Scaled Filter Array In-Pixel Binning for Automotive Image Sensors
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Solution Overview
Problem
Image sensors with Bayer-pattern color filters face challenges in low-light scenes due to color artifacts caused by binning and difficulty in in-pixel binning, especially in automotive applications requiring increased pixel resolution without compromising light sensitivity.
Innovation Solution
The use of scaled filter arrays and charge-domain binning on the floating diffusion node, where larger color filters cover multiple pixels and share charge onto a common floating diffusion node, maximizing signal-to-noise ratio and light sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If Bayer-pattern color filters are used with binning to capture low-light scenes, then light sensitivity is improved, but color artifacts occur due to aliasing
Solution Approach 1:
The pixel array is segmented into color-specific groups (red pixels, green pixels, blue pixels) that are spatially separated and can be independently binned. This segmentation allows charge from pixels of the same color to be combined without mixing colors, thereby improving light sensitivity while avoiding color artifacts that would result from aliasing.
2Ease of operation
If pixels of the same color are placed next to each other to enable in-pixel binning, then charge sharing onto floating diffusion node becomes possible, but traditional Bayer-pattern layout must be changed
Solution Approach 1:
The pixel array layout is designed to be dynamically configurable, allowing pixels to be grouped into color-specific blocks that can be selectively activated for binning operations. This dynamic arrangement enables in-pixel binning by bringing same-color pixels adjacent to each other within each block, while maintaining the ability to switch between different operational modes.
3Measurement precision
If pixel size is reduced to increase resolution in automotive applications, then pixel resolution is improved, but light sensitivity decreases
Solution Approach 1:
Multiple small pixels of the same color within each block are merged by combining their charge signals onto a shared floating diffusion node. This merging process effectively creates a larger virtual pixel with equivalent light-sensitive area, thereby maintaining high light sensitivity despite using physically smaller pixels to achieve higher resolution.
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 approach enhances light sensitivity and maintains or exceeds the sensitivity of current generation large-pixel sensors while achieving higher resolution, suitable for next-generation automotive imagers.
Implementation Method 1
Each color filter has a different photoresponse and is optically coupled to a corresponding group of individual pixels
Implementation Method 2
individual pixels... that convert incident photons to electrical charge
Implementation Method 3
individual pixels... that convert incident photons to electrical charge
Implementation Method 4
charge-domain binning on the floating diffusion node, where larger color filters cover multiple pixels and share charge onto a common floating diffusion node
Data Source
AI summary
Embodiments of an apparatus including a pixel array including a plurality of individual pixels grouped into pixel kernels having two or more individual pixels, wherein each pixel kernel includes a floating diffusion electrically coupled to all individual pixels in the kernel. A color filter array (CFA) is positioned over and optically coupled to the pixel array, the CFA comprising a plurality of tiled minimal repeating units, each including a plurality of scaled filters having a photoresponse selected from among two or more different photoresponses. Individual pixels within each pixel kernel are optically coupled to a scaled filter. Circuitry and logic coupled to the pixel array cause the apparatus to operate in a first mode wherein signals from a subset of individual pixels are individually transferred to their floating diffusion and read, resulting in a high-resolution, low-sensitivity sub-image and a second mode wherein signals from individual pixels in every pixel kernel are binned into the kernel's floating diffusion and read, resulting in a low-resolution, high-sensitivity image.