quantity that determines the maximum geometric throughput of radiation transmitted, received or emitted in a single-pass, passive optical arrangement
Note 1 to entry: Defining a ray as the confined radiation exchange between two subtended surface area elements d
Note 2 to entry: "Single-pass" means that the term applies only for radiation transfer in a single defined direction. It does not apply to devices such as Fabry–Pérot cavities.
Note 3 to entry: See also "optical extent".
Note 4 to entry: The geometric extent is expressed in square metre times steradian (m2·sr).
Note 5 to entry: This entry was numbered 845-01-33 in IEC 60050-845:1987.
Note 6 to entry: This entry was numbered 17-489 in CIE S 017:2011.