Solid-State Imaging Element Conversion Efficiency Control
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Solution Overview
Problem
In solid-state imaging elements, the conversion efficiency of charge to voltage is locked to a minimum when transferring charge from a low-sensitivity photodiode due to the connection configuration, limiting the dynamic range expansion of image data.
Innovation Solution
A solid-state imaging element with high-sensitivity and low-sensitivity transfer transistors, amplification transistors, and conversion efficiency control transistors that allow for controlled conversion efficiency by switching these transistors to optimize charge transfer and voltage signal output, including a driving circuit to manage the transfer and output of signals from multiple charge storage units.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If both switching transistors are switched on to transfer charge from the low-sensitivity photodiode, then charge transfer is enabled, but the conversion efficiency is locked to a minimum value
Solution Approach 1:
The patent introduces conversion efficiency control transistors that dynamically adjust the connection configuration between charge storage units and floating diffusion regions. By switching these control transistors on or off, the system can change the effective capacitance connected to the floating diffusion, thereby adjusting the conversion efficiency from minimum to maximum values while maintaining the ability to transfer charge from low-sensitivity photodiodes.
2Measurement precision
If conversion efficiency is maximized by switching off both switching transistors, then charge to voltage conversion efficiency is improved, but charge transfer from low-sensitivity photodiode is blocked
Solution Approach 1:
The patent introduces conversion efficiency control transistors as intermediary elements between the switching transistors and the floating diffusion region. These control transistors mediate the connection, allowing the system to achieve both charge transfer and high conversion efficiency by selectively connecting charge storage units to the floating diffusion region based on the sensitivity of the photodiode and the desired conversion efficiency level.
3Adaptability or versatility
If multiple charge storage units are connected to expand dynamic range, then image data dynamic range is improved, but dark current noise increases
Solution Approach 1:
The patent applies different conversion efficiency settings to different charge storage units based on their specific function. High-sensitivity photodiodes use one conversion efficiency setting while low-sensitivity photodiodes use another, allowing each region to be optimized for its specific purpose. This local optimization enables dynamic range expansion while minimizing dark current noise in each specific region.
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
Improves the conversion efficiency of charge to voltage, enabling higher dynamic range and reduced dark current noise, thereby enhancing the quality of image data capture.
Implementation Method 1
a high-sensitivity photodiode (311) having a sensitivity higher than a predetermined sensitivity and a low-sensitivity photodiode (312) having a sensitivity lower than the predetermined sensitivity
Data Source
AI summary
Provided is a high-sensitivity-side transfer transistor that transfers a charge from a high-sensitivity photodiode having a sensitivity higher than a predetermined sensitivity to a first charge storage unit. A low-sensitivity-side transfer transistor that transfers a charge from a low-sensitivity photodiode having a sensitivity lower than the predetermined sensitivity to a second charge storage unit. An amplification transistor that amplifies a voltage of the first charge storage unit. A first conversion efficiency control transistor that controls conversion efficiency of converting the charge to the voltage by opening and closing a pathway between the first and second charge storage units. A second conversion efficiency control transistor that controls the conversion efficiency by opening and closing a pathway between the second charge storage unit and a third charge storage unit.