How Binoculars Work: 5 Key Points
Do you know how binoculars work? It’s amazing how one device can let you see distant things as though they’re near.
Binoculars are two telescopes put together side by side, allowing you to see distant objects with both eyes, instead of one as in a telescope.
Before you try to understand how binoculars work, knowing the main parts can help you.
1 – Main Parts
These are the main parts of binoculars and an overview of their specific functions:
- Objective lenses: determine the amount of light the binoculars gather from the object. They capture the light and direct it to the eyepiece, allowing you to see the object.
- Eyepiece Lenses: allows you to focus and enlarge the image.
- Prisms: rotate the image so they can be viewed right side up.
- Focus wheel: they slightly move the interior lenses of the eyepiece to help with focusing and you can have sharper images.
- Diopter knob: as you turn the knob to the left or right so you can adjust the focus of the eyepiece lenses.
- Chassis: the housing or case that holds all these binocular parts together
2 – Refraction
To understand how binoculars work, you need to understand refraction.
Simply put, refraction is a process where the lens captures the light rays and they slow down and bend.
3 – Binoculars Use Convex Lenses
You can control the direction of the light with the shape of the lens. A convex lens curves likes a dome. The glass on the inner part is thicker than the outside.
When light rays strike, they come together in the middle – or they converge. This is why we also call them a converging lens.
A convex lens can make things appear bigger. A magnifying glass uses a convex lens.
4 – The Lenses’ Major Role
A pair of binoculars is made up of two convex lenses, one in front of the other. This allows you to see objects clearly even when they’re far.
The first lens catches the light rays from the object and makes the focused object look nearer behind the lens. They call this the objective lens because it’s nearer to the object.
The second lens picks up the image and magnifies it, just like a magnifying glass.
5 – What Prisms Do
When light rays from a distance pass through a convex lens (the first lens), they cross over. This causes the images to appear upside down.
This is where prisms save the day. Binoculars come with a pair of prisms. These prisms rotate the image 180 degrees.
The first prism flips the image to one side (90 degrees). The next prism rotates it again onto its side (another 90 degrees) until the image is on its right side up.
There are two types of prisms: roof and Porro prisms. The difference is how they are arranged. Roof prisms are in a straight line, back to back each other. Porro prisms have a zigzag design.
In a Nutshell
Binoculars have three vital optical components: objective lens, prism, and eyepiece. They work together so you can see distant objects closer.