Opaque Waveguide Optical Engine Assembly for HMDs
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Solution Overview
Problem
Conventional head-mounted displays (HMDs) have limitations such as small eye relief, eye box, and field of view, along with rapid battery drain due to high energy requirements, which are not ideal for hands-free computing and augmented reality applications.
Innovation Solution
A waveguide optical engine assembly is used in HMDs, comprising a microprojector, waveguide, and prism enclosed within an opaque housing, reducing environmental light interference and energy consumption while maintaining superior eye relief, eye box, and field of view.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If conventional refractive optics are used in HMDs, then the device structure is simple, but the eye relief, eye box, and field of view are smaller than desired
Solution Approach 1:
The patent introduces waveguides as intermediary optical elements between the microdisplay and the user's eye. These waveguides mediate the light path through total internal reflection and optical coupling, enabling extended eye relief and larger eye box without proportionally increasing overall device complexity
Solution Approach 2:
The optical system employs a nested configuration where the microdisplay is coupled to the waveguide, which is then integrated into the HMD housing. This nesting allows compact arrangement of optical components while maintaining large eye relief and field of view parameters
2Volume of moving object
If transparent waveguides are used to provide large field of view and eye relief, then optical performance is improved, but environmental light interferes with image quality and increases energy requirements
Solution Approach 1:
The patent applies local quality by making the housing opaque in specific regions where environmental light would interfere with the waveguide, while maintaining transparency or optical access in other regions. This selective application of opacity minimizes light interference without completely blocking the waveguide's optical function
Solution Approach 2:
The patent converts the harmful effect of environmental light into a benefit by using the opaque housing to block ambient light, thereby improving image contrast and quality. The previously harmful light interference becomes a design consideration that leads to improved overall system performance through strategic light blocking
3Illumination intensity
If transparent waveguides are used without opaque housing, then the device allows environmental awareness, but image quality deteriorates due to environmental light interference
Solution Approach 1:
The patent implements dynamic adaptability by making the housing opacity configurable or adjustable. The housing can transition between opaque and transparent states, or allow user selection, enabling the device to adapt to different environmental conditions and usage scenarios, thus maintaining both image quality and environmental awareness as needed
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 improved image quality and extended battery life by minimizing energy requirements and maintaining the benefits of waveguides like larger field of view and eye relief, making it suitable for both augmented reality and non-AR environments.
Implementation Method 1
Waveguides, which are generally clear or transparent (i.e. see through), have superior eye relief, eye box and fields of view when compared to conventional optics
Implementation Method 2
a prism for projecting a source image projected by the microprojector to the waveguide
Implementation Method 3
a prism for projecting a source image projected by the microprojector to the waveguide
Data Source
AI summary
A head-mounted computing device having a waveguide optical engine assembly is disclosed. The waveguide is enclosed in a housing to limit or minimize exposure of the waveguide to ambient light. Further, the waveguide optical engine assembly comprises a compact footprint by allowing the other components of the waveguide optical engine assembly, such as a microprojector, a prism assembly, and the like, to be placed behind a rear surface of the waveguide. In addition to the compact footprint of the waveguide optical assembly, the configuration of the waveguide optical assembly disclosed, allows for maximization of advantages provided by the waveguide as related to eye box and eye relief. Additionally, the power requirements of the waveguide are greatly reduced, which also results in a prolonged battery life powering the head-mounted computing device.