Hybrid Optical Filter for Stable Near-Infrared Shielding
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Solution Overview
Problem
Existing optical filters for imaging devices face issues such as reduced visible light transmittance, spectral transmittance and reflectance changes with varying incident angles, stray light generation, and inadequate ultraviolet light shielding, which affect image quality and reproducibility.
Innovation Solution
An optical filter design comprising a dielectric multilayer film, a near-infrared absorbing glass substrate, and a resin film with near-infrared and ultraviolet absorbing dyes, ensuring high visible light transmittance, effective near-infrared shielding, minimal spectral changes at high angles, and reduced stray light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a reflection type filter using dielectric multilayer film is used to shield near-infrared light, then near-infrared shielding is improved, but spectral transmittance and reflectance change with varying incident angles causing image reproducibility issues
Solution Approach 1:
The patent combines dielectric multilayer films with absorption-type filtering materials (dyes or glass) to create a hybrid optical filter. The dielectric multilayer provides selective near-infrared reflection while the absorption material attenuates specific wavelength ranges. This composite structure achieves effective near-infrared shielding while maintaining stable spectral characteristics across varying incident angles, as the absorption component compensates for angle-dependent reflectance changes.
2Object-affected harmful factors
If a dye-based absorption filter is used to block near-infrared light, then near-infrared shielding is improved, but visible light transmittance decreases
Solution Approach 1:
The patent employs absorption materials (dyes or glass) with specifically tailored spectral absorption characteristics that target near-infrared wavelengths while being transparent or highly transmissive in the visible light region. By selecting materials whose absorption bands are localized to the near-infrared range, the filter achieves effective near-infrared blocking without compromising visible light transmission.
3Ease of manufacture
If conventional optical filters are used, then basic filtering function is provided, but stray light is generated due to reflection from lens and sensor surfaces
Solution Approach 1:
The patent converts potentially harmful reflected light into beneficial absorbed energy by incorporating broadband absorption materials (dyes or glass) that absorb reflected near-infrared and visible light. The absorption-type filtering material prevents reflected light from traveling back through the optical system, thereby eliminating stray light, flare, and ghost images while maintaining the desired spectral filtering function.
4Illumination intensity
If standard optical filters are used, then visible light transmission is maintained, but ultraviolet light reflection causes blue flare and ghost
Solution Approach 1:
The patent modifies the optical parameters of the filter by incorporating absorption materials with specific ultraviolet absorption characteristics. The dye or glass material is selected to absorb ultraviolet wavelengths while maintaining high transmittance in the visible region. This parameter change in the absorption spectrum eliminates ultraviolet reflection that would otherwise cause blue flare and ghost artifacts in images.
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 maintains excellent visible light transmittance and near-infrared shielding with minimal spectral changes and stray light, enhancing image quality and reproducibility, particularly under high incident angles.
Implementation Method 1
a reflection type filter in which dielectric thin films having different refractive indices are alternately laminated (dielectric multilayer film) on one surface or both surfaces of a transparent substrate 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 includes a near-infrared ray absorbing dye, an ultraviolet ray absorbing dye, and a resin. The optical filter satisfies all of the spectral characteristics (i-1) to (i-9).