Fabry-Perot Interference Filter with Encapsulating Structure for Thermal Detectors
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Solution Overview
Problem
Existing electromagnetic radiation detection devices with thermal detectors and interference filters face challenges where the properties of the thermal detector are affected by the interference filter, hindering effective multispectral detection.
Innovation Solution
A device featuring a thermal detector housed in a cavity with a Fabry-Perot interference filter, where the filter is positioned away from the detector and formed by semi-reflective mirrors with high- and low-refractive-index layers, ensuring the filter does not contact the detector and maintains the detector's properties, using a thin encapsulating layer that extends above the detector to form part of the semi-reflective mirrors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the interference filter is placed directly on the absorbing membrane to achieve multispectral detection, then spectral selectivity is improved, but the thermal detector properties are affected and degraded
Solution Approach 1:
The patent introduces an encapsulating structure as an intermediary element positioned between the interference filter and the thermal detector. This encapsulating structure houses the thermal detector within a cavity and provides a protective interface, allowing the interference filter to be positioned close to the detector for spectral selectivity while preventing direct contact that would degrade detector properties. The encapsulating structure thus mediates the interaction between the filter and detector, enabling both spectral precision and detector reliability.
2Device complexity
If the interference filter contacts the thermal detector to enable compact positioning, then device complexity is reduced, but the thermal detector properties are affected
Solution Approach 1:
The encapsulating structure serves multiple functions simultaneously: it houses the thermal detector within a protective cavity, positions the interference filter at an optimal distance, provides thermal insulation, and protects the detector from environmental factors. This multi-functional design achieves compact positioning without direct contact, reducing the need for additional complex positioning structures while maintaining detector properties.
3Reliability
If the thermal detector is thermally insulated by suspending it on anchoring pillars to maintain detector performance, then detector properties are preserved, but the device complexity increases
Solution Approach 1:
The patent merges the thermal insulation function with the encapsulating structure. The encapsulating structure itself provides thermal insulation by housing the detector within a cavity that isolates it from the substrate, eliminating the need for separate anchoring pillars and insulating arms. This integration maintains detector properties through thermal insulation while reducing structural complexity by combining multiple functions into a single encapsulating component.
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 configuration allows for selective detection of electromagnetic radiation by filtering wavelengths without affecting the thermal detector's performance, achieving high spectral selectivity and rejection ratios while preserving the detector's properties.
Implementation Method 1
at least one Fabry-Perot interference filter placed level with the encapsulating structure and away from the thermal detector, said filter being formed by first and second semi-reflective mirrors that are separated from each other by a layer called the structured layer
Implementation Method 2
at least one Fabry-Perot interference filter placed level with the encapsulating structure and away from the thermal detector
Implementation Method 3
each semi-reflective mirror including what is called a high-refractive-index layer made of at least one dielectric or semiconductor material
Implementation Method 4
each semi-reflective mirror including what is called a high-refractive-index layer made of at least one dielectric or semiconductor material, said layer having a thickness equal to a multiple of the ratio of a reference wavelength
Data Source
AI summary
A device for detecting electromagnetic radiation includes at least one thermal detector, placed on a substrate; an encapsulating structure forming a cavity housing the thermal detector, including at least one thin encapsulating layer; and at least one Fabry-Perot interference filter, formed by first and second semi-reflective mirrors that are separated from each other by a structured layer. A high-index layer of one of the semi-reflective mirrors is at least partially formed from the thin encapsulating layer.