Source : Webster's Revised Unabridged Dictionary (1913)

Lieberkuhn \Lie"ber*k["u]hn\ (l[=e]"b[~e]r*k[usd]n), n. [Named
   after a German physician and instrument maker, J. N.
   Lieberk["u]hn.] (Optics)
   A concave metallic mirror attached to the object-glass end of
   a microscope, to throw down light on opaque objects; a
   reflector.