Huygens' eyepiece
/ (ˈhaɪɡənz) /
noun
physics
a telescope eyepiece consisting of two planoconvex lenses separated by a distance equal to half the sum of their focal lengths, which are in the ratio of three to one, and oriented so that their curved surfaces face the incident light
Word Origin for Huygens' eyepiece
C19: named after Christiaan
Huygens (1629–95), Dutch physicist