Optical Filter Asymmetric Coating HEV Blocking
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Solution Overview
Problem
Current optical filters struggle to independently control the reflection of desired wavelengths from the front and back surfaces of a lens without requiring application of both front and backside coatings, leading to increased back reflection into the eye, which is particularly problematic for blocking high energy visible light from sources like HID headlamps.
Innovation Solution
The use of absorbing layers within the coating stack allows for independent control of front and backside reflectance, enabling the creation of filters with high transmission in the visible spectrum while selectively blocking HEV wavelengths by incorporating materials like gold, tungsten, or nickel, which differ in refractive index and absorptance, thereby decoupling front and back reflectance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If an edge filter is used to block HEV wavelengths by reflecting light from the front surface, then front surface reflection is improved, but back surface reflection increases and reflects light into the eye
Solution Approach 1:
The patent applies asymmetric coating design where the front and back surfaces have different optical properties. The front surface has high reflectance for HEV wavelengths while the back surface has low reflectance, achieved through different coating configurations on each surface
Solution Approach 2:
The patent implements local quality by giving different regions (front and back surfaces) different optical characteristics. The front surface is optimized for HEV reflection while the back surface is optimized for light transmission with minimal reflection
2Illumination intensity
If traditional AR coatings are used to minimize reflection, then transmission is improved, but HEV wavelength blocking is insufficient
Solution Approach 1:
The patent segments the optical spectrum into different wavelength regions and applies different coating strategies for each. The coating stack is designed with specific layers optimized for visible transmission while other layers provide HEV wavelength blocking through absorption and reflection mechanisms
Solution Approach 2:
The patent uses composite coating structures combining multiple materials with different optical properties. The coating stack includes layers with varying refractive indices and absorption characteristics to simultaneously achieve high visible transmission and HEV blocking
3Object-affected harmful factors
If both front and backside coatings are applied to independently control reflection, then reflectance control is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent merges multiple functions into a single integrated coating stack applied to one surface. The coating structure combines HEV blocking, visible transmission optimization, and reflection control in one multi-layer configuration, eliminating the need for separate front and backside coatings
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
This approach effectively reduces back surface reflection while maintaining high front side reflection, minimizing glare from passing cars and providing enhanced protection against HEV light without the need for dual coatings, thus improving driver safety and aesthetic appeal.
Implementation Method 1
The materials are chosen such that one material has a refractive index of less than 1.6, e.g. silicon dioxide, SiO2, and the other material has a refractive index greater than 1.6, e.g. titanium dioxide, TiO2, or, zirconium dioxide, ZrO2. In addition, a conductive layer may be employed, such as indium tin oxide, as described in U.S. Pat. No. 6,852,406 to Marechal, or a thin metallic layer, such as 0.2 nm of Au, as described in U.S. Pat. No. 8,007,901 to Beinat, to impart anti-static properties to the coating.
Implementation Method 2
Such filters can be created in a variety of ways, including through physical vapor deposition, PVD, techniques. Coatings to reduce and control the reflection from the surface of a lens, referred to as antireflection, AR, coatings are commonly employed.
Data Source
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Figure 3A~3C
Figure 4A~4B
AI summary
An optical filter providing selective transmittance of target wavelengths of light and tunable, differential front and back surface reflectance.