Tunable Interferometric Spectrometer OPD Control
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Solution Overview
Problem
Grating spectrometers have low 1st order diffraction throughput and efficiency curves that are peaked around a single wavelength, limiting their ability to efficiently analyze spectral content across a broad range of wavelengths.
Innovation Solution
A tunable interferometric scanning spectrometer that splits incoming light beams into two optical paths, adjusts the optical path difference through rotatable dispersive elements and movable mirrors, and calculates spectra using a filter function matrix to mitigate coloring across the focal plane, allowing for higher spectral resolution and versatility in use as either a scanning or Fourier spectrometer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a grating spectrometer is used, then spectral analysis can be performed, but the 1st order diffraction throughput is low (approximately 20%) and efficiency is peaked around one wavelength
Solution Approach 1:
The patent changes the fundamental operating parameter from diffraction-based wavelength selection to interferometric optical path difference (OPD) modulation. By varying the OPD between reference and measurement beams across a broad range, the system achieves high throughput across a broad spectral band rather than being peaked at one wavelength, resolving the contradiction between energy loss and adaptability
Solution Approach 2:
The patent replaces the mechanical grating-based diffraction system with an interferometric system using beam splitters, mirrors, and detectors. This substitution eliminates the inherent throughput limitations of grating diffraction while enabling broad spectral coverage through electronic control of optical path differences, simultaneously improving energy efficiency and adaptability
2Loss of energy
If interferometric scanning is used to achieve broad wavelength coverage, then throughput improves, but coloring across the focal plane occurs due to filter function variation
Solution Approach 1:
The patent measures the actual filter function across the focal plane at multiple wavelengths and uses this measured data to compute correction factors. These correction factors are applied as feedback to the spectral reconstruction algorithm, compensating for the coloring effects and restoring spectral accuracy while maintaining the high throughput benefits of interferometric scanning
Solution Approach 2:
The patent performs preliminary characterization of the filter function across the entire focal plane before actual spectral measurements. This preliminary mapping of the filter function variations allows the system to pre-compute correction matrices that are then applied during spectral reconstruction, eliminating coloring artifacts without requiring additional hardware modifications
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 interferometric scanning spectrometer achieves higher throughput and flat efficiency across a broader wavelength range, enabling more accurate spectral analysis and reconstruction with minimal error, and can be used as a hybrid spectrometer for various applications.
Implementation Method 1
The interferometric scanning spectrometer divides incoming light beams into two different optical paths
Implementation Method 2
The spectrometer includes a rotatable dispersive element (e.g., glass plate) in one of the optical paths. In this aspect, the OPD between the optical paths may be adjusted by rotation of the dispersive element
Implementation Method 3
In another aspect, the spectrometer comprises a moveable minor in the other optical path. In this aspect, the OPD between the optical paths may be adjusted by displacement of the minor
Implementation Method 4
detects intensities of the combined light beams across a focal plane (e.g., with a sensor array)
Data Source
AI summary
A tunable interferometric scanning spectrometer is provided. In one aspect of the disclosure, the interferometric scanning spectrometer splits incoming light beams among different optical paths in the spectrometer, recombines the light beams from the different optical paths to produce combined light beams, detects intensities of the combined light beams across a focal plane (e.g., with a sensor array), and calculates a spectra based on the detected intensities and a filter function that is a function of optical path difference (OPD) between the optical paths. In one aspect, the filter function varies across the focal plane. In another aspect, the spectrometer comprises a rotatable dispersive element (e.g., glass plate) in one the optical paths and/or a moveable mirror in the other optical path. In this aspect, the spectrometer may be adjusted away from zero OPD by rotation of the dispersive element and/or displacement of the mirror.