Gradient Refractive Index Infrared Filter for Color Shift Reduction
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Solution Overview
Problem
Conventional infrared filters cause color shift and warpage in optical systems due to their design, especially when the chief ray angle increases, leading to distorted image color reproduction and manufacturing inefficiencies.
Innovation Solution
An infrared filter with a multilayer film structure on a transparent substrate, featuring film layers with gradient refractive indexes and composite materials, which reduces color shift, internal stress, and manufacturing costs while improving transmittance and manufacturing yield.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional infrared filters use alternate film layers of high and low refractive index materials, then infrared light can be filtered out, but color shift and warpage occur in peripheral regions when chief ray angle increases
Solution Approach 1:
The patent changes the refractive index parameters of the film layers by introducing four distinct refractive index levels (NA, NB, NC, ND) arranged in gradient order, replacing the conventional alternating high-low pattern. This parameter optimization reduces color shift and warpage while maintaining infrared filtering effectiveness.
Solution Approach 2:
The patent employs composite material structures with at least two kinds of film layers made of composite materials, combining different material properties to achieve both infrared filtering and reduced optical distortion. The composite materials allow for tailored refractive indices and stress characteristics.
2Object-affected harmful factors
If multilayer coating with high layer count is applied, then infrared filtering performance improves, but warpage increases due to uneven internal stress
Solution Approach 1:
The patent optimizes the refractive index parameters across the four film layer types to achieve a gradient distribution that balances infrared filtering capability with internal stress uniformity. This parameter design allows high layer count without excessive warpage.
Solution Approach 2:
The patent assigns different refractive index characteristics to different regions of the multilayer structure, with each film layer type (first, second, third, fourth kind) having specific refractive index ranges. This local differentiation optimizes both filtering performance and stress distribution.
3Ease of manufacture
If conventional infrared filter design is used, then manufacturing process is simple, but color shift occurs in peripheral regions
Solution Approach 1:
The patent establishes specific refractive index parameter ranges for each film layer type, providing clear manufacturing guidelines. The gradient arrangement of refractive indices (NA > NB > NC > ND) offers a systematic approach that maintains manufacturability while eliminating color shift.
Solution Approach 2:
The use of composite materials with specific refractive index characteristics allows the patent to achieve superior color reproduction while maintaining compatibility with conventional manufacturing processes. The composite structure provides the necessary optical properties without requiring entirely new fabrication techniques.
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 filter effectively filters out infrared light, minimizing color shift and warpage, enhancing image quality and manufacturing efficiency by using a multilayer film structure with specific refractive index gradients and composite materials.
Implementation Method 1
an infrared-filtering multilayer film... effectively filters out infrared light
Implementation Method 2
the four kinds of film layers are arranged in order of gradient refractive indexes
Data Source
AI summary
An infrared filter includes a transparent substrate, and an infrared-filtering multilayer film. The infrared-filtering multilayer film is coated on the transparent substrate, and the infrared-filtering multilayer film includes a plurality of the first kind of film layers, a plurality of the second kind of film layers, a plurality of the third kind of film layers and a plurality of the fourth kind of film layers, wherein the four kinds of film layers are arranged in order of gradient refractive indexes. At least two kinds of film layers are made of composite materials.