Fiber Optic Plate Stand-offs for X-ray Detector Delamination
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Solution Overview
Problem
X or Gamma ray detectors face shear stress and localized delamination due to thermal expansion mismatch between the fiber optic plate and imaging sensor, leading to artifacts in detected images, with existing spacers being ineffective in maintaining a consistent gap and potentially contaminating the detector.
Innovation Solution
The use of stand-offs around the periphery of the fiber optic plate ensures a minimum thickness between the FOP and the imaging sensor, reducing shear stress and delamination risk by creating a consistent gap filled with a coupling material, without introducing spacers into the optical path.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the coupling layer is made thin to maintain MTF, then optical performance is improved, but shear stress increases causing localized delamination
Solution Approach 1:
The coupling layer is segmented into two distinct functional parts: a thin central coupling layer (5-50 microns) maintained to preserve MTF, and peripheral stand-offs (0.5-2mm height) that provide mechanical separation. This segmentation allows the thin central region to maintain optical performance while the peripheral structures prevent shear stress concentration and delamination.
Solution Approach 2:
Stand-off structures serve as intermediary elements between the FOP and imaging sensor perimeter. These stand-offs act as mechanical mediators that absorb thermal expansion differences and prevent direct contact between the FOP edges and sensor surface, thereby reducing shear stress and preventing delamination without compromising the thin central coupling layer.
2Manufacturing precision
If glass spheres are used as spacers to maintain gap, then FOP spacing is improved, but they cluster in valleys and produce optical artifacts
Solution Approach 1:
The spacer function is extracted from the optical path and relocated to the periphery. Instead of placing spacers within the optical path (which cause artifacts), the stand-off structures are positioned at the FOP periphery where they provide mechanical spacing without interfering with light transmission. This extraction eliminates optical artifacts while maintaining FOP spacing.
Solution Approach 2:
The stand-off structures are simple, inexpensive elements that can be easily manufactured and replaced if needed. Unlike complex spacer systems, these stand-offs are straightforward cylindrical or conical structures that provide effective spacing without the complexity of glass sphere assemblies, reducing both manufacturing complexity and potential for optical interference.
3Reliability
If coupling oil is used to reduce shear stress, then delamination is reduced, but it contaminates the detector and dries out over time
Solution Approach 1:
The shear stress mitigation function is extracted from the coupling material and transferred to the stand-off structures. By providing mechanical separation through the stand-offs, the need for thick coupling layers or coupling oils is eliminated, thereby preventing contamination and drying out issues while maintaining delamination resistance.
Solution Approach 2:
The stand-off structures serve as intermediary mechanical elements that mediate between the FOP and imaging sensor. They provide the necessary separation to reduce shear stress without requiring the use of coupling oils that would contaminate the detector. The stand-offs act as a permanent mechanical solution that eliminates the need for fluid coupling materials.
4Manufacturing precision
If the coupling layer thickness matches surface flatness variation, then MTF is maintained, but direct contact occurs at peaks causing damage
Solution Approach 1:
The coupling system is segmented into a thin central coupling layer that maintains MTF and peripheral stand-off structures that provide mechanical protection. This segmentation allows the thin central region to preserve optical performance while the peripheral stand-offs prevent direct contact between the FOP edges and sensor surface, protecting components from damage.
Solution Approach 2:
Different regions of the coupling system have different functional properties: the central region has thin coupling material optimized for optical performance (MTF), while the peripheral region has taller stand-off structures optimized for mechanical protection and shear stress reduction. This local differentiation allows each region to perform its specific function optimally without compromising the other.
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 effectively reduces shear stress and delamination, maintaining the modulation transfer function and preventing optical artifacts, while ensuring uniformity and tailored fit for each detector configuration.
Implementation Method 1
The FOP consists of many individual optical fibers aligned in parallel through which the light is guided
Implementation Method 2
The coupling layer serves to physically attach the FOP to the imager. This creates shear stress due to TCE (Thermal Coefficient of Expansion) mismatch between the FOP (5-8 ppm/C) and the imaging sensor (approximately 3 ppm/C)
Implementation Method 3
the X or Gamma ray radiation penetrates through an object to be examined and encounters a scintillator layer that converts the X or Gamma ray radiation into visible light
Data Source
AI summary
Stand-offs are attached around the periphery of the fiber optic plate (FOP) to ensure a certain minimum thickness between the FOP and the imaging sensor to reduce shear stress and the risk of delamination due to shear stress in an X or Gamma ray detector. A coupling material fills the gap between the FOP and the imaging sensor.