ocular (ok'u-lar)

Of or belonging to the eye; conducted by means of the sense of sight (said of an examination); as a n., an eyepiece; the part of a compound optical apparatus, such as a telescope or microscope, into which the observer looks, achromatic o. An o. in which the chromatic aberration is wholly or nearly eliminated, aplanatic o. An o. corrected for spherical aberration, with the chromatic aberration usually eliminated, binocular stereoscopic o. An o. composed of two o's about as far apart as the two eyes and connected with a single tube which is put in place of the o. of a uni ocular microscope, compensating o. An o. especially constructed for use with apochromatic objectives and serving to correct or compensate for aberrations in the objectives outside the axis, erecting o. An o. with which an erecting prism is connected. so that the image in the compound microscope appears erect as with a simple microscope; it is mostly used for di ecting microscopes, goniometer o. An o. with a goniometer for measuring the angles of microscopic crystals. Huygens's o. See under Huygens. micrometer o., micrometric o. An o. with which is connected a micrometer for the purpose of measuring the real image of objects, microscopic o., microscopical o. An o. consisting of one or more converging lenses or lens systems the combined action of which is like that of a simple microscope, magnifying the real image formed by the objective.