Bonded Silicon Infrared Filter for Compact Spectral Imaging
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Solution Overview
Problem
Existing Fabry-Perot cavity devices in the mid-infrared and thermal infrared bands are unable to provide hyperspectral imaging, and existing FPI devices are difficult to fabricate and complicated in techniques, limiting their application in miniaturized and low-cost infrared spectral imaging.
Innovation Solution
A tunable infrared optical filter device is designed with first and second mirrors bonded to form a cavity, using distributed Bragg reflectors composed of silicon films, which are formed by bonding silicon films to reduce device size and simplify fabrication, and include electrodes for mirror movement to achieve tunability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If beam splitting technology based on wheel filters or prisms is used for spectral imaging, then spectral imaging capability is achieved, but device size becomes large and cost increases
Solution Approach 1:
The patent uses thin film mirrors formed by micromachining techniques to create a compact Fabry-Perot interferometer. The thin film movable mirror is suspended above the substrate, enabling miniaturization while maintaining spectral imaging functionality. This directly addresses the contradiction by replacing bulky wheel filters or prisms with thin-film-based optical elements.
Solution Approach 2:
The patent replaces the mechanical beam splitting system (wheel filters or prisms) with an electro-optical system based on Fabry-Perot interference. The movable mirror is actuated by electrostatic forces from underlying electrodes, substituting mechanical rotation or translation with electrical control, thereby reducing device size and complexity.
2Ease of manufacture
If bulk-micromachined FPI device is used, then device structure is formed, but fabrication complexity increases and cost increases due to cantilever beam structure
Solution Approach 1:
The patent extracts the movable mirror structure from the substrate by releasing it through etch holes, creating a suspended thin film mirror. This separates the mirror function from the substrate, eliminating the need for complex cantilever beam structures while simplifying fabrication. The mirror is held in place only by the release holes, reducing structural complexity.
Solution Approach 2:
The patent changes the structural parameters of the movable mirror from a bulk cantilever beam to a thin film suspended structure. This parameter change simplifies the fabrication process by using standard micromachining techniques and reduces the overall device complexity while maintaining the required mechanical properties for tuning.
3Ease of operation
If bulk-micromachined FPI device with elastic structure is used, then device functionality is achieved, but intrinsic stress and deformation occur in mirrors due to elastic structure influence
Solution Approach 1:
The patent segments the support structure into discrete etch holes rather than a continuous elastic structure. This segmentation eliminates the intrinsic stress and deformation caused by continuous elastic structures while still providing the necessary support and tuning functionality. The mirrors are held at discrete points, improving their structural stability.
4Volume of stationary object
If surface-micromachined FPI device is used, then device size is reduced, but fabrication difficulty increases and techniques become complicated
Solution Approach 1:
The patent merges the mirror formation and release processes into a single micromachining sequence. The thin film mirrors are formed and released in one fabrication run, combining multiple steps into a unified process. This reduces fabrication difficulty while achieving miniaturization, as the mirrors are created and released simultaneously without requiring separate complex assembly steps.
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 device achieves miniaturization, simplifies fabrication, and enables large-scale commercial production of infrared spectral imaging equipment, reducing costs and complexity.
Implementation Method 1
each of the first mirror and the second mirror respectively are distributed Bragg reflectors formed by bonding silicon films
Implementation Method 2
tunable infrared optical filter device... Fabry-Perot interference
Implementation Method 3
A surface of a position where the first mirror and the second mirror are bonded to each other is provided with an electrode for driving the first mirror or the second mirror to move
Data Source
AI summary
A tunable infrared optical filter device, includes a first mirror and a second mirror bonded to each other to form a cavity therebetween. A surface of a position where the first mirror and the second mirror are bonded to each other is provided with an electrode for driving the first mirror or the second mirror to move, and each of the first mirror and the second mirror is a distributed Bragg reflector formed by bonding silicon films. The silicon film may be formed by machining the silicon film wafer, to form the distributed Bragg reflector composed of the two silicon films and the chambers therebetween. The distributed Bragg reflector may also be formed by bonding the silicon film and the silicon film of an SOI wafer.