High resolution optical coder for precise determination of the angle of rotation of an axle where the coder disk has three coaxial paths of markings towards its outer edge that use receivers and diffracted light for measurement

摘要

High resolution optical coder has a disk (1) mounted on an axis (2) for which it is required to measure the angle of rotation. The disk includes three concentric paths (10,11) of markings of fixed width. Light beams are aimed at the disk to pass through the markings so that they are diffracted and then the diffracted light detected by receivers, converted to digital signals and analyzed. The coder comprises a first group of receivers that receives light diffracted from the first, so called fine marking path (10). A second group of receivers receive light diffracted by the neighboring paths (11) where the markings have a width 2N times greater than the width of the fine path markings. N is positive and greater than zero. The markings of one neighboring path (11) are displaced by a half period with respect to the other. The signal produced and analyzed by the first receiver associated with the fine path is corrected by processing signals from at least a pair of the first group of receivers.