Radiation Imaging Detector Proportional Charge Gain Readout
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Solution Overview
Problem
Existing X-ray imaging systems suffer from charge injection noise and Thin Film Transistor (TFT) arrays switching noise, which degrade image quality and increase noise levels, especially under high electric fields and thick conversion material usage.
Innovation Solution
A radiation imaging detector system that uses a photoconductive material with buried electrodes and dielectric layers to direct electric fields away from conductive surfaces during image capture, allowing for low noise readout without TFTs, employing correlated double sampling to minimize thermal and reset noise, and using high-temperature materials without damaging the readout array.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If charge integration time is extended to improve signal accumulation, then signal-to-noise ratio improves, but temporal resolution deteriorates due to fixed readout timing
Solution Approach 1:
The patent applies dynamics by making the integration time variable rather than fixed. The readout circuit dynamically adjusts the integration period for each pixel based on detected motion or scene requirements, allowing longer integration for static scenes (improving SNR) and shorter integration for moving scenes (maintaining temporal resolution). This resolves the contradiction by adapting the integration time to actual needs rather than using a fixed value.
2Adaptability or versatility
If per-pixel readout circuitry is added to enable independent charge transfer for variable integration, then temporal resolution and flexibility improve, but device complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the detector into multiple independently controllable pixel regions, each with its own readout circuitry. This allows different integration times to be applied to different regions simultaneously based on their individual requirements. The segmentation enables flexible adaptation to various imaging scenarios while maintaining manageable circuit complexity through modular design.
3Ease of manufacture
If charge transfer is initiated at fixed intervals, then readout timing is simplified, but charge loss occurs due to carrier recombination during extended integration periods
Solution Approach 1:
The patent applies feedback by using the detected signal level to control the timing of charge transfer. The readout circuit monitors the accumulated charge and initiates transfer when optimal levels are reached, or adjusts timing based on scene characteristics. This feedback mechanism ensures charges are transferred before recombination losses occur while maintaining relatively simple readout timing through automated control.
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 system achieves ultra-low noise image capture by avoiding charge injection and TFT switching noise, enabling high-quality imaging with thicker conversion materials and reduced fabrication costs, while allowing for large-scale array construction without the limitations of conventional TFT fabrication tools.
Implementation Method 1
a radiation imaging detector comprising a two-dimensional array of photodetectors... each photodetector comprising a semiconductor body... configured to transfer a first charge to a first floating diffusion and a second charge to a second floating diffusion
Implementation Method 2
an amplifier circuit coupled to the first and second floating diffusion... wherein the amplifier circuit is configured to provide a proportional charge gain to the first charge and the second charge during readout of the first charge and the second charge
Data Source
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AI summary
The invention relates to a two steps image capture panel for recording x-ray image information. More particularly, the invention relates to a method and an apparatus for directing the internal electric field to capture the x-ray image first on an insulating surface, avoiding charge injection noise from the insulating surface, and then re-directing the internal electrical field to transfer the image charge from the insulating surface to a conductive readout electrode with electric field sufficient for charge gain during image readout.