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May 02, 2021 | 01:15 am 2043 0

How Do Binoculars Work?

How Do Binoculars Work?

Binoculars work according to the laws of optics - that's clear. But how exactly? If you are interested in understanding a little bit about the physical processes that take place in your device - welcome, let's get to the bottom of it. It's not going to be too complicated and we're not going to quote you Wikipedia or a school textbook. It is going to be simple and to the point.

How Do Binoculars Work?

Binoculars are two telescopes mounted together and provide an image for both eyes. They can come in handy in a variety of situations. Binoculars have always been a popular device, ranging from children's models and theatrical varieties to advanced technical devices for field or astronomical observation. Hunters also use binoculars to observe game. It allows you to locate and observe animals without creating a frightening noise.
The demand for binoculars is quite active, and manufacturers offer many options with many different characteristics. Therefore, before you choose, you need to understand how it works and what the characteristics of the optics mean.


The phenomenon of light rays refracting as they pass from air into water (or any other dense medium such as glass) is called refraction. Lenses work by refraction, and binoculars, telescopes, or glasses work by using lenses. Two telescopes side by side are binoculars. That's about it. But if you look at the construction of binoculars externally, it's easy to see that often its lenses are not arranged in relation to each other in the same row as in a spyglass. The eyepiece tubes are usually slightly shifted in relation to the objective channel. This system gives the user a highly three-dimensional picture.
It should be understood that the lens and the eyepiece are different parts of the binoculars. A larger diameter tube represents the objective lens. It rotates toward the object of study, while the eyepiece is the lens to which the eye looks through.

Magnification of binoculars

Or the degree of magnification of a binocular is one of the main criteria for choosing these optics. The higher the magnification, the farther it is possible to view the object from a greater distance and determine the fine details. Binoculars often have a numerical designation in their name, for example: 20X50. The number 20 means that the device is capable of magnifying the image 20 times. The 50 refers to the size of the objective lens. 
Binoculars that have a magnification correction function also have a numerical designation. For example, 8-24X50 means the optics is capable of magnification within a range of 8 to 24 times.

Close Focus Distance

The close focusing distance is the closest point the binoculars can focus on. This distance varies from 0.5 to 30 yards, depending on the binocular design. If the focusing distance is short compared to the magnification, the binoculars can also be used to view details not visible to the naked eye.

Prism varieties of binoculars

The optical prisms added to the design made it possible to display the image in the correct direction without the need for a large number of lenses and a reduction in the overall length of the instrument. Prism varieties of binoculars are the most widely used today. The two main construction models, the Porro and Roof, invert the image, magnifying it for the observer.
·         The classic Porro-type prisms have a lens and eyepiece that are staggered, providing flexibility, but the binoculars look more bulky. This shape provides better image quality.
·         Roof-type systems are more compact, cheaper and lighter due to the positioning of all elements on one axis, but they lack somewhat in user characteristics.
Sometimes an inverse Porro pattern is used, in which the lenses are shifted closer than the eyepieces. Such models provide high-quality bright images in a smaller size, but their field of view is very small.

Center Focus System

The most common is the central focusing system, which allows you to focus the image synchronously for both eyepiece tubes. In Porro and Roof binoculars, this focusing system is done differently. In case the user has vision defects and his right and left eyes see "differently", an additional design element, the dioptric correction mechanism, is used to compensate for the difference in vision.
Often this dioptric correction ring is located on one of the binoculars' eyepiece tubes, and more often on the right one. By correcting this ring, you can adjust the binoculars precisely to your vision, even if both of your eyes have different medical parameters.

Anti-reflective coatings

Anti-reflective coatings reduce the loss of light on each optical surface by the reflection on each surface. Reducing reflection with anti-reflective coatings also reduces the amount of "lost" light inside the binoculars, which would otherwise make the image cloudy (low contrast). Binoculars with a good optical coating can give a brighter image than uncoated binoculars with a large objective lens because of better light transmission through the assembly.
Standard terminology used in binoculars descriptions:
·         Coated - single-layer coating (usually only on the outer surfaces of the lenses);
·         Fully coated (FC) - single-layer coating on all optical surfaces;
·         Multicoated (MC) is multi-coated on some surfaces, and single-coated on the other surfaces;
·         Fully multicoated (FMC) - multilayer coating on all optical surfaces.
There are other parameters that affect how comfortable and useful binoculars will be. Plasticity, which depends on the interpupillary distance, gives a sense of depth and relief of space, nitrogen-filled bodies will keep lenses from fogging up in fog or damp weather, durability and moisture-resistant characteristics are needed in extreme conditions. Before buying, it is worth imagining how good the ergonomics of the binoculars will be and how much you will like them personally - this question can only be decided based on your own taste.

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