Magnification principle

Structure and Optical Technologies

Binoculars feature a combination of objective lens and eyepiece lens that magnifies distant objects and makes them appear nearer. Keplerian binoculars in general use have convex lenses for objectives as well as eyepieces. In principle, a real image A formed by an objective lens is magnified by an eyepiece lens and viewed as a virtual image B. As a result, the magnified objects can be observed as if they were just in front of your eyes.
In this case, the image is inverted, so prisms are incorporated to rectify it so that an erect image can be viewed.