CMOS Image Sensor Floating Diffusion Segmentation
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Solution Overview
Problem
CMOS image sensors face limitations in dynamic range, leading to saturation in bright areas and inability to express dark images due to limited capacitance of the floating diffusion region, which compromises sensitivity when attempting to expand dynamic range.
Innovation Solution
Implementing multiple floating diffusion regions with varying capacitance within a pixel, allowing for expanded dynamic range without sacrificing sensitivity by separating them for optimal charge handling at different illuminance levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the capacitance of the floating diffusion region is increased to expand dynamic range, then the dynamic range is improved, but the sensitivity is decreased and dark images cannot be expressed
Solution Approach 1:
The pixel is divided into multiple floating diffusion regions (first floating diffusion region and second floating diffusion region) with different capacitance values. The first floating diffusion region has larger capacitance for handling bright images, while the second has smaller capacitance for capturing dark images, allowing simultaneous optimization for both dynamic range and sensitivity
Solution Approach 2:
Different regions within the pixel are assigned different capacitance characteristics tailored to specific imaging conditions. The first floating diffusion region is optimized for high illuminance conditions with larger capacitance, while the second is optimized for low illuminance conditions with smaller capacitance, enabling each region to perform its specialized function effectively
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
Enables vivid image capture across a wide illuminance range without saturation, maintaining high sensitivity by synthesizing signals from regions optimized for low and high capacitance, thus enhancing the dynamic range of CMOS image sensors.
Implementation Method 1
If light is irradiated onto the surface of the photodiode (PD) 110, holes and electrons are separated. Then, the holes flow to a ground to be then removed, and electrons accumulate in the photodiode (PD) 110.
Data Source
AI summary
A CMOS (Complementary Metal-Oxide Semiconductor) image sensor is provided. A CMOS image sensor includes a first light-receiving unit converting light into charge, a first floating diffusion region, in which a first potential corresponding to the converted amount of charge is generated and a second floating diffusion region, to which the charge in the first floating diffusion region is transmitted, and in which a second potential is generated, wherein a wide dynamic range signal is acquired from the first floating diffusion region, a high-sensitively signal is acquired from the second floating diffusion region, and the acquired signals are synthesized and output.