Aperture multiplier using a rectangular waveguide
An optical aperture multiplier includes a first optical waveguide ( 10 ) having a rectangular cross-section and including partially reflecting surfaces ( 40 ) at an oblique angle to a direction of elongation of the waveguide. A second optical waveguide ( 20 ), also including partially reflecting surfaces ( 45 ) at an oblique angle, is optically coupled with the first optical waveguide ( 10 ). An image coupled into the first optical waveguide with an initial direction of propagation at an oblique coupling angle advances by four-fold internal reflection along the first optical waveguide, with a proportion of intensity of the image reflected at the partially reflecting surfaces so as to be coupled into the second optical waveguide, and then propagates through two-fold reflection within the second optical waveguide, with a proportion of intensity of the image reflected at the partially reflecting surfaces so as to be directed outwards from one of the parallel faces as a visible image.
1. An optical arrangement comprising:
(a) an optical waveguide having at least a first pair of parallel faces for conveying an image via total internal reflection; and
(b) an image projecting arrangement optically coupled to said optical waveguide for introducing into said optical waveguide a collimated image, said image projecting arrangement comprising a polarized beam splitter prism having:
(i) an image input surface;
(ii) a collimating optical element deployed on a second surface substantially perpendicular to said image input surface; and
(iii) a polarized beam splitter deployed on a diagonal plane so as to direct image illumination from said image input surface towards said collimating optical element,
said polarized beam splitter prism being optically coupled to said optical waveguide with said image input surface and said second surface tilted relative to said first pair of parallel faces, said polarized beam splitter prism further comprising a modified bottom face lying on a side of said polarized beam splitter away from said collimating optical element and forming a continuation of a first of said first pair of parallel faces.
2. The optical arrangement of claim 1 , wherein at least part of said modified bottom face lies within a cuboid defined by said image input surface and said second surface.
3. The optical arrangement of claim 1 , wherein said polarized beam splitter prism is optically coupled to said waveguide via a coupling prism, and wherein said coupling prism provides an external surface coplanar with, and bridging between, said modified bottom face and said first of said first pair of parallel faces.
4. The optical arrangement of claim 1 , further comprising an image projecting source optically coupled to said image input surface so as to project an image into said polarized beam splitter prism, said image projecting source and said collimating optical element defining an angular field of view for rays of a collimated image projected from said collimating optical element, wherein a second of said first pair of parallel faces terminates at an edge, and wherein said first of said first pair of parallel faces and said modified bottom face together form an extended surface extending sufficiently that said edge is illuminated by rays of said collimated image of all angles within said angular field of view after reflection at said extended surface.
5. The optical arrangement of claim 1 , wherein said optical waveguide further comprises a second pair of parallel faces so that said optical waveguide conveys an image via four-fold internal reflection, said image input surface and said second surface being tilted relative to both said first and said second pairs of parallel faces, and wherein said polarized beam splitter prism further comprises a second modified bottom face lying on a side of said polarized beam splitter away from said collimating optical element and forming a continuation of one of said second pair of parallel faces.
6. The optical arrangement of claim 5 , wherein at least part of said modified bottom face and at least part of said second modified bottom face lie within a cuboid defined by said image input surface and said second surface.
7. The optical arrangement of claim 5 , wherein said polarized beam splitter prism is optically coupled to said waveguide via a coupling prism, and wherein said coupling prism provides a first external surface coplanar with, and bridging between, said modified bottom face and said first of said first pair of parallel faces, and a second external surface coplanar with, and bridging between, said second modified bottom face and said first of said second pair of parallel faces.
8. The optical arrangement of claim 5 , further comprising an image projecting source optically coupled to said image input surface so as to project an image into said polarized beam splitter prism, said image projecting source and said collimating optical element defining an angular field of view for rays of a collimated image projected from said collimating optical element, wherein a second of said first pair of parallel faces terminates at a first edge and a second of said second pair of parallel faces terminates at a second edge, and wherein said first of said first pair of parallel faces and said modified bottom face together form a first extended surface extending sufficiently that said first edge is illuminated by rays of said collimated image of all angles within said angular field of view after reflection at said first extended surface, and wherein said first of said second pair of parallel faces and said second modified bottom face together form a second extended surface extending sufficiently that said second edge is illuminated by rays of said collimated image of all angles within said angular field of view after reflection at said second extended surface.