Specularly reflected light from a convergence position on an object surface 31 enters a second critical-angle prism 14, another prism 15, and a first critical-angle prism 13 of a parallel beam selection optical system 20 in this order as a parallel beam traveling along the optical axis. The critical-angle...http://www.google.co.uk/patents/US7301697?utm_source=gb-gplus-sharePatent US7301697 - Microscope device
