noun
: a lens system in which either the entrance pupil or the exit pupil is at infinity and which is used in optical measuring devices to eliminate parallax between an image and the scale for its measurement
noun
: a lens system in which either the entrance pupil or the exit pupil is at infinity and which is used in optical measuring devices to eliminate parallax between an image and the scale for its measurement
Webster's New International English Dictionary. Новый международный словарь английского языка Webster. 2012