Porro prism
/ˈpɒrəʊ/(亦作Porro prism)
noun
1- a reflecting prism in which the light is reflected on two 45° surfaces and returned parallel to the incoming beam波罗棱镜。比较ROOF PRISM.
1.1
porro prisms
（亦作porro-prism binoculars）a pair of binoculars using two such prisms at right angles, resulting in a conventional instrument with objective lenses that are further apart than the eyepieces波罗棱镜双筒望远镜。