Optical Filter Composite for Weather-Resistant Near-Infrared Shielding
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Solution Overview
Problem
Existing optical filters face issues with poor weather resistance, reduced transmissivity in the visible light region, and spectral transmittance changes due to varying incident angles, particularly in near-infrared light regions, which affect image reproducibility in imaging devices.
Innovation Solution
An optical filter configuration comprising a dielectric multilayer film, a near-infrared absorbing fluorophosphate glass, and a resin film with a near-infrared absorbing dye, ensuring minimal spectral characteristic changes at high incident angles and excellent shielding properties in the near-infrared region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a copper complex coating is used to absorb near-infrared light, then near-infrared shielding is achieved, but moisture resistance and weather resistance deteriorate
Solution Approach 1:
The patent combines multiple materials with different functions: a dielectric multilayer film for reflection, a glass substrate for structural support and UV absorption, and a resin film containing near-infrared absorbing dye for selective NIR absorption. This composite structure achieves both weather resistance and effective near-infrared shielding without the degradation issues of copper complex coatings.
2Object-affected harmful factors
If a dye is used to absorb near-infrared light, then near-infrared shielding is achieved, but visible light transmittance decreases
Solution Approach 1:
The resin film contains a near-infrared absorbing dye that selectively absorbs only in the near-infrared wavelength region (700-2500 nm) while maintaining high transmittance in the visible light region (380-700 nm). This localized absorption property allows the filter to shield near-infrared light without significantly reducing visible light transmission.
Solution Approach 2:
The patent specifies precise wavelength ranges for the dye's absorption characteristics, with the absorption peak positioned in the near-infrared region. By controlling the dye's absorption spectrum parameters, the filter achieves effective NIR shielding while preserving visible light transmittance above 50% in the 400-700 nm range.
3Object-affected harmful factors
If a dielectric multilayer film is used for reflection, then near-infrared shielding is achieved, but spectral transmittance changes at high incident angles
Solution Approach 1:
The patent combines three different light shielding mechanisms: reflection by the dielectric multilayer film, absorption by the glass substrate, and absorption by the resin film containing near-infrared absorbing dye. This multi-mechanism approach ensures that near-infrared light is effectively blocked regardless of incident angle, while visible light transmittance remains stable.
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 provides excellent weather resistance, high transmissivity in the visible light region, and effective near-infrared light shielding, particularly around 1200 nm, with minimal spectral changes even at high incident angles.
Implementation Method 1
a reflection type filter in which dielectric thin films having different refractive indices are alternately laminated on one surface or both surfaces of a transparent substrate (dielectric multilayer film) and light to be shielded is reflected by utilizing interference of light
Implementation Method 2
an absorption type filter in which light to be shielded is absorbed by using a glass or a dye that absorbs light in a specific wavelength region
Data Source
AI summary
An optical filter includes: a dielectric multilayer film 1; a substrate comprising a near-infrared ray absorbing glass and a resin film; and a dielectric multilayer film 2 in this order. The resin film comprises a near-infrared ray absorbing dye and a resin, the near-infrared ray absorbing glass is a fluorophosphate glass containing P, Cu, and F, and the optical filter satisfies all of the spectral characteristics (i-1) to (i-3), (i-5), and (i-13).