Patent ID: 6686585
Filing Date: 2004-02-03
Classification: G01D

Abstract:
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.