Circulation of light in your binoculars
The second optical principal interesting to tackle is the circulation of light in a pair of binoculars.
On the X-ray image of this pair of binoculars, you can see the objective lens at the bottom. Light passes through the objective lens, then the focus lens (which makes the image sharply defined), then the prism, and then the eyepiece lenses. What you must remember is that light is transmitted in a straight line. As such, there are obstacles in a pair of binoculars. For example, the optical components. So, on contact with an obstacle, the light can be absorbed, dispersed, reflected, or refracted. The light is going to encounter six, seven or eight optical obstacles and what you should know is that, at each of these interfaces, the light loses around 5% of its transmission rate. As it stands, if no action is taken, 60% of the light which enters the objective lens would leave the eyepiece. You would then have very little contrast, and it would appear quite dull and rather dark when you looked through the binoculars. The main aim in designing a pair of binoculars is therefore to improve the definition and quality of the image.