US-12619023-B2 - Optical systems including light-guide optical elements for two-dimensional expansion with retarder element

Abstract

An optical system for directing image illumination injected at a coupling-in region to an eye-motion box for viewing by an eye of a user, including a light-guide optical element (LOE) formed from transparent material that includes: a first region containing a first set of planar, mutually-parallel, partially-reflecting surfaces having a first orientation; a second region containing a second set of planar, mutually-parallel, partially-reflecting surfaces having a second orientation non-parallel to the first orientation; a set of mutually-parallel major external surfaces extending across the first and second regions, and an optical retarder deployed between the first region and the second region so as to rotate a polarization of light deflected by the first set of partially-reflecting surfaces prior to reaching the second set of partially-reflecting surfaces.

Inventors

• Ronen CHRIKI
• Elad Sharlin
• Tsion EISENFELD
• Shimon GRABARNIK

Assignees

• LUMUS LTD.

Dates

Publication Date

20260505

Application Date

20210920

Claims (17)

1. 1 . An optical system for directing image illumination injected at a coupling-in region to an eye-motion box for viewing by an eye of a user, the optical system comprising a light-guide optical element (LOE) formed from transparent material, said LOE comprising: a pair of mutually-parallel major surfaces supporting propagation of image illumination within said LOE by internal reflection at said major surfaces; a first set of planar, mutually-parallel, partially-reflecting surfaces located between said major surfaces in a first region of said LOE, said first set of partially-reflecting surfaces having a first orientation; a second set of planar, mutually-parallel, partially-reflecting surfaces located between said major surfaces in a second region of said LOE, said second set of partially-reflecting surfaces having a second orientation non-parallel to said first orientation, wherein said pair of major surfaces extend continuously across said first and second regions of said LOE without any intervening air gap, wherein said second set of partially-reflecting surfaces are at an oblique angle to said major surfaces so that a part of image illumination propagating within said LOE by internal reflection at said major surfaces from said first region into said second region is coupled out of said LOE towards the eye-motion box, and wherein said first set of partially-reflecting surfaces are oriented so that a part of image illumination propagating within said LOE by internal reflection at said major surfaces from said coupling-in region is deflected towards said second region, said LOE further comprising an optical retarder deployed between said first region and said second region so that image illumination of a first polarization state deflected by said first set of partially-reflecting surfaces is rotated to a second polarization state prior to first incidence on said second set of partially-reflecting surfaces, the image illumination remaining substantially in said second polarization state for incidence on successive surfaces of said second set of partially-reflecting surfaces.
2. 2 . The optical system of claim 1 , further comprising a compact image projector (POD) optically coupled to the LOE so as to inject the image illumination into the coupling-in region of the LOE such that the image illumination with said first polarization state becomes trapped in one dimension by internal reflection at said pair of major surfaces.
3. 3 . The optical system of claim 2 , wherein the POD is configured to generate a collimated image, collimated to infinity, such that the image illumination spans a range of angles corresponding to an angular field of view in two dimensions.
4. 4 . The optical system of claim 1 , wherein the first set of partially-reflecting surfaces are oriented orthogonal to said major surfaces of the LOE.
5. 5 . The optical system of claim 4 , wherein both the image illumination and a conjugate of the image illumination are deflected into the second region.
6. 6 . The optical system of claim 1 , wherein the first set of partially-reflecting surfaces are oriented obliquely to said major surfaces of the LOE.
7. 7 . The optical system of claim 6 , wherein either the image illumination or a conjugate of the image illumination is deflected into the second region.
8. 8 . The optical system of claim 1 , wherein the first set of partially-reflecting surfaces successively reflect a proportion of the image illumination propagating within said first region such that the image illumination undergoes expansion in a first dimension.
9. 9 . The optical system of claim 1 , wherein the second set of partially-reflecting surfaces successively reflect a proportion of the image illumination propagating within said second region such that the image illumination undergoes expansion in a second dimension.
10. 10 . The optical system of claim 1 , wherein the first region is configured to achieve aperture expansion in one of an x-axis or y-axis direction, and the second region is configured to achieve aperture expansion in the other one of the x-axis or y-axis direction.
11. 11 . The optical system of claim 1 , wherein the first and second set of partially-reflecting surfaces are implemented as internal surfaces coated with dielectric thin film coatings configured to reflect light that impinges on said internal surfaces over a predetermined range of angles.
12. 12 . The optical system of claim 1 , wherein the retarder is deployed within the LOE such that the retarder extends between the major surfaces substantially perpendicular to said major surfaces.
13. 13 . The optical system of claim 1 , wherein the retarder is deployed within the LOE such that the retarder extends between the major surfaces at an oblique angle relative to said major surfaces.
14. 14 . The optical system of claim 1 , wherein the retarder is deployed within the LOE such that the retarder is oriented substantially parallel to said major surfaces.
15. 15 . The optical system of claim 14 , wherein the retarder is oriented substantially adjacent to one of said major surfaces.
16. 16 . The optical system of claim 2 , wherein said first polarization state is substantially s-polarized relative to said first set of partially-reflecting surfaces and said second polarization state is substantially s-polarized relative to said second set of partially-reflecting surfaces.
17. 17 . An optical system for directing image illumination injected at a coupling-in region to an eye-motion box for viewing by an eye of a user, the optical system comprising a light-guide optical element (LOE) formed from transparent material, said LOE comprising: a pair of mutually-parallel major surfaces supporting propagation of image illumination within said LOE by internal reflection at said major surfaces; a first set of planar, mutually-parallel, partially-reflecting surfaces located between said major surfaces in a first region of said LOE, said first set of partially-reflecting surfaces having a first orientation; a second set of planar, mutually-parallel, partially-reflecting surfaces located between said major surfaces in a second region of said LOE, said second set of partially-reflecting surfaces having a second orientation non-parallel to said first orientation, wherein said pair of major surfaces extend continuously across said first and second regions of said LOE without any intervening air gap, wherein said second set of partially-reflecting surfaces are at an oblique angle to said major surfaces so that a part of image illumination propagating within said LOE by internal reflection at said major surfaces from said first region into said second region is coupled out of said LOE towards the eye-motion box, and wherein said first set of partially-reflecting surfaces are oriented so that a part of image illumination propagating within said LOE by internal reflection at said major surfaces from said coupling-in region is deflected towards said second region, said deflection being a sole redirection of an in-plane component of a propagation direction of the image illumination occurring between the coupling-in region and the second region of said LOE, said LOE further comprising an optical retarder deployed between said first region and said second region so that image illumination of a first polarization state deflected by said first set of partially-reflecting surfaces is rotated to a second polarization state prior to first incidence on said second set of partially-reflecting surfaces, the image illumination remaining substantially in said second polarization state for incidence on successive surfaces of said second set of partially-reflecting surfaces.

Description

TECHNICAL FIELD The presently disclosed subject matter relates to optical systems, and, more particularly, to optical systems that include light-guide optical elements (LOE) configured for two-dimensional image expansion. BACKGROUND Recent years have seen an influx in consumer demand for head mounted displays (HMD) and “smart” eye-wear such as augmented reality (AR) glasses, collectively referred to herein as near eye display systems. Accordingly, in this rapidly developing area of technology there is a growing need for optical systems that are more compact and light weight, and yet still provide a relatively large field of view (FOV) and produce bright, high quality images. Some of the known optical systems employ a waveguide (also referred to herein as “light guide”, “light-guide optical element” or “LOE”) to expand an input image by propagating the image along a substrate in which is embedded one or more sets of partially reflective internal surfaces (“facets”). One of the known problems with this type of optical system is the loss of small amounts of light due to polarization mismatch between partial reflections from non-parallel facets. GENERAL DESCRIPTION According to one aspect of the presently disclosed subject matter there is provided an optical system for directing image illumination injected at a coupling-in region to an eye-motion box for viewing by an eye of a user, the optical system including a light-guide optical element (LOE) formed from transparent material, the LOE including: a first region containing a first set of planar, mutually-parallel, partially-reflecting surfaces having a first orientation; a second region containing a second set of planar, mutually-parallel, partially-reflecting surfaces having a second orientation non-parallel to the first orientation; a set of mutually-parallel major external surfaces, the major external surfaces extending across the first and second regions such that both the first set of partially-reflecting surfaces and the second set of partially-reflecting surfaces are located between the major external surfaces, wherein the second set of partially-reflecting surfaces are at an oblique angle to the major external surfaces so that a part of image illumination propagating within the LOE by internal reflection at the major external surfaces from the first region into the second region is coupled out of the LOE towards the eye-motion box, and wherein the first set of partially-reflecting surfaces are oriented so that a part of image illumination propagating within the LOE by internal reflection at the major external surfaces from the coupling-in region is deflected towards the second region, the LOE further including an optical retarder deployed between the first region and the second region so as to rotate a polarization of light deflected by the first set of partially-reflecting surfaces prior to reaching the second set of partially-reflecting surfaces. According to some aspects, the optical system includes a compact image projector (POD) optically coupled to the LOE so as to inject the image illumination into the coupling-in region of the LOE such that the image illumination becomes trapped in one dimension by internal reflection at the set of major external surfaces. According to some aspects, the POD is configured to generate a collimated image, collimated to infinity, such that the image illumination spans a range of angles corresponding to an angular field of view in two dimensions. According to some aspects, the first set of partially-reflecting surfaces are oriented orthogonal to the major external surfaces of the LOE. According to some aspects, both the image illumination and a conjugate of the image illumination are deflected into the second region. According to some aspects, the first set of partially-reflecting surfaces are oriented obliquely to the major external surfaces of the LOE. According to some aspects, either the image illumination or a conjugate of the image illumination is deflected into the second region. According to some aspects, the first set of partially-reflecting surfaces successively reflect a proportion of the image illumination propagating within the first region such that the image illumination undergoes expansion in a first dimension. According to some aspects, the second set of partially-reflecting surfaces successively reflect a proportion of the image illumination propagating within the second region such that the image illumination undergoes expansion in a second dimension. According to some aspects, the first region is configured to achieve aperture expansion in one of an x-axis or y-axis direction, and the second region is configured to achieve aperture expansion in the other one of the x-axis or y-axis direction. According to some aspects, the first and second set of partially-reflecting surfaces are implemented as internal surfaces coated with dielectric thin film coatings configured to reflect light that impinges o