Single Photon Counting Detectors with Interpixel Communication Logic
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Solution Overview
Problem
Single photon counting detectors face limitations in count rate and charge sharing, particularly at small pitches, which restrict the development of high-resolution detectors due to pile-up effects and charge diffusion, leading to reduced position resolution and inefficiencies in photon detection.
Innovation Solution
The introduction of an interpixel communication logic system with multiple comparators and counters allows for precise determination of photon position by evaluating comparator outputs across neighboring channels, enabling subdivision of sensor diodes into virtual channels smaller than physical diodes, thus overcoming charge sharing and count rate limitations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the pitch of sensor diodes is reduced to increase resolution, then measurement precision is improved, but charge sharing effects worsen due to increased diffusion and electrostatic repulsion
Solution Approach 1:
The patent divides each physical sensor diode into multiple virtual channels by subdividing the physical area into smaller sections. This segmentation allows the system to achieve position resolution finer than the physical pitch by assigning different regions of a single diode to different virtual channels, thereby improving measurement precision without being constrained by the physical diode pitch.
Solution Approach 2:
The patent introduces inter-pixel communication logic as an intermediary component that collects signals from multiple neighboring readout unit cells and determines the most likely photon impact position. This intermediary process enables the system to resolve charge sharing effects by analyzing patterns across multiple channels and identifying the true photon origin, thereby maintaining high position resolution even at small pitches.
2Measurement precision
If the pitch of sensor diodes is reduced to increase resolution, then measurement precision is improved, but count rate capability worsens due to pile-up effects
Solution Approach 1:
By subdividing each physical diode into multiple virtual channels, the patent effectively increases the number of independent detection regions without increasing the physical diode density. This allows photons to be distributed across more channels, reducing the probability of pile-up effects in any single channel and improving count rate capability while maintaining high position resolution.
Solution Approach 2:
The inter-pixel communication logic acts as an intermediary that processes signals from multiple neighboring channels to determine the true photon impact position. This additional processing step helps distinguish between genuine photons and pile-up events by analyzing signal patterns across multiple channels, thereby improving count rate capability without sacrificing measurement precision.
3Measurement precision
If inter-pixel communication logic is implemented to overcome charge sharing, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent segments the functionality of charge sharing mitigation into modular virtual channels within each readout unit cell. Instead of implementing complex analog charge sharing correction circuits, the system uses digital segmentation of detection regions and simple logic to assign photons to virtual channels, reducing device complexity while maintaining high position resolution.
Solution Approach 2:
The patent replaces complex analog signal processing for charge sharing correction with digital inter-pixel communication logic. By using digital counters and logic gates to determine photon positions based on signal patterns across multiple channels, the system achieves high measurement precision with simpler, more scalable digital circuitry instead of complex analog mechanisms.
4Measurement precision
If multiple comparators and counters are added to each readout unit cell for virtual channels, then measurement precision is improved, but manufacturing cost increases
Solution Approach 1:
The patent uses segmentation of physical diode areas into virtual channels, where each virtual channel is represented by existing readout unit cells rather than requiring completely separate physical structures. This approach achieves high position resolution by logical division rather than physical multiplication of components, reducing manufacturing cost while improving measurement precision.
Solution Approach 2:
The patent makes existing readout unit cells multi-functional by enabling them to serve multiple virtual channels through inter-pixel communication. Instead of requiring dedicated hardware for each virtual channel, the same physical readout infrastructure is used for multiple logical channels, achieving high measurement precision without proportionally increasing manufacturing cost.
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 enhances position resolution beyond the physical sensor diode pitch, enabling high-count rate and high-frame rate photon detection with improved efficiency, particularly in small pitch detectors, by accurately locating photon hits and mitigating the corner effect.
Implementation Method 1
the semiconductor sensor, containing an array of photo-detector diodes, also called sensor diodes, where the photon radiation is absorbed and converted into electric charge
Implementation Method 2
when a photon is absorbed in the semiconductor sensor layer, it creates a charge cloud, which due to diffusion and electrostatic repulsion of the charge carriers gets larger while drifting to the collecting electrode
Data Source
AI summary
A system counts photon interactions in an array of photosensitive diodes and addresses the issue of improving position resolution. Every photo-detector diode of the array is connected to a readout unit cell containing a high-gain charge-to-voltage amplifier, a shaper, at least two comparators with independent thresholds and at least one interpixel communication logic, receiving as input signals from comparator outputs of the same readout unit cell and of the neighboring readout unit cells. This logic is then connected to at least one counter, each counter followed by a counter readout. By means of the digital interpixel communication logic and the set of comparators with different thresholds in every readout unit cell, it is possible to determine the photon hit position in the detector with a higher position resolution than the physical photo-detector size including the removal of the corner effect in pixel detectors.