Phase Function Effects on Identification of Terahertz Spectral Signatures Using the Discrete Wavelet Transform

Khani, Mahmoud E.; Winebrenner, D. P.; Arbab, M. Hassan

doi:10.1109/tthz.2020.2997595

Cited by 30 publications

(23 citation statements)

References 25 publications

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“…results in an effective zero-phase MODWT pyramid algorithm. Accordingly, features in the wavelet domain will be in alignment with those in the input signal [30], as it is shown in Fig. 3(b).…”

Section: ) Maximal Overlap Discrete Wavelet Transformmentioning

confidence: 98%

“…Inverse MODWT pyramid algorithm After finding the wavelet and scaling coefficients of the derivative of THz reflectivity, we correct the phase distortions caused by the wavelet and scaling filters in the decomposition stage [30].…”

Section: Reverse Circular Advancementmentioning

confidence: 99%

“…The wavelet coefficients associated with these resonant frequencies, marked by the black circles, demonstrate a decomposition leveldependent shift with respect to their correct positions. These misalignments are originated from the phase functions of the wavelet and scaling filters used in the wavelet transform's pyramid algorithm [28], [30]. Especially when choosing the wavelet shrinkage thresholds from a specific interval at each decomposition level [41], these misalignments can lead to selecting erroneous threshold values.…”

Section: ) Maximal Overlap Discrete Wavelet Transformmentioning

confidence: 99%

“…However, among the Daubechies orthogonal wavelet filters introduced in [39], the least asymmetric wavelets demonstrate the most symmetrical shapes and therefore the highest phase function linearity. Consequently, for the LA(L) mother wavelets, where L represents the mother wavelet length, it has been shown that advancing the jth-level wavelet coefficients by 2 j−1 (L − 1) − ν, where ν is given by [30], [37],…”

Section: ) Maximal Overlap Discrete Wavelet Transformmentioning

confidence: 99%

“…Importantly, THz spectroscopy in scattering-mitigated off-specular geometries will enable stand-off detection applications in arbitrary detection angles, which has not been possible so far due to the aforementioned spectral artifacts. For instance, by increasing the surface roughness, the increase in scatteringinduced artifacts in the wavelet domain diminishes the ability of wavelets for identifying the resonant signatures in previous algorithms [23], [28], [30].…”

Section: Introductionmentioning

confidence: 99%

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Chemical Identification in the Specular and Off-Specular Rough-Surface Scattered Terahertz Spectra Using Wavelet Shrinkage

Khani

Arbab

2021

IEEE Access

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We present the development and implementation of a novel wavelet shrinkage technique for the retrieval of obscured characteristic resonant signatures in the scattered terahertz (THz) reflectivity of molecular crystals. In this implementation, the wavelet basis functions associated with the absorption features were identified using the second-order total variation of the wavelet coefficients. Additionally, wavelet coefficients at certain scales were modified using the phase function corrections and wavelet hard thresholding. Reconstruction of the original spectra using these modified wavelet coefficients yielded the exact resonant frequencies of the chemicals, which were otherwise unrecognizable in the spectral artifacts of the rough surface scattering. We examined the robustness of this method over controlled levels of rough surface scattering, validated using the Kirchhoff approximation, in spectroscopic targets made from αlactose monohydrate and 4-aminobenzoic acid (PABA), which have close spectral lines. We successfully retrieved the spectral absorption fingerprints in both specular and off-specular reflection geometries. This technique can be utilized for stand-off material characterization using the THz reflection spectroscopy in uncontrolled environments and potentially can be adopted for other broadband spectroscopic modalities.

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Section: ) Maximal Overlap Discrete Wavelet Transformmentioning

confidence: 98%

Section: Reverse Circular Advancementmentioning

confidence: 99%

Section: ) Maximal Overlap Discrete Wavelet Transformmentioning

confidence: 99%

Section: ) Maximal Overlap Discrete Wavelet Transformmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Chemical Identification in the Specular and Off-Specular Rough-Surface Scattered Terahertz Spectra Using Wavelet Shrinkage

Khani

Arbab

2021

IEEE Access

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In Vivo Assessment and Monitoring of Burn Wounds Using a Handheld Terahertz Hyperspectral Scanner

Osman

Harris

Zhou

et al. 2022

Advanced Photonics Research

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The accuracy of clinical assessment techniques in diagnosing partial‐thickness burn injuries has remained as low as 50–76%. Depending on the burn depth and environmental factors in the wound, such as reactive oxygen species, inflammation, and autophagy, partial‐thickness burns can heal spontaneously or require surgical intervention. Herein, it is demonstrated that terahertz time‐domain spectral imaging (THz‐TDSI) is a promising tool for in vivo quantitative assessment and monitoring of partial‐thickness burn injuries in large animals. We used a novel handheld THz‐TDSI scanner to characterize burn injuries in a porcine scald model with histopathological controls. Statistical analysis (n = 40) indicates that the THz‐TDSI modality can accurately differentiate between partial‐thickness and full‐thickness burn injuries (1‐way ANOVA, p < 0.05). THz‐TDSI has the potential to improve burn care outcomes by helping surgeons in making objective decisions for early excision of the wound.

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Two effective methods for improving the quality of THz spectroscopy systems

Mirsalehi

Kavehvash

Fardmanesh

2022

Optik

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Phase Function Effects on Identification of Terahertz Spectral Signatures Using the Discrete Wavelet Transform

Cited by 30 publications

References 25 publications

Chemical Identification in the Specular and Off-Specular Rough-Surface Scattered Terahertz Spectra Using Wavelet Shrinkage

Chemical Identification in the Specular and Off-Specular Rough-Surface Scattered Terahertz Spectra Using Wavelet Shrinkage

In Vivo Assessment and Monitoring of Burn Wounds Using a Handheld Terahertz Hyperspectral Scanner

Two effective methods for improving the quality of THz spectroscopy systems

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