Noise-Reducing Image Sensor Design for X-Ray Systems
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Summary
Problems
Existing image sensors, particularly those using thin-film transistor (TFT) panels, face challenges with noise and voltage threshold variations, which limit their dynamic range and increase power dissipation, especially in active pixel arrays for X-ray imaging.
Innovation solutions
The implementation of capacitive coupling between the input node and the column line allows for voltage shifting within the operational range of the readout circuitry, enabling the use of TFT technology while isolating high voltages from semiconductor dies, thereby reducing noise and threshold voltage variations.
TRIZ Analysis
Specific contradictions:
General conflict description:
Principle concept:
If active pixel arrays are implemented on TFT panels, then the dynamic range is improved, but noise and threshold voltage variations increase
Why choose this principle:
A capacitive coupling element is introduced between the pixel array output and the readout circuitry input. This capacitor acts as an intermediary that blocks DC voltage variations and threshold voltage drift from the TFT panel while allowing AC signal transmission, thereby reducing noise and stabilizing the readout circuit operation without compromising dynamic range
Principle concept:
If active pixel arrays are implemented on TFT panels, then the dynamic range is improved, but noise and threshold voltage variations increase
Why choose this principle:
The system is divided into two distinct parts: the pixel array on the TFT panel and the readout circuitry on a separate semiconductor die. This segmentation isolates the noise-sensitive readout circuit from the noisy TFT panel, allowing each to be optimized independently while maintaining their functional connection through the capacitive coupling
Application Domain
Data Source
AI summary:
The implementation of capacitive coupling between the input node and the column line allows for voltage shifting within the operational range of the readout circuitry, enabling the use of TFT technology while isolating high voltages from semiconductor dies, thereby reducing noise and threshold voltage variations.
Abstract
The present invention relates to an image sensor and to an imaging system comprising the same. The present invention particularly relates to X-ray image sensors and imaging systems. The image sensor according to the invention comprises a pixel array that includes a plurality of active pixels arranged in a matrix of rows and columns, and a plurality of column lines to which outputs of pixels in the same column are coupled for the purpose of outputting pixel signals. The image sensor further comprises readout circuitry that includes a plurality of readout units, each readout unit being configured for reading out a respective column line through an input node of the readout unit. The image sensor is characterized in that the image sensor further comprises capacitive units, such as capacitors, for capacitively coupling each input node to its corresponding column line.