Freeform Nanostructured Surface for AR/VR Near-Eye Display
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Solution Overview
Problem
Conventional near-eye displays face challenges in providing wide field of view and efficient diffraction of image light, especially with optical aberrations induced by tilting and decentering of reflective surfaces, and limited efficiency in transverse electric polarized light across the visible spectrum.
Innovation Solution
Incorporation of a freeform nanostructured surface with a meta-grating on the combiner and secondary mirror, featuring a unit cell with meta-atoms of varying length-to-width ratios, which corrects optical aberrations and achieves high diffraction efficiency of at least 50% for transverse electric polarized light across a wide angle of incidence in the visible spectrum.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional reflective surfaces are used in near-eye displays, then the device structure is simple, but optical aberrations are induced by tilting and decentering that degrade image quality
Solution Approach 1:
The patent applies freeform surface technology that modifies the geometric parameters of the reflective surface, transforming it from a conventional flat or simple curved surface to a complex freeform surface with specific mathematical descriptions. This parameter change enables the surface to correct optical aberrations while maintaining structural integration
Solution Approach 2:
The freeform reflective surface introduces asymmetric geometric characteristics to correct the symmetric optical aberrations caused by tilted and decentered optical paths in near-eye displays. The asymmetric surface profile compensates for the asymmetric distortion in the optical system
2Device complexity
If conventional diffraction gratings are used, then the device structure is simple, but diffraction efficiency for transverse electric polarized light is limited across the visible spectrum
Solution Approach 1:
The patent employs meta-grating structures that combine multiple material layers and nanoscale patterns to achieve superior diffraction performance. The composite structure includes metallic and dielectric materials arranged in specific configurations to enhance transverse electric polarized light diffraction efficiency across the visible spectrum
Solution Approach 2:
The meta-grating applies local quality variations at the nanoscale level, where different regions of the grating structure have specifically tailored geometric properties and material compositions to optimize diffraction efficiency for different wavelengths and polarization states of light
3Ease of manufacture
If conventional optical surfaces are used, then manufacturing is easier, but the field of view is limited and image information cannot be effectively conveyed
Solution Approach 1:
The freeform surface introduces additional geometric dimensions and complexity to the conventional optical surface, enabling light routing in multiple directions and expanding the effective field of view. The freeform geometry creates multiple virtual image sources that broaden the angular coverage
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
The solution enhances the near-eye display's ability to convey image information efficiently and corrects optical aberrations, providing a wide field of view and high diffraction efficiency, making it suitable for virtual or augmented reality applications.
Implementation Method 1
The meta-grating is further configured to provide at least 50% +1 diffraction order Transverse Electric polarized absolute grating efficiency at a desired wavelength of the visible light spectrum in reflection, within a range of operation of an angle of incidence that spans about 20°
Implementation Method 2
The freeform property of the nanostructured surface is either configured to correct optical aberrations induced by tilting and decentering of the first reflective surface and the second reflective surface
Implementation Method 3
aspects of the nanostructured surface are used to couple light into or out of the waveguide
Data Source
Figure 1a~2b
Figure 3a~4b
Figure 5~6
AI summary
A near eye display includes at least one of a combiner, a secondary mirror, and a waveguide having a freeform nanostructured surface. The freeform nanostructured surface encompasses a freeform surface, a nanostructured surface or a combination of both the freeform surface and the nanostructured surface. The freeform nanostructured surface can be incorporated into a combiner or a secondary mirror in the near eye display in a compact folded geometry, wherein an anamorphic or freeform optic can be optically intermediate an image source and the freeform nanostructured surface. The nanostructured surface can include a meta-grating operable across the visible spectrum. The meta-grating includes meta-atoms configured to provide a given efficiency at the desired wavelengths in reflection.