Radiation Imaging System Without Selenium Layer
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Solution Overview
Problem
Conventional radiation imaging systems using amorphous selenium suffer from 'ghosting' and reduced image resolution due to charge trapping and limited x-ray absorption at higher energies, limiting their application to low-energy x-ray imaging.
Innovation Solution
A radiation imaging system employing an electrical insulation layer without an x-ray semiconductor, utilizing a top electrode, charge collection electrode, and transistors to capture and store x-ray charges, which reduces charge trapping and maintains high spatial resolution across a wide range of x-ray energies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If amorphous selenium is used as photoconductive material, then charge transport properties are improved, but x-ray absorption capability deteriorates at higher energies
Solution Approach 1:
The patent extracts and removes the photoconductive selenium layer from the imaging system. By eliminating the selenium layer that causes charge trapping and ghosting, the system achieves high spatial resolution and eliminates the need for charge erasing schemes while maintaining operational reliability
Solution Approach 2:
The patent introduces an intermediary scintillation layer that converts x-ray photons to visible light photons, which then activate the photoconductive layer. This intermediary conversion process enables effective x-ray absorption at high energies while maintaining charge transport properties through the photoconductive layer
2Quantity of substance
If selenium layer thickness is increased to improve x-ray absorption, then manufacturing complexity increases
Solution Approach 1:
The patent segments the x-ray detection function into two separate layers: a scintillation layer for x-ray absorption and conversion, and a photoconductive layer for charge generation and transport. This segmentation allows each layer to be optimized independently, reducing overall fabrication complexity while maintaining high x-ray absorption capability
Solution Approach 2:
The patent employs a composite structure combining scintillation material and photoconductive material in a layered configuration. This composite approach leverages the complementary properties of each material to achieve high x-ray absorption without requiring excessive thickness of a single material, thereby simplifying manufacturing
3Measurement precision
If charge collection is improved in selenium layer, then ghosting effect increases due to charge trapping
Solution Approach 1:
The patent removes the selenium photoconductive layer that is responsible for charge trapping and ghosting. By extracting this problematic layer, the system eliminates the source of ghosting while maintaining effective charge collection through the alternative scintillation-photoconductor architecture
Solution Approach 2:
The patent converts the harmful charge trapping phenomenon into a beneficial setup by using a scintillation layer that generates light photons, which then activate a thin photoconductive layer. This conversion approach maintains high charge collection efficiency without the ghosting problem, as the light photon generation and charge separation occur in a controlled manner without significant charge trapping
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 high spatial resolution and minimizes ghosting effects, enabling effective imaging with high-energy x-rays without the need for residual charge-erasing schemes, thus improving image quality and extending application to high-energy x-ray imaging.
Implementation Method 1
electron-hole pairs are generated in the photoconductive layer 190, under the dielectric layer 120, in response to the intensity of the image-wise modulated pattern of x-ray radiation
Implementation Method 2
these electron-hole pairs are separated by the applied biasing electric field supplied by a high voltage power supply. The electron-hole pairs move in opposite directions along the electric field lines toward opposing surfaces of the photoconductive layer 190
Data Source
AI summary
A method of operating a radiation imaging system includes applying a bias voltage to a top electrode, receiving ionization radiation, wherein the ionization radiation penetrates an electrical insulation layer and generate a charge signal, storing the charge signal in a storage capacitor among a plurality of storage capacitors, changing a polarity of a gate line bias voltage of one row of transistors among a plurality of transistors, and integrating charges from storage capacitors connected to each other along orthogonal data lines. The imaging system includes an electrical insulation layer having a top surface and a bottom surface, a top electrode on the top surface of the electrical insulation layer, a plurality of pixel units electrically coupled to the electrical insulation layer, the plurality of pixel units including a plurality of storage capacitors, and a plurality of transistors connected to the plurality of pixel units such that a respective transistor is connected to each of the plurality of pixel units.