Lenses

1 definition found

From The Collaborative International Dictionary of English v.0.48 [gcide]:

  Lens \Lens\ (l[e^]nz), n.; pl. {Lenses} (-[e^]z). [L. lens a
     lentil. So named from the resemblance in shape of a double
     convex lens to the seed of a lentil. Cf. {Lentil}.] (Opt.)
     A piece of glass, or other transparent substance, ground with
     two opposite regular surfaces, either both curved, or one
     curved and the other plane, and commonly used, either singly


     or combined, in optical instruments, for changing the
     direction of rays of light, and thus magnifying objects, or
     otherwise modifying vision. In practice, the curved surfaces
     are usually spherical, though rarely cylindrical, or of some
     other figure.
     [1913 Webster] Lenses
     [1913 Webster]
  
     Note: Of spherical lenses, there are six varieties, as shown
           in section in the figures herewith given: viz., a
           plano-concave; b double-concave; c plano-convex; d
           double-convex; e converging concavo-convex, or
           converging meniscus; f diverging concavo-convex, or
           diverging meniscus.
           [1913 Webster]
  
     {Crossed lens} (Opt.), a double-convex lens with one radius
        equal to six times the other.
  
     {Crystalline lens}. (Anat.) See {Eye}.
  
     {Fresnel lens} (Opt.), a compound lens formed by placing
        around a central convex lens rings of glass so curved as
        to have the same focus; used, especially in lighthouses,
        for concentrating light in a particular direction; -- so
        called from the inventor.
  
     {Multiplying lens} or {Multiplying glass} (Opt.), a lens one
        side of which is plane and the other convex, but made up
        of a number of plane faces inclined to one another, each
        of which presents a separate image of the object viewed
        through it, so that the object is, as it were, multiplied.
        
  
     {Polyzonal lens}. See {Polyzonal}.
        [1913 Webster]