Renishaw Plc

Renishaw Transducer Systems Limited

Colin Keith Howley

James Reynolds Henshaw

Peter Geoffrey Holden

Adam Michael Whiting

Simon Eliot McADAM

Simon Eliot Mcadam

An incremental encoder apparatus including: a scale including a series of periodic features defining an optical incremental scale, and at least one magnetic reference mark; and a readhead. The readhead includes at least one incremental sensor configured to detect light from the optical incremental scale and to output at least one signal dependent thereon, and at least two analogue Hall sensors, each including at least two output terminal pairs, and each configured to switch repeatedly between each output terminal pair so as to reduce any inherent offset in the output of the analogue Hall sensor. The apparatus is configured to determine the presence of the reference mark from the outputs of the at least two analogue Hall sensors.

Encoder apparatus

A scale reading apparatus includes a readhead that is moveable relative to a scale. The readhead includes an incremental channel from which a series of reference mark pulses are produced as the readhead is moved relative to the scale. A reference mark channel is also provided that produce a reference mark gating pulse when the readhead passes a predetermined (absolute) position mark on the scale. An alignment detection unit monitors during use, phase alignment of the reference mark gating pulse and reference mark pulses. The alignment detection unit is arranged to monitor the phase of the leading and trailing edges of said reference mark gating pulse relative to the phase of the reference mark pulses. The apparatus may be used in position encoders and the like.

Scale and readhead apparatus and method

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.

Scale and readhead system

A scale for a scale reading apparatus has a scale track with scale marks which form an incremental scale. The scale also has a set of reference marks. The scale has at least one additional track and different combinations of markers in the at least one additional track have different functions, for example reference mark enablers and right and left limit switches.

Scale reading apparatus

Opto-electronic linear encoding apparatus includes a scale and a readhead movable relative to the scale in a direction of spacing of the scale lines. The readhead is formed of a single semi-conductor substrate, typically made of gallium arsenide. The substrate is divided into two regions, the first region including a light emitting diode having a plurality of elongate electrodes provided on its upper surface and spaced in the direction of spacing of the scale lines. The light emitting diode region, the elongate electrodes and the substrate cooperate to produce a plurality of coplanar elongate light emitting regions between the elongate electrodes which perform the combined functions of a diffused light source and an index grating. The second region is an analyzer having a plurality of elongate photosensitive elements spaced apart in the direction of spacing of the scale lines. The photosensitive elements are divided into a plurality of sets and are interleaved on the substrate in a repeating pattern with the outputs of elements of a given set being connected in common. The analyzer thus performs the combined functions of an analyzer grating and a plurality of photodetectors which generate a plurality of phase-shifted cyclically varying signals.

Opto-electronic scale reading apparatus having an array of elongate

A readhead 10 traverses along a scale 12, producing square wave signals in quadrature on lines 24,26. These are counted by an external counter 28 to indicate the position along the scale. The square waves cannot be used to monitor the orientation and stand-off of the readhead 10 relative to the scale 12. To achieve this, therefore, circuitry within the readhead 10 monitors the sinusoidal quadrature signals from which the square waves are produced, and gives a simple go/no-go indication on a LED 62 when these signals have an acceptable amplitude and are in an acceptable quadrature relationship.

Readhead for producing signals when travelling along a scale having a

Setting up of quadrature signals

Quadrature input signals from an opto-electronic or magnetic readhead which is movable relative to a periodically marked scale, are respectively multiplied by quadrature reference signals from a reference oscillator in multipliers. The resulting signals are added together in a mixer to give a signal (S) having a frequency which is the reference frequency shifted by the frequency of the input signals. This signal (S) is then compared with the reference signal. The reference signals are generated from a high frequency clock which is subsequently used to compare the period of the reference signal with that of the signal (S), giving outputs which interpolate the position of the readhead within the pitch of the marks on the scale.

Processing quadrature signals

A frequency-to-voltage converter, as applied to controlling the speed of a motor, comprises: a motor speed encoder (1) producing first and second alternating signals (3a,3b) each at the same, first frequency which frequency is dependent on the said speed, the first and second signals being in quadrature with each other; a reference oscillator (4), for producing third and fourth alternating signals (5a,5b) each at the same, reference frequency, which frequency is higher than said first frequency, the third and fourth signals being in quadrature with each other; and single sideband modulating means (6,7,8) connected to receive the first, second, third and fourth signals and to produce a fifth alternating signal (8a) which is a frequency-shifted version of one of the first and second signals. The fifth signal and one of the third and fourth signals (5b) are applied to respective frequency-to-voltage converters (9,10), the DC output voltages of which are subtracted from each other in a differential amplifier (12). The DC output voltage of the amplifier is proportional to the speed of the motor and is used to control the speed to a desired value. The converter provides a DC signal inherently free from ripple over a wide dynamic range.

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Stonehouse, United Kingdom

Colin Keith Howley