SURFACE RELIEF GRATING IN AN OPTICAL WAVEGUIDE HAVING A REFLECTING SURFACE AND DIELECTRIC LAYER CONFORMING TO THE SURFACE

摘要

The invention relates to a display device for displaying an image over a field of view. The device comprises: an optical arrangement for directing image bearing light from an image source so that the light has rays at a range of angles relative to an injection axis; and an optical waveguide having an input grating for diffracting into the waveguide said light over said range of angles such that all of the diffracted light is totally internally reflected within the waveguide and so that image bearing light output from the waveguide has a field of view corresponding to said range of angles, wherein the input grating is a surface relief grating having a profiled reflective surface and at least one layer of dielectric material conforming to the surface for diffracting light over said range of angles into the waveguide.