About: http://webisa.webdatacommons.org/81663939

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	An apparatus for detecting a focusing state of an optical system according to claim 1, wherein said defining means is a light shielding plate having a rectangular light transmitting hole.
http://www.w3.org/ns/prov#wasQuotedFrom	google.com