Waveguide Lens Structure for Lightweight Stable Imaging
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Solution Overview
Problem
Existing waveguide lenses face challenges in simultaneously achieving lightweight design and imaging stability due to the deformation of thick glass cover plates during bonding, which can damage diffraction gratings and affect imaging performance, and the added weight from multiple glass layers.
Innovation Solution
A waveguide lens design incorporating a filling layer and a low-refractive-index transparent layer to protect the diffraction grating, reducing the thickness of glass cover plates and ensuring imaging stability by preventing deformation and external contamination, while maintaining effective diffraction and total reflection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If the thickness of the glass cover plate is reduced to achieve lightweight design, then the weight of the waveguide lens is reduced, but the glass cover plate is prone to deformation under pressure during bonding, which damages the diffraction grating and affects imaging performance
Solution Approach 1:
A filling layer with refractive index matching the waveguide substrate is introduced between the diffraction grating and the glass cover plate. This intermediary layer distributes the bonding pressure uniformly, preventing localized stress concentration that would deform thin glass cover plates while maintaining their weight-reducing benefit. The filling layer acts as a pressure-distributing mediator that protects the diffraction grating from deformation during the bonding process.
Solution Approach 2:
The refractive index of the filling layer is specifically matched to the waveguide substrate material to eliminate optical interfaces that would cause reflections or refractions. This parameter matching ensures that the filling layer is optically invisible while providing mechanical support and pressure distribution, thus maintaining imaging performance while enabling thinner glass cover plates.
2Object-affected harmful factors
If two layers of glass cover plates are added to protect the waveguide lens surfaces from pollution, then the protection against fingerprints and dirt is improved, but the thickness of the waveguide lens increases to about 1.7 mm, making it too thick for lightweight AR applications
Solution Approach 1:
The glass cover plates are reduced to thin film structures (first glass cover plate thickness: 0.05-0.5 mm, second glass cover plate thickness: 0.05-0.5 mm) that provide sufficient protective function against pollution while minimizing thickness contribution. These thin film structures maintain their protective capability against fingerprints and dirt while keeping the overall lens thickness within acceptable limits for lightweight AR applications.
Solution Approach 2:
The protective function is segmented into two separate glass cover plates positioned at different locations: the first glass cover plate protects the diffraction grating surface, while the second glass cover plate protects the opposite surface of the waveguide substrate. This segmentation allows each plate to be optimized for minimal thickness while collectively providing comprehensive protection against pollution on both surfaces.
3Object-affected harmful factors
If a glass cover plate is added to protect the diffraction grating from external impurities, then the protection against pollution damages is improved, but the complexity of the bonding process increases due to the need for precise thickness control to prevent deformation
Solution Approach 1:
The filling layer serves as a bonding intermediary that simplifies the bonding process by providing a compliant interface between the diffraction grating and the thin glass cover plate. This intermediary layer accommodates thickness variations and positioning tolerances, reducing the precision requirements for bonding process control while maintaining effective protection against pollution damages.
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 design achieves a lightweight and stable waveguide lens by protecting the diffraction grating from external forces and contaminants, reducing thickness and weight, and ensuring reliable imaging performance without air gaps that cause misting.
Implementation Method 1
in order to avoid the damage to the total reflection transmission of rays inside the waveguide lens
Data Source
AI summary
A waveguide lens, including: a waveguide substrate, wherein a diffraction grating is provided on a side surface of the waveguide substrate; a filling layer, wherein the filling layer is provided in a filling manner on a side of the diffraction grating that is away from the waveguide substrate; a low-refractive-index transparent layer, wherein the low-refractive-index transparent layer is connected with the filling layer; a first glass cover plate, wherein the first glass cover plate is bonded to a side surface of the low-refractive-index transparent layer that is away from the waveguide substrate; and a second glass cover plate, wherein the second glass cover plate is bonded to another side surface of the waveguide substrate. The problem of it being difficult to simultaneously take lightweight and imaging stability of a waveguide lens in the prior art into consideration is solved.