Resin-Dielectric Composite Optical Filter for High-Angle Stability
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Solution Overview
Problem
Existing optical filters using dielectric multilayer films suffer from changes in spectral transmittance and reflectance curves due to varying incident angles, leading to ripples and stray light, which degrade image quality, especially in camera modules with reduced height and high incident angles.
Innovation Solution
An optical filter configuration comprising a first dielectric multilayer film, a resin film with a dye, and a second dielectric multilayer film, where the resin film has a maximum absorption wavelength between 690 nm to 800 nm, and the dielectric films have specific refractive indices and quarter wave optical thicknesses, ensuring consistent transmittance and reflectance characteristics across different incident angles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a dielectric multilayer film is used to shield near-infrared light, then near-infrared shielding is achieved, but spectral transmittance and reflectance curves change with incident angle causing ripples and stray light
Solution Approach 1:
The patent combines a resin film containing a near-infrared absorbing dye with dielectric multilayer films to create a composite optical filter. The resin film absorbs near-infrared light through molecular absorption, while the dielectric multilayer films provide visible light interference control. This composite structure achieves reliable near-infrared shielding without the spectral curve variations and stray light problems caused by dielectric multilayer films alone.
2Length of moving object
If the camera module height is reduced, then compactness is improved, but incident angle increases causing stronger ripple generation and degraded image quality
Solution Approach 1:
The patent converts the harmful effect of high incident angles into a beneficial outcome by using the resin film's absorption characteristics. The resin film absorbs near-infrared light regardless of incident angle, and its optical properties remain stable at high angles. This allows the optical filter to maintain excellent performance in compact camera modules where high incident angles are inevitable.
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 prevents ripples and stray light in the visible light region while maintaining high transmittance in the visible light region and effective shielding in the near-infrared light region, even at high incident angles.
Implementation Method 1
the resin film includes a resin and a dye having a maximum absorption wavelength in 690 nm to 800 nm in the resin
Implementation Method 2
light desired to be shielded is reflected using interference of light
Implementation Method 3
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
Data Source
AI summary
An optical filter includes a first dielectric multilayer film, a resin film, a phosphate glass, and a second dielectric multilayer film. The second dielectric multilayer film includes at least one H2 layer satisfying a refractive index of 1.8 or more and 2.5 or less and a QWOT of 1.1 or more and 3.5 or less, when a layer closest to the phosphate glass in the H2 layers is defined as a first H2 layer, the second dielectric multilayer film comprises a first M2 layer comprising a single layer satisfying a QWOT of 1.2 or more and 1.8 or less or a plurality of layers satisfying a total QWOT of 1.2 or more and 1.8 or less between the first H2 layer and the phosphate glass, and the optical filter satisfies all of the spectral characteristics (i-1) to (i-4).