Tilted Mirror Fabry-Perot Filter for Tunable Spectral Resolution
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Solution Overview
Problem
Prior-art tunable spectral filters are often slow, have limited tuning range, poor spectral resolution, and are complex to implement, making them inadequate for wide spectral range applications such as hyperspectral imaging and spectrometry.
Innovation Solution
A Fabry-Perot cavity-based spectral filter with one planar mirror tilted relative to the other, allowing a linear gradient in cavity length, enabling control over both the absolute wavelengths and spectral range, and using vertical actuators to control mirror separation and tilt, resulting in high spectral resolution and tunability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional tunable Fabry-Perot cavity is used, then the center wavelength can be tuned, but the tuning range is limited and the spectral resolution is poor
Solution Approach 1:
The patent applies dynamics by making the cavity length continuously variable through a deformable spacer that can be dynamically adjusted. This allows the Fabry-Perot cavity to transition from a fixed-geometry structure to one where the cavity length can be changed in real-time, enabling both high spectral resolution (when cavity length is precisely controlled) and wide tuning range (when cavity length is varied across multiple values).
Solution Approach 2:
The patent changes the physical parameter of cavity length to resolve the contradiction. By using a deformable spacer, the cavity length can be varied continuously, which simultaneously enables wide spectral tuning range while maintaining the ability to achieve high spectral resolution at any desired wavelength through precise control of the cavity length parameter.
2Adaptability or versatility
If the cavity length is changed to tune the wavelength, then the wavelength can be adjusted, but the response speed is slow
Solution Approach 1:
The patent replaces traditional mechanical adjustment mechanisms (such as motorized stages or piezoelectric actuators) with an electrostatic actuation system. The deformable spacer is actuated by electrostatic forces, which respond much faster than mechanical systems. This substitution enables rapid wavelength tuning while maintaining precise control over the cavity length.
Solution Approach 2:
The patent utilizes the phase transition or state change concept by employing a deformable spacer that can rapidly change its physical state or configuration in response to electrostatic actuation. This allows the cavity length to be adjusted quickly without the inertial limitations of mechanical systems, achieving fast wavelength tuning.
3Measurement precision
If prior-art tunable spectral filters are implemented, then some spectral filtering is achieved, but the device complexity increases
Solution Approach 1:
The patent merges multiple functions into a single integrated structure. The deformable spacer simultaneously serves as the tuning mechanism and the structural element defining the cavity length, eliminating the need for separate mechanical adjustment mechanisms. This integration reduces device complexity while maintaining spectral filtering capability and tunability.
Solution Approach 2:
The deformable spacer acts as a multi-functional element that provides both structural support for the Fabry-Perot cavity and the tuning mechanism for wavelength adjustment. This universal component performs multiple functions (mechanical support, cavity length definition, and active tuning), thereby reducing the overall device complexity compared to systems requiring separate components for each function.
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 solution provides high spectral resolution over wide spectral ranges, enhancing the performance of hyperspectral imaging systems and spectrometers by allowing precise control over the spectral content and resolution, improving the quality factor of the cavity and sensitivity.
Implementation Method 1
Light having wavelength, λ, will resonate back and forth between the mirrors inside the optically resonant cavity when its cavity length, L, is equal to an integer number, N, of half-wavelengths (i.e., when L=Nλ/2) and be transmitted through the cavity with low loss. At the same time, light characterized by other wavelengths will be reflected by the FP cavity.
Implementation Method 2
one planar mirror that can be tilted relative to the other planar mirror along at least a first direction to realize a cavity length having a linear gradient along that direction. At each point along the first direction, therefore, the FP cavity has a different cavity length and passes a different wavelength at that point.
Data Source
Figure 1
Figure 2A~2B
Figure 3A~3C
AI summary
A Fabry-Perot cavity-based spectral notch filter is disclosed, where the filter is operative for providing an output optical signal whose spectral content is spatially dispersed along at least one direction, while also controlling the spectral position and spectral range of the output light. In some embodiments, the spectral filter is integrated with a detector arrays to realize a compact, high-resolution spectrometer that can rapidly acquire the absorption spectrum of a sample with high sensitivity.