Light Guide Plate Diffractive Gratings Optical Efficiency Enhancement
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Solution Overview
Problem
Conventional head-mounted displays (HMDs) are bulky and heavy due to the large number of optical elements required, making them difficult to manufacture and wear.
Innovation Solution
A display device configuration that includes a light guide plate with an input grating and an output grating, along with an optical efficiency enhancement layer, to improve optical efficiency and reduce the number of optical elements needed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional HMD optical systems use multiple optical elements (mirrors, half mirrors) to achieve virtual image display, then the field of view and magnification requirements are met, but the device becomes bulky and heavy
Solution Approach 1:
The patent combines multiple optical elements (mirrors, half mirrors, beam splitters) into a single integrated optical system using diffractive optical elements and waveguides. This merging approach maintains the required field of view and magnification while significantly reducing the number of separate components, thereby reducing overall device weight and bulk.
Solution Approach 2:
The patent replaces traditional mechanical optical elements (mirrors, lenses, beam splitters) with diffractive optical elements and waveguide-based systems. This substitution uses optical diffraction and total internal reflection phenomena to achieve the same optical functions with fewer physical components, reducing device weight while maintaining performance.
2Adaptability or versatility
If conventional HMD optical systems use multiple optical elements to achieve virtual image display, then the optical functions are fulfilled, but the manufacturing complexity increases
Solution Approach 1:
The patent integrates multiple optical functions (beam splitting, reflection, focusing, wavelength separation) into single multifunctional optical elements such as diffractive optical elements and layered waveguide structures. This reduces the number of assembly steps and alignment requirements, thereby simplifying manufacturing while maintaining full optical functionality.
Solution Approach 2:
The patent designs optical elements that perform multiple functions simultaneously. For example, a single diffractive optical element handles beam splitting, wavelength separation, and focusing; waveguide layers guide different wavelengths through different paths. This multi-functionality reduces the total component count and simplifies the manufacturing process.
3Weight of moving object
If the number of optical elements is reduced using diffraction grating, then the device size and weight are reduced, but the optical efficiency may be compromised
Solution Approach 1:
The patent optimizes the parameters of diffractive optical elements including grating period, depth, shape, and material properties to maximize diffraction efficiency. By carefully controlling these parameters, the system achieves high optical efficiency with reduced component count, maintaining light throughput while minimizing energy loss.
Solution Approach 2:
The patent uses composite optical structures combining different materials with complementary properties. For example, combining diffractive optical elements made from specific polymers or glasses with waveguide layers of optimized refractive index to enhance light coupling and reduce losses. This composite approach maintains high optical efficiency while using fewer elements.
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
The proposed configuration enhances optical efficiency, reduces bulk and weight, and simplifies the manufacturing process of HMDs, enabling more compact and user-friendly augmented reality and virtual image displays.
Implementation Method 1
an input grating on a first surface of the light guide plate, the input grating being configured to diffract an input beam incident on the first surface at an angle equal to or greater than a critical angle of the light guide plate to generate a diffracted transmission beam propagating within the light guide plate through total internal reflection
Implementation Method 2
the input grating being configured to diffract an input beam incident on the first surface at an angle equal to or greater than a critical angle of the light guide plate to generate a diffracted transmission beam propagating within the light guide plate through total internal reflection
Implementation Method 3
an output grating on the first surface of the light guide plate and spaced apart from the input grating, wherein the output grating is configured to generate a first output beam passing through the output grating and emitted from the light guide plate by diffracting the diffracted transmission beam
Implementation Method 4
an optical efficiency enhancement layer arranged on a second surface of the light guide plate, the optical efficiency enhancement layer having a reflectance of 50% or more with respect to the input beam, wherein the second output beam is based on a transmitted input beam which is a second portion of the input beam passing through the input grating and reflected by the optical efficiency enhancement layer
Data Source
AI summary
A display device includes a light guide plate; an input grating on a first surface of the light guide plate and configured to generate a diffracted transmission beam; an output grating on the first surface of the light guide plate and spaced apart from the input grating, wherein the output grating is configured to generate a first output beam emitted from the light guide plate; and an optical efficiency enhancement layer on a second surface of the light guide plate and overlapping at least one of the input grating and the output grating in a traveling direction of the input beam, the second surface being opposite to the first surface.