Inclined-Substrate Photon-Counting Detector for Higher X-Ray Resolution
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Solution Overview
Problem
Existing radiographic inspection devices, such as CT devices, face limitations in reducing X-ray exposure amount and improving spatial resolution due to the inefficiencies in converting X-rays into electrical signals and the size constraints of solid scintillators, leading to low light sensitivity and limited resolution.
Innovation Solution
A photon counting radiation detector with an epitaxial layer on a substrate, where the substrate is inclined at a specific angle to minimize overlapping and contamination, allowing for smaller detection pixels and higher resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a solid scintillator is used to convert X-rays into visible light, then the radiation detection function is achieved, but the light sensitivity is limited and the X-ray exposure amount cannot be reduced sufficiently
Solution Approach 1:
The patent introduces a photodiode as an intermediary device that directly converts X-rays into electrical signals, eliminating the need for solid scintillators and the associated light conversion losses. This direct conversion approach resolves the contradiction by improving light sensitivity while maintaining detection efficiency.
Solution Approach 2:
The patent replaces the mechanical/optical system (solid scintillator converting X-rays to light, then photodiode converting light to electrical signals) with a direct electrical conversion system where the photodiode converts X-rays directly into electrical signals, eliminating the intermediate light conversion step and its associated losses.
2Measurement precision
If the solid scintillator size is reduced to improve spatial resolution, then the resolution is limited by the polycrystalline structure of the scintillator
Solution Approach 1:
The patent replaces the solid scintillator with a photodiode that has no polycrystalline structure limitations. This substitution allows for continuous reduction in detector size without encountering the fundamental material structure limits that constrain scintillator-based systems, thereby enabling improved spatial resolution.
3Measurement precision
If the detection pixel size is reduced to achieve higher resolution, then regions incapable of detection increase and image blur occurs
Solution Approach 1:
The patent changes the electrical parameters of the photodiode, specifically optimizing the reverse bias voltage to extend the depletion layer width. This parameter change allows for smaller detection pixels without creating dead regions, as the extended depletion layer ensures complete charge collection even in reduced pixel geometries, thereby preventing image blur while maintaining high resolution.
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 detector achieves higher resolution by reducing regions incapable of detection and suppressing image blur, enabling more detailed imaging with reduced X-ray exposure.
Implementation Method 1
The visible light is converted into an electrical signal via a photodiode detector
Implementation Method 2
a luminescent material called a solid scintillator is used in X-ray CT devices. The solid scintillator is a substance that emits light when irradiated with X-rays
Implementation Method 3
a radiation detector in which the radiation passing through a test subject is converted directly into an electrical signal
Data Source
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AI summary
A photon counting radiation detector (100) includes a cell structure (1) including a substrate (3) and an epitaxial layer (2) provided on the substrate (3), radiation being incident on the epitaxial layer (2); an inclination θ of the substrate (3) being set in a predetermined range, where tsub is a thickness of the substrate (3), tepi is a thickness of the epitaxial layer (2), L is a length of the substrate (3), and the inclination θ is an inclination of the substrate (3) with respect to an incident direction of the X-rays. The epitaxial layer (2) is preferably one type selected from SiC, Ga2O3, GaAs, GaN, diamond, and CdTe. Such a photon counting radiation detector (100) is preferably a direct converting type.