Pixel-Sharing Image Sensor Circuit for Light Area and Drive Strength
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Solution Overview
Problem
In solid-state imaging elements with a pixel sharing type structure, the sharing of transistors among pixels leads to insufficient driving force due to narrow transistor gate widths, which affects optical characteristics like sensitivity, especially as pixel size decreases with miniaturization.
Innovation Solution
The implementation of a configuration where multiple transistors are connected in parallel and arranged in specific directions to enhance driving force, including amplification, selection, and reset transistors, while maintaining light receiving area sizes, and incorporating symmetrical transistor layouts to improve photo response non-uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If transistors are shared among multiple pixels to reduce the number of transistors per pixel, then the light receiving area can be increased, but the transistor gate width becomes narrow resulting in insufficient driving force
Solution Approach 1:
Multiple transistors (first transistor and second transistor) are connected in parallel to merge their driving capabilities. This allows the light receiving area to remain large while the combined transistors provide sufficient driving force through parallel connection, resolving the contradiction between area and power.
2Power
If the gate width of transistor is increased to improve driving force, then the sensitivity improves, but the light receiving area must be reduced
Solution Approach 1:
Instead of increasing the gate width of a single transistor (which would reduce light receiving area), the invention combines multiple transistors in parallel. Each transistor can maintain a smaller gate width that fits within the available area, while their combined effect provides the necessary driving force and sensitivity.
3Productivity
If pixel size is reduced for miniaturization, then the number of pixels increases, but the transistor driving force becomes even more insufficient
Solution Approach 1:
The parallel connection of multiple transistors within each pixel provides sufficient driving force even when pixel size is reduced for miniaturization. This allows high pixel density to be achieved while maintaining adequate transistor performance through the combined effect of parallel-connected transistors.
4Device complexity
If transistors are arranged between adjacent photodiodes to share them, then the transistor count per pixel decreases, but the transistor gate width is constrained
Solution Approach 1:
Multiple transistors are connected in parallel and share the same gate electrode structure. This merging approach allows the transistors to share space efficiently while providing sufficient total gate width for driving force, resolving the constraint between device complexity and gate width.
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 improves the driving force of transistors, enhances image quality, and maintains light receiving area sizes, addressing the issue of insufficient driving force and sensitivity in solid-state imaging elements.
Implementation Method 1
a plurality of first photoelectric conversion elements... a first transfer section configured to transfer electric charge from the plurality of first photoelectric conversion elements
Data Source
AI summary
A solid-state imaging element of a pixel sharing type with improved driving of transistors is disclosed. A first electric charge accumulating section and a second electric charge accumulating section are arranged in a predetermined direction. A first transfer section transfers electric charge from first photoelectric conversion elements to the first electric charge accumulating section, causing it to accumulate the electric charge. A second transfer section transfers electric charge from second photoelectric conversion elements to the second electric charge accumulating section, causing it to accumulate the electric charge. A first transistor is configured to output a signal corresponding to an amount of the electric charge accumulated in each of the first electric charge accumulating section and the second electric charge accumulating section. A second transistor is arranged with the first transistor in the predetermined direction and connected in parallel to the first transistor.