Optical systems including light-guide optical elements with two-dimensional expansion

An optical system for directing image illumination from an image projector towards a user for viewing, the optical system comprising:

• (a) an image projector for projecting a collimated image having an angular field of view about an optical axis, said collimated image having a projector optical aperture;
• (b) a light-guide optical element (LOE) formed from transparent material, said LOE comprising:
• (i) a first region containing a first set of planar, mutually-parallel, partially-reflecting surfaces having a first orientation;
• (ii) a second region containing a second set of planar, mutually-parallel, partially-reflecting surfaces having a second orientation non-parallel to said first orientation;
• (iii) a set of mutually-parallel major external surfaces, said major external surfaces extending across said first and second regions such that both said first set of partially-reflecting surfaces and said second set of partially-reflecting surfaces are located between said major external surfaces;
• and
• (iv) a coupling-in surface having a coupling-in optical aperture, said coupling-in surface being positioned such that a collimated image introduced via said coupling-in surface propagates within said LOE by internal reflection at said major external surfaces, is partially reflected by said first set of partially-reflecting surfaces to generate a deflected propagating image propagating within said LOE by internal reflection at said major external surfaces, and is partially reflected by said second set of partially-reflecting surfaces to generate a coupled-out image directed outwards from one of said major external surfaces towards the user,
• wherein said coupling-in optical aperture has at least one dimension larger than a corresponding dimension of said projector optical aperture, and wherein said image projector is associated with said coupling-in surface via an aperture expanding arrangement comprising a third set of planar, mutually-parallel, at least partially-reflecting surfaces deployed between said image projector and said coupling-in surface, said aperture expanding arrangement expanding an effective optical aperture of said image projector by specular reflection at successive surfaces of said third set of partially-reflecting surfaces to fill said coupling-in optical aperture.