Fourier Transforms in Spectroscopy

Kauppinen, J.; Partanen, Jari

doi:10.1002/3527600299

Cited by 106 publications

(93 citation statements)

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“…Since the GIFTS FPA contains 128 × 128 detector elements, the distortion caused by the off-axis effects is too great to be neglected. The off-axis pixels are sampled at slightly shorter optical path differences (OPDs), which cause the spectra of these pixels to expand to slightly higher wavenumbers [4]. The correction can be formulated as a fractional sampling rate conversion problem, which can be solved via sinc interpolations, i.e.,…”

Section: ) Off-axis Effectsmentioning

confidence: 99%

GIFTS SM EDU data processing and algorithms

Tian

Johnson

Reisse

et al. 2007

2007 IEEE International Geoscience and Remote Sensing Symposium

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Abstract-The Geosynchronous Imaging Fourier TransformSpectrometer (GIFTS) Sensor Module (SM) Engineering Demonstration Unit (EDU) is a high resolution spectral imager designed to measure infrared (IR) radiances using a Fourier transform spectrometer (FTS). The GIFTS instrument employs three Focal Plane Arrays (FPAs), which gather measurements across the long-wave IR (LWIR), short/mid-wave IR (SMWIR), and visible spectral bands. The raw interferogram measurements are radiometrically and spectrally calibrated to produce radiance spectra, which are further processed to obtain atmospheric profiles via retrieval algorithms. This paper describes the processing algorithms involved in the calibration stage. The calibration procedures can be subdivided into three stages. In the pre-calibration stage, a phase correction algorithm is applied to the decimated and filtered complex interferogram. The resulting imaginary part of the spectrum contains only the noise component of the uncorrected spectrum. Additional random noise reduction can be accomplished by applying a spectral smoothing routine to the phase-corrected blackbody reference spectra. In the radiometric calibration stage, we first compute the spectral responsivity based on the previous results, from which, the calibrated ambient blackbody (ABB), hot blackbody (HBB), and scene spectra can be obtained. During the post-processing stage, we estimate the noise equivalent spectral radiance (NESR) from the calibrated ABB and HBB spectra. We then implement a correction scheme that compensates for the effect of fore-optics offsets. Finally, for off-axis pixels, the FPA off-axis effects correction is performed. To estimate the performance of the entire FPA, we developed an efficient method of generating pixel performance assessments. In addition, a random pixel selection scheme is designed based on the pixel performance evaluation.

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Section: ) Off-axis Effectsmentioning

confidence: 99%

GIFTS SM EDU data processing and algorithms

Tian

Johnson

Reisse

et al. 2007

2007 IEEE International Geoscience and Remote Sensing Symposium

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“…The full-width at half maximum (FWHM) of the sinc function [26] is approximately 1/(2T ) [27], where T is the duration of the time series. We choose the duration of our runs to correspond to a value of FWHM equal to 0.5% of the imposed angular frequency, this corresponds to a run with at least 50/π cycles of oscillations.…”

Section: B Data Analysismentioning

confidence: 99%

Strain-rate frequency superposition in large-amplitude oscillatory shear

2010

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In a recent work, Wyss, et.al. [Phys. Rev. Lett., 98, 238303 (2007)] have noted a property of 'soft solids' under oscillatory shear, the so-called strain-rate frequency superposition (SRFS). We extend this study to the case of soft solids under large-amplitude oscillatory shear (LAOS). We show results from LAOS studies in a monodisperse hydrogel suspension, an aqueous gel, and a biopolymer suspension, and show that constant strain-rate frequency sweep measurements with soft solids can be superimposed onto master curves for higher harmonic moduli, with the same shift factors as for the linear viscoelastic moduli. We show that the behavior of higher harmonic moduli at low frequencies in constant strain-rate frequency sweep measurements is similar to that at large strain amplitudes in strain-amplitude sweep tests. We show surface plots of the harmonic moduli and the energy dissipation rate per unit volume in LAOS for soft solids, and show experimentally that the energy dissipated per unit volume depends on the first harmonic loss modulus alone, in both the linear and the nonlinear viscoelastic regime.

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“…The surface location algorithm was based on first and second moment calculations [16] applied to the average of two axial reflectivity profiles. The first moment, σ 1 , was used to calculate the centroid or weighted mean value of the axial reflectivity profile, while the second moment, σ 2 , was utilized to estimate the surface location: ε = σ 1 -σ 2 ( Fig 5).…”

Section: Surface Detection and Tracking Algorithmmentioning

confidence: 99%

Adaptive ranging for optical coherence tomography

Iftimia¹,

Bouma²,

Boer³

et al. 2004

Opt. Express

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At present, optical coherence tomography systems have a limited imaging depth or axial scan range, making diagnosis of large diameter arterial vessels and hollow organs difficult. Adaptive ranging is a feedback technique where image data is utilized to adjust the coherence gate offset and range. In this paper, we demonstrate an adaptive optical coherence tomography system with a 7.0 mm range. By matching the imaging depth to the approximately 1.5 mm penetration depth in tissue, a 3 dB sensitivity improvement over conventional imaging systems with a 3.0 mm imaging depth was realized.

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Fourier Transforms in Spectroscopy

Cited by 106 publications

References 0 publications

GIFTS SM EDU data processing and algorithms

GIFTS SM EDU data processing and algorithms

Strain-rate frequency superposition in large-amplitude oscillatory shear

Adaptive ranging for optical coherence tomography

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