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Abstract

An optical encoding system for determing the absolute and the incremental positions of a movable member relative to a stationary member. For example, three stationary light sources may be supported by the stationary member for emitting three narrow light beams on respective paths. An encoding band may be supported by the movable member in the paths of the light beams. The band has a timing and incremental encoding track comprising at least one series of alternating light-blocking stripes and light-passing stripes, and a data track comprising a series of distinct absolute position tags. A read head may be supported by the stationary member and has three optical sensors, one for each light beam, two preferably in quadrature with each other for the timing and incremental encoding track, and one for the data track. Each optical sensor includes light sensors for generating an analog signal voltage. A decoding system actuated by these analog signal voltages determines the incremental and absolute position of the movable member relative to the stationary member.

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First Claim