An absolute encoder device comprises a code plate having a 1-track type absolute pattern whose minimum reading unit length is .lambda., a first incremental pattern with a pitch .lambda., and a second incremental pattern with pitch 2.sup.-n .lambda.. The device also comprises a detector section, which...http://www.google.de/patents/US5252825?utm_source=gb-gplus-sharePatent US5252825 - Absolute encoder using interpolation to obtain high resolution
