Solid-State Image Sensor Charge-Voltage Converter Dynamic Range
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Solution Overview
Problem
The existing solid-state image sensors have a limited dynamic range due to the restricted potential increase of the floating diffusion (FD) when the reset transistor is not turned on, which limits the charge quantity that can be transferred to the charge-voltage converter.
Innovation Solution
The proposed solid-state image sensor includes a transfer transistor, an amplifier transistor, and a capacitance between a control signal line and the charge-voltage converter, where the potential of the charge-voltage converter changes direction using the control signal line, allowing for increased charge transfer and dynamic range expansion by capacitive coupling, even when the reset transistor is turned off.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the potential of the floating diffusion is increased by increasing the potential of the gate of a reset transistor, then the charge quantity that can be transferred to the floating diffusion increases and the dynamic range widens, but the reset transistor turns on and drives the floating diffusion at a predetermined potential, making it impossible to read out signals corresponding to the charges of the photoelectric converters
Solution Approach 1:
The patent divides the potential control function into two independent parts: the reset transistor controls the minimum potential of the floating diffusion, while a separate capacitance connected to a control signal line controls the maximum potential. This segmentation allows each component to operate independently without interfering with the other's function, resolving the contradiction between increasing charge quantity and maintaining signal readout capability.
Solution Approach 2:
The patent introduces a capacitance as an intermediary element between the control signal line and the floating diffusion. This capacitance acts as a mediator that can increase the potential of the floating diffusion without requiring the reset transistor to turn on, thereby preventing the reset transistor from driving the floating diffusion to a fixed potential while still achieving the desired potential increase for higher charge capacity.
2Ease of operation
If the potential of the gate of the reset transistor is increased until the reset transistor is turned on, then the floating diffusion is driven at a predetermined potential, but it becomes impossible to read out signals corresponding to the charges of the photoelectric converters even if the charges are transferred to the floating diffusion
Solution Approach 1:
The patent segments the potential control function into two independent control mechanisms: the reset transistor for minimum potential control and a separate capacitance connected to a control signal line for maximum potential control. This allows the floating diffusion to achieve a wider potential control range while maintaining signal readout capability, as each control mechanism operates independently without interfering with the other.
Solution Approach 2:
The capacitance serves as an intermediary that enables extended potential control range without requiring the reset transistor to turn on. By using this intermediate element, the system can achieve greater potential control flexibility while preserving the ability to read out signal information from the photoelectric converters.
3Adaptability or versatility
If the charge quantity that can be transferred to the floating diffusion is limited to the range where the reset transistor is not turned on, then the dynamic range is limited, but increasing the potential beyond this range causes the reset transistor to turn on and prevent signal readout
Solution Approach 1:
The patent segments the potential control function into two independent parts: the reset transistor handles minimum potential control while a separate capacitance connected to a control signal line handles maximum potential control. This segmentation enables the floating diffusion to achieve a wider dynamic range without requiring complex interconnections or control logic, as each segment operates independently.
Solution Approach 2:
The capacitance serves multiple functions: it increases the potential of the floating diffusion to expand the dynamic range, it prevents the reset transistor from turning on during normal operation, and it enables independent control of the maximum potential. This multi-functionality achieves enhanced adaptability without proportionally increasing device complexity.
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 a higher saturated charge quantity to be transferred to the charge-voltage converter, effectively widening the dynamic range and enhancing image sensor performance.
Implementation Method 1
a capacitance between a control signal line and the charge-voltage converter; and a control unit configured to change a potential of the control signal line so that the potential of the charge-voltage converter changes to a second direction which is opposite to the first direction
Data Source
AI summary
An image sensor including a photoelectric converter, a charge-voltage converter, a transfer transistor to transfer a charge from the photoelectric converter to the charge-voltage converter whereby potential of the charge-voltage converter changes to a first direction, an amplifier transistor to output a signal corresponding to potential of the charge-voltage converter to a column signal line, the amplifier transistor sequentially outputting, to the column signal line, noise level and light signal level, a capacitance between a control signal line and the charge-voltage converter, and a control unit to change a potential of the control signal line so that the potential of the charge-voltage converter changes to a second direction opposite to the first direction in a period in which the charge-voltage converter is in floating and which is prior to outputting the noise level.