HMD Eyepiece with Beam Splitters for Depth Sensing
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Solution Overview
Problem
Conventional near-to-eye optical systems for head-mounted displays suffer from limited field of view and bulkiness due to the use of mirrors and lenses, which restrict their practical applications in augmented reality and other fields.
Innovation Solution
The implementation of a head-mounted display eyepiece with dual reflective surfaces, including a polarization rotator and beam splitters, which expands the eyebox and enables depth sensing by superimposing computer-generated images over ambient scene light, allowing for a more compact and efficient near-to-eye optical system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If conventional near-to-eye optical systems use mirrors and lenses, then the system can display images, but the field of view is limited and the system becomes bulky
Solution Approach 1:
The patent combines multiple optical functions (beam splitting, polarization rotation, depth sensing) into a single integrated eyepiece structure. The waveguide integrates both the display optical path and depth sensing camera, eliminating the need for separate mirrors and lenses, thereby reducing eyepiece volume while expanding field of view through optimized light routing
2Area of stationary object
If conventional optical systems are used, then the structure is simple, but the eyebox size becomes small
Solution Approach 1:
The patent uses a waveguide structure that extends the optical path in the thickness dimension of the eyepiece. By routing light through multiple internal reflections and polarization rotations within the waveguide thickness, the system achieves a large eyebox area without increasing the lateral footprint, effectively trading structural complexity in one dimension for spatial efficiency in another
3Ease of operation
If mirrors and lenses are used in the optical system, then the system can function, but the overall system becomes bulky
Solution Approach 1:
The patent replaces traditional mechanical optical components (mirrors, lenses) with a waveguide-based optical system. The waveguide uses total internal reflection and polarization effects to guide and manipulate light, eliminating the need for bulky mechanical components while maintaining optical functionality and enabling practical wearable applications
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 field of view and reduces the size of the eyepiece while maintaining an acceptable eyebox size, enabling more practical and efficient augmented reality applications by allowing users to see both computer-generated and real-world images with improved clarity and accuracy.
Implementation Method 1
a polarization rotator and beam splitters, which expands the eyebox
Implementation Method 2
a polarization rotator and beam splitters, which expands the eyebox
Data Source
AI summary
An eyepiece for a head mounted display includes an imaging region and a viewing region. The imaging region includes a camera. The viewing region is aligned with an eye of a user and includes a first beam splitter and a second beam splitter. The viewing region is partially transparent to pass a first portion of ambient scene light received through an ambient scene side of the eyepiece out an eye-ward side of the eyepiece. The first BS and the second BS are partially reflective and oriented to redirect offset portions of the ambient scene light received through the ambient scene side along the eyepiece towards the imaging region. The camera is positioned to capture both of the offset portions of the ambient scene light redirected by the first beam splitter and the second beam splitter.