Patent ID: 7060968

Claim:
An optical encoder for determining a location of an object, the optical encoder comprising: a scale having a pattern formed thereon, the pattern having a plurality of periods; means for relating motion between the scale and the object; means for illuminating the scale; means for forming an image of the pattern; means for detecting and outputting signals derived from a portion of the image of the pattern which lies within a field of view of the detector means, the field of view defining a fixed coordinate system; means for binning the signals from the detector means to define a binned image; and analyzing means, receiving the signals from the binning means for determining the location of the object, wherein the analyzing means: (i) finds, in accordance with the binned image, one of the plurality of periods within the field of view; (ii) identifies the one of the plurality of periods within the fixed coordinate system; and (iii) determines a coarse location of the object in accordance with the identity determined in (ii).