An optical encoder and method for measuring displacement information uses an encoder member that includes multiple optical tracks of diffractive optical regions having different periodicities with respect to consecutive identical diffractive optical regions to produce diffracted beams of light from at least one beam of light emitted from a light source. The diffracted beams of light are received at photodetectors, which produce electrical signals in response to the received beams of light. The electrical signals are related to the displacement information being measured.