Wearable Optical Article Interferential Coating for Thin High-NIR Reflection
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Solution Overview
Problem
Existing optical coatings for wearable devices struggle to achieve high near-infrared reflection while maintaining a low visible light reflectance, particularly for applications like spectacles and contact lenses, due to thickness constraints and material limitations, which are not suitable for common organic substrates.
Innovation Solution
A multilayer interferential coating with alternating low and high refractive index layers, optimized for near-infrared reflection, achieving peak reflectance of at least 70% at 850 nm or 940 nm, while maintaining low visible light reflectance of less than 1.5%, using materials like SiO2, SiN, ZrO2, and Ta2O5, with a total thickness of less than 750 nm.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If multilayer quarter-wave reflection stacks are used to achieve high NIR reflection, then peak reflectance at 850 nm or 940 nm is improved, but total coating thickness increases to ≥1000 nm which is not applicable for common organic substrates
Solution Approach 1:
The patent changes the optical thickness parameters of the coating layers from conventional quarter-wave (λ/4) to variable thicknesses. Specifically, the first high-index layer has optical thickness between λ/6 and λ/3, the first low-index layer has optical thickness between λ/6 and λ/2, and subsequent layers follow specific thickness relationships. This parameter optimization enables achieving ≥70% peak reflectance at 850 nm or 940 nm while keeping total thickness <750 nm, making it compatible with organic substrates.
Solution Approach 2:
The patent employs composite multilayer structures combining materials with different refractive indices (high-index materials like TiO2, Ta2O5, Nb2O5 with low-index materials like SiO2, MgF2) in specific thickness ratios. This composite approach allows precise control over the optical interference effects, enabling high NIR reflection with reduced thickness compared to conventional uniform quarter-wave stacks.
2Illumination intensity
If quarter-wave reflection stacks with many layers are used to increase reflectance, then maximum reflectance approaches 100%, but the coating becomes too thick for wearable optical articles
Solution Approach 1:
The patent optimizes the thickness parameters of each layer to achieve the desired reflectance with fewer layers. By setting the first high-index layer thickness to λ/6-λ/3 and the first low-index layer to λ/6-λ/2, and establishing specific thickness relationships between subsequent layers, the patent achieves ≥70% peak reflectance with a total thickness <750 nm, avoiding the need for 10+ layers required by conventional quarter-wave stacks.
Solution Approach 2:
The patent uses a partial approach by not requiring the full 100% reflectance that would demand many layers. Instead, it targets a practical threshold of ≥70% peak reflectance, which is sufficient for the intended application while keeping the coating thickness manageable at <750 nm, balancing performance with manufacturability.
3Measurement precision
If interferential coating is added to enhance NIR reflection, then detection range of proximity sensors is extended, but manufacturing precision requirements increase
Solution Approach 1:
The patent defines specific optical thickness ranges for each layer (first high-index: λ/6-λ/3, first low-index: λ/6-λ/2, second low-index: λ/8-λ/4) that provide a balanced compromise between achieving sufficient NIR reflection and maintaining manufacturability. These parameter specifications enable standard manufacturing processes to achieve the required performance without excessive precision demands.
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 enhances near-infrared reflection for wearable optical articles, allowing them to interact with digital devices' proximity sensors, extending the detection range beyond conventional limits, and providing alerts for optimal reading distances.
Implementation Method 1
an interferential coating configured to selectively reflect light of at least one range of wavelengths of an incident light in the near infrared light spectrum
Implementation Method 2
The peak reflectance of the interferential coating, measured at a substantially normal to the optical article at a wavelength of 850 nm or 940 nm, is at least 70%
Implementation Method 3
A multilayer interferential coating with alternating low and high refractive index layers, optimized for near-infrared reflection
Implementation Method 4
alternating low and high refractive index layers, optimized for near-infrared reflection
Data Source
AI summary
Disclosed is a user wearable optical article including an optical substrate and an interferential coating. The interferential coating may be disposed the substrate and may be configured to selectively reflect light of at least one range of wavelengths of an incident light in the near infrared light spectrum. A peak reflectance measured at a substantially normal to the optical article may be at least 70%. An eyewear including an optical article and a method for producing an optical article are also disclosed. The method may include providing the optical substrate and providing the interferential coating disposed on the optical substrate. The interferential coating may selectively reflect light of at least one range of wavelengths of an incident light in the near infrared light spectrum. A peak reflectance may be at least 70% and the interferential coating has a mean reflectance of less than 1.5% in a visible light range.