Imaging Pixel Charge Transfer Path Segmentation
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Solution Overview
Problem
Conventional imaging devices face limitations in achieving high-speed operation and improved temporal resolution due to the restricted charge transfer speed from the photodiode to the floating diffusion, primarily due to mobility constraints within the silicon substrate.
Innovation Solution
The imaging device incorporates a configuration with first and second pixel cells, each featuring a photoelectric converter, charge transfer channels, and charge accumulators, where the distance from the photoelectric converter to the charge accumulator differs between pixel cells, allowing for simultaneous detection in different time windows and improved charge transfer efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If charge is transferred from photodiode to floating diffusion through conventional paths, then charge accumulation is achieved, but transfer speed is limited by silicon substrate mobility
Solution Approach 1:
The pixel cell is divided into multiple independent charge transfer channels (first charge transfer channel and second charge transfer channel) with different path lengths. This segmentation allows charge to be transferred through multiple parallel paths simultaneously, increasing overall transfer speed while maintaining reliable temporal resolution through differentiated timing windows.
Solution Approach 2:
The invention introduces a spatial dimension variation by creating charge transfer channels with different path lengths (first position and second position at different distances from photoelectric converter). This dimensional differentiation enables multi-time-window detection, allowing faster charge transfer while preserving temporal resolution through spatial-temporal mapping.
2Duration of action of moving object
If discharge gate is used to discharge charge from photodiode, then reset time is reduced to practically zero, but charge transfer to floating diffusion remains the limiting factor
Solution Approach 1:
The invention extracts the charge transfer function from the single conventional path to multiple parallel charge transfer channels. By taking out and duplicating transfer paths with different lengths, the system maintains the fast reset capability while eliminating the bottleneck of single-path transfer speed, achieving both fast reset and fast overall cycling.
Solution Approach 2:
Multiple charge transfer channels operate continuously and simultaneously, with charge being transferred through different paths at different speeds. This continuous multi-path operation eliminates idle time in the cycle, maintaining uninterrupted useful action and improving overall cycle speed while preserving reset efficiency.
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 higher-speed detection and improved temporal resolution by allowing charge to be transferred and accumulated in multiple time windows, reducing the dependency on the silicon substrate's mobility limitations.
Implementation Method 1
a first photoelectric converter that generates first charge
Data Source
AI summary
An imaging device includes first and second pixel cells. The first and second pixel cells each include: a photoelectric converter that generates charge; a first charge transfer channel that has a first end electrically connected to the photoelectric converter, and a second end, the charge transfer channel transferring the charge in a direction from the first end toward the second end; a second charge transfer channel that branches from a position of the charge transfer channel, the second charge transfer channel transferring at least a part of the charge; and a charge accumulator that accumulates charge transferred via the second charge transfer channel. Distances from the first end to the position in the direction of the first and second pixel cells are different from each other.