An optical shaft resolver using coupled light-modulators

An experimental, optical shaft resolver is described which uses continuously rotating radial gratings to form two light modulators. Angular position is determined as the phase difference between the signals from the fixed reference modulator and the variable position modulator. 360 line gratings are used, each line interval being divided into 200 parts by conventional equipment. The method is able to average centring and manufacturing errors, thus reducing production tolerances.