Radiography Apparatus Signal Sampling for Parasitic Capacitance Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Radiography apparatuses using pixels with switching elements face challenges in reducing the time required to capture radiographic images due to the need to wait for charge movement from parasitic capacitance, which is not adequately addressed by existing techniques like those using CCD sensors.
Innovation Solution
A radiography apparatus with a radiation detector featuring pixels with conversion elements and switching elements, employing first and second sample-and-hold units and a control unit to manage the switching elements' states, allowing for the acquisition and correction of electric signals to reduce image capture time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the switching element is turned off and the radiography apparatus waits for charge to move from parasitic capacitance before sampling and holding the electric signal, then the switching element can properly read out charge from the pixel, but the time required to capture a radiographic image increases
Solution Approach 1:
The patent applies preliminary action by performing sample-and-hold operations at specific timing points (before and after the control signal) in advance, so that the charge movement from parasitic capacitance is already accounted for when the final image signal is processed. This eliminates the need to wait for charge to fully move from parasitic capacitance, thereby reducing image capture time while maintaining readout accuracy
Solution Approach 2:
The patent uses feedback by comparing the electric signal sampled before the control signal with the signal sampled after the control signal. The difference between these two signals represents the charge from the pixel, while the common component represents the parasitic capacitance charge. This feedback mechanism allows the system to eliminate parasitic capacitance effects without waiting for charge to move, thus resolving the contradiction between reliability and time loss
2Ease of operation
If the switching element is changed from on state to off state, then charge is moved from parasitic capacitance between gate electrode and source electrode, but this charge movement creates interference with the signal that needs to be sampled and held
Solution Approach 1:
The patent extracts the parasitic capacitance signal from the total signal by performing sample-and-hold operations at two different timing points. The signal component related to parasitic capacitance is separated and can be eliminated through differential processing, leaving only the desired pixel charge signal. This extraction approach removes the harmful parasitic capacitance interference while maintaining ease of switching element control
Solution Approach 2:
The patent applies preliminary anti-action by sampling and holding the electric signal both before and after the control signal is applied to the switching element. This preliminary sampling captures the parasitic capacitance charge, allowing it to be subtracted from the subsequent measurement. This preemptive approach counteracts the harmful effect of parasitic capacitance charge movement, enabling clean signal acquisition without interfering with switching element operation
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 a reduction in the time needed to capture radiographic images by efficiently managing the switching elements and signal sampling, improving the overall imaging process.
Implementation Method 1
a conversion element that generates a larger amount of charge as an amount of radiation emitted becomes larger
Data Source
AI summary
A radiography apparatus includes: a radiation detector that includes a plurality of pixels, each of which includes a thin film transistor and which are two-dimensionally arranged, and data lines through which charge accumulated in the connected pixels is transmitted as an electric signal; and a first sample-and-hold unit and a second sample-and-hold unit that sample and hold the electric signal transmitted through the data line. In a case in which the charge accumulated in the pixel is read out, the radiography apparatus performs control such that the thin film transistor is turned off and the first sample-and-hold unit samples and holds a first electric signal transmitted through the data line; and the thin film transistor is turned on and the second sample-and-hold unit samples and holds a second electric signal transmitted through the data line.