Optical systems including light guide optical elements with two-dimensional magnification

Abstract

An optical system including a light guide optical element (LOE) for achieving optical aperture expansion is provided. [Solution] An optical system comprising a light guide optical element (LOE) having first and second sets (204, 206) of mutually parallel, partially reflective surfaces in different orientations. Both sets of partially reflective surfaces are located between parallel main external surfaces. A third set (202) of at least partially reflective surfaces, located in a coupling-in region, receives image illumination injected from a projector (2) through an optical aperture having a first in-plane width, and directs the image illumination toward a first set of partially reflective facets having an effective optical aperture having a second width greater than the first width, via reflection of at least a portion of the image illumination in the third set of at least partially reflective facets.

Claims

1. An optical system for directing image illumination injected in a coupling-in region toward a user for viewing, wherein the optical system includes a light guide optical element (LOE) formed from a transparent material, the LOE is (a) A first region comprising a first set of planar, mutually parallel partial reflective surfaces having a first orientation, (b) A second region including planar and mutually parallel partially reflective surfaces having a second orientation that is not parallel to the first orientation, (c) comprising one set of mutually parallel primary external surfaces, the primary external surfaces extending across the first and second regions such that both the first set of partial reflective surfaces and the second set of partial reflective surfaces are located between the primary external surfaces, The second set of partial reflective surfaces is inclined obliquely with respect to the main outer surface, so that a portion of the image illumination propagating within the LOE by internal reflection at the main outer surface from the first region to the second region is coupled out from the LOE toward the user, and the first set of partial reflective surfaces is such that a portion of the image illumination propagating within the LOE by internal reflection at the main outer surface from the coupling-in region is deflected toward the second region. The optical system further includes a third set of planar, mutually parallel, at least partially reflective surfaces arranged in the coupling-in region, wherein the arrangement of the third set of at least partially reflective surfaces receives image illumination injected from a projector through an optical aperture having a first width measured parallel to the main outer surface, and directs the image illumination, via reflection of at least a portion of the image illumination in the third set of at least partially reflective surfaces, toward the first set of partially reflective surfaces having an effective optical aperture having a second width measured parallel to the main outer surface, wherein the second width is greater than the first width.

2. The optical system according to claim 1, wherein the third set of at least partially reflective surfaces has a first sequence of continuously increasing reflectance in the order in which the image illumination reaches the at least partially reflective surfaces, and the first set of partially reflective surfaces has a second sequence of continuously increasing reflectance in the order in which the image illumination reaches the partially reflective surfaces, the second sequence beginning with a reflectance smaller than the last reflectance of the first sequence.

3. The optical system according to claim 2, wherein the final reflectance of the first sequence of continuously increasing reflectances is greater than 90%.

4. The optical system according to claim 1, wherein most of the image illumination directed toward the first set of partially reflective surfaces receives just one reflection from the third set of at least partially reflective surfaces.

5. The optical system according to claim 1, wherein most of the image illumination directed toward the first set of partially reflective surfaces receives two reflections from the third set of at least partially reflective surfaces.

6. The optical system according to claim 1, wherein the third set of at least partially reflective surfaces is integrated as part of the LOE and located between the main outer surfaces.

7. The optical system according to claim 6, wherein the third set of at least partially reflective surfaces is parallel to the first set of partially reflective surfaces.

8. The optical system according to claim 6, wherein the third set of at least partially reflective surfaces is not parallel to the first set of partially reflective surfaces.

9. The optical system according to claim 1, wherein the inter-surface spacing of the third set of at least partially reflective surfaces is smaller than the inter-surface spacing of the first set of partially reflective surfaces.

10. The optical system according to claim 1, wherein the surface area of ​​each of the third set of at least partially reflective surfaces is smaller than the surface area of ​​each of the first set of partially reflective surfaces.

11. The optical system according to claim 1, wherein the first region and the second region do not overlap.

12. The optical system according to claim 1, further comprising an image projector for projecting a collimated image having a field of view about the optical axis, wherein the image projector is optically coupled to the LOE to introduce a collimated image into the LOE as a propagated image propagated into the LOE by internal reflection at the main outer surface via a third set of at least partially reflective surfaces in the coupling-in region, the propagated image being partially reflected by a first set of partially reflective surfaces to generate a deflected propagated image propagated into the LOE by internal reflection at the main outer surface, and the deflected propagated image being partially reflected by a second set of partially reflective surfaces to generate a couple-out image directed outward from one of the main outer surfaces toward the user.

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