Radiation Imaging Gain Correction Using Variable Capacitance
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Solution Overview
Problem
Existing radiation imaging apparatuses face challenges in achieving a high signal-to-noise ratio (SNR) due to large pixel nonlinearity, even after gain correction, requiring a large number of calibration points.
Innovation Solution
A radiation imaging apparatus with a photoelectric conversion unit having first and second capacitances, and a gain correction unit that adjusts the interval of gain correction points by switching between these capacitances, allowing for effective correction of pixel values based on the accumulated charge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multi-point gain correction is applied to improve image SNR, then signal-to-noise ratio is improved, but the number of calibration points increases
Solution Approach 1:
The patent applies dynamics by making the gain correction interval variable rather than fixed. The correction interval is dynamically adjusted based on the accumulated charge amount in the photoelectric conversion unit, using different intervals for different charge ranges. This allows the system to adapt the calibration density to the actual operating conditions, achieving high SNR where needed while reducing unnecessary calibrations elsewhere.
Solution Approach 2:
The patent changes the parameter of correction interval based on the charge accumulation state. By switching between a first correction interval for lower charge amounts and a second correction interval for higher charge amounts, the system optimizes the balance between correction precision and calibration overhead. This parameter adaptation resolves the contradiction by concentrating calibration resources where they are most needed.
2Stability of the object's composition
If gain correction is performed to suppress pixel sensitivity fluctuation, then pixel sensitivity uniformity is improved, but image SNR remains reduced when pixel nonlinearity is large
Solution Approach 1:
The patent applies local quality by using different gain correction intervals for different charge accumulation ranges. Instead of applying a uniform correction approach across all operating conditions, the system uses a first correction interval for lower charge amounts and a second correction interval for higher charge amounts. This localized approach ensures that correction precision is optimized for each specific operating region, addressing both sensitivity uniformity and SNR concerns.
Solution Approach 2:
The patent makes the gain correction process dynamic by adjusting the correction interval based on the accumulated charge amount. This dynamic adaptation allows the system to respond to changing operating conditions, applying more frequent corrections when needed and reducing corrections when the system operates in more linear regions, thereby improving both sensitivity uniformity and signal-to-noise ratio.
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 the capture of high SNR images with fewer calibration points, enhancing image quality and reducing the need for extensive calibration.
Implementation Method 1
a photoelectric conversion unit configured to have a first capacitance and a second capacitance as charge accumulation capacitances
Data Source
AI summary
A radiation imaging apparatus that has a plurality of pixels capable of outputting an image signal in accordance with an irradiation of radiation comprises a photoelectric conversion unit which has a first capacitance and a second capacitance as charge accumulation capacitances and a gain correction unit configured to correct a pixel value in relation to a dose of the irradiated radiation based on an image signal outputted in accordance with a charge accumulated by the photoelectric conversion unit. The gain correction unit changes an interval of gain correction points at which to perform correction in accordance with a switch from a first capacitance to a second capacitance.