Abstract: A retaining device comprises a holder for receiving an object and a clamp 4. The holder comprises a cylindrical sleeve 1 with three longitudinal cut-out slits 3 spaced 120° apart and a base 2 secured at one end. The inner surface of the clamp 4 has three lobes 11,12,13 also spaced 120° apart. The portions midway adjacent lobes contact the portions of the sleeve midway adjacent slits 3, resulting in a symmetrical force being applied to the circumference of the sleeve 1 when the clamp 4 is tightened. The clamp 4 is free from the base 2 of the holder and is not rigidly attached to the sleeve 1 and thus does not apply unequal forces to the holder when the clamp is tightened. Alternatively the sleeve 1 may have a thin continuous wall which deforms when forces are applied to it by the clamp 4. The object inserted into the sleeve may have a spherically shaped portion to allow is to be angularly adjusted in the sleeve before the clamp is tightened.

Abstract: 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 polarization states are directed from the cavity into polarization maintaining fibers (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 fibers. The additional steering prisms compensate for temperature induced beam deviations in the birefringent prisms. Interferometric sensing heads (20, 22) receive the beams from the fibers 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 fibers attached to the sensing heads are kinematically located in the head.

Abstract: A retaining device comprises a holder for receiving an object and a clamp 4. The holder comprises a cylindrical sleeve 1 with three longitudinal cut-out slits 3 spaced 120° apart and a base 2 secured at one end. The inner surface of the clamp 4 has three lobes 11,12,13 also spaced 120° apart. The portions midway adjacent lobes contact the portions of the sleeve midway adjacent slits 3, resulting in a symmetrical force being applied to the circumference of the sleeve 1 when the clamp 4 is tightened. The clamp 4 is free from the base 2 of the holder and is not rigidly attached to the sleeve 1 and thus does not apply unequal forces to the holder when the clamp is tightened. Alternatively the sleeve 1 may have a thin continuous wall which deforms when forces are applied to it by the clamp 4. The object inserted into the sleeve may have a spherically shaped portion to allow is to be angularly adjusted in the sleeve before the clamp is tightened.