| 摘要 |
<p>Apparatus for producing and guiding a light beam, in particular for a laser interferometer, includes a laser having a laser tube (100) and an external cavity (112). Two laser beams (110A' and 110B') of orthogonal polarisation states are directed from the cavity into polarisation maintaining fibres (12, 14). The two beams are generated from a single beam (110) by a birefringent prism (120) in the cavity. Additional beam steering prisms (130A and 130B) are included to direct the beams from the birefringent prism to the fibres. The additional steering prisms compensate for temperature induced beam deviations in the birefringent prisms. Interferometric sensing heads (20, 22) receive the beams from the fibres and include a rotatable wedge prism and mechanical adjustment means for guiding the beams onto reflecting surfaces on an object for positioning the object. The ends of the fibres attached to the sensing heads are kinematically located in the head.</p> |
