Image Sensor Charge Transfer Paths for Global and Rolling Shutter
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Solution Overview
Problem
Image sensors driven in a global electronic shutter mode face difficulties in performing signal readout using a rolling electronic shutter mode, as existing technologies struggle to synchronize accumulation and readout processes across all rows simultaneously.
Innovation Solution
The image sensor incorporates a photoelectric conversion unit, a holding unit, an accumulation unit, a first transfer path, and a second transfer path to manage electric charges generated by the photoelectric conversion unit, allowing for both global and rolling electronic shutter operations by controlling the transfer and readout of charges through multiple pathways.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If an image sensor is driven in a global electronic shutter mode, then simultaneous charge accumulation across all rows is achieved, but rolling electronic shutter mode operation becomes difficult
Solution Approach 1:
The transfer path is divided into two separate paths: a first transfer path for direct charge transfer from photoelectric conversion units to accumulation units, and a second transfer path for charge transfer via holding units. This segmentation allows the system to support both global shutter mode (using first transfer path) and rolling shutter mode (using second transfer path) operations, resolving the contradiction between shutter mode compatibility and device complexity
Solution Approach 2:
The dual transfer path configuration enables the image sensor to perform multiple functions: it can operate in global electronic shutter mode using the first transfer path for simultaneous charge accumulation, and in rolling electronic shutter mode using the second transfer path for sequential row-by-row charge transfer. This multi-functionality allows a single device to adapt to different shutter mode requirements without sacrificing complexity
2Productivity
If charges are accumulated in the accumulation unit from multiple photoelectric conversion units, then signal readout efficiency is improved, but charge transfer time and potential data loss increase
Solution Approach 1:
The holding unit serves as a preliminary storage stage that temporarily holds charges from photoelectric conversion units before they are transferred to the accumulation unit. This preliminary action allows charges to be staged and transferred in an organized manner, improving readout efficiency while managing transfer time effectively and preventing data loss during the transfer process
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 enables simultaneous accumulation and readout across all rows in global shutter mode and efficient row-by-row operations in rolling shutter mode, enhancing operational flexibility and dynamic range, while allowing for earlier start of photoelectric conversion in subsequent frames.
Implementation Method 1
a photoelectric conversion unit that photoelectrically converts light to generate an electric charge
Data Source
AI summary
An image sensor includes: a photoelectric conversion unit that photoelectrically converts light to generate an electric charge; a holding unit that holds the electric charge generated by the photoelectric conversion unit; an accumulation unit that accumulates the electric charge generated by the photoelectric conversion unit; a first transfer path that transfers the electric charge generated by the photoelectric conversion unit to the accumulation unit; and a second transfer path that transfers the electric charge generated by the photoelectric conversion unit to the accumulation unit via the holding unit.