Hybrid Interference Filter for Mini-Spectrometers
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Solution Overview
Problem
Existing interference filters face challenges in achieving high transmission at desired wavelengths with narrow responses and large rejection bands while maintaining stability in ambient conditions, leading to increased complexity and cost due to sidebands and material instability.
Innovation Solution
A hybrid interference filter design incorporating a metal mirror, a dielectric mirror, and a spacer, where the metal mirror is protected by the spacer and dielectric mirror, allowing for varying spacer thickness to tune selectivity across a wide range of wavelengths without altering the mirror thicknesses, thereby reducing the number of layers and additional filters needed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If dielectric mirrors are used in interference filters, then transmission at desired wavelength is high, but sidebands are transmitted causing narrow rejection band
Solution Approach 1:
The patent combines a dielectric mirror and a metal mirror in a single interference filter structure. The dielectric mirror provides high transmission at the desired wavelength, while the metal mirror contributes to broadening the rejection band and suppressing sidebands. This merging of two different mirror types resolves the contradiction by allowing both high transmission and wide rejection band to coexist in one filter.
2Reliability
If metal mirrors are used in interference filters, then rejection band is broad and sidebands are suppressed, but transmission at desired wavelength is reduced
Solution Approach 1:
The patent combines a dielectric mirror and a metal mirror in a single interference filter structure. The dielectric mirror provides high transmission at the desired wavelength, while the metal mirror contributes to broadening the rejection band and suppressing sidebands. This merging of two different mirror types resolves the contradiction by allowing both high transmission and wide rejection band to coexist in one filter.
3Illumination intensity
If silver is used as metal mirror material, then optical performance is optimal, but stability in ambient conditions deteriorates
Solution Approach 1:
The patent uses a composite structure combining dielectric materials and metal (silver) mirror materials. The dielectric layers serve as protective encapsulation for the silver mirror, preventing direct exposure to ambient conditions that would cause degradation. This composite approach allows the system to enjoy the optimal optical performance of silver while the dielectric protective layers maintain stability in ambient conditions.
4Reliability
If additional high pass and low pass filters are added to remove sidebands, then rejection band width increases, but device complexity increases
Solution Approach 1:
The patent merges the functions of the interference filter and sideband suppression into a single integrated structure by combining dielectric and metal mirrors. This eliminates the need for separate high pass and low pass filters that would otherwise be required to remove sidebands, thereby reducing device complexity while maintaining wide rejection band.
5Reliability
If thickness of dielectric mirrors is varied to eliminate sidebands, then rejection band improves, but manufacturing complexity increases
Solution Approach 1:
The patent uses a composite structure where the metal mirror layer provides inherent sideband suppression properties. This allows for more consistent and easier manufacturing compared to precisely controlling the thickness of multiple dielectric mirror layers, as the metal layer can be deposited with less stringent thickness control requirements while still achieving the desired optical performance.
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 and narrow spectral responses with large rejection bands, simplifying production and reducing costs by allowing spectral tuning through spacer thickness variation alone, while protecting the metal mirror from degradation.
Implementation Method 1
The metal mirror and the dielectric mirror are configured to enable optical interference in the spacer to select a light component of an incident light to be transmitted
Data Source
AI summary
The invention relates to an interference filter (100) for receiving an incident light (135) and selecting a light component of the incident light to be transmitted (115). The interference filter (100) includes a metal mirror (110), a dielectric mirror (130), and a spacer (120) placed between the metal mirror (110) and the dielectric mirror (130). The metal mirror (110) and the dielectric mirror (130) are configured to enable optical interference in the spacer (120) to select the light component of the incident light to be transmitted (115). Using one metal mirror and one dielectric mirror allows achieving a spectral response with high finesse and large rejection band while reducing the total number of layers in the filter and reducing the number of additional filters necessary for removing transmitted side bands, relative to prior art approaches.