Bragg Grating Waveguide for Multi-Depth AR Displays
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Solution Overview
Problem
Conventional 3-D display systems often cause discomfort due to a mismatch between accommodation and vergence, leading to an unrealistic and uncomfortable perception of depth.
Innovation Solution
A head-mounted display system utilizing a combination of volume phase holographic and liquid crystal polarization gratings to provide separate presentations of images corresponding to multiple depth planes, aligning accommodation and vergence for a more realistic and comfortable 3-D simulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional 3-D display systems are used, then image content can be presented to the user, but accommodation and vergence mismatch occurs causing discomfort and unrealistic depth perception
Solution Approach 1:
The display system segments the image content into multiple depth planes, with each plane presented at its appropriate focal distance. This allows different portions of the image to be focused at different distances, enabling the accommodation-vergence relationship to be maintained for each depth plane while presenting a composite 3-D image to the user.
Solution Approach 2:
The system adds the dimension of focal distance to the traditional 2-D display by presenting image content at multiple focal distances corresponding to different depth planes. This creates a multi-focal display where image content exists not only in lateral dimensions but also in the depth dimension with appropriate focus distances.
2Reliability
If multiple depth planes are presented with separate image content, then a more realistic 3-D simulation is achieved, but device complexity increases
Solution Approach 1:
The system creates multiple copies of the image content, with each copy optimized for a specific depth plane and focal distance. These copies are then superimposed to form the composite 3-D image, allowing each depth plane to be independently optimized while maintaining overall system coherence.
Solution Approach 2:
The display system is designed to perform multiple functions simultaneously: presenting image content at multiple depth planes, maintaining appropriate focus distances for each plane, and combining them into a unified 3-D image. This multi-functionality is achieved through a unified optical architecture that handles all depth planes through consistent optical paths.
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 system achieves a highly believable simulation of perceived depth by aligning accommodation and vergence, providing a more comfortable and realistic 3-D experience.
Implementation Method 1
a first reflective diffractive optical element including a volume phase holographic grating configured to reflect light at a particular incident angle and transmit light at other incident angles
Implementation Method 2
a second reflective diffractive optical element including a liquid crystal polarization grating configured to transmit incident light having a first polarization state and reflect incident light polarized having a second different polarization state
Implementation Method 3
The combination of the first and second reflective diffractive optical elements can be disposed on one side of the waveguide and be configured to operate as a transmissive diffractive optical element
Data Source
AI summary
A head-mounted display system can include a head-mountable frame, a light projection system configured to output light to provide image content to a user's eye, and a waveguide supported by the frame. The waveguide can be configured to guide at least a portion of the light from the light projection system coupled into the waveguide to present the image content to the user's eye. The system can include a grating that includes a first reflective diffractive optical element and a second reflective diffractive optical element. The combination of the first and second reflective diffractive optical elements can operate as a transmissive diffractive optical element. The first reflective diffractive optical element can be a volume phase holographic grating. The second reflective diffractive optical element can be a liquid crystal polarization grating.