A display device for displaying an image, the device comprising: an optical waveguide arrangement (10, 12) for directing image-bearing light, received from an image source over a range of angles relative to an injection axis, through the waveguide arrangement (10,12) for output to form a viewable image; and an input grating for diffracting into the waveguide arrangement (10, 12) the received image-bearing light such that all of the diffracted light is totally internally reflected within the waveguide arrangement (10, 12) and so that image bearing light output from the waveguide arrangement has a field of view corresponding to said range of angles, wherein the input grating is a surface relief grating for diffracting light over said range of angles into the waveguide arrangement (10, 12), the input grating having a profiled surface and a layered structure applied thereto comprising a layer of reflective material (36, 40) providing a reflective surface and at least one layer of dielectric material (34, 42), each of the reflective surface and the at least one layer of dielectric material being conformal in profile with said profiled surface and disposed such that the received image-bearing light interacts with both the at least one layer of dielectric material (34, 42) and the reflective surface, and wherein the thickness of the at least one layer of dielectric material (34, 42) with which the light interacts is selected to control the angular bandwidth of the input grating such that the image bearing light that is incident upon the input grating over said range of angles is diffracted into the waveguide arrangement (10, 12). an optical waveguide arrangement (10, 12) for directing image-bearing light, received from an image source over a range of angles relative to an injection axis, through the waveguide arrangement (10,12) for output to form a viewable image; and an input grating for diffracting into the waveguide arrangement (10, 12) the received image-bearing light such that all of the diffracted light is totally internally reflected within the waveguide arrangement (10, 12) and so that image bearing light output from the waveguide arrangement has a field of view corresponding to said range of angles, wherein the input grating is a surface relief grating for diffracting light over said range of angles into the waveguide arrangement (10, 12), the input grating having a profiled surface and a layered structure applied thereto comprising a layer of reflective material (36, 40) providing a reflective surface and at least one layer of dielectric material (34, 42), each of the reflective surface and the at least one layer of dielectric material being conformal in profile with said profiled surface and disposed such that the received image-bearing light interacts with both the at least one layer of dielectric material (34, 42) and the reflective surface, and wherein the thickness of the at least one layer of dielectric material (34, 42) with which the light interacts is selected to control the angular bandwidth of the input grating such that the image bearing light that is incident upon the input grating over said range of angles is diffracted into the waveguide arrangement (10, 12).