Objective lens, focusing lens, image-erecting system and eyepiece – the key elements found in all binoculars for birding and nature observation. Each component has its own special job: The objective lens generates an image of the observed object at the intermediate image plane. This image is upside down and reversed left-to-right, so the prism system is positioned in front of the intermediate image plane and this corrects the image for both top to bottom, and left to right orientations. The result is an upright, unreversed image. Prisms are used in both binoculars and spotting scopes for this purpose. The eyepiece acts as a magnifier and helps the eye to examine the image.
Representation of the optical path in the binocular body.
Theoretically, one converging lens each for the objective lens and eyepiece is enough, but the result would be a crude and unsatisfactory instrument. Therefore, sophisticated systems have been developed which contain, for example, up to 12 lens elements or more for binoculars (Victory SF 8x32) on each side, or up to 17 lens elements for spotting scopes with zoom objectives (Harpia 95 with 23-70x eyepiece). Different glass materials with varying properties are also combined (including the very high- quality optical fluoride glass for ZEISS FL lenses) to achieve brilliant, outstanding results. The many coatings applied to all glass surfaces in a high vacuum and, of course, extremely stringent tolerances in the manufacture of each part, and during assembly, play key roles as well.
Representation of the optical path in the binocular body.
Theoretically, one converging lens each for the objective lens and eyepiece is enough, but the result would be a crude and unsatisfactory instrument. Therefore, sophisticated systems have been developed which contain, for example, up to 12 lens elements or more for binoculars (Victory SF 8x32) on each side, or up to 17 lens elements for spotting scopes with zoom objectives (Harpia 95 with 23-70x eyepiece). Different glass materials with varying properties are also combined (including the very high- quality optical fluoride glass for ZEISS FL lenses) to achieve brilliant, outstanding results. The many coatings applied to all glass surfaces in a high vacuum and, of course, extremely stringent tolerances in the manufacture of each part, and during assembly, play key roles as well.
