Radiation Imaging Bias Current Evaluation for Dark Charge Variation
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Solution Overview
Problem
Existing radiation imaging apparatuses face challenges in accurately determining radiation irradiation due to variations in dark charge currents, leading to determination errors, especially when using pre-measured current profiles from factory tests that do not account for actual usage conditions.
Innovation Solution
The radiation imaging apparatus employs a detection unit with conversion elements and transistors, using a bias current evaluation system that adjusts for dark current estimates and uses dynamic comparison target values based on previous determination processes to improve accuracy, allowing for real-time detection of radiation irradiation and termination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If pre-measured current profiles from factory tests are used for radiation determination, then the device complexity is reduced, but the measurement precision deteriorates due to variations in dark charge currents under different usage conditions
Solution Approach 1:
The patent applies preliminary action by measuring and storing current profiles during a calibration phase before actual radiation detection. The system pre-measures current characteristics under various conditions (with and without radiation, with different reset operations) and stores these profiles for later comparison during operation, enabling accurate radiation determination without complex real-time analysis
Solution Approach 2:
The system uses feedback by continuously monitoring the current flowing through the bias line and comparing it against stored reference profiles. The determination unit adjusts its assessment based on the difference between measured current and expected current profiles, refining radiation detection accuracy through iterative comparison and adaptation
2Manufacturing precision
If sequential reset operation is performed on conversion elements, then the manufacturing precision is maintained, but measurement precision deteriorates due to reset-induced currents flowing in the bias line
Solution Approach 1:
The patent segments the reset operation by performing it row-by-row or in groups rather than simultaneously across all conversion elements. This segmentation isolates reset-induced currents to specific time windows and spatial regions, allowing the system to distinguish them from radiation-induced currents and maintain measurement precision
Solution Approach 2:
The system introduces an intermediary approach by using the bias line current as a mediator signal that contains information about both radiation and reset operations. By analyzing the temporal and spatial characteristics of this intermediate signal, the determination unit can separate and identify radiation-induced currents from reset-induced currents
3Ease of operation
If factory shipment current values are used for correction, then the ease of operation is improved, but reliability deteriorates due to variations in dark charge between test and actual usage conditions
Solution Approach 1:
The patent applies parameter changes by measuring and storing current profiles under multiple different conditions (with radiation, without radiation, with reset operations, without reset operations) rather than relying on a single factory measurement. This multi-parameter approach captures the variability of dark charge under different usage conditions, improving reliability while maintaining ease of operation through pre-characterization
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 enhances the accuracy of radiation detection by reducing the impact of dark current variations, enabling precise determination of radiation irradiation and termination, thereby improving the reliability of image data generation.
Implementation Method 1
Each pixel includes a conversion element which converts X-rays or light into charge
Data Source
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AI summary
A radiation imaging apparatus (130) including pixels; driving lines; a driving circuit (202); bias lines (BS1 - Bs3, BsC); an acquisition unit (205) configured to acquire an evaluation value based on a current flowing in the bias line; a determination unit (208) configured to compare the evaluation value with a comparison target value to determine whether radiation is irradiated; a control unit (209) configured to control the acquisition unit and the determination unit; and a storage unit (207) configured to store the evaluation value used in the determination process, is provided. A comparison target value used in a given determination process is based on one or more evaluation values used in one or more determination processes which are performed before the given determination process and in which it is determined that radiation has not been irradiated.