Meta-Photodiode Pixel Layout for Filterless Color Separation
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Solution Overview
Problem
Image sensors face challenges in light utilization efficiency due to color filters, which absorb most incident light, and struggle with high-resolution color separation as pixel sizes decrease, leading to resolution degradation and under-sampling issues.
Innovation Solution
The use of a pixel array with meta-photodiodes arranged in a specific configuration, where each pixel includes a first, second, and third meta-photodiode to absorb different wavelength bands, arranged within a size less than the diffraction limit, with uniform absorption spectra in both central and peripheral areas, allowing for efficient light absorption and color separation without a color filter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a color filter is used for color separation, then color detection is enabled, but light utilization efficiency is reduced to about 33%
Solution Approach 1:
The patent removes the color filter component from the optical path and extracts only the necessary light absorption function, implementing it directly in the photodiode structure through selective bandgap materials. This eliminates the 2/3 light absorption loss inherent in color filter-based systems while maintaining color separation capability.
Solution Approach 2:
The patent replaces the mechanical/optical color filter system with a semiconductor-based photodiode system that uses electronic bandgap properties for wavelength-selective absorption. This substitution enables direct conversion of optical energy to electrical signals with higher efficiency while maintaining spectral discrimination.
2Area of stationary object
If meta-photodiodes are arranged with small spacing for compact design, then device area is reduced, but absorption spectra uniformity across different chief ray angles deteriorates
Solution Approach 1:
The patent applies different structural optimizations to different regions of the pixel array. Central pixels (receiving near-vertical light) and peripheral pixels (receiving oblique light) are designed with adjusted meta-photodiode spacing and orientation to compensate for angle-dependent absorption variations, ensuring uniform spectral response across the entire array despite compact overall dimensions.
Solution Approach 2:
The patent introduces adjustable and adaptive parameters in the meta-photodiode design, including variable spacing, orientation angles, and depth positions, that can be optimized for different chief ray angles. This dynamic design approach allows the system to maintain absorption spectra uniformity across varying light incidence conditions while keeping the pixel area compact.
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
This configuration enhances light utilization efficiency and enables high-resolution color detection by ensuring uniform absorption spectra across different chief ray angles, reducing the need for color filters and minimizing resolution degradation.
Implementation Method 1
a first meta-photodiode configured to selectively absorb light of a first wavelength band; a second meta-photodiode configured to selectively absorb light of a second wavelength band different from the first wavelength band; and a third meta-photodiode configured to selectively absorb light of a third wavelength band different from the first wavelength band and second wavelength band
Data Source
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AI summary
An image sensor may include a pixel array including a plurality of two-dimensionally arranged pixels. Each pixel may include a first meta-photodiode absorbing light of a first wavelength band; a second meta-photodiode absorbing light in a second wavelength band; and a third meta-photodiode absorbing light of a third wavelength band, wherein the first meta-photodiode, the second meta-photodiode, and the third meta-photodiode may be arranged in an area having a size less than a diffraction limit. The arrangement form of the first meta-photodiode, the second meta-photodiode, and the third meta-photodiode arranged in the plurality of pixels in a central portion of the pixel array may be the same as the arrangement form of the first meta-photodiode, the second meta-photodiode, and the third meta-photodiode arranged in the plurality of pixels in a periphery of the pixel array.