Abstract: A read head for a scale reading apparatus, the head including a light source and an array of photodetector elements, wherein said light source and array of photodetector elements are fabricated in a lattice matched semiconductor compound.

Abstract: A method of calibrating an articulating probe head comprising the steps of measuring an artefact of known dimensions with the workpiece sensing probe mounted on the articulating probe head, in which the articulating probe head is unlocked. An error functional map is generated corresponding to the difference between the measured and known dimensions of the artefact. Subsequent workpieces are measured with the articulating probe head unlocked and the corresponding correction applied. The true dimensions of the artefact may be determined by measuring it with a probe mounted on an articulating probe head in which the axes of the articulating probe head are locked. A mechanical lock is provided to lock the axes of the articulating probe head.

Abstract: Apparatus and method of determining drift for a surface measurement probe. The surface measurement probe has a housing, a surface contacting stylus, a vibration generator which causes vibration of the stylus, a sensing device for determining a parameter related to change in vibration of the stylus, and a comparator for determining the relationship of the parameter with a threshold. Readings of the parameter are taken when the stylus is not in contact with a surface and average over a time t, which is significantly larger than the transition time when touching a surface. The average of the readings of the parameter is compared to a reference parameter. The comparison is used to determine whether there has been significant drift of the parameters. Thus drift due to temperature change is corrected.

Abstract: A method for measuring a surface profile using a surface sensing device mounted on an articulating probe head in which the probe head is moved along a nominal path relative to the surface profile, an at least approximation of the surface normal of the surface profile, the surface profile is sensed with the surface sensing device and the distance or force of the surface sensing device relative to the surface profile substantially in the direction of the surface normal. The surface normal may be determined by approximating at least one section to a curved profile which can be mathematically parameterised.

Abstract: A method of calibrating an articulating probe head comprising the steps of measuring an artefact of known dimensions with the workpiece sensing probe mounted on the articulating probe head, in which the articulating probe head is unlocked. An error functional map is generated corresponding to the difference between the measured and known dimensions of the artefact. Subsequent workpieces are measured with the articulating probe head unlocked and the corresponding correction applied. The true dimensions of the artefact may be determined by measuring it with a probe mounted on an articulating probe head in which the axes of the articulating probe head are locked. A mechanical lock is provided to lock the axes of the articulating probe head.

Abstract: Contact sensing probe apparatus includes a workpiece contacting stylus, a transducer mechanically coupled to the stylus and an oscillator for supplying an alternating current to the transducer to induce vibration of the stylus. A contact sensor is also provided for monitoring the phase difference between the voltage supplied to the transducer and the current flow to the transducer. The oscillator is arranged to supply the transducer with an alternating current of a first frequency during contact sensing. This first frequency is selected to induce mechanical resonance but to be away from the maximum of the mechanical resonance peak. The probe may be used with co-ordinate positioning machines, such as portable articulated measuring arms, co-ordinate measuring machines (CMM) and the like.

Abstract: A contact sensing probe having a stylus which is vibrated longitudinally by a piezoelectric transducer. Contact with a workpiece is detected from damping of the vibration. The stylus is mounted to a probe body via parallel diaphragm springs. These cooperate with a counter mass to form a mechanical low pass filter, which isolates the stylus vibrations from influences caused by the mounting or handling of the probe body.

Abstract: A measurement system has a surface sensing device mounted on an articulating probe head, which in turn is mounted on a coordinate positioning apparatus. The surface sensing device is moved relative to a surface by driving at least one of the coordinate positioning apparatus and probe head in at least one axis to scan the surface. The surface sensing device measures its distance from the surface and the probe head is driven to rotate the surface sensing device about at least one axis in order to control the relative position of the surface sensing device from the surface to within a predetermined range in real time.

Abstract: Apparatus for a co-ordinate positioning machine is described that comprises an articulating probe head for supporting a measurement probe. The articulating probe head comprises at least one electric motor. Heating means are provided for generating heat in the articulating probe head. The heating means may be the motors or discrete heating elements. Temperature sensing means, such as one or more temperature sensors, is also provided for determining the temperature at the articulating probe head. The apparatus allows the temperature of the articulating probe head to be controlled.

Abstract: A rotary drive mechanism is disclosed comprising a housing (10), a first motor (12) having a first rotor (38) and a first stator (32) connected to the housing and a second motor (50) having a second rotor (52) and a second stator (54) connected to the housing characterised in that the second motor is mechanically independent of the first motor whereby acceleration torques of the first motor are at least partially inertia balanced by the second motor. The balancing may be effected by equal and opposite rotation of the second motor. Control means may be provided to provide the second motor with a current which is proportional to that supplied to the first motor. Also disclosed is a positioning device and a probe having the rotary drive mechanism.