Patent ID: 6157188
Filing Date: 2000-12-05
Classification: G01B,G01D,H03M

Abstract:
An absolute position transducer, comprising:a scale member;a read head member, the read head member and the scale member movable relative to each other along a measuring axis;a code track position transducer providing an output that defines a position of the read head relative to the scale member to a first resolution, comprising:at least one set of code track sensors formed on the read head member, each set of code track sensors including a number N of sensors, where N is a positive integer greater than 1, anda code track formed on the scale member, the code track having a plurality of zones distributed along the measuring axis, at least one sensible element formed in at least some of the plurality of zones;an intermediate position transducer device that provides a continuously varying output that defines a position of the read head relative to the scale member to a second resolution finer than the first resolution, the continuously varying output varying periodically over an intermediate wavelength, the intermediate position transducer device comprising at least one position transducer formed on the read head and scale member; anda signal processing circuit electrically connected to each set of code track sensors and the at least one position transducer;wherein:the sensible elements modulate an output of the sensors of each set of code track sensors based on a relative position between the read head member and the scale member;the sensible elements are distributed on the scale member such that each zone is capable of producing one of a set of output states in an overlying sensor, the zones forming a series of code elements extending along the measuring axis, the code elements arranged into blocks of n code elements forming a code word; andeach intermediate wavelength coinciding with a set of m identical blocks of n code elements, where m is an integer at least equal to one.