Freeform Waveguide Prism for Head-Mounted Light Field Displays
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Solution Overview
Problem
Conventional head-mounted displays (HMDs) suffer from visual discomfort due to vergence-accommodation conflicts caused by the inability to render correct focus cues, leading to unnatural eye accommodation and retinal blurring, which limits their effectiveness in providing immersive virtual reality (VR) and augmented reality (AR) experiences.
Innovation Solution
A high-performance head-mounted light field display based on integral imaging using a freeform waveguide prism and a vari-focal element to enhance lateral and longitudinal resolutions, depth of field, and viewing angle, while maintaining a large eyebox and reducing cross-talk, by refracting and reflecting light through multiple freeform optical surfaces to create a 3D image at a selected location outside the prism.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional HMDs use a fixed-distance 2D image plane, then the device complexity is reduced, but the ability to render correct focus cues is lost, causing vergence-accommodation conflicts
Solution Approach 1:
The patent implements a tunable lens that can dynamically adjust its focal length to match different depth planes of the 3D scene. This dynamic focusing mechanism allows the display to render correct focus cues for objects at various distances, resolving the vergence-accommodation conflict while maintaining reasonable device complexity through electronic control rather than mechanical adjustment.
Solution Approach 2:
The patent changes the optical parameter (focal length) of the lens system to match different depth planes. By varying the focal length parameter in sync with the displayed depth information, the system renders accurate focus cues for 3D objects at different distances, improving focus cue accuracy without requiring a completely complex optical system.
2Reliability
If HMDs use stereoscopic 3D rendering with binocular disparities, then the perception of 3D space is improved, but the accommodation and convergence cues become decoupled, causing visual discomfort
Solution Approach 1:
The patent implements a feedback mechanism where the focal length of the tunable lens is adjusted based on the depth information of the displayed 3D scene. This feedback loop ensures that the accommodation cue (focal length) matches the convergence cue (binocular disparity), eliminating the decoupling effect that causes visual discomfort while maintaining accurate 3D perception.
Solution Approach 2:
The patent dynamically changes the focal length parameter of the lens system to match the depth plane of different 3D objects. This parameter adjustment synchronizes the accommodation response with the convergence response, resolving the cue conflict that causes visual discomfort while preserving accurate 3D scene perception.
3Device complexity
If HMDs lack variable focal length capability, then the device complexity is minimized, but the depth of field and viewing angle resolution are limited
Solution Approach 1:
The patent introduces a tunable lens that can dynamically adjust its focal length to match different depth planes of the 3D scene. This dynamic focusing mechanism allows the display to render correct focus cues for objects at various distances, resolving the vergence-accommodation conflict while maintaining reasonable device complexity through electronic control rather than mechanical adjustment.
Solution Approach 2:
The patent changes the optical parameter (focal length) of the lens system to match different depth planes. By varying the focal length parameter in sync with the displayed depth information, the system renders accurate focus cues for 3D objects at different distances, improving focus cue accuracy without requiring a completely complex optical system.
4Device complexity
If conventional HMDs use a fixed virtual image plane, then the optical system is simplified, but the ability to provide immersive VR and AR experiences is reduced due to visual discomfort
Solution Approach 1:
The patent implements a tunable lens that can dynamically adjust its focal length to match different depth planes of the 3D scene. This dynamic focusing mechanism allows the display to render correct focus cues for objects at various distances, resolving the vergence-accommodation conflict while maintaining reasonable device complexity through electronic control rather than mechanical adjustment.
Solution Approach 2:
The patent implements a feedback mechanism where the focal length of the tunable lens is adjusted based on the depth information of the displayed 3D scene. This feedback loop ensures that the accommodation cue (focal length) matches the convergence cue (binocular disparity), eliminating the decoupling effect that causes visual discomfort while maintaining accurate 3D perception.
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 provides a wider field of view, higher resolution, and a larger depth range, reducing visual discomfort and improving the immersion and accuracy of 3D scenes, enabling more effective VR and AR experiences with reduced artifacts and increased user comfort.
Implementation Method 1
a first freeform optical surface disposed to receive light from the lightfield and refract the received light into the body of the prism
Implementation Method 2
a second freeform optical surface disposed to receive the refracted light from the first freeform optical surface and reflect the light into the body of the prism
Implementation Method 3
a third freeform optical surface disposed to receive the light from the intermediate image and total internally reflect the light into the body of the prism
Implementation Method 4
a fourth freeform optical surface disposed to receive the reflected light from the third freeform optical surface and reflect the light back to the third freeform surface at an angle that allows the light to exit the prism
Data Source
AI summary
Freeform waveguide prism and use with head-mounted light field display with integral imaging and relay group.