Currently,some photorealistic computer graphics are very similar to photographic images.Photorealistic computer generated graphics can be forged as photographic images,causing serious security problems.The aim of this...Currently,some photorealistic computer graphics are very similar to photographic images.Photorealistic computer generated graphics can be forged as photographic images,causing serious security problems.The aim of this work is to use a deep neural network to detect photographic images(PI)versus computer generated graphics(CG).In existing approaches,image feature classification is computationally intensive and fails to achieve realtime analysis.This paper presents an effective approach to automatically identify PI and CG based on deep convolutional neural networks(DCNNs).Compared with some existing methods,the proposed method achieves real-time forensic tasks by deepening the network structure.Experimental results show that this approach can effectively identify PI and CG with average detection accuracy of 98%.展开更多
With the development of computer graphics,realistic computer graphics(CG)have become more and more common in our field of vision.This rendered image is invisible to the naked eye.How to effectively identify CG and nat...With the development of computer graphics,realistic computer graphics(CG)have become more and more common in our field of vision.This rendered image is invisible to the naked eye.How to effectively identify CG and natural images(NI)has been become a new issue in the field of digital forensics.In recent years,a series of deep learning network frameworks have shown great advantages in the field of images,which provides a good choice for us to solve this problem.This paper aims to track the latest developments and applications of deep learning in the field of CG and NI forensics in a timely manner.Firstly,it introduces the background of deep learning and the knowledge of convolutional neural networks.The purpose is to understand the basic model structure of deep learning applications in the image field,and then outlines the mainstream framework;secondly,it briefly introduces the application of deep learning in CG and NI forensics,and finally points out the problems of deep learning in this field and the prospects for the future.展开更多
Holographic displays have the promise to be the ultimate 3D display technology,able to account for all visual cues.Recent advances in photonics and electronics gave rise to high-resolution holographic display prototyp...Holographic displays have the promise to be the ultimate 3D display technology,able to account for all visual cues.Recent advances in photonics and electronics gave rise to high-resolution holographic display prototypes,indicating that they may become widely available in the near future.One major challenge in driving those display systems is computational:computer generated holography(CGH)consists of numerically simulating diffraction,which is very computationally intensive.Our goal in this paper is to give a broad overview of the state-of-the-art in CGH.We make a classification of modern CGH algorithms,we describe different algorithmic CGH acceleration techniques,discuss the latest dedicated hardware solutions and indicate how to evaluate the perceptual quality of CGH.We summarize our findings,discuss remaining challenges and make projections on the future of CGH.展开更多
Full-parallax light-field is captured by a small-scale 3D image scanning system and applied to holographic display. A vertical camera array is scanned horizontally to capture full-parallax imagery, and the vertical vi...Full-parallax light-field is captured by a small-scale 3D image scanning system and applied to holographic display. A vertical camera array is scanned horizontally to capture full-parallax imagery, and the vertical views between cameras are interpolated by depth image-based rendering technique. An improved technique for depth estimation reduces the estimation error and high-density light-field is obtained. The captured data is employed for the calculation of computer hologram using ray-sampling plane. This technique enables high-resolution display even in deep 3D scene although a hologram is calculated from ray information, and thus it makes use of the important advantage of holographic 3D display.展开更多
This focus issue Digital and Computer Generated Holography （DCH） combines the contributions from digital holography （DH） and computer-generated holography （CGH） into a single issue. We have classified the papers...This focus issue Digital and Computer Generated Holography （DCH） combines the contributions from digital holography （DH） and computer-generated holography （CGH） into a single issue. We have classified the papers into four topics： holographic microscopy, computer-generated holography,展开更多
Interferometric optical testing using computer-generated hologram （CGH） can give highly accurate measurement of aspheric surfaces has been proved. After the system is designed, a phase function is obtained according...Interferometric optical testing using computer-generated hologram （CGH） can give highly accurate measurement of aspheric surfaces has been proved. After the system is designed, a phase function is obtained according to the CGH＇s surface plane. For the requirement of accuracy, an optimization algorithm that transfers the phase function into a certain mask pattern file is presented in this letter, based on the relationship between the pattern error of CGH and the output wavefront accuracy. Then the writing machine is able to fabricate such a mask with this kind of file. With that mask, an improved procedure on fabrication of phase type CGH is also presented. Interferometrie test results of an aspherie surface show that the whole test system obtains the demanded accuracy.展开更多
Freeform surfaces are increasingly used in the design of compact optical systems. Interferometric null test with computer generated hologram （CGH）, which has been successfully used in highly accurate test of aspheri...Freeform surfaces are increasingly used in the design of compact optical systems. Interferometric null test with computer generated hologram （CGH）, which has been successfully used in highly accurate test of aspheric surfaces, is adopted to test the freeform surfaces. The best fitting sphere of the freeform surface under the test is firstly calculated to quickly estimate the possibility of null test. To decrease the maximum spatial frequency of the null CGH, the position of the CGH and the direction of optical axis are optimized. The estimated maximum spatial frequency of the CGH is 7.8% apart from the optimized one, which shows the validity of the best fitting sphere.展开更多
A multi-plane adaptive-additive algorithm is developed for optimizing computer-generated holograms for the reconstruction of traps in three-dimensional （3D） spaces. This algorithm overcomes the converging stagnation...A multi-plane adaptive-additive algorithm is developed for optimizing computer-generated holograms for the reconstruction of traps in three-dimensional （3D） spaces. This algorithm overcomes the converging stagnation problem of the traditional multi-plane Gerehber-Saxton algorithm and improves the diffraction efficiency of the holograms effectively, The optimized holograms are applied in a holographic optical tweezers （HOT） platform. Additionally, a computer program is developed and integrated into the HOT platform for the purpose of achieving the interactive control of traps. Experiments demonstrate that the manipulation of micro-particles into the 3D structure with optimized holograms can be carried out effectively on the HOT Dlatform.展开更多
Freeform optical surfaces （FOSs） will be the best elements in the design of compact optical systems in the future. However, it is extremely difficult to measure freeform surface with sufficient accuracy, which im- p...Freeform optical surfaces （FOSs） will be the best elements in the design of compact optical systems in the future. However, it is extremely difficult to measure freeform surface with sufficient accuracy, which im- pedes the development of the freeform surface. The design and fabrication of computer-generated hologram （CGH） , which has been successfully applied to the tests for aspheric surfaces, cannot be directly adopted to test FOSs due to their non-rotational asymmetry. A novel ray tracing planning method combined with successively optimizing even and odd power coefficients of phase polynomials in turn is proposed, which can successfully design a non-rotational asymmetry CGH for the tests of FOSs with an F-O lens. A new eight-step fabrication process is also presented aiming to solve the problem that the linewidth on the same circle of the CGH for testing freeform surface is not uniform. This problem cannot be solved in the original procedure of CGH fabrication. The test results of the step profiler show that the CGH fabricated in the new nrocedure meets the reauirements.展开更多
A three-dimensional （3D） object reconstruction technique that uses pure-phase computer-generated holograms （CGHs） and a phase-only spatial light modulator （SLM） is proposed. The full parallax CGHs are generated ...A three-dimensional （3D） object reconstruction technique that uses pure-phase computer-generated holograms （CGHs） and a phase-only spatial light modulator （SLM） is proposed. The full parallax CGHs are generated by the point source method and the wave-oriented method without paraxial approximation. Different from conventional CGHs, the pure-phase information on the hologram plane is loaded on the SLM to reconstruct the 3D diffusive objects without considering the reference wave. This technique is more efficient in its utilization of the space-bandwidth product of the SLMs. Numerical simulations and experiments are performed, and the results show that our proposed method can reconstruct 3D diffusive objects successfully.展开更多
Research demonstrates that a Fresnel hologram can be generated and simultaneously encrypted numerically based on a secret symmetric key formed by the maximal length sequence （M-sequence）. The method can be directly ...Research demonstrates that a Fresnel hologram can be generated and simultaneously encrypted numerically based on a secret symmetric key formed by the maximal length sequence （M-sequence）. The method can be directly extended to encrypt a video holographic clip in a frame-by-frame manner. However, given the limited combination of signals in the family of M-sequence, hacking the secret key through trial and error can be time consuming but not difficult. In this letter, we propose a method that is difficult to crack with brute force for enerypting a holographic video sequence. An M-sequence is first randomly assigned to enerypt each frame of the holographic video signal. Subsequently, the index of the selected M-sequence, which is necessary to decrypt the hologram~ is encrypted with the RSA algorithm before transmitting to the receiving end. At the receiving end, the decoder is provided with a private key to recover the index for each frame, and the corresDonding M-se（mence is used to decrvDt the encoded hologram.展开更多
Background Computer Generated Animations(CGA),when applied to three-dimensional(3D)city models(3DCM),can be used as powerful tools to support urban decision-making.This leads to a new paradigm,based on procedural mode...Background Computer Generated Animations(CGA),when applied to three-dimensional(3D)city models(3DCM),can be used as powerful tools to support urban decision-making.This leads to a new paradigm,based on procedural modeling,that allows the integration of known urban structures.Methods This paper introduces a new workflow for the development of high-quality approximations of urban models in a short time and enables facilities to be imported from other cities into a given city model,following specific generation rules.Results Thus,this workflow provides a very simple approach to observe,study,and simulate the implementation of models already developed in other cities,in a city where they are not yet adopted.Examples of these models include all types of mobility systems and urban infrastructure.Conclusions This allows us to perceive the environmental impact of certain decisions in the real world,as well as to carry out simple simulations to determine the changes that can occur in the flows of people,traffic,and other city activities.展开更多
Component object model technology is used to solve problems encountered when using three-dimentional （3D） objects to conduct computer-generated hologram （CGH） fast coding. MATLAB and C/C＋＋ are combined for relev...Component object model technology is used to solve problems encountered when using three-dimentional （3D） objects to conduct computer-generated hologram （CGH） fast coding. MATLAB and C/C＋＋ are combined for relevant programming under experimental conditions. The proposed method effectively reduces the time required for holographic encoding of large amounts of 3D object data. The CGH- accelerated computing method based on mixed programming is proven to be highly reliable and practical by testing the 3D data of different data volumes. According to the test results, the proposed method improves the efficiency of holographic encoding. The higher the data volume is, the more significantly the computation speed is improved.展开更多
A new encryption/decryption system for optical information security is proposed in this paper. We used an iterative Fourier transform algorithm to optimize the encrypted hologram as well as the decryption key as phase...A new encryption/decryption system for optical information security is proposed in this paper. We used an iterative Fourier transform algorithm to optimize the encrypted hologram as well as the decryption key as phase-only elements. The optical decryption was implemented by superimposing the encrypted hologram and the decryyption key in a simple optical setup. Numerical simulation and optical experiment have confirmed the proposed technique as a simple and easy implementation for optical decryption, demonstrating potential applications in optical information security verification.展开更多
Holography is an optical technique that records and reconstructs the light wavefront to generate desired images,emerging as a promising candidate for various display applications.The development of holography has been...Holography is an optical technique that records and reconstructs the light wavefront to generate desired images,emerging as a promising candidate for various display applications.The development of holography has been closely associated with computer-generated holography,in which the discretized phase and amplitude distributions of electromagnetic waves are computationally calculated and physically implemented using optical devices such as spatial light modulators and diffractive optical elements.In parallel,a variety of iterative phase retrieval algorithms,most notably the Gerchberg–Saxton(GS)algorithm,have also been studied to improve the fidelity and accuracy of the hologram reconstruction.1,2 Despite these advances,conventional implementations suffer from intrinsic limitations such as undesired higher-order diffraction,low spatial resolution,restricted viewing angles,and system bulkiness.展开更多
This Letter describes an approach to encode complex-amplitude light waves with spatiotemporal double-phase holograms(DPHs) for overcoming the limit of the space-bandwidth product(SBP) delivered by existing methods. To...This Letter describes an approach to encode complex-amplitude light waves with spatiotemporal double-phase holograms(DPHs) for overcoming the limit of the space-bandwidth product(SBP) delivered by existing methods. To construct DPHs, two spatially macro-pixel encoded phase components are employed in the SBP-preserved resampling of complex holograms. Four generated sub-DPHs are displayed sequentially in time for high-quality holographic image reconstruction without reducing the image size or discarding any image terms when the DPHs are interweaved. The reconstructed holographic images contain more details and less speckle noise, with their signal-to-noise ratio and structure similarity index being improved by 14.64% and 78.79%,respectively.展开更多
A novel speckle reduction technique for digital holography is proposed. Multiple off-axis holograms are recorded using a circularly polarized illumination beam and a rotating linearly polarized reference beam. The spe...A novel speckle reduction technique for digital holography is proposed. Multiple off-axis holograms are recorded using a circularly polarized illumination beam and a rotating linearly polarized reference beam. The speckle noise in the reconstructed images is suppressed by averaging these fields. We demonstrate the effectiveness of this technique experimentally and conduct additional statistical evaluation.展开更多
Improving the intelligence of virtual entities is an important issue in Computer Generated Forces （CGFs） construction. Some traditional approaches try to achieve this by specifying how entities should react to prede...Improving the intelligence of virtual entities is an important issue in Computer Generated Forces （CGFs） construction. Some traditional approaches try to achieve this by specifying how entities should react to predefined conditions, which is not suitable for complex and dynamic environments. This paper aims to apply Monte Carlo Tree Search （MCTS） for the behavior modeling of CGF commander. By look-ahead reasoning, the model generates adaptive decisions to direct the whole troops to fight. Our main work is to formulate the tree model through the state and action abstraction, and extend its expansion process to handle simultaneous and durative moves. We also employ Hierarchical Task Network （HTN） planning to guide the search, thus enhancing the search efficiency. The final implementation is tested in an infantry combat simulation where a company commander needs to control three platoons to assault and clear enemies within defined areas. Comparative results from a series of experiments demonstrate that the HTN guided MCTS commander can outperform other commanders following fixed strategies.展开更多
An approach, based on the correlation between the intensity distribution of object wave of the directly recorded by charge-coupled device and the one reconstructed by computer, is proposed to evaluate the quality of t...An approach, based on the correlation between the intensity distribution of object wave of the directly recorded by charge-coupled device and the one reconstructed by computer, is proposed to evaluate the quality of the phase reconstruction in light emitting diode （LED） based phase-shifting digital holography. This method enables us to find out the optimal reconstructed phase even though the peak wavelength of LED, which is used for calibrating the phase-shifter, is inconvenient to be determined and tends to shift with temperature and driving current. The feasibility of this method is verified by both computer simulations and experiments.展开更多
An improved polarization recording approach to reduce speckle noise in digital holography is proposed. Multiple off-axis holograms are obtained by rotating the linear polarization state of both illumination and refere...An improved polarization recording approach to reduce speckle noise in digital holography is proposed. Multiple off-axis holograms are obtained by rotating the linear polarization state of both illumination and reference wave simultaneously. By averaging the intensity fields, the speckle noise in the reconstructed images is well suppressed. Statistical evaluation of the experimental results shows the effectiveness and improvement of the proposed method.展开更多
基金This work is supported,in part,by the National Natural Science Foundation of China under grant numbers U1536206,U1405254,61772283,61602253,61672294,61502242In part,by the Jiangsu Basic Research Programs-Natural Science Foundation under grant numbers BK20150925 and BK20151530+1 种基金In part,by the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD)fundIn part,by the Collaborative Innovation Center of Atmospheric Environment and Equipment Technology(CICAEET)fund,China.
文摘Currently,some photorealistic computer graphics are very similar to photographic images.Photorealistic computer generated graphics can be forged as photographic images,causing serious security problems.The aim of this work is to use a deep neural network to detect photographic images(PI)versus computer generated graphics(CG).In existing approaches,image feature classification is computationally intensive and fails to achieve realtime analysis.This paper presents an effective approach to automatically identify PI and CG based on deep convolutional neural networks(DCNNs).Compared with some existing methods,the proposed method achieves real-time forensic tasks by deepening the network structure.Experimental results show that this approach can effectively identify PI and CG with average detection accuracy of 98%.
基金supported by National Natural Science Foundation of China(62072250).
文摘With the development of computer graphics,realistic computer graphics(CG)have become more and more common in our field of vision.This rendered image is invisible to the naked eye.How to effectively identify CG and natural images(NI)has been become a new issue in the field of digital forensics.In recent years,a series of deep learning network frameworks have shown great advantages in the field of images,which provides a good choice for us to solve this problem.This paper aims to track the latest developments and applications of deep learning in the field of CG and NI forensics in a timely manner.Firstly,it introduces the background of deep learning and the knowledge of convolutional neural networks.The purpose is to understand the basic model structure of deep learning applications in the image field,and then outlines the mainstream framework;secondly,it briefly introduces the application of deep learning in CG and NI forensics,and finally points out the problems of deep learning in this field and the prospects for the future.
基金This research was funded by the Research Foundation-Flanders(FWO),Junior postdoctoral fellowship(12ZQ220N),the joint JSPS-FWO scientific cooperation program(VS07820N)the Japan Society for the Promotion of Science(19H04132 and JPJSBP120202302)。
文摘Holographic displays have the promise to be the ultimate 3D display technology,able to account for all visual cues.Recent advances in photonics and electronics gave rise to high-resolution holographic display prototypes,indicating that they may become widely available in the near future.One major challenge in driving those display systems is computational:computer generated holography(CGH)consists of numerically simulating diffraction,which is very computationally intensive.Our goal in this paper is to give a broad overview of the state-of-the-art in CGH.We make a classification of modern CGH algorithms,we describe different algorithmic CGH acceleration techniques,discuss the latest dedicated hardware solutions and indicate how to evaluate the perceptual quality of CGH.We summarize our findings,discuss remaining challenges and make projections on the future of CGH.
基金partly supported by the JSPS Grant-in-Aid for Scientific Research #17300032
文摘Full-parallax light-field is captured by a small-scale 3D image scanning system and applied to holographic display. A vertical camera array is scanned horizontally to capture full-parallax imagery, and the vertical views between cameras are interpolated by depth image-based rendering technique. An improved technique for depth estimation reduces the estimation error and high-density light-field is obtained. The captured data is employed for the calculation of computer hologram using ray-sampling plane. This technique enables high-resolution display even in deep 3D scene although a hologram is calculated from ray information, and thus it makes use of the important advantage of holographic 3D display.
文摘This focus issue Digital and Computer Generated Holography （DCH） combines the contributions from digital holography （DH） and computer-generated holography （CGH） into a single issue. We have classified the papers into four topics： holographic microscopy, computer-generated holography,
文摘Interferometric optical testing using computer-generated hologram （CGH） can give highly accurate measurement of aspheric surfaces has been proved. After the system is designed, a phase function is obtained according to the CGH＇s surface plane. For the requirement of accuracy, an optimization algorithm that transfers the phase function into a certain mask pattern file is presented in this letter, based on the relationship between the pattern error of CGH and the output wavefront accuracy. Then the writing machine is able to fabricate such a mask with this kind of file. With that mask, an improved procedure on fabrication of phase type CGH is also presented. Interferometrie test results of an aspherie surface show that the whole test system obtains the demanded accuracy.
文摘Freeform surfaces are increasingly used in the design of compact optical systems. Interferometric null test with computer generated hologram （CGH）, which has been successfully used in highly accurate test of aspheric surfaces, is adopted to test the freeform surfaces. The best fitting sphere of the freeform surface under the test is firstly calculated to quickly estimate the possibility of null test. To decrease the maximum spatial frequency of the null CGH, the position of the CGH and the direction of optical axis are optimized. The estimated maximum spatial frequency of the CGH is 7.8% apart from the optimized one, which shows the validity of the best fitting sphere.
基金supported by the National Natural Science Foundation of China under Grant Nos. 50975271and 91023049
文摘A multi-plane adaptive-additive algorithm is developed for optimizing computer-generated holograms for the reconstruction of traps in three-dimensional （3D） spaces. This algorithm overcomes the converging stagnation problem of the traditional multi-plane Gerehber-Saxton algorithm and improves the diffraction efficiency of the holograms effectively, The optimized holograms are applied in a holographic optical tweezers （HOT） platform. Additionally, a computer program is developed and integrated into the HOT platform for the purpose of achieving the interactive control of traps. Experiments demonstrate that the manipulation of micro-particles into the 3D structure with optimized holograms can be carried out effectively on the HOT Dlatform.
基金supported by the Natural Science Foundation of Jiangsu Province of China under Grant No.BK2012802
文摘Freeform optical surfaces （FOSs） will be the best elements in the design of compact optical systems in the future. However, it is extremely difficult to measure freeform surface with sufficient accuracy, which im- pedes the development of the freeform surface. The design and fabrication of computer-generated hologram （CGH） , which has been successfully applied to the tests for aspheric surfaces, cannot be directly adopted to test FOSs due to their non-rotational asymmetry. A novel ray tracing planning method combined with successively optimizing even and odd power coefficients of phase polynomials in turn is proposed, which can successfully design a non-rotational asymmetry CGH for the tests of FOSs with an F-O lens. A new eight-step fabrication process is also presented aiming to solve the problem that the linewidth on the same circle of the CGH for testing freeform surface is not uniform. This problem cannot be solved in the original procedure of CGH fabrication. The test results of the step profiler show that the CGH fabricated in the new nrocedure meets the reauirements.
基金supported by the Innovation Team Development Program of the Ministry of Education of China (No IRT0606)the National Basic Research Program of China (No 2006CB302901)
文摘A three-dimensional （3D） object reconstruction technique that uses pure-phase computer-generated holograms （CGHs） and a phase-only spatial light modulator （SLM） is proposed. The full parallax CGHs are generated by the point source method and the wave-oriented method without paraxial approximation. Different from conventional CGHs, the pure-phase information on the hologram plane is loaded on the SLM to reconstruct the 3D diffusive objects without considering the reference wave. This technique is more efficient in its utilization of the space-bandwidth product of the SLMs. Numerical simulations and experiments are performed, and the results show that our proposed method can reconstruct 3D diffusive objects successfully.
文摘Research demonstrates that a Fresnel hologram can be generated and simultaneously encrypted numerically based on a secret symmetric key formed by the maximal length sequence （M-sequence）. The method can be directly extended to encrypt a video holographic clip in a frame-by-frame manner. However, given the limited combination of signals in the family of M-sequence, hacking the secret key through trial and error can be time consuming but not difficult. In this letter, we propose a method that is difficult to crack with brute force for enerypting a holographic video sequence. An M-sequence is first randomly assigned to enerypt each frame of the holographic video signal. Subsequently, the index of the selected M-sequence, which is necessary to decrypt the hologram~ is encrypted with the RSA algorithm before transmitting to the receiving end. At the receiving end, the decoder is provided with a private key to recover the index for each frame, and the corresDonding M-se（mence is used to decrvDt the encoded hologram.
基金project"Crowdsourcing Optimized Wireless Sensor Network Deployment(CRoWD)"of Dirección General de Investigaciones of Universidad Santiago de Cali under grant No.613-621119-852.
文摘Background Computer Generated Animations(CGA),when applied to three-dimensional(3D)city models(3DCM),can be used as powerful tools to support urban decision-making.This leads to a new paradigm,based on procedural modeling,that allows the integration of known urban structures.Methods This paper introduces a new workflow for the development of high-quality approximations of urban models in a short time and enables facilities to be imported from other cities into a given city model,following specific generation rules.Results Thus,this workflow provides a very simple approach to observe,study,and simulate the implementation of models already developed in other cities,in a city where they are not yet adopted.Examples of these models include all types of mobility systems and urban infrastructure.Conclusions This allows us to perceive the environmental impact of certain decisions in the real world,as well as to carry out simple simulations to determine the changes that can occur in the flows of people,traffic,and other city activities.
基金supported by the National Natural Science Foundation of China(Nos.61007061 and 11172116)the Scientific Research Foundation for the Returned Overseas Chinese Scholars of the State Education Ministry(No.KKQA201307001)
文摘Component object model technology is used to solve problems encountered when using three-dimentional （3D） objects to conduct computer-generated hologram （CGH） fast coding. MATLAB and C/C＋＋ are combined for relevant programming under experimental conditions. The proposed method effectively reduces the time required for holographic encoding of large amounts of 3D object data. The CGH- accelerated computing method based on mixed programming is proven to be highly reliable and practical by testing the 3D data of different data volumes. According to the test results, the proposed method improves the efficiency of holographic encoding. The higher the data volume is, the more significantly the computation speed is improved.
文摘A new encryption/decryption system for optical information security is proposed in this paper. We used an iterative Fourier transform algorithm to optimize the encrypted hologram as well as the decryption key as phase-only elements. The optical decryption was implemented by superimposing the encrypted hologram and the decryyption key in a simple optical setup. Numerical simulation and optical experiment have confirmed the proposed technique as a simple and easy implementation for optical decryption, demonstrating potential applications in optical information security verification.
基金financially supported by the POSCO-POSTECH-RIST Convergence Research Center program funded by POSCOthe National Research Foundation grant(Grant No.RS-2022-NR067559)funded by the Ministry of Science and ICT(MSIT)of the Korean government.
文摘Holography is an optical technique that records and reconstructs the light wavefront to generate desired images,emerging as a promising candidate for various display applications.The development of holography has been closely associated with computer-generated holography,in which the discretized phase and amplitude distributions of electromagnetic waves are computationally calculated and physically implemented using optical devices such as spatial light modulators and diffractive optical elements.In parallel,a variety of iterative phase retrieval algorithms,most notably the Gerchberg–Saxton(GS)algorithm,have also been studied to improve the fidelity and accuracy of the hologram reconstruction.1,2 Despite these advances,conventional implementations suffer from intrinsic limitations such as undesired higher-order diffraction,low spatial resolution,restricted viewing angles,and system bulkiness.
基金supported by the National Natural Science Foundation of China (NSFC)(Nos. 61827825 and 61775117)Tsinghua University Initiative Scientific Research Program (No. 20193080075)the Cambridge Tsinghua Joint Research Initiative
文摘This Letter describes an approach to encode complex-amplitude light waves with spatiotemporal double-phase holograms(DPHs) for overcoming the limit of the space-bandwidth product(SBP) delivered by existing methods. To construct DPHs, two spatially macro-pixel encoded phase components are employed in the SBP-preserved resampling of complex holograms. Four generated sub-DPHs are displayed sequentially in time for high-quality holographic image reconstruction without reducing the image size or discarding any image terms when the DPHs are interweaved. The reconstructed holographic images contain more details and less speckle noise, with their signal-to-noise ratio and structure similarity index being improved by 14.64% and 78.79%,respectively.
基金supported by the Precision Opto-Mechatronics Technology,Key Laboratory the Ministry of Education of China,the National "863" Project of China (No. 2007AA12Z131)the Science Foundation of Education Commission of Beijing(No. KZ200910005001)
文摘A novel speckle reduction technique for digital holography is proposed. Multiple off-axis holograms are recorded using a circularly polarized illumination beam and a rotating linearly polarized reference beam. The speckle noise in the reconstructed images is suppressed by averaging these fields. We demonstrate the effectiveness of this technique experimentally and conduct additional statistical evaluation.
文摘Improving the intelligence of virtual entities is an important issue in Computer Generated Forces （CGFs） construction. Some traditional approaches try to achieve this by specifying how entities should react to predefined conditions, which is not suitable for complex and dynamic environments. This paper aims to apply Monte Carlo Tree Search （MCTS） for the behavior modeling of CGF commander. By look-ahead reasoning, the model generates adaptive decisions to direct the whole troops to fight. Our main work is to formulate the tree model through the state and action abstraction, and extend its expansion process to handle simultaneous and durative moves. We also employ Hierarchical Task Network （HTN） planning to guide the search, thus enhancing the search efficiency. The final implementation is tested in an infantry combat simulation where a company commander needs to control three platoons to assault and clear enemies within defined areas. Comparative results from a series of experiments demonstrate that the HTN guided MCTS commander can outperform other commanders following fixed strategies.
基金supported by the National Natural Sci-ence Foundation of China under Grant No 60677019
文摘An approach, based on the correlation between the intensity distribution of object wave of the directly recorded by charge-coupled device and the one reconstructed by computer, is proposed to evaluate the quality of the phase reconstruction in light emitting diode （LED） based phase-shifting digital holography. This method enables us to find out the optimal reconstructed phase even though the peak wavelength of LED, which is used for calibrating the phase-shifter, is inconvenient to be determined and tends to shift with temperature and driving current. The feasibility of this method is verified by both computer simulations and experiments.
基金supported by the National Natural Science Foundation of China (No. 31000387)the Fundamental Research Funds for the Central Universities,China (No. YWF-10-02-087)the Science Foundation of Education Commission of Beijing, China (No.KZ200910005001)
文摘An improved polarization recording approach to reduce speckle noise in digital holography is proposed. Multiple off-axis holograms are obtained by rotating the linear polarization state of both illumination and reference wave simultaneously. By averaging the intensity fields, the speckle noise in the reconstructed images is well suppressed. Statistical evaluation of the experimental results shows the effectiveness and improvement of the proposed method.
