecting light and concentrating that light in a focal point. This makes the image sharper. Usually, 2 more lenses are used for better viewing.

These parts can further be divided into two main systems the Mechanical System and the Optic System. The mechanical system of a Binocular has all the moving parts and it is the main system that lets you properly use the device while the optical system does the actual work of magnifying the image. Let’s take a detailed look at them.


So, there you have it. These are the main parts of a Binocular. These parts are incredibly useful for the overall working of the device. If you own a binocular, you should know the inner workings of it so, if you have to fix a binocular tomorrow, it would be easy to do so.

Also, check- What Do The Numbers On Binoculars Mean?

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