Binoculars are a pair of mirror-symmetrical telescopes attached by a centralized brace and an adjusting wheel. These binoculars are aligned to point in the same direction but provide the viewer with two slightly different perspectives of the same object for the purpose of producing, or reflecting, a greater sense of depth, dimension, and distance than single-lens view-pieces, known as monoculars. The most common binoculars are hand-held, but others, especially those larger, are mounted on stationary stands or tripods with rotation slides for panoramic viewing. Binoculars function on the basic rinciples of reflection, distance, and light refraction. All binoculars show an erect image created through either Galilean Optics or optical prisms. In the case of the latter, the optical path between eyes and
object is virtually “folded” by filtering elements called prisms inside the binoculars so that the actual physical distance between seer and that which is seen is less than the focal length of the lenses in the binoculars. This “folding” of the optical path increases the separation between the two lenses and ultimately creating a greater sense of depth. This actively involves reflection, distance, and light refraction.

Prismatic binoculars use a sequence of reflecting and filtering elements fitted within each monocular, initiating a Z-shaped optical path. In this way, the optical path is “folded” These little elements, known as porro prisms, are situated in such a way that they filter light and channel it through to optimize visual sharpness and clarity. Since binoculars have two of these chasms closely linked, the optical path is not only “folded,” but doubled, created a more three-dimensional view of  the object.

** Think: holding a magnifying glass in front of another magnifying glass and looking through both. The image is pulled up close because the visual distance between you and what you’re seeing has been cut. Make sense?

Since some objects that are viewed are not at a fixed distance, and even more due to the fact that each viewer’s eyes are different than any other’s, binoculars must have focusing adjustments. With binoculars, each monocular is focused independently of the other, so both have to be adjusted to work with the other to amplify the object desired in accordance with the viewer’s vision. Since it is more convenient to focus both monoculars at the same time, a central wheel on the binoculars provides synchronized adjustments. Each monocular, though, has its own adjustment wheel to accommodate the viewer’s eyes. Once this adjustment is made, the central wheel on the bincoculars will be the only necessary mechanism for further focus.

** Think: If you’re driving at nighttime and one of your headlights is burnt out, your vision is limited. One portion of the space in front of you is illuminated, the other dark. You therefore can’t see the full picture.

Collimation is necessary for optimum focus in any set of binoculars; both monoculars must be aligned just right for binoculars to work properly. This is the main technical principle behind the concept of binocular vision. When collimation is successful, each of the monocular’s “folded” optical paths are merged, and a three-dimensional image is constructed. This is the simple process of binocular function.