Optical system for a display

An optical system comprising:

• (a) an aperture-expanding lightguide optical element (LOE) having a pair of mutually parallel major surfaces, separated by a first thickness, said LOE supporting propagation of light by internal reflection at said major surfaces, said LOE having:
• (i) a first redirecting configuration deployed in a first region of said LOE for progressively redirecting light propagating in a first in-plane direction to propagate in a second in-plane direction towards a second region of the LOE, and
• (ii) a second redirecting configuration deployed in the second region of said LOE for progressively redirecting light propagating in the second in-plane direction out of the LOE for viewing by a viewer;
• and
• (b) a coupling-in arrangement comprising:
• (i) a coupling lightguide element (CLE) having a pair of mutually parallel surfaces separated by a second thickness that is no more than half of said first thickness, said parallel surfaces of said CLE having an area that is no more than 10 percent of an area of said major surfaces of said LOE, one of said surfaces of said CLE being bonded to one of said major surfaces of said LOE at an interface, at least part of said interface provided with a beam splitter coating having a reflectivity of at least 50%, and
• (ii) an input coupler deployed to couple light corresponding to a collimated image into said CLE.