Compound Light-Guide Optical Elements

An optical system for directing image illumination injected at a coupling-in region towards a user for viewing, the optical system comprising a light-guide optical element (LOE) formed from transparent material, said LOE comprising:

• a. a first region containing a first set of planar, mutually-parallel, partially-reflecting surfaces having a first orientation;
• b. a second region containing a second set of planar, mutually-parallel, partially-reflecting surfaces having a second orientation non-parallel to said first orientation;
• c. a pair of mutually-parallel planar major external surfaces, said planar 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 planar major external surfaces,
• wherein said second set of partially-reflecting surfaces are at an oblique angle to said planar major external surfaces so that a part of image illumination propagating within said LOE by internal reflection at said planar major external surfaces from said first region into said second region is coupled out of said LOE towards the user, and wherein said first set of partially-reflecting surfaces are oriented so that a part of image illumination propagating within said LOE by internal reflection at said planar major external surfaces from said coupling-in region is deflected towards said second region,
• wherein said LOE has a thickness between said planar major external surfaces, and
• wherein said first set of partially-reflecting surfaces extend across at least 95 percent of said thickness, and said second set of partially-reflecting surfaces in said second region are contained within a subsection of said thickness spanning less than 95 percent of said thickness so that said second set of partially-reflecting surfaces are excluded from at least one surface layer of said second region.