Refraction losses in terahertz computed tomography

Terahertz tomographic imaging of XVIIIth Dynasty Egyptian sealed pottery

“…Although THz CT seems powerful, most of the published results concerned the investigation of simple manufactured phantom objects, such as foam or polyethylene cylinders, drilled with metallic bars [10,11] or filled with specific chemical substances such as lactose or lactose powder [12,13]. The main reason is the limitation caused by the diffraction effects and Fresnel losses experienced by the propagation of the THz wave through the sample.…”

Consideration of refraction losses for time-domain terahertz computed tomography

“…However, due to important refraction losses, the time delay of the THz main pulse did not correspond properly to the effective optical pathway experienced by the THz radiation near the edges of the sample. To solve this problem, we applied a specific multi-averaging procedure as follows [3]. First, we fixed minimal thresholds to identify the presence of peaks in a single THz waveform.…”

Hyperspectral Terahertz Tomography in Amplitude Contrast

“…CW narrowband systems will allow imaging in THz amplitude contrast at discrete wavelengths important for security and non-destructive testing. To achieve indirect imaging from the amplitude of the transmission beam hard-field tomography, it is also essential to understand and manage the soft-field scattered component in the transmitted THz signal; problems associated with THz computed tomography include Snell and Fresnel refraction [12][13][14][15], and Gaussian THz beam profile [16]. The novelty in this work is that using a pulsed THz tomography system wide spectral information is accessed, over one order of magnitude in wavelength, to study the quality of the hard-field reconstructed images as a function of wavelength.…”