Binoculars: What are They and How Do They Work?
Binocular telescopes, or simply binoculars, are devices that help your eyes get a better look at things. That is, you are given a bigger or magnified image of distant images. It is very similar to normal or what are called monocular telescopes with a few very obvious differences. Well for starters, you should look through it with both your eyes. Another is that it functions in a much more similar manner to your eyes than monocular telescopes.
Our eyes function in binocular vision. Binocular vision is the ability of one’s eyes to look at the same thing and register a single image. This is possible because the field of vision of each of the eyes overlap at the center. The slight differences in the angle of each eye and what it sees individually create a sense of depth perception and distance. Depth perception and distance become apparent when the image converges on the sweet spot at the center. This is where the field of vision overlaps. So simply, two eyes are better than one.
The same principle is followed in making binoculars. The earliest form is this invention is, of course, the monocular telescope in the 17th century by the Italian physicist and astronomer, Galileo. Mounting two together showed potential and this potential was, and to this day, explored in optics and astronomy.
Early binoculars followed the principles of Galilean optics. This is where a convex objective or lens and a concave lens called the eyepiece. Compared to modern binoculars, early binoculars only provided a narrow field of vision and little magnification. They were most often used in opera houses and theatres.
Improved versions of binoculars are the ones that use prisms. These binoculars employ the principles of Keplerian optics where images formed by the objective lens are viewed through a positive eyepiece lens though this configuration lead to inverted images. There are many different ways in correcting this. Examples of these prisms are the Porro and Roof prisms.
Binoculars that make use of Porro-prisms create a great sense of depth in the images seen. It uses a Z-shaped configuration that erects images. Roof-prism binoculars use objective pieces in line with the eyepiece. The advantage of the latter is that they provide a narrower and more compact device that of the ones which use Porro-prisms. Another difference here is the brightness. Porro-prisms produce a brighter view because it employs silvered surfaces that reduce light transmission.
Porro prism binoculars occasionally need their prism sets to be re-aligned to bring them into collimation. Collimation is the alignment of the optical elements in getting the best view. The fixed alignment in roof-prism designs means the binoculars normally won’t need re-collimation. So, the choice between Porro- or Roof-prism is dependent on the preferences of the user.
