Binoviewer

A binoviewer is an optical device designed to enable binocular viewing through a single objective.

In contrast to binoculars, it does not allow stereoscopic viewing, as both images are produced by the same objective and do not differ except for aberrations induced by the binoviewer itself. However, binocular viewing allows the brain's visual system to make use of binocular summation, resulting in a more relaxed viewing experience and an increased ability of detecting faint details.