Abstract: A probe (10) for a machine tool has a switch (32) or other sensor for connecting its battery power supply in response to movement of the probe. In a preferred embodiment, the switch responds to rotation of the probe in the machine tool spindle. The switch (32) is responsive to linear accelerations, but is mounted in the probe so as to respond also to the rotation. A circuit is provid to discriminate between the rotation and linear movements.

Abstract: A laser interferometer is disclosed comprising a housing capable of being substantially repeatably mounted to a wall of an environmental chamber, the housing including a laser source, a reflector attached to an object located within the environmental chamber, and a light passage provided through the wall of the environmental chamber enabling passage of a laser beam from the laser source to the reflector. At least one beam steerer may be provided for adjusting direction of passage of a laser beam through the light passage. Also disclosed is a column laser interferometer.

Abstract: A laser system and interferometer are disclosed comprising a laser source for generating a laser beam, and first and second adjustable elements wherein the first and second adjustable elements have limited rotational motion so rotation of the first adjustable element causes deviation of a laser beam in one plane and rotation of the second adjustable element causes deviation in a second plane, and a laser beam from the laser source is oblique to a required beam direction whereby rotation of the adjustable elements deviates the laser beam enabling alignment of the laser beam to the required beam direction. The adjustable elements may be rotatable through 90°. The first and second planes may be perpendicular to the required beam direction and to each other. At least one mirror may be provided which can be angularly offset to the required beam direction.

Abstract: The invention relates to a reference mark detector for use with a metrological scale or encoder (10) having a patterned reference mark rm movable relative to the reference mark detector. The detector may comprise a photodetector array (20) for detecting the patterned reference mark, the array comprising at least two sets of detector elements A and B each set being formed as a pattern which relates to the pattern of the reference mark. The two sets may be separate rows of photodectors or different elements of the same row of photodetectors. The pattern is preferably irregular.

Abstract: A method of measuring an object on a coordinate positioning apparatus. A first object is placed on a coordinate positioning apparatus and measured with a workpiece contacting probe to create measurement data. The measurement data is collected at multiple stylus deflections or probe forces. For a plurality of points on the surface of the first object, the measurement data is extrapolated to that corresponding to zero stylus deflection or zero probe force. An error function or map is created from the measurement data and the extrapolated data. Subsequent objects are then measured using a known stylus deflection or known probe force and the error function or map is used to apply an error correction to these measurements.

Abstract: An optical slit comprises two blades 40,42 which define a slit between them, each blade being independently movable. This enables both the slit position and the slit width to be adjusted. The slit may be aligned with the center of a light beam by aiming the light beam at a detector, traversing at least one edge of the slit across the beam path, measuring the intensity of transmitted light at the detector for each position of the slit, and feeding back a signal which adjusts the slit position for maximum light throughput. The width on the optical slit may be selected by placing the slit in the path of the light beam and measuring the light transmitted at the detector, calculating the percentage of light transmitted for that slit width and feeding back a signal which adjusts slit width to obtain the desired amount of light throughput.

Abstract: A scale (10) has magnetic incremental scale marks in a track (10a), and a pseudo-random code sequence in a reference mark track (10b). Sensors (2,3) feed the pattern of the code in the track (10b) into a bi-directional shift register (18). So that a user can select any desired position for use as a reference mark, a memory (24) is provided, into which any selected code value can be pre-stored. A comparator (26) then compares the code value in the shift register (18) with the code value in the memory (24) and outputs a reference mark signal (Ri) when they match.

Abstract: The present invention teaches a method and apparatus for making measurement of an object on a machine, such as a machine tool, using an optical measuring apparatus which includes a light source for generating a beam of light which is incident on a detector. A detection signal is generated within the detector each time the beam is interrupted. The duration and/or frequency of the detection signals are evaluated and an output signal is emitted from the detection only if a further detection signal is present within the detector in a specified time interval from the generation of an earlier detection signal.

Abstract: An optical apparatus e.g. an interferometric displacement determination device: spectroscopic analysis apparatus; polarisation measurement apparatus; or a heterodyne frequency measurement device has a linear HeNe gas laser having an Ne content of an Ne20 isotope and an Ne22 isotope in substantially equal proportions, the apparatus in use having optical feedback toward the laser causing, 0.1% or more of the light output of the laser to be returned toward the laser (1). Use of this type of laser provides good polarisation stability even though excessive backreflection may occur, and hence the laser's frequency can be readily controlled.

Abstract: An optical pulse signal from a machine tool measuring probe is received by a photodiode (28). To reduce interference from xenon strobe beacons, fluorescent lights etc., the pulse signal is processed by an AGC amplifier (30) with low frequency signal cancellation, and the pulses are then detected by a threshold detector (32). The threshold of this detector (32) is variable by a circuit (50), in accordance with the overall amplitude of the signal pulses, in order to provide the best rejection of interference pulses.

Abstract: A rotary ring 3 for use in scale reading apparatus has a scale on its outer circumference and is mounted on a rotary shaft 6. To reduce error caused by the rotary ring 3 not sitting concentrically on the rotary shaft 6, the inner circumference 5 of the rotary ring 3 and the outer circumference of the shaft 6 are both tapered. To compensate for eccentricity of the shaft, mounting screws 8 are provided in holes on the rotary ring to adjust the position of the rotary ring until it is concentric with the axis of rotation of the shaft.

Abstract: A probe arm for locating a probe on a machine includes a signal conditioning circuit which produces probe status signals to be sent to the machine. The signal conditioning circuit includes two LEDs mounted on the arm and which are differently coloured to provide a visual indication of probe status e.g. probe ready or probe triggered. One of the LEDs has twice the efficiency of the other and therefore to maintain consistent illumination one is driven with twice the current of the other. Thus by monitoring the current through the LEDs in a sensing circuit at the output terminals of the signal conditioning circuit the status of the probe is communicated to the machine. Power to the probe and signal conditioning circuit is provided from the machine via the output terminals so that only two wires are required to connect the arm to the machine.

Abstract: A coordinate measuring machine (CMM) carries a probe and is controlled by a controller to drive the probe to take measurements on a workpiece. In order to reduce the effects of acceleration-induced deflections of the probe on the measurements made by the machine, accelerometers are provided to measure the accelerations of the probe and to produce signals indicative thereof. The acceleration signals (45) are passed to the controller (FIG. 2) where they are integrated (46) and filtered (48) before being passed as velocity signals (49) to a summing junction (50) from which they are fed to a velocity feedback control loop (34,35,36,37) which reduces any changes in the velocity (and hence deflection) of the probe due to the accelerations.

Abstract: A coordinate positioning machine has an operating module such as a tool or probe (10) mounted for translational motion relative to a table (16) with three degrees of freedom by means of three articulated linkages (18). Each of the linkages is made up of a torsion box (22) which is pivotally mounted to a vertical pillar (20) with one degree of freedom, and a pair of struts (26), each of which is pivotally mounted with two degrees of freedom to the torsion box at one end, and to the operating module at the other. The linkages cooperate to prevent all rotational motion of the operating module, while allowing translation. Motion of the operating module is actuated manually, and the mass thereof is counterbalanced by an articulated counterbalance arm 90 which guides a cable 96 that is in turn connected to a fusee. Displacement of the operating module is measured using scale and readhead encoders (40,50).

Abstract: A coordinate positioning machine comprises a fixed structure including a table and a supporting frame, rigidly connected together. A movable arm is suspended from the frame by means of three powered telescopic struts, each of which is universally pivotally connected to both the arm and the frame. As a consequence, the movable arm is able to move with three rotational degrees of freedom. Movement of the arm with each of these degrees of freedom is constrained by a passive device, connected to the arm and the fixed structure, and which eliminates all rotational movement of the arm, while simultaneously permitting translation thereof.

Abstract: An interface circuit for processing signals from a touch trigger probe is adapted to prevent the generation of false trigger signals during an inspection cycle. The probe incorporates a plurality of strain gauges, the voltage across which rises above a predetermined threshold when a stylus supported by the probe contacts a surface. When the probe is moved away from the surface and the stylus loses contact, the outputs across the gauges drop below the trigger threshold. The interface prevents false triggers When, while the stylus is in contact with a surface, a machine vibration occurs which causes an oscillation in the voltage across the gauges; the voltage dropping below the threshold level (causing the interface to reset), and then immediately passing back up through the threshold, causing the interface to emit a trigger signal.

Abstract: A touch trigger probe for a coordinate measuring machine or machine tool has a stylus, which is biased into a rest position. The stylus has two independent supports, provided within a housing. A first support comprises a skirt of a stylus holder which is axially constrained on a surface of the housing. The second support comprises a kinematic arrangement of cylinders and balls, together with a planar spring, which together provide lateral constraint. The first support is biased by a much lighter force than the second support, so that its friction is very low. This reduces the lobing and hystersis of the stylus movement, and thereby increases the accuracy of the probe. The stylus movement first takes up a clearance between the first support and an abutment surface of the housing and then disengages the kinematic arrangement of the second support upon further stylus movement.

Abstract: A method of determining surface contour of diffusely reflecting objects is realized by interferometric comparison of beams reflected from a reference mirror and from an object (11), by changing the optical path length of the object beam, by focusing the object beam onto a plane corresponding to the zero path length difference between the beams being compared interferometrically, and by measuring said variation of the optical path length from an initial value up to a moment when appears an interference pattern displaying maximum contrast.

Abstract: A touch trigger probe for a coordinate measuring machine or machine tool has a stylus (14), which is biased into a rest position. The stylus has two independent supports, provided within a housing (10). In the embodiment of FIG. 1, the first support comprises a skirt (18) of a stylus holder (12), which is axially constrained on a surface (20) of the housing (10). The second support comprises a kinematic arrangement of cylinders (34) and balls (36), together with a planar spring (30), which together provide lateral constraint. The first support is biased by a much lighter force than the second support, so that its friction is very low. This reduces the lobing and hysteresis of the stylus movement, and thereby increases the accuracy of the probe.

Abstract: A capacitance sensing probe is disclosed for taking measurements of features on a workpiece surface. The probe has two electrodes (E.sub.1, E.sub.2) spaced apart in the direction of movement of the probe with the electrodes being disposed in an attitude normal to the surface. Only the edge of the electrodes are exposed to the surface and an electric circuit (EC) is provided for determining the effect of the surface on the fringe field capacitance between the electrodes. Guard electrodes are used to reduce the stray capacitance being measured. Various embodiments are shown with different numbers and arrangements of electrodes.