Multilayer Interferential Coatings for Wide-Angle Visible–NIR Reflection
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Solution Overview
Problem
Existing antireflective coatings do not effectively reduce reflections in both the visible and near-infrared regions across a wide range of angles of incidence, particularly above 35°, and lack robustness and aesthetic appeal, which is crucial for ophthalmic lenses used in augmented and virtual reality devices.
Innovation Solution
A multilayered interferential coating comprising high and low refractive index layers, with specific layer thicknesses and arrangements, achieves low reflection across the visible and near-infrared regions up to 60°, maintaining robustness and aesthetic appeal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional single-layer or simple multilayer antireflective coating is used, then the manufacturing process is simple and cost-effective, but the reflection reduction performance is insufficient in both the visible and near-infrared regions, especially at high angles of incidence above 35°
Solution Approach 1:
The patent divides the antireflective coating into multiple distinct layers (typically 3-7 layers) with alternating high and low refractive indices. Each layer has a specific thickness optimized for its refractive index, creating a segmented structure that progressively reduces reflections across the broad wavelength range from 400-1200 nm and maintains effectiveness at high angles of incidence up to 60°.
Solution Approach 2:
The patent employs composite coating structures combining materials with different refractive indices (high index materials like TiO2, Ta2O5, SiO2 with low index materials like MgF2, SiO2). This composite approach enables the coating to achieve superior broadband antireflective performance across visible and near-infrared regions while maintaining robustness and aesthetic appearance.
2Illumination intensity
If the antireflective coating is optimized for low reflection in the visible region, then aesthetic appearance is improved, but reflection reduction in the near-infrared region deteriorates
Solution Approach 1:
The patent systematically varies critical parameters including the refractive index values of coating materials, the thickness of each layer (optimized to λ/4 or variations thereof), and the number of layers in the stack. These parameter changes enable the coating to achieve low reflection across the entire spectrum from 400-1200 nm, with specific optimization for both visible aesthetics and NIR performance for eye tracking applications.
Solution Approach 2:
The patent extends the antireflective performance from the traditional single dimension of visible wavelength optimization to a broader spectral dimension covering 400-1200 nm. This is achieved by carefully selecting layer thicknesses and refractive indices that create destructive interference for reflected waves across this extended wavelength range, thereby improving both visible aesthetics and NIR transmission simultaneously.
3Measurement precision
If the antireflective coating is designed for high angle of incidence performance, then eye tracking accuracy is improved, but the coating complexity and manufacturing difficulty increase
Solution Approach 1:
The patent designs the coating structure to dynamically adapt to varying angles of incidence through its alternating high-low refractive index layer configuration. The specific thickness ratios and refractive index combinations create angle-insensitive antireflective properties that maintain low reflection from 0° to 60° incidence angles, ensuring consistent eye tracking accuracy across different viewing positions without requiring complex adaptive structures.
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 coating provides very low reflection in both the visible and near-infrared regions, ensuring high accuracy and reliability for eye tracking while maintaining consistent color appearance and robustness, suitable for ophthalmic lenses in augmented and virtual reality devices.
Implementation Method 1
multilayered interferential coating
Implementation Method 2
high refractive index layer (HI) having a refractive index higher than or equal to 1.55 and at least one low refractive index layer (LI) having a refractive index layer lower than 1.55
Data Source
AI summary
The invention relates to an optical article comprising a transparent substrate with a front main face and with a rear main face, at least one of the main faces being coated with a multilayered interferential coating comprising a stack of at least one high refractive index layer (HI) having a refractive index higher than or equal to 1.55 and at least one low refractive index layer (LI) having a refractive index layer lower than 1.55, characterized in that said multilayered interferential coating has a mean reflection factor for wavelengths ranging from 445 nm to a predetermined maximum wavelength higher than or equal to 1185 nm, noted Rm (445-≥1185), that is lower than or equal to 2.9%, preferably 2.6% at an angle of incidence lower than or equal to 45°.