An optical system comprising: a lightguide having: a first external surface and a second external surface mutually parallel, and a first sequence of facets, at least a portion of which are: a plurality of parallel, partially reflecting, and polarization selective surfaces, at an oblique angle relative to said first and second external surfaces, and between said first and second external surfaces; a front-lit reflective polarization rotating image modulator: deployed to spatially modulate first polarized light coupled-out from said first external surface, outputting reflected second polarized light corresponding to an image, and deployed such that said reflected second polarized light traverses said lightguide from said first external surface via said first sequence of facets to said second external surface; an illumination source optically coupled to said lightguide to introduce light of at least said first polarization into said lightguide; wherein each of said facets of said first sequence of facets reflects at least a portion of said light and transmits a remaining portion of said light so that said light propagates by internal reflection at said first and second external surfaces, being progressively partially reflected by successive facets of said first sequence of facets towards said image modulator via the first external surface as said first polarized light, and wherein said facets of said first sequence of facets transmit said second polarized light; and a polarizer deployed to selectively transmit said second polarized light emerging from said second external surface of the lightguide. a lightguide having: a first external surface and a second external surface mutually parallel, and a first sequence of facets, at least a portion of which are: a plurality of parallel, partially reflecting, and polarization selective surfaces, at an oblique angle relative to said first and second external surfaces, and between said first and second external surfaces; a first external surface and a second external surface mutually parallel, and a first sequence of facets, at least a portion of which are: a plurality of parallel, partially reflecting, and polarization selective surfaces, at an oblique angle relative to said first and second external surfaces, and between said first and second external surfaces; a plurality of parallel, partially reflecting, and polarization selective surfaces, at an oblique angle relative to said first and second external surfaces, and between said first and second external surfaces; a front-lit reflective polarization rotating image modulator: deployed to spatially modulate first polarized light coupled-out from said first external surface, outputting reflected second polarized light corresponding to an image, and deployed such that said reflected second polarized light traverses said lightguide from said first external surface via said first sequence of facets to said second external surface; deployed to spatially modulate first polarized light coupled-out from said first external surface, outputting reflected second polarized light corresponding to an image, and deployed such that said reflected second polarized light traverses said lightguide from said first external surface via said first sequence of facets to said second external surface; an illumination source optically coupled to said lightguide to introduce light of at least said first polarization into said lightguide; wherein each of said facets of said first sequence of facets reflects at least a portion of said light and transmits a remaining portion of said light so that said light propagates by internal reflection at said first and second external surfaces, being progressively partially reflected by successive facets of said first sequence of facets towards said image modulator via the first external surface as said first polarized light, and wherein said facets of said first sequence of facets transmit said second polarized light; and a polarizer deployed to selectively transmit said second polarized light emerging from said second external surface of the lightguide.