Optical Cross Section or OCS is a value which describes the maximum amount of optical flux reflected back to the source. The standard unit of measurement is
Contents
Flat mirror
Optical cross section of a flat mirror with a given reflectivity at a particular wavelength
Where
In order to maximize the return a corner reflector is used. The alignment of a corner reflector with respect to the source is not as critical as the alignment of a flat mirror.
Other optical devices
Optical cross section is not limited to reflective surfaces. Optical devices such as telescopes and cameras will return some of the optical flux back to the source, since it has optics that reflect some light. The Optical cross section of a camera can vary over time due to the camera shutter opening and closing.