(n.) The lens, or combination of lenses, at the eye end of a telescope or other optical instrument, through which the image formed by the mirror or object glass is viewed.

Iconoscope Kodak Photostat SLR X-ray machine achromatic lens aerial reconnaissance camera astigmatic lens astrograph box camera burning glass camera obscura candid camera cinematograph coated lens color camera concave lens concavo-convex lens condenser convex lens eyeglass eyepiece glass hand lens kinematograph lens magnifier magnifying glass meniscus miniature camera minicam motion-picture camera movie camera object glass objective objective prism ocular photochronograph photocopier photomicroscope photopitometer portrait camera precision camera press camera prism reader reading glass reflex camera spectroscopic camera stereo camera still camera telephoto lens television camera toric lens tripod camera twin-lens reflex varifocal lens vest-pocket camera zoom lens