Cohesive framework for non-line-of-sight imaging based on Dirac notation.

The non-line-of-sight (NLOS) imaging field encompasses both experimental and computational frameworks that focus on imaging elements that are out of the direct line-of-sight, for example, imaging elements that are around a corner. Current NLOS imaging methods offer a compromise between accuracy and reconstruction time as experimental setups have become more reliable, faster, and more accurate. However, all these imaging methods implement different assumptions and light transport models that are only valid under particular circumstances.

Non-line-of-sight imaging in the presence of scattering media using phasor fields.

Non-line-of-sight (NLOS) imaging aims to reconstruct partially or completely occluded scenes. Recent approaches have demonstrated high-quality reconstructions of complex scenes with arbitrary reflectance, occlusions, and significant multi-path effects. However, previous works focused on surface scattering only, which reduces the generality in more challenging scenarios such as scenes submerged in scattering media.

Towards standardisation of contact and contactless electrical measurements of CVD graphene at the macro-, micro- and nano-scale.

Graphene has become the focus of extensive research efforts and it can now be produced in wafer-scale. For the development of next generation graphene-based electronic components, electrical characterization of graphene is imperative and requires the measurement of work function, sheet resistance, carrier concentration and mobility in both macro-, micro- and nano-scale. Moreover, commercial applications of graphene require fast and large-area mapping of electrical properties, rather than obtaining a single point value, which should be ideally achieved by a contactless measurement technique.

Mapping the conductivity of graphene with Electrical Resistance Tomography.

Electronic applications of large-area graphene films require rapid and accurate methods to map their electrical properties. Here we present the first electrical resistance tomography (ERT) measurements on large-area graphene samples, obtained with a dedicated measurement setup and reconstruction software. The outcome of an ERT measurement is a map of the graphene electrical conductivity.

Quality assessment of terahertz time-domain spectroscopy transmission and reflection modes for graphene conductivity mapping.

We present a comparative study of electrical measurements of graphene using terahertz time-domain spectroscopy in transmission and reflection mode, and compare the measured sheet conductivity values to electrical van der Pauw measurements made independently in three different laboratories. Overall median conductivity variations of up to 15% were observed between laboratories, which are attributed mainly to the well-known temperature and humidity dependence of non-encapsulated graphene devices. We conclude that terahertz time-domain spectroscopy performed in either reflection mode or transmission modes are indeed very accurate methods for mapping electrical conductivity of graphene, and that both methods are interchangeable within measurement uncertainties.

Terahertz scattering and water absorption for porosimetry.

We use terahertz transmission through limestone sedimentary rock samples to assess the macro and micro porosity. We exploit the notable water absorption in the terahertz spectrum to interact with the pores that are two orders of magnitude smaller (<1μm) than the terahertz wavelength. Terahertz water sensitivity provides us with the dehydration profile of the rock samples.

Terahertz time-gated spectral imaging for content extraction through layered structures.

Spatial resolution, spectral contrast and occlusion are three major bottlenecks for non-invasive inspection of complex samples with current imaging technologies. We exploit the sub-picosecond time resolution along with spectral resolution provided by terahertz time-domain spectroscopy to computationally extract occluding content from layers whose thicknesses are wavelength comparable. The method uses the statistics of the reflected terahertz electric field at subwavelength gaps to lock into each layer position and then uses a time-gated spectral kurtosis to tune to highest spectral contrast of the content on that specific layer.

Direct estimation of the permeation of topical excipients through artificial membranes and human skin with non-invasive Terahertz time-domain techniques.

Background: Drug permeation through skin, or a synthetic membrane, from locally acting pharmaceutical products can be influenced by the permeation behaviour of pharmaceutical excipients.

Objective: Terahertz time-domain technology is investigated as a non-invasive method for a direct and accurate measurement of excipients permeation through synthetic membranes or human skin.

Methods: A series of in-vitro release and skin permeation experiments of liquid excipients (e.

Nanostructured porous silicon films for terahertz optics.

A simple technique is reported to create 31 and 45 μm thick, graded-index Si films in the form of nanospirals on a Si substrate using a dynamic, oblique angle deposition technique. We show that the success in producing such a thick, nanostructured film without delamination from the Si substrate is primarily due to the nano-porous nature of the film which effectively eliminates the stress generated during growth. Effective refractive indices of 1.

Self-referenced method for terahertz wave time-domain spectroscopy.

The method allows retrieval of the absorbance of a sample without the need for a reference measurement. The method measures the dynamic variation of frequency resolution as the waveform is being acquired. In terahertz wave time-domain spectroscopy, the frequency resolution increases as the temporal window increases.

Assessment of terahertz spectroscopy to detect antibiotic residues in food and feed matrices.

We report the use of terahertz (THz) spectroscopy to explore the spectral properties of eleven antibiotics commonly used in livestock production. Eight of the eleven antibiotics showed specific fingerprints in the frequency range between 0.1 and 2 THz.

Identification and classification of chemicals using terahertz reflective spectroscopic focal-plane imaging system.

We present terahertz (THz) reflective spectroscopic focal-plane imaging of four explosive and bio-chemical materials (2, 4-DNT, Theophylline, RDX and Glutamic Acid) at a standoff imaging distance of 0.4 m. The 2 dimension (2-D) nature of this technique enables a fast acquisition time and is very close to a camera-like operation, compared to the most commonly used point emission-detection and raster scanning configuration.