An optical device, comprising: a light waves-transmitting substrate (20, 150) having at least two major surfaces and edges; optical means for coupling light waves into the substrate (20, 150) by total internal reflection; a plurality of partially reflecting surfaces located at a distance from each other and carried internally within the substrate (20, 150), wherein the partially reflecting surfaces are parallel to each other and not parallel to any of the edges of the substrate (20, 150) but located at an oblique angle to the major surfaces of the substrate (20, 150), characterized in at least two of the partially reflecting surfaces being anisotropic, each anisotropic surface (22a, 22b) having a major axis (42, 80, 90) parallel to the surface plane, the reflection and transmission properties of the surface substantially depending on the orientation of the polarization of the incident light in relation to the major axis (42, 80, 90) of the surface, the anisotropic surfaces (22a, 22b) being mounted with the major axis (42, 80, 90) in different directions, wherein light waves coupled into the substrate (20, 150) pass through a first partially reflecting surface of the at least two anisotropic surfaces (22a, 22b) three times at different positions and directions, the passing ray having p polarization each time, the coupled light waves being partially reflected out of the substrate (20, 150) by the first partially reflecting surface, the major axis (42, 80, 90) of which is oriented to reflect s-polarized light waves, and by a second partially reflecting surface of the at least two anisotropic surfaces (22a, 22b), the major axis (42, 80, 90) of which is oriented to reflect p-polarized light waves. a light waves-transmitting substrate (20, 150) having at least two major surfaces and edges; optical means for coupling light waves into the substrate (20, 150) by total internal reflection; a plurality of partially reflecting surfaces located at a distance from each other and carried internally within the substrate (20, 150), wherein the partially reflecting surfaces are parallel to each other and not parallel to any of the edges of the substrate (20, 150) but located at an oblique angle to the major surfaces of the substrate (20, 150), characterized in at least two of the partially reflecting surfaces being anisotropic, each anisotropic surface (22a, 22b) having a major axis (42, 80, 90) parallel to the surface plane, the reflection and transmission properties of the surface substantially depending on the orientation of the polarization of the incident light in relation to the major axis (42, 80, 90) of the surface, the anisotropic surfaces (22a, 22b) being mounted with the major axis (42, 80, 90) in different directions, wherein light waves coupled into the substrate (20, 150) pass through a first partially reflecting surface of the at least two anisotropic surfaces (22a, 22b) three times at different positions and directions, the passing ray having p polarization each time, the coupled light waves being partially reflected out of the substrate (20, 150) by the first partially reflecting surface, the major axis (42, 80, 90) of which is oriented to reflect s-polarized light waves, and by a second partially reflecting surface of the at least two anisotropic surfaces (22a, 22b), the major axis (42, 80, 90) of which is oriented to reflect p-polarized light waves.