IMPROVEMENTS IN AND RELATING TO WAVEGUIDES

摘要

A waveguide for a display apparatus comprising a planar optical waveguide part (20) for guiding light to be displayed, an input diffraction grating (21) to diffract received light (7) along the optical waveguide part for guiding thereby, an intermediate diffraction grating (22) to receive diffracted light from the input diffraction grating and to expand the received light in a first dimension by diffraction (8), and an output diffraction grating (23) to receive the expanded light and to output the received expanded light (10) from the optical waveguide part by diffraction for display. The input diffraction grating is positioned so as to be located wholly within the geographical area of the intermediate grating, and the grating vectors of the input diffraction grating and the intermediate diffraction grating are oriented in different respective directions.