Radiographic Imaging Array Stable Power Down Method
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Solution Overview
Problem
Radiographic imaging arrays using amorphous silicon (a-Si:H) TFTs face performance issues due to parasitic capacitance, leading to noise and imaging artifacts during power-down and subsequent image captures, as residual charge from scan line feed-through affects the floating node of pixels.
Innovation Solution
Implementing a controlled power-down method where the power for the bias control circuit, address control circuit, and signal sensing circuit are sequentially removed, ensuring a conductive path to drain unwanted charge from the floating node, and maintaining the photodiodes in a low bias state to reduce artifacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If power is removed from all circuits simultaneously during power-down, then the power-down process is simple and fast, but residual charge accumulates on the floating node causing noise and imaging artifacts
Solution Approach 1:
The power-down process is segmented into distinct sequential stages: first disabling the scan line drive circuitry, then disabling the readout circuitry, and finally disabling the bias circuits. This segmentation ensures that at each stage, charge can be properly drained from the floating node before the next circuit is powered down, preventing residual charge accumulation and imaging artifacts while maintaining a relatively fast overall power-down process.
Solution Approach 2:
Before completely removing power from the imaging array, the method performs preliminary actions by first disabling the scan line drive circuitry while maintaining power to other circuits. This preliminary step allows the floating node to be discharged through the still-powered readout and bias circuits, preventing charge accumulation before the final power removal occurs.
2Ease of manufacture
If a-Si:H TFT is used as the switching element, then the imaging array can be manufactured with available technology, but parasitic capacitance from the TFT affects performance and generates noise
Solution Approach 1:
The method converts the harmful effect of parasitic capacitance in a-Si:H TFTs into a beneficial outcome by designing a power-down sequence that utilizes the TFT's capacitance to hold charge temporarily during the transition. By disabling circuits in a specific sequence, the parasitic capacitance becomes part of the charge drainage mechanism, ensuring that residual charge is properly managed and converted into a controlled state rather than causing noise and artifacts.
3Loss of energy
If the imaging array is powered down completely, then energy consumption is reduced, but the array requires longer initialization time during subsequent power-ups due to residual charge
Solution Approach 1:
The method performs preliminary charge drainage actions during the power-down sequence itself, rather than requiring separate initialization actions after power-up. By systematically disabling circuits in an order that ensures charge is drained from the floating node before each circuit is powered down, the array reaches a clean zero-charge state that requires minimal initialization time upon subsequent power-up, thus reducing both energy consumption and initialization time.
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 results in a more uniform shut-down state and reduced noise, minimizing imaging artifacts and enabling faster initialization during subsequent power-ups, thus improving the quality of radiographic images.
Implementation Method 1
The photoelectric conversion element 120 or photosensor is sensitive to incident radiation and can generate a number of charge carriers where the number depends on the radiation dosage.
Data Source
AI summary
Embodiments of radiographic imaging systems; radiography detectors and methods for using the same can include radiographic imaging array that can include a plurality of pixels that each include a photoelectric thin-film conversion element coupled to a conversion thin-film switching element. In certain exemplary embodiments, a radiographic imaging array can include a bias control circuit to provide a bias voltage to the photosensors for a portion of the imaging array, an address control circuit to control scan lines, where each of the scan lines is coupled to a plurality of pixels in the portion of the imaging array; and a signal sensing circuit connected to data lines, where each of the data lines is coupled to at least two pixels in the portion of the imaging array, where power of the bias control circuit, the address control circuit, and the signal sensing circuit is not removed simultaneously.