X-ray Detector Noise Reduction via Rheobase Voltage Reset
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Solution Overview
Problem
X-ray detecting apparatuses face image delay issues when displaying motion pictures due to increased electrical noise, which decreases detective quantum efficiency (DQE), especially when reducing X-ray irradiation levels for motion picture display.
Innovation Solution
The solution involves a driving method that samples first and second data voltages corresponding to rheobase and bias voltages, respectively, and resets the rheobase voltage after noise sampling to minimize electrical noise, using a low temperature polysilicon TFT for switching and reset transistors, and a reset driver that applies a reset signal until the end of a frame to reduce image delay.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If X-ray irradiation levels are reduced for motion picture display, then patient safety is improved, but electrical noise increases and detective quantum efficiency decreases
Solution Approach 1:
The patent applies preliminary action by resetting the rheobase voltage in advance (during the period from noise sampling completion to frame end) before the next X-ray signal arrives. This pre-resetting ensures that when reduced-level X-ray irradiation occurs, the photodiode starts with a clean voltage state, preventing noise accumulation and maintaining detective quantum efficiency even at lower irradiation levels.
2Object-affected harmful factors
If X-ray irradiation levels are reduced for motion picture display, then patient safety is improved, but image quality deteriorates due to increased electrical noise
Solution Approach 1:
The reset operation is performed in advance during the interval between noise sampling completion and frame end, preparing the photodiode for the next low-level X-ray signal. This preliminary voltage reset prevents noise from affecting image quality when reduced irradiation is used for motion picture display.
Solution Approach 2:
The patent separates the noise sampling operation from the actual signal detection by performing noise sampling at a specific timing point and then resetting the rheobase voltage. This extraction of the noise component allows the system to maintain image quality by removing electrical noise effects even when using reduced X-ray irradiation levels.
3Device complexity
If conventional sampling methods are used without timely reset, then device complexity is reduced, but image delay increases
Solution Approach 1:
The patent implements periodic action by systematically performing noise sampling followed by rheobase voltage resetting at regular intervals (from noise sampling completion to frame end). This periodic reset cycle ensures that each frame starts with a clean state, preventing image delay while maintaining relatively simple device architecture using standard TFT transistors.
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 reduces electrical noise, improving detective quantum efficiency and minimizing image delay by ensuring the rheobase voltage is reset before the next frame, thus enhancing the quality of X-ray motion picture display.
Implementation Method 1
a photodiode generating a first current corresponding to visible rays incident through a scintillator layer
Implementation Method 2
a switching transistor switching a current corresponding to the rheobase voltage to generate the first data voltage
Data Source
AI summary
An apparatus for detecting X-rays and a driving method of the X-ray detecting apparatus. The driving method includes sampling a first data voltage corresponding to a rheobase voltage and a bias voltage, the rheobase voltage being generated by a current from a photodiode, sampling a second data voltage corresponding to the bias voltage after resetting the rheobase voltage, and resetting the rheobase voltage from the time that the sampling of the second data voltage is finished to the time that a corresponding frame is finished. An image delay generated when an X-ray motion picture is displayed may be minimized.