In mausoleum murals, existing bubbles are one kind of the most harmful defects for the repair and protection of relics. For this reason, it is necessary to detect bubbles, especially the ones with small size. A method...In mausoleum murals, existing bubbles are one kind of the most harmful defects for the repair and protection of relics. For this reason, it is necessary to detect bubbles, especially the ones with small size. A method to detect the small bubbles with enhanced terahertz （THz） images is proposed. To simulate the bubbles in the mausoleum murals, circular grooves have been hidden in the plaster and then measured by the THz reflected time domain spectroscopy imaging system. To observe the small bubbles in murals, a comprehensive enhancement algorithm is adopted to process the obtained THz images. With the enhanced method, the circular grooves in the murals can be observed clearly, even for the circular groove with a diameter of 1.5 mm. The results indicate that the proposed comprehensive method can be used to detect the tiny defects of murals.展开更多
Terahertz(THz)near-field microscopy retains the advantages of THz radiation and realizes sub-wavelength imaging,which enables applications in fundamental research and industrial fields.In most THz near-field microscop...Terahertz(THz)near-field microscopy retains the advantages of THz radiation and realizes sub-wavelength imaging,which enables applications in fundamental research and industrial fields.In most THz near-field microscopies,the sample surface must be approached by a THz detector or source,which restricts the sample choice.Here,a technique was developed based on an air-plasma dynamic aperture,where two mutually perpendicular air-plasmas overlapped to form a cross-filament above a sample surface that modulated an incident THz beam.THz imaging with quasi sub-wavelength resolution(approximately λ/2,where λ is the wavelength of the THz beam)was thus observed without approaching the sample with any devices.Damage to the sample by the air-plasmas was avoided.Near-field imaging of four different materials was achieved,including metallic,semiconductor,plastic,and greasy samples.The resolution characteristics of the near-field system were investigated with experiment and theory.The advantages of the technique are expected to accelerate the advancement of THz microscopy.展开更多
基金supported by the 973 Program of China under Grant No.2013CBA01702National Natural Science Foundation of China under Grant No.11474206,No.91233202,No.11374216,and No.11404224+3 种基金Program for New Century Excellent Talents in University under Grant No.NCET-12-0607Scientific Research Project of Beijing Education Commission under Grant No.KM201310028005Specialized Research Fund for the Doctoral Program of Higher Education under Grant No.20121108120009the Beijing Youth Top-Notch Talent Training Plan under Grant No.CIT&TCD201504080
文摘In mausoleum murals, existing bubbles are one kind of the most harmful defects for the repair and protection of relics. For this reason, it is necessary to detect bubbles, especially the ones with small size. A method to detect the small bubbles with enhanced terahertz （THz） images is proposed. To simulate the bubbles in the mausoleum murals, circular grooves have been hidden in the plaster and then measured by the THz reflected time domain spectroscopy imaging system. To observe the small bubbles in murals, a comprehensive enhancement algorithm is adopted to process the obtained THz images. With the enhanced method, the circular grooves in the murals can be observed clearly, even for the circular groove with a diameter of 1.5 mm. The results indicate that the proposed comprehensive method can be used to detect the tiny defects of murals.
基金This work was supported by the National Natural Science Foundation of China(grant nos.11874132,1174243,11774246,and 12174271)the National Key R&D Program of China(No.2019YFC1711905)+2 种基金the Beijing Talents Project(grant no.2018A19)the Sino-German Mobility Program from Sino-German Center for Science Funding(Grant M-0225)DAAD/CSC Exchange Project,and Capacity Building for Science&Technology Innovation-Fundamental Scientifc Research Funds(grand no.00820531120017,00820530290072).
文摘Terahertz(THz)near-field microscopy retains the advantages of THz radiation and realizes sub-wavelength imaging,which enables applications in fundamental research and industrial fields.In most THz near-field microscopies,the sample surface must be approached by a THz detector or source,which restricts the sample choice.Here,a technique was developed based on an air-plasma dynamic aperture,where two mutually perpendicular air-plasmas overlapped to form a cross-filament above a sample surface that modulated an incident THz beam.THz imaging with quasi sub-wavelength resolution(approximately λ/2,where λ is the wavelength of the THz beam)was thus observed without approaching the sample with any devices.Damage to the sample by the air-plasmas was avoided.Near-field imaging of four different materials was achieved,including metallic,semiconductor,plastic,and greasy samples.The resolution characteristics of the near-field system were investigated with experiment and theory.The advantages of the technique are expected to accelerate the advancement of THz microscopy.
