Highly efficient compact head-mounted display system

An optical device, comprising:

• an input aperture;
• an output aperture;
• at least a first and a second light-transmitting substrate, having refractive indices and each having at least two parallel major surfaces and edges;
• a first and a second coupling-in element for coupling light waves characterized by an angular range into the first and the second light-transmitting substrate, respectively, to effect total internal reflection;
• at least a first and a second reflecting surface located between the two major surfaces of the first light-transmitting substrate for coupling light waves out of the first light-transmitting substrate, and
• at least a third and a fourth reflecting surface located between the two major surfaces of the second light-transmitting substrate for coupling light waves out of the second light-transmitting substrate,
• wherein the angular range of the light waves incident on the first coupling-in element comprising at least a first, a second, and a third angular segment, the first and the third reflecting surfaces are angular sensitive surfaces, the first reflecting surface is substantially total reflective for the first angular segment and substantially transparent for the second and the third angular segments, the third reflecting surface is substantially total reflective for the first and the second angular segments and substantially transparent for the third angular segment, and the second and the fourth reflecting surfaces are substantially total reflective for the second and the third angular segments.