presentation about the construction and use of binoculars

Modern binoculars consist of two barrel chambers with an objective lens, eyepiece, and a pair of prisms inside. The prisms reflect and lengthen the light, while the objective lenses enhance and magnify images due to stereoscopic vision.

Man has been experimenting with glass since its advent sometime around 3500 B.C. These experiments soon became known for their ocular implications. The designs of early optical instruments, like the telescope, were not recorded. It is assumed that these instruments were studied and perfected by Galileo Galilei. Early binoculars were actually called binocular telescopes, and are thought to be based on Galileo's discoveries and designs of prisms.

Early telescopic lenses were full of bubbles and other imperfections. They were also slightly green due to the iron content in the glass. Polishing techniques were crude, and although lenses were of good quality in the center, the peripheral shape was poor resulting in a restricted aperture. As telescopes were improved, binoculars evolved. The first patent application for binocular telescopes was filed early in the seventeenth century by Jan Lippershey in present day Holland. Lippershey primarily used quartz crystal, which is hard to manipulate. The first hand-held binocular originated in 1702 with Johann Zahn's small binocular of two tubes with a lithe connection.

A patent application submitted in 1854 by Ignatio Porro began the use of the modern prism binocular called the Porro prism erecting system. This optical system consisted of an objective lens and ocular lens (eyepiece) with two facing, right angle prisms arranged to invert and correct the orientation of the image. The two most commonly used prism systems are the porro prism and the roof prism design. The roof system uses prisms positioned one over the other resulting in a more compact design.

An other major breakthrough occurred in 1894 when Carl Zeiss, a German optical specialist, developed binoculars with convex lenses and delta prisms to correct the inverted image. In a porro design, the light is bent in a "Z" shape before reaching the eye, allowing the distance between the eyepiece and the objective lens to be compacted. This enables the size and weight of binoculars to be reduced.

Reductions in the weight of the binoculars occurred with the use of aluminum or polycarbonate housings instead of the heavier metal alloys used in pre-civil war binoculars. Performance of smaller and larger binoculars has improved with the introduction of coatings to render the lenses non-reflective and reduce the amount of scattered light. The quality of prisms has also improved over the years, resulting in a reduction of the bubbling effect of optical glass. In the early 1970s, nitrogen filled, waterproof binoculars were developed. A decade later the arrival of infrared transmitters capable of seeing in the dark further transformed binocular technology. Variable magnification models were also developed allowing the user to adjust the level of magnification.

Raw Materials

Modern-day binocular tubes are primarily made out of aluminum coated with silicon or a leather-like material called gutta-percha. The lenses and prisms are made from glass and coated with an anti-reflective coating.

With the exception of the optical glass and some rubber seals, the majority of binocular component parts can be manufactured using a Computer Assisted Design and Manufacturing (CAD/CAM) system that downloads the designs to a variety of Computer Numerically Controlled (CNC) devices (multi-axis mill turn and milling machines as well as vertical and horizontal machining centers, lathes, etc.). Using CAD software provides both drawing, dimensioning, and visualization capabilities. These lead to improvements in the binoculars final design.

The Manufacturing Process

• The lens material is poured into a lens mold, which has a spherical curved bottom. This results in a lens that is about 4 in (10.2 cm) in diameter and 1-1.5 in (2.4-3.8 cm) thick.
• The lenses are then removed from the molds and cut into specific pieces using a diamond saw to create the optical lenses.
• The lenses are placed into the grinding machine and polished.
• After they have been carefully machined, the lenses are anodized to reduce reflections in vacuum tanks. The more coatings applied, the less light absorbed.
• The ocular lenses (nearest the eyes) are also molded and carefully polished by auto-polish machines after which they are centered on diamond turning machines and finally cleaned by running through several different solvents in automated machinery.
• The objective lenses, those furthest from the eyes, are molded and then polished with polishing machines.
• These components are then manually assembled into a die cast body, which is often made from aluminum.
• Using a technique called physical vapor deposition, the optics are placed into a "plasma machine" and coated with dielectric coatings. The coatings are essential for high performance.
• The optics are then inspected and tested for clarity and defects using lasers in specially designed particulate free rooms.
• Next, the rod shaped prisms are cut by lasers into three-sided shapes depending on the type of prism being manufactured (i.e., roof prisms or porro prisms).
• The prisms are coated with dielectric materials (metal oxides) by physical vapor deposition inside a vacuum chamber.
• When all these components are assembled on a belt assembly line, the final assembly station collimates the binocular by hand, making the left side exactly parallel to the right, so only one image will be seen at a time.
• The binocular housing is then covered with a substance called gutta-percha, which looks like leather but is more durable and flexible. This covering is applied by hand using an adhesive and may be coated with a protective rubber covering.
• On the assembly line bare metal housing covers are covered with plastic or rubber.
• The prisms are placed by hand inside the binocular casing and manually screwed in place.
• The objective lenses are held in place by a metal or plastic ring and the eyepiece is fitted with a rubber eyecap.
• The focusing lenses are placed in the housing with screws mounted by hand.
• Waterproof binoculars must have orings at every orifice, be purged with nitrogen (injected through a seal), and sealed. The final step would be the packing of binoculars in cases with neck straps, most cases today being of a canvas-like material.

Quality Control

Binoculars that have been hermetically sealed (waterproof) and nitrogen charged (fogproof) are tested underwater. Most binoculars will withstand water immersion at 16.4(5 m) for five minutes. Both barrels of a binocular need to be optically parallel for the image to merge into one perfect circle and are carefully checked for alignment.

Byproducts/Waste

Lenses and prisms that have defects such as scratches or cracks are either discarded and melted down to be molded again, or they are recycled. If the casing is damaged during production, it is also either remolded or recycled.

Binoculars continue to advance with new technology. Their ability to see further with better focusing techniques enables the consumer to use the product for a wider variety of tasks. Binoculars are now tending to use the same stabilizing method used in video cameras that automatically stabilizes the prism system so that the image remains steady to the viewer. Some binoculars are also coming equipped with night scope vision. This would enable the consumer to see objects that are far away even at night. Technological advancements are continually made on these specialty binoculars, which are primarily used by the military or for surveillance.

Where to Learn More

Bell, Louis. The Telescope. McGraw-Hill Book Company, Inc., 1922.

Von Rohr, Moritz. Die Binokularen Instrumente. Berlin: Springer, 1920.

The United States Patent Office Web Page. November 2001. < http://www.uspto.gov/patft >.

Van Helden, Albert. The Telescope. 1995. November 2001. < http://es.rice.edu/ES/humsoc/GalileoiThings/telescope.html >.

Bonny McClain

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• U.S. Naval Institute - The Selection and Use of Binoculars
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binoculars , optical instrument, usually handheld, for providing a magnified stereoscopic view of distant objects. It consists of two similar telescopes , one for each eye, mounted on a single frame. A single thumbwheel may control the focus of both telescopes simultaneously, and provision may be made for adjusting the focus of each separately to allow for varying characteristics in the two eyes. Binoculars are designed to give an upright view that is correctly oriented left-to-right. Because they allow use of both eyes in a natural way, they are more comfortable than single telescopes, provide depth perception, and improve visual acuity by giving the human visual system two sets of data to process and combine.

In most binoculars, each telescope is provided with two reflecting prisms . The prisms reinvert, or erect, the inverted image supplied by the objective of each telescope. They prescribe a folded path for the light rays, allowing a shorter overall length for the instrument. When the prisms used are of the Porro type ( see optics: Reflecting prisms ), they also provide better depth perception at greater distances by allowing the two objectives to be set farther apart than the eyepieces. The arrangement of these prisms and the other optical components is shown in the illustration .

The primary optical characteristics of a pair of binoculars are commonly described by two numbers, the first of which is followed by a multiplication sign—for instance, 7×50. The first number indicates the magnification (e.g., 7×, meaning “7 times”) and the second the diameter of the objective in millimetres (1 inch is about 25 millimetres). This latter figure is a measure of the light-gathering power of the instrument. For a given magnification, larger objectives produce a brighter image in dim light but also create a more massive pair of binoculars. Handheld binoculars designed for typical uses such as hunting, sports watching, nature study, or amateur astronomy range from about 6×30 to 10×50. Instruments having greater magnifications and light-gathering power are too heavy to hold steady, especially for long periods, but they can be fixed to a tripod or other mount.

In applications in which depth perception is not important, a single telescope, called a monocular, may be employed. It is essentially one-half of a pair of binoculars and usually incorporates prisms in the light path.

Opera glasses and field glasses are binoculars with simple, often inexpensive lens systems and narrow fields of view and are usually made with magnifications of 2.5× to 5×. The lenses used in most binoculars are coated on some or all of their air-to-glass surfaces to reduce reflections.

How Do Binoculars Work: A Step-by-Step Guide to Understanding the Physics, Numbers, and Function

Binoculars are fascinating optical devices that allow us to observe distant objects as if they were right in front of us. Whether you’re a nature enthusiast, birdwatcher, stargazer, or sports fan, binoculars play a pivotal role in enhancing your visual experience. But have you ever wondered how these optical marvels work, both in terms of physics and numbers? In this comprehensive guide, we will delve into the intricacies of binoculars, exploring their construction, the physics behind their operation, and their various uses. So, fasten your seatbelts, as we embark on a journey to uncover the secrets of these remarkable optical instruments.

Table of Contents

Understanding the Basics: What are Binoculars?

Before diving into the inner workings of binoculars, it’s important to understand what they are. Binoculars, often colloquially referred to as “binos,” are a pair of handheld optical devices that consist of two telescopes mounted side by side. These optical instruments are designed to provide a magnified view of distant objects, making them appear closer and more detailed than they would to the naked eye. The beauty of binoculars lies in their portability and ease of use, making them an ideal choice for various activities.

The Physics Behind Binoculars

The fundamentals of optics.

At the core of understanding how binoculars work is the science of optics. Binoculars are essentially two refracting telescopes that use lenses and prisms to bend and magnify light. This optical magnification process is based on the principles of refraction, which occurs when light passes through different media, such as glass or air.

Objective and Eyepiece Lenses

Binoculars consist of two main optical components: the objective lens and the eyepiece lens. The objective lens, located at the front of the binoculars, collects and focuses light from the distant object you’re observing. It forms an inverted real image inside the binoculars. The eyepiece lens, positioned near your eyes, further magnifies the image created by the objective lens, making it appear right-side-up.

Prisms and Their Role

To ensure that the image is upright when it reaches your eyes, binoculars utilize prisms. Prisms are glass or optical elements that reflect and invert the image, allowing for a comfortable and natural viewing experience. The most common types of prisms used in binoculars are Porro prisms and roof prisms.

How Binoculars Magnify Images

The magnification power of binoculars is determined by the relationship between the objective lens and the eyepiece lens. This relationship is represented by the ratio of focal lengths of these two lenses. For example, if the focal length of the objective lens is 50mm and that of the eyepiece lens is 5mm, the binoculars will have a magnification of 10x.

The magnification factor dictates how much larger the image will appear compared to what you can see with the naked eye. For a 10x binocular, the image will appear ten times closer and larger than it would to the unaided eye.

Deciphering the Numbers: How Do Binoculars Work Numerically?

When shopping for binoculars, you’ll often encounter a series of numbers and specifications. Understanding these numerical values is crucial in choosing the right pair of binoculars for your specific needs.

Magnification Power

The first number in the specification, such as 8x or 10x, represents the magnification power of the binoculars. As mentioned earlier, an 8x binocular will make objects appear eight times closer than they would to the naked eye, while a 10x binocular will magnify them ten times.

Objective Lens Diameter

The second number, like in 8×42 or 10×50, indicates the diameter of the objective lens in millimeters. A larger objective lens lets in more light and provides a brighter image, which can be advantageous in low-light conditions.

Exit Pupil Size

The exit pupil size is calculated by dividing the objective lens diameter by the magnification. It determines the amount of light that enters your eye and is important for low-light situations. A larger exit pupil size is desirable for better performance in dim conditions.

Field of View

The field of view represents the width of the area you can see through the binoculars at a specific distance. It’s typically expressed in feet or meters at a specific distance (e.g., 420 feet at 1,000 yards). A wider field of view allows you to observe a larger area at once, making it easier to track fast-moving subjects or survey landscapes.

The Construction and Working of Binoculars

Objective lens.

The objective lens is responsible for capturing and concentrating the light from the object you’re observing. It’s usually larger in diameter and placed at the front of the binoculars. The size of the objective lens affects the amount of light that can enter the binoculars, directly impacting image brightness and clarity.

Prisms play a crucial role in the design of binoculars, allowing for a more compact and streamlined form. Porro prisms, which are shaped like a “Z” or a “W,” are traditionally used in Porro prism binoculars. Roof prisms, which have a straight-line design, are employed in roof prism binoculars. Both types of prisms invert the image and ensure it appears upright when it reaches your eyes.

Eyepiece Lens

The eyepiece lens magnifies the image formed by the objective lens, allowing you to see distant objects clearly. It also incorporates the eyecups, which can be adjusted for your comfort, especially if you wear eyeglasses.

Focus Mechanism

Binoculars have a focusing mechanism that allows you to bring the image into sharp focus. There are two types of focus mechanisms: center focus and individual focus. Center focus binoculars have a central knob for adjusting both eyepieces simultaneously, while individual focus binoculars require you to adjust each eyepiece independently.

Binocular Coatings

Modern binoculars are often coated to enhance image quality. These coatings reduce glare and reflections, improve light transmission, and protect the lenses from scratches and dirt. Common coatings include anti-reflective coatings, phase coatings for roof prisms, and dielectric coatings for increased light reflection.

How Do Binoculars Work: A Step-by-Step Process

Now that we’ve covered the basic components of binoculars let’s take a closer look at the step-by-step process of how binoculars work:

Step 1: Gathering Light

The objective lens gathers light from the object you’re observing. It’s responsible for collecting as much light as possible, ensuring a bright and clear image.

Step 2: Inversion of Image

As the light passes through the objective lens, it forms an inverted real image inside the binoculars. This is where the prisms come into play. They reflect and invert the image so that it appears right-side-up when it reaches your eyes.

Step 3: Magnification

The eyepiece lens magnifies the inverted image formed by the objective lens. The magnification factor, determined by the focal lengths of these lenses, determines how much larger the image will appear.

Step 4: Diopter Adjustment

To accommodate differences in individual eyesight, binoculars often come with a diopter adjustment. This allows you to fine-tune the focus of one eyepiece independently, ensuring that both your eyes see a sharp image.

Exploring Binocular Diagrams

For those who are visually inclined, binocular diagrams provide a visual representation of the internal components and their arrangement within the binoculars. These diagrams can be a valuable resource when studying the construction and operation of binoculars.

In this diagram, you can see how the objective lens, prisms, and eyepiece lens are positioned within the binoculars. It’s important to note that the actual layout may vary between different binocular models, but the fundamental principles remain the same.

A Glimpse at the Uses of Binoculars

Binoculars have a wide range of applications and are employed by enthusiasts and professionals in various fields. Here are some common uses of binoculars:

Birdwatching

Birdwatchers use binoculars to get a closer look at birds in their natural habitat. The magnification and clarity of binoculars make it easier to identify and appreciate the details of various bird species.

Astronomers and stargazers use binoculars for observing celestial objects such as stars, planets, and the moon. Binoculars provide a wider field of view than telescopes, making them great for scanning the night sky.

Sports and Events

Sports fans use binoculars to get a closer view of action on the field or track. Binoculars are also handy for concerts and other live events, allowing you to enjoy the performance up close.

Outdoor Adventures

Hikers, campers, and outdoor enthusiasts use binoculars to survey landscapes, spot wildlife, and plan their routes. Binoculars help them navigate and appreciate the natural beauty around them.

Hunters use binoculars to scout and track game from a safe distance. Binoculars provide the necessary magnification and clarity to identify targets and assess their surroundings.

Binoculars are remarkable optical instruments that blend the beauty of physics with the precision of numerical specifications. Their construction and operation are a testament to human ingenuity, enabling us to explore the world and the cosmos from the comfort of our hands. Whether you’re a nature lover, sports aficionado, or astronomy enthusiast, binoculars open up a world of closer, clearer, and more detailed observations. So, the next time you pick up a pair of binoculars, you can appreciate not only the view but also the science and technology that make it all possible. Happy exploring!

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by Chris Woodford . Last updated: February 14, 2024.

W hat if you could walk on the Moon or stare an elephant right in the eye? Binoculars and telescopes are the next best thing. They take you up to the action without having to move a muscle. Binoculars are based on the science of optics and some pretty clever tricks that lenses pull on light . But how exactly do binoculars zoom you from your armchair to the middle of the solar system? Let's find out...

Photo: Reflections of a passing ship in a large pair of binoculars onboard the USS Sioux. Photo by Juel Foster courtesy of US Navy and DVIDS .

How binoculars use lenses

The way light bends when it goes from air to a different material (such as water or glass ) is called refraction . (For a full explanation of how it works, please see our detailed article on light .) Refraction is the key to how lenses work—and lenses are the key to binoculars, telescopes, and glasses. But how do we get from light bending in water to a cool pair of binoculars that let us study the moon?

Water sitting in a glass appears to have a straight upper edge, even though it is very slightly curved (the curved edge has a special name: it's called a meniscus ). If you place a glass on top of a newspaper and look straight down, the news print looks just the same as normal. That's because the top of the water is effectively straight. But if the water had a curved upper surface, the news print would look magnified. You can see this for yourself by trying the simple activity "Make a water lens" in our main article on lenses .

Photo: New technology is constantly making old inventions obsolete, but there's still no substitute for a really good pair of binoculars. Photo by Brooke Moeder courtesy of US Air Force .

Types of lenses

Photo: Lenses come in all shapes and sizes. The giant Fresnel lens surrounding a lighthouse lamp are designed to concentrate the light into a parallel beam so you can see it at a great distance. The lenses in binoculars do the opposite job, focusing light rays from far off so you can see distant things more clearly. Read more about how Fresnel lenses work .

A lens is a curved piece of glass shaped a bit like a lentil. (If you ever wondered where a lens gets it name from, that's where: lens comes from the Latin word for lentil.) When light rays hit a glass lens, they slow down and bend. If the lens curves like a lentil (like a dome), so its outside is thinner than its middle, it's called a convex lens . As light rays enter a convex lens, they bend in toward the middle—as though the lens is sucking them in. That means a convex lens brings distant light rays into a focus. It's also called a converging lens because it makes light rays come together (converge). Looking at things through a convex lenses makes them appear bigger—so convex lenses are used in things like magnifying glasses.

Another kind of lens curves the opposite way, with the middle thinner than the outside. This is called a concave lens . (You can remember this easily if you think that a concave lens caves in in the middle.) A concave lens makes light rays spread out like the lines of a firework . Imagine light rays coming into a concave lens and then shooting out in all directions. That's why a concave lens is sometimes called a diverging lens . It makes light rays shoot out (diverge). Concave lenses are used in movie projectors to make light from the film spread out and cover a bigger area when it hits the wall.

The optics of binoculars

Photo: Key features of field glasses. You focus by turning the focusing screw in the middle. This pushes the focusing mechanism back and forward, increasing the distance between the objective lens and the eyepiece lens.

You can probably see where we're heading. If you want to see something in the distance, you can use two convex lenses, placed one in front of the other. The first lens catches light rays from the distant object and makes a focused image a short distance behind the lens. This lens is called the objective , because it's nearest to the object you're looking at. The second lens picks up that image and magnifies it, just like a magnifying glass magnifies an image on paper. It's called the eyepiece. If you put the two lenses in a closed tube, hey presto, you have a telescope. You can make your own telescope easily enough with a couple of magnifying glasses and a cardboard tube wrapped around them. Binoculars are simply two telescopes side by side, one for each eye.

Artwork: How to make a telescope from two lenses. The objective lens makes a focused image of the object. The eyepiece lens makes the image bigger.

But there's a catch. When light rays from a distant object pass through a convex lens, they can cross over. That's why distant things sometimes look upside down if you look at them through a magnifying glass. The second lens doesn't sort out that problem. So binoculars have a pair of prisms (large wedges of glass) inside them to rotate the image through 180 degrees. One prism rotates the image through 90 degrees (flips it onto its side), then the next prism rotates it through another 90 degrees (flips it onto its side again), so the two prisms effectively turn it upside down. The prisms can either be arranged in a back-to-back arrangement (known as roof prisms ) or at 90 degrees (known as Porro prisms ).

Artwork: How prisms correct the inverted image and turn it the right way up. The eyepiece lens takes the corrected image from the prisms and magnifies it, as before.

Artwork: The path that light rays take through the lenses and Porro prisms in a typical pair of binoculars. It's not that clear from our artwork, but one of the prisms is arranged at 90 degrees to the other (in other words, one is mounted horizontally and the other vertically).

The prisms explain why binoculars are heavy and why they are sometimes quite chunky in the middle. Field glasses, which are compact binoculars like the ones shown in the photo here, flip the incoming images using only lenses. There are no prisms, so field glasses are smaller, lighter and more compact—but the image quality is poorer.

Artwork: Key features of a typical pair of Bushnell Porro prism binoculars. Right: You can see the objective lens (blue), the two prisms (orange), and the central focusing screw (red). Left: The eyepiece focusing mechanism (yellow) is pulled out and shown in more detail. Now you can see the two eyepiece lenses, the compound ocular lens (top) and the field lens (bottom), separated by an air gap that increases or decreases as you turn the focus ring (mounted on the outside of the eyepiece). Artwork from US Patent 3,744,872: Binocular with improved prism mount by Alfred Akin and David Bushnell, July 10, 1973, courtesy of US Patent and Trademark Office.

How to choose a pair of binoculars: a quick buying guide

Photo: An inexpensive pair of field glasses.

The choice is big and baffling! So which binoculars do you buy? I've bought two pairs of binoculars in the last few years—a really good compact, waterproof pair with roof prisms and a small, cheap pair of field glasses. I spent a long time researching the subject and getting confused by all kinds of unhelpful sales literature. I'm still no expert, but these are the handy tips I managed to figure out for myself:

• My number one tip is that binoculars you use constantly are better than ones that sit in the car or the closet because they're too heavy or cumbersome to carry or because they're so expensive you're afraid to take them anywhere.
• It's vitally important to decide why you want the binoculars and how you will use them before you start.
• If you want something for carrying in your pocket on walks, on the off chance you might see an elephant walking down Fifth Avenue, I'd go for a small and inexpensive pair of field glasses that magnify perhaps eight times.
• If you want to do some serious birdwatching or astronomy, with your binoculars used in a hide or a static location, invest in something heavier, better quality, and more expensive.
• If you plan to look through your binoculars for any length of time (such as when you're birdwatching or stargazing), good quality lenses are worth the investment. Don't wreck your eyes. If you're just going to be looking at the odd bird here and there, cheap field glasses are fine.
• Don't assume that "more magnification" means "better binoculars". The more the lenses magnify, the more the effect of your hand movements will be magnified too. In other words, buy something that magnifies more than about 8 or 10 times and you may find it impossible to keep the lenses steady enough to see anything at all. Higher magnification binoculars also show you less of the scene at a time (because it's bigger). In other words, they have what's called a smaller field of view. Steer clear of buying binoculars in newspapers with amazing sounding magnifications (20 times, 30 times, or whatever it might be); they're probably impossible to keep steady and focused.
• Binoculars are described with two numbers separated by an x. For example, the field glasses in the photo above are 8 x 21. The first number is the magnification. So they magnify up to eight times. The second number is the size of the objective lens in millimeters. So my field glasses have an objective lens 21mm across. The bigger the objective lens, the more light enters, so the brighter the object will appear. Whether you want objects to look bright depends on whether you want to study the full moon (which can look almost blindingly bright through binoculars) or birds at dusk. Again, considering what you will use your binoculars for is all important. Binoculars marked 8 x 42, 7 x 42, or 7 x 50 are great for all-round general-purpose use. However, the bigger the second number, the bigger the lenses—and the heavier (and harder to carry) your binoculars will be.

Photo: Try binoculars before you buy to make sure you like the feel of them.

• Will you always use your binoculars on dry days... or sometimes in the rain? If you're a hardcore birder, you'll need weather-proof and fogproof binoculars, filled with anti-fogging argon or nitrogen gas (to stop them steaming up), and fitted with rubber grips and good rubber eyecups to make a tight seal around your eyes. If you're out and about in very wet environments, you might want to make sure your binoculars are fully waterproof when fully immersed for short or long periods.
• Don't buy online until you're tried them in a shop. Go into a shop and try a few different models. See how you like them (especially their weight and general feel). Make a note of ones you like and then buy online if you want to.
• Good binoculars are great, but small, light field glasses are—in my view—unbeatable. They're small enough to put in your pocket and light enough to carry. There's no risk of missing that golden eagle, red kite, or baby dolphin!
• The best solution should be obvious to you now: if you can afford it, buy a pair of fantastic binoculars for "best" and a pair of cheap field glasses to carry in your pocket.

If you liked this article...

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For older readers

• Philip's Stargazing with Binoculars by Robin Scagell, David Frydman. Firefly, 2014. A practical guide that includes chapters on choosing and using your binoculars.
• A Buyer's and User's Guide to Astronomical Telescopes and Binoculars by James Mullaney. Springer Science, 2013. Chapter 2 (Binocular Basics) is a good introduction to binocular optics that also covers binocular telescopes. The original 2006 version of the book has been completely updated so the buying information is, once again, nicely up to date.
• Finding Your Wings: A Workbook for Beginning Bird Watchers by Burton S. Guttman. Houghton Mifflin Harcourt, 2008. A very active, practical guide to birdwatching that includes details of how to choose and use binoculars.
• Exploring the Night Sky with Binoculars by Patrick Moore. Cambridge University Press, 2000. A classic introductory guide for amateur astronomers.

For younger readers

• Astronomy for Kids: How to Explore Outer Space with Binoculars, a Telescope, or Just Your Eyes! by Bruce Betts. Callisto Media, 2021. A great hands-on guide to the sky for ages 7–13.
• Binoculars by Robin Koontz. Rourke, 2014. A simple introduction for ages 7–10.
• Scientific Pathways: Light by Chris Woodford. Rosen, 2013 (previously published by Blackbirch in 2004). One of my own books, this sets out the logical sequence of scientific discoveries from ancient Greek ideas about optics to modern fiber optics (for ages 9–12).
• How Telescopes, Binoculars, and Microscopes Work by Ryan Jacobson. Child's World, 2011. A 32-page guide that puts binoculars in a broader context with other optical instruments. Ages 7–10.
• The Next Generation of Digital Smart Optics Promises to Replace Traditional Scopes and Binoculars by Scott Einsmann. Outdoor Life. February 5, 2024. How GPS, Lidar, AI, AR, and other new tech will boost the power of your binoculars.
• World's First-Ever Smart Binoculars Can Identify 9000 Birds Thanks To Built-In AI . MSN Money. January, 2024. AI will soon come as standard on binoculars; here's a glimpse of the tech future!
• Binoculars That Use Digital Trickery to Give You Super-Sight by Christina Bonnington. Wired. January 21, 2015. New binoculars use digital image processing to reduce fuzziness caused by rain, wind, and other atmospheric distractions.
• Pentagon to Merge Next-Gen Binoculars With Soldiers' Brains by Sharon Weinberger. Wired. May 1, 2007. The latest military binoculars pick up signals from the wearer's brain for hugely improved image detection.
• David Bushnell, 92, Importer of Affordable Binoculars, Dies by Jennifer Bayot. The New York Times. March 31, 2005. The story of how David Bushnell put binoculars in the hands of the masses.
• The Neurophysiology of Binocular Vision by John D. Pettigrew, Scientific American, Vol. 227, No. 2, August 1972, pp. 84–96. A great, very clear introduction to how our eyes and brains enable our 3D visual perception.
• US Patent 395,872: Binocular glass by James Briggs, January 8, 1889. An early design for field glasses that sit on your nose like a pair of spectacles.
• US Patent 3,531,177: A binocular construction using plastic foam and magnets by Alfred Akin (Bushnell), September 29, 1970. A design for lightweight, inexpensive, shock-absorbing, floating binoculars based on using plastic foam as the body material.
• US Patent 3,744,872: Binocular with improved prism mount by Alfred Akin and David Bushnell, July 10, 1973. A typical Porro prism design from one of the pioneers of affordable binoculars, David Bushnell. This gives a good description of all the bits you'll find in modern binoculars and what they all do.
• US 20020109785: Digital record and replay binoculars by Jack and Steven Hammack, August 15, 2002. Binoculars with built-in digital recording and a viewing screen.

Text copyright © Chris Woodford 2007, 2020. All rights reserved. Full copyright notice and terms of use .

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How Do Binoculars Work?

Optics behind the binoculars, different types of binoculars, a final word.

Binoculars cleverly use the concept of optics to enable us to view distant objects with ease. Their design is based on the principles of light refraction.

As a kid, I always wanted to own a super-cool pair of binoculars that the S.H.I.E.L.D. agents used in Marvel movies. Imagine being able to look through walls and see every technical detail of your surroundings.

Binoculars may not be superhero-level tools, but they cleverly use the science of optics to zoom you inside an anthill or out to the middle of the Milky Way. In this article, we will learn how exactly this cool gadget works, so that the next time you come across a pair, you’ll know what’s really happening!

Binoculars are essentially a pair of telescopes mounted on a single frame. Though telescopes trace their history back to the 15th century, J.P. Lemeire is credited with the design and patent of the binoculars, which were developed in 1825. Fast forward to 1854, when Ignazio Porro came up with the concept of prism binoculars, which laid the foundation for the incredible technological advancements of binoculars.

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Binoculars work on the concept of light refraction, and the “magic” element is how lenses/prisms effectively implement this property of light.

When light passes through different media, it bends outwards or inwards, depending on the density of the medium through which it’s traveling. This is called the refraction of light. If light travels to a denser medium, it bends inwards, whereas if it travels to a rarer medium, it bends outward.

The glass in the objective lens of the binoculars receives the incident light, and when light passes through them it bends or refracts to form an image. Therefore, the amount of light can be controlled by altering the objective lens. The glass in the eyepiece further receives light through the objective lens and processes its image into the final image perceived by the observer.

Lenses And Magnification

The word lens comes from the Latin word for lentil, in reference to its shape. Therefore, a lens is a piece of curved glass through which light can be transmitted or refracted.

Primarily, there are two types of lenses—convex and concave.

The convex lens is thicker in the middle and thinner towards the sides. This construction helps light refract inwards and allows for focusing distant rays into a smaller region, forming a small image of the distant object. It is used as the objective lens of the binoculars.

The concave lens, on the other hand, is thinner in the middle and thicker towards the side. The light refracts outwards, forming comparatively larger images of smaller objects. Hence, it behaves like a magnifying glass. The eyepiece of binoculars is made of this type of lens so we can clearly see the image of the object.

Prisms And Their Arrangement

The whole construction of binoculars is now coming together, but there’s a catch. It just so happens that when light from a very faraway object passes through the convex objective lens, it produces an upside-down image, resulting from the crossing over of light. The eyepiece also cannot resolve this problem, so the final upside-down image won’t be of any use. This is where prisms come to the rescue!

A prism is a three-dimensional piece of glass that can rotate and reflect an image. Thus, prisms are deployed in binoculars to rotate the inverted image by 180⁰ and obtain an upright image in the eyepiece. Each prism can rotate light by an angle of 90⁰.

A set of two prisms in each tube is used to obtain the desired image in a pair of binoculars. There are two types of arrangements for the prisms, namely Porro prisms and Roof prisms.

In Porro prisms, the two prisms are arranged side by side at 90⁰. This results in a bulkier structure to the binoculars.

In Roof prisms, the two prisms are arranged in a straight line along the direction of light propagation, which results in more compact binoculars.

Also Read: How Do Different Types Of Telescopes Work?

Putting all the above inferences together, we conclude that when rays of light passing through the objective lens form an inverted image of the distant object, the arrangement of the prisms rotates it by 180⁰ and the eyepiece, in turn, produces a magnified image of the initial image, enabling the observer to easily view that object with clarity. This happens for both the left and right tubes of the binoculars.

With advancements in science and technology, devices are becoming better each day. Binoculars have broadened their horizon of versatile use and are now classified into some specialty categories listed below:

Mini Binoculars

These are portable and can be stuffed into your backpack quite easily. They may be not as powerful as the full-sized ones, but still serve the purpose of magnification quite well.

Zoom Binoculars

These types of binoculars specialize in changing the magnification of the lenses according to your requirements and are able to zoom in on objects.

Wide-Angle Binoculars

As the name suggests, these binoculars have a wider field of view than normal binoculars, enabling you to cover a better range to spot objects in open spaces. These are ideal for wildlife and game spotting.

High-powered Binoculars

These are used as an alternative to telescopes by astronomers. They are ideal for long-distance viewing, due to their high level of magnification.

Night-vision Binoculars

These are probably the coolest type of binoculars, as they can enable you to see distant objects in the dark. Used especially by the military or special forces, these binoculars make use of photo-sensitive lenses and photo-cathodes. Thermal imaging may also be available in these binoculars.

Also Read: Which Is Better: Optical Microscope Or Electron Microscope?

Whether a secret agent, a celebrated soldier, or a wildlife enthusiast, when on a mission or adventure, binoculars are as essential tool. The ability to see what you want beyond the physical limitations of the human eye is quite fascinating.

Let’s just hope that someday, we can have a device that fits into our eye lens and automatically turns it into a binocular. That ability may not be far away, as technology is evolving fast!

Also Read: Want Eagle Vision? Here Are Some Traits You’d Need.

• How do binoculars work? - Socratic. Socratic
• What Do Numbers on Binoculars Mean? - A Detailed Guide [Upd. 2022] - theoptics.org
• How to Use Binoculars (the right way) - Deschutes Land Trust. The Deschutes Land Trust
• Binoculars - New World Encyclopedia. newworldencyclopedia.org

Shreya Chakraborty is pursuing her master’s degree in Physics from NSUT, New Delhi. She is passionate about literature and writing, which allows her to express her scientific interests easily and effectively. She enjoys watching Sci-Fi movies, writing poems and articles, and wondering at the beauty of the night sky.

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Science at work. Binoculars.

Aug 04, 2014

851 likes | 3.74k Views

Science at work. Binoculars. By Skye B roekate. A brief description of binoculars history. . What is a binocular? The first binocular telescope is two telescopes placed side by side. Who developed binoculars first?

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• future changes
• things people
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Presentation Transcript

Science at work. Binoculars. By Skye Broekate

A brief description of binoculars history. • What is a binocular? • The first binocular telescope is two telescopes placed side by side. • Who developed binoculars first? • Johann Lipperhey invented binoculars and is also the inventor of the ordinary Dutch telescope. • When was the first binocular telescope developed? • The binocular telescope was created in 1608. • How has binoculars changed? (got better) • Better coatings for higher transmission of light, better prisms, and wider angle eye lenses have made most of the improvements in the last fifty years. Almost all these ideas originated in Japan

Show diagrams of how the light bends through binoculars . • Use cut away views to show how light is bent: They use the prisms because binoculars are very small and they need to bend the light How does binoculars use lenses to bend light? Modern binoculars consist of two barrel chambers with an objective lens, eyepiece, and a pair of prisms inside. The prisms reflect and lengthen the light, while the objective lenses enhance and magnify images due to stereoscopic vision.

Show diagrams of how binoculars work and explain it. • Binoculars work on the same principles as telescopes. The process begins with a series of lenses. The lenses focus on an object and gather the light from it. As the light passes through a series of lenses, the image gets larger. Binoculars differ from a telescope in that they allow the image to be transmitted to both eyes at once. • Binocular lenses are curved pieces of glass. A binocular can have several lenses; in fact, the more lenses that the binocular has, the better the magnification. Unfortunately, each time the image passes into the next lens, light is lost, so binoculars include a prism that bends and reflects light into the lenses. The prism also flips the image. Without it, everything you see through the lenses would be upside down

Explain where binoculars are used is used. • Who uses binoculars and what do they use them for? • binoculars are used for viewing distant objects and to bring far-away Images up close. • Some of the things people use binoculars for is: • Galilean opera glasses, used in theatres, • for typical outdoor use e.g. Bird watching • Hunters and bird watchers rely on binoculars to bring their quarry into clear detail • sports fans often bring binoculars to the event so they don't miss one moment of action.

What future changes are expected to be made to binoculars in the future. • Binoculars continue to advance with new technology. Their ability to see further with better focusing techniques enables the consumer to use the product for a wider variety of tasks. Binoculars are now tending to use the same stabilizing method used in video cameras that automatically stabilizes the prism system so that the image remains steady to the viewer. Some binoculars are also coming equipped with night scope vision. This would enable the consumer to see objects that are far away even at night. Technological advancements are continually made on these specialty binoculars, which are primarily used by the military or for surveillance.

Bibliography • http://wiki.answers.com/Q/Who_invented_binoculars_and_when#ixzz1y7IA6V2N • http://en.wikipedia.org/wiki/Binoculars • http://www.life123.com/technology/home-electronics/binoculars/how-do-binoculars-work.shtml • http://www.madehow.com/Volume-7/Binocular.html#ixzz1yODVPoCx • http://www.madehow.com/Volume-7/Binocular.html

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Introduction

How Binoculars Work

Most binoculars contain a series of lenses and prisms . Lenses are circles of curved glass. Prisms are pieces of glass with several flat sides. The lenses and prisms change the direction of the light going through them. The lenses and prisms together change the image of the object being viewed.

When someone looks through a pair of binoculars light enters through a lens, called an objective lens, in each side. The objective lenses turn the image being viewed upside down. Then the light passes through the prisms. The prisms turn the image right side up and reflect it toward eyepieces. Finally, the light passes through the eyepieces into the eyes. The lenses in the eyepieces make the image look bigger. A ring located between the eyepieces lets the user adjust the focus of the binoculars. Focusing makes objects look clearer. The ring works by changing the distance between the eyepiece and the prisms.

How Binoculars Are Used

The size of the lenses is important, too. Larger lenses allow more light to enter the binoculars. This makes them work better at night or in dim light. However, larger lenses are also heavier. This makes the binoculars harder to carry and harder to hold steady. Smaller lenses might not be best for night viewing, but they are easy to hold and to carry.

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Binoculars - PowerPoint PPT Presentation

Amount of light transmitted through the binoculars in millimeters (mm) ... http://www.meade.com/manuals/binoc/ Binoculars. Questions or Comments? ... – PowerPoint PPT presentation

• An Informative Insight to a Powerful Tool
• By Chris Robb
• Binoculars - An optical device designed for simultaneous use by both eyes
• Consists of two small telescopes joined with a single focusing device
• They are used to magnify a distant object
• Telescopes generally have inverted images
• Binoculars use prisms for image-erection
• Two Styles Roof and Porro
• Prisms overlap closely for straight alignment
• More costly due to need for precise alignment
• Objective lenses are offset from the eyepiece
• Greater 3-D view and image depth
• Power and Light 10X42
• Power 10X (Magnification)
• Light Collection 42mm Objective Diameter (OD)
• Exit Pupil OD/Power 4.2mm
• Amount of light transmitted through the binoculars in millimeters (mm)
• Pupil Diameter Noon 2-4mm Evening 7mm
• Larger exit pupil helps for twilight viewing
• Field of View (F.O.V)
• Side-to-side measurement of viewing field _at_ 1000 yards.
• Distance in millimeters (mm) a binocular can be held away from the eye _at_ full F.O.V.
• A large eye relief will reduce eyestrain and is ideal for a person that wears eyeglasses.
• Coated, Fully Coated, Multi-Coated, Fully Multi-Coated, and Phase Coated
• Fully Multi-coated will give better performance i.e. enhanced contrast light transmission
• Digital Information Systems
• Image Stabilization Technology
• Built-in Compass and Video Display Device
• Video, Snapshot and Sound Recording
• LIDAR Ranging
• Light Amplification i.e. Night Vision
• Light Frequency Tuning IR/UV/Visible
• Solar Cell Material Coating for Power Supply
• GPS Location Broadcasting for Lost/Found
• Large Binocular Telescopes
• Possibilities are Endless!!!
• LBT Telescope Video
• http//medusa.as.arizona.edu/lbtwww/ads/mplbt.mpg
• Binoculars Information
• http//www.prairieimages.com/binoculars.htm
• Pictures of Old Binoculars
• http//www.swanseaheritage.net/article/gat.asp?ART ICLE_ID633
• http//www.swanseaheritage.net/article/gat.asp?ART ICLE_ID634
• Victory 8x56 B T Cross-section
• http//www.zeiss.de/C12567A80033F8E4/allBySubject/ 67AE641BBE77EB6BC12569EC00487C27
• Prism Schematics
• http//www.birdwatching.com/optics/binoculars1.htm lHow20Binoculars20Work
• Meade Binocular Diagram Reference
• http//www.meade.com/manuals/binoc/
• Questions or Comments?

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Construction and use of binocular

Binoculars rely on pairs of prism to fold & erect the image in each tube assembly. doubled roof prisms are small and light enough that a pair of binoculars designed around them can have short, straight & lightweight tubes. the use of binoculars is given below:- binocular is used in army, police, etc. the given diagram is a construction of binocular.