Two corner cubes are opposed to share one or two mirror surfaces in common thereby integrally forming two mirror groups, and driven to be reciprocatively rotated in a plane including two opposite edges thereof or a symmetry plane including an edge defined by the two common mirror surfaces, while a beam...http://www.google.fr/patents/US5243404?utm_source=gb-gplus-shareBrevet US5243404 - Fourier transform spectrophotometer
