Shear-Invariant Michelson Interferometer for Single-Shot FT Spectroscopy
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Solution Overview
Problem
Current Fourier transform spectrometers face challenges in achieving high spectral resolution and stability, especially when measuring chaotic movements or turbulent scenes, due to limitations in interferometer design and the need for serial interferogram acquisition, which results in distorted spectra and reduced signal-to-noise ratios.
Innovation Solution
A Michelson-type interferometer with a (2n+1) angle mirror group, such as a triple angle mirror group, is used to generate invariant lateral shear, allowing for simultaneous acquisition of multiple spatial interferograms and enabling single-shot hyperspectral imaging with improved spectral resolution and robustness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional Michelson interferometer is used for spectral measurement, then spectral information can be obtained, but the measurement is distorted by chaotic movements and turbulent scenes, reducing measurement precision
Solution Approach 1:
The invention divides the scene into multiple discrete areas, with each area having its own dedicated interferometer. This segmentation allows each interferometer to independently measure a specific region, making the system robust against chaotic movements and turbulence affecting other areas. The modular architecture isolates measurement errors to individual segments rather than affecting the entire measurement.
Solution Approach 2:
The invention creates multiple copies of the interferometer system, with each copy dedicated to measuring a specific area. These redundant copies ensure that if one measurement is distorted by turbulence or movement, other copies provide alternative measurements that can be used for correction or validation, thereby improving overall measurement precision and reliability.
2Measurement precision
If serial interferogram acquisition is used, then spectral resolution can be achieved, but the measurement process is time-consuming and susceptible to movements during acquisition
Solution Approach 1:
By dividing the scene into multiple areas and assigning one interferometer to each area, the system acquires all interferograms simultaneously rather than sequentially. This parallel acquisition approach eliminates the time delay inherent in serial measurement, allowing complete spectral data to be obtained in a single shot without susceptibility to movements during the acquisition process.
Solution Approach 2:
The invention enables continuous spectral measurement of multiple areas simultaneously, with all interferometers operating in parallel to capture data at the same moment. This continuous parallel operation eliminates the interruptions and time losses associated with sequential scanning, achieving both high spectral resolution and rapid acquisition.
3Area of stationary object
If the interferometer is moved across the object for scanning, then the measurement area can be extended, but misalignment and distortion artifacts increase
Solution Approach 1:
Instead of moving a single interferometer across the object, the invention segments the measurement area into multiple stationary zones, each covered by a dedicated interferometer. This eliminates the need for mechanical scanning and associated alignment issues, as each interferometer remains fixed in its optimal position for measuring its assigned area, thereby maintaining high alignment accuracy across the entire extended measurement area.
Solution Approach 2:
The invention transitions from a one-dimensional scanning approach (moving one interferometer across the object) to a two-dimensional parallel architecture (multiple interferometers covering different areas simultaneously). This dimensional change allows the system to expand the measurement area without introducing the alignment errors and distortion artifacts that result from mechanical movement and scanning.
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 approach enables high wavenumber accuracy and constancy, allowing for undisturbed spectral measurements even in turbulent conditions, with the potential for miniaturization and reduced misalignment issues, resulting in high-quality hyperspectral images with reduced errors.
Implementation Method 1
A shear-invariant dual-beam interferometer, designed as a Michelson-type interferometer with a scanned detector, can be used in a single-shot imaging FT spectrometer... two coherent partial images or partial beams are formed in the interferometer, which undergo image field discrimination before generating at least two spatial interferograms... invariant lateral shear
Implementation Method 2
a triple angled mirror group... consisting of an arrangement of - in total - three at least approximately planar mirrors or at least approximately planar mirror surfaces in a throat or W-shape, each at an angle to each other, which are oriented substantially perpendicular to a common reference plane
Implementation Method 3
A beam splitter with a planar beam splitter surface, wherein the beam splitter is used both for beam splitting, thereby forming two partial beams, and for at least partial beam merging with a lateral shear s between the two partial beams
Implementation Method 4
wherein at least two spatial interferograms of individual selected areas of an image of the object to be detected... are formed simultaneously on the rasterized detector
Implementation Method 5
Fourier transformation of the at least one spatial interferogram acquired in single-shot mode to generate a spectrum
Data Source
Figure 1~2
Figure 3.1~3.6
Figure 4.1~4.3
AI summary
Fourier transform spectrometer, FT spectrometer, comprising: Michelson-type interferometer (601, 602, 603, 604, 605, 606, 607, 608, 609) comprising: at least one beam splitter unit designed to split an incident light beam (EB) from a spatially extended object into a first partial beam (TB1) and a second partial beam (TB2); and to superimpose at least part of the first partial beam (TB1) and the second partial beam (TB2) with a lateral shear (s); a first beam deflection unit designed to deflect the first partial beam (TB1) at least once; a second beam deflection unit designed to deflect the second partial beam (TB2) at least once;wherein at least one of the first beam deflection unit and the second beam deflection unit represents a (2n+1) angle mirror group with (2n+1) mirror surfaces and all (2n+1) mirror surfaces are arranged perpendicular to a common reference plane to deflect the first partial beam (TB1) and/or the second partial beam (TB2) (2n+1) times and wherein the (2n+1)-fold deflection generates the lateral shear (s) between the first partial beam (TB1) and the second partial beam (TB2) and wherein n is a natural number ≥1.;