Clear Filter Pixels for Noise Reduction in Image Sensors
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Solution Overview
Problem
Conventional imaging systems face limitations in miniaturization due to signal-to-noise ratio (SNR) constraints, particularly in low light conditions, where increasing light exposure amplifies noise through color correction matrices, compromising image quality.
Innovation Solution
An imaging system with an array of pixels including red, blue, and clear image pixels that generate white signals across a broader light spectrum, coupled with processing circuitry performing chroma filtering and weighted sum operations to reduce noise correlations and enhance SNR, allowing for improved noise reduction and image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If clear image pixels are used to increase light exposure and improve SNR, then signal-to-noise ratio is improved, but noise amplification occurs during color correction transformation
Solution Approach 1:
The patent applies chroma filtering to clear image pixel data before performing color correction transformation. By pre-processing the data to reduce noise correlations in the chroma channels, the subsequent color correction matrix operation amplifies less noise, thereby maintaining improved SNR while minimizing noise amplification artifacts
Solution Approach 2:
The patent introduces an intermediate processing step (chroma filtering) between data capture and color correction. This intermediary operation processes the clear image pixel data to establish noise correlations that prevent harmful noise amplification during the color transformation, acting as a mediator between the clear pixel output and the final RGB image
2Area of stationary object
If image sensor size is reduced for miniaturization, then device size is reduced, but signal-to-noise ratio deteriorates due to smaller pixel area
Solution Approach 1:
The patent makes clear image pixels serve multiple functions: they capture luminance information like traditional pixels while also providing enhanced signal strength for noise reduction. By processing these clear pixel data through chroma filtering and color correction, the system achieves both miniaturization and maintained SNR, as the clear pixels effectively perform both luminance capture and noise reduction roles
Solution Approach 2:
The patent changes the spectral response parameter of certain pixels to be broadband (clear pixels) rather than narrowband (traditional RGB pixels). This parameter change allows smaller pixels to capture more photons across the visible spectrum, improving the signal component of SNR even as pixel area decreases, thereby enabling miniaturization without SNR penalty
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 system effectively increases the signal-to-noise ratio and reduces noise amplification, enabling better image quality and miniaturization of image sensors by leveraging the broader spectral response of clear image pixels and advanced processing techniques.
Implementation Method 1
clear image sensor pixels that generate white image signals in response to at least red light, green light, and blue light
Data Source
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AI summary
An image sensor may have an array of image sensor pixels arranged in color filter unit cells each having one red image pixel that generates red image signals, one blue image pixel that generate blue image signals, and two clear image sensor pixels that generate white image signals. The image sensor may be coupled to processing circuitry that performs filtering operations on the red, blue, and white image signals to increase noise correlations in the image signals that reduce noise amplification when applying a color correction matrix to the image signals. The processing circuitry may extract a green image signal from the white image signal. The processing circuitry may compute a scaling value that includes a linear combination of the red, blue, white and green image signals. The scaling value may be applied to the red, blue, and green image signals to produce corrected image signals having improved image quality.