The popularity of deep learning has boosted computer-generated holography(CGH)as a vibrant research field,particularly physics-driven unsupervised learning.Nevertheless,present unsupervised CGH models have not yet exp...The popularity of deep learning has boosted computer-generated holography(CGH)as a vibrant research field,particularly physics-driven unsupervised learning.Nevertheless,present unsupervised CGH models have not yet explored the potential of generating full-color 3D holograms through a unified framework.In this study,we propose a lightweight multiwavelength network model capable of high-fidelity and efficient full-color hologram generation in both 2D and 3D display,called IncepHoloRGB.The high-speed simultaneous generation of RGB holograms at 191 frames per second(FPS)is based on Inception sampling blocks and multi-wavelength propagation module integrated with depth-traced superimposition,achieving an average structural similarity(SSIM)of 0.88 and peak signal-to-noise ratio(PSNR)of 29.00 on the DIV2K test set in reconstruction.Full-color reconstruction of numerical simulations and optical experiments shows that IncepHoloRGB is versatile to diverse scenarios and can obtain authentic full-color holographic 3D display within a unified network model,paving the way for applications towards real-time dynamic naked-eye 3D display,virtual and augmented reality(VR/AR)systems.展开更多
Deep learning offers a novel opportunity to achieve both high-quality and high-speed computer-generated holography(CGH).Current data-driven deep learning algorithms face the challenge that the labeled training dataset...Deep learning offers a novel opportunity to achieve both high-quality and high-speed computer-generated holography(CGH).Current data-driven deep learning algorithms face the challenge that the labeled training datasets limit the training performance and generalization.The model-driven deep learning introduces the diffraction model into the neural network.It eliminates the need for the labeled training dataset and has been extensively applied to hologram generation.However,the existing model-driven deep learning algorithms face the problem of insufficient constraints.In this study,we propose a model-driven neural network capable of high-fidelity 4K computer-generated hologram generation,called 4K Diffraction Model-driven Network(4K-DMDNet).The constraint of the reconstructed images in the frequency domain is strengthened.And a network structure that combines the residual method and sub-pixel convolution method is built,which effectively enhances the fitting ability of the network for inverse problems.The generalization of the 4K-DMDNet is demonstrated with binary,grayscale and 3D images.High-quality full-color optical reconstructions of the 4K holograms have been achieved at the wavelengths of 450 nm,520 nm,and 638 nm.展开更多
We propose a Phong shading approximation,which gives the amplitude of each point inside the triangle through linear interpolation within the framework of self-similarity segmentation and affine transformation in polyg...We propose a Phong shading approximation,which gives the amplitude of each point inside the triangle through linear interpolation within the framework of self-similarity segmentation and affine transformation in polygon-based computer-generated holography.Shading is important as it reflects the geometric properties of the objects.To accurately represent the geometric properties of objects in three-dimensional space,the method involves calculating the amplitude distribution on each triangle and maintaining a complete analytical framework,with the edges of the reconstructed polygons nearly unobservable.Numerical simulations and optical reconstructions demonstrate that the proposed method successfully addresses the issue of edge discontinuity on polygonal surfaces.展开更多
In this paper,we propose,to our knowledge,a new complex-valued dense atrous neural network(CDANN)for phase-only hologram(POH)generation.The network architecture integrates a complex-valued partial convolution(C-PConv)...In this paper,we propose,to our knowledge,a new complex-valued dense atrous neural network(CDANN)for phase-only hologram(POH)generation.The network architecture integrates a complex-valued partial convolution(C-PConv)module into the down-sampling stages of dual U-Net structures,enhancing computational efficiency through selective channelwise processing.To improve feature extraction,we introduce a novel complex-value dense atrous convolution(DAC)module,which employs four cascaded branches with multi-scale atrous convolutions to capture intricate features while maintaining spatial resolution.Additionally,we integrate a spatial pyramid pooling(SPP)module into the U-Net architecture to encode multi-scale contextual features derived from the DAC module.This hierarchical integration expands the U-Net's receptive field while facilitating cross-layer feature fusion.The proposed method achieves an average peak signal-to-noise ratio(PSNR)of 32.19 d B and an average structural similarity index measure(SSIM)of 0.892 within a running time of 24 ms,outperforming conventional approaches.Experiments confirm significant improvements in both reconstruction quality and computational efficiency,making the CDANN suitable for real-time holographic displays.展开更多
We present a novel method for scale-invariant 3D face recognition by integrating computer-generated holography with the Mellin transform.This approach leverages the scale-invariance property of the Mellin transform to...We present a novel method for scale-invariant 3D face recognition by integrating computer-generated holography with the Mellin transform.This approach leverages the scale-invariance property of the Mellin transform to address challenges related to variations in 3D facial sizes during recognition.By applying the Mellin transform to computer-generated holograms and performing correlation between them,which,to the best of our knowledge,is being done for the first time,we have developed a robust recognition framework capable of managing significant scale variations without compromising recognition accuracy.Digital holograms of 3D faces are generated from a face database,and the Mellin transform is employed to enable robust recognition across scale factors ranging from 0.4 to 2.0.Within this range,the method achieves 100%recognition accuracy,as confirmed by both simulation-based and hybrid optical/digital experimental validations.Numerical calculations demonstrate that our method significantly enhances the accuracy and reliability of 3D face recognition,as evidenced by the sharp correlation peaks and higher peak-to-noise ratio(PNR)values than that of using conventional holograms without the Mellin transform.Additionally,the hybrid optical/digital joint transform correlation hardware further validates the method's effectiveness,demonstrating its capability to accurately identify and distinguish 3D faces at various scales.This work provides a promising solution for advanced biometric systems,especially for those which require 3D scale-invariant recognition.展开更多
The rapid advancement of computer-generated holography has bridged deep learning with traditional optical principles in recent years.However,a critical challenge in this evolution is the efficient and accurate convers...The rapid advancement of computer-generated holography has bridged deep learning with traditional optical principles in recent years.However,a critical challenge in this evolution is the efficient and accurate conversion from the amplitude to phase domain for high-quality phase-only hologram(POH)generation.Existing computational models often struggle to address the inherent complexities of optical phenomena,compromising the conversion process.In this study,we present the cross-domain fusion network(CDFN),an architecture designed to tackle the complexities involved in POH generation.The CDFN employs a multi-stage(MS)mechanism to progressively learn the translation from amplitude to phase domain,complemented by the deep supervision(DS)strategy of middle features to enhance task-relevant feature learning from the initial stages.Additionally,we propose an infinite phase mapper(IPM),a phase-mapping function that circumvents the limitations of conventional activation functions and encapsulates the physical essence of holography.Through simulations,our proposed method successfully reconstructs high-quality 2K color images from the DIV2K dataset,achieving an average PSNR of 31.68 dB and SSIM of 0.944.Furthermore,we realize high-quality color image reconstruction in optical experiments.The experimental results highlight the computational intelligence and optical fidelity achieved by our proposed physics-aware cross-domain fusion.展开更多
To reduce the computing time of composite computer-generated holograms （CGHs） gen- eration based upon the angular projection algorithm for holographic three-dimensional （3D） display, a grid-based holographic displ...To reduce the computing time of composite computer-generated holograms （CGHs） gen- eration based upon the angular projection algorithm for holographic three-dimensional （3D） display, a grid-based holographic display （ GHD ） scheme was designed. The grid computing technology was applied to numerically process the different angular projections of an object in distributed-parallel manner to create the corresponding CGHs. The whole treatment of a projection was regarded as a job executed on the grid node machine. The number of jobs which were submitted to grid nodes, therefore, was equal to that of the projections of the object. A Condor-based grid testbed was constructed to verify the feasibility of the GHD scheme, and a graphical user interface （GUI） program and several service modules were developed for it. A 3D terrain model as an example was processed on the testbed. The result showed that the scheme was feasible and able to improve the execution elficiency greatly.展开更多
Incoherent digital holography has attracted significant attention due to its advantages in threedimensional(3D)imaging under low spatial coherence conditions,such as easy access to light sources and reduced speckle no...Incoherent digital holography has attracted significant attention due to its advantages in threedimensional(3D)imaging under low spatial coherence conditions,such as easy access to light sources and reduced speckle noise.However,interlayer crosstalk during the reconstruction process leads to a substantial reduction in reconstruction fidelity.Furthermore,existing deconvolutionand deep-learning-based reconstruction algorithms face limitations in terms of effectiveness and generalization.To address these challenges,we propose a compressive incoherent digital holography(CIDH)approach for 3D imaging.In CIDH,a point spread hologram sequence with a high signal-to-noise ratio is initially obtained using a customized computergenerated holography method for dual-channel forward data acquisition.For scene reconstruction,a compressed sensing-based two-step iterative shrinkage/thresholding algorithm is employed to achieve high-fidelity 3D scene retrieval.The combined optimization demonstrates exceptional performance in suppressing interlayer crosstalk and enhancing reconstruction fidelity.In simulations,crosstalk was effectively suppressed across 10 depth layers.In experiments,successful suppression was achieved for both a five-layer transmissive object and a two-layer reflective 3D object,resulting in significantly improved reconstruction accuracy.The proposed framework shows great potential for applications in various incoherent source-illuminated and fluorescent 3D imaging.展开更多
We propose a method of full-color,scan-free,and natural-light motion-picture holography for full-color 4D(3D+time)imaging and develop a portable natural-light motion-picture holographic camera that can be set on a mov...We propose a method of full-color,scan-free,and natural-light motion-picture holography for full-color 4D(3D+time)imaging and develop a portable natural-light motion-picture holographic camera that can be set on a movable table without any antivibration structure.Full-color motion-picture holograms of objects illuminated by natural light are obtained at the frame rate of an image sensor.We perform the single-shot natural-light full-color 3D imaging of objects illuminated by sunlight and the full-color 4D imaging of a moving object.This holographic camera is capable of full-color 4D imaging of objects ranging in size from the centimeter order to the 10-m order.This opens up a new stage in holographic imaging,overcoming the limitations of conventional holographic imaging despite the portability of this camera.展开更多
Streamer discharges that do not transition to a spark channel are now being widely investigated.One of these discharges is the apokamp discharge,in which streamers start from a diffuse spark channel having a curved sh...Streamer discharges that do not transition to a spark channel are now being widely investigated.One of these discharges is the apokamp discharge,in which streamers start from a diffuse spark channel having a curved shape at a high repetition rate of voltage pulse.In this work,to estimate the electron concentration in the plasma forming the apokamp a digital holographic laser scanning method is applied for the first time.The method is based on a comparison of the phases of two optical wavefronts,registered at different time instants in the form of digital holograms.The result of the phase comparison between the wavefronts is presented in the form of a numerically calculated map of the phase difference of the reconstructed wavefronts.A gas-discharge plasma is a phase(transparent)object,and the interference fringes are formed as a result of the change in the refractive index introduced by the plasma with respect to the original unperturbed medium.The obtained value of the refractive index allows estimation of the concentration of electrons in the spark channel plasma.It is shown that at as the voltage pulse repetition rate increases from 5 to 50 kHz the concentration of electrons in the plasma forming the apokamp decreases by an estimated four times.展开更多
For eliminating the zero-order image in digital holography, a new method using the differential of the hologram intensity instead of the hologram itself for numerical reconstruction is proposed. This method is based o...For eliminating the zero-order image in digital holography, a new method using the differential of the hologram intensity instead of the hologram itself for numerical reconstruction is proposed. This method is based on digital image processing. By analyzing the spatial spectrum of the off-axis digital hologram, it theoretically proves that the zero-order image can be effectively eliminated by differential before reconstruction. Then, the detected hologram is processed in the program with differential and reconstruction. Both the theoretical analysis and digital reconstruction results show that it can effectively eliminate the large bright spot in the center of the reconstructed image caused by the zero-order image, improve the image quality significantly, and render a better contrast of the reconstructed image. This method is very simple and convenient due to no superfluous optical elements and requiring only one time record.展开更多
The effects of chloride and thiosulfate ions on localized corrosion of alloy 800 are investigated through dynamical observation of the change in phase image of the diffusion layer during passive film breakdown using d...The effects of chloride and thiosulfate ions on localized corrosion of alloy 800 are investigated through dynamical observation of the change in phase image of the diffusion layer during passive film breakdown using digital holography. The results indicate that solution chemistry has a significant effect on film breakdown and diffusion layer. The phase distribution changes at different applied potentials show that in the process of film breakdown, dissolution of metal ions from pitting is not remarkable in chloride-only solution, whereas dissolution of metal ions is significantly high in thiosulfate and chloride solution. Thiosulfate has a combined effect with chloride ions in passive film degradation.展开更多
It is still a great challenge at present to combine the high rate capability of the electrochemical capacitor with the high electrochemical capacity feature of rechargeable battery in energy storage and transport devi...It is still a great challenge at present to combine the high rate capability of the electrochemical capacitor with the high electrochemical capacity feature of rechargeable battery in energy storage and transport devices. By studying the lithiation mechanism of Li_4Ti_5O_12 （LTO） using in-situ electron holography, we find that double charge layers are formed at the interface of the insulating Li_4Ti_5O_12 （Li_4） phase and the semiconducting Li_7Ti_5O_12 （Li_7） phase, and can greatly boost the lithiation kinetics. The electron wave phase of the LTO particle is found to gradually shrink with the interface movement, leaving a positive electric field from Li_7 to Li_4 phase. Once the capacitive interface charges are formed, the lithiation of the core/shell particle could be established within 10 s. The ultrafast kinetics is attributed to the built-in interface potential and the mixed Ti3＋/Ti4＋ sites at the interface that could be maximally lowering the thermodynamic barrier for Li ion migration.展开更多
In this paper, we propose an encryption scheme based on phase-shifting digital interferometry. According to the original system framework, we add a random amplitude mask and replace the Fourier transform by the Fresne...In this paper, we propose an encryption scheme based on phase-shifting digital interferometry. According to the original system framework, we add a random amplitude mask and replace the Fourier transform by the Fresnel transform. We develop a mathematical model and give a discrete formula based on the scheme, which makes it easy to implement the scheme in computer programming. The experimental results show that the improved system has a better performance in security than the original encryption method. Moreover, it demonstrates a good capability of anti-noise and anti-shear robustness.展开更多
基金supports from National Natural Science Foundation of China(Grant No.62205117,52275429)National Key Research and Development Program of China(Grant No.2021YFF0502700)+2 种基金Young Elite Scientists Sponsorship Program by CAST(Grant No.2022QNRC001)West Light Foundation of the Chinese Academy of Sciences(Grant No.xbzg-zdsys-202206)Hubei Natural Science Foundation Innovative Research Group Project(2024AFA025).
文摘The popularity of deep learning has boosted computer-generated holography(CGH)as a vibrant research field,particularly physics-driven unsupervised learning.Nevertheless,present unsupervised CGH models have not yet explored the potential of generating full-color 3D holograms through a unified framework.In this study,we propose a lightweight multiwavelength network model capable of high-fidelity and efficient full-color hologram generation in both 2D and 3D display,called IncepHoloRGB.The high-speed simultaneous generation of RGB holograms at 191 frames per second(FPS)is based on Inception sampling blocks and multi-wavelength propagation module integrated with depth-traced superimposition,achieving an average structural similarity(SSIM)of 0.88 and peak signal-to-noise ratio(PSNR)of 29.00 on the DIV2K test set in reconstruction.Full-color reconstruction of numerical simulations and optical experiments shows that IncepHoloRGB is versatile to diverse scenarios and can obtain authentic full-color holographic 3D display within a unified network model,paving the way for applications towards real-time dynamic naked-eye 3D display,virtual and augmented reality(VR/AR)systems.
基金We are grateful for financial supports from National Natural Science Foundation of China(62035003,61775117)China Postdoctoral Science Foundation(BX2021140)Tsinghua University Initiative Scientific Research Program(20193080075).
文摘Deep learning offers a novel opportunity to achieve both high-quality and high-speed computer-generated holography(CGH).Current data-driven deep learning algorithms face the challenge that the labeled training datasets limit the training performance and generalization.The model-driven deep learning introduces the diffraction model into the neural network.It eliminates the need for the labeled training dataset and has been extensively applied to hologram generation.However,the existing model-driven deep learning algorithms face the problem of insufficient constraints.In this study,we propose a model-driven neural network capable of high-fidelity 4K computer-generated hologram generation,called 4K Diffraction Model-driven Network(4K-DMDNet).The constraint of the reconstructed images in the frequency domain is strengthened.And a network structure that combines the residual method and sub-pixel convolution method is built,which effectively enhances the fitting ability of the network for inverse problems.The generalization of the 4K-DMDNet is demonstrated with binary,grayscale and 3D images.High-quality full-color optical reconstructions of the 4K holograms have been achieved at the wavelengths of 450 nm,520 nm,and 638 nm.
基金supported by the National Natural Science Foundation of China(Nos.62341124 and 62275113)the Yunnan Fundamental Research Projects(No.202201AT070030)。
文摘We propose a Phong shading approximation,which gives the amplitude of each point inside the triangle through linear interpolation within the framework of self-similarity segmentation and affine transformation in polygon-based computer-generated holography.Shading is important as it reflects the geometric properties of the objects.To accurately represent the geometric properties of objects in three-dimensional space,the method involves calculating the amplitude distribution on each triangle and maintaining a complete analytical framework,with the edges of the reconstructed polygons nearly unobservable.Numerical simulations and optical reconstructions demonstrate that the proposed method successfully addresses the issue of edge discontinuity on polygonal surfaces.
基金supported by the National Natural Science Foundation of China(No.62265006)the Jiangxi Provincial Department of Science and Technology(Nos.20212BCJL23050 and 20232BAB212017)+4 种基金the Foundation of Jiangxi Educational Commission(No.GJJ200623)the China Postdoctoral Science Foundation(No.2021M691344)the Jiangxi Provincial Postdoctoral Science Foundation of China(No.2020KY16)the Natural Science Foundation of Zhejiang Province(No.LQ22F050005)the Fundamental Research Funds for the Provincial Universities of Zhejiang(No.2022YW53)。
文摘In this paper,we propose,to our knowledge,a new complex-valued dense atrous neural network(CDANN)for phase-only hologram(POH)generation.The network architecture integrates a complex-valued partial convolution(C-PConv)module into the down-sampling stages of dual U-Net structures,enhancing computational efficiency through selective channelwise processing.To improve feature extraction,we introduce a novel complex-value dense atrous convolution(DAC)module,which employs four cascaded branches with multi-scale atrous convolutions to capture intricate features while maintaining spatial resolution.Additionally,we integrate a spatial pyramid pooling(SPP)module into the U-Net architecture to encode multi-scale contextual features derived from the DAC module.This hierarchical integration expands the U-Net's receptive field while facilitating cross-layer feature fusion.The proposed method achieves an average peak signal-to-noise ratio(PSNR)of 32.19 d B and an average structural similarity index measure(SSIM)of 0.892 within a running time of 24 ms,outperforming conventional approaches.Experiments confirm significant improvements in both reconstruction quality and computational efficiency,making the CDANN suitable for real-time holographic displays.
基金financial supports from the National Natural Science Foundation of China(Grant No.6227511362405124).
文摘We present a novel method for scale-invariant 3D face recognition by integrating computer-generated holography with the Mellin transform.This approach leverages the scale-invariance property of the Mellin transform to address challenges related to variations in 3D facial sizes during recognition.By applying the Mellin transform to computer-generated holograms and performing correlation between them,which,to the best of our knowledge,is being done for the first time,we have developed a robust recognition framework capable of managing significant scale variations without compromising recognition accuracy.Digital holograms of 3D faces are generated from a face database,and the Mellin transform is employed to enable robust recognition across scale factors ranging from 0.4 to 2.0.Within this range,the method achieves 100%recognition accuracy,as confirmed by both simulation-based and hybrid optical/digital experimental validations.Numerical calculations demonstrate that our method significantly enhances the accuracy and reliability of 3D face recognition,as evidenced by the sharp correlation peaks and higher peak-to-noise ratio(PNR)values than that of using conventional holograms without the Mellin transform.Additionally,the hybrid optical/digital joint transform correlation hardware further validates the method's effectiveness,demonstrating its capability to accurately identify and distinguish 3D faces at various scales.This work provides a promising solution for advanced biometric systems,especially for those which require 3D scale-invariant recognition.
基金National Natural Science Foundation of China(62305184)Basic and Applied Basic Research Foundation of Guangdong Province(2023A1515012932)+4 种基金Science,Technology and Innovation Commission of Shenzhen Municipality(WDZC20220818100259004)Research Grants Council of the Hong Kong Special Administrative Region,China(C5031-22G,CityU11300123,CityU11310522)Guangdong Provincial Department of Science and Technology(2020B1515120073)City University of Hong Kong(9610628)Research Grants Council of Hong Kong(ECS 27212822).
文摘The rapid advancement of computer-generated holography has bridged deep learning with traditional optical principles in recent years.However,a critical challenge in this evolution is the efficient and accurate conversion from the amplitude to phase domain for high-quality phase-only hologram(POH)generation.Existing computational models often struggle to address the inherent complexities of optical phenomena,compromising the conversion process.In this study,we present the cross-domain fusion network(CDFN),an architecture designed to tackle the complexities involved in POH generation.The CDFN employs a multi-stage(MS)mechanism to progressively learn the translation from amplitude to phase domain,complemented by the deep supervision(DS)strategy of middle features to enhance task-relevant feature learning from the initial stages.Additionally,we propose an infinite phase mapper(IPM),a phase-mapping function that circumvents the limitations of conventional activation functions and encapsulates the physical essence of holography.Through simulations,our proposed method successfully reconstructs high-quality 2K color images from the DIV2K dataset,achieving an average PSNR of 31.68 dB and SSIM of 0.944.Furthermore,we realize high-quality color image reconstruction in optical experiments.The experimental results highlight the computational intelligence and optical fidelity achieved by our proposed physics-aware cross-domain fusion.
文摘To reduce the computing time of composite computer-generated holograms （CGHs） gen- eration based upon the angular projection algorithm for holographic three-dimensional （3D） display, a grid-based holographic display （ GHD ） scheme was designed. The grid computing technology was applied to numerically process the different angular projections of an object in distributed-parallel manner to create the corresponding CGHs. The whole treatment of a projection was regarded as a job executed on the grid node machine. The number of jobs which were submitted to grid nodes, therefore, was equal to that of the projections of the object. A Condor-based grid testbed was constructed to verify the feasibility of the GHD scheme, and a graphical user interface （GUI） program and several service modules were developed for it. A 3D terrain model as an example was processed on the testbed. The result showed that the scheme was feasible and able to improve the execution elficiency greatly.
基金supported by the National Natural Science Foundation of China(Grant Nos.12325408,12274129,12374274,12274139,62175066,92150102,62475070,12474404,12471368,and 12304338)the Shanghai Municipal Education Commission(Grant No.2024AI01007).
文摘Incoherent digital holography has attracted significant attention due to its advantages in threedimensional(3D)imaging under low spatial coherence conditions,such as easy access to light sources and reduced speckle noise.However,interlayer crosstalk during the reconstruction process leads to a substantial reduction in reconstruction fidelity.Furthermore,existing deconvolutionand deep-learning-based reconstruction algorithms face limitations in terms of effectiveness and generalization.To address these challenges,we propose a compressive incoherent digital holography(CIDH)approach for 3D imaging.In CIDH,a point spread hologram sequence with a high signal-to-noise ratio is initially obtained using a customized computergenerated holography method for dual-channel forward data acquisition.For scene reconstruction,a compressed sensing-based two-step iterative shrinkage/thresholding algorithm is employed to achieve high-fidelity 3D scene retrieval.The combined optimization demonstrates exceptional performance in suppressing interlayer crosstalk and enhancing reconstruction fidelity.In simulations,crosstalk was effectively suppressed across 10 depth layers.In experiments,successful suppression was achieved for both a five-layer transmissive object and a two-layer reflective 3D object,resulting in significantly improved reconstruction accuracy.The proposed framework shows great potential for applications in various incoherent source-illuminated and fluorescent 3D imaging.
基金supported by the Japan Society for the Promotion of Science(JSPS)(Grant Nos.JP23K26579 and JP23K17364)the Mitsubishi Foundation(Grant No.202111007)+3 种基金Precursory Research for Embryonic Science and Technology(PRESTO)(Grant No.JPMJPR16P8)the Cooperative Research Program of“Network Joint Research Centre for Materials and Devices”(Grant Nos.20234030 and 20240411)the JST CREST(Grant No.JPMJCR23A1)the JST FOREST(Grant No.JPMJFR206K).
文摘We propose a method of full-color,scan-free,and natural-light motion-picture holography for full-color 4D(3D+time)imaging and develop a portable natural-light motion-picture holographic camera that can be set on a movable table without any antivibration structure.Full-color motion-picture holograms of objects illuminated by natural light are obtained at the frame rate of an image sensor.We perform the single-shot natural-light full-color 3D imaging of objects illuminated by sunlight and the full-color 4D imaging of a moving object.This holographic camera is capable of full-color 4D imaging of objects ranging in size from the centimeter order to the 10-m order.This opens up a new stage in holographic imaging,overcoming the limitations of conventional holographic imaging despite the portability of this camera.
基金performed in accordance with the support of the Russian Science Foundation(RSF)(No.23-79-00023)。
文摘Streamer discharges that do not transition to a spark channel are now being widely investigated.One of these discharges is the apokamp discharge,in which streamers start from a diffuse spark channel having a curved shape at a high repetition rate of voltage pulse.In this work,to estimate the electron concentration in the plasma forming the apokamp a digital holographic laser scanning method is applied for the first time.The method is based on a comparison of the phases of two optical wavefronts,registered at different time instants in the form of digital holograms.The result of the phase comparison between the wavefronts is presented in the form of a numerically calculated map of the phase difference of the reconstructed wavefronts.A gas-discharge plasma is a phase(transparent)object,and the interference fringes are formed as a result of the change in the refractive index introduced by the plasma with respect to the original unperturbed medium.The obtained value of the refractive index allows estimation of the concentration of electrons in the spark channel plasma.It is shown that at as the voltage pulse repetition rate increases from 5 to 50 kHz the concentration of electrons in the plasma forming the apokamp decreases by an estimated four times.
基金The Natural Science Foundation of Jiangsu Province (No.BK2006102)the National Natural Science Foundation of China(No.10772086)
文摘For eliminating the zero-order image in digital holography, a new method using the differential of the hologram intensity instead of the hologram itself for numerical reconstruction is proposed. This method is based on digital image processing. By analyzing the spatial spectrum of the off-axis digital hologram, it theoretically proves that the zero-order image can be effectively eliminated by differential before reconstruction. Then, the detected hologram is processed in the program with differential and reconstruction. Both the theoretical analysis and digital reconstruction results show that it can effectively eliminate the large bright spot in the center of the reconstructed image caused by the zero-order image, improve the image quality significantly, and render a better contrast of the reconstructed image. This method is very simple and convenient due to no superfluous optical elements and requiring only one time record.
基金supported by Natural Sciences and Engineering Research Council of Canada Discovery GrantNational Natural Science Foundation of China (No. 51371124)
文摘The effects of chloride and thiosulfate ions on localized corrosion of alloy 800 are investigated through dynamical observation of the change in phase image of the diffusion layer during passive film breakdown using digital holography. The results indicate that solution chemistry has a significant effect on film breakdown and diffusion layer. The phase distribution changes at different applied potentials show that in the process of film breakdown, dissolution of metal ions from pitting is not remarkable in chloride-only solution, whereas dissolution of metal ions is significantly high in thiosulfate and chloride solution. Thiosulfate has a combined effect with chloride ions in passive film degradation.
基金supported by the National Natural Science Foundation of China (Nos. 51501085, 11704019, 51522212 and 51421002)National Program on Key Basic Research Project (2014CB921002)the Strategic Priority Research Program of Chinese Academy of Sciences (No. XDB07030200)
文摘It is still a great challenge at present to combine the high rate capability of the electrochemical capacitor with the high electrochemical capacity feature of rechargeable battery in energy storage and transport devices. By studying the lithiation mechanism of Li_4Ti_5O_12 （LTO） using in-situ electron holography, we find that double charge layers are formed at the interface of the insulating Li_4Ti_5O_12 （Li_4） phase and the semiconducting Li_7Ti_5O_12 （Li_7） phase, and can greatly boost the lithiation kinetics. The electron wave phase of the LTO particle is found to gradually shrink with the interface movement, leaving a positive electric field from Li_7 to Li_4 phase. Once the capacitive interface charges are formed, the lithiation of the core/shell particle could be established within 10 s. The ultrafast kinetics is attributed to the built-in interface potential and the mixed Ti3＋/Ti4＋ sites at the interface that could be maximally lowering the thermodynamic barrier for Li ion migration.
基金supported by the National Basic Research Program of China(Grant No.2011CB302903)the National Natural Science Foundation of China(Grant Nos.61272084 and 61202004)the Key Project of Natural Science Research of Jiangsu University,China(Grant No.11KJA520002)
文摘In this paper, we propose an encryption scheme based on phase-shifting digital interferometry. According to the original system framework, we add a random amplitude mask and replace the Fourier transform by the Fresnel transform. We develop a mathematical model and give a discrete formula based on the scheme, which makes it easy to implement the scheme in computer programming. The experimental results show that the improved system has a better performance in security than the original encryption method. Moreover, it demonstrates a good capability of anti-noise and anti-shear robustness.
