An apparatus comprising: a light guiding element having a plurality of faces including first and second parallel faces, said light guiding element being configured for guiding rays of an image by internal reflection at said first and second parallel faces, one of said plurality of faces providing a coupling surface; a transparent optical element having an interface surface for attachment to said coupling surface, said transparent optical element being configured such that rays of an image propagating within said transparent optical element pass through said interface surface and said coupling surface so as to propagate within the light guiding element; a non-transparent coating applied to at least part of at least one of said plurality of faces of said light guiding element, said coating defining an edge adjacent to, or overlapping, said coupling surface of said light guiding element, wherein said coating defines an optical cutoff edge for rays of an image passing from said transparent optical element into said light guiding element, and in that said non-transparent coating is configured to generate internal reflection at an underlying region of said at least one face, wherein a quantity of transparent adhesive is deployed between said coupling surface and said interface surface so as to form an optically transmissive interface, said adhesive extending to, and overlapping, said optical cutoff edge, and wherein said coupling surface and said first parallel face meet at a ground edge, wherein said edge is non-overlapping with said ground edge, characterized in that said coupling surface is inclined relative to said first and second parallel faces, and wherein said adhesive fills a recess formed between said ground edge and said interface surface. a light guiding element having a plurality of faces including first and second parallel faces, said light guiding element being configured for guiding rays of an image by internal reflection at said first and second parallel faces, one of said plurality of faces providing a coupling surface; a transparent optical element having an interface surface for attachment to said coupling surface, said transparent optical element being configured such that rays of an image propagating within said transparent optical element pass through said interface surface and said coupling surface so as to propagate within the light guiding element; a non-transparent coating applied to at least part of at least one of said plurality of faces of said light guiding element, said coating defining an edge adjacent to, or overlapping, said coupling surface of said light guiding element, wherein said coating defines an optical cutoff edge for rays of an image passing from said transparent optical element into said light guiding element, and in that said non-transparent coating is configured to generate internal reflection at an underlying region of said at least one face, wherein a quantity of transparent adhesive is deployed between said coupling surface and said interface surface so as to form an optically transmissive interface, said adhesive extending to, and overlapping, said optical cutoff edge, and wherein said coupling surface and said first parallel face meet at a ground edge, wherein said edge is non-overlapping with said ground edge, characterized in that said coupling surface is inclined relative to said first and second parallel faces, and wherein said adhesive fills a recess formed between said ground edge and said interface surface.