Stacked X-ray Sensor Pixel Arrays with Shielded Circuitry
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Solution Overview
Problem
Existing x-ray sensors face challenges with radiation damage and poor registration between high-energy (HE) and low-energy (LE) arrays, leading to reduced sensitivity and accuracy in material discrimination, especially in dual-energy (DE) or multiple-energy x-ray imaging applications.
Innovation Solution
A multi-energy x-ray detector is designed with vertically parallel two-dimensional pixel arrays, shielded MOS devices, and radiation-hardened CMOS technology, ensuring good alignment and resistance to radiation damage, eliminating the need for fiber optics and enhancing signal quality and registration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If MOS devices are placed close to pixels for signal reception, then signal reception efficiency is improved, but radiation damage susceptibility increases
Solution Approach 1:
The device is segmented into distinct functional regions: pixel arrays for x-ray detection, separate MOS device regions for signal processing, and intermediate shielding structures. This spatial segmentation allows pixels to be exposed to x-rays while MOS devices are protected, resolving the contradiction between proximity for signal reception and separation for radiation protection.
Solution Approach 2:
X-ray shielding structures act as intermediaries between the pixel arrays and MOS devices. These shields selectively block x-rays from reaching the MOS devices while allowing electrical signal transmission, enabling both efficient signal reception and radiation protection simultaneously.
2Reliability
If scintillators and fiber optics are added to protect from radiation damage, then radiation resistance is improved, but sensitivity and compactness are reduced
Solution Approach 1:
The harmful function of x-rays is extracted and blocked by dedicated shielding structures positioned between the pixel arrays and MOS devices. This removes the need for bulky scintillator layers and fiber optic coupling, maintaining device compactness while providing radiation protection.
Solution Approach 2:
The solution moves from a planar layout requiring lateral separation to a three-dimensional stacked architecture with vertical shielding. This allows pixels and MOS devices to be vertically separated with compact horizontal footprint, improving both radiation resistance and compactness.
3Measurement precision
If pixel arrays are closely aligned for good registration, then material discrimination accuracy is improved, but alignment precision requirements increase
Solution Approach 1:
The pixel array is segmented into multiple independent sub-arrays, each with its own readout circuitry. This allows flexible positioning and alignment of individual sub-arrays during assembly, reducing the cumulative alignment errors that would affect a single large array and improving overall registration accuracy.
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 provides improved signal-to-noise ratios, accurate material discrimination, and extended radiation lifetimes, enabling high-sensitivity and accurate dual-energy or multi-energy x-ray imaging without the tradeoffs of previous technologies.
Implementation Method 1
the pixels contain scintillator material that converts x-ray photons to lower-energy or visible photons that are detectable by photodiodes
Implementation Method 2
the pixels contain photodiodes or photoelements that are resistant to radiation damage
Implementation Method 3
an x-ray shielding disposed one of the pixel arrays, positioned to shield the MOS devices on all the pixel arrays
Data Source
AI summary
A dual/multi-energy x-ray image sensor with stacked two-dimensional pixel arrays. Each pixel in one pixel array has a corresponding “overlaid” pixel in the other pixel array. The pixel arrays are stacked parallel and aligned so that they are nominally normal to the x-ray path, and so that a straight path taken by an x-ray photon from the x-ray source to a pixel in one pixel array will also nominally intersect the corresponding pixel in the other pixel array(s). The energy image sensor provides an x-ray scanning detector system, which has increased signal levels and signal-to-noise ratios over dual- or multi-energy detectors using linear diode arrays, specifically when the pixel arrays are TDI pixel arrays that offer higher sensitivities in high-speed line-scan applications. Signal processing circuitry is placed on a periphery of the pixel arrays and shielded. Dual-to-multiple energy applications can be accomplished by increasing the number of stacked pixel arrays.