CMOS Image Sensor Charge Transfer Mediator for Leakage Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional CMOS image sensors face challenges in performing simultaneous electronic shutter operations due to voltage limitations and complex charge transfer processes, leading to charge leakage and unwanted exposure during electronic shutter operations.
Innovation Solution
A CMOS image sensor design with a photo-electric conversion device, amplification device, storage device, and transfer device, along with a drive circuit that controls signal transfer between these components to minimize charge leakage and simplify operations by using specific timing pulses and control pulses to manage charge transfer and exposure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If a storage part is provided between the photodiode and amplifier to enable electronic shutter operation, then simultaneous electronic shutter function is achieved for all pixels, but charge leakage occurs from the photodiode to the storage part during charge holding
Solution Approach 1:
An intermediate transfer part is introduced between the photodiode and storage part to control charge transfer. This transfer part acts as a mediator that can be selectively activated to prevent direct charge leakage while enabling controlled charge transfer during exposure and readout phases.
Solution Approach 2:
The charge transfer path is segmented into multiple stages: photodiode → transfer part → storage part → amplifier. This segmentation allows independent control of each stage, enabling the transfer part to be turned off during charge holding to prevent leakage while maintaining the electronic shutter function.
2Device complexity
If the photodiode and storage part are disposed adjacent to each other to simplify structure, then device complexity is reduced, but the storage part is directly exposed to light generating unwanted charges
Solution Approach 1:
The pixel structure is segmented into functionally separated regions: the photodiode for charge generation, the transfer part for controlled charge movement, and the storage part for charge holding. This segmentation allows the storage part to be physically positioned away from the light path while maintaining structural simplicity through systematic layout.
Solution Approach 2:
The transfer part serves as an intermediary that physically separates the photodiode from the storage part. This intermediate structure prevents direct light exposure of the storage part while enabling controlled charge transfer, thus eliminating unwanted charge generation without significantly increasing device complexity.
3Ease of operation
If charges are transferred via the transfer part and storage part even when electronic shutter operation is not needed, then charge transfer functionality is maintained, but the operation becomes complex
Solution Approach 1:
The transfer part is designed with dynamic controllability, allowing it to be turned on or off based on operational requirements. When electronic shutter operation is not needed, the transfer part can be kept in a default state that simplifies the charge transfer path, reducing operational complexity while maintaining necessary functionality.
Solution Approach 2:
The transfer part is designed to serve multiple functions: enabling electronic shutter operation when needed, and providing a simplified charge transfer path when not needed. This multi-functionality allows the same structure to adapt to different operational modes, reducing the need for separate circuits for different functions.
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 solution enables efficient electronic shutter operations with reduced charge leakage and unwanted exposure, simplifying the drive process and allowing for uniform shutter operation across the entire image sensor, even when not needed.
Implementation Method 1
a photo-electric conversion device which generates and accumulates a signal charge according to the amount of light from an object
Data Source
AI summary
An object of the present invention is to eliminate the influences of the leakage etc. of charges from a photodiode to a storage part during the electronic shutter operation. To achieve this object, the present invention includes: a photodiode which generates and accumulates a signal charge according to the amount of light from an object; an amplification part which amplifies a signal charge outputted from the photodiode and outputs the amplified signal to the outside; a storage part which temporarily stores the signal charge; and a transfer device which transfers the signal outputted from the photo-electric conversion device to the storage part via the amplification part.