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Indexed optical encoder, method for indexing an optical encoder, and method for dynamically adjusting gain and offset in an optical encoder

  • US 8,476,579 B2
  • Filed: 10/19/2012
  • Issued: 07/02/2013
  • Est. Priority Date: 08/28/2008
  • Status: Active Grant
First Claim
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1. A method of dynamically adjusting gain and offset in an optical encoder, the method comprising:

  • 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;

    wherein calculating the first target gain and the first target offset includes;

    determining a minimum value and maximum value in a set of data from the first fine count channel;

    calculating a moving average minimum based on the minimum value and minimum values from a plurality of prior sets of data from the first fine count channel;

    calculating a moving average maximum based on the maximum value and maximum values from the plurality of prior sets of data from the first fine count channel;

    calculating the first target gain according to the equation Gcal=(ave_maxA

    ave_minA)/2, where Gcal is the first target gain, ave_maxA is the moving average maximum, and ave_minA is the moving average minimum; and

    calculating the first target offset according to the equation OFFSETcal=(ave_maxA+ave_minA)/2, where OFFSETcal is the first target offset.

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