Decentering Optical System for HMD Image Completeness
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Solution Overview
Problem
Conventional image display apparatuses for head-mounted displays (HMDs) face challenges in providing a wide view angle while maintaining a small and thin form factor, as they often result in image lacking due to the non-overlapping light fluxes at the boundary parts of combined images when the observer's eye is rotated, and require large overlapping areas that reduce efficiency and increase the size of the optical system.
Innovation Solution
The image display apparatus incorporates a decentering optical system with reflective surfaces that overlap light flux components from multiple display elements on the exit pupil plane, eliminating the need for overlapping areas in the original images and enhancing image information presentation efficiency by ensuring all light fluxes are introduced to the observer's pupil, even when the eye is rotated.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional optical systems with V-shaped mirrors are used, then the device structure is simple, but image lacking occurs when the observer's eye is rotated
Solution Approach 1:
The patent introduces a decentering optical system where light fluxes from multiple display elements are overlapped in the exit pupil plane (a different spatial dimension) rather than requiring overlapping areas in the image plane. This dimensional shift allows the optical system to maintain image completeness across eye rotations without increasing structural complexity
Solution Approach 2:
The patent employs asymmetric optical paths for different display elements, with each element having a specific viewing angle range. The decentered arrangement of optical components creates asymmetric light flux distribution that is then overlapped in the exit pupil plane, ensuring complete image coverage without requiring symmetric overlapping areas
2Reliability
If overlapping areas are provided in original images to introduce all light fluxes to the eye, then image completeness is improved, but image information presentation efficiency decreases and device size increases
Solution Approach 1:
The patent resolves this contradiction by shifting the overlap operation from the image plane to the exit pupil plane. Display elements can maintain their full resolution without redundant overlapping areas, while the decentering optical system ensures that light fluxes from all elements are properly overlapped in the exit pupil plane, maintaining both efficiency and completeness
3Reliability
If overlapping areas are provided in original images to introduce all light fluxes to the eye, then image completeness is improved, but the optical system size increases
Solution Approach 1:
The patent eliminates the need for large overlapping areas in the image plane by performing the overlap function in the exit pupil plane through decentered optical paths. This allows for a more compact display element arrangement and reduces the overall optical system size while maintaining complete image coverage
Solution Approach 2:
The patent divides the optical system into multiple decentered segments, each handling a specific display element's light flux. This segmentation allows for optimized placement of optical components and reduces the overall footprint compared to a unified system requiring large overlapping areas
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 configuration allows for a compact, efficient image display with a wide view angle by ensuring all light fluxes are integrated on the exit pupil plane, reducing the thickness of the optical system and preventing image lacking, thus improving the presentation of seamless enlarged combined images.
Implementation Method 1
When a cross-section of the optical system on which optical paths of the first light flux and the second light flux are turned by reflections at the reflective surface is defined as a decentering cross-section
Data Source
AI summary
The image display apparatus includes first and second display elements respectively displaying first and second original images, and an optical system presenting an enlarged combined image of the first and second original images with first and second light fluxes from the first and second display elements. The optical system includes at least one reflective surface. When a cross-section of the optical system on which optical paths of the first and second light fluxes are turned by reflections at the reflective surface is defined as a decentering cross-section, the first and second original images correspond to different view angles in the decentering cross-section. Light flux components respectively included in the first and second light fluxes and introduced to a same image point in the enlarged combined image are overlapped with each other on an exit pupil plane.