Dual Waveguide Optical System for Head-Mounted Display FOV Expansion
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Solution Overview
Problem
Conventional head-mounted display (HMD) optical lens modules limit the field of view (FOV) due to their volume and complexity, particularly when trying to achieve a wider FOV and full-color image with a slim design, as they require difficult-to-fabricate biconic lenses to expand image light in two directions.
Innovation Solution
The use of a dual optical waveguide system with a first and second optical waveguide device, each containing beam splitters, where the second light entering surface faces the first light exiting surface with a gap between them, allowing image light to be expanded in two directions without the need for an extra biconic lens, reducing volume, weight, and fabrication complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a conventional optical lens module is used to implement AR display effect, then the image light can be transmitted to user's eyes, but the field of view is greatly limited and the volume is large
Solution Approach 1:
The patent divides the optical system into multiple waveguide devices, each handling specific light paths. The first waveguide device receives image light from the display apparatus, while the second waveguide device receives external ambient light. This segmentation allows each waveguide to be optimized for its specific function, enabling a wider field of view while maintaining a compact overall volume.
Solution Approach 2:
The patent introduces a beam splitter as an intermediary component within the waveguide devices. The beam splitter mediates between the image light path and the external ambient light path, allowing both types of light to be combined and directed to the user's eyes. This intermediary component enables the superposition of virtual and real images without requiring a large optical system.
2Adaptability or versatility
If a beam splitter array is added to expand image light in one direction, then the field of view can be widened, but a biconic lens is required to expand image light in two directions which is difficult to fabricate and increases cost
Solution Approach 1:
Instead of using a complex biconic lens to expand image light in two directions simultaneously, the patent segments the light expansion function into two separate waveguide devices. The first waveguide device expands image light in one direction using a beam splitter array, and the second waveguide device handles the other direction. This segmentation replaces the difficult-to-fabricate biconic lens with simpler, more manufacturable components.
Solution Approach 2:
The patent combines multiple waveguide devices to achieve the light expansion function that would otherwise require a single complex biconic lens. By merging the functions of the first and second waveguide devices, each with their own beam splitter arrays, the system achieves two-directional light expansion with components that are easier to fabricate and assemble.
3Adaptability or versatility
If a biconic lens is used to expand image light in two directions, then the FOV can be enlarged, but the fabrication difficulty and cost become extremely high
Solution Approach 1:
The patent segments the optical system into multiple functional modules: a display apparatus, a first waveguide device with beam splitters for one direction, and a second waveguide device with beam splitters for another direction. This modular segmentation replaces the single complex biconic lens with multiple simpler components, reducing overall device complexity while maintaining the enlarged field of view capability.
Solution Approach 2:
The waveguide devices serve multiple functions: they guide image light from the display apparatus, expand light in specific directions using beam splitter arrays, and combine with external ambient light paths. This multi-functionality replaces the need for specialized components like biconic lenses, simplifying the overall optical system design.
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 results in a smaller, lighter HMD with a larger FOV and lower fabrication costs compared to conventional designs, as the image light is effectively guided to the user's eyes without the need for additional lenses, enhancing the AR display effect.
Implementation Method 1
The first beam splitter is disposed in the first optical waveguide device... capable of expanding the image light on a direction to guide the image light of the projection apparatus to the user's eyes
Implementation Method 2
an angle between the first light entering surface and the first light exiting surface is less than 90 degrees
Implementation Method 3
The image light enters the first optical waveguide device through the first light entering surface... The first light exiting surface is connected to the first light entering surface
Data Source
AI summary
An optical system including a first optical waveguide device, and a second optical waveguide device is provided. The first optical waveguide device includes a first light entering surface, a first light exiting surface and a first beam splitter. An image light emitted from the display enters the first optical waveguide device through the first light entering surface. The second optical waveguide device includes a second light entering surface, a second light exiting surface and a second beam splitter. The second light entering surface faces the first light exiting surface. A gap is formed between the second light entering surface and the first light exiting surface. Besides, a head-mounted display using the optical system described above is also provided.