Radiation Detector Noise Reduction via Periodic Bias Current
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Solution Overview
Problem
Conventional radiation detectors for X-ray imaging systems suffer from noise issues, particularly 1/f noise, which becomes pronounced at low X-ray flux levels, limiting the effectiveness of ultralow dose imaging.
Innovation Solution
A radiation detector design that includes a scintillator, a photosensor, and an electronics module with a current-to-frequency converter, charge integrator, comparator, and logic module, which generates a pulsed signal correlating with the charge and supplies a bias current to maintain components at an optimal operation point, while an interrupting device stops charge integration during radiation source off-states to suppress noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a bias current is supplied to the current-to-frequency converter to maintain optimal operation point, then the electronics can operate at appropriate point for low X-ray flux, but the bias current generates 1/f noise that becomes pronounced at low X-ray flux levels
Solution Approach 1:
The patent applies periodic action by switching the bias current on and off in synchronization with the X-ray flux. The bias current is supplied only during periods when X-ray flux is present and switched off during off-periods. This periodic modulation ensures the electronics operate at the appropriate point during measurement while eliminating continuous noise generation, thereby resolving the contradiction between maintaining stable operation and reducing noise.
2Measurement precision
If continuous bias current is supplied to maintain electronics operation, then low X-ray flux measurement is enabled, but noise limits ultralow dose imaging
Solution Approach 1:
The patent implements periodic action by synchronizing the bias current supply with the X-ray flux presence. The current-to-frequency converter receives bias current only during X-ray on-periods and is switched off during off-periods. This enables precise low flux measurement when needed while eliminating continuous noise that would limit ultralow dose imaging capability.
Solution Approach 2:
The patent applies the extraction principle by removing the bias current during off-periods of X-ray flux. Instead of maintaining continuous bias current, the system extracts (switches off) the bias current during periods when no X-ray measurement is occurring, thereby eliminating the noise source while preserving measurement capability when X-ray flux is present.
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 design allows for precise determination of X-ray flux over a wide dynamic range and reduces noise by ensuring the bias current only contributes during measurement cycles, enhancing the precision of X-ray flux modulation applications.
Implementation Method 1
a scintillator for converting a flux of radiation particles, such as X-ray photons, into visible light
Implementation Method 2
a photosensor optically coupled to the scintillator... which may comprise a photodiode for converting the visible light output by the scintillator to the charge
Data Source
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AI summary
A radiation detector (100) with a scintillator (102), a photosensor (104) and an electronics module (108) is proposed. The electronics module (108) has a current-to- frequency converter (110) with a charge integrator (112) for generating a pulsed signal having a frequency correlating with a charge generated by the photosensor (104) during a measurement cycle. The electronics module (108) further comprises a current source (120) for generating a frequency offset of the pulsed signal, an interrupting device (134) for interrupting an integration of the charge by the charge integrator (112), and a logic module (124) for determining the frequency of the pulsed signal. Therein, the logic module (124) is configured for determining an off-state of a radiation (404) source and for triggering the interrupting device (134) upon determining the off-state of the radiation source (404).