Investigation on reconstruction methods applied to 3D terahertz computed tomography

Abstract

3D terahertz computed tomography has been performed using a monochromatic millimeter wave imaging system coupled with an infrared temperature sensor. Three different reconstruction methods (standard back-projection algorithm and two iterative analysis) have been compared in order to reconstruct large size 3D objects. The quality (intensity, contrast and geometric preservation) of reconstructed cross-sectional images has been discussed together with the optimization of the number of projections. Final demonstration to real-life 3D objects has been processed to illustrate the potential of the reconstruction methods for applied terahertz tomography.

Terahertz tomographic imaging of XVIIIth Dynasty Egyptian sealed pottery

“…However, in x-ray CT, it is well-known that BFP suffers from several disadvantages, such as beam hardening, noise sensitivity, and geometric degradation in case of an insufficient number of projections. We recently pointed out that alternative iterative reconstruction methods, such as the simultaneous algebraic reconstruction technique (SART) [17], can be applied to THz CT with equivalent accuracy and quality as BFP [8]. Especially for a limited number of projections (typically less than 25), we emphasized a quantitative degradation of the BFP reconstruction, whereas the SART method can already offer optimized reconstruction quality.…”

“…Recently, we developed an alternative THz imaging system based on a millimeter continuous-wave source coupled with an infrared thermal sensor. This device has especially been used for three-dimensional (3D) THz imaging of opaque objects using computed tomography (CT) [8], which was first demonstrated in 2002 [9].…”

Terahertz technologies: present and future

“…Both pulsed and CW THz waves can be applied to tomographic imaging of layer structure of tablets, internal structures of objects, material inspection, security applications, etc. [42,43,44,45,46,47,48] In addition to the above limited examples, a wide range of nondestructive inspection and testing applications have been reported in order to find real and specific needs which cannot be duplicated by competing technologies.…”

Terahertz and Cultural Heritage Science: Examination of Art and Archaeology

“…THz-CT uses mostly narrow bandwidth sources, multiple projection angles and back projection [62,63]. It is also possible to use broadband sources in time domain mode and to represent in the XY-plane for each pixel the time series (as depth Z) [64].…”