Dielectric Multilayer Optical Filter for Angle-Dependent Color Uniformity
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Solution Overview
Problem
In thinning imaging devices, the reduced distance between the lens and optical filter member leads to larger differences in light incident angles, causing color tone differences between the central and peripheral regions of captured images, affecting image quality, and there is a need to enhance light transmission within the visible wavelength range to improve image quality.
Innovation Solution
An optical filter member with a base and an optical film comprising first, second, and third dielectric multilayer films, where the second and third films have higher average refractive indices than the first, and are strategically positioned to reduce angle-dependent optical characteristics and block specific wavelengths, ensuring consistent light transmission across the visible spectrum.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the distance between the lens and the optical filter member is reduced to thin the imaging device, then the device thickness is reduced, but the difference in light incident angles between central and peripheral regions increases causing color tone differences
Solution Approach 1:
The optical film is segmented into three distinct dielectric multilayer films (first, second, and third) with different refractive indexes and optical characteristics. Each film is designed with specific layer structures and materials to independently control different aspects of light transmission and reflection, allowing the system to maintain color tone uniformity across different incident angles while keeping the device thin.
Solution Approach 2:
Different regions of the optical film have different local optical properties. The first dielectric multilayer film has a specific light transmission range, the second film has a different transmission range with higher refractive index, and the third film blocks specific wavelengths. This local differentiation of optical properties allows each region to compensate for angle-dependent color shifts, maintaining overall color uniformity despite varying incident angles.
2Device complexity
If a single dielectric multilayer film is used in the optical filter member, then the structure is simpler, but the light transmission range and color tone uniformity across different incident angles are insufficient
Solution Approach 1:
The optical film uses composite dielectric materials with different refractive indexes arranged in three distinct multilayer films. The first film uses dielectric layers with specific refractive indexes for baseline filtration, the second film uses higher refractive index materials to enhance angle insensitivity, and the third film adds additional wavelength-selective blocking. This composite structure achieves superior color tone uniformity and transmission characteristics that cannot be obtained with a single dielectric multilayer film.
3Manufacturing precision
If the optical film has high transmittance in the visible light range to enhance image quality, then the image quality improves, but the ability to block unwanted wavelengths (including infrared and specific visible ranges) may be compromised
Solution Approach 1:
The wavelength control function is segmented across three different dielectric multilayer films, each responsible for specific wavelength ranges. The first film handles the primary visible light transmission, the second film enhances transmission in specific visible ranges while blocking others, and the third film provides additional blocking for infrared and specific visible wavelengths. This segmentation allows high transmittance in desired visible ranges while effectively blocking unwanted wavelengths.
Solution Approach 2:
The optical characteristics of the three dielectric multilayer films are optimized with different parameters including refractive indexes, layer thicknesses, and material compositions. The first film has specific optical parameters for baseline performance, the second film has higher refractive index parameters to reduce angle sensitivity, and the third film has parameters optimized for blocking specific wavelengths. These parameter variations enable simultaneous achievement of high visible light transmission and effective unwanted wavelength blocking.
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 effectively reduces optical characteristic changes due to light angle differences and enhances image quality by maintaining a desired light transmission range, thereby improving the color consistency and clarity of images captured by the imaging device.
Implementation Method 1
an optical film disposed on a surface of the base, the optical film including a first, a second and a third dielectric multilayer films, in the respective multilayer films a plurality of dielectric layers having different refractive indexes being laminated
Implementation Method 2
The second dielectric multilayer film having a second light transmission range falling within the first light transmission range and having an average refractive index higher than that of the first dielectric multilayer film
Data Source
AI summary
An optical filter member includes a transparent base; and an optical film disposed on a surface of the base. The optical film includes a first, a second and a third dielectric multilayer films, in the respective multilayer films a plurality of dielectric layers having different refractive indexes being laminated. The first dielectric multilayer film has a first light transmission range within a wavelength of visible light. The second dielectric multilayer film has a second light transmission range falling within the first light transmission range and has an average refractive index higher than that of the first dielectric multilayer film. The third dielectric multilayer film blocks light having twice a wavelength of a central wavelength of the second light transmission range. The second dielectric multilayer film is disposed, together with the first dielectric multilayer film or the third dielectric multilayer film, on a same main surface side of the base.