- 标题
- 摘要
- 关键词
- 实验方案
- 产品
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[Laser Institute of America ICALEO?? 2017: 36th International Congress on Applications of Lasers & Electro-Optics - Atlanta, Georgia, USA (October 22a??26, 2017)] International Congress on Applications of Lasers & Electro-Optics - Aberration control by high NA focusing in transparent media
摘要： High numerical aperture (NA) focusing of light in transparent media is important in microscopy, various techniques of optical data storage and laser microprocessing. By high NA focusing through a flat bounding surface of a medium there appears positive spherical aberration reducing energy concentration and lowering physical resolution. The deeper is focusing and higher NA, the stronger is aberration and light scattering. By laser material processing there appears uncontrolled energy distribution along optical axis that makes inherently complex physical processes of laser radiation interaction with material even more complex and less predictable. To control the spherical aberration induced by internal high NA focusing it is suggested to apply specially designed aplanatic objective of patent pending optical design. The objective provides full compensation of spherical aberration for diffraction limited on-axis and off-axis high NA focusing at wide range of depths, for example from 0 to 2 mm in fused silica for NA0.8 without immersion. By setting movable components in optimum for particular depth reciprocal positions it is possible to provide not only full aberration compensation but also under- and over-compensation, thus providing control of energy distribution along optical axis at arbitrary depth and achieving special material processing effects. The paper describes design features of this optical approach as well as comparative results of spot size calculations and corresponding microphotographs of processed areas in fused silica by laser radiation focusing at various depths using NA0.8 objectives with and without compensation of aberrations.
关键词： aplanatic objective,spherical aberration,laser microprocessing,high numerical aperture,transparent media
更新于2025-09-19 17:13:59
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[IEEE 2019 24th Microoptics Conference (MOC) - Toyama, Japan (2019.11.17-2019.11.20)] 2019 24th Microoptics Conference (MOC) - Quantum dot-based optically pumped VCSELs with high-contrast periodic gratings
摘要： With meter-resolution images delivered by modern synthetic aperture radar (SAR) satellites satellites like TerraSAR-X and TanDEM-X, it is now possible to map urban areas from space in very high level of detail using advanced interferometric techniques such as persistent scatterer interferometry and tomographic SAR inversion (TomoSAR), whereas these multi-pass techniques are based on a great number of images. We aim at precise TomoSAR reconstruction while signi?cantly reducing the required number of images by incorporating building a priori knowledge to the estimation. In the paper, we propose a novel work?ow that marries the freely available geographic information systems (GIS) data (i.e., 2-D building footprints) and the joint sparsity concept for TomoSAR inversion. Experiments on bistatic TanDEM-X data stacks demonstrate the great potential of the proposed approach, e.g., highly accurate tomographic reconstruction is achieved using six interferograms only.
关键词： Compressive sensing,TanDEM-X,SAR tomography,joint sparsity,GIS,synthetic aperture radar
更新于2025-09-19 17:13:59
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[IEEE 2019 IEEE Conference on Power Electronics and Renewable Energy (CPERE) - Aswan City, Egypt (2019.10.23-2019.10.25)] 2019 IEEE Conference on Power Electronics and Renewable Energy (CPERE) - Integrated Single Output Sensor Distributed MPPT for Photovoltaic Systems: A Novel Per-Cell Approach
摘要： The temporal variations (diurnal and annual) in arboreal (εTree) and bare soil (εSoil) dielectric constants and their correlation with precipitation were examined for several trees in Japan. A significant (1 σ (standard deviation) and 2 σ) εTree increase is observed after rainfall at 89.8% and 90.5% probability. However, rainfall does not always induce significant εTree increases. Rainfall of more than 5 mm/day can induce 1 σ εTree increase at a 59.6% probability. In order to examine whether the increase in εTree affects the L-band σ0 variation in a forest, the four-year temporal variation of the L-band backscattering coefficient (σ0) was estimated from observations by the Advanced Land Observing Satellite Phased Array type L-band Synthetic Aperture Radar. Observed maximum absolute deviations from the mean over the forest area were 1.0 and 1.2 dB for σ0 HV, respectively, and 4.0 and 3.0 dB over open land. σ0 and σ0 and rainfall correlations show that εTree and σ0 Forest are proportional to precipitation integrated over seven or eight days; εSoil and σ0 Open land are proportional to precipitation integrated over three days. This finding indicates that εTree variations influence σ0 Forest areas. A stronger correlation between σ0 HV and precipitation is observed in several sites with low σ0 HV, where less biomass is expected, and several sites with high σ0 HV, where more biomass is expected. A weaker correlation between σ0 HV and precipitation is observed for several sites with high σ0 HV. These differences may be explained by the different contributions of double bounce scattering and potential transpiration, which is a measure of the ability of the atmosphere to remove water from the surface through the processes of transpiration. The two other results were as follows: 1) The functional relation between aboveground biomass and σ0 showed dependence on precipitation data, this being an effect connected with seasonal changes of the εTree. This experiment reinforces the fact that the dry season is preferable for retrieval of woody biomass from inversion of the functional dependence of SAR backscatter and for avoiding the influence of rainfall. 2) The complex dielectric constant for a tree trunk, which is measured between 0.2 and 6 GHz, indicates that free water is dominant in the measured tree.
关键词： forest,temporal variation,dielectric constant,Biomass,Phased Array type L-band Synthetic Aperture Radar (PALSAR)
更新于2025-09-19 17:13:59
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[IEEE 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Chicago, IL, USA (2019.6.16-2019.6.21)] 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Design Advancement of an Indoor Soil Deposition Chamber: A Road to Standardization
摘要： Change detection using synthetic aperture radar (SAR) data is useful in emergency situations and unfavorable weather conditions. In this letter, change detection using multitemporal polarimetric Uninhabited Aerial Vehicle SAR data is investigated in an urban environment. The most robust polarimetric parameters are determined, and change detection techniques using a maximum likelihood ratio and a hyperbolic tangent model function are applied to the selected parameter. The model function was introduced to quantify the change characteristics and to rule out seasonal changes or those related to mobile features, and thus to only detect durable and permanent changes in urban environments. A comparison of results with historical Google Earth images showed a good level of agreement. Fitting of the hyperbolic tangent function to the multitemporal polarimetric parameters significantly reduces the false detection rate and indicates whether a building was constructed or destroyed, as well as when the detected changes occurred.
关键词： polarimetry,Change detection,multitemporal,urban,Uninhabited Aerial Vehicle Synthetic Aperture Radar (UAVSAR)
更新于2025-09-19 17:13:59
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Dual-Core Photonic Crystal Fiber-Based Plasmonic RI Sensor in the Visible to Near-IR Operating Band
摘要： With the steadily increasing spatial resolution of synthetic aperture radar images, the need for a consistent but locally adaptive image enhancement rises considerably. Numerous studies already showed that adaptive multilooking, able to adjust the degree of smoothing locally to the size of the targets, is superior to uniform multilooking. This study introduces a novel approach of multiscale and multidirectional multilooking based on intensity images exclusively but applicable to an arbitrary number of image layers. A set of 2-D circular and elliptical filter kernels in different scales and orientations (named Schmittlets) is derived from hyperbolic functions. The original intensity image is transformed into the Schmittlet coefficient domain where each coefficient measures the existence of Schmittlet-like structures in the image. By estimating their significance via the perturbation-based noise model, the best-fitting Schmittlets are selected for image reconstruction. On the one hand, the index image indicating the locally best-fitting Schmittlets is utilized to consistently enhance further image layers, e.g., multipolarized, multitemporal, or multifrequency layers, and on the other hand, it provides an optimal description of spatial patterns valuable for further image analysis. The final validation proves the advantages of the Schmittlets over six contemporary speckle reduction techniques in six different categories (preservation of the mean intensity, equivalent number of looks, and preservation of edges and local curvature both in strength and in direction) by the help of four test sites on three resolution levels. The additional value of the Schmittlet index layer for automated image interpretation, although obvious, still is subject to further studies.
关键词： Adaptive filters,digital filters,image analysis,image reconstruction,image representations,image edge analysis,image enhancement,synthetic aperture radar (SAR)
更新于2025-09-19 17:13:59
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[IEEE 2019 IEEE 5th International Conference Actual Problems of Unmanned Aerial Vehicles Developments (APUAVD) - Kiev, Ukraine (2019.10.22-2019.10.24)] 2019 IEEE 5th International Conference Actual Problems of Unmanned Aerial Vehicles Developments (APUAVD) - Laser Opto-Electronic Airspace Monitoring System in the Visible and Infrared Ranges
摘要： A novel design concept of multimode ?ltering antenna, which is realized by integrating a multimode resonator and an antenna, has been applied to the design of dual-polarized antenna arrays for achieving a compact size and high performance in terms of broad bandwidth, high-frequency selectivity and out-of-band rejection. To verify the concept, a 2 × 2 array at C-band is designed and fabricated. The stub-loaded resonator (SLR) is employed as the feed of the antenna. The resonant characteristics of SLR and patch as well as the coupling between them are presented. The method of designing the integrated resonator-patch module is explained. This integrated design not only removes the need for separated ?lters and traditional 50-Ω interfaces but also improves the frequency response of the module. A comparison with the traditional patch array has been made, showing that the proposed design has a more compact size, wider bandwidth, better frequency selectivity, and out-of-band rejection. Such low-pro?le light weight broadband dual-polarized arrays are useful for space-borne synthetic aperture radar (SAR) and wireless communication applications. The simulated and measured results agree well, demonstrating a good performance in terms of impedance bandwidth, frequency selectivity, isolation, radiation pattern, and antenna gain.
关键词： Antenna array,broadband,?ltering antenna,dual-polarization,synthetic aperture radar (SAR),stub-loaded resonator (SLR)
更新于2025-09-19 17:13:59
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[IEEE 2019 8th International Conference on Renewable Energy Research and Applications (ICRERA) - Brasov, Romania (2019.11.3-2019.11.6)] 2019 8th International Conference on Renewable Energy Research and Applications (ICRERA) - Smoothing Methodologies for Photovoltaic Power Fluctuations
摘要： A novel design concept of multimode ?ltering antenna, which is realized by integrating a multimode resonator and an antenna, has been applied to the design of dual-polarized antenna arrays for achieving a compact size and high performance in terms of broad bandwidth, high-frequency selectivity and out-of-band rejection. To verify the concept, a 2 × 2 array at C-band is designed and fabricated. The stub-loaded resonator (SLR) is employed as the feed of the antenna. The resonant characteristics of SLR and patch as well as the coupling between them are presented. The method of designing the integrated resonator-patch module is explained. This integrated design not only removes the need for separated ?lters and traditional 50-Ω interfaces but also improves the frequency response of the module. A comparison with the traditional patch array has been made, showing that the proposed design has a more compact size, wider bandwidth, better frequency selectivity, and out-of-band rejection. Such low-pro?le light weight broadband dual-polarized arrays are useful for space-borne synthetic aperture radar (SAR) and wireless communication applications. The simulated and measured results agree well, demonstrating a good performance in terms of impedance bandwidth, frequency selectivity, isolation, radiation pattern, and antenna gain.
关键词： Antenna array,broadband,?ltering antenna,dual-polarization,synthetic aperture radar (SAR),stub-loaded resonator (SLR)
更新于2025-09-19 17:13:59
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[IEEE 2019 International Conference on Microwave and Millimeter Wave Technology (ICMMT) - Guangzhou, China (2019.5.19-2019.5.22)] 2019 International Conference on Microwave and Millimeter Wave Technology (ICMMT) - Design of Dynamically Tunable Broadband Polarization Converter in Terahertz Frequency Based on Graphene Strips
摘要： The phenomenon of soil salinization in semi-arid regions is getting amplified and accentuated by both anthropogenic practices and climate change. Land salinization mapping and monitoring using conventional strategies are insufficient and difficult. Our work aims to study the potential of synthetic aperture radar (SAR) for mapping and monitoring of the spatio-temporal dynamics of soil salinity using interferometry. Our contribution in this paper consists of a statistical relationship that we establish between field salinity measurement and InSAR coherence based on an empirical analysis. For experimental validation, two sites were selected: 1) the region of Mahdia (central Tunisia) and 2) the plain of Tadla (central Morocco). Both sites underwent three ground campaigns simultaneously with three Radarsat-2 SAR image acquisitions. The results show that it is possible to estimate the temporal change in soil electrical conductivity (EC) from SAR images through the InSAR technique. It has been shown that the radar signal is more sensitive to soil salinity in HH polarization using a small incidence angle. However, for the HV polarization, a large angle of incidence is more suitable. This is, under considering the minimal influence of roughness and moisture surfaces, for a given InSAR coherence.
关键词： interferometric synthetic aperture radar (InSAR) coherence,polarimetric synthetic aperture radar (SAR),soil salinity,Electrical conductivity (EC)
更新于2025-09-16 10:30:52
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[IEEE 2019 TEQIP III Sponsored International Conference on Microwave Integrated Circuits, Photonics and Wireless Networks (IMICPW) - Tiruchirappalli, India (2019.5.22-2019.5.24)] 2019 TEQIP III Sponsored International Conference on Microwave Integrated Circuits, Photonics and Wireless Networks (IMICPW) - Design of Broadband and Optimum Gain Aperture Coupled Micro-Strip Antenna
摘要： Microstrip antennas have attained wide acceptance because of its size and conformability. But it has a limitation of less bandwidth. In order to overcome this various techniques have been proposed. Aperture coupling is one of them, it has a lot of design ?exibility with various design parameters. In this paper an aperture coupled microstrip antenna is designed and simulated using CST Microwave studio. The designed antenna operates at X-band 9.79 to 11.79 GHz (VSWR < 2) with 18.53% bandwidth, side lobe level (SLL) nearly -13 dB over bandwidth and the gain and directivity varies from 6.58 dB to 7.7 dB and 8.3 to 8.6 dBi, respectively.
关键词： Side Lobe Level,Aperture Coupling,VSWR,Bandwidth,Gain
更新于2025-09-16 10:30:52
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[IEEE 2019 IEEE International Symposium on Antennas and Propagation and USNC-URSI Radio Science Meeting - Atlanta, GA, USA (2019.7.7-2019.7.12)] 2019 IEEE International Symposium on Antennas and Propagation and USNC-URSI Radio Science Meeting - Wideband printed ridge gap waveguide differential feeding aperture antenna for millimeter wave applications
摘要： Millimeter wave has gained great attention for 5G communications and imaging systems. Building a high gain antenna is essential to such systems. In this paper, the design of a high gain differential feeding aperture antenna in the printed ridge gap waveguide technology is presented. It has a fractional bandwidth of 16.1% at 30GHz with S11<?10dB and peak gain of 12.8dBi. The aperture efficiency is 52% and the radiation pattern is stable over the operating frequency range. The 3-dB gain bandwidth is 15.4%dBi.
关键词： 5G communications,Millimeter wave,high gain antenna,printed ridge gap waveguide,differential feeding aperture antenna
更新于2025-09-16 10:30:52