CMOS Image Sensor Bank Segmentation for Noise Reduction
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Solution Overview
Problem
High-speed solid-state imaging devices face challenges in minimizing noise due to simultaneous driving of overflow gates, which can distort images and disrupt signal reading, especially in applications requiring high frame rates and high-definition imaging.
Innovation Solution
A CMOS image sensor with a control unit that manages the operation of overflow gates to minimize noise by transferring charge to charge accumulation sections through a different route, allowing for sequential reading out and resetting, and using dummy rows to reduce the impact of overflow gate driving on image signal processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If simultaneous driving of overflow gates is carried out for all rows to discharge charge from photodiodes, then the degree of freedom in exposure time is improved, but noise is generated due to IR drop and signal line coupling
Solution Approach 1:
The pixel array is divided into multiple banks, and the overflow gate driving is segmented to operate on different banks at different times. This allows the system to maintain the flexibility of simultaneous driving while reducing noise by limiting the scope of simultaneous operations to smaller subsets of pixels rather than the entire array.
Solution Approach 2:
The overflow gate driving is implemented as periodic row-by-row operations instead of continuous simultaneous driving. Each row is driven sequentially through the banks in a periodic manner, which reduces noise while maintaining the ability to control exposure timing flexibly.
2Reliability
If simultaneous transfer driving for all rows is carried out to charge accumulation sections, then simultaneity of accumulation periods is improved, but reading out time becomes longer
Solution Approach 1:
The pixel array is divided into multiple banks that can be read out independently and in parallel. This segmentation allows the system to maintain simultaneity of accumulation periods across the entire array while reducing the total reading out time by processing multiple banks simultaneously through separate readout paths.
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 enables high simultaneity in exposure time while minimizing noise and distortion, improving image quality in high-speed and high-definition imaging applications.
Implementation Method 1
a light reception element for receiving light to generate charge as a reception light signal
Data Source
AI summary
A solid-state imaging device includes first and second sets of pixels. The first pixels have light reception elements and a discharging unit that discharges charge corresponding to light received by the first pixels. The second pixels have corresponding light reception elements but are covered with a light shielding film. Signals stored in the second light reception elements are read to a next stage when the discharging units corresponding to the first light reception elements are enabled.