Technological Evolution in Grating Encoders: A Review

As core components for ultra-precision positioning, grating encoders have technologically evolved toward higher accuracy, faster speeds, and multi-degree-of-freedom (multi-DOF) integration. This review systematically traces the technological progression of commercial grating encoders from imaging scanning to interferential scanning, from incremental to absolute encoding, and from single axis to multi-DOF integration. It compares the distinct technical strategies adopted by Heidenhain and Renishaw for robustness enhancement and absolute encoding within the imaging scanning paradigm. It also uncovers the physical mechanism of optical subdivision that allows interferential scanning encoders to surpass the sub-nanometer resolution barrier. Building upon this foundation, recent academic advances in multi-DOF interferometric measurement systems and Fizeau interferometer-based grating self-calibration methodologies are also reviewed.