Non-Linearity in Wide Dynamic Range CMOS Image Sensors Utilizing a Partial Charge Transfer Technique.

Area of Science:

• * Electrical Engineering
• * Solid-State Devices
• * Image Sensor Technology

Background:

• * Partial charge transfer (PCT) technique enhances CMOS image sensor dynamic range by combining long and short accumulation time signals.
• * The short accumulation time signal in PCT exhibits non-linearity with incident light, impacting accuracy.
• * Understanding and mitigating this non-linearity is essential for high-performance image sensors.

Purpose of the Study:

• * To analyze the non-linearity present in the short accumulation time signal of the PCT technique.
• * To investigate the relationship between dynamic range expansion and signal non-linearity.
• * To identify the primary factors contributing to non-linearity in PCT.

Main Methods:

• * Theoretical analysis of charge transfer dynamics in CMOS image sensors.
• * Modeling of current diffusion and photodiode initial conditions.
• * Simulation and analysis of signal behavior under varying illumination.

Main Results:

• * Non-linearity in PCT is attributed to current diffusion (exponentially related to potential barrier) and photodiode initial conditions.
• * Error in high illumination regions increases with the ratio of long to short accumulation times.
• * Higher photodiode saturation levels exacerbate errors in high illumination conditions.

Conclusions:

• * The PCT technique's non-linearity is a critical factor limiting its effectiveness, particularly in high illumination scenarios.
• * Mitigation strategies should address current diffusion and optimize photodiode characteristics.
• * Further research is needed to fully compensate for non-linearity and maximize dynamic range benefits.