Waveguide Pupil Expander for Aberration-Limited Viewing Windows
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Solution Overview
Problem
Conventional projection lenses used for holographic displays suffer from aberrations when a large viewing window is required, particularly in coherent light systems, which degrade image quality due to the periphery of the lens contributing most to image aberrations.
Innovation Solution
A waveguide pupil expander is designed to replicate only the center section of the projection lens, using an aperture stop to eliminate light rays from the periphery, and a graded coating to compensate for light intensity loss, expanding the exit pupil while minimizing aberrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a large aperture projection lens is used to provide a large viewing window, then the viewing window size is improved, but image quality deteriorates due to increased aberrations from the lens periphery
Solution Approach 1:
The patent segments the projection lens aperture into a central section and a peripheral section. The waveguide pupil expander replicates only the central section of the lens, effectively separating the useful central portion from the harmful peripheral portion that causes aberrations. This segmentation allows the system to maintain a large viewing window while avoiding the quality degradation caused by the lens periphery.
Solution Approach 2:
The patent extracts and eliminates the harmful peripheral section of the projection lens using an aperture stop. By removing the peripheral light rays that contribute most to aberrations, the system retains only the central light rays that provide acceptable image quality. This extraction resolves the contradiction by sacrificing the peripheral aperture area while preserving image quality.
2Manufacturing precision
If the aperture of the projection lens is reduced to eliminate peripheral aberrations, then image quality is improved, but the viewing window size decreases
Solution Approach 1:
The patent uses a waveguide pupil expander to create multiple replicas of the aperture stop (which defines the reduced central aperture). These replicas expand the effective viewing window by distributing the central aperture image across a larger area, allowing the system to maintain a large viewing window while using only the central, high-quality portion of the lens.
Solution Approach 2:
The patent transitions from a single-aperture configuration to a multi-replica configuration in the waveguide pupil expander. By creating multiple images of the central aperture stop through the waveguide, the system expands the viewing window in a different dimensional space, resolving the contradiction between aperture size and viewing window size.
3Manufacturing precision
If an aperture stop is introduced to block peripheral light rays, then aberrations are reduced, but light intensity decreases
Solution Approach 1:
The waveguide pupil expander creates multiple replicas of the aperture stop, effectively multiplying the light-gathering area. While each individual replica receives less light than the full aperture, the combined effect of multiple replicas compensates for the intensity loss, maintaining acceptable overall light intensity while achieving aberration reduction.
Solution Approach 2:
The patent changes the spatial distribution parameter of the light rays by creating multiple dispersed replicas of the aperture stop. This parameter change allows the system to redirect light that would otherwise be blocked into multiple alternative paths, compensating for the intensity reduction caused by the aperture stop.
Data Source
AI summary
Disclosed embodiments include a display system having a viewing window on a viewing plane, the display system comprising a picture-generating unit and an imaging system, where the picture-generating unit displays a picture on a display plane that is a holographic reconstruction formed from a hologram of the picture. The imaging system comprises a projection lens disposed between the display plane and viewing plane, an aperture stop, and a waveguide pupil expander. The projection lens comprises a pair of planar surfaces that define the boundaries of the projection lens, the aperture stop restricts the aperture of the projection lens in the first direction and forms the limiting aperture stop of the imaging system, and the waveguide pupil expander receives light of the picture from the projection lens through the aperture stop and replicates the aperture stop to expand the viewing window of the display system.