Meta-Photodiode Pixel Layout for Filterless Color Imaging
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Solution Overview
Problem
Image sensors face challenges in achieving high light utilization efficiency due to the use of color filters, which absorb most of the incident light, and in achieving high resolution due to pixel size limitations and under-sampling in color separation methods.
Innovation Solution
The implementation of a pixel array with meta-photodiodes that selectively absorb different wavelength bands of light, arranged in a specific configuration to optimize light absorption and maintain uniform absorption spectra across the pixel array, eliminating the need for color filters and enhancing resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a color filter is used to sense color, 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 within the photodiode structure through selective wavelength absorption materials. This eliminates the 2/3 light loss caused by traditional color filters while maintaining color detection capability.
Solution Approach 2:
The patent replaces the mechanical/optical color filter system with a material-based selective absorption mechanism at the photodiode level. Instead of using a physical color filter layer to block unwanted wavelengths, the invention uses materials with specific bandgaps to selectively absorb certain wavelength ranges, achieving color separation without the energy loss of traditional filtering.
2Measurement precision
If meta-photodiodes are arranged with small spacing to improve resolution, then resolution is enhanced, but absorption spectra uniformity across the array may be affected
Solution Approach 1:
The patent carefully controls and optimizes the spacing parameter between meta-photodiodes to maintain both high resolution and uniform absorption spectra. By setting the spacing to be at least half the sum of the widths of adjacent photodiodes, the invention ensures sufficient optical isolation while maintaining compact pixel structures. This parameter optimization allows sub-150nm spacing that enhances resolution without compromising spectral uniformity across the array.
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 improves light utilization efficiency and enables high-resolution color detection without the limitations of traditional color filters, allowing for full-color pixel functionality and uniform absorption spectra regardless of incident light angles.
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
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.