X-ray detector gain switching gate periodic action
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Solution Overview
Problem
CMOS-based X-ray detectors suffer from leakage currents in activated gain switches and transfer gates, leading to increased noise and reduced dynamic range, especially during long integration times.
Innovation Solution
The gain switches or transfer gates are driven with a low duty cycle and high frequency pulse train, reducing active time and leakage current while maintaining high saturation charge, allowing for low noise and high dynamic range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If gain switches are activated continuously to enable gain selection, then gain settings can be selected, but leakage currents increase causing noise and reduced dynamic range
Solution Approach 1:
The patent applies periodic action by switching gain gates on and off at specific phases during the integration period. Instead of continuous activation, gain switches are activated periodically at predetermined phases, allowing charge redistribution between capacitors only when needed. This periodic switching maintains gain selection capability while minimizing the duration of switch activation, thereby reducing leakage current and its associated noise.
2Reliability
If gain switching gate is switched on for long periods to transfer charge, then charge transfer is complete, but leakage current increases and saturation charge decreases
Solution Approach 1:
The patent applies preliminary action by pre-determining the optimal phases for gain switch activation during the integration period. The gain switches are activated at specific predetermined phases before the integration period ends, ensuring that charge transfer between capacitors is completed in advance. This allows the system to achieve complete charge transfer while keeping the switches off for the majority of the integration time, thereby preserving saturation charge and minimizing leakage.
3Measurement precision
If integration time is extended to capture more X-ray signal, then signal collection improves, but leakage current contribution increases
Solution Approach 1:
The patent applies segmentation by dividing the integration period into multiple phases and activating gain switches only during specific segments rather than continuously. The integration period is segmented such that gain switches are activated only at predetermined phases for brief periods to redistribute charge between capacitors. This segmentation allows extended integration time for improved signal collection while limiting leakage current contribution to specific short time windows when switches are active.
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 minimizes leakage currents, maintaining low noise and high dynamic range even in low sensitivity settings by activating the gain switching transistor or charge transfer gate for short periods, thereby reducing shot noise and preserving image quality.
Implementation Method 1
a photodiode for transforming X-ray radiation into electrical charge
Implementation Method 2
a scintillator for transforming X-ray radiation into another radiation, a photodiode for transforming the other radiation into electrical charge
Implementation Method 3
a first capacitor for being charged by an electrical charge, wherein the first capacitor is electrically connected to the unit for transforming
Data Source
AI summary
The application describes an X-ray detector for use in a medical equipment, wherein the detector comprises an unit for transforming X-ray radiation into electrical charge, a first capacitor for being charged by an electrical charge, wherein the first capacitor is electrically connected to the unit for transforming, a second capacitor for being charged by an electrical charge, and a first gain switching gate, wherein the second capacitor is electrically connected with the unit for transforming if the first gain switching gate is in on-state, wherein the detector is adapted to switch on the first gain switching gate for short periods. Further the application describes an X-ray system comprising a detector according to the invention, wherein the system is adapted for gain selection, wherein the detector is adapted to switch on the first gain switching gate for short periods. Further, the application describes a method for using a detector according to the inventive concept, wherein the first gain switching gate is switched on only for short periods of time for redistribution of electrical charge between the first capacitor and the second capacitor.