There is provided an optical device, comprising a light-transmitting substrate having at least two major surfaces (26) parallel to each other; optical means (16) for coupling light waves located in a field-of-view into the substrate by internal reflection, and at least one partially reflecting surface (22) located in the substrate which is non-parallel to the major surfaces of the substrate, characterized in that at least one of the major surfaces is coated with a dichroic coating.