Terahertz frequency modulated continuous wave imaging advanced data processing for art painting analysis

Abstract

Reflection terahertz frequency modulated continuous waves scanner (300 GHz) has been proficiently optimized for imaging two easel paintings of different age. The information content of the obtained THz images has been fully inspected by selecting the appropriate THz image parameter. At the same time, a new data processing has been developed for improving the level of detail held by the axial parametric THz images by means of Gaussian fit of the reflected signals. By carefully weighting the reflected signals as a function of the optical path, the reflected amplitude has been corrected for the positioning of the object surface with respect to the beam focal point. The artifact affecting the THz images recorded from an uneven painting surface have been resolved and the obtained images fairly represent to the original painting.

Roadmap of Terahertz Imaging 2021

“…With regard to the inspection of materials and objects, FMCW techniques at the interface between the microwave and THz frequency regimes have established themselves by now [377][378][379][380], and the measurement systems continue to be improved [381][382][383][384][385].…”

Review of photomixing continuous-wave terahertz systems and current application trends in terahertz domain

“…Recently artwork started to be scanned by THz systems. 57 These imaging systems have been used for scanning ancient mummified samples paintings. 74,75 Frequency-domain THz systems allow for the depth inspection of the object under investigation due to the frequency sweep of the emitted radiation.…”

“…74 Figure 12(a) shows the THz image of the global maximum of the signals recorded from the contemporary painting after contrast enhancement. 57 By comparing it with the THz surface topography of the painting obtained by illuminating the object with raking light Fig. 12(a), it can be seen that the black lines of the THz image correspond to the sharp edges of the thickest brushstrokes used by the artist to model the subjects in relief.…”

“…a) The contemporary painting front, (b) THz image of the contemporary painting after contrast enhancement, parameter: signal global maximum, (c) signals recorded at the ðx; yÞ coordinates reported in the legend, corresponding to the colored dots ofFig. 12(b) 57. …”

Fibonacci terahertz imaging by silicon diffractive optics

“…Terahertz (THz) imaging and spectroscopy displays an attractive feature to expose new possibilities and wide-ranging potential in many versatile applications. Already known implementations covering security [1,2], package inspection [3], biomedicine diagnostics [4,5] and food control [6] recently have been extended by promising studies in investigating 2D materials [7,8], surface control [9] and paintings examination [10,11]. From practical point of view, design of a THz imaging system should be compact, free of optical alignment, reliable and providing an ability of relatively rapid scans.…”