Radiation Image Detector Automatic Exposure Detection Circuit
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Solution Overview
Problem
Radiation image detectors face challenges in achieving accurate image sensing due to dark current issues and inappropriate exposure times, which affect image quality.
Innovation Solution
A radiation image detector with automatic exposure detection capability, incorporating a high voltage circuit, image sensing panel with photoconductive and barrier layers, and an automatic exposure detector to determine optimal exposure onset and cessation times based on sensing signal patterns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If photoconductive material is used to generate charges, then image sensing capability is achieved, but dark current increases resulting in background level issues
Solution Approach 1:
The patent extracts and removes electrons from the photoconductive layer through an electron barrier layer, separating the harmful electrons (dark current) from the useful holes (image signal). This allows the photoconductive material to maintain its charge generation capability while eliminating the dark current interference.
Solution Approach 2:
The patent introduces an electron barrier layer as an intermediary between the photoconductive layer and the electrode. This intermediary structure selectively blocks electrons while allowing holes to pass, thereby resolving the conflict between charge generation and dark current suppression.
2Measurement precision
If exposure time is extended to improve image quality, then more charge carriers are collected, but background noise increases
Solution Approach 1:
The patent extracts electrons before they can contribute to background noise accumulation during extended exposure. By removing electrons through the electron barrier layer, the system can maintain longer exposure times for improved image quality without the penalty of increased background noise from electron accumulation.
3Object-generated harmful factors
If exposure time is shortened to reduce background noise, then dark current impact is reduced, but image quality deteriorates
Solution Approach 1:
The electron barrier layer acts as an intermediary that enables the system to maintain optimal exposure timing. By blocking electrons at the barrier interface, the system can precisely control exposure duration without the trade-off between background noise and image quality that plagues conventional systems.
4Measurement precision
If automatic exposure detection is added to optimize exposure timing, then image quality is improved, but device complexity increases
Solution Approach 1:
The patent merges the automatic exposure detection function with the existing readout circuitry. The electron barrier layer's inherent electron-blocking property provides a natural signal for exposure detection, eliminating the need for separate complex detection systems while achieving precise exposure timing 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
Improves image sensing quality by accurately determining exposure times, reducing background noise, and enhancing the collection of charge carriers, thereby improving the overall image quality.
Implementation Method 1
The photoconductive layer senses the incident X-ray and generates the holes and the electrons
Implementation Method 2
the hole barrier layer blocks the holes injected from the upper electrode layer
Implementation Method 3
the electron barrier layer blocks the electrons injected from the lower electrode layer
Data Source
AI summary
A radiation image detector with automatic exposure detection includes a high voltage circuit unit for providing an operation bias. An image sensing panel includes semiconductor multi-layer structure, receives the operation bias and senses an incident X-ray, and produces holes and electrons. The holes produce positive charges for forming an image. An automatic exposure detector is coupled to the high voltage circuit unit to transfer the operation bias and detects variation pattern with time of a voltage signal or a current signal induced by the electrons to determine an onset time or a cessation time for exposure. A control unit couples to the high voltage circuit unit, the image sensing panel, and the automatic exposure detector and configured to perform system control, including obtaining an image signal from the image sensing panel. An imaging unit couples to the control unit to process the image signal and display and store the image.