Patent ID: 7262714

Claim:
An encoder comprising: a detector; an optical system for generating an image of a code strip on said detector, said image comprising a plurality of light and dark stripes, said detector generating a plurality of sinusoidal signals differing in phase from one another as said code strip moves relative to said detector, each sinusoidal signal cycling through one period and only one period when said code strip moves a distance equal to one light stripe and one dark stripe with respect to said detector, wherein said detector generates said plurality of sinusoidal signals from said image of said light and dark stripes as said image moves over said detector; a frequency multiplier that generates a plurality of frequency multiplied signals, each frequency multiplied signal corresponding to one of said sinusoidal signals and having a frequency that is an integer multiple of that corresponding sinusoidal signal, said integer multiple being greater than 1; and a signal interpolator that defines a plurality of position locations utilizing said frequency multiplied signals, there being at least 5 said position locations corresponding to said code strip moving a distance equal to one light stripe and one dark stripe with respect to said detector.