Scale reading apparatus
First Claim
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1. Scale reading apparatus comprising:
- a scale and readhead moveable relative to one another, said scale having scale markings arranged to form a first incremental pattern having a first scale pitch and at least one scale marking arranged to form a second incremental pattern having a second scale pitch, different to said first scale pitch;
a first detector to detect said first incremental scale pattern;
a second detector to detect said second incremental pattern;
wherein both first and second detectors are provided in the same readhead; and
the output of at least one of the first and second detectors may be selected to provide incremental position information.
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Abstract
Scale reading apparatus having a scale and readhead moveable relative to one another. The scale has a first incremental scale pattern with a fine pitch and a second incremental scale pattern with a coarse pitch. The readhead has a detector to detect each of the incremental scale patterns. The scale reading apparatus can be used for both slow speed and fast speed measurements. The second incremental scale pattern may be provided in a scale track which has a dual function (e.g. limit track or reference mark) and the readhead may be configured to decode the signal to produce an output suitable for the desired function.
32 Citations
40 Claims
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1. Scale reading apparatus comprising:
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a scale and readhead moveable relative to one another, said scale having scale markings arranged to form a first incremental pattern having a first scale pitch and at least one scale marking arranged to form a second incremental pattern having a second scale pitch, different to said first scale pitch; a first detector to detect said first incremental scale pattern; a second detector to detect said second incremental pattern; wherein both first and second detectors are provided in the same readhead; and the output of at least one of the first and second detectors may be selected to provide incremental position information. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. A method for detecting the relative position or speed of a scale and readhead of a scale reading apparatus comprising a scale, said scale having scale markings arranged in a first incremental pattern having a first scale pitch and at least one scale marking arranged in a second incremental pattern having a second scale pitch, said first scale pitch being different to said second scale pitch, and a readhead comprising a first detector to detect said first incremental scale pattern and a second detector to detect said second incremental pattern, the method comprising the steps of:
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outputting signals from the first and second detectors; and selectively using the output of at least one of the first detector and the second detector to provide incremental position information. - View Dependent Claims (15, 16, 17, 18, 19, 20)
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21. A scale reading system comprising a scale and readhead moveable relative to each other and configured to determine relative data at at least two different incremental resolution levels;
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and a communications link outputting data from the readhead; wherein the position data at the at least two different incremental resolution levels is sent down the same communications link. - View Dependent Claims (22, 23, 24, 25, 26, 27)
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28. A scale reading apparatus comprising:
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at least one scale marking; a readhead with a transducer system to detect the at least one scale marking and to produce signals relating to the at least one scale marking; and a configurator which selects a signal decoding method to produce an output from the signal relating to one of an incremental function or at least one alternative function. - View Dependent Claims (29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40)
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Specification