In order to improve the imaging quality of terahertz(THz) spectroscopy, Terahertz Composite Imaging Method(TCIM) is proposed. The traditional methods of improving THz spectroscopy image quality are mainly from the asp...In order to improve the imaging quality of terahertz(THz) spectroscopy, Terahertz Composite Imaging Method(TCIM) is proposed. The traditional methods of improving THz spectroscopy image quality are mainly from the aspects of de-noising and image enhancement. TCIM breaks through this limitation. A set of images, reconstructed in a single data collection, can be utilized to construct two kinds of composite images. One algorithm, called Function Superposition Imaging Algorithm(FSIA), is to construct a new gray image utilizing multiple gray images through a certain function. The features of the Region Of Interest(ROI) are more obvious after operating, and it has capability of merging ROIs in multiple images. The other, called Multi-characteristics Pseudo-color Imaging Algorithm(Mc Pc IA), is to construct a pseudo-color image by combining multiple reconstructed gray images in a single data collection. The features of ROI are enhanced by color differences. Two algorithms can not only improve the contrast of ROIs, but also increase the amount of information resulting in analysis convenience. The experimental results show that TCIM is a simple and effective tool for THz spectroscopy image analysis.展开更多
This paper is devoted to reviewing the results achieved so far in the application of the single-pixel imaging technique to terahertz(THz)systems.The use of THz radiation for imaging purposes has been largely explored ...This paper is devoted to reviewing the results achieved so far in the application of the single-pixel imaging technique to terahertz(THz)systems.The use of THz radiation for imaging purposes has been largely explored in the last twenty years,due to the unique capabilities of this kind of radiation in interrogating material properties.However,THz imaging systems are still limited by the long acquisition time required to reconstruct the object image and significant efforts have been recently directed to overcome this drawback.One of the most promising approaches in this sense is the so-called“single-pixel”imaging,which in general enables image reconstruction by patterning the beam probing the object and measuring the total transmission(or reflection)with a single-pixel detector(i.e.,with no spatial resolution).The main advantages of such technique are that i)no bulky moving parts are required to raster-scan the object and ii)compressed sensing(CS)algorithms,which allow an appropriate reconstruction of the image with an incomplete set of measurements,can be successfully implemented.Overall,this can result in a reduction of the acquisition time.In this review,we cover the experimental solutions proposed to implement such imaging technique at THz frequencies,as well as some practical uses for typical THz applications.展开更多
Computed tomography has been proven to be useful for non-destructive inspection of structures and materials. We build a three-dimensional imaging system with the photonically generated incoherent noise source and the ...Computed tomography has been proven to be useful for non-destructive inspection of structures and materials. We build a three-dimensional imaging system with the photonically generated incoherent noise source and the Schottky barrier diode detector in the terahertz frequency band （90–140GHz）. Based on the computed tomography technique, the three-dimensional image of a ceramic sample is reconstructed successfully by stacking the slices at different heights. The imaging results not only indicate the ability of terahertz wave in the non-invasive sensing and non-destructive inspection applications, but also prove the effectiveness and superiority of the uni-traveling-carrier photodiode as a terahertz source in the imaging applications.展开更多
Terahertz(THz)imaging has drawn significant attention because THz wave has a unique capability to transient,ultrawide spectrum and low photon energy.However,the low resolution has always been a problem due to its long...Terahertz(THz)imaging has drawn significant attention because THz wave has a unique capability to transient,ultrawide spectrum and low photon energy.However,the low resolution has always been a problem due to its long wavelength,limiting their application of fields practical use.In this paper,we proposed a complex one-shot super-resolution(COSSR)framework based on a complex convolution neural network to restore superior THz images at 0.35 times wavelength by extracting features directly from a reference measured sample and groundtruth without the measured PSF.Compared with real convolution neural network-based approaches and complex zero-shot super-resolution(CZSSR),COSSR delivers at least 6.67,0.003,and 6.96%superior higher imaging efficacy in terms of peak signal to noise ratio(PSNR),mean square error(MSE),and structural similarity index measure(SSIM),respectively,for the analyzed data.Additionally,the proposed method is experimentally demonstrated to have a good generalization and to perform well on measured data.The COSSR provides a new pathway for THz imaging super-resolution(SR)reconstruction below the diffraction limit.展开更多
Spectroscopic measurements and terahertz imaging of the cornea are carried out by using a rapid scanning terahertz time domain spectroscopy（THz-TDS） system.A voice coil motor stage based optical delay line（VCM-ODL...Spectroscopic measurements and terahertz imaging of the cornea are carried out by using a rapid scanning terahertz time domain spectroscopy（THz-TDS） system.A voice coil motor stage based optical delay line（VCM-ODL） is developed to provide a rather simple and robust structure with both the high scanning speed and the large delay length.The developed system is used for THz spectroscopic measurements and imaging of the corneal tissue with different amounts of water content,and the measurement results show the consistence with the reported results,in which the measurement time using VCM-ODL is a factor of 360 shorter than the traditional motorized optical delay line（MDL）.With reducing the water content a monotonic decrease of the complex permittivity of the cornea is observed.The two-term Debye relaxation model is employed to explain our experimental results,revealing that the fast relaxation time of a dehydrated cornea is much larger than that of a hydrated cornea and its dielectric behavior can be affected by the presence of the biological macromolecules.These results demonstrate that our THz spectrometer may be a promising candidate for tissue hydration sensing and practical application of THz technology.展开更多
A system for measuring terahertz spectrum is proposed based on optical interferometer theory, and is experimentally demonstrated by using a backward-wave oscillator as the terahertz source. A high-resolution, high-pre...A system for measuring terahertz spectrum is proposed based on optical interferometer theory, and is experimentally demonstrated by using a backward-wave oscillator as the terahertz source. A high-resolution, high-precision interferometer is constructed by using a pyroelectric detector and a chopper. The results show that the spectral resolution is better than 1 GHz and the relative error of frequency is less than 3%. The terahertz energy density distribution is calculated by an inverse Fourier transform and tested to verify the feasibility of the interferometric approach. Two kinds of carbon-fiber composites are imaged. The results confirm that the interferometer is useful for transmission imaging of materials with different thickness values.展开更多
A compact terahertz（THz） imaging system based on complementary compressive sensing has been proposed using two single-pixel detectors. By using a mechanical spatial light modulator, sampling in the transmission and ...A compact terahertz（THz） imaging system based on complementary compressive sensing has been proposed using two single-pixel detectors. By using a mechanical spatial light modulator, sampling in the transmission and reflection orientations was achieved simultaneously, which allows imaging with negative mask values. The improvement of THz image quality and anti-noise performance has been verified experimentally compared with the traditional reconstructed image, and is in good agreement with the numerical simulation. The demonstrated imaging system, with the advantages of high imaging quality and strong anti-noise property, opens up possibilities for new applications in the THz region.展开更多
In this article, two terahertz transmission imaging systems are built with a 2.52 THz continuous wave laser and two types of sensors. One is array scanning system using a 124×124 pyro-electric array camera as the...In this article, two terahertz transmission imaging systems are built with a 2.52 THz continuous wave laser and two types of sensors. One is array scanning system using a 124×124 pyro-electric array camera as the detector; the other is a point-wise scanning system utilizing a Golay cell as the detector. The imaging speed and quality is briefly analyzed. Terahertz （THz） imaging results demonstrate that the array scanning system has higher imaging speed with lower resolution. The point-wise scanning system has higher imaging quality with lower speed.展开更多
A review on Terahertz end-to-end systems with an emphasis on integrated approaches is presented.Four major catalogs of THz integrated systems,including THz communication systems,THz imaging systems,THz radars,and THz ...A review on Terahertz end-to-end systems with an emphasis on integrated approaches is presented.Four major catalogs of THz integrated systems,including THz communication systems,THz imaging systems,THz radars,and THz spectroscopy systems,are reviewed in this article.The performance of integrated systems is compared with non-integrated solutions,followed by a discussion on the trend in future research avenues and applications.展开更多
Graphene is a one-atom-thick planar sheet of sp2-hybridized orbital bonded honeycomb carbon crystal. Its gapless and linear energy spectra of electrons and holes lead to the unique carrier transport and optical proper...Graphene is a one-atom-thick planar sheet of sp2-hybridized orbital bonded honeycomb carbon crystal. Its gapless and linear energy spectra of electrons and holes lead to the unique carrier transport and optical properties, such as giant carrier mobility and broadband flat optical response. As a novel material, graphene has been regarded to be extremely suitable and competent for the development of terahertz （THz） optical devices. In this paper, the fundamental electronic and optic properties of graphene are described. Based on the energy band structure and light transmittance properties of graphene, many novel graphene based THz devices have been proposed, including modulator, generator, detector, and imaging device. This progress has been reviewed. Future research directions of the graphene devices for THz applications are also proposed.展开更多
As semiconductor devices,the terahertz quantum-cascade laser is a coherent source based on intersubband transitions of unipolar carriers while the terahertz quantum-well photodetector is a kind of detector which match...As semiconductor devices,the terahertz quantum-cascade laser is a coherent source based on intersubband transitions of unipolar carriers while the terahertz quantum-well photodetector is a kind of detector which matches the laser frequency.They are solid-state,electrically operated,and can be easily integrated with other components.This paper reviews the state of the art for the design,working performance,and future directions of the two devices.Their applications in photoelectric characterization and imaging are also discussed.展开更多
The analysis on the thickness of polyamide plate using Terahertz Time Domain System(THz-TDS)in reflection mode is carried out.The refractive index,one of the optical parameters in terahertz band,is solved through the ...The analysis on the thickness of polyamide plate using Terahertz Time Domain System(THz-TDS)in reflection mode is carried out.The refractive index,one of the optical parameters in terahertz band,is solved through the mathematics model,and its value is 1.88.A kind of polyamide plate sample with four kinds of thickness is designed and the ability of THz-based method to detect defects or foreign bodies in fiber glass is verified by attaching metal plates to the back of fiberglass.By the comparison of traditional method and THz method,the terahertz method has a measurement error between 2.5%and 10%.As the thickness increases,the error tends to increase.The reason about the deviations is analyzed,as well as the systematic factors affecting the thickness measurement accuracy,in order to improve the accuracy of THz thickness measurement system and provide theoretical basis for designing terahertz thickness measurement system in the future.展开更多
Recently,the diagnoses of dental caries and other dental issues are in a queue as only X-ray-based techniques are available in most hospitals around the world.Terahertz(THz)parametric imaging(TPI)is the latest technol...Recently,the diagnoses of dental caries and other dental issues are in a queue as only X-ray-based techniques are available in most hospitals around the world.Terahertz(THz)parametric imaging(TPI)is the latest technology that can be applied for medical applications,especially dental caries.This technology is harmless and thus suitable for biological samples owing to the low energy of THz emission.In this paper,a developed TPI system is used to investigate the two-dimensional(2 D)and three-dimensional(3D)images of different samples from human teeth.After analyzing the measured images of human teeth,the results suggest that the THz parametric technology is capable of investigating the inner side structure of the teeth.This technique can be useful in detecting the defects in all types of human and animal teeth.The measurement and analytical calculations have been performed by using the TPI system and MATLAB,respectively,and both are in good agreement.The characteristics of THz waves and their interactions with the tooth samples are summarized.And the available THz-based technologies,such as TPI,and their potential applications of diagnoses are also presented.展开更多
基金National defense technical basic research project,Terahertz Detection Technology and Application Research on Ceramic Matrix Composites(JSZL2015411C002).
文摘In order to improve the imaging quality of terahertz(THz) spectroscopy, Terahertz Composite Imaging Method(TCIM) is proposed. The traditional methods of improving THz spectroscopy image quality are mainly from the aspects of de-noising and image enhancement. TCIM breaks through this limitation. A set of images, reconstructed in a single data collection, can be utilized to construct two kinds of composite images. One algorithm, called Function Superposition Imaging Algorithm(FSIA), is to construct a new gray image utilizing multiple gray images through a certain function. The features of the Region Of Interest(ROI) are more obvious after operating, and it has capability of merging ROIs in multiple images. The other, called Multi-characteristics Pseudo-color Imaging Algorithm(Mc Pc IA), is to construct a pseudo-color image by combining multiple reconstructed gray images in a single data collection. The features of ROI are enhanced by color differences. Two algorithms can not only improve the contrast of ROIs, but also increase the amount of information resulting in analysis convenience. The experimental results show that TCIM is a simple and effective tool for THz spectroscopy image analysis.
文摘This paper is devoted to reviewing the results achieved so far in the application of the single-pixel imaging technique to terahertz(THz)systems.The use of THz radiation for imaging purposes has been largely explored in the last twenty years,due to the unique capabilities of this kind of radiation in interrogating material properties.However,THz imaging systems are still limited by the long acquisition time required to reconstruct the object image and significant efforts have been recently directed to overcome this drawback.One of the most promising approaches in this sense is the so-called“single-pixel”imaging,which in general enables image reconstruction by patterning the beam probing the object and measuring the total transmission(or reflection)with a single-pixel detector(i.e.,with no spatial resolution).The main advantages of such technique are that i)no bulky moving parts are required to raster-scan the object and ii)compressed sensing(CS)algorithms,which allow an appropriate reconstruction of the image with an incomplete set of measurements,can be successfully implemented.Overall,this can result in a reduction of the acquisition time.In this review,we cover the experimental solutions proposed to implement such imaging technique at THz frequencies,as well as some practical uses for typical THz applications.
基金Supported by the Hundred Talents Program of Chinese Academy of Sciencesthe National Basic Research Program of China under Grant No 2014CB339803+2 种基金the Major National Development Project of Scientific Instrument and Equipment under Grant No2011YQ150021the National Natural Science Foundation of China under Grant Nos 61575214,61574155,61404149 and 61404150the Shanghai Municipal Commission of Science and Technology under Grant Nos 14530711300,15560722000 and 15ZR1447500
文摘Computed tomography has been proven to be useful for non-destructive inspection of structures and materials. We build a three-dimensional imaging system with the photonically generated incoherent noise source and the Schottky barrier diode detector in the terahertz frequency band （90–140GHz）. Based on the computed tomography technique, the three-dimensional image of a ceramic sample is reconstructed successfully by stacking the slices at different heights. The imaging results not only indicate the ability of terahertz wave in the non-invasive sensing and non-destructive inspection applications, but also prove the effectiveness and superiority of the uni-traveling-carrier photodiode as a terahertz source in the imaging applications.
基金"XingLiaoYingCai"Talents of Liaoning Province,China(Grant No.XLYC2007074)Shenyang Young and Middle-aged Science and Technology Innovation Talent Support Program(Grant No.RC200512)+1 种基金Project supported by“XingLiaoYingCai"Talents of Liaoning Province,China(Grant No.XLYC2007074)Shenyang Young and Middle-aged Science and Technology Innovation Talent Support Program(Grant No.RC200512),。
文摘Terahertz(THz)imaging has drawn significant attention because THz wave has a unique capability to transient,ultrawide spectrum and low photon energy.However,the low resolution has always been a problem due to its long wavelength,limiting their application of fields practical use.In this paper,we proposed a complex one-shot super-resolution(COSSR)framework based on a complex convolution neural network to restore superior THz images at 0.35 times wavelength by extracting features directly from a reference measured sample and groundtruth without the measured PSF.Compared with real convolution neural network-based approaches and complex zero-shot super-resolution(CZSSR),COSSR delivers at least 6.67,0.003,and 6.96%superior higher imaging efficacy in terms of peak signal to noise ratio(PSNR),mean square error(MSE),and structural similarity index measure(SSIM),respectively,for the analyzed data.Additionally,the proposed method is experimentally demonstrated to have a good generalization and to perform well on measured data.The COSSR provides a new pathway for THz imaging super-resolution(SR)reconstruction below the diffraction limit.
基金Project supported by the National Natural Science Foundation of China(Grant No.61205101)the Shenzhen Municipal Research Foundation,China(Grant Nos.GJHZ201404171134305 and JCYJ20140417113130693)the Marie Curie Actions-International Research Staff Exchange Scheme(IRSES)(Grant No.FP7 PIRSES-2013-612267)
文摘Spectroscopic measurements and terahertz imaging of the cornea are carried out by using a rapid scanning terahertz time domain spectroscopy（THz-TDS） system.A voice coil motor stage based optical delay line（VCM-ODL） is developed to provide a rather simple and robust structure with both the high scanning speed and the large delay length.The developed system is used for THz spectroscopic measurements and imaging of the corneal tissue with different amounts of water content,and the measurement results show the consistence with the reported results,in which the measurement time using VCM-ODL is a factor of 360 shorter than the traditional motorized optical delay line（MDL）.With reducing the water content a monotonic decrease of the complex permittivity of the cornea is observed.The two-term Debye relaxation model is employed to explain our experimental results,revealing that the fast relaxation time of a dehydrated cornea is much larger than that of a hydrated cornea and its dielectric behavior can be affected by the presence of the biological macromolecules.These results demonstrate that our THz spectrometer may be a promising candidate for tissue hydration sensing and practical application of THz technology.
基金supported by the National Natural Science Foundation of China(Grant Nos.61377109 and 11374007)
文摘A system for measuring terahertz spectrum is proposed based on optical interferometer theory, and is experimentally demonstrated by using a backward-wave oscillator as the terahertz source. A high-resolution, high-precision interferometer is constructed by using a pyroelectric detector and a chopper. The results show that the spectral resolution is better than 1 GHz and the relative error of frequency is less than 3%. The terahertz energy density distribution is calculated by an inverse Fourier transform and tested to verify the feasibility of the interferometric approach. Two kinds of carbon-fiber composites are imaged. The results confirm that the interferometer is useful for transmission imaging of materials with different thickness values.
基金Project supported by the National Basic Research Program of China(Grant Nos.2015CB755403 and 2014CB339802)the National Key Research and Development Program of China(Grant No.2016YFC0101001)+3 种基金the National Natural Science Foundation of China(Grant Nos.61775160,61771332,and 61471257)China Postdoctoral Science Foundation(Grant No.2016M602954)Postdoctoral Science Foundation of Chongqing,China(Grant No.Xm2016021)the Joint Incubation Project of Southwest Hospital,China(Grant Nos.SWH2016LHJC04 and SWH2016LHJC01)
文摘A compact terahertz（THz） imaging system based on complementary compressive sensing has been proposed using two single-pixel detectors. By using a mechanical spatial light modulator, sampling in the transmission and reflection orientations was achieved simultaneously, which allows imaging with negative mask values. The improvement of THz image quality and anti-noise performance has been verified experimentally compared with the traditional reconstructed image, and is in good agreement with the numerical simulation. The demonstrated imaging system, with the advantages of high imaging quality and strong anti-noise property, opens up possibilities for new applications in the THz region.
文摘In this article, two terahertz transmission imaging systems are built with a 2.52 THz continuous wave laser and two types of sensors. One is array scanning system using a 124×124 pyro-electric array camera as the detector; the other is a point-wise scanning system utilizing a Golay cell as the detector. The imaging speed and quality is briefly analyzed. Terahertz （THz） imaging results demonstrate that the array scanning system has higher imaging speed with lower resolution. The point-wise scanning system has higher imaging quality with lower speed.
文摘A review on Terahertz end-to-end systems with an emphasis on integrated approaches is presented.Four major catalogs of THz integrated systems,including THz communication systems,THz imaging systems,THz radars,and THz spectroscopy systems,are reviewed in this article.The performance of integrated systems is compared with non-integrated solutions,followed by a discussion on the trend in future research avenues and applications.
基金supported by the 973 Program of China under Grant No.2013CBA01702the National Natural Science Foundation of China under Grant No.11204188,61205097,91233202,11374216,and 11174211+2 种基金the National High Technology Research and Development Program of China under Grant No.2012AA101608-6the Beijing Natural Science Foundation under Grant No.KZ201110028035the Program for New Century Excellent Talents in University under Grant No.NCET-12-0607,and the CAEP THz Science and Technology Foundation
文摘Graphene is a one-atom-thick planar sheet of sp2-hybridized orbital bonded honeycomb carbon crystal. Its gapless and linear energy spectra of electrons and holes lead to the unique carrier transport and optical properties, such as giant carrier mobility and broadband flat optical response. As a novel material, graphene has been regarded to be extremely suitable and competent for the development of terahertz （THz） optical devices. In this paper, the fundamental electronic and optic properties of graphene are described. Based on the energy band structure and light transmittance properties of graphene, many novel graphene based THz devices have been proposed, including modulator, generator, detector, and imaging device. This progress has been reviewed. Future research directions of the graphene devices for THz applications are also proposed.
基金the National Key R&D Program of China(Grant No.2017YFA0701005)the National Natural Science Foundation of China(Grant Nos.61927813,61775229,61704181,and 61991432)the Shanghai International Cooperation Project,China(Grant No.18590780100).
文摘As semiconductor devices,the terahertz quantum-cascade laser is a coherent source based on intersubband transitions of unipolar carriers while the terahertz quantum-well photodetector is a kind of detector which matches the laser frequency.They are solid-state,electrically operated,and can be easily integrated with other components.This paper reviews the state of the art for the design,working performance,and future directions of the two devices.Their applications in photoelectric characterization and imaging are also discussed.
文摘The analysis on the thickness of polyamide plate using Terahertz Time Domain System(THz-TDS)in reflection mode is carried out.The refractive index,one of the optical parameters in terahertz band,is solved through the mathematics model,and its value is 1.88.A kind of polyamide plate sample with four kinds of thickness is designed and the ability of THz-based method to detect defects or foreign bodies in fiber glass is verified by attaching metal plates to the back of fiberglass.By the comparison of traditional method and THz method,the terahertz method has a measurement error between 2.5%and 10%.As the thickness increases,the error tends to increase.The reason about the deviations is analyzed,as well as the systematic factors affecting the thickness measurement accuracy,in order to improve the accuracy of THz thickness measurement system and provide theoretical basis for designing terahertz thickness measurement system in the future.
基金the Research Fund for International Young Scientist Fund under Grant No.61750110520the Special Project for Guiding Local Science and Technology Development under Grant No.2018ZYYD006the Hubei Polytechnic University Laboratory Fund under Grant No.19XJK24R。
文摘Recently,the diagnoses of dental caries and other dental issues are in a queue as only X-ray-based techniques are available in most hospitals around the world.Terahertz(THz)parametric imaging(TPI)is the latest technology that can be applied for medical applications,especially dental caries.This technology is harmless and thus suitable for biological samples owing to the low energy of THz emission.In this paper,a developed TPI system is used to investigate the two-dimensional(2 D)and three-dimensional(3D)images of different samples from human teeth.After analyzing the measured images of human teeth,the results suggest that the THz parametric technology is capable of investigating the inner side structure of the teeth.This technique can be useful in detecting the defects in all types of human and animal teeth.The measurement and analytical calculations have been performed by using the TPI system and MATLAB,respectively,and both are in good agreement.The characteristics of THz waves and their interactions with the tooth samples are summarized.And the available THz-based technologies,such as TPI,and their potential applications of diagnoses are also presented.
