Abstract: A signal conditioning circuit for multiple channel capacitive displacement transducers. The transducer 30 comprises three differential capacitive transducers, driven by respective square waves from modulators 32x, 32y, 32z. The modulators are driven at different frequencies which are even multiples of each other, derived from a divider 68. The signals from each differential capacitance pair of the transducer 30 are received by a common charge amplifier 48. They are then demodulated by respective phase sensitive rectifiers 50x, 50y, 50z, each of which is driven at the same frequency as the corresponding modulator. The outputs of the phase sensitive rectifiers are integrated, e.g. by circuits 60,62,44 for one of the channels, and the resulting voltage signal is fed back to the corresponding modulator so as to tend to null the input to the charge amplifier 48. The use of modulating frequencies which are even multiples of each other enables the signals to be multiplexed through a single charge amplifier 48.

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.

Abstract: A scale is fixed to one part of a position determining apparatus, and a read head is relatively movable on the other part of the apparatus. Incremental scale marks are regularly spaced along the scale and are counted in a counter to give an indication of relative position of the scale and read head. The marks may for example be recorded magnetically. Some scales are distinguishable from the other, e.g., by having different amplitudes. Positioning information can then be encoded in a binary word. This can either be absolute position values, or error correction information.

Abstract: In an optical detection system a plurality of photodiode detectors are placed in an enclosure. The enclosure has an aperature through which is directed a light beam to be analyzed. To eliminate the effect which ambient light entering the aperture would have on the detector signals, each of the detectors are arranged to be at equal distances from the aperture so that they all have the same acceptance cone angle for the light entering the aperture. Thus the ratio of signal to ambient light in the portion of the light beam reaching each detector is the same and the d.c. component of the signal produced by the detector can be easily removed in the signal conditioning electronics. The equal spacing of the detectors from the aperture is achieved in accordance with the invention by using beam splitters in the path of the beam to deflect portions of the beam to detectors which are offset from the base axis.

Abstract: An alingment adjusting mechanism secures and adjusts the alignment of a magazine (10) which retains a plurality of sensing elements (12) within the working area of a coordinate measuring machine) relative to the bed of a machine on which the magazine is mounted. The mechanism comprises a plate (20), rigidly connected to the bed, and a base (18), which supports the magazine (10) secured to the bed of the machine via the plate (20); the base (18) is resiliently secured to the plate (20) by bolts (26), washers (27) and disc springs (30). The bearing end of a grub screw (40) engages a conical recess (46), thus providing a pivot point for pivoting of the base (18) relative to the plate (20). Two further pairs of grub screws (34) and (48) bear against the plate (20). Adjustment of the attitude of the base (18) about the axes (56) (the roll), (54) (the pitch), and (58) (the yaw) is achieved using the grub screws (34, 40, 48).

Abstract: The invention provides an opto-electronic scale reading apparatus comprising a read head in which a plurality of optical emitter and receiver pairs are arranged so that beams of collimated light generated by the respective emitters fall on a common region of a scale. Compared to arrangements where the light beams fall on separate regions of the scale, the apparatus according to the invention is relatively immune to the effects of certain misalignments between the scale and the read head.

Abstract: A device for changing styli or probes in a coordinate measuring machine has a magazine (330) with several stations each holding a stylus or probe (320). A holder (310) on the quill of the coordinate measuring machine has an opening (313A), so that kinematic support elements (325) in the holder (310) can be moved underneath cooperating kinematic support elements (324) on the stylus (320). The holder (310) is then lifted up to engage the kinematic support elements, and the stylus can then be carried horizontally out of the magazine (30). During this operation, the kinematic support elements are biased into engagement initially by a leaf spring (335), and subsequently by a spring-loaded arm (314) in the holder (310), which bears against the top of a plate (322) of the stylus (320). When the holder (310) is engaged in the magazine (330), an extension plate (334) causes the arm (314) to swing out of the way.

Abstract: An opto-electronic scale-reading apparatus comprising a read head and a scale supported for displacement relative to each other for the incremental reading of marks provided on the scale. The read head includes a light source for producing light rays incident on the scale, an index grating for diffracting readable rays into fringes in at least one order of diffracton, and an analyzer grating for converting the fringes into light modulations at a rate which is a function of the rate of displacement between the read head and the scale. The scale comprises an elongate member having marks spaced in the direction of its length and spaces defined between the marks. The marks and spaces are defined by respective first and second surfaces of surface portions of the members, the first surfaces laying at an angle to adjacent second surfaces so that incident rays are reflected by the first surfaces in a first direction to be readable by the read head in the first direction.

Abstract: An optical electronic scale reading apparatus comprising a scale read by a read head to determine the relative displacement therebetween. The read head comprises reflective surfaces so arranged that light from a source is reflected therefrom and interacts with the scale at first, second and third positions. At the third position, a fringe field is developed which has the same pitch as the scale. A detector is provided to receive light modulations during relative movement of the scale and read head as the fringe field interacts with the scale at the third position. These modulations are counted to determine the relative displacement between the scale and read head.

Abstract: Optical scale reading apparatus in accordance with the invention includes an optical fibre 30 for directing light from a light source 22 on to a scale 10. Light from the scale is reflected into a readhead 12 of any suitable construction. The fibre is designed to reduce any non-uniformity in the light entering it and various embodiments of the invention are described for achieving the required effect. For example, the length to diameter ratio of the fibre is made to be at least 5:1. Alternatively, or in addition, one or more constrictions are formed in the fibre, and as a further alternative or addition, at least one end face of the fibre is roughened to cause diffusion of the light.

Abstract: An opto-electronic scale-reading apparatus comprising a scale defined by marks provided on one of two members, a read head provided on the other member and including diffraction means for producing interference fringes having movement relative to the read head responsive to a displacement between the scale and the read head, and detecting means for detecting the movement of the interference fringes. The scale marks may have periodicities differing from a nominal value, and the apparatus includes a spatial filter whereby scale periodicities, differing from the nominal value by more than a given maximum, are prevented from contributing to the production of said fringes.

Abstract: The invention concerns a focus detection circuit for an optical trigger probe. The probe has a laser light source, a beam splitter and a focusing lens system. The probe produces a light beam focused to a point at a distance d from the probe. Light reflected from the surface is reflected from the beam splitter onto two pairs of photosensitive detectors. The signals from the two outer detectors are added as are the signals from the two inner detectors, and the two sums are subtracted to provide a focus error signal which is passed to a zero crossing detector. When the light beam is focused on the surface, the difference between the sums of the detector signals will be zero and the zero crossing detector circuit emits an output pulse. To eliminate false trigger signals when the probe is some distance from the workpiece and the reflected light is minimal, a validating signal is generated by measuring the intensity of the relected light at a detector.

Abstract: Measuring apparatus for use in measuring relative movements of two objects and wherein a scale and scale reader are provided mounted respectively on the objects for providing an accurate determination of the relative positions of the two objects with reference to the marks on the scale, the positions of which are accurately known. An interferometer is also provided for measuring the relative movements of the scale and scale reader in order to provide an accurate determination of the relative positions of the two objects at positions between the scale marks. In order to correlate the readings of the scale reader and the interferometer, the scale reader outputs a signal to the interferometer each time a scale mark is detected and the interferometer reading is updated.

Abstract: An apparatus for determining values of a periodic function by interpolation which comprises a reading device for receiving scanning signals A,B,C,D nominally in phase quadrature with each other from the periodic function. The signals are combined in a converter to produce sine and cosine derived signals SN,CS from which interpolation is performed by a computer. Each of the derived signals SN,CS is derived from at least three of the scanning signals A,B,C,D, for example, in the forms 2B-A-D and 2B-A-B.

Abstract: A machine tool has a table movable relative to a head for machining a workpiece mounted on the head by a tool mounted on the table. The table also supports a magazine for blank workpieces, and the table is movable between a first position in which the head and the tool are in machining promitiy and a second position in which the head and the magazine are proximate. The head has a work holder adapted to grip a blank workpiece at said second position for transfer, by movement of the table, to said first position. After machining, the workpiece is correspondingly returnable to the magazine. The work holder is mounted on a spindle supported on the head and rotatable for machining purposes. In a modification the spindle supports a tool, and the head has a gripper which is separate from the spindle and is used for the transfer of workpieces between the magazine and a work holder mounted on the table.

Abstract: A contact-sensing probe for measuring workpieces includes a body (16) for attachment to a machine and a workpiece contacting stylus (22) carried by a stylus holder (24) which is mounted within the body for movmeent relative thereto from a rest position to a displaced position when the stylus contacts the workpiece. Sensors are provided for sensing workpiece contact by the stylus. The sensors comprise a plurality of strain gauges (46) mounted on pillars (44) connecting two parts (36A,36B) of a support structure which supports the stylus holder on the body. The strain gauges are mounted with their principal axes lying at an angle to the axes of the pillars, and by optimizing the numbers, positions and dimensions of the pillars together with the angles of the strain gauges, high sensitivity can be achieved with minimum risk of false signals due to probe vibration, while at the same time minimizing the variation in pre-travel of the stylus.

Abstract: A cutting tool includes a motor and control inside the cutting tool for adjusting the cutting radius of the cutting tool. The cutting tool is adaptable for use with machine tools which do not include integral systems for moving parts of the cutting tool adjust the cutting radius.

Abstract: A position determination apparatus comprising a coordinate measuring machine having a scale. In addition, a read/write head and a laser interferometer system are provided, both of which can measure the position of a probe. The head writes signals derived from the interferometer onto the scale and is used either to lay down the periodic scale marks, or to write error correction values onto the scale. The scale is thus calibrated in situ on the machine.

Abstract: A metrological scale for use in optoelectronic scale reading apparatus comprising a tape made of spring steel and having a surface layer of copper. The scale has scale marks constituted by a zig-zag or other profile impressed into the surface layer by a rolling process. During rolling, the relatively soft copper is readily deformed to accept the profile while the spring steel resists plastic elongation of the tape.

Abstract: A probe (12) is connected to an interface circuit (10). The probe (12) has two different types of contact sensors, namely a piezo electric sensor and an electro-mechanical switching sensor. The trigger signal from the piezo electric sensor is detected by circuits (34,36,38,40) while that from the switching sensor is detected by a comparator (32). The signals are mixed in a mixer (42) to produce a single output trigger signal. A monostable (48) and latch (50) discriminate which sensor produced the output signal, making use of the inherent time delay between the two sensor signals. Circuits (24,26,28) determine if a conventional switching probe has been connected instead of the probe (12). If so, a transistor (T4) varies the power supply to the probe, and gates (30,33) switch in a comparator (18) in place of the comparator (32).