Abstract: Scale reading apparatus having a scale and readhead moveable relative to one another The scale has a first incremental scale pattern with a fine pitch and a second incremental scale pattern with a coarse pitch. The readhead has a detector to detect each of the incremental scale patterns. The scale reading apparatus can be used for both slow speed and fast speed measurements. The second incremental scale pattern may be provided in a scale track which has a dual function (e.g. limit track or reference mark) and the readhead may be configured to decode the signal to produce an output suitable for the desired function.

Abstract: A touch probe (10,50) is disclosed comprising a probe body (12,52) housing first locating elements (23,58), a stylus holder (16,54) having second locating elements (24,57) which co-operate with the first locating elements to locate the stylus holder within the probe body, and a bias (36,68,86) to urge the first and second locating elements into contact, wherein an element (35,50,76,90) is provided to damp motion between the probe body and the stylus holder. The element may slow a relative movement between the locating elements perhaps by resisting the urging of the bias or absorb energy produced by a relative movement between the probe body and stylus holder. The element may be slidably or rotatably mounted with respect to one of the probe head and stylus holder.

Abstract: A touch-trigger probe is provided with a sensor (which may be a mirror (106), an optical fibre (206), or a bi-refringent element (307)) which changes state by vibrating or undergoing strain when a stylus connected to the probe contacts a workpiece. The sensor is typically provided on (in the case of the mirror (106)), or in (in the case of the optical fibre (206)) the stylus. The change of state of the sensor causes a change in the path length, polarization state, or intensity of light waves conveyed by the sensor. An interferometer may be provided to detect such changes. Other forms of electromagnetic waves may be used to the same effect.

Abstract: A succession of nominally identical workpieces is measured using a probe on a coordinate measuring machine. To enable most of the workpieces to be probed at a fast speed (step 40), and compensate for the errors thereby introduced, one workpiece is also probed at a slow speed (step 32). For that workpiece, a series of error values is calculated (step 36) from the differences between the fast and slow measurements. The subsequent fast measurements on succeeding workpieces are corrected by making use of these error values (step 42).