Radiation Image Detection Analog Leak Correction
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Solution Overview
Problem
Conventional radiation image detection systems face issues with dynamic range reduction due to leak currents from TFT switches, especially when high doses of X-rays are irradiated, leading to errors in image signals.
Innovation Solution
The method involves detecting an analog leak level through each data line with TFT switches in the OFF state before switching them ON, and correcting the analog image signal based on this leak level before conversion to digital, thereby preventing dynamic range reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If leak current correction is performed by subtracting leak current component from digital image signal after A/D conversion, then image signal error is corrected, but dynamic range of the image signal is reduced
Solution Approach 1:
The patent performs leak current correction before A/D conversion by detecting leak current with TFT switches in OFF state and subtracting it from the image signal in analog domain. This preliminary correction prevents dynamic range reduction while maintaining signal accuracy, as the correction occurs before the signal is quantized to digital values.
Solution Approach 2:
The patent introduces an intermediate leak current detection step between charge accumulation and signal readout. By detecting leak current through data lines when TFT switches are OFF, and using this as a reference to correct the subsequent image signal, the system accurately removes leak current effects without compromising the full dynamic range of the original signal.
2Illumination intensity
If larger amount of X-rays is irradiated to generate more charges, then image signal intensity is improved, but leak current increases causing more noise
Solution Approach 1:
The patent implements a feedback mechanism where leak current is detected during the readout process (when TFT switches are OFF) and this detected leak current value is used to correct the image signal. This feedback approach dynamically compensates for leak current noise that increases with higher X-ray doses, maintaining signal quality across varying illumination intensities.
Solution Approach 2:
The patent converts the harmful leak current into a useful correction reference. By deliberately measuring the leak current that flows through data lines when TFT switches are OFF, the system obtains a direct measurement of the noise component, which is then subtracted from the image signal to eliminate the harmful effect and recover the true image information.
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
This approach effectively corrects image signal errors caused by leak currents while maintaining the full dynamic range of the image signal, even under high X-ray irradiation conditions.
Implementation Method 1
Radiation, such as X-rays or the like, enters from a direction normal to the surface of FIG. 8, which is converted to electrical signals by the photoelectric conversion elements
Data Source
AI summary
A radiation image detection method including the steps of: detecting from a radiation image detector including multitudes of pixels disposed two-dimensionally, each having a TFT switch, an analog image signal of each pixel flowing out through each data line by sequentially switching ON the TFT switches connected to each scanning line on a scanning line-by-scanning line basis; detecting an analog leak level flowing out through each data line with the TFT switches connected to each of the scanning lines being switched OFF each time before switching ON the TFT switches on a scanning line-by-scanning line basis when converting the detected analog image signal to a digital image signal and outputting; and correcting the analog image signal before being converted to the digital image signal based on the leak level.