Solid-State Imaging Device Impedance Control for Noise Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional solid-state imaging devices face issues with excessive instantaneous current during the global shutter method, leading to potential device damage and image noise due to impedance mismatch between control lines and power supply lines.
Innovation Solution
Incorporating an impedance controller to adjust the impedance value of the power-supply line, allowing for a higher impedance during all reset operations to reduce current flow and a lower impedance during reading operations to minimize noise, without significantly increasing circuit size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an impedance element is inserted between the pixel driver circuit and the power supply terminal to reduce excessive instantaneous current, then device reliability is improved, but the time constant between the control line and power supply increases, extending the convergence time of potential swing and causing noise
Solution Approach 1:
The patent applies dynamics by making the impedance element switchable between two states: a first impedance value during all reset operation to limit instantaneous current, and a second impedance value during reading operation to minimize noise. This dynamic adjustment allows the system to adapt impedance characteristics to different operational phases, resolving the contradiction between current limiting and noise reduction.
Solution Approach 2:
The patent changes the impedance parameter of the impedance element based on operational mode. By controlling the impedance element to present different impedance values in different operations, the system optimizes both current limitation during reset and noise minimization during reading, transforming a static compromised solution into a dynamically optimized one.
2Reliability
If the impedance value of the power-supply line is increased to reduce instantaneous current flow, then device damage is prevented, but noise in the pixel signal output increases
Solution Approach 1:
The patent makes the impedance element dynamic by switching between high impedance during all reset operation (to prevent device damage) and low impedance during reading operation (to minimize noise). This time-varying impedance characteristic allows the system to satisfy both protective and signal-quality requirements that cannot be met simultaneously with a fixed impedance value.
3Device complexity
If a fixed impedance element is used in the power-supply line, then device complexity is reduced, but the system cannot simultaneously optimize for both current limitation and noise reduction
Solution Approach 1:
The patent introduces controlled dynamics through a switchable impedance element that can be controlled by a control signal. This adds minimal complexity while enabling the system to adapt to different operational phases, achieving a balance between circuit simplicity and operational versatility.
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 effectively reduces the risk of device damage and noise in the pixel signal output, ensuring high-quality image capture by managing instantaneous current and potential swings.
Implementation Method 1
an impedance controller configured to control an impedance value for the power-supply line in the reading operation to be less than an impedance value for the power-supply line in the all reset operation
Implementation Method 2
each pixel including a photoelectric conversion element configured to convert incident light into a signal charge
Data Source
AI summary
A solid-state imaging device includes a pixel array, control lines TG each provided for a corresponding one of rows of pixels and configured to control, e.g., operation of a transfer transistor, and a driver circuit 103 configured to control the operation of the transfer transistor through the control lines TG and connected to a power-supply line TGL. The solid-state imaging device performs all reset operation for resetting signal charges of all pixels by the driver circuit 103 and reading operation for reading a pixel signal from each row of the pixels. An impedance controller 130 configured to control an impedance value for power-supply line TGL in the reading operation to be less than an impedance value for power-supply line TGL in the all reset operation is provided.