Dual Waveguide HMD with Variable Reflectivity Splitting
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Solution Overview
Problem
Head-mounted display (HMD) devices face challenges in providing a large field of view (FOV) and maintaining good display quality while minimizing volume, as the proximity of the optical engine to the user's eye blocks the external environmental beam, reducing the effectiveness of augmented reality (AR) and limiting user immersion.
Innovation Solution
The HMD device employs a dual waveguide system with strategically designed light splitting elements and a lens module to project an image beam, ensuring a large FOV and minimizing volume, by optimizing the reflectivity and configuration of light splitting elements to avoid blocking the user's line of sight and enhance image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the optical engine is positioned close to the user's eye, then the display can be compact, but the external environmental beam is blocked from entering the user's eye, reducing AR effectiveness
Solution Approach 1:
The waveguide is divided into multiple segments with different optical functions: a first waveguide segment for guiding image beams from the optical engine, and a second waveguide segment for guiding external environmental beams to the user's eye. This segmentation allows each segment to be optimized for its specific function, enabling the optical engine to be positioned closer to the eye while maintaining AR effectiveness through the dedicated environmental beam passage in the second segment.
2Volume of moving object
If the optical engine is positioned close to the user's eye, then the device volume is reduced, but the field of view is limited
Solution Approach 1:
The patent utilizes the third dimension (depth) by positioning the optical engine in front of the user's eye rather than directly at the eye, and by using multiple waveguide segments arranged in different spatial orientations. This dimensional arrangement allows the image beams to be guided through the first waveguide segment while external beams pass through the second segment, effectively expanding the field of view without increasing the overall device volume.
3Manufacturing precision
If light splitting elements with high reflectivity are used, then image quality is improved, but the device volume increases
Solution Approach 1:
Different light splitting elements are positioned at different locations within the waveguide system, with each element having reflectivity optimized for its specific position and function. The first light splitting element in the first waveguide segment has reflectivity optimized for image beam guidance, while the second light splitting element in the second waveguide segment has reflectivity optimized for environmental beam passage. This local optimization allows good display quality without requiring uniformly high reflectivity throughout the entire system, thereby controlling device volume.
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 configuration allows for a significant increase in the field of view while maintaining a compact form factor, improving user immersion and AR effectiveness by allowing external environmental beams to be integrated seamlessly, thus enhancing the overall display quality and user experience.
Implementation Method 1
A reflectivity of the Nth one of the second light splitting elements is smaller than or equal to a reflectivity of the (N+1)th one of the second light splitting elements
Data Source
AI summary
A HMD device including a display, a first waveguide element and a second waveguide element is provided. The first waveguide element comprises a first light incident surface, a first light emerging surface and a plurality of first light splitting elements. An image beam is incident to the first waveguide element through the first light incident surface, and leaves the first waveguide element through the first light emerging surface. The second waveguide element comprises a second light incident surface, a second light emerging surface and a plurality of second light splitting elements. The image beam is incident to the second waveguide element through the second light incident surface. The image beam leaves through the second light emerging surface and is projected to the projection target. A reflectivity of the Nth one of the second light splitting elements is smaller than or equal to a reflectivity of the (N+1)th one of the second light splitting elements.