Shared Floating Diffusion Pixel Readout for Selective Signal Access
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Solution Overview
Problem
Current image sensors face challenges in efficiently reading out signals from pixel arrays with multiple photoelectric conversion elements sharing a floating diffusion area, which affects their performance in converting optical images into electrical signals effectively.
Innovation Solution
The image sensor design includes a pixel array with sub-pixels that share a floating diffusion area and are driven by a row driver, which generates and controls drive signals for reading out signals from the photoelectric conversion elements, utilizing micro lenses to overlap the photoelectric conversion elements and define readout areas based on preset modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If multiple photoelectric conversion elements share a floating diffusion area, then device complexity is reduced and manufacturing is simplified, but signal reading efficiency deteriorates due to difficulty in selectively reading out signals from specific elements
Solution Approach 1:
The pixel array is divided into multiple readout areas, and within each pixel, individual photoelectric conversion elements can be selectively accessed. Transmission gates are used to segment the signal paths from each photoelectric conversion element to the shared floating diffusion area, enabling selective reading of signals from specific elements while maintaining the shared floating diffusion structure.
Solution Approach 2:
The row driver dynamically controls transmission gates to enable flexible readout modes. The system can switch between reading all elements, reading specific subsets of elements, or combining signals from different elements in real-time based on imaging requirements, making the readout process adaptive and efficient.
2Manufacturing precision
If a shared floating diffusion area is used by multiple photoelectric conversion elements, then manufacturing precision requirements are reduced, but the ability to perform selective signal reading deteriorates
Solution Approach 1:
Transmission gates serve as intermediary components between photoelectric conversion elements and the shared floating diffusion area. These gates enable selective connection and disconnection of signal paths, allowing the system to control which elements' signals are read out while maintaining the simplified shared floating diffusion structure.
3Adaptability or versatility
If variable readout modes are implemented, then adaptability and versatility are improved, but device complexity increases due to additional control mechanisms
Solution Approach 1:
The row driver is designed with multi-functionality to handle various readout modes using a unified control architecture. The same transmission gates and floating diffusion area are used across different readout modes (full readout, partial readout, signal combination modes), reducing the need for dedicated hardware for each mode while maintaining versatility.
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 design enhances the efficiency of signal reading and conversion, improving the performance of image sensors by allowing for variable readout modes and efficient charge summing across the pixel array, thereby improving image data acquisition.
Implementation Method 1
a micro lens disposed to overlap the plurality of photoelectric conversion elements
Implementation Method 2
each of the plurality of sub-pixels includes a plurality of photoelectric conversion elements sharing a floating diffusion area with each other
Data Source
AI summary
An image sensor is provided. The image sensor includes: a pixel array including a plurality of pixels arranged along rows and columns; and a row driver which drives the plurality of pixels for each of the rows, wherein each of the plurality of pixels includes a plurality of sub-pixels, each of the plurality of sub-pixels includes a plurality of photoelectric conversion elements sharing a floating diffusion area with each other, and a micro lens disposed to overlap the plurality of photoelectric conversion elements, a readout area is defined on the pixel array in accordance with a preset readout mode, and the row driver generates a drive signal for reading out signals provided from a photoelectric conversion element included in the readout area from among the plurality of photoelectric conversion elements, and provides the drive signal to the pixel array.