Wedge-Shaped Optical Filter for Spectrometer Fabrication
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Solution Overview
Problem
Fabricating a photospectrometer with an array of Fabry-Perot filters of unique thicknesses over addressable photodiodes is complex and costly due to multiple etching and deposition steps required for transparent layers, and standard Fabry-Perot filters face challenges in achieving high finesse and narrow bandwidth, with issues like low transmission, especially in the blue spectrum, and contamination risks.
Innovation Solution
A linearly variable wedge-shaped thin film multi-layer optical coating filter with a single partially reflective metal layer sandwiched between two transparent layers of alternating dielectric materials, allowing for a single deposition process and providing high transmission and narrow bandwidth without the need for multiple etching steps, using materials like aluminum for cost-effectiveness and ease of fabrication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple etching and deposition steps are used to fabricate Fabry-Perot filters with unique thicknesses, then the photospectrometer can achieve wavelength discrimination, but the fabrication process becomes complex and costly
Solution Approach 1:
The patent combines multiple discrete Fabry-Perot filters into a single integrated filter structure with multiple reflective surfaces at different depths within a transparent matrix. This merging approach eliminates the need for multiple separate etching and deposition steps while maintaining the wavelength discrimination capability through the stacked reflective surface configuration
Solution Approach 2:
The invention transitions from a two-dimensional planar filter structure to a three-dimensional stacked configuration with reflective surfaces at different depths. This dimensional change allows multiple filtering functions to be integrated within a single volume, reducing fabrication complexity while preserving spectral selectivity
2Device complexity
If standard Fabry-Perot filters are used, then the structure is simple, but transmission is low especially in the blue spectrum
Solution Approach 1:
The patent uses a composite structure combining a transparent matrix material with multiple reflective surfaces made of different materials (metallic and dielectric layers). This composite approach optimizes light transmission across the visible spectrum, particularly improving blue spectrum transmission while maintaining structural simplicity
Solution Approach 2:
The invention modifies the optical parameters of the filter by adjusting the refractive indices, thicknesses, and material compositions of the transparent matrix and reflective surfaces. These parameter changes enhance transmission efficiency across different wavelengths while preserving the simple overall structure
3Measurement precision
If multiple transparent layers with different thicknesses are fabricated, then unique wavelength filtering is achieved, but fabrication time and cost increase
Solution Approach 1:
The patent merges multiple individual filter layers into a single integrated structure where multiple reflective surfaces are embedded within one transparent matrix. This consolidation reduces the number of fabrication cycles from multiple separate depositions to a single integrated fabrication process, improving productivity while maintaining precise wavelength filtering
Solution Approach 2:
The invention segments the filtering function into multiple reflective surfaces at different depths within a single matrix structure. This segmentation allows each surface to contribute to specific wavelength filtering while the entire structure is fabricated in one process, eliminating the need for sequential layer fabrication
4Measurement precision
If Fabry-Perot filters are used, then wavelength selectivity is achieved, but contamination risks arise from multiple deposition steps
Solution Approach 1:
The patent combines multiple reflective surfaces and transparent layers into a single integrated filter structure that can be fabricated in one deposition process. This merging eliminates the repeated exposure to deposition environments that causes contamination, while maintaining wavelength selectivity through the stacked reflective surface configuration
Solution Approach 2:
The invention converts the potential harm of contamination from multiple deposition steps into a benefit by designing a structure where all layers are deposited simultaneously or in sequence within a single controlled environment. This approach uses the deposition process itself to create a sealed, contamination-resistant structure
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 achieves high transmission efficiency across the visible spectrum with adjustable bandwidth, reduces fabrication time and cost, and eliminates contamination risks, providing a more efficient and cost-effective solution for photospectrometers with improved wavelength sensitivity.
Implementation Method 1
a linearly variable wedge-shaped thin film multi-layer optical coating filter with a single partially reflective metal layer sandwiched between two transparent layers of alternating dielectric materials
Data Source
AI summary
A light filter includes exactly one partially reflective layer having a top and a bottom and a wedge-shaped profile defining a wedge direction. First and second transparent layers are disposed on the top and bottom, respectively, of the partially reflective layer, each transparent layer including at least two dielectric layers of two different materials, each dielectric layer having a wedge-shaped profile oriented in the wedge direction. A photospectrometer including a light filter with the wedge-shaped profile is also disclosed.