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 Raman spectroscopy system has a filter arrangement comprising two filters (16, 26A) in series, to reject light of the illuminating wavenumber from the scattered light of interest. The filters are tilted and have different characteristics for light of first and second different polarisation states. To counter this, the filters are arranged so that their respective effects on the respective polarisation states at least partially cancel each other out. This may for example be done by arranging their tilt axes (32, 34) orthogonally to each other.

Abstract: A method of calibrating a measurement probe (10) mounted on a machine is described. The measurement probe (10) has a stylus (14) with a workpiece contacting tip (16). The method comprises determining a probe calibration matrix that relates the probe outputs (a,b,c) to the machine coordinate system (x,y,z.). The method comprising the steps of scanning a calibration artefact (18) using a first probe deflection (d1) to obtain first machine data and using a second probe deflection (d2) to obtain second machine data. The first and second machine data are used to obtain a pure probe calibration matrix in which any machine errors are substantially omitted. Advantageously, the method determines the pure probe matrix numerically based on the assumption that the difference between the first and second machine position data is known.

Abstract: A sample positioning stage for positioning a sample to be inspected relative to an optical inspection device, including a first generally planar body on which a sample can be carried and a second body directly coupled to the first body via at least one rigid bearing and at least one resiliently compliant bearing provided between the first and second bodies. The first and second bodies are preloaded against each other in a dimension substantially parallel to the plane of the first generally planar body via the bearings. The stage also includes a motorized drive system operable to drive the first and second bodies relative to each other in the first plane toward a demanded relative position received from a position input device, and a position sensing device on at least one of the first and second bodies, for providing a measure of the relative position of the first and second bodies.

Abstract: In a Raman spectroscopy apparatus, exciting light is focussed on a sample (26) as a line focus 38. Spectra from points in the line focus are dispersed in rows 46 on a CCD detector 34, having a two-dimensional array of pixels. The line focus moves longitudinally in a direction Y (arrow 48) relative to the sample. Simultaneously and synchronously, charge is shifted in a parallel direction Y? (arrow 50) within the CCD, so that data from a given point in the sample continues to accumulate. This ensures that the data from each sample point arises from illumination which is integrated along the line focus, and makes it easier to stitch the data together subsequently to form an image of the sample. In order to provide averaging in the X direction during fast, low resolution scanning, the line focus is swept across the sample in a zig-zag fashion, between boundary lines 60.

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 fabricating a bearing surface (11,13) for a gas or air bearing (2) is described. The method comprises taking a bulk bearing portion (30; 44) having at least one bearing surface region and providing a coating (32; 42) on the bearing surface region to define at least one gas pocket (34; 40). The at least one gas pocket (34; 40) has a depth substantially equal to the thickness of the coating (32; 42). In one example, laser ablation is used to remove part of the coating (32; 42) to form the gas pockets (34; 40). The coating (32; 42) may be an anodised coating and the bulk bearing portion (30) may be formed from aluminium. An air bearing component formed using the method is also described.

Abstract: A pivot joint has a first member having a ball located at one end, a fixed member having one or more bearing surface, which locates on the ball of the first member and a second member having one or more bearing surface located at one end which locates onto the ball of the first member. The first and second members are rotatable about the centre of the ball. This type of pivot joint is suitable for use in a machine such as a Stewart platform.

Abstract: A method of calibrating a scale measurement apparatus. A scale has scale markings arranged to form an incremental pattern and at least one scale mark. A readhead has an incremental detector means which produces an output signal and a scale mark detector means for producing a signal having a zero crossing. The readhead is moved relative to the scale. The output from the incremental detector is used to determine a predetermined phase in the output signal and the value of the signal from the scale mark detector corresponding to the predetermined phase in the output signal from the incremental detector on either side of the zero crossing is determined. These values are used to define the width of the scale mark pulse.

Abstract: An optical element has a member having features which interact with incident light to produce two or more resultant beams. The configuration of the optical element is such that light which interacts with said features when passing through the member from a first side to produce two or more resultant beams does not interact with said features when returned to another side of the member and/or vice versa. The optical element may be used in a readhead of a scale and readhead apparatus.

Abstract: A pivot joint has a first structure comprising a ball mounted in a receptacle, wherein the location of the ball is held with respect to the receptacle, and a second structure mounted on and movable with respect to the ball, wherein the second structure has at least one bearing surface which defines its position with respect to the ball. The ball may be held in location by contact with the receptacle at least two positions. At least one of the positions of contact may be adjustable.

Abstract: Position measurement apparatus, such as hexapod co-ordinate measuring machine, is described that comprises a thrust frame and a metrology frame. The thrust frame comprises a load carrying base connected to a moveable platform by a plurality of powered extendable legs. The metrology frame comprising a metrology base attached to the load carrying base by a base attachment mechanism such as kinematic mounts. The base attachment mechanism is arranged to prevent any distortions of the load carrying base being transmitted to the metrology base.

Abstract: A probe for position determining apparatus has a probe body (18) and a workpiece-contacting stylus (14). A strain sensitive structure connects the probe body and the stylus, and includes bendable members (32). The bendable members have an asymmetric cross-section, e.g. “T” shaped. A strain gauge (33) is mounted to the stem of the “T” to detect the bending caused when the stylus contacts a workpiece. This enables the strain sensitive structure to be both robust and sensitive to the bending.

Abstract: A gas turbine having air cooling is provided with an effective measure for cleaning cooling air which is used in the turbine, which measure is particularly efficient. In order to allow comparatively pure, that is to say particle-free, compressed cooling air to flow into the cooling-channel system of the turbine, it is proposed that a protective element is provided for particle separation in a manner which is adjacent radially further to the outside to the removal opening, which protective element impedes particles which floating the compressor final air from flowing into the removal opening. As a result the clogging of cooling—air holes in impact-cooled turbine components which are loaded by hot gas can be avoided.

Abstract: An apparatus for measuring a surface of a workpiece is described. The apparatus comprises a support, attachable to the moveable arm of a machine, such as a coordinate positioning machine, and rotatable about first and second axes of rotation, the axes driven by first and second motors respectively. The apparatus additionally comprises a surface sensing device for sensing the surface of a workpiece, rotatable about a third axis of rotation. This third axis of rotation is alignable with the first axis of rotation, and when aligned, rotation of the support relative to the surface sensing device is actuatable by the first motor. A method for using an apparatus for measuring a surface of a workpiece is also described.

Abstract: Measurement apparatus comprising a laser measuring system an acoustic system is described. The apparatus provides a feedback control signal that can be used in the feedback control system of an associated machine. To allow real time, dynamic, operation the laser measurements are compensated using a compensation value derived from a plurality of laser measurements and at least one acoustic time of flight value.

Abstract: A method of calibrating a probe is disclosed said probe being mounted on a machine and having a stylus with a workpiece contacting tip, comprising calculating calibration information for the probe for a first orientation of the probe, and rotating the calibration information by an angle to obtain a probe calibration information for when the probe is oriented by that angle with respect to the first orientation. Also disclosed is a method of calibrating a probe during a measurement process. The calibration information may include a vector which relates probe head axes to machine axes; a calibration matrix; datum data; an inertial matrix. The stylus tip may be datumed at the orientation of the probe or inferred from datum information obtained at different orientations. The rotation step may be carried out by a software/computer program which may be stored on a controller for the machine.

Abstract: A tool shank (18;38;138) is described that comprises a spindle attachment portion (20) that is removably attachable to the rotatable spindle (12) of a machine tool (10), a shank body portion (21;121) which extends beyond the end of the spindle when the tool shank (18;38;138) is attached to the spindle (12) of a machine tool (10) and the first part (26;38;148) of a separable electrical coupling (22;132). The shank body portion comprises a feature (28;128) suitable for engagement with a tool change device (29) and the first part (26;38;148) of the separable electrical coupling (22;132) is located on the shank body portion (21;121) between the feature (28;128) and the spindle attachment portion (20). A machine tool (10), and a kit for retrofitting a machine tool (10), that comprise the second part (24;148) of the separable electrical coupling (22;132) are also described.

Abstract: A ‘go, no-go’ method is described for determining whether the dimensions of an object, such as a workpiece, conform to tolerance. The method uses a measurement probe, such as a touch trigger, analogue, or non-contact probe, mounted on a measuring apparatus such as a coordinate measuring machine, machine tool, or a lathe. The method comprises the step of driving the measurement probe around a path relative to the object, said path being based on a tolerance of the object. The path relative to the object may include at least a first path based on the maximum tolerance of the object and a second path based on the minimum tolerance of the object. The method additionally comprises the steps of monitoring any probe measurement data acquired by the measurement probe as the probe is driven around the path, and indicating if the dimensions of the object do not conform to tolerance only if there is a change in state of the probe measurement data that is acquired as the measurement probe is driven around the path.

Abstract: Scale reading apparatus is described that comprises a readhead (12) that is moveable relative to a scale (10). The readhead (12) comprises an incremental channel from which a series of reference mark pulses (56) are produced as the readhead (12) is moved relative to the scale (10). A reference mark channel is also provided that produce a reference mark gating pulse (58) when the readhead (12) passes a predetermined (absolute) position mark (22) on the scale. Alignment detection means monitor, during use, phase alignment of the reference mark gating pulse (58) and reference mark pulses (56). The alignment detection means is arranged to monitor the phase of the leading and trailing edges (68) of said reference mark gating pulse (58) relative to the phase of the reference mark pulses (56). The apparatus may be used in position encoders and the like.