Multilayer Antireflective Coating for Ophthalmic Lenses in Low Luminance
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Solution Overview
Problem
Current antireflective coatings for ophthalmic lenses are optimized for photopic vision and do not effectively reduce reflectivity for scotopic vision, leading to increased glare and reduced light transmission in low luminance conditions.
Innovation Solution
A multilayered antireflective coating with a stack of high refractive index and low refractive index layers, specifically designed to achieve a mean light reflection factor of less than 0.5% for scotopic vision and less than 2.5% for photopic vision, using a spectral luminous efficiency function accurate for scotopic vision, and incorporating a weighting function for ultraviolet radiation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If traditional antireflective coatings are optimized for photopic vision with mean light reflection factor Rv lower than 2.5%, then aesthetic appearance and daytime visibility are improved, but scotopic vision performance deteriorates with increased glare and reduced light transmission in low luminance conditions
Solution Approach 1:
The patent applies parameter changes by optimizing the refractive index and thickness parameters of coating layers to achieve different reflectivity characteristics. The multilayer coating structure with specific refractive index gradients (ranging from 1.3 to 2.0) and controlled layer thicknesses (10-200 nm) creates wavelength-selective reflectivity that reduces scotopic glare while maintaining photopic light transmission. This resolves the contradiction by changing the optical parameters of the coating to simultaneously address both vision conditions.
Solution Approach 2:
The patent employs composite materials by combining multiple dielectric layers with different refractive indices (materials such as silicon oxide, titanium oxide, zirconium oxide, and magnesium fluoride) to create a multilayer antireflective coating. This composite structure enables differential control of light reflection across the visible spectrum, achieving low reflectivity in the blue-green region (400-550 nm) for scotopic vision while maintaining acceptable reflectivity in other regions for photopic vision, thus resolving the glare vs. light transmission contradiction.
2Illumination intensity
If the mean light reflection factor Rv is reduced to below 1% for photopic vision, then aesthetic appearance is improved, but the complexity of the multilayer coating structure increases
Solution Approach 1:
The patent applies local quality by creating spatial variation in the optical properties of the coating layers. Each layer in the multilayer structure has locally optimized refractive index and thickness parameters tailored to specific wavelength ranges. The refractive index gradient across layers (from 1.3 to 2.0) and the varying thicknesses (10-200 nm) provide localized optical control, achieving ultra-low reflectivity in critical blue-green regions while managing overall structural complexity through targeted local optimizations rather than uniform coating design.
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 significantly reduces perceived reflections under low luminance conditions, enhances night vision by increasing overall transmittance, and minimizes glare, while maintaining aesthetic appeal and high anti-reflective performance across both photopic and scotopic conditions.
Implementation Method 1
An antireflection coating usually consists of multilayers comprising interferential thin layers, generally an alternation of layers based on a dielectric material of high refractive index and a dielectric material of low refractive index
Implementation Method 2
the function of such a coating is to reduce its light reflection and therefore to increase its light transmission
Data Source
Figure 1~2
AI summary
This invention relates to an ophthalmic lens 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 antireflective 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 lower than 1.55, characterized in that said multilayered antireflective coating has: a mean light reflection factor in the visible region for photopic vision Rv lower than or equal to 2.5%, preferably lower than or equal to 0.9%, for at least an angle of incidence lower than 35°; a mean light reflection factor in the visible region for scotopic vision Rv' lower than or equal to 0.5%, preferably lower than or equal to 0.4%, for at least an angle of incidence lower than 35°.