Distributed Head-Mounted Display System with Light-Guide Optical Element
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Solution Overview
Problem
Conventional compact optical modules for head-mounted displays (HMDs) become bulky and impractical as the desired field-of-view increases, leading to sensitivity in eye-motion-box viewing angles and poor image quality, especially in mobile applications where compactness and mobility are crucial.
Innovation Solution
The use of a compact light-guide optical element (LOE) that allows for wide field-of-views and large eye-motion-box values, enabling a high-quality, compact optical system with improved manufacturability and reduced sensitivity to eye movements, and facilitating the integration of a narrowband wireless communication channel between a head-mounted display unit and a portable control unit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a conventional free-space optical module is used for HMD, then the system can achieve basic display functionality, but the optical module becomes larger, heavier and bulkier as the desired field-of-view increases
Solution Approach 1:
The optical system is divided into separate functional modules: a compact light-guide optical element (LOE) for image projection and a portable control unit for processing and wireless transmission. This segmentation allows the HMD to maintain a small form factor while the control unit handles the computational load and provides a larger display interface.
Solution Approach 2:
The patent transitions from a direct-view display in the portable control unit to a virtual image projection through the LOE in the HMD. This dimensional change allows the display content to be projected into the user's eye through a compact optical path, achieving a large virtual image within a small physical footprint.
2Volume of moving object
If compact optical solutions are implemented to reduce size, then the device becomes more compact, but the eye-motion-box (EMB) becomes very small (typically less than 8 mm) and the system becomes sensitive to eye movements
Solution Approach 1:
The optical system incorporates dynamic adjustment capabilities through the LOE design that can adapt to eye movements. The wireless communication between the portable control unit and HMD allows for real-time adjustments to maintain optimal display conditions as the user's eye position changes.
3Volume of moving object
If a direct-display is used in mobile devices to meet mobility requirements, then the device remains compact, but the image viewing quality becomes poor
Solution Approach 1:
The light-guide optical element acts as an intermediary between the compact display source in the portable control unit and the user's eye in the HMD. This intermediary optical system projects the display content as a large virtual image, significantly improving viewing quality while maintaining the compactness of the mobile device.
4Manufacturing precision
If wideband wireless transmission is used for high-quality image transmission, then image quality improves, but health hazards and power consumption issues arise
Solution Approach 1:
The system uses narrowband wireless communication for control signals and metadata transmission, while the high-quality image data is processed and displayed locally through the LOE projection system. This partial use of wireless transmission (only for essential control data) avoids the health and power consumption issues associated with wideband transmission of high-resolution image data.
Data Source
AI summary
There is provided an electro-optical system, including at least two spaced-apart units, a head-mounted display (HMD) unit, having a video signal source, a display source for displaying video signals from the display source, an optical module for projecting video signals from the display source into a user's eye, a driving electronic module, a power supply, and a portable control unit. The two spaced-apart units communicate by a narrowband wireless channel.