Position encoder with scale calibration
AssigneeMicroE Systems, Inc.
InventorsDonald L. Grimes, Stuart E. Schechter, Donald K. Mitchell
Life of this patent
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Abstract
There is provided a measurement system in which the calibration data is easily incorporated into or obtained by the position sensing and/or displacement sensing system's processing unit. A scale-based encoder has a signal processor that corrects for scale inaccuracy based on a limited set of correction coefficients. The correction coefficients are the slopes and offsets that define a piecewise linear correction curve corresponding to the errors inherent in the scale. Several ways for communicating the coefficients to the processor are envisioned. Correction is applicable to linear or rotary encoders.
Claims48
A device for detecting relative movement and correcting for scale inaccuracy, comprising:
- (A) an optical scale relatively movable with respect to a source, having a periodic array of alternating regions with a detectable optical property;
- (B) a periodic detector having a sensing region positioned thereon, positioned relative to the scale to detect the detectable property, wherein the periodic detector detects and transmits a measure of displacement of the scale in response to a movement of the scale;
- and
- C) a processor, operatively connected to the periodic detector, receiving the measure of displacement from the periodic detector, receiving calibration data corresponding to the scale indicative of a linear piecewise approximation correlating to the scale, the piecewise approximation including a plurality of segments, each of the segments corresponding to a portion of the scale, the calibration data including information a location on the scale of each segment and information defining the slope of each segment;
- and converting the measure of displacement into a calibrated displacement using the calibration data.
A method of detecting relative movement and correcting for scale inaccuracy, comprising the steps of:
- (A) providing an optical scale relatively movable with respect to a source, having a periodic array of alternating regions with a detectable optical property;
- (B) providing a periodic detector having a sensing region positioned thereon, positioned relative to the scale to detect the detectable property, wherein the periodic detector detects and transmits a measure of displacement of the scale in response to a movement of the scale;
- (C) providing calibration data indicative of a linear piecewise approximation correlating to the scale, the piecewise approximation including a plurality of segments, each of the segments corresponding to a portion of the scale, the calibration data including information defining a location on the scale of each segment and information defining the slope of each segment;
- and
- (D) receiving in a processor operatively connected to the periodic detector, the measure of displacement from the periodic detector, receiving calibration data corresponding to the scale, and converting the measure of displacement into a calibrated displacement using the calibration data.
Dependencies are inferred from the claim text.