How do Binoculars Work: A-Z About Binoculars


Binoculars are a wonder of science that gives you a clear and enriched vision of faraway things and places and takes you closer to the action. Bird watchers and wildlife journalists benefit significantly from this invention. With one, they get to observe nature and its creations more clearly and better, and the other helps to capture the beauty of mother earth.

How the way binoculars work is a pretty interesting topic. Okay, then let’s talk about it. In here, you will know how binoculars work, including how we humans can see distant objects closer through binoculars. How the waves pass through and how the lenses and optics work together. The mechanism of binoculars is quite simple, both in theory and practice. It always fascinated me how the laws of optic works with lenses and light; this article is going to be all about the working science behind a binocular.

The Theory

The weight light Banton’s when light goes through from air to another material, it’s called Refraction and refraction, is the main factor that how to make the lenses working and lenses are also the key to telescopes, glasses, binoculars. But how do we actually can get from light in a water bottle to a binocular? Where light is bent that lets us see things that are far away from our beautiful planet Earth.

Well, binoculars are only two simple telescopes put side by side, each telescope is for each eye, but there’s a limitation when light waves from a distance object passed through the convex lens they cross over that’s why the thing from a distance looks upside down if you look at them through. The other lens doesn’t solve out the problem. So, binoculars have a pair of prism that makes sure the image seems accurate. The lightwave travels as a wave through the binoculars, but unlike the sound wave, our water waves it doesn’t need any matter or material to carry energy along. Meaning, that light can travel through a vacuum, a completely airless space.

The Lenses

To understand binoculars, we need to go way back. The first binoculars were invented in 1825 when a new map of Paris produced a binocular with an internal screw of centrally placed between two monoculars. At the right moment, this screw allowed the users to focus their eyes simultaneously, thus making binoculars easier to adjust. Humans can look through the lenses of binoculars to observe those things that are too far away more clearly that we know today is a common knowledge.

Now the binoculars used two lenses named Convex, and there the first lens catches the visible light waves from distant objects then makes a focus image a little distance just behind the lens. That lens is known as the objective lens. Because it is near to the real object that you are looking at. Now the second lens catch that images then magnifies the image. It is just like magnifying-glass. Magnifies an image on the paper and also keep an image horizontally and vertically.

The Prisms

The triangular prisms used in binoculars between the objective and eyepiece lens are designed in a way so that they face their hypotenuses. Before reaching the focal point, when the light passes through the objective lens, it enters the prisms and lengthens the focal path by carrying out a pinball action through them. We have known and used prisms for 3-dimensional images and, in this case, enhances the image by adding further clarity.

There are two types of prism used in the binocular: 1) Porro Prism 2) Roof Prism. They are different in shapes but mostly work in the same way. The Porro prisms came from its Italian inventor of the same name. Around the mid way of the 19th century, he designed these two prisms to solve the upside-down image problem. He invented the right position to situate both prisms between the eyepiece lens and the objective lens for the telescope.

They were set in such a way that when placed to reverse the image, they also folded the path of light to a more flexible mechanism. However, later at the end of the 19th century, and optic company named Zeiss Optical Works merged the Porro prism idea with glasses to invent the first-ever modern prismatic binoculars. After that more modification have taken in place, at first the prismatic binoculars used to be really heavy, since the prisms the triangular pieces of solid glass, and that considerably added to the weight. As time passed and technology advanced, using binoculars also became more effective, definite, and compact.

Brief Description of How does a binocular work?

So, heading to the practical part now. When you put two convex lenses one after another, it makes images appear closer than they are. The job of the first convex lens is to accumulate light rays from faraway objects and produce a clear, focused image behind the lens in a short distance. While the second lens receives the image and then just like a magnifying glass, it magnifies the image. The first lens, which is the nearest object you’re looking at, is called the objective lens. And when you put both the said lenses in a cubicle, you get a telescope. And that was just the basic.

Binoculars are like two telescopes, one beside another; however, the light from distant objects tend to cross over each other while crossing a convex lens. Now you understand why faraway objects look upside down when you try to look at them through a magnifying glass. Although, as we have already said before, adding another lens does not solve the upside-down problem. That is where the prisms come to work.

So, they used a pair of prisms inside the binocular to rotate the upside-down image to upright. Each prism rotates the image to 90 degrees, and after going through both prisms, the image rotates 180 degrees and transforms back into track again. Different binoculars set the prisms differently; typically, there are two ways they are set up, the back to back arrangement is called roof prisms. And Porro prism is when they are arranged in 90 degrees.

For better understanding, I suggest you get up and about because we got work to do. You’ll need a bright object, suppose the bulb from a table lamp, two magnifying glasses and two pieces of prisms and a tracing paper. Illuminate the bulb and put the magnifying glass in front of it, so the light goes through the glass, the first magnifying glass will work as the objective lens.

Then, take the tracing paper on the opposite of light and magnifying glass, so the glass stays in the middle of tracing paper and light bulb. After you see the reflection of a bulb on the tracing paper, start moving it, and adding to distance, you’ll see that at a certain point, the reflection of the light bulb will be upside down.

Now you’ll see that adding another magnifying glass won’t solve this, but it will surely enlarge it. Put the other glass on the opposite end of the tracing paper; the second glass will magnify the reflection on paper when you look through it, which acts as the eyepiece lens of the telescope. As evident it is, you have a working telescope which makes distant bright object appear closer and brighter.

However, let’s not forget that the image is still backward and upside down. To correct that problem, you’ll need to make use of the two prisms, which is a solid piece of erecting glass that works as a mirror. But unlike the mirror, they do not have a reflective coating, but the light travels through them at an angle, posing two of them at a certain position will enable them to reflect the upside-down image of light as the proper upright one.

Set them before the eyepiece, so the light has to go the prisms first, then the second convex lens. And the object will appear closer and as it is now. Great! You have just learned yourself to make a telescope. And hopefully, you have understood the working theory behind binoculars.


Nowadays the binoculars are not only a tool for astronomers but also for the common people like we are. It is one of the most important extension to the travelers. Most of the people use a pair of binoculars to observe the Mother Nature. Birding is very much enjoyable to the people in this modern era.

Hunters use binoculars with night vision so they can have an advantage in hunting at poor lighting conditions. Binoculars can be a great gift to your bird watcher and nature-loving friends. Presently, the market offers many diversities and a great range of features.

Some offer better diopter adjustment, adjustability at magnification, some are waterproof, and some offer optimal image quality. Just like there are binoculars for professionals, there are also for hobbyists, kids, etc. Now I hope you have gotten the gist of the science behind a binocular, which you’ll remember the next time you’re looking through binoculars.

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