ABSOLUTE MOIRE TYPE POSITION ENCODER FOR USE IN A CONTROL SYSTEM

摘要

A two-dimensional Moiré type absolute position encoder (200) comprises a reticle (30) having spatially periodic transmission properties that vary according to a two dimensional incidence position of incident radiation. An imaging optical system (25) projects a plurality of radiation patterns onto reticle (30). The radiation that passes through reticle (30) is measured by radiation detector (23) and a controller (201) uses the electrical signals generated by detector (23) to determine the absolute position of reticle (30).