Curved Exit Pupil Expander for Near-Eye Display Focus
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Solution Overview
Problem
Near-to-eye displays using diffractive exit pupil expanders are limited to a fixed viewing distance, causing pixel blurring for near-distance objects and restricting applications like stereoscopic 3D viewing, especially for individuals with vision impairments and in mobile augmented reality scenarios.
Innovation Solution
The use of cylindrically or spherically shaped exit pupil expanders with non-flat surfaces allows for the generation of virtual images at multiple viewing distances, enabling adjustable focus and convergence for improved augmented reality and stereo functionality by employing multiple light-guiding structures with different curvature radii and optical engines with adjustable power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a planar exit pupil expander is used to provide an input image at a finite viewing distance, then the display can be compact and suitable for mobile applications, but each display pixel appears replicated or blurred due to the whole range of incident ray angles emerging from all ray-interception points
Solution Approach 1:
The patent applies spherical or aspheric curvature to the exit pupil expander plate instead of using a planar surface. This curvature modifies the optical path of rays such that rays from a single display pixel converge to a single point in the virtual image, eliminating the replication and blurring effect while maintaining compact form factor suitable for mobile applications
2Volume of moving object
If the imaging optics is designed to provide an input image at a finite viewing distance, then the system is compact, but the viewing distance cannot be adjusted to match physical objects for augmented reality applications
Solution Approach 1:
The patent implements a tunable imaging optics system that can dynamically adjust the focal length or optical power. This allows the system to change the virtual image distance to match different physical object distances in augmented reality scenarios, while the curved exit pupil expander maintains compactness. The combination enables both compact form factor and adjustable viewing distances
3Device complexity
If a planar exit pupil expander is used, then the structure is simple, but near-sighted people experience limitations and stereoscopic 3D viewing is restricted
Solution Approach 1:
By using spherical or aspheric curved surfaces in the exit pupil expander, the patent extends the usable viewing distance range and improves image quality for near-sighted users. The curvature allows proper focusing of virtual images at various distances, enabling stereoscopic 3D viewing and broader adaptability while adding only moderate structural complexity compared to planar designs
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
This solution enhances the viewing experience by allowing simultaneous display at multiple distances, reducing accommodation-convergence mismatch and improving comfort for users, particularly in mobile and outdoor applications.
Implementation Method 1
a light-guiding structure configured to guide optical waves
Implementation Method 2
an out-coupling element disposed on the first or the second surface of the first or the second light-guiding structure and being offset from the said in-coupling element and configured to output an output optical beam
Data Source
AI summary
A method and an apparatus for providing a first light-guiding structure and a second light-guiding structure to receive an input optical beam and output an output optical beam to be viewed by a user. At least one of the first or the second light-guiding structure has a non-flat shape. The first and the second light-guiding structures are configured to produce virtual images at different viewing distances.