(ˈ)hīˈgēnēən-, (ˈ)hȯi- noun
also huy·gens eyepiece ˈhīgənz-, ˈhȯi- ; or huy·ghe·ni·an eyepiece
Usage: usually capitalized H
Etymology: huyghenian irregular from Christian Huygens (or Huyghens ) died 1695 Du. physicist + English -ian
: a compound eyepiece used especially with achromatic objectives that consists of two plano-convex lenses separated by a diaphragm with the convex sides facing the objective