Encoder readhead
First Claim
1. A readhead arranged to read an absolute scale encoding a series of data bits, the readhead comprising:
- a plurality of sensors that are each arranged to produce a sensor signal indicative of measured magnetic field strength;
a plurality of signal combiners, each signal combiner being arranged to receive at least two of the sensor signals produced by the plurality of sensors and to produce therefrom a combined sensor signal, the plurality of signal combiners thereby generating a plurality of combined sensor signals;
a plurality of data bit extractors for generating absolute position data and arranged to receive the plurality of combined sensor signals, each data bit extractor being arranged to receive at least two of the combined sensor signals and to determine the value of a data bit encoded in an associated absolute scale; and
an incremental signal generator arranged to receive at least two of the plurality of combined sensor signals also received by the data bit extractors and to generate at least one incremental signal from the at least two combined sensor signals.
1 Assignment
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Accused Products
Abstract
A readhead is provided for reading an absolute scale, optionally a passive magnetic scale, that encodes a series of data bits. The readhead includes a plurality of sensors, such as an array of Hall sensors, for producing a plurality of sensor signals. A plurality of signal combiners are also provided to receive at least two of the sensor signals and produce therefrom a combined sensor signal. A plurality of data bit extractors are arranged to receive at least two combined sensor signals and to determine the value of a data bit encoded in an associated absolute scale. The readhead also comprises an incremental signal generator for generating at least one incremental signal from the combined sensor signals produced by a plurality of the signal combiners. In this manner, both absolute and incremental position is measured.
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Citations
23 Claims
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1. A readhead arranged to read an absolute scale encoding a series of data bits, the readhead comprising:
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a plurality of sensors that are each arranged to produce a sensor signal indicative of measured magnetic field strength; a plurality of signal combiners, each signal combiner being arranged to receive at least two of the sensor signals produced by the plurality of sensors and to produce therefrom a combined sensor signal, the plurality of signal combiners thereby generating a plurality of combined sensor signals; a plurality of data bit extractors for generating absolute position data and arranged to receive the plurality of combined sensor signals, each data bit extractor being arranged to receive at least two of the combined sensor signals and to determine the value of a data bit encoded in an associated absolute scale; and an incremental signal generator arranged to receive at least two of the plurality of combined sensor signals also received by the data bit extractors and to generate at least one incremental signal from the at least two combined sensor signals. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21)
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22. A readhead arranged to read an absolute scale encoding a series of data bits, the readhead comprising;
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a plurality of sensors arranged to produce a plurality of sensor signals; a plurality of signal combiners, each signal combiner arranged to receive at least two of the sensor signals and to produce therefrom a combined sensor signal, and each signal combiner arranged to receive its combined sensor signal by combining the sensor signals from a plurality of adjacent sensors of the plurality of sensors; a plurality of data bit extractors, each data bit extractor being arranged to receive at least two combined sensor signals and to determine the value of a data bit encoded in an associated absolute scale; and an incremental signal generator arranged to generate at least one incremental signal from the combined sensor signals produced by a plurality of the signal combiners, wherein the plurality of signal combiners are arranged to generate a plurality of combined sensor signals (Si) from the plurality of sensor signals (Hi) produced by the plurality of sensors in accordance with the summation scheme;
Si=Hi−
Hi+1−
Hi+2+Hi+3;
i=1 . . . (4·
N)N being the number of data bits in each codeword encoded by the associated absolute scale, the readhead comprising 4N+3 sensors, and the sensors being spaced apart so as to provide four sensors per bit length L of the associated absolute scale.
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23. An encoder device comprising:
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a passive absolute magnetic scale comprising a scale member and a plurality of scale markings arranged to encode a series of data bits of bit length L, the scale markings having a different magnetic permeability than the scale member, the plurality of scale markings being a plurality of grooves, the plurality of grooves comprising grooves of at least a first groove type and a second groove type, the magnetic permeability of the passive absolute magnetic scale in the locality of grooves of the first groove type being different than the magnetic permeability of the passive absolute magnetic scale in the locality of grooves of the second groove type, and a groove of the first groove type indicating a data bit having a first value and a groove of the second groove type indicating a data bit having a second value; and a readhead arranged to read an absolute scale encoding a series of data bits, the readhead comprising; a plurality of sensors arranged to produce a plurality of sensor signals, the readhead comprising an integer number of sensors per bit length L, a plurality of signal combiners, each signal combiner being arranged to receive at least two of the sensor signals and to produce therefrom a combined sensor signal, a plurality of data bit extractors, each data bit extractor being arranged to receive at least two combined sensor signals and to determine the value of a data bit encoded in an associated absolute scale, and an incremental signal generator arranged to generate at least one incremental signal from the combined sensor signals produced by a plurality of the signal combiners.
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Specification