Image Sensor Pixel Layout for Faster Phase Difference Readout
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Solution Overview
Problem
Current image sensors with 6×6 unit pixel groups face challenges in extracting phase differences due to uneven numbers of pixels, making it difficult to distinguish color differences from phase differences caused by micro-lenses, which affects readout speed and accuracy.
Innovation Solution
Incorporating a center pixel group with 2×2 pixels of different colors and surrounding color pixel groups, along with dual gain conversion transistors, to enable 4-sum or 8-sum mode operations, allowing for increased readout speed by using existing 2×2 driving modes and symmetric micro-lens arrangements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a 6x6 unit pixel group with uneven pixel distribution is used, then color filtering can be implemented, but phase difference detection becomes difficult and readout speed is limited
Solution Approach 1:
The pixel array is segmented into multiple 6x6 unit pixel groups, each containing a center pixel group (2x2 pixels) and surrounding color pixel groups. This segmentation allows different regions to serve different functions: the center region for phase difference detection and the surrounding regions for color imaging, resolving the contradiction between detection accuracy and readout speed
Solution Approach 2:
The patent introduces a spatial dimension solution by arranging pixels in a specific 6x6 geometric pattern with a centered 2x2 group. This dimensional arrangement enables simultaneous achievement of color filtering (through surrounding pixels) and phase difference detection (through center pixels), while the structured layout facilitates parallel readout operations that improve readout speed
2Adaptability or versatility
If 2x2 pixel driving mode is used, then device compatibility is maintained, but readout speed is constrained
Solution Approach 1:
The 6x6 unit pixel group design is universally compatible with existing 2x2 pixel driving modes while enabling additional functionality. The center 2x2 pixels can operate in traditional modes for compatibility, while the complete 6x6 structure enables 4-sum and 8-sum modes for enhanced readout speed, making the system multi-functional and adaptable to different operating requirements
Solution Approach 2:
The patent implements dynamic operation modes that can switch between 2x2 pixel driving (for compatibility) and 4-sum/8-sum modes (for high-speed readout). This dynamic flexibility allows the system to adapt its readout strategy based on application requirements, maintaining compatibility while enabling high-speed operation when needed
3Measurement precision
If floating diffusion nodes are selectively coupled, then color differentiation accuracy improves, but circuit complexity increases
Solution Approach 1:
Multiple floating diffusion nodes that process the same color information are selectively coupled together through dual gain conversion transistors. This merging combines signals from multiple pixels of the same color, improving color differentiation accuracy through signal integration while using shared circuitry to manage complexity
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 the readout speed of the image sensor by up to 150% by enabling efficient phase difference detection and improved color differentiation, facilitating faster data processing in image sensors.
Implementation Method 1
a dual gain conversion transistor suitable for selectively coupling the first floating diffusion node to the second floating diffusion node
Implementation Method 2
a first sub-color pixel group including a plurality of first photodiodes
Data Source
AI summary
Disclosed is an image sensor including: a center pixel group including 2×2 pixels having different colors in a center area of a 6×6 unit pixel group; and first to fourth color pixel groups having the same color as one pixel of the center pixel group, disposed as units of 2×4 pixels or 4×2 pixels to have a shape surrounding the center pixel group, and having different colors.