Light-Guide Optical Element With Retarder for Polarization-Matched Expansion
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Solution Overview
Problem
Existing optical systems for near-eye displays suffer from light loss due to polarization mismatch between non-parallel facets, leading to inefficient image projection and non-uniform output.
Innovation Solution
Incorporating an optical retarder between sets of partially-reflecting surfaces within the light-guide optical element to rotate the polarization of light, ensuring consistent s-polarization across all facets, thereby optimizing reflectivity and image uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If non-parallel facets are used for two-dimensional image expansion, then the field of view and image size are improved, but light loss occurs due to polarization mismatch
Solution Approach 1:
A polarization compensator is introduced as an intermediary element between the first and second sets of non-parallel facets. This compensator actively manages the polarization state of light, rotating it to match the orientation required by subsequent facets, thereby preventing polarization mismatch losses while maintaining the benefits of non-parallel facet geometry for expanded field of view
Solution Approach 2:
The polarization state of light is dynamically adjusted by rotating the polarization angle as light propagates through different regions of the light-guide optical element. This parameter change ensures that the polarization orientation remains compatible with the local facet orientation at each stage of image expansion, eliminating reflectivity losses
2Illumination intensity
If non-parallel facets are used for two-dimensional image expansion, then image brightness is improved through multiple reflections, but polarization mismatch causes reduced reflectivity
Solution Approach 1:
The polarization compensator serves as a mediator that ensures consistent reflectivity across all facets by actively rotating the polarization state of incident light to match the optimal orientation for each facet set, thereby maintaining high and uniform reflectivity throughout the two-dimensional expansion process
Solution Approach 2:
The polarization rotation is performed in advance before light reaches each set of facets, preparing the light's polarization state to be optimally aligned with the upcoming facet orientation. This preliminary action prevents polarization mismatch from occurring in the first place, ensuring consistent reflectivity
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enhances light efficiency and uniformity in the projected image by maintaining consistent polarization, resulting in brighter and more uniform output images.
Implementation Method 1
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
Implementation Method 2
a part of image illumination propagating within the LOE by internal reflection at the major external surfaces
Data Source
AI summary
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.