Charge Sensing Amplifier for X-Ray Image Sensor Noise Stabilization
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Solution Overview
Problem
Conventional X-ray image sensors face challenges in maintaining image quality due to variations in external conditions and reset noise, which affect the accuracy of sensing operations and output voltage stability.
Innovation Solution
A charge sensing amplifier configuration with a first capacitor for storing and amplifying charges, a second capacitor for reducing noise-induced voltage variations, and a delay unit for maintaining the output voltage at a reference level, along with control logic for managing reset signals, is employed to stabilize the output voltage and enhance image sensing accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a conventional charge sensing amplifier is used, then the circuit is simple, but the output voltage varies due to reset noise and external conditions
Solution Approach 1:
The charge sensing amplifier is divided into multiple functional blocks: a first capacitor for charge storage, a second capacitor for noise compensation, a delay unit for timing control, and control logic for coordinate operation. This segmentation allows each component to address specific issues (reset noise, external condition variations) independently, achieving stable output voltage without excessive overall complexity.
Solution Approach 2:
The second capacitor acts as an intermediary element that compensates for voltage variations caused by reset noise and external conditions. It mediates between the charge storage function of the first capacitor and the output, filtering out noise and stabilizing the output voltage through its charge-discharge cycles controlled by the delay unit and control logic.
2Productivity
If reset signals are applied frequently, then the sensing operation is maintained, but output voltage stability deteriorates due to reset noise
Solution Approach 1:
Reset signals are applied periodically rather than continuously, with the delay unit introducing controlled time intervals between reset operations. This periodic action maintains the sensing operation continuity while allowing the second capacitor to compensate for voltage variations between resets, reducing the impact of reset noise on output stability.
Solution Approach 2:
The control logic prepares the second capacitor in advance by charging or discharging it based on predicted voltage variations before the actual reset operation occurs. This preliminary action ensures that when the reset signal is applied, the output voltage is already positioned to minimize the impact of reset noise, maintaining stability during frequent sensing operations.
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 significantly reduces output voltage variations caused by external conditions and reset noise, ensuring high-quality image acquisition and maintaining the output voltage at a stable reference level, even under varying conditions.
Implementation Method 1
a first capacitor for storing charges
Implementation Method 2
a second capacitor for reducing variations in voltage induced by reset noise
Data Source
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AI summary
According to example embodiments, an image sensor includes a charge sensing amplifier (200) configured to amplify charges sensed by a sensing unit (110). The charge sensing amplifier includes an input terminal (IN), an amplification terminal (210), an output terminal, a first capacitor (C1) connected between the input terminal and the amplification terminal, a first switch (SW1) connected between the input terminal and the amplification terminal, a second capacitor (C2) connected between the amplification terminal and the output terminal, and a second switch (SW2) connected between the output terminal and a reference voltage terminal.