Dual Waveguide HMD Eye Box Expansion
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Solution Overview
Problem
Existing head-mounted displays (HMDs) face challenges in balancing the miniaturization of the optical system with the expansion of the eye box, leading to compromised display performance and wearability.
Innovation Solution
The use of a dual waveguide system where the first waveguide reflects video light into the second waveguide, with both waveguides having parallel main planes for internal reflection, and the angle between the duplication directions of the two waveguides being less than 90 degrees, allowing for the enlargement of the eye box while maintaining a compact optical system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a waveguide is used to enlarge the eye box, then the eye box is expanded, but the optical system size increases and optical efficiency decreases
Solution Approach 1:
The patent divides the eye box enlargement function into two separate waveguides: a first waveguide that duplicates light in one direction and a second waveguide that duplicates light in another direction. This segmentation allows each waveguide to be optimized for its specific duplication direction, achieving comprehensive eye box expansion without requiring a single oversized waveguide structure.
Solution Approach 2:
The patent introduces a spatial dimensionality change by arranging the first and second waveguides at different orientations. The first waveguide duplicates light in a first direction while the second waveguide duplicates light in a second direction that is not parallel to the first direction. This multi-directional approach expands the eye box in multiple dimensions simultaneously, achieving compact optical system size while maintaining large eye box.
2Volume of moving object
If the angle between duplication directions of two waveguides is made small, then the optical system is miniaturized, but the eye box expansion effectiveness may be reduced
Solution Approach 1:
The patent optimizes the angle parameter between the duplication directions of the two waveguides. By setting the angle to be less than 90 degrees but not too small, the system achieves an optimal balance: the waveguides can be arranged in a compact configuration to minimize optical system size, while still maintaining effective eye box expansion in multiple directions.
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 enables the miniaturization of the optical system while expanding the eye box, improving display performance and wearability by reducing the size of the lens aperture and enhancing light utilization efficiency.
Implementation Method 1
each of the first waveguide and the second waveguide includes a pair of parallel main planes that confine video light by internal reflection
Data Source
AI summary
A head mounted display displays an image in the user's field of vision and includes a video display unit that generates the image to be displayed. A first waveguide and a second waveguide duplicate the video light from the video display unit. Each of the waveguides includes a pair of parallel main planes that confine video light by internal reflection. The first waveguide includes an incident surface that reflects video light into the inside and two or more outgoing reflective surfaces emit video light into the second waveguide. The second waveguide includes an input unit that couples video light from the first waveguide to the inside and an output unit that emits video light to the user's pupil, wherein the angle between the duplication direction of video light in the first waveguide and the duplication direction of video light in the second waveguide is less than 90°.