Optical Filter Angular Color Correction via Volume-Weighted Absorption
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Solution Overview
Problem
Light-emitting devices, such as LEDs and OLEDs, exhibit significant angular dependence in emission intensity, leading to variations in perceived color when viewed from different angles, which affects their quality and requires filters with angle-dependent correction effects.
Innovation Solution
An optical filter with a transmission portion and an absorption portion, where the transmission portion has a larger volume than the absorption portion, and specific transmittance differences are maintained across various incidence angles to reduce angular dependence of emission intensity, using UV curable resins and light absorbers with strategically placed grooves for optimal color correction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional filter is used to correct color, then color accuracy at front view is improved, but angular dependence of emission intensity remains significant causing color shift at oblique viewing angles
Solution Approach 1:
The filter is designed with spatially varying properties: the absorption portion contains light absorbers concentrated in specific regions (particularly in the blue wavelength region around 450-480nm), while the transmission portion allows light passage. This local differentiation enables angle-dependent color correction, where the absorption portion compensates for increased blue light emission at oblique angles, and the transmission portion maintains overall light transmission efficiency.
Solution Approach 2:
The filter's optical parameters (transmittance and absorptance) are specifically engineered to vary with wavelength and incident angle. The absorption portion is designed to have wavelength-selective absorption characteristics that change with viewing angle, allowing the filter to dynamically adjust color balance based on the angle of incident light from the OLED.
2Measurement precision
If a filter layer is added to correct angular color shift, then color consistency is improved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The filter is segmented into distinct functional portions: an absorption portion containing light absorbers and a transmission portion allowing light passage. This segmentation allows each portion to be optimized for its specific function while simplifying the overall design compared to attempting to create a uniform filter with all required properties.
Solution Approach 2:
The filter employs composite material structure combining organic light absorbers (such as dyes or pigments) with a transparent matrix material. This composite approach enables tailored optical properties by selecting appropriate absorber compounds with specific absorption spectra, while the transparent matrix provides structural support and controlled transmittance.
3Adaptability or versatility
If the absorption portion volume is increased to enhance color correction, then angular dependence reduction is improved, but light transmission efficiency decreases
Solution Approach 1:
The absorption portion is designed with just sufficient absorption capacity to correct angular color shift without over-absorbing light. The light absorber concentration and distribution are optimized to provide exactly the needed correction for blue light emission variation at oblique angles, avoiding excessive absorption that would reduce overall luminance.
Solution Approach 2:
The optical parameters of the absorption portion (absorptance, concentration of light absorbers, path length) are precisely controlled to achieve the optimal balance between color correction and light transmission. By adjusting these parameters, the filter provides adequate blue light suppression at oblique angles while maintaining sufficient overall transmittance for high luminance output.
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 optical filter provides effective color correction for specific wavelength regions based on the angle of incident light, significantly reducing the angular dependence of emission intensity in light-emitting devices, ensuring consistent color perception across different viewing angles.
Implementation Method 1
an absorption portion absorbing light between a plane of incidence and a plane of emission
Implementation Method 2
a transmission portion transmitting light
Data Source
AI summary
An optical filter includes a transmission portion transmitting light and an absorption portion absorbing light between a plane of incidence and a plane of emission, and the volume of the transmission portion is larger than the volume of the absorption portion. For the optical filter, when the transmission spectrum S0 of light incident at an incidence angle of 0° and the transmission spectrum S60 of light incident at an incidence angle of 60° are superimposed, the transmittance (%) at an incidence angle of 60° is lower than the transmittance (%) at an incidence angle of 0° by 15% or more for a first wavelength band, and the difference between the transmittance (%) at an incidence angle of 60° and the transmittance (%) at an incidence angle of 0° is 10% or less for a second wavelength band.