Near-to-Eye Optical Module with Aspherical Waveguide Surfaces
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Solution Overview
Problem
Existing augmented reality (AR) head-mounted devices are bulky and heavy due to large optical modules, and current optical waveguide technologies are not optically efficient, making it difficult to integrate AR solutions with traditional glasses or head-mounted devices while ensuring high-quality image presentation and a wide field of view.
Innovation Solution
The development of an optical module for near-to-eye display devices that includes a substrate with specific reflective surfaces and non-planar incident and exit surfaces, allowing for a unique field of view configuration and improved light efficiency by utilizing aspherical or free-form surfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing prism technology is used for optical modules, then the device can achieve certain optical functions, but the weight and volume increase significantly
Solution Approach 1:
The patent replaces traditional mechanical prism-based optical systems with a waveguide-based optical system. The waveguide uses total internal reflection and diffraction grating structures to achieve the same optical functions (image projection, field of view expansion) without the bulk and weight of conventional prisms, directly resolving the contradiction between optical functionality and device weight.
Solution Approach 2:
The waveguide itself acts as a thin film structure that guides light through its bulk. This thin-film approach replaces thick prism assemblies, enabling the optical module to maintain its functions while dramatically reducing weight and volume for head-mounted display applications.
2Volume of moving object
If optical waveguide technology is used, then the device size is reduced, but optical efficiency decreases
Solution Approach 1:
The patent introduces curved or free-form exit surfaces on the waveguide. These curved surfaces optimize the extraction of light from the waveguide to the user's eye, improving coupling efficiency and reducing light loss. The curvature allows better matching of light rays to the pupil geometry, thereby enhancing optical efficiency while maintaining the compact waveguide structure.
Solution Approach 2:
The waveguide structure incorporates different surface properties at different locations: the input surface has specific coupling structures, the internal structure includes diffraction gratings at precise locations, and the exit surface has curved or free-form geometry. This local optimization of surface properties at critical locations maximizes light transmission efficiency throughout the waveguide path.
3Device complexity
If traditional optical modules are used, then the structure is simple, but the field of view is limited and image quality is insufficient
Solution Approach 1:
The waveguide extends the optical path in the thickness dimension of the waveguide substrate, allowing light to travel a longer effective distance within a compact lateral footprint. This dimensional approach enables expansion of the field of view and improved image quality without increasing the lateral size of the optical module, as the light propagation occurs primarily in the vertical dimension through the waveguide thickness.
Solution Approach 2:
The curved or free-form exit surfaces of the waveguide are designed to expand the angular range of light extraction, thereby widening the field of view. The curvature allows light rays from different angles to be efficiently extracted and directed to the user's pupil, increasing the visible field area while maintaining a simple overall waveguide structure.
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 optical module design achieves a more compact and lightweight form factor, enhances light efficiency by effectively utilizing light from both the center and edges of the microdisplay, and provides a wider field of view, reducing user fatigue and improving the overall viewing experience.
Implementation Method 1
The first reflective surface is disposed on the first end of the substrate and is configured to reflect light
Implementation Method 2
The second reflective surface is disposed on the second end of the substrate and is configured to receive the light reflected by the first reflective surface and reflect the received light
Data Source
AI summary
An optical module, a near-to-eye display device, and an optical substrate are disclosed. At least one first distance is defined between a first intersection line and a periphery of a second reflective surface along a first direction. At least one second distance is defined between the first intersection line and the periphery of the second reflective surface along a second direction. The at least one first distance is less than the at least one second distance. At least one third distance is defined between a second intersection line and a periphery of an exit surface along the first direction. At least one fourth distance is defined between the second intersection line and the periphery of the exit surface along the second direction. The at least one third distance is less than the at least one fourth distance.