Optical device having a rotatable birefringent crystal

摘要

An optical device has a rotatable birefringent crystal. The crystal is rotatable around a first axis ( 4; 42 ) and has a crystallographic-optical axis ( 6; 44 ) in a plane that is perpendicular to the first axis. In addition, the crystal is rotated around the first axis in order to control a displacement (Deltax) of a light beam in the plane when the light beam is polarized within the plane and directed onto the crystal.