Radiographic Detector Bias Current Compensation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Radiographic image detecting apparatuses, such as FPDs, face challenges in securing a wide dynamic range due to varying electric charge accumulation in photoelectric conversion elements, especially at low radiation doses, leading to small signal amplitudes and degraded image quality.
Innovation Solution
A radiographic image detecting apparatus with a current detector to measure bias currents and adjust amplification gains in real-time, using a controller to correct signal amplitude based on detected current values, ensuring appropriate output even with voltage drops across resistors, and incorporating a second amplifying circuit to enhance signal quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a resistor with large resistance value is connected in series to the bias line to detect bias current, then the bias current can be detected, but voltage drop occurs across the resistor which lowers the photosensitivity of the photoelectric conversion element and decreases signal amplitude
Solution Approach 1:
The bias line is divided into two segments: a first bias line connected directly to the photoelectric conversion element and a second bias line connected through the resistor to a reference potential. This segmentation allows the bias current to be detected while minimizing voltage drop impact on the photoelectric conversion element's photosensitivity.
Solution Approach 2:
The resistor is introduced as an intermediary component in the bias line to enable bias current detection. By placing the resistor in a specific configuration (connected between the bias line and reference potential), it serves as a mediator that allows current measurement without significantly interfering with the primary function of biasing the photoelectric conversion element.
2Reliability
If the gain of the amplifying circuit is adjusted based on detected bias current, then the signal amplitude can be maintained, but the device complexity increases due to additional control circuits
Solution Approach 1:
A feedback mechanism is implemented where the detected bias current information is fed back to the amplifying circuit control unit. This feedback loop enables automatic adjustment of the amplifying circuit's gain based on the actual bias current, maintaining signal amplitude while providing adaptive control.
Solution Approach 2:
The amplifying circuit's gain is made dynamic rather than fixed. The gain adjustment unit can change the amplifying circuit's gain in real-time based on the detected bias current, allowing the system to adapt to varying operating conditions and maintain optimal signal amplitude.
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 solution enables the production of high-quality radiographic images by maintaining signal amplitude and securing a wide dynamic range, preventing image degradation caused by voltage drops and varying radiation doses.
Implementation Method 1
photoelectric conversion elements generates electric charges in response to radiation applied thereto and then converts the generated electric charges into electric signals
Implementation Method 2
a scintillator or the like converts radiation applied thereto into an electromagnetic wave such as visible light or the like having a wavelength other than the wavelength of the radiation
Implementation Method 3
a voltage drop across the resistor is measured by a differential amplifier, because the bias currents are weak, i.e., in the order of microampere
Data Source
AI summary
A radiographic image detecting apparatus and a radiographic image capturing system are provided. The radiographic image detecting apparatus includes photoelectric conversion elements for generating electric charge by emission of radiation, a bias line through which a bias voltage is supplied to the photoelectric conversion elements, a power supply for applying the bias voltage to the photoelectric conversion elements through the bias line, a current detector for detecting a bias current flowing through the bias line based on a voltage drop across a resistor inserted in the bias line, a first amplifying circuit, a second amplifying circuit connected to an output of the first amplifying circuit, and a controller for correcting the electric signal by increasing a gain of the second amplifying circuit depending on decrease in a sensitivity of the photoelectric conversion element, the decrease being caused by the voltage drop.