Binoculars(redirected from Binocular instrument)
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A set of two identical telescopes, one for each eye, which gives binocular vision of magnified distant objects. The images are erected using either an eyepiece of negative power, or prisms, or very occasionally, an additional lens system placed between objective and eyepiece. On binoculars, the magnification M and the diameter D of the objective or entrance pupil are shown as M ✕ D (e.g. 8 ✕ 30). Syn. field glasses; prism binoculars (for those which use prisms as erectors). See erector; galilean telescope; terrestrial telescope.
Millodot: Dictionary of Optometry and Visual Science, 7th edition. © 2009 Butterworth-Heinemann