SiPM Trigger Pulse-Width Filtering for Dark Count Rejection
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Solution Overview
Problem
Silicon photomultiplier (SiPM) detector arrays in digital PET systems and LIDAR systems face issues with dark counts, leading to false triggers and increased detector deadtime due to thermally generated carriers, which are not effectively addressed by existing energy-based validation logic.
Innovation Solution
A pulse-width filter is introduced in the trigger network to block pulses with a width less than a threshold, rejecting dark counts before they activate downstream validation and integration circuitry, thereby reducing unnecessary deadtime.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If energy-based validation logic is used to reject dark counts, then false triggers can be filtered, but detector deadtime increases due to unnecessary validation processing
Solution Approach 1:
The patent applies preliminary action by performing pulse width filtering before the trigger is validated and processed by downstream circuitry. The pulse width filter is positioned in the trigger network to block narrow pulses from dark counts early in the signal path, preventing them from activating energy-based validation logic, integration circuitry, and timestamping circuitry. This early rejection reduces detector deadtime by avoiding unnecessary processing of false triggers.
Solution Approach 2:
The patent extracts the pulse width filtering function from the main validation logic and implements it as a separate, dedicated filter in the trigger network. This extraction allows dark count rejection to occur independently and early in the signal path, before triggers are passed to energy-based validation circuitry, thereby eliminating the time penalty of running full validation on all triggers including dark counts.
2Reliability
If integration and timestamping circuitry is activated for every trigger, then complete event processing is performed, but unnecessary reset processing occurs for dark counts
Solution Approach 1:
The pulse width filter performs preliminary rejection of dark count triggers before they can activate integration and timestamping circuitry. By filtering narrow pulses early in the trigger network, the system prevents false triggers from propagating to downstream processing stages, thereby avoiding unnecessary integration, timestamping, and subsequent reset operations that would waste detector time.
3Reliability
If the trigger network processes all SPAD breakdown events, then no detection events are missed, but dark counts introduce false triggers and increase deadtime
Solution Approach 1:
The patent applies local quality by making the trigger network selectively responsive to different types of events based on their pulse characteristics. The pulse width filter introduces a local discrimination criterion (pulse width threshold) that allows genuine detection events to pass through while blocking dark count triggers. This localized filtering within the trigger network maintains detection completeness for valid events while rejecting false triggers early in the processing chain.
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 pulse-width filter efficiently rejects dark counts, reducing detector deadtime and improving imaging and ranging capabilities by enhancing the discrimination of noise events without invoking energy-based validation logic, leading to improved performance in PET and LIDAR systems.
Implementation Method 1
each cell including a single-photon avalanche diode (SPAD) that is reverse biased above its breakdown voltage
Implementation Method 2
a single-photon avalanche diode (SPAD) undergoes breakdown
Implementation Method 3
a pulse-width filter configured to block pulses on the trigger line whose pulse width is less than a threshold width
Data Source
AI summary
The present application relates generally to silicon photomultiplier (SiPM) detector arrays. In one aspect, there is a system including an array of cells each including a single-photon avalanche diode (SPAD) reverse-biased above a breakdown voltage of the SPAD. The system may further include a trigger network configured to generate pulses on a trigger line in response to SPADs of the array undergoing breakdown. The system may still further include a pulse-width filter configured to block pulses on the trigger line whose pulse width is less than a threshold width.