CMOS Image Sensor Pixel-Embedded Amplifier for Dynamic Range
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Solution Overview
Problem
Conventional CMOS image sensors suffer from low dynamic range and high noise in low-light conditions, requiring additional hardware and consuming more power, which makes them inefficient and costly for applications like night-vision and surveillance.
Innovation Solution
A high dynamic range CMOS image sensor with pixel-embedded signal amplification using a single in-pixel switch for dual-mode operation, combining capacitance and switched biasing to enhance signal-to-noise ratio and reduce noise, thereby achieving efficient and compact imaging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If conventional CMOS sensors amplify the input signal using static amplifiers and capacitors, then the output signal voltage increases, but the image quality deteriorates due to noise and compromised gain
Solution Approach 1:
The patent applies dynamics by making the amplifier biasing state time-varying rather than static. The amplifier transitions between different biasing states (first biasing state with higher gain, second biasing state with lower noise) at different time periods. This dynamic approach allows the system to optimize both gain and noise performance over time, resolving the contradiction between achieving high signal voltage and maintaining image quality.
Solution Approach 2:
The patent implements periodic action by alternating the amplifier's biasing state between two distinct states at different time periods. During the first time period, the amplifier operates in a high-gain state for signal accumulation; during the second time period, it switches to a low-noise state for signal reading. This periodic switching enables the system to achieve both high signal voltage and high image quality by optimizing different phases of the signal processing cycle.
2Reliability
If additional hardware is added to improve low-light performance, then the imaging capability enhances, but the device complexity and cost increase
Solution Approach 1:
The patent applies universality by making the existing amplifier perform multiple functions through dynamic biasing. The same amplifier circuit serves both as a high-gain signal accumulation amplifier and as a low-noise signal reading amplifier, depending on its biasing state. This eliminates the need for separate dedicated amplifiers for different functions, reducing device complexity while maintaining enhanced low-light imaging capability.
Solution Approach 2:
The patent applies parameter changes by dynamically adjusting the amplifier's biasing parameters (voltage, current) rather than changing the hardware structure. By changing the electrical parameters of the existing amplifier circuit, the system achieves different operational modes (high-gain mode, low-noise mode) without adding any physical components, thereby improving low-light performance while keeping device complexity low.
3Adaptability or versatility
If conventional sensors use dynamic range optimization, then the bright-light performance improves, but the low-light signal-to-noise ratio deteriorates
Solution Approach 1:
The patent applies dynamics by transitioning the amplifier between different biasing states at different time periods. During the signal accumulation phase, the amplifier operates in a first biasing state optimized for gain; during the signal reading phase, it switches to a second biasing state optimized for low noise. This dynamic adaptation allows the system to maintain high signal-to-noise ratio in low-light conditions while preserving broad dynamic range capability.
Solution Approach 2:
The patent applies preliminary action by accumulating the signal at high gain during the first time period before switching to the low-noise reading state. This preliminary signal accumulation at enhanced gain ensures that even weak low-light signals are amplified sufficiently before the noise-optimized reading phase begins, thereby maintaining high signal-to-noise ratio while preserving dynamic range.
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 enhances the signal-to-noise ratio and dynamic range in low-light conditions, reducing power consumption and hardware requirements, resulting in a more efficient, compact, and cost-effective imaging solution.
Implementation Method 1
receiving light for a predetermined duration on a pixel array, including a plurality of photodiodes
Implementation Method 2
modulating the in-pixel amplifier in the capacitance mode for a voltage-build, wherein the voltage build-up augments gain of the input electronic signal
Data Source
AI summary
A method and a system are described for improving a dynamic range of a CMOS image sensor by pixel-embedded signal amplification. An electromagnetic radiation is incident for a predetermined duration on a pixel array including a plurality of photodiodes. The photodiodes release electrons in form of an input electronic signal and the released input signal is temporarily stored in a storage node. The said input signal is then transferred to a gate of an in-pixel amplifier, which is configured to dynamically alternate between modes of capacitance and switched biasing, using a single in-pixel switch. Then, the in-pixel amplifier is modulated while in capacitance mode for a voltage build-up and this augment gain of the input signal. Thereafter, the in-pixel amplifier alternates to a switched biasing mode for suppression of noise signals. Finally, a resultant electronic signal is generated with a high gain after processing and suppression of the noise signals.