Lead-Free Glass Light Guide Plate for AR and VR Displays
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Solution Overview
Problem
Current light guide members for head-mounted displays have limited viewing angles and color reproducibility, and are not lead-free, making them unsuitable for virtual reality applications, while also being bulky and heavy, which is a concern for augmented reality devices.
Innovation Solution
A lead-free glass light guide plate with a refractive index of 1.8 or more, internal transmittance of 0.6 or more at 400 nm, and a thickness of 0.5 to 1.0 mm, featuring high parallelism and chromaticity coordinates, along with diffractive optical elements to enhance viewing angle and color accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If lead-free glass with high refractive index (1.8 or more) is used for the light guide plate, then viewing angle and color reproducibility are improved, but manufacturing complexity increases
Solution Approach 1:
The patent applies parameter changes by precisely controlling the refractive index of lead-free glass to be 1.8 or more, and specifying internal transmittance of 0.6 or more at 400 nm wavelength. These parameter specifications enable achieving wide viewing angle and excellent color reproducibility while using environmentally friendly lead-free materials, resolving the contradiction between performance improvement and manufacturing feasibility
Solution Approach 2:
The patent employs composite materials by formulating a specific lead-free glass composition that combines multiple oxides to achieve the required refractive index of 1.8 or more. This composite glass material maintains high optical performance while avoiding lead, thus improving viewing angle and color reproducibility without compromising environmental safety
2Weight of moving object
If the light guide plate thickness is reduced to make the device thinner and lighter, then portability is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent implements thin-film technology by reducing the light guide plate thickness to 0.5-1.0 mm, making the head-mounted display thinner and lighter for improved portability. This thin-film design maintains structural integrity while meeting the weight and thickness requirements for AR applications
Solution Approach 2:
The patent specifies precise parameter ranges including surface parallelism of 20 arc seconds or less and thickness uniformity of 5 μm or less. These stringent parameter controls ensure that even at reduced thickness of 0.5-1.0 mm, the light guide plate maintains optimal optical performance and manufacturing feasibility
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 solution provides a thin, lightweight light guide plate with improved color reproducibility and a wider viewing angle, suitable for both augmented and virtual reality applications, while being environmentally friendly by using lead-free materials.
Implementation Method 1
a propagation means which totally reflects the inputted image in the light guide member to propagate the inputted image toward a user's pupils
Implementation Method 2
the light guide plate may include a first optical element which diffracts the guided image light and outputs the image light to the user's pupil
Data Source
Figure 1~1(b)
Figure 2
Figure 3~3(b)
AI summary
Provided is a light guide plate for an image display device which uses lead-free glass, has excellent color reproducibility and a light weight, and may obtain a wide viewing angle. A light guide plate for an image display device, which guides image light inputted from an image display element and outputs the image light toward a user's pupil, is configured to be made of lead-free glass having a refractive index of 1.8 or more with respect to a wavelength of the image light, and to have internal transmittance of 0.6 or more with respect to a wavelength of 400 nm when a plate thickness is 10 mm. [Representative Drawing]