Elimination of Fresnel Reflection Boundary Effects and Beam Steering in Pulsed Terahertz Computed Tomography

Mukherjee, S.; Federici, John F.; Lopes, Paulo; Cabral, Miguel

doi:10.1007/s10762-013-9985-3

Cited by 25 publications

(20 citation statements)

References 20 publications

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“…For example, Mukherjee et al [13] consider reconstructing a homogeneous cylinder with a known shape and material. They use this prior knowledge to compensate for the reflection and refraction in the acquired projections.…”

Section: Review On Thz Tomographymentioning

confidence: 99%

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Terahertz Differential Computed Tomography: a Relevant Nondestructive Inspection Application

Duhant

Triki²,

Strauss

2019

J Infrared Milli Terahz Waves

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In recent years, tremendous advances have been made in the choice of materials used in industry. With weight reduction as the goal, composite and polymer materials are more and more popular but they are almost transparent to X-ray. Because of this, interest has grown in other wavelengths like TeraHertz (THz). Due to a difference in how X-ray and THz propagate, X-ray CT algorithms cannot be directly used. For example, THz induces refraction making the reconstruction problem nonlinear. In this paper, we present a new algorithm which complies with beam profile intensities, refraction, reflection. It is based on linearizing the reconstruction process around a Computer Aided Design (CAD) model of the object to be reconstructed. The method we propose computes the deviation between the object and this model.

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Section: Review On Thz Tomographymentioning

confidence: 99%

“…Therefore, the relation between the beam attenuation and the densities to be reconstructed cannot be represented by a linear relation anymore. This should prohibits the direct use of conventional reconstruction algorithms [13].…”

Section: Introductionmentioning

confidence: 99%

Terahertz Differential Computed Tomography: a Relevant Nondestructive Inspection Application

Duhant

Triki²,

Strauss

2019

J Infrared Milli Terahz Waves

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“…We follow the idea of Mukherjee et. al, see [23], who consider refraction and reflection losses for cylindrical objects with known refractive index for the reconstruction of the absorption coefficient. We generalize this approach for general objects with given interfaces, unknown n and reconstruct both refractive index and absorption coefficient.…”

Section: Refraction and Reflection Lossesmentioning

confidence: 99%

“…Therefore, our approach will be a correction of the measured intensity data, so that only absorption losses are considered for the reconstruction of the absorption coefficient. Mukherjee et al [23] introduced this approach successfully for cylindric objects. We expand this approach to arbitrary interfaces and an initially unknown refractive index.…”

Section: Consideration Of Fresnel Lossesmentioning

confidence: 99%

“…In [29], Recur et al presented a filtered backprojection and adapted iterative methods (SART, OSEM) for 3D THz CT, which considers the intensity distribution of THz rays (Gaussian beam). Mukherjee et al only regard cylindric objects, but take Fresnel reflection losses and beam steering losses into account, see [23]. Furthermore, Ferguson et al [15] and Wang et al [34] reconstruct the refractive index using measurements of the diffracted THz field based on the Helmholtz equation (so-called T-ray Diffraction Tomography, analogous to ultrasound tomography, see [9,10]).…”

Section: Introductionmentioning

confidence: 99%

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A modified algebraic reconstruction technique taking refraction into account with an application in terahertz tomography

Tepe

Schuster

Littau

2016

Inverse Problems in Science and Engineering

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Terahertz (THz) tomography is a rather novel technique for nondestructive testing that is particularly suited for the testing of plastics and ceramics. Previous publications showed a large variety of conventional algorithms adapted from computed tomography or ultrasound tomography which were directly applied to THz tomography. Conventional algorithms neglect the specific nature of THz radiation, i. e. refraction at interfaces, reflection losses and the beam profile (Gaussian beam), which results in poor reconstructions. The aim is the efficient reconstruction of the complex refractive index, since it indicates inhomogeneities in the material. A hybrid algorithm has been developed based on the algebraic reconstruction technique (ART). ART is adapted by including refraction (Snell's law) and reflection losses (Fresnel equations). Our method uses a priori information about the interface and layer geometry of the sample. This results in the "Modified ART for THz tomography", which reconstructs simultaneously the complex refractive index from transmission coefficient and travel time measurements.

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Equivalent source of reflector in finite‐different time‐domain for rapid analysis of corner scattering in terahertz computed tomography imaging

Feng,

Cha,

Shi

et al. 2024

Micro & Optical Tech Letters

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We propose the equivalent source of reflector in finite‐different time‐domain (ESR‐FDTD) for rapid analysis of corner scattering in terahertz computed tomography (THz‐CT) imaging. The ESR‐FDTD is used instead of the reflector in the THz‐CT imaging system, which can significantly reduce the computational domain of the THz‐CT imaging system and effectively reduce the computational time and memory usage. The electric field distribution of the beam reflected by the reflector and that of the beam radiated from the ESR of the reflector are compared, and the results show that the electric field distributions of the reflector and its ESR are almost the same. The results of the corner scattering show that the phenomenon of corner scattering does not fully satisfy the behaviors of reflection and refraction. Therefore, the corner scattering cannot be accurately analyzed by the ray‐tracing method.

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Elimination of Fresnel Reflection Boundary Effects and Beam Steering in Pulsed Terahertz Computed Tomography

Cited by 25 publications

References 20 publications

Terahertz Differential Computed Tomography: a Relevant Nondestructive Inspection Application

Terahertz Differential Computed Tomography: a Relevant Nondestructive Inspection Application

A modified algebraic reconstruction technique taking refraction into account with an application in terahertz tomography

Equivalent source of reflector in finite‐different time‐domain for rapid analysis of corner scattering in terahertz computed tomography imaging

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