Joint Deblurring and Denoising of THz Time-Domain Images

Ljubenovic, Marina; Zhuang, Lina; Beenhouwer, Jan De; Sijbers, Jan

doi:10.1109/access.2020.3045605

Cited by 12 publications

(22 citation statements)

References 33 publications

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“…A major reason for such unresolved problems may be the fact that THz beam can neither be easily collimated nor radiated widely as microwave radiation. Combined with the improvements of the theoretical analyzation of THz propagation and optical component design, the combination of signal analysis and processing techniques can be another solution [94] to such problems. Furthermore, as stated in the previous section, the use of a THz array, in combination with other novel techniques, such as the sparse array concept [95], or combining arrays with a mechanical beam-scanning system for higher data acquisition speed with lower cost, can also be a future trend for solving spatial sampling issues.…”

Section: Discussionmentioning

confidence: 99%

Towards Practical Terahertz Imaging System With Compact Continuous Wave Transceiver

Nishida

Sagisaka

et al. 2021

J. Lightwave Technol.

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Terahertz (THz) imaging techniques have attracted significant attention and have developed rapidly in recent years. However, despite several advances, these techniques are still not mature, and their high cost and system complexity continue to limit their applications. In this article, the techniques for achieving a practical imaging system with a compact THz transceiver are addressed, while considering the limitations of the current technique. The aim is to provide a brief review of related topics, while also covering our recent progress, which can provide some general perspectives and contrasting approaches for realizing a practical THz imaging system. The continuous wave devices are mainly focused for their flexibility of balancing the imaging resolution and data acquisition time. The importance of transceiver integration is also discussed and illustrated by introducing a 600-GHz band micro-photonic interface for integrating a THz source and detector, with a single resonant tunneling diode as a transceiver. With regard to system issues, spatial sampling with mechanical beam-scanning is discussed as an intermediate approach for moving stage and array technology. The potential and limitations of this approach are evaluated, along with an elliptical reflector as an alternative to an f-theta lens owing to its low cost and simplicity. The combination of integrated devices, along with the mechanical beam-scanning, is also discussed for demonstrating our current concept of realizing a practical THz imaging system.

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Section: Discussionmentioning

confidence: 99%

Towards Practical Terahertz Imaging System With Compact Continuous Wave Transceiver

Nishida

Sagisaka

et al. 2021

J. Lightwave Technol.

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“…An approach that considers bands of THz HS images jointly has been introduced in [7]. Similar to FastHyDe, the method is based on the low-rank and self-similarity properties of HS images and it includes two additional expansions that make it suitable for THz data: i) a specialized THz beam modelling process and ii) a deblurring step based on well-known, robust deblurring approaches.…”

Section: Image Processing Methods For Thz Datamentioning

confidence: 99%

“…The fast deblurring and denoising method [7], tailored to THz time-domain images, three noise types (Gaussian i.i.d., Gaussian non-i.i.d., and Poisson), and band-dependent blur is further tested on 1 cent and a silver pendant. The method follows the same low-rank assumption from (6) but instead of performing only denoising on subspace components (i.e., eigen-images) it additionally adds a non-blind deblurring step (i.e., deblurring with a known PSF).…”

Section: Joint Denoising and Deblurring Algorithmmentioning

confidence: 99%

“…Terahertz Time-Domain Spectroscopy (THz-TDS) employs short pulses of THz radiation to probe dielectric response of materials in the far-infrared region and reconstruct objects' inner structure, giving as result a 3-dimensional hyperspectral (HS) data-cube, providing information on both surface and inner structures. Despite the fact that THz-TDS imaging offers a unique means to probe materials' properties, it poses also major challenges in terms of data processing because of the multiple sources of image degradation that make difficult the analysis of the THz signals [7]. THz-TDS images are in fact corrupted by frequency-dependent beam-shape induced blur and noise with additional signal distortions introduced by scattering losses (more information on degradation effects will be provided in Section IV).…”

mentioning

confidence: 99%

“…Some conventional image restoration algorithms can singularly tackle blur effects, noise, or low resolution, thus overcoming only partially physical limitations determined by the THz-TDS imaging technique. The joint removal of several degradation effects in THz HS images represents still a challenge due to several reasons: a frequency dependency of blur and noise; the presence of blocking artefacts introduced by the step size of a scanning system; and existence of additional effects such as reflection and refraction [7]. At present, there is a limited number of efficient computational strategies to address some of the THz imaging problems and the majority of the proposed approaches have dealt with single-frequency measurements, such as THz images in continuous wave mode or volumetric reconstruction with THz computed tomography.…”

mentioning

confidence: 99%

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Beam-Shape Effects and Noise Removal from THz Time-Domain Images in Reflection Geometry in the 0.25-6 THz Range

Ljubenovic¹,

Artesani²,

Bonetti³

et al. 2022

Preprint

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The increasing need of restoring high-resolution Hyper-Spectral (HS) images is determining a growing reliance on Computer Vision-based processing to enhance the clarity of the image content. HS images can, in fact, suffer from degradation effects or artifacts caused by instrument limitations. This paper focuses on a procedure aimed at reducing the degradation effects, frequency-dependent blur and noise, in Terahertz Time-Domain Spectroscopy (THz-TDS) images in reflection geometry. It describes the application of a joint deblurring and denoising approach that had been previously proved to be effective for the restoration of THz-TDS images in transmission geometry, but that had never been tested in reflection modality. This mode is often the only one that can be effectively used in most cases, for example when analyzing objects that are either opaque in the THz range, or that cannot be displaced from their location (e.g., museums), such as those of cultural interest. Compared to transmission mode, reflection geometry introduces, however, further distortion to THz data, neglected in existing literature. In this work, we successfully implement image deblurring and denoising of both uniform-shape samples (a contemporary 1 Euro cent coin and an inlaid pendant) and samples with the uneven reliefs and corrosion products on the surface which make the analysis of the object particularly complex (an ancient Roman silver coin). The study demonstrates the ability of image processing to restore data in the 0.25 -6 THz range, spanning over more than four octaves, and providing the foundation for future analytical approaches of cultural heritage using the farinfrared spectrum still not sufficiently investigated in literature.

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HINRDNet: A half instance normalization residual dense network for passive millimetre wave image restoration

Huang

Hua

et al. 2023

Infrared Physics & Technology

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Joint Deblurring and Denoising of THz Time-Domain Images

Cited by 12 publications

References 33 publications

Towards Practical Terahertz Imaging System With Compact Continuous Wave Transceiver

Towards Practical Terahertz Imaging System With Compact Continuous Wave Transceiver

Beam-Shape Effects and Noise Removal from THz Time-Domain Images in Reflection Geometry in the 0.25-6 THz Range

HINRDNet: A half instance normalization residual dense network for passive millimetre wave image restoration

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