A lens system consisting of two or more lenses on the same axis.

Roget 445: optical instruments; lens, meniscus, magnifier, sunglass, magnifying glass, hand lens; microscope, megascope^†, tienoscope^†.    spectacles, specs [Coll.], glasses, barnacles, goggles, eyeglass, pince-nez, monocle, reading glasses, bifocals; contact lenses, soft lenses, hard lenses; sunglasses, shades [Coll.].    periscopic lens^†; telescope, glass, lorgnette; spyglass, opera glass, binocular, binoculars, field glass; burning glass, convex lens, concave lens, convexo-concave lens^†, coated lens, multiple lens, compound lens, lens system, telephoto lens, wide-angle lens, fish-eye lens, zoom lens; optical bench.    astronomical telescope, reflecting telescope, reflector, refracting telescope, refractor, Newtonian telescope, folded-path telescope, finder telescope, chromatoscope; X-ray telescope; radiotelescope, phased-array telescope, Very Large Array radiotelescope; ultraviolet telescope; infrared telescope; star spectroscope; space telescope.    [telescope mounts] altazimuth mount, equatorial mount.    refractometer, circular dichroism spectrometer.    interferometer.    phase-contrast microscope, fluorescence microscope, dissecting microscope; electron microscope, transmission electron microscope; scanning electron microscope, SEM; scanning tunneling electron microscope.    [microscope components] objective lens, eyepiece, barrel, platform, focusing knob; slide, slide glass, cover glass, counting chamber; illuminator, light source, polarizer, [component parts of telescopes] reticle, cross-hairs.    light pipe, fiber optics mirror, reflector, speculum; looking-glass, pier-glass, cheval-glass, rear-view mirror, hand mirror, one-way mirror, magnifying mirror.    [room with distorting mirrors] fun house.    prism, diffraction grating; beam splitter, half-wave plate, quarter-wave plate.    camera lucida [Lat.], camera obscura [Lat.]; magic lantern etc. (show) 448; stereopticon; chromatrope^†, thaumatrope^†; stereoscope, pseudoscope^†, polyscope^†, kaleidoscope.    photometer, eriometer^†, actinometer^†, lucimeter^†, radiometer; ligth detector, photodiode, photomultiplier, photodiode array, photocell.    X-ray diffractometer, goniometer.    spectrometer, monochrometer, UV spectrometer, visible spectrometer, Infrared spectrometer, Fourier transform infrared spectrometer, recording spectrometer; densitometer, scanning densitometer, two-dimensional densitometer.    abdominoscope^†, gastroscope [Med.], helioscope^†, polariscope^†, polemoscope^†, spectroscope.    abdominoscopy^†; gastroscopy [Med.]; microscopy, microscopist.    ... show more