INDEXED OPTICAL ENCODER, METHOD FOR INDEXING AN OPTICAL ENCODER, AND METHOD FOR DYNAMICALLY ADJUSTING GAIN AND OFFSET IN AN OPTICAL ENCODER
First Claim
1. An optical encoder comprising:
- an encoder disk comprising;
a signal track comprising a diffraction grating formed as a ring on the encoder disk; and
an index track comprising a reflective index mark, wherein a width of the index mark is larger than a pitch of the diffraction grating;
an illumination system structured to direct light to the encoder disk; and
a detector structured to detect light diffracted from the encoder disk.
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Accused Products
Abstract
An optical encoder may include an encoder disk, an illumination system, and a detector to detect light diffracted from the encoder disk. The encoder disk may include a signal track comprising a diffraction grating, and an index track comprising a reflective index mark, wherein a width of the index mark is larger than a pitch of the diffraction grating. An indexing method may include providing an encoder disk, providing an illumination system to direct light to the encoder disk, providing a detector structured to detect light diffracted from the encoder disk, calculating an estimated count of quadrature states from a rising edge of an index pulse to a middle of the index interval, and calculating the quadrature state at an approximate center of the index pulse. A dynamic parameter correction method may include calculating a target gain and offset and correcting values based on the target gain and offset.
100 Citations
36 Claims
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1. An optical encoder comprising:
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an encoder disk comprising; a signal track comprising a diffraction grating formed as a ring on the encoder disk; and an index track comprising a reflective index mark, wherein a width of the index mark is larger than a pitch of the diffraction grating; an illumination system structured to direct light to the encoder disk; and a detector structured to detect light diffracted from the encoder disk. - View Dependent Claims (4, 5, 6, 7, 8, 9, 10, 11, 12)
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2. The optical encoder of claim 2, wherein the index track comprises:
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a first index track formed as a ring on the encoder disk; and a second index track formed as a ring on the encoder disk. - View Dependent Claims (3, 13, 35)
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14. An encoder disk for use in an optical encoder, the encoder disk comprising:
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a signal track comprising a diffraction grating formed as a ring on the encoder disk; and an index track comprising a reflective index mark, wherein a width of the index mark is larger than a pitch of the diffraction grating. - View Dependent Claims (15, 16, 17, 18, 19, 20, 21, 22, 36)
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23. An indexing method for use with an optical encoder, the indexing method comprising:
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providing an encoder disk, comprising; a signal track comprising a diffraction grating formed as a ring on the encoder disk; and an index track formed as a ring on the encoder disk, the index track comprising an index mark provided at an index angular coordinate; providing an illumination system structured to direct light to the encoder disk; providing a detector structured to detect light diffracted from the encoder disk, the detector comprising; two offset detectors structured to detect light diffracted from the signal track and output a quadrature signal; and an index detector structured to detect light reflected from the index track and output an index pulse; calculating an estimated state count kest of quadrature states from a rising edge of the index pulse to a middle of the index interval; calculating Qkest, wherein Qkest is the quadrature state at kest and corresponds to the quadrature state at an approximate center of the index pulse; and determining an offset correction. - View Dependent Claims (24, 25)
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26. A method of dynamically adjusting gain and offset in an optical encoder, the method comprising:
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providing an encoder disk comprising a diffraction grating; illuminating the encoder disk with light; providing a detector structured to detect light diffracted from the diffraction grating and output a first fine count channel; calculating a first target gain and first target offset for the first fine count channel; and applying a correction to data sampled from the first fine count channel based on the first target gain and first target offset. - View Dependent Claims (27, 28, 29, 30, 31, 32, 33, 34)
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Specification