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US 9,285,245 B2Granted
Absolute encoder
AssigneeCanon Kabushiki Kaisha
InventorYoshiyuki Okada
Life of this patent
Estimating the term…
Abstract
The present invention provides an absolute encoder including a scale on which a first mark and a second mark are arrayed, a detector configured to detect light from the scale, and to output periodic signals in which peak values, including a first peak value corresponding to the first mark and a second peak value corresponding to the second mark and smaller than the first peak value periodically appear, and a processor configured to obtain a code sequence by binarization of the first peak value and the second peak value in the periodic signals output from the detector, wherein the processor has a function of performing calibration so that the first peak value becomes larger than a threshold for the binarization and the second peak value becomes smaller than the threshold.
Claims12
An absolute encoder comprising:
- a scale on which a first mark and a second mark are arrayed;
- a light source configured to emit light with which the scale is irradiated;
- a detector configured to detect light from the scale, and to output periodic signals in which peak values, including a first peak value corresponding to the first mark and a second peak value corresponding to the second mark and smaller than the first peak value, periodically appear;
- and
- a processor configured to obtain a code sequence by binarization of the first peak value and the second peak value in the periodic signals output from the detector,
- wherein the processor has a function of performing calibration so that the first peak value becomes larger than a threshold for the binarization and the second peak value becomes smaller than the threshold,
- the processor being further configured to
- specify a largest first maximum value and a smallest second maximum value among maximum values of the periodic signals with regard to respective periods thereof, and
- set an intensity of the light emitted by the light source so that the first maximum value is not smaller than a first reference value larger than the threshold, and the second maximum value is not larger than a second reference value smaller than the threshold.
6 more elements
An absolute encoder comprising:
- a scale on which a first mark and a second mark are arrayed;
- a detector configured to detect light from the scale, and to output periodic signals in which peak values, including a first peak value corresponding to the first mark and a second peak value corresponding to the second mark and smaller than the first peak value, periodically appear;
- an amplifier configured to amplify the periodic signals output from the detector;
- and
- a processor configured to obtain a code sequence by binarization of the first peak value and the second peak value in the amplified periodic signals output from the amplifier,
- wherein the processor has a function of performing calibration so that the first peak value becomes larger than a threshold for the binarization and the second peak value becomes smaller than the threshold,
- the processor being further configured to
- specify a largest first maximum value and a smallest second maximum value among maximum values of the periodic signals with regard to respective periods thereof, and
- set a gain of the amplifier so that the gain is not smaller than a value obtained by dividing a first reference value larger than the threshold by the first maximum value, and is not larger than a value obtained by dividing a second reference value smaller than the threshold by the second maximum value.
6 more elements
An absolute encoder comprising:
- a scale on which a first mark and a second mark are arrayed;
- a detector configured to detect light from the scale, and to output periodic signals in which peak values, including a first peak value corresponding to the first mark and a second peak value corresponding to the second mark and smaller than the first peak value, periodically appear;
- a processor configured to obtain a code sequence by binarization of the first peak value and the second peak value in the periodic signals output from the detector,
- wherein the detector includes a photoelectric conversion device configured to perform photoelectric conversion of the light from the scale to output the periodic signals, and
- wherein the processor has a function of performing calibration so that the first peak value becomes larger than a threshold for the binarization and the second peak value becomes smaller than the threshold,
- the processor being further configured to
- specify a largest first maximum value and a smallest second maximum value among maximum values of the periodic signals with regard to respective periods thereof, and
- set an accumulation time of the photoelectric conversion device based on a time ratio which is not smaller than a value obtained by dividing a first reference value larger than the threshold by the first maximum value, and is not larger than a value obtained by dividing a second reference value smaller than the threshold by the second maximum value.
5 more elements
An absolute encoder comprising:
- a scale on which a first mark and a second mark are arrayed;
- a detector configured to detect light from the scale, and to output periodic signals in which peak values, including a first peak value corresponding to the first mark and a second peak value corresponding to the second mark and smaller than the first peak value, periodically appear;
- a processor configured to obtain a code sequence by binarization of the first peak value and the second peak value in the periodic signals output from the detector,
- wherein the processor has a function of performing calibration so that the first peak value becomes larger than a threshold for the binarization and the second peak value becomes smaller than the threshold,
- the processor being further configured to specify a largest first maximum value and a smallest second maximum value among maximum values of the periodic signals with regard to respective periods thereof, and
- perform the calibration so that a value obtained by correcting the first maximum value based on a maximum value of variations in intensity of light from the first mark is not smaller than a first reference value larger than the threshold, and a value obtained by correcting the second maximum value based on a maximum value of variations in intensity of light from the second mark is not larger than a second reference value smaller than the threshold.
3 more elements
An absolute encoder comprising:
- a scale on which a first mark and a second mark are arrayed;
- a detector configured to detect light from the scale, and to output periodic signals in which peak values, including a first peak value corresponding to the first mark and a second peak value corresponding to the second mark and smaller than the first peak value, periodically appear;
- and
- a processor configured to obtain a code sequence by binarization of the first peak value and the second peak value in the periodic signals output from the detector,
- wherein the processor has a function of performing calibration so that the first peak value becomes larger than a threshold for the binarization and the second peak value becomes smaller than the threshold,
- the processor being further configured to
- specify, among maximum values of the periodic signals with regard to respective periods thereof, a largest first maximum value, a smallest second maximum value, a third maximum value which is smaller than the first maximum value, larger than a first value between the first maximum value and the second maximum value, and closest to the first value, and a fourth maximum value which is larger than the second maximum value, smaller than the first value and closest to the first value, and
- perform the calibration so that a value obtained by correcting the third maximum value is not smaller than a first reference value larger than the threshold, and a value obtained by correcting the fourth maximum value is not larger than a second reference value smaller than the threshold.
5 more elements
An absolute encoder comprising:
- a scale on which a first mark and a second mark are arrayed;
- a detector configured to detect light from the scale, and to output periodic signals in which peak values, including a first peak value corresponding to the first mark and a second peak value corresponding to the second mark and smaller than the first peak value, periodically appear;
- and
- a processor configured to obtain a code sequence by binarization of the first peak value and the second peak value in the periodic signals output from the detector,
- wherein the processor has a function of performing calibration so that the first peak value becomes larger than a threshold for the binarization and the second peak value becomes smaller than the threshold, the processor being further configured to
- specify a largest first maximum value and a smallest second maximum value among maximum values of the periodic signals with regard to respective periods thereof, and
- perform the calibration so that the first maximum value is not smaller than a first reference value larger than the threshold, and the second maximum value is not larger than a second reference value smaller than the threshold.
4 more elements
Dependencies are inferred from the claim text.