Night vision devices with beveled eyecups

Beveled eyecups

— the angled eyecups ensure that the eyepiece(s) fit as tightly as possible to the eye, providing a high degree of isolation from extraneous light sources that can impair image visibility and distract the operator. On the other hand, such equipment is unsuitable for use with glasses (although in some models this disadvantage is compensated by the ability to turn up the eyecups).