roof prism
noun
1- a reflecting prism in which the reflecting surface is in two parts that are angled like the two sides of a pitched roof脊角棱镜。比较PORRO PRISM.
1.1
roof prisms
（亦作roof-prism binoculars）a pair of binoculars using two such prisms, resulting in an instrument with parallel sides and objective lenses that are the same distance apart as the eyepieces脊角棱镜双目镜。