To overcome the shortcomings of the single-shot autocorrelation SSA where only one pulse width is obtained when the SSA is applied to measure the pulse width of ultrashort laser pulses a modified SSA for measuring the...To overcome the shortcomings of the single-shot autocorrelation SSA where only one pulse width is obtained when the SSA is applied to measure the pulse width of ultrashort laser pulses a modified SSA for measuring the spatiotemporal characteristics of ultrashort laser pulses at different spatial positions is proposed. The spatiotemporal characteristics of femtosecond laser pulses output from the Ti sapphire regenerative amplifier system are experimentally measured by the proposed method. It was found that the complex spatial characteristics are measured accurately.The pulse widths at different spatial positions are various which obey the Gaussian distribution.The pulse width at the same spatial position becomes narrow with the increase in input average power when femtosecond laser pulses pass through a carbon disulfide CS2 nonlinear medium.The experimental results verify that the proposed method is valid for measuring the spatiotemporal characteristics of ultrashort laser pulses at different spatial positions.展开更多
AIM: To investigate the diagnostic ability of single-shot echo-planar imaging(EPI) diffusion-weighted imaging (DWI) to differentiate between malignant and benign pancreatic lesions. METHODS: A computerized search was ...AIM: To investigate the diagnostic ability of single-shot echo-planar imaging(EPI) diffusion-weighted imaging (DWI) to differentiate between malignant and benign pancreatic lesions. METHODS: A computerized search was performed on Pub Med, MEDLINE and EMBASE up to August 2014. Nine studies(10 sets of data) with a total of 304 malignant pancreatic lesions and 188 benign pancreatic lesions were included. The characteristics of each study included the study name, year of publication, magnetic resonance modalities used, patient population, strength of field, pulse time, repetition time, echo time(TE), maximum b factor, mean age, mean body weight, fat suppression, number of benign and malignant lesions, and true positive, true negative, false positive and false negative results. All analyses were performed using Meta-Di Sc and Stata 11.0.RESULTS: The pooled sensitivity and specificity of singleshot EPI DWI were 0.83(95%CI: 0.79-0.87) and 0.77(95%CI: 0.70-0.83), respectively. The positive likelihood ratio and negative likelihood ratio were 5.09(95%CI: 2.19-11.84) and 0.23(95%CI: 0.15-0.36), respectively. The P value for the χ2 heterogeneity for all pooled estimates was < 0.05. From the fitted summary receiver operating characteristic curve, the area under the curve and Q* index were 0.89 and 0.82, respectively. Publication bias was not present(t = 0.58, P = 0.58). Meta-regression analysis indicated that fat suppression, mean age, TE, and maximum b factor were not sources of heterogeneity(all P > 0.05). CONCLUSION: Single-shot EPI DWI is useful to differentiate between malignant and benign pancreatic lesions. Lesion size ≥ 2 cm is the limit for the diagnosis of early lesions.展开更多
According to electro-optical sampling theory, we propose a new method to detect the spatiotemporal field of a single- shot terahertz pulse by spectral holography for the first time. The single-shot terahertz pulse is ...According to electro-optical sampling theory, we propose a new method to detect the spatiotemporal field of a single- shot terahertz pulse by spectral holography for the first time. The single-shot terahertz pulse is coupled into a broadened chirped femtosecond pulse according to electro-optical sampling theory in the detecting system. Then the reference wave and the signal wave are split by Dammann grating and spread into the interference band-pass filter. The filtered sub-waves are at different central-frequencies because of the different incident angles. These sub-waves at different central-frequencies interfere to form sub-holograms, which are recorded in a single frame of a charge coupled device （CCD）. The sub-holograms are numerically processed, and the spatiotemporal field distribution of the original terahertz pulse is reconstructed. The computer simulations verify the feasibility of the proposed method.展开更多
A new terahertz dispersive device designed for single-shot spectral measurements of broadband terahertz pulses is proposed. With two-dimensional quasi-randomly distributed element design, the device exhibits approxima...A new terahertz dispersive device designed for single-shot spectral measurements of broadband terahertz pulses is proposed. With two-dimensional quasi-randomly distributed element design, the device exhibits approximately the dispersive property of single-order diffraction in far field. Its far-field diffraction pattern is experimentally verified employing a continuous terahertz source centered at 2.52 THz and a pyroelectric focal-plane-array camera, which is in good agreement with the numerical result. The device provides a new approach for direct single-shot spectral measurements of broadband terahertz waves.展开更多
X-ray grating interferometer has attracted widely attention in the past years due to its capability in achieving x-ray phase contrast imaging with low brilliance source. However, the widely used phase stepping informa...X-ray grating interferometer has attracted widely attention in the past years due to its capability in achieving x-ray phase contrast imaging with low brilliance source. However, the widely used phase stepping information extraction method reduces system stability and prolongs data acquisition time by several times compared with conventional x-ray absorption- based imaging. The mechanical stepping can be avoided by using a staggered grating, but at the cost of low vertical spatial resolution. In this paper, employing a modified staggered grating and the angular signal radiography, we proposed a single-shot grating-based x-ray differential phase contrast imaging with decent vertical spatial resolution. The theoretical framework was deduced and proved by numerical experiments. Absorption, phase, and scattering computed tomography can be performed without phase stepping. Therefore, we believe this fast and highly stable imaging method with decent resolution would be widely applied in x-ray grating-based phase contrast imaging.展开更多
Terahertz(THz) waves have shown a broad prospect in the analysis of some dielectric materials because of their special properties. For the ultrafast irreversible processes, the THz single-shot measurement is a good ch...Terahertz(THz) waves have shown a broad prospect in the analysis of some dielectric materials because of their special properties. For the ultrafast irreversible processes, the THz single-shot measurement is a good choice. In this paper,a single-shot system is investigated, where a pump beam is used to generate THz pulses with high electrical field by optical rectification in LiNbO3, the probe beam with wavefront tilted by a blazed grating is used for single-shot measurement. The time window is up to 90 ps, the signal to noise ratio is 2000 : 1, the spectrum covers from 0.1 THz to about 2.0 THz, and the spectral resolution is 0.011 THz. The single-shot measurement result agrees well with that of a traditional electrical-optic sampling method.展开更多
In this paper,a single-shot 360-degree cranial deformity detection system using digital image correlation(DIC)is presented to quickly obtain and detect accurate 3D data of infants’cra-nium.By introducing plane mirror...In this paper,a single-shot 360-degree cranial deformity detection system using digital image correlation(DIC)is presented to quickly obtain and detect accurate 3D data of infants’cra-nium.By introducing plane mirrors into a stereo 3D DIC measurement system,a multi-view 3D imaging model is established to convert 3D data from real and virtual perspectives into 360-degree 3D data of the tested infant cranium,achieving single-shot and panoramic 3D measurement.Exper-imental results showed that the performance and measurement accuracy of the proposed system can meet the requirements for cranial deformity detection,which provides a fast,accurate,and low-cost solution medically.展开更多
Based on the frequency-to-time mapping relation of the linearly chirped pulse, the temporal phase shift induced by a laser-excited wake in a helium gas jet is measured using a chirped-pulse spectral interferometry wi...Based on the frequency-to-time mapping relation of the linearly chirped pulse, the temporal phase shift induced by a laser-excited wake in a helium gas jet is measured using a chirped-pulse spectral interferometry with ～ 140 fs resolution over a temporal region of I ps in a single shot. In this measurement, the image of the wake is obtained with one-dimensional spatial resolution and temporal resolution limited only by the bandwidth and chirp of the pulse. The ＇bubbles＇ feature of the wake structure, along with multiple wakes excited by the main lobe and the side lobe of a laser focal-spot, is captured simultaneously.展开更多
Single-shot ultrafast multidimensional optical imaging(UMOI)combines ultrahigh temporal resolution with multidimensional imaging capabilities in a snapshot,making it an essential tool for real-time detection and analy...Single-shot ultrafast multidimensional optical imaging(UMOI)combines ultrahigh temporal resolution with multidimensional imaging capabilities in a snapshot,making it an essential tool for real-time detection and analysis of ultrafast scenes.However,current single-shot UMOI techniques cannot simultaneously capture the spatial-temporal-spectral complex amplitude information,hampering it from complete analyses of ultrafast scenes.To address this issue,we propose a single-shot spatial-temporal-spectral complex amplitude imaging(STS-CAI)technique using wavelength and time multiplexing.By employing precise modulation of a broadband pulse via an encoding plate in coherent diffraction imaging and spatial-temporal shearing through a wide-open-slit streak camera,dual-mode multiplexing image reconstruction of wavelength and time is achieved,which significantly enhances the efficiency of information acquisition.Experimentally,a custom-built STS-CAI apparatus precisely measures the spatiotemporal characteristics of picosecond spatiotemporally chirped and spatial vortex pulses,respectively.STS-CAI demonstrates both ultrahigh temporal resolution and robust phase sensitivity.Prospectively,this technique is valuable for spatiotemporal coupling measurements of large-aperture ultrashort pulses and offers promising applications in both fundamental research and applied sciences.展开更多
Purpose-Single-shot multi-category clothing recognition and retrieval play a crucial role in online searching and offline settlement scenarios.Existing clothing recognition methods based on RGBD clothing images often ...Purpose-Single-shot multi-category clothing recognition and retrieval play a crucial role in online searching and offline settlement scenarios.Existing clothing recognition methods based on RGBD clothing images often suffer from high-dimensional feature representations,leading to compromised performance and efficiency.Design/methodology/approach-To address this issue,this paper proposes a novel method called Manifold Embedded Discriminative Feature Selection(MEDFS)to select global and local features,thereby reducing the dimensionality of the feature representation and improving performance.Specifically,by combining three global features and three local features,a low-dimensional embedding is constructed to capture the correlations between features and categories.The MEDFS method designs an optimization framework utilizing manifold mapping and sparse regularization to achieve feature selection.The optimization objective is solved using an alternating iterative strategy,ensuring convergence.Findings-Empirical studies conducted on a publicly available RGBD clothing image dataset demonstrate that the proposed MEDFS method achieves highly competitive clothing classification performance while maintaining efficiency in clothing recognition and retrieval.Originality/value-This paper introduces a novel approach for multi-category clothing recognition and retrieval,incorporating the selection of global and local features.The proposed method holds potential for practical applications in real-world clothing scenarios.展开更多
Compressed ultrafast photography(CUP)is a burgeoning single-shot computational imaging technique that provides an imaging speed as high as 10 trillion frames per second and a sequence depth of up to a few hundred fram...Compressed ultrafast photography(CUP)is a burgeoning single-shot computational imaging technique that provides an imaging speed as high as 10 trillion frames per second and a sequence depth of up to a few hundred frames.This technique synergizes compressed sensing and the streak camera technique to capture nonrepeatable ultrafast transient events with a single shot.With recent unprecedented technical developments and extensions of this methodology,it has been widely used in ultrafast optical imaging and metrology,ultrafast electron diffraction and microscopy,and information security protection.We review the basic principles of CUP,its recent advances in data acquisition and image reconstruction,its fusions with other modalities,and its unique applications in multiple research fields.展开更多
To seek high signal-to-noise ratio(SNR) is critical but challenging for single-shot intense terahertz(THz)coherent detection. This paper presents an improved common-path spectral interferometer for single-shot THz det...To seek high signal-to-noise ratio(SNR) is critical but challenging for single-shot intense terahertz(THz)coherent detection. This paper presents an improved common-path spectral interferometer for single-shot THz detection with a single chirped pulse as the probe for THz electro-optic(EO) sampling. Here, the spectral interference occurs between the two orthogonal polarization components with a required relative time delay generated with only a birefringent plate after the EO sensor. Our experiments show that this interferometer can effectively suppress the noise usually suffered in a non-common-path interferometer. The measured single-shot SNR is up to 88.85, and the measured THz waveforms are independent of the orientation of the used Zn Te EO sensor, so it is easy to operate and the results are more reliable. These features mean that the interferometer is quite qualified for applications where strong THz pulses, usually with single-shot or low repetition rate, are indispensable.展开更多
Orbital angular momentum (OAM) spectrum diagnosis is a fundamental building block for diverseOAM-based systems. Among others, the simple on-axis interferometric measurement can retrieve theamplitude and phase informat...Orbital angular momentum (OAM) spectrum diagnosis is a fundamental building block for diverseOAM-based systems. Among others, the simple on-axis interferometric measurement can retrieve theamplitude and phase information of complex OAM spectra in a few shots. Yet, its single-shot retrievalremains elusive, due to the signal–signal beat interference inherent in the measurement. Here, weintroduce the concept of Kramers–Kronig (KK) receiver in coherent communications to the OAM domain,enabling rigorous, single-shot OAM spectrum measurement. We explain in detail the working principle andthe requirement of the KK method and then apply the technique to precisely measure variouscharacteristic OAM states. In addition, we discuss the effects of the carrier-to-signal power ratio and thenumber of sampling points essential for rigorous retrieval and evaluate the performance on a large set ofrandom OAM spectra and high-dimensional spaces. Single-shot KK interferometry shows enormouspotential for characterizing complex OAM states in real time.展开更多
We propose a novel on-line beam diagnostic method based on single-shot beam splitting phase retrieval. The incident beam to be measured is diffracted into many replicas by a Dammann grating and then propagates through...We propose a novel on-line beam diagnostic method based on single-shot beam splitting phase retrieval. The incident beam to be measured is diffracted into many replicas by a Dammann grating and then propagates through a weakly scattering phase plate with a known structure; the exiting beams propagate along their original direction and form an array of diffraction patterns on the detector plane. By applying the intensity of diffraction patterns into an iterative algorithm and calculating between the grating plane, weakly scattering plane, and detector plane, the complex field of the incident beam can be reconstructed rapidly; the feasibility of this method is verified experimentally with wavelengths of 1053 and 632.8 nm.展开更多
X-ray free-electron lasers(FELs)provide cutting-edge tools for fundamental researches to study nature down to the atomic level at a time-scale that fits this resolution.A precise knowledge of temporal information of F...X-ray free-electron lasers(FELs)provide cutting-edge tools for fundamental researches to study nature down to the atomic level at a time-scale that fits this resolution.A precise knowledge of temporal information of FEL pulses is the central issue for its applications.Here we proposed and demonstrated a novel method to determine the FEL temporal profiles online.This robust method,designed for ultrafast FELs,allows researchers to acquire real-time longitudinal profiles of FEL pulses as well as their arrive times with respect to the external optical laser with a resolution better than 6 fs.Based on this method,we can also directly measure various properties of FEL pulses and correlations between them online.This helps us to further understand the FEL lasing processes and realize the generation of stable,nearly fully coherent soft X-ray laser pulses at the Shanghai Soft X-ray FEL facility.This method will enhance the experimental opportunities for ultrafast science in various areas.展开更多
Laser–plasma interactions have been studied in detail over the past twenty years,as they show great potential for the next generation of particle accelerators.The interaction between an ultra-intense laser and a soli...Laser–plasma interactions have been studied in detail over the past twenty years,as they show great potential for the next generation of particle accelerators.The interaction between an ultra-intense laser and a solid-state target produces a huge amount of particles:electrons and photons(X-rays andγ-rays)at early stages of the process,with protons and ions following them.At SPARC LAB Test Facility we have set up two diagnostic lines to perform simultaneous temporally resolved measurements on both electrons and protons.展开更多
Pulse contrast is a crucial parameter of high peak-power lasers since the prepulse noise may disturb laser–plasma interactions. Contrast measurement is thus a prerequisite to tackle the contrast challenge in high pea...Pulse contrast is a crucial parameter of high peak-power lasers since the prepulse noise may disturb laser–plasma interactions. Contrast measurement is thus a prerequisite to tackle the contrast challenge in high peak-power lasers.This paper presents the progress review of single-shot cross-correlator(SSCC) for real-time contrast characterization.We begin with the key technologies that enable an SSCC to simultaneously possess high dynamic range(1010), large temporal window(50–70 ps) and high fidelity. We also summarize the instrumentation of SSCC prototypes and their applications on five sets of petawatt laser facilities in China. Finally, we discuss how to extend contrast measurements from time domain to spatiotemporal domain. Real-time and high-dynamic-range contrast measurements, provided by SSCC, can not only characterize various complex noises in high peak-power lasers but also guide the system optimization.展开更多
Incoherent optical processing of microwave signals,where low-coherence broadband light sources are employed instead of costly mode locked lasers,has attracted great interest thanks to its wide applications in microwav...Incoherent optical processing of microwave signals,where low-coherence broadband light sources are employed instead of costly mode locked lasers,has attracted great interest thanks to its wide applications in microwave photonics filtering[1–3],arbitrary generation[4–6]and analog to digital conversion[7]。展开更多
In strong-field physics experiments with ultraintense lasers,a single-shot cross-correlator(SSCC)is essential for fast optimization of the pulse contrast and meaningful comparison with theory for each pulse shot.To si...In strong-field physics experiments with ultraintense lasers,a single-shot cross-correlator(SSCC)is essential for fast optimization of the pulse contrast and meaningful comparison with theory for each pulse shot.To simultaneously characterize an ultrashort pulse and its long pedestal,the SSCC device must have both a high resolution and a large temporal window.However,the resolution and window in all kinds of single-shot measurement contradict each other in principle.Here we propose and demonstrate a novel SSCC device with two separate measurement channels:channel-1 for the large-window pedestal measurement has a moderate resolution but a large window,while channel-2 for the ultrashort pulse measurement has a small window but a high resolution;this allows the accurate characterization of the pulse contrast in a single shot.A two-channel SSCC device with a 200-fs resolution and 114-ps window has been developed and tested for its application in ultraintense lasers at 800 nm.展开更多
Detection efficiency plays an increasingly important role in object detection tasks.One-stage methods are widely adopted in real life because of their high efficiency especially in some real-time detection tasks such ...Detection efficiency plays an increasingly important role in object detection tasks.One-stage methods are widely adopted in real life because of their high efficiency especially in some real-time detection tasks such as face recognition and self-driving cars.RetinaMask achieves significant progress in the field of one-stage detectors by adding a semantic segmentation branch,but it has limitation in detecting multi-scale objects.To solve this problem,this paper proposes RetinaMask with Gate(RMG)model,consisting of four main modules.It develops RetinaMask with a gate mechanism,which extracts and combines features at different levels more effectively according to the size of objects.It firstly extracted multi-level features from input image by ResNet.Secondly,it constructed a fused feature pyramid through feature pyramid network,then gate mechanism was employed to adaptively enhance and integrate features at various scales with the respect to the size of object.Finally,three prediction heads were added for classification,localization and mask prediction,driving the model to learn with mask prediction.The predictions of all levels were integrated during the post-processing.The augment network shows better performance in object detection without the increase of computation cost and inference time,especially for small objects.展开更多
基金The National Natural Science Foundation of China(No.61171081,No.61471164)the Natural Science Foundation of Hunan Province(No.14JJ6043)
文摘To overcome the shortcomings of the single-shot autocorrelation SSA where only one pulse width is obtained when the SSA is applied to measure the pulse width of ultrashort laser pulses a modified SSA for measuring the spatiotemporal characteristics of ultrashort laser pulses at different spatial positions is proposed. The spatiotemporal characteristics of femtosecond laser pulses output from the Ti sapphire regenerative amplifier system are experimentally measured by the proposed method. It was found that the complex spatial characteristics are measured accurately.The pulse widths at different spatial positions are various which obey the Gaussian distribution.The pulse width at the same spatial position becomes narrow with the increase in input average power when femtosecond laser pulses pass through a carbon disulfide CS2 nonlinear medium.The experimental results verify that the proposed method is valid for measuring the spatiotemporal characteristics of ultrashort laser pulses at different spatial positions.
基金Supported by Key Program of Scientific Research of Fujian Medical University,FMU 09ZD014
文摘AIM: To investigate the diagnostic ability of single-shot echo-planar imaging(EPI) diffusion-weighted imaging (DWI) to differentiate between malignant and benign pancreatic lesions. METHODS: A computerized search was performed on Pub Med, MEDLINE and EMBASE up to August 2014. Nine studies(10 sets of data) with a total of 304 malignant pancreatic lesions and 188 benign pancreatic lesions were included. The characteristics of each study included the study name, year of publication, magnetic resonance modalities used, patient population, strength of field, pulse time, repetition time, echo time(TE), maximum b factor, mean age, mean body weight, fat suppression, number of benign and malignant lesions, and true positive, true negative, false positive and false negative results. All analyses were performed using Meta-Di Sc and Stata 11.0.RESULTS: The pooled sensitivity and specificity of singleshot EPI DWI were 0.83(95%CI: 0.79-0.87) and 0.77(95%CI: 0.70-0.83), respectively. The positive likelihood ratio and negative likelihood ratio were 5.09(95%CI: 2.19-11.84) and 0.23(95%CI: 0.15-0.36), respectively. The P value for the χ2 heterogeneity for all pooled estimates was < 0.05. From the fitted summary receiver operating characteristic curve, the area under the curve and Q* index were 0.89 and 0.82, respectively. Publication bias was not present(t = 0.58, P = 0.58). Meta-regression analysis indicated that fat suppression, mean age, TE, and maximum b factor were not sources of heterogeneity(all P > 0.05). CONCLUSION: Single-shot EPI DWI is useful to differentiate between malignant and benign pancreatic lesions. Lesion size ≥ 2 cm is the limit for the diagnosis of early lesions.
基金supported by the National Natural Science Foundation of China(Grant No.10904079)
文摘According to electro-optical sampling theory, we propose a new method to detect the spatiotemporal field of a single- shot terahertz pulse by spectral holography for the first time. The single-shot terahertz pulse is coupled into a broadened chirped femtosecond pulse according to electro-optical sampling theory in the detecting system. Then the reference wave and the signal wave are split by Dammann grating and spread into the interference band-pass filter. The filtered sub-waves are at different central-frequencies because of the different incident angles. These sub-waves at different central-frequencies interfere to form sub-holograms, which are recorded in a single frame of a charge coupled device （CCD）. The sub-holograms are numerically processed, and the spatiotemporal field distribution of the original terahertz pulse is reconstructed. The computer simulations verify the feasibility of the proposed method.
基金Project supported by the Foundation of Science and Technology Development of China Academy of Engineering Physics(Grant No.2011B0102023)the Foundation of Plasma Physics Laboratory(Grant No.9140C680304110C6806)
文摘A new terahertz dispersive device designed for single-shot spectral measurements of broadband terahertz pulses is proposed. With two-dimensional quasi-randomly distributed element design, the device exhibits approximately the dispersive property of single-order diffraction in far field. Its far-field diffraction pattern is experimentally verified employing a continuous terahertz source centered at 2.52 THz and a pyroelectric focal-plane-array camera, which is in good agreement with the numerical result. The device provides a new approach for direct single-shot spectral measurements of broadband terahertz waves.
基金supported by the National Natural Science Foundation of China(Grant Nos.11275204,11475175,and 11405175)the China Postdoctoral Science Foundation(Grant No.2017M612097)the Fundamental Research Funds for the Central Universities(Grant No.WK2310000065)
文摘X-ray grating interferometer has attracted widely attention in the past years due to its capability in achieving x-ray phase contrast imaging with low brilliance source. However, the widely used phase stepping information extraction method reduces system stability and prolongs data acquisition time by several times compared with conventional x-ray absorption- based imaging. The mechanical stepping can be avoided by using a staggered grating, but at the cost of low vertical spatial resolution. In this paper, employing a modified staggered grating and the angular signal radiography, we proposed a single-shot grating-based x-ray differential phase contrast imaging with decent vertical spatial resolution. The theoretical framework was deduced and proved by numerical experiments. Absorption, phase, and scattering computed tomography can be performed without phase stepping. Therefore, we believe this fast and highly stable imaging method with decent resolution would be widely applied in x-ray grating-based phase contrast imaging.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61427814 and 61575161)the National Key Research and Development Program of China(Grant No.2017YFA0701005)the Natural Science Foundation of Shaanxi Province,China(Grant No.2019JZ-04)。
文摘Terahertz(THz) waves have shown a broad prospect in the analysis of some dielectric materials because of their special properties. For the ultrafast irreversible processes, the THz single-shot measurement is a good choice. In this paper,a single-shot system is investigated, where a pump beam is used to generate THz pulses with high electrical field by optical rectification in LiNbO3, the probe beam with wavefront tilted by a blazed grating is used for single-shot measurement. The time window is up to 90 ps, the signal to noise ratio is 2000 : 1, the spectrum covers from 0.1 THz to about 2.0 THz, and the spectral resolution is 0.011 THz. The single-shot measurement result agrees well with that of a traditional electrical-optic sampling method.
基金supported by the National Natural Science Found-ation of China(No.62075096)Leading Technology of Ji-angsu Basic Research Plan(No.BK20192003)+4 种基金National De-fense Science and Technology Foundation of China(No.2019-JCJQ-JJ-381)“333 Engineering”Research Project of Jiangsu Province(No.BRA2016407)Jiangsu Provincial“One Belt and One Road”Innovation Cooperation Project(No.BZ2020007)Fundamental Research Funds for the Central Universities(Nos.30921011208,30919011222 and 30920032101)Open Research Fund of Jiangsu Key Laboratory of Spectral Imaging&Intelligent Sense(No.JS-GP202105).
文摘In this paper,a single-shot 360-degree cranial deformity detection system using digital image correlation(DIC)is presented to quickly obtain and detect accurate 3D data of infants’cra-nium.By introducing plane mirrors into a stereo 3D DIC measurement system,a multi-view 3D imaging model is established to convert 3D data from real and virtual perspectives into 360-degree 3D data of the tested infant cranium,achieving single-shot and panoramic 3D measurement.Exper-imental results showed that the performance and measurement accuracy of the proposed system can meet the requirements for cranial deformity detection,which provides a fast,accurate,and low-cost solution medically.
基金Supported by the National Natural Science Foundation of China under Grant No 61377102the Defense Industrial Technology Development Program under Grant No B1520133010
文摘Based on the frequency-to-time mapping relation of the linearly chirped pulse, the temporal phase shift induced by a laser-excited wake in a helium gas jet is measured using a chirped-pulse spectral interferometry with ～ 140 fs resolution over a temporal region of I ps in a single shot. In this measurement, the image of the wake is obtained with one-dimensional spatial resolution and temporal resolution limited only by the bandwidth and chirp of the pulse. The ＇bubbles＇ feature of the wake structure, along with multiple wakes excited by the main lobe and the side lobe of a laser focal-spot, is captured simultaneously.
基金supported by the National Natural Science Foundation of China(Grant Nos.12074121,12274139,and 12325408)the China Postdoctoral Science Foundation(Grant Nos.2023M743252 and 2024T170846)+1 种基金the Fundamental Research Funds for the Central Universities(Grant No.YZY24014)the Key Research and Development Program of Zhejiang Province(Grant No.2024SSYS0014).
文摘Single-shot ultrafast multidimensional optical imaging(UMOI)combines ultrahigh temporal resolution with multidimensional imaging capabilities in a snapshot,making it an essential tool for real-time detection and analysis of ultrafast scenes.However,current single-shot UMOI techniques cannot simultaneously capture the spatial-temporal-spectral complex amplitude information,hampering it from complete analyses of ultrafast scenes.To address this issue,we propose a single-shot spatial-temporal-spectral complex amplitude imaging(STS-CAI)technique using wavelength and time multiplexing.By employing precise modulation of a broadband pulse via an encoding plate in coherent diffraction imaging and spatial-temporal shearing through a wide-open-slit streak camera,dual-mode multiplexing image reconstruction of wavelength and time is achieved,which significantly enhances the efficiency of information acquisition.Experimentally,a custom-built STS-CAI apparatus precisely measures the spatiotemporal characteristics of picosecond spatiotemporally chirped and spatial vortex pulses,respectively.STS-CAI demonstrates both ultrahigh temporal resolution and robust phase sensitivity.Prospectively,this technique is valuable for spatiotemporal coupling measurements of large-aperture ultrashort pulses and offers promising applications in both fundamental research and applied sciences.
文摘Purpose-Single-shot multi-category clothing recognition and retrieval play a crucial role in online searching and offline settlement scenarios.Existing clothing recognition methods based on RGBD clothing images often suffer from high-dimensional feature representations,leading to compromised performance and efficiency.Design/methodology/approach-To address this issue,this paper proposes a novel method called Manifold Embedded Discriminative Feature Selection(MEDFS)to select global and local features,thereby reducing the dimensionality of the feature representation and improving performance.Specifically,by combining three global features and three local features,a low-dimensional embedding is constructed to capture the correlations between features and categories.The MEDFS method designs an optimization framework utilizing manifold mapping and sparse regularization to achieve feature selection.The optimization objective is solved using an alternating iterative strategy,ensuring convergence.Findings-Empirical studies conducted on a publicly available RGBD clothing image dataset demonstrate that the proposed MEDFS method achieves highly competitive clothing classification performance while maintaining efficiency in clothing recognition and retrieval.Originality/value-This paper introduces a novel approach for multi-category clothing recognition and retrieval,incorporating the selection of global and local features.The proposed method holds potential for practical applications in real-world clothing scenarios.
基金This work was partially supported by the National Natural Science Foundation of China(Grant Nos.91850202,11774094,11727810,11804097,and 61720106009)the Science and Technology Commission of Shanghai Municipality(Grant Nos.19560710300 and 17ZR146900)the China Postdoctoral Science Foundation(Grant No.2018M641958).
文摘Compressed ultrafast photography(CUP)is a burgeoning single-shot computational imaging technique that provides an imaging speed as high as 10 trillion frames per second and a sequence depth of up to a few hundred frames.This technique synergizes compressed sensing and the streak camera technique to capture nonrepeatable ultrafast transient events with a single shot.With recent unprecedented technical developments and extensions of this methodology,it has been widely used in ultrafast optical imaging and metrology,ultrafast electron diffraction and microscopy,and information security protection.We review the basic principles of CUP,its recent advances in data acquisition and image reconstruction,its fusions with other modalities,and its unique applications in multiple research fields.
基金National Natural Science Foundation of China(NSFC)(61490710,61775142,61705132)Science and Technology Planning Project of Guangdong Province(2016B050501005)Specialized Research Fund for the Shenzhen Strategic Emerging Industries Development(JCYJ20150324141711651,JCYJ20150525092941064,JCYJ20170412105812811)
文摘To seek high signal-to-noise ratio(SNR) is critical but challenging for single-shot intense terahertz(THz)coherent detection. This paper presents an improved common-path spectral interferometer for single-shot THz detection with a single chirped pulse as the probe for THz electro-optic(EO) sampling. Here, the spectral interference occurs between the two orthogonal polarization components with a required relative time delay generated with only a birefringent plate after the EO sensor. Our experiments show that this interferometer can effectively suppress the noise usually suffered in a non-common-path interferometer. The measured single-shot SNR is up to 88.85, and the measured THz waveforms are independent of the orientation of the used Zn Te EO sensor, so it is easy to operate and the results are more reliable. These features mean that the interferometer is quite qualified for applications where strong THz pulses, usually with single-shot or low repetition rate, are indispensable.
基金supported by the National Key Research and Development Program of China (2018YFB1801803, 2019YFA0706302)the Basic and Applied Basic Research Foundation of Guangdong Province (2021B1515020093, 2021B1515120057)+1 种基金the Local Innovative and Research Teams Project of Guangdong Pearl River Talents Program (2017BT01X121)the Swiss National Science Foundation (P2ELP2_199825)
文摘Orbital angular momentum (OAM) spectrum diagnosis is a fundamental building block for diverseOAM-based systems. Among others, the simple on-axis interferometric measurement can retrieve theamplitude and phase information of complex OAM spectra in a few shots. Yet, its single-shot retrievalremains elusive, due to the signal–signal beat interference inherent in the measurement. Here, weintroduce the concept of Kramers–Kronig (KK) receiver in coherent communications to the OAM domain,enabling rigorous, single-shot OAM spectrum measurement. We explain in detail the working principle andthe requirement of the KK method and then apply the technique to precisely measure variouscharacteristic OAM states. In addition, we discuss the effects of the carrier-to-signal power ratio and thenumber of sampling points essential for rigorous retrieval and evaluate the performance on a large set ofrandom OAM spectra and high-dimensional spaces. Single-shot KK interferometry shows enormouspotential for characterizing complex OAM states in real time.
基金supported by the National Natural Science Foundation of China(No.61675215)the Shanghai Sailing Program(No.18YF1426600)
文摘We propose a novel on-line beam diagnostic method based on single-shot beam splitting phase retrieval. The incident beam to be measured is diffracted into many replicas by a Dammann grating and then propagates through a weakly scattering phase plate with a known structure; the exiting beams propagate along their original direction and form an array of diffraction patterns on the detector plane. By applying the intensity of diffraction patterns into an iterative algorithm and calculating between the grating plane, weakly scattering plane, and detector plane, the complex field of the incident beam can be reconstructed rapidly; the feasibility of this method is verified experimentally with wavelengths of 1053 and 632.8 nm.
文摘X-ray free-electron lasers(FELs)provide cutting-edge tools for fundamental researches to study nature down to the atomic level at a time-scale that fits this resolution.A precise knowledge of temporal information of FEL pulses is the central issue for its applications.Here we proposed and demonstrated a novel method to determine the FEL temporal profiles online.This robust method,designed for ultrafast FELs,allows researchers to acquire real-time longitudinal profiles of FEL pulses as well as their arrive times with respect to the external optical laser with a resolution better than 6 fs.Based on this method,we can also directly measure various properties of FEL pulses and correlations between them online.This helps us to further understand the FEL lasing processes and realize the generation of stable,nearly fully coherent soft X-ray laser pulses at the Shanghai Soft X-ray FEL facility.This method will enhance the experimental opportunities for ultrafast science in various areas.
文摘Laser–plasma interactions have been studied in detail over the past twenty years,as they show great potential for the next generation of particle accelerators.The interaction between an ultra-intense laser and a solid-state target produces a huge amount of particles:electrons and photons(X-rays andγ-rays)at early stages of the process,with protons and ions following them.At SPARC LAB Test Facility we have set up two diagnostic lines to perform simultaneous temporally resolved measurements on both electrons and protons.
基金supported by the National Natural Science Foundation of China (NSFC) (Nos. 61705128, 61727820, and 91850203)Shanghai Sailing Program (No. 17YF1409100)Natural Science Foundation of Shanghai (No. 17ZR1414000)
文摘Pulse contrast is a crucial parameter of high peak-power lasers since the prepulse noise may disturb laser–plasma interactions. Contrast measurement is thus a prerequisite to tackle the contrast challenge in high peak-power lasers.This paper presents the progress review of single-shot cross-correlator(SSCC) for real-time contrast characterization.We begin with the key technologies that enable an SSCC to simultaneously possess high dynamic range(1010), large temporal window(50–70 ps) and high fidelity. We also summarize the instrumentation of SSCC prototypes and their applications on five sets of petawatt laser facilities in China. Finally, we discuss how to extend contrast measurements from time domain to spatiotemporal domain. Real-time and high-dynamic-range contrast measurements, provided by SSCC, can not only characterize various complex noises in high peak-power lasers but also guide the system optimization.
文摘Incoherent optical processing of microwave signals,where low-coherence broadband light sources are employed instead of costly mode locked lasers,has attracted great interest thanks to its wide applications in microwave photonics filtering[1–3],arbitrary generation[4–6]and analog to digital conversion[7]。
基金supported by the National Natural Science Foundation of China(NSFC)(Nos.61727820 and 62122049)the Science and Technology Commission of Shanghai Municipality(Nos.21QA1404600 and 22JC1401900)+1 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences,China(No.XDA25020306)Jingui Ma would like to thank the sponsorship of the Yangyang Development Fund。
文摘In strong-field physics experiments with ultraintense lasers,a single-shot cross-correlator(SSCC)is essential for fast optimization of the pulse contrast and meaningful comparison with theory for each pulse shot.To simultaneously characterize an ultrashort pulse and its long pedestal,the SSCC device must have both a high resolution and a large temporal window.However,the resolution and window in all kinds of single-shot measurement contradict each other in principle.Here we propose and demonstrate a novel SSCC device with two separate measurement channels:channel-1 for the large-window pedestal measurement has a moderate resolution but a large window,while channel-2 for the ultrashort pulse measurement has a small window but a high resolution;this allows the accurate characterization of the pulse contrast in a single shot.A two-channel SSCC device with a 200-fs resolution and 114-ps window has been developed and tested for its application in ultraintense lasers at 800 nm.
基金the National Natural Science Foundation of China under Grant No.61672181。
文摘Detection efficiency plays an increasingly important role in object detection tasks.One-stage methods are widely adopted in real life because of their high efficiency especially in some real-time detection tasks such as face recognition and self-driving cars.RetinaMask achieves significant progress in the field of one-stage detectors by adding a semantic segmentation branch,but it has limitation in detecting multi-scale objects.To solve this problem,this paper proposes RetinaMask with Gate(RMG)model,consisting of four main modules.It develops RetinaMask with a gate mechanism,which extracts and combines features at different levels more effectively according to the size of objects.It firstly extracted multi-level features from input image by ResNet.Secondly,it constructed a fused feature pyramid through feature pyramid network,then gate mechanism was employed to adaptively enhance and integrate features at various scales with the respect to the size of object.Finally,three prediction heads were added for classification,localization and mask prediction,driving the model to learn with mask prediction.The predictions of all levels were integrated during the post-processing.The augment network shows better performance in object detection without the increase of computation cost and inference time,especially for small objects.
