Patent ID: 8492704

Claim:
An encoder for precisely indicating the position of a first member with respect to a second member, comprising: a pattern of machine-sensible elements carried on a single track of said first member; said machine-sensible elements being located at successive incremental locations on said single track of said first member and each representing one of the binary values “0” and “1”; and a plurality of “n” sensors, carried by said second member at a plurality of spaced locations thereon in proximity to said single track of said first member and alignable with said machine-sensible elements of said first member; characterized in that said pattern of machine-sensible elements is carried by a single track of said first member, and in that the number “n” of sensors carried by said second member is greater than “3”, such that each sensor senses the binary value of each machine-sensible element with which it is aligned to produce an output corresponding to the binary value of the machine-sensible element with which it is aligned, whereby the outputs of all the sensors constitute a binary code of “n” bits identifying the position of said first member with respect to said second member, and wherein said pattern of machine-sensible elements carried on said track of the first member, and the spacing of said sensors carried by said second member with respect to said track on the first member, are such that each incremental movement of said first member changes the binary value of only one of said bits of the binary numbers outputted by said sensors.