Photon Counting Circuit Using Pulse Differentiation Against Stacking Errors
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Solution Overview
Problem
Photon counting devices face errors due to charge sharing and stacking phenomena between neighboring pixels, especially in multilevel detection systems, leading to incorrect interpretation of photon energies and materials analysis.
Innovation Solution
A photon counting circuit with an analog stage generating pulsed signals, a digital stage comprising comparators, a differentiator circuit, and logic gates to accurately count photons by combining outputs and reducing stacking errors, allowing real-time processing without post-correction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pixel size is reduced to improve detection sensitivity and avoid photon stacking, then measurement precision is improved, but charge sharing between neighboring pixels increases leading to counting errors
Solution Approach 1:
The invention segments the photon detection and processing functions into distinct stages: analog pulse generation at the pixel level, analog-to-digital conversion, digital pulse differentiation, and energy level classification. This segmentation allows each stage to be optimized independently, maintaining large pixel sizes for reliable charge collection while achieving precise photon counting through digital signal processing.
Solution Approach 2:
The invention introduces an intermediary differentiator circuit that processes the analog pulse signals between the detector and the counter. This differentiator generates derivative signals that clearly distinguish individual photon events, even when multiple photons are detected simultaneously, thereby preventing counting errors without requiring pixel size reduction.
2Measurement precision
If pixel size is reduced to avoid stacking phenomena, then photon counting accuracy is improved, but device complexity increases due to larger number of pixels required
Solution Approach 1:
The invention implements a universal differentiator circuit and energy classification system that can process signals from all pixels in the array through the same processing pipeline. This multi-functional approach allows the system to maintain large pixel sizes while achieving accurate photon counting and energy discrimination without requiring individual processing electronics for each pixel.
Solution Approach 2:
The invention replaces the mechanical approach of using many small pixels with a signal processing approach. Instead of physically dividing the detector into many small elements, the system uses electronic differentiation and digital signal processing to achieve the same effect of resolving individual photon events, thereby reducing device complexity.
3Measurement precision
If post-counting correction is applied to fix counting errors, then measurement precision is improved, but processing time increases and real-time detection is compromised
Solution Approach 1:
The invention performs the differentiation and signal separation action preliminarily, during the photon detection process itself, rather than as a post-processing correction. The differentiator circuit generates derivative signals in real-time that clearly delineate individual photon events, allowing accurate counting without requiring subsequent correction steps.
Solution Approach 2:
The system uses feedback from the derivative signal generation to dynamically adjust the counting process. The differentiator output provides real-time information about photon event boundaries, allowing the system to accurately count photons and classify their energies without time-consuming post-acquisition correction algorithms.
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
The solution effectively reduces counting errors by differentiating pulse periods and combining signals to accurately count photons across varying energy levels, enhancing the precision of photon detection and material analysis without compromising pixel size or requiring post-processing.
Implementation Method 1
an ionizing radiation detector; an analog stage for generating a pulsed signal, each pulse of which has an amplitude proportional to the energy released by an interaction of at least one photon in the detector
Data Source
Figure 1~2
Figure 3~4D
Figure 5A~5D
AI summary
The invention relates to a circuit for counting photons, including: an input terminal (IN) intended to be connected to a detector of ionising radiation; an analogue stage (4) for generating a pulsed signal, each pulse of which has an amplitude proportional to the energy released by an interaction of at least one photon in the detector; and a digital stage (8) including: at least one first comparator for comparing the amplitude of the pulses to a first threshold; a differentiator circuit (9) for determining periods in which the derivative of the pulse signal is of a given sign; at least one first logic gate for combining the outputs of the first comparator and the differentiator circuit; and at least one first counter for counting the number of pulses present on the output of the combining element.