Light Guide Array for PET Detector SPAD Crosstalk Reduction
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Solution Overview
Problem
Conventional PET scanner SiPMs face challenges in maximizing photon detection efficiency while minimizing afterpulsing and optical crosstalk events, which increase with the size of the SPAD area, affecting other parameters.
Innovation Solution
The implementation of an optical light guide array between SPAD microcells and an optically transparent plate, where an optical coupler adhesive forms beads that direct light onto the active area of the SPAD, optimizing light coupling and reducing crosstalk through precise alignment and geometry design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the area of the SPAD is increased to improve photon detection efficiency, then the PDE is enhanced, but the probabilities of afterpulsing events and optical crosstalk events increase
Solution Approach 1:
The invention introduces optical isolation structures (light guides, reflective surfaces, and absorptive materials) that segment the optical path between adjacent microcells. These structures divide the optical space into isolated zones, preventing photons from one microcell from reaching neighboring microcells, thereby reducing optical crosstalk while maintaining large SPAD areas for high detection efficiency
Solution Approach 2:
The invention employs intermediary optical elements such as light guides and reflective surfaces positioned between adjacent microcells. These intermediaries redirect photons away from neighboring microcells and toward the active area of their originating microcell, effectively mediating the optical interaction to reduce crosstalk while preserving detection efficiency
2Reliability
If the area of the SPAD is increased to improve photon detection efficiency, then more photons are detected, but the area required for electronics and traces increases proportionally
Solution Approach 1:
The invention applies local quality optimization by concentrating the photosensitive area in specific regions while using specialized optical structures in other regions. The SPAD active area is optimized for photon detection, while surrounding areas are dedicated to optical isolation and light guiding functions, allowing each zone to serve its specific purpose efficiently
Solution Approach 2:
The invention transitions from a two-dimensional planar layout to a three-dimensional optical structure by incorporating light guides and reflective surfaces that extend vertically and laterally. This dimensional change allows optical isolation and light routing to occur in additional spatial dimensions, reducing the footprint required for electronics and traces while maintaining large effective detection areas
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 photon detection efficiency by ensuring that a greater fraction of photons interact with the photosensitive area, reducing afterpulsing and crosstalk events, and improving alignment accuracy between scintillator and photodiode elements.
Implementation Method 1
an optical coupler adhesive forms beads that direct light onto the active area of the SPAD
Implementation Method 2
optical light guide array between SPAD microcells and an optical transparent plate
Data Source
AI summary
A photon detector having an optical transparent plate and photodiode array interconnected by an optical light guide array. The optical light guide array including elements providing a transmission line between the optical transparent plate and the photodiode array, where the position of one or more optical light guide elements is formed to adjust for a miss-registered photodiode individual element. A method for assembling the photon detector includes depositing a non-wetting film on opposing surfaces of the optical transparent plate and/or photodiode array, altering the deposited non-wetting film in regions of individual photodiode elements, dispensing an optical coupler adhesive on the optical transparent plate and photodiode array to form adhesive beads, aligning the opposing surfaces, assembling the opposing surfaces so that the corresponding optical coupler adhesive beads contact each other, and curing the optical coupler adhesive to form a structurally merged photon detector having optical light guide elements.