US Patent RE39934 Adjustable optical attenuator

An optical attenuator for attenuating a collimated beam of light propagating along an optical path while preserving the composition of polarization of the collimated beam of light is disclosed. The optical attenuator comprises a beam attenuator for attenuating a portion of the collimated beam of light when a portion of the beam attenuator is disposed within the optical path. The beam attenuator has a cross section along a plane perpendicular to the direction of propagation of the collimated beam of light of the portion of the attenuator in the shape of a wedge. The attenuation is varied using a controller for moving the beam attenuator in order to vary a size of the portion of the wedge within the optical path.