Monday, 9 April 2018
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Tuesday, 27 June 2017
The History Of The Binoculars
Have you ever wondered when binoculars were invented? You would assume that they were created around the same time as the telescope, but parts of the binocular were actually being made as early as the 1200’s. The history of binoculars is not as short as you may think because, whilst the idea has been around for a long time, certain inventions needed to be made before the binoculars were able to give you properly orientated images. Read on to find out about the history of binoculars!
In 1267 a friar called Roger Bacon wrote about his solution to the problem of focusing the eyes on close objects, i.e. the short-sightedness which tends to develop with age. He recommended that sections of glass could be placed on pages of writing to magnify their content, and by the end of the 1200’s craftsmen were already making thin glass sections which would be put into frames so people could wear them in front of their eyes, i.e. the first glasses. As these reading glasses were similar in shape to lentils, they became known as lenses because the word lens is Latin for lentil.
The Invention Of Binoculars
Binoculars were actually built in 1608 by a man called Hans Lippershey in the Netherlands. He created a convex lens and a concave lens which, when combined, could magnify the image of distant objects.
He showed his binoculars to the Assembly of the States-General of the Netherlands and they asked that he create a similar object with two lenses as it would be easier for use in battle. He did indeed create these binoculars, but they had poor resolution and bad magnification and so they didn’t become particularly popular. Lippershey wanted to patent his invention, but he was refused.
The origins of the binoculars may actually go back before Lippershey because around that time you could already buy small spyglasses with a similar design.
During the 17th/18th century, a few inventors had a go at creating smaller telescopes or two piece box telescopes, i.e. binoculars, but they were all pretty bad quality and we don’t know much about them.
Galileo may have actually stolen Lippershey’s idea because just one year later in 1609 Galileo started the process of building a telescope. He eventually created around one hundred telescopes which could magnify up to thirty times, and with these telescopes he was able to observe far away objects including the Moon, Jupiter’s satellites and his invention has lived on ever since.
Galileo’s telescopes were pretty basic by today’s standards. He only used lenses which were curved on one side and his creations have a very small field of view.
The development of binoculars doesn’t seem to have progressed very much until the 1820’s when binocular ‘theatre glasses’ started to become popular. These glasses were based on Galileo’s design, and even though the magnification wasn’t particularly powerful at all it wasn’t really a problem if the spectators only wanted to magnify a nearby stage.
Later on, in the nineteenth century similar binoculars are known as ‘field glasses’ started to be developed. These binoculars were very similar, but they have a slightly higher magnification.
Ignazio Porro is sometimes thought of as the inventor of the binocular because he received a patent in 1854 for his prism system, and without that prism system binoculars may never have become popular.
Porro prisms were created for a variety of optical instruments with the goal of orientating images so they were correct. They normally work as part of a double porto prism system which will reflect the light four times in total.
The prism is made up of right angles, and when the light enters the large rectangular face of the prism it will internally reflect twice so the image has now turned 180 degrees. There is normally a second prism rotated at 90 degrees and it is there to ensure that the light will go through both prisms.
Porro’s prism design is still widely used today. Prisms are necessary for binoculars because without them any images that you see through the binoculars will be upside down and backward! Prisms have a mirror like an effect which reflects the light back and orientates the images so they are the right way up.
Ernst Abbe & Carl Zeiss
Carl Zeiss had been working on building better microscopes since the 1840s Zeiss ran an optics workshop and in 1866 that workshop had sold over 1,000 microscopes. In 1866 he paired up with fellow inventor Ernst Abbe and along with Otto Schott, they worked on improving lenses for multiple optical instruments including microscopes.
Ernst Abbe is the same Abbe of the Abbe-Koenig prism. Their prism is a roof prism and it is basically designed to invert the image so it is no longer upside down. The prism is composed of two glass prisms which are cemented together in a shallow V shape.
The light will enter one side of the prism, it internally reflects 30 degrees, it is then reflected from the roof section of the binocular, and it is reflected again at 30 degrees on the opposite face of the prism. Roof prisms have been around since the late 1800s, but they only started to become popular on the market almost a hundred years ago in the 1980s.
The idea for the binocular is as old as Galileo, but it was only around 200 years later that the idea actually began to take off. Binoculars are very handy because you can look through them with both eyes at once which means you are not distracted by your other eye and you get a sense of depth, so it’s actually surprising they weren’t invented earlier.
Prisms are pretty much essential for binoculars because, whilst it may not matter if the moon, planet or star that you are looking at is upside down, it will probably matter if you are trying to watch live sports at a stadium or if you’re trying to take a closer look at the local (or not so local) wildlife.
Saturday, 3 June 2017
The refraction of light is key to how binoculars work because it explains how lenses work. Refraction is The way light bends when it goes from the air to a different material. Placing a stick in water is a refraction of light because the stick appears bent, however it is not. A lens is a curved piece of glass and when light rays hit a piece of glass such as a lens, they slow down and bend. If the lens curves, 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.
A different kind of lens curves the opposite way, with the middle being thinner than the outside is. 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.
Okay, so hopefully you can 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. 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 basically just two telescopes in one device, but when light rays pass through a convex lens from a distance they cross over. Hence why far away things often look upside down when looking at them through a magnifying glass.
So binoculars have a pair of prisms (big 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)
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.
Is this becoming any clearer?
Less Complicated Break Down
No? Okay so basically the 2 lenses you look through in a pair of Binoculars refract the light in certain ways to capture images from far away to be clearer than they really are. Like glasses lenses help you see things differently, so do Binoculars.