spherometer

from WordNet (r) 3.0 (2006)

spherometer
    n 1: a measuring instrument for measuring the curvature of a
         surface

from The Collaborative International Dictionary of English v.0.48

Spherometer \Sphe*rom"e*ter\, n. [Sphere + -meter: cf. F.
   sph['e]rom[`e]tre.] (Physics)
   An instrument for measuring the curvature of spherical
   surface, as of lenses for telescope, etc.
   [1913 Webster]