Image Sensor Transfer Transistor Voltage Control
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Solution Overview
Problem
Image sensors often experience horizontal band noise (SHBN) due to bright light exposure, which degrades image quality and is not effectively addressed by existing technologies.
Innovation Solution
An image sensor design incorporating a photoelectric converter, transfer transistor, source follower transistor, and correlated double sampler (CDS) with specific voltage control signals to manage charge transfer and output conversion, minimizing noise by maintaining the voltage of the transmission signal at a stable level during charge transfer and output processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a transfer transistor is used to transfer charges from the photoelectric converter to the floating diffusion node, then charge transfer efficiency is improved, but parasitic capacitive coupling occurs between the transfer line and output line causing horizontal band noise
Solution Approach 1:
The patent extracts and removes the problematic parasitic capacitive coupling effect by carefully controlling the voltage levels during different operational phases. The transfer line voltage is set to a second voltage level during the transfer period that minimizes parasitic coupling to the output line, effectively taking out the harmful noise component while preserving the charge transfer function.
Solution Approach 2:
The patent applies preliminary action by pre-setting the voltage levels of the transfer line and control signals before the charge transfer operation begins. The transfer line is prepared with the appropriate voltage level to enable efficient charge transfer while minimizing parasitic effects, and the control signals are timed to ensure proper sequencing of operations.
2Measurement precision
If voltage levels are changed during operation to control charge transfer, then transfer precision is improved, but signal timing complexity increases
Solution Approach 1:
The patent employs periodic action by using cyclically repeating control signals with different voltage levels applied to the transfer line and control terminals. The control signals follow a periodic pattern that switches between different voltage levels at specific intervals, enabling precise charge transfer while maintaining manageable timing through regular, repeating cycles rather than complex irregular sequences.
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
The solution effectively reduces noise in image sensors, enhancing image quality by stabilizing voltage levels and minimizing parasitic capacitive coupling effects that cause horizontal band noise.
Implementation Method 1
a photoelectric converter to receive light, to generate charges in response to the received light
Data Source
AI summary
An image sensor includes a photoelectric converter to generate charges in response to incident light and to provide the generated charges to a first node, a transfer transistor to provide a voltage of the first node to a floating diffusion node based on a first control signal, a source follower transistor to provide a voltage of the floating diffusion node as a unit pixel output, a correlated double sampler (CDS) to receive the unit pixel output and to convert the unit pixel output into a digital code. The first control signal having first, second, and third voltages is maintained at the second voltage in a period between when the voltage of the first node is provided to the floating diffusion node and when the CDS is provided with the voltage of the first node as the unit pixel output.