Radiation Image Pickup Threshold Calibration
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Solution Overview
Problem
Existing radiation image pickup apparatuses face challenges in accurately detecting the presence and absence of irradiation due to noise components coupled with signal outputs, particularly during reset operations, and lack optimal threshold value settings for precise detection.
Innovation Solution
The method involves switching the radiation image pickup apparatus between two modes to calculate and set optimal threshold values based on detection signals during irradiation and non-irradiation periods, using a pixel array with conversion and switch elements, and an arithmetic unit to process detection signals and determine the start and end of irradiation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If differential processing is performed on detection signals to remove noise components, then measurement precision is improved, but device complexity increases due to additional signal processing requirements
Solution Approach 1:
The patent applies preliminary action by pre-calculating threshold values based on statistical parameters (mean and standard deviation) of detection signals acquired during calibration periods before actual irradiation detection. This preprocessing approach separates the complex signal processing from the real-time detection, improving measurement precision while managing device complexity through offline computation.
2Reliability
If threshold values are set to ensure high detection accuracy, then reliability is improved, but detection time increases due to careful threshold selection and verification
Solution Approach 1:
The patent performs preliminary action by acquiring detection signals during calibration periods (before actual use) to calculate statistical parameters and determine optimal threshold values. This advance preparation ensures high detection reliability during operation without time loss, as the threshold selection process is completed beforehand rather than during real-time detection.
Solution Approach 2:
The patent applies parameter changes by using statistical parameters (mean and standard deviation) of detection signals to dynamically determine optimal threshold values. Instead of using fixed arbitrary thresholds, the system adjusts thresholds based on the actual signal characteristics, improving reliability while maintaining efficient detection timing.
3Measurement precision
If optimal threshold values are determined through advance calibration and statistical analysis, then measurement precision is improved, but loss of time occurs during the calibration process
Solution Approach 1:
The patent accepts the time loss during calibration as a necessary preliminary action that occurs only once or periodically, not during each detection event. By performing the time-consuming signal acquisition and statistical analysis in advance, the system achieves high measurement precision during actual operation without recurring time penalties.
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 enables instantaneous and highly accurate detection of irradiation presence/absence by minimizing noise interference and optimizing threshold settings, improving detection accuracy and reducing the time required to detect the start of irradiation.
Implementation Method 1
Each of the pixels includes a conversion element that converts radiation or light into electric carriers
Data Source
AI summary
A radiation image pickup apparatus includes a pixel array having pixels each including a conversion element and a switch element, a drive circuit for controlling the switch element between a conducting state and a non-conducting state, a detection unit for outputting a detection signal varying with the intensity of irradiation of the pixel array, and an arithmetic unit for calculating a start threshold value used to detect start of irradiation based on the signal output from the detection unit during a period when radiation is not emitted onto the pixel array in which the switch elements are sequentially set in a conducting state on a row-by-row basis by the drive circuit and the signal output from the detection unit during a period when radiation is emitted onto the pixel array in which the switch elements are sequentially set in a conducting state on a row-by-row basis by the drive circuit.