Gradient Refractive Index Anti-Reflection Composite
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Solution Overview
Problem
Existing anti-reflection films, such as multi-layer films and fine periodic structures, face challenges in reducing reflectance across a wide wavelength region while maintaining low reflection at interfaces, leading to issues like ghosting and flare in imaging systems due to residual reflection.
Innovation Solution
A composite structure featuring a gradient refractive index thin film with a refractive index change in the film thickness direction, combined with a fine structure arranged at a pitch shorter than visible light wavelengths, is used to reduce reflection. This structure includes an adhesive layer for the fine structure on the gradient refractive index thin film, minimizing refractive index differences at interfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a multi-layer film-type anti-reflection film is used to suppress reflectance over a wide wavelength region, then the reflectance is reduced, but the structure requires a substantial number of layers and complicates the design
Solution Approach 1:
The patent divides the anti-reflection function into two separate components: a gradient refractive index thin film that provides continuous refractive index transition, and a fine structure layer with sub-wavelength features that further suppresses reflection. This segmentation allows each layer to be optimized independently, reducing the total number of layers needed compared to traditional multi-layer films.
Solution Approach 2:
The patent employs a gradient refractive index thin film where the refractive index changes continuously from the substrate to the air interface. This continuous parameter change eliminates the need for multiple discrete layers with different refractive indexes, simplifying the overall structure while maintaining effective broadband anti-reflection performance.
2Reliability
If the density of ND filters is increased to reduce light transmittance for high sensitivity imaging, then the diaphragm aperture can be prevented from becoming too small, but the reflectance of the filter increases causing ghost and flare
Solution Approach 1:
The patent creates a composite structure combining an ND filter with a gradient refractive index thin film and a fine structure layer. This composite design allows the ND filter to maintain its light-absorbing function while the additional layers work together to suppress reflection, eliminating ghost and flare issues even at high ND densities.
Solution Approach 2:
The patent converts the harmful reflection effect into a beneficial anti-reflection function by adding the gradient refractive index thin film and fine structure layer. These layers are specifically designed to reduce the reflectance of the ND filter, transforming the problematic reflection into an enhanced anti-reflection performance that improves image quality.
3Object-affected harmful factors
If a fine periodic structure is used as an anti-reflection structure, then the anti-reflection wavelength region is expanded, but light reflection occurs at the interface between the structure and substrate
Solution Approach 1:
The patent introduces a gradient refractive index thin film as an intermediary layer between the substrate and the fine structure. This intermediate layer provides a continuous refractive index transition, eliminating the abrupt interface that causes reflection. The gradient film acts as a mediator that smoothly connects the optical properties of the substrate and the fine structure, preventing interface reflection.
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 solution significantly reduces reflection, minimizing ghosting and image degradation in imaging systems, particularly in diaphragm devices, by effectively managing light absorption and transmission across a wide wavelength range.
Implementation Method 1
a gradient refractive index thin film with refractive index change in the film thickness direction formed on the substrate
Implementation Method 2
a fine structure having many fine parts arranged at a pitch shorter than the wavelength of visible light is formed on the gradient refractive index thin film
Implementation Method 3
This structure includes an adhesive layer for the fine structure on the gradient refractive index thin film, minimizing refractive index differences at interfaces
Data Source
AI summary
There is provided an optical filter or an anti-reflection structure with lower reflection in comparison with the conventional ones by comprising a gradient refractive index thin film 12 with continuous, periodic refractive index change in the film thickness direction and a fine periodic structure 151 lowering reflection, wherein the refractive index of the gradient refractive index thin film 12 in its thickness direction on the substrate side changes so as to become close to that of the substrate, while on the fine periodic structure 111 changes so as to become close to that of the fine periodic structure 151. The optical filter can be used in an optical device or an electronic device display.