An optical device, comprising: a light-transmitting substrate having at least two major surfaces and edges; at least one partially reflecting surface (22a, 22b) located between the two major surfaces of the light-transmitting substrate for partially reflecting light waves out of the substrate; a transparent plate, having at least two major surfaces and edges, at least one partially reflecting surface (222a, 222b) located between the two major surfaces of the transparent plate for partially reflecting light waves out of the transparent plate; one of the major surfaces of the transparent plate being optically attached to a major surface of the light-transmitting substrate defining an interface plane (167, 210), characterized in that the device further comprises an optical element (16, 230) for coupling light waves into the light-transmitting substrate by total internal reflection, a beam-splitting coating is applied at the interface plane (167, 210) between the substrate and the transparent plate, such that said light-transmitting substrate and said first transparent plate form at least part of a light-guide optical element having an upper major surface, a lower major surface and the interface plane (167, 210), wherein light waves coupled inside the light-transmitting substrate and the transparent plate are partially reflected from the interface plane (167, 210) and partially pass therethrough and wherein the light waves undergo a plurality of total internal reflections off the upper major surface and the lower major surface, wherein said upper major surface, said lower major surface and said internal partially reflecting interface plane (167, 210) are all parallel to each other, and wherein said at least one partially reflecting surface (22a, 22b) located between the two major surfaces of the light-transmitting substrate is parallel to and oriented at exactly the same orientation as said at least one partially reflecting surface (222a, 222b) located between the two major surfaces of the transparent plate. a light-transmitting substrate having at least two major surfaces and edges; at least one partially reflecting surface (22a, 22b) located between the two major surfaces of the light-transmitting substrate for partially reflecting light waves out of the substrate; a transparent plate, having at least two major surfaces and edges, at least one partially reflecting surface (222a, 222b) located between the two major surfaces of the transparent plate for partially reflecting light waves out of the transparent plate; one of the major surfaces of the transparent plate being optically attached to a major surface of the light-transmitting substrate defining an interface plane (167, 210), characterized in that the device further comprises an optical element (16, 230) for coupling light waves into the light-transmitting substrate by total internal reflection, a beam-splitting coating is applied at the interface plane (167, 210) between the substrate and the transparent plate, such that said light-transmitting substrate and said first transparent plate form at least part of a light-guide optical element having an upper major surface, a lower major surface and the interface plane (167, 210), wherein light waves coupled inside the light-transmitting substrate and the transparent plate are partially reflected from the interface plane (167, 210) and partially pass therethrough and wherein the light waves undergo a plurality of total internal reflections off the upper major surface and the lower major surface, wherein said upper major surface, said lower major surface and said internal partially reflecting interface plane (167, 210) are all parallel to each other, and wherein said at least one partially reflecting surface (22a, 22b) located between the two major surfaces of the light-transmitting substrate is parallel to and oriented at exactly the same orientation as said at least one partially reflecting surface (222a, 222b) located between the two major surfaces of the transparent plate.