A display has an image projector projecting collimated image illumination along a projection direction, and an optical element having two major surfaces and containing partially reflective surfaces which are internal to the optical element, planar, mutually parallel and overlapping relative to the projection direction. Each ray of the collimated image illumination enters the optical element and is partially reflected by at least two of the partially reflective surfaces so as to be redirected to exit the first major surface along a viewing direction. An alternative implementation, a first reflection from one of the partially reflective surfaces redirects part of the image illumination rays so as to undergo total internal reflection at the major surfaces of the optical element. The rays are then redirected by further reflection from another of the partially reflective surfaces to exit the optical element along the viewing direction.