Tunable Notch Filter Spectral Mapping via Inversion
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Solution Overview
Problem
Current spectral imaging systems face challenges such as requiring numerous optical components, complex instrumentation, high cost, and low signal-to-noise ratios due to filtering out most incident radiation, which limits their effectiveness in constructing accurate spectral maps.
Innovation Solution
A tunable notch filter-based mapping spectrometer that electronically tunes the notch filter to selectively attenuate specific spectral bands, allowing most electromagnetic radiation to pass through to the detector array, thereby enhancing signal-to-noise ratios and enabling the construction of spectral maps with higher resolution and accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If spectral filter arrays or tunable bandpass filters are used to select specific spectral bands, then spectral resolution is improved, but most incident radiation is filtered out resulting in weak signals and low signal-to-noise ratios
Solution Approach 1:
Instead of filtering out unwanted wavelengths to achieve spectral selection, the patent inverts the approach by filtering out only a narrow notch of wavelengths and allowing the rest of the spectrum to pass. This is achieved using a tunable notch filter that removes a specific narrow band while transmitting the majority of incident radiation, thereby maintaining high signal-to-noise ratios while still achieving spectral discrimination through computational comparison of multiple notched spectra
Solution Approach 2:
The patent changes the filtering parameter from broad bandpass filtering to narrow notch filtering. By tuning the notch filter to different wavelengths and measuring the resulting spectral notches, the system achieves spectral resolution through parameter variation rather than through traditional broad filtering. The computational processing of multiple notched spectra at different parameter settings enables full spectral reconstruction
2Measurement precision
If traditional spectral imaging systems use numerous optical components and complex spectroscopic instrumentation, then spectral mapping capability is improved, but device complexity and cost increase
Solution Approach 1:
The patent extracts the spectral filtering function from complex optical instrumentation and implements it through a single tunable notch filter. By removing the need for multiple optical components and complex spectroscopic instruments, the system achieves spectral mapping capability with minimal hardware while relying on computational processing to extract spectral information from the notched spectra
Solution Approach 2:
The patent replaces mechanical and optical complexity with electronic and computational simplicity. Instead of using numerous optical components and mechanical spectroscopic instruments, the system uses an electronically tunable notch filter combined with computational algorithms to achieve spectral mapping, thereby substituting mechanical complexity with electronic control and software processing
3Measurement precision
If bandpass filters are used to select spectral bands, then spectral selection is improved, but integration time increases and throughput decreases
Solution Approach 1:
The patent inverts the traditional filtering approach by using notch filters that remove only narrow spectral bands while allowing the majority of radiation to pass through. This enables rapid data acquisition with short integration times, as the high throughput of the notch filter configuration allows much more light to reach the detector compared to traditional bandpass filters
Solution Approach 2:
The patent employs periodic tuning of the notch filter across different wavelengths to acquire spectral information. By rapidly switching the notch filter to different wavelength settings and acquiring multiple notched spectra in sequence, the system reconstructs the full spectrum through computational processing, achieving both spectral selection and rapid data acquisition
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 results in higher signal-to-noise ratios, shorter integration times, and the ability to operate under low light conditions, while maintaining spatial resolution and allowing for dynamic adjustment of spectral filtering parameters, enabling applications in various fields including satellite imaging and medical diagnostics.
Implementation Method 1
A tunable notch filter-based mapping spectrometer that electronically tunes the notch filter to selectively attenuate specific spectral bands, allowing most electromagnetic radiation to pass through to the detector array
Implementation Method 2
directing the spectral components to a detector, which detects and measures the spectrally separated radiation and converts the resulting spectral information to electrical signals
Data Source
AI summary
Methods use a tunable notch filter for constructing a spectral map of electromagnetic radiation in a selected spectral band that is incident on a notch filter for a plurality of time periods. Electromagnetic radiation is passed by an electronically tuned notch filter to a detector array for the plurality of selected time periods, and the detector response is determined. For at least a first selected time period the notch filter is tuned to selectively attenuate the passing of one or more selected sub-bands of electromagnetic radiation in the selected spectral band. Information about the selectively attenuated radiation is determined and used along with information about the radiation passed to the detector array for each time period to construct a spectral map. Electronically tunable notch filters may be made with metamaterials such as patterned graphene.