About: http://webisa.webdatacommons.org/95833991

Property	Value
http://www.w3.org/1999/02/22-rdf-syntax-ns#type	http://www.w3.org/ns/prov#Entity
http://www.w3.org/ns/prov#value	A system as claimed in claim 1 wherein said optical element is a plate of a transparent material having two surfaces which are inclined relative to the principal axis of the beam and wherein one of said two surfaces is partly reflecting.
http://www.w3.org/ns/prov#wasQuotedFrom	google.com