Optical system having prism between polarizing beam splitter and lightguide

An optical system comprising:

• (a) a lightguide having a pair of parallel major surfaces supporting propagation of image light by internal reflection at the major surfaces, said lightguide having a lightguide entrance;
• (b) an image projecting arrangement for generating a collimated image for introduction into said lightguide, said image projecting arrangement comprising:
• (i) first, second and third micro-LED arrays configured for generating, respectively, images of first, second and third colors,
• (ii) a dichroic combiner having first, second and third input surfaces supporting, respectively, said first, second and third micro-LED arrays, said dichroic combiner including a first diagonally deployed dichroic reflector, selectively reflective for the first color and transmissive for the second color and the third color, and a second diagonally-deployed dichroic reflector, selectively reflective for the third color and transmissive for the second color,
• (iii) a polarizing-beam-splitter prism, associated with said dichroic combiner, having a diagonal polarizing beam splitter surface, and
• (iv) reflective collimating optics associated with a face of said polarizing-beam-splitter prism and deployed to collimate image light from said first, second and third micro-LED arrays that was combined by said dichroic combiner and reflected by said polarizing beam splitter surface, said reflective collimating optics having a principal plane and an optical axis;
• and
• (c) a coupling prism between said polarizing beam splitter surface and said lightguide entrance, said coupling prism providing a coupling surface that is coplanar with, or parallel to, one of said parallel major surfaces,
• wherein said lightguide and said coupling surface are inclined relative to said optical axis so that the collimated image from said reflective collimating optics passing through said polarizing beam splitter surface enters said lightguide entrance, partly directly and partly after reflection from said coupling surface, at angles undergoing internal reflection within said lightguide,
• and wherein a reference length RL is defined as a distance along said optical axis from said principal plane to said polarizing beam splitter surface, a light path from said principal plane to said lightguide entrance having a length less than 3×RL.