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 beam deflector has first and second wedge prisms having refractive indices and geometries which are similar (in the case of the geometry to within arc minutes). The prisms are rotatable about an optical axis O defined by the direction of propagation of the incident light beam, to adjust the angle through which the incident beam is deflected. A third prism has a wedge angle which is greater than that of the first and second prisms by a factor of 2. When the directions in which the first and second prisms refract the beam away from the optical axis are aligned about the optical axis at notional angles of 0° and 90° respectively, and the third prism is aligned with its direction of refractive deviation at a notional angle of 225° about the optical axis, the light beam will pass undeviated through the deflecting device.

Abstract: The component parts of an optical measuring system include two housings (20,22) each of which contains optical elements of the system, and a base (10). The two housings are each provided on at least one face with the complementary parts of a kinematic support (18), and the optical components are arranged within the respective housings so that when the kinematic support is engaged the optical components are properly aligned. The base is provided with a kinematic support (16) on its surface which is arranged so that when the base is aligned with a machine axis, any housing placed on the kinematic support will automatically be aligned with the machine axis. Thus by aligning the base with a machine axis, the optical components of the system will automatically be aligned when the housings are connected to the base and to each other using the kinematic supports.

Abstract: A mounting device for a telescopic ball-bar has a hexagonal shank retained in jaws of a chuck on a spindle of a lathe. A supporting bracket extending from the shank carries a magnetic socket in one of a plurality of locations, and receivably mounts one end of the ball-bar for universal pivotal motion. The configuration of the bracket, the spacing between the socket and the shank, and the orientation of the socket, are such that the other end of the ball-bar, which is universally pivotally mounted to the tool post of the lathe, may execute a circular trajectory of greater than 180.degree., which trajectory intersects the axis of rotation of the lathe.

Abstract: A laser interferometer, used for measuring displacement over long distances (e.g. 100 meters) includes an integral laser/detector unit 10, which emits a beam 12 of laser light. The fraction of the beam 12B which passes undiverted through a beam splitter 14 is laterally displaced by a periscope 18, which is positioned close to the laser 10. After passage through the periscope 18, the undiverted beam is incident upon a large retroreflector 20, whose size is such that the beam reflected by retroreflector 20 is laterally displaced by an amount greater than the lateral displacement due to passage of the beam through the periscope 18. Opaque housing 26 of the periscope 18 is used to screen reflected light from entrance into the laser cavity.

Abstract: A ball-bar 26 for calibrating machine tools and coordinate measuring machines comprise a unit 30 containing a displacement transducer 34 for measuring axial displacement of a precision ball 28. The ball 28 is pivotably located on the head or spindle 12 of the machine, which is driven in a circle about a ball 22 mounted on the bed or table 10 of the machine at the other end of the ball-bar in order to perform a calibration. The ball-bar has a modular construction, its various components such as the unit 30, extension bar 40, magnetic sockets 24,29, supporting device 14 and magnetic clamp 16 being connected together via M6 screw-threads, e.g. at 18,42,44. This enables the unit 30 to be connected to the various other components in a variety of configurations, e.g. for use as an electronic dial gauge.

Abstract: A method of and apparatus for dynamically calibrating a machine are disclosed in which a laser interferometer is provided in addition to the machine scales for taking independent measurements of a movement of a machine part while the part is in motion. As the moving machine part reaches pre-determined distances along its movement (e.g. every inch) the readings of the interferometer and the machine scales relating to the movement of the machine part are recorded and compared. Any difference is recorded for use in mapping the machine errors. In the preferred form of the invention a reflector is mounted on the machine spindle adjacent to, or in place of, a tool or measuring probe, and its movements are measured by the interferometer. The interferometer is arranged to generate a signal as each predetermined distance is reached and an infra-red signal is transmitted from the interferometer to a receiver on the machine spindle which is wired into the probe or tool detection circuits.