Anti-Reflection Coating Without Al2O3 for Ultrawide-Angle Lenses
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Solution Overview
Problem
Existing anti-reflection coatings for lenses with large inclination angles suffer from poor anti-reflection performance and are prone to fogging when stored under high-temperature, high-humidity conditions due to the reaction between Al2O3 and silica aerogel layers.
Innovation Solution
A three- or four-layer anti-reflection coating structure is developed without Al2O3, where the refractive indices of the layers are specifically adjusted, with the second layer having a higher refractive index than the first and third layers, and the third layer being a silica aerogel, formed using a sol-gel method, to prevent fogging and maintain excellent anti-reflection performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Al2O3 is used in the first layer to prevent weathering of the substrate surface, then the anti-reflection coating has good durability, but the coating is prone to fogging when stored under high-temperature, high-humidity conditions due to reaction between Al2O3 and silica aerogel layers
Solution Approach 1:
The patent removes Al2O3 from the first layer to eliminate the harmful reaction with silica aerogel that causes fogging. The first layer is replaced with materials such as SiO2, TiO2, Ta2O5, or Nb2O5 that do not react with silica aerogel under high-temperature, high-humidity storage conditions, thereby eliminating the fogging problem while maintaining weathering prevention through the overall coating structure.
Solution Approach 2:
The patent changes the material composition parameter of the first layer from Al2O3 to alternative materials with different chemical properties. This parameter change prevents the chemical reaction with silica aerogel while maintaining the protective function against weathering, resolving the contradiction between durability and fogging resistance.
2Reliability
If a three-layer structure with porous silica having refractive index of 1.07-1.18 is used to achieve low reflectance, then anti-reflection performance is improved, but it becomes difficult to stably produce the porous silica layer with extremely high porosity
Solution Approach 1:
The patent expands the refractive index range of the third layer from the conventional 1.07-1.18 to 1.15-1.35, allowing the use of silica aerogel with higher refractive index (1.20-1.35) that can be more stably produced. This parameter change maintains acceptable anti-reflection performance while significantly improving manufacturing stability.
Solution Approach 2:
The patent uses silica aerogel as a composite material in the third layer, which provides both the required optical properties (refractive index 1.20-1.35) and structural stability. The aerogel structure maintains high porosity while achieving refractive indices that are more feasible for stable production compared to extremely porous silica.
3Adaptability or versatility
If existing anti-reflection coating structures are used on lenses with large inclination angles, then the coating can be applied to ultrawide-angle lenses, but the anti-reflection performance becomes poor in peripheral portions with large incident angles
Solution Approach 1:
The patent optimizes the refractive index distribution across the coating layers to achieve effective anti-reflection across different incident angles. By carefully selecting refractive indices where the second layer (1.75-2.50) is higher than the first (1.37-1.57) and third (1.20-1.35) layers, the coating maintains low reflectance from normal incidence to large incident angles, improving performance in peripheral portions of ultrawide-angle lenses.
Solution Approach 2:
The patent uses a composite multi-layer structure with materials having different refractive indices (SiO2, TiO2, Ta2O5, Nb2O5, silica aerogel) to achieve broad-angle anti-reflection. This composite structure creates multiple interference effects that suppress reflection across a wide range of incident angles, making the coating effective for ultrawide-angle applications.
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 achieves stable anti-reflection performance over a wide wavelength and angle range, including large inclination angles, and remains effective even after storage under high-temperature, high-humidity conditions, making it suitable for imaging equipment like ultrawide-angle lenses.
Implementation Method 1
the first and second layers being formed by a vacuum vapor deposition method
Implementation Method 2
the third layer being formed by a sol-gel method
Implementation Method 3
multi-layer, anti-reflection coatings comprising a combination of dielectric films having different refractive indices for utilizing interference effects with dielectric film thickness of 1⁄2λ or 1⁄4λ to a center wavelength λ
Data Source
AI summary
An anti-reflection coating having an three-layer structure comprising first to third layers formed in this order on a substrate, the substrate having a refractive index of 1.6-1.9, the first layer having a refractive index of 1.37-1.57, the second layer having a refractive index of 1.75-2.5, and the third layer having a refractive index of 1.18-1.32, to light in a wavelength range of 550 nm; the third layer being formed by silica aerogel; and the first and second layers containing no Al2O3.