In the field of deep space exploration,the rapid development of terahertz spectrometer has put forward higher requirements to the back-end chirp transform spectrometer(CTS)system.In order to simultaneously meet the me...In the field of deep space exploration,the rapid development of terahertz spectrometer has put forward higher requirements to the back-end chirp transform spectrometer(CTS)system.In order to simultaneously meet the measurement requirements of wide bandwidth and high accuracy spectral lines,we built a CTS system with an analysis bandwidth of 1 GHz and a frequency resolution of 100 kHz around the surface acoustic wave(SAW)chirp filter with a bandwidth of 1 GHz.In this paper,the relationship between the CTS nonlinear phase error shift model and the basic measurement parameters is studied,and the effect of CTS phase mismatch on the pulse compression waveform is analyzed by simulation.And the expander error optimization method is proposed for the problem that the large nonlinear error of the expander leads to the unbalanced response of the CTS system and the serious distortion of the compressed pulse waveform under large bandwidth.It is verified through simulation and experiment that the method is effective for reducing the root mean square error(RMSE)of the phase of the expander from 18.75°to 6.65°,reducing the in-band standard deviation of the CTS frequency resolution index from 8.43 kHz to 4.72 kHz,solving the problem of serious distortion of the compressed pulse waveform,and improving the uneven CTS response under large bandwidth.展开更多
Various electromagnetic signals are excited by the beam in the acceleration and beam-diagnostic elements of a particle accelerator.It is important to obtain time-domain waveforms of these signals with high temporal re...Various electromagnetic signals are excited by the beam in the acceleration and beam-diagnostic elements of a particle accelerator.It is important to obtain time-domain waveforms of these signals with high temporal resolution for research,such as the study of beam–cavity interactions and bunch-by-bunch parameter measurements.Therefore,a signal reconstruction algorithm with ultrahigh spatiotemporal resolution and bunch phase compensation based on equivalent sampling is proposed in this paper.Compared with traditional equivalent sampling,the use of phase compensation and setting the bunch signal zero-crossing point as the time reference can construct a more accurate reconstructed signal.The basic principles of the method,simulation,and experimental comparison are also introduced.Based on the beam test platform of the Shanghai Synchrotron Radiation Facility(SSRF)and the method of experimental verification,the factors that affect the reconstructed signal quality are analyzed and discussed,including the depth of the sampled data,quantization noise of analog-to-digital converter,beam transverse oscillation,and longitudinal oscillation.The results of the beam experiments show that under the user operation conditions of the SSRF,a beam excitation signal with an amplitude uncertainty of 2%can be reconstructed.展开更多
As same as the conventional inverse synthetic aperture radar（ISAR）, the compressed ISAR also requires the echo signal based motion compensation, which consists of the range alignment and the phase autofoeusing. A ph...As same as the conventional inverse synthetic aperture radar（ISAR）, the compressed ISAR also requires the echo signal based motion compensation, which consists of the range alignment and the phase autofoeusing. A phase autofocusing algorithm for compressed ISAR imaging is presented. In the algorithm, phase autofocusing for the sparse ISAR echoes is accomplished using the eigenvector method. Experimental results validate the effectiveness of the algorithm.展开更多
Maintaining the s-polarization state of laser beams is important to achieve high modulation depth in a laser-interference-based super-resolution structured illumination microscope(SR-SIM).However,the imperfect optical...Maintaining the s-polarization state of laser beams is important to achieve high modulation depth in a laser-interference-based super-resolution structured illumination microscope(SR-SIM).However,the imperfect optical components can depolarize the laser beams hence degenerating the modulation depth.Here,we first presented a direct measurement method designed to estimate the modulation depth more precisely by shifting illumination patterns with equal phase steps.This measurement method greatly reduces the dependence of modulation depths on the samples,and then developed a polarization optimization method to achieve high modulation depth at all orientations by actively and quantitatively compensating for the additional phase difference using a combination of waveplate and a liquid crystal variable retarder(LCVR).Experimental results demonstrate that our method can achieve illumination patterns with modulation depth higher than 0.94 at three orientations with only one LCVR voltage,which enables isotropic resolution improvement.展开更多
We demonstrate the transmission of a microwave frequency signal at 10 GHz over a 112-km urban fiber link based on a novel simple-architecture electronic phase compensation system.The key element of the system is the l...We demonstrate the transmission of a microwave frequency signal at 10 GHz over a 112-km urban fiber link based on a novel simple-architecture electronic phase compensation system.The key element of the system is the low noise frequency divider by 4 to differentiate the frequency of the forward signal from that of the backward one,thus suppressing the effect of Brillouin backscattering and parasitic reflection along the link.In terms of overlapping Allan deviation,the frequency transfer instability of 4.2×10-15 at 1-s integration time and 1.6×10-18 at one-day integration time was achieved.In addition,its sensitivity to the polarization mode dispersion in fiber is analyzed by comparing the results with and without laser polarization scrambling.Generally,with simplicity and robustness,the system can offer great potentials in constructing cascaded frequency transfer system and facilitate the building of fiber-based microwave transfer network.展开更多
Nonlinear response is an important factor affecting the accuracy of three-dimensional image measurement based on the fringe structured light method.A phase compensation algorithm combined with a Hilbert transform is p...Nonlinear response is an important factor affecting the accuracy of three-dimensional image measurement based on the fringe structured light method.A phase compensation algorithm combined with a Hilbert transform is proposed to reduce the phase error caused by the nonlinear response of a digital projector in the three-dimensional measurement system of fringe structured light.According to the analysis of the influence of Gamma distortion on the phase calculation,the algorithm establishes the relationship model between phase error and harmonic coefficient,introduces phase shift to the signal,and keeps the signal amplitude constant while filtering out the DC component.The phase error is converted to the transform domain,and compared with the numeric value in the space domain.The algorithm is combined with a spiral phase function to optimize the Hilbert transform,so as to eliminate external noise,enhance the image quality,and get an accurate phase value.Experimental results show that the proposed method can effectively improve the accuracy and speed of phase measurement.By performing phase error compensation for free-form surface objects,the phase error is reduced by about 26%,and about 27%of the image reconstruction time is saved,which further demonstrates the feasibility and effectiveness of the method.展开更多
The phase diagrams in the mixed spin-3/2 and spin-2 Ising system with two alternative layers on a honeycomb lattice are investigated and discussed by the use of the effective-field theory with correlations. The intera...The phase diagrams in the mixed spin-3/2 and spin-2 Ising system with two alternative layers on a honeycomb lattice are investigated and discussed by the use of the effective-field theory with correlations. The interaction of the nearest-neighbour spins of each layer is taken to be positive （ferromagnetic interaction） and the interaction of the adjacent spins of the nearest-neighbour layers is considered to be either positive or negative （ferromagnetic or antiferromagnetic interaction）. The temperature dependence of the layer magnetizations of the system is examined to characterize the nature （continuous or discontinuous） of the phase transitions and obtain the phase transition temperatures. The system exhibits both second- and first-order phase transitions besides triple point （TP）, critical end point （E）, multicritical point （A）, isolated critical point （C） and reentrant behaviour depending on the interaction parameters. We have also studied the temperature dependence of the total magnetization to find the compensation points, as well as to determine the type of behaviour, and N-type behaviour in Neel classification nomenclature existing in the system. The phase diagrams are constructed in eight different planes and it is found that the system also presents the compensation phenomena depending on the sign of the bilinear exchange interactions.展开更多
Flat optics have attracted interest for decades due to their flexibility in manipulating optical wave properties,which allows the miniaturization of bulky optical assemblies into integrated planar components.Recent ad...Flat optics have attracted interest for decades due to their flexibility in manipulating optical wave properties,which allows the miniaturization of bulky optical assemblies into integrated planar components.Recent advances in achromatic flat lenses have shown promising applications in various fields.However,it is a significant challenge for achromatic flat lenses with a high numerical aperture to simultaneously achieve broad bandwidth and expand the aperture sizes.Here,we present the zone division multiplex of the meta-atoms on a stepwise phase dispersion compensation(SPDC)layer to address the above challenge.In principle,the aperture size can be freely enlarged by increasing the optical thickness difference between the central and marginal zones of the SPDC layer,without the limit of the achromatic bandwidth.The SPDC layer also serves as the substrate,making the device thinner.Two achromatic flat lenses of 500 nm thickness with a bandwidth of 650–1000 nm are experimentally achieved:one with a numerical aperture of 0.9 and a radius of 20.1µm,and another with a numerical aperture of 0.7 and a radius of 30.0µm.To the best of our knowledge,they are the broadband achromatic flat lenses with highest numerical apertures,the largest aperture sizes and thinnest thickness reported so far.Microscopic imaging with a 1.10µm resolution has also been demonstrated by white light illumination,surpassing any previously reported resolution attained by achromatic metalenses and multi-level diffractive lenses.These unprecedented performances mark a substantial step toward practical applications of flat lenses.展开更多
Motion compensation is a key step for inverse synthetic aperture radar (ISAR) imaging. Many algorithms have been proposed. The rank one phase estimation (ROPE) algorithm is a good estimator for phase error widely used...Motion compensation is a key step for inverse synthetic aperture radar (ISAR) imaging. Many algorithms have been proposed. The rank one phase estimation (ROPE) algorithm is a good estimator for phase error widely used in SAR. The ROPE algorithm is used in ISAR phase compensation and the concrete implementation steps are presented. Subsequently, the performance of ROPE is analyzed. For ISAR data that fit the ROPE algorithm model, an excellent compensation effect can be obtained with high computation efficiency. Finally, ISAR real data are processed with ROPE and its imaging result is compared with that obtained by the modified Doppler centroid tracking (MDCT) method, which is a robust and good estimator in ISAR phase compensation.展开更多
Microsphere assisted microscopy(MAM)has been rapidly developed to meet the measurement needs of microstructures.MAM can be integrated with optical interference microscopy(OIM)to achieve high lateral resolution surface...Microsphere assisted microscopy(MAM)has been rapidly developed to meet the measurement needs of microstructures.MAM can be integrated with optical interference microscopy(OIM)to achieve high lateral resolution surface profile measurement.However,the microspheres introduce intricate phase changes,resulting in optical path asymmetry which is very challenging to compensate for.This limitation constrains the application of MAM in OIM.In this paper,simulation analysis reveals that the phase transmission of the microsphere is influenced by parameters such as microsphere diameter and its relative position to the sample.It is concluded that a unique compensation process must be adopted for each individual microsphere.Addressing this issue,we proposed a phase compensation algorithm based on the three-dimensional position control of the microsphere and integrated it into our combined system of MAM and white light interferometry(WLI),reducing the phase errors introduced by the microspheres while enhancing the lateral resolution of optical system.This approach improved the profile measurement accuracy,offering a perspective for optically measuring the surface profile of intricate microstructures.展开更多
This work proposes a new strategy to improve the rotor position estimation of a permanent magnet synchronous motor(PMSM) over wide speed range. Rotor position estimation of a PMSM is performed by using sliding mode ob...This work proposes a new strategy to improve the rotor position estimation of a permanent magnet synchronous motor(PMSM) over wide speed range. Rotor position estimation of a PMSM is performed by using sliding mode observer(SMO). An adaptive observer gain was designed based on Lyapunov function and applied to solve the chattering problem caused by the discontinuous function of the SMO in the wide speed range. The cascade low-pass filter(LPF) with variable cut-off frequency was proposed to reduce the chattering problem and to attenuate the filtering capability of the SMO. In addition, the phase shift caused by the filter was counterbalanced by applying the variable phase delay compensation for the whole speed area. High accuracy estimation result of the rotor position was obtained in the experiment by applying the proposed estimation strategy.展开更多
In this paper, the authors present the transmission line (TL) realization of one-dimensional subwavelength resonator formed by a pair of conventional right-handed material (RHM) and left-handed material (LHM). In such...In this paper, the authors present the transmission line (TL) realization of one-dimensional subwavelength resonator formed by a pair of conventional right-handed material (RHM) and left-handed material (LHM). In such resonator, a novel reso- nant mode with the resonant frequency depending on the length ratio of the RH/LH TL sections occurs as a consequence of the full phase compensation due to the backward wave in the LH TL section. The theoretical circuit-model analyses are supported by simulation and experimental evidence on resonators with different RH/LH length ratios.展开更多
This paper first studies the phase errors for fine-resolution spotlight mode SAR imaging and decomposes the phase errors into two kinds, one is caused by translation and the other by rotation. Mathematical analysis an...This paper first studies the phase errors for fine-resolution spotlight mode SAR imaging and decomposes the phase errors into two kinds, one is caused by translation and the other by rotation. Mathematical analysis and computer simulations show the above mentioned motion kinds and their corresponding damages on spotlight mode SAR imaging. Based on this analysis, a single PPP is introduced for spotlight mode SAR imaging with the PFA on the assumption that relative rotation between APC and imaged scene is uniform. The selected single point is used first to correct the quadratic and higher order phase errors and then to adjust the linear errors. After this compensation, the space-invariant phase errors caused by translation are almost corrected. Finally results are presented with the simulated data.展开更多
AIM: Variation in structure-related components in plant products prompted the trend to establish methods, using multiple or total analog analysis, for their effective quality control. However, the general use of routi...AIM: Variation in structure-related components in plant products prompted the trend to establish methods, using multiple or total analog analysis, for their effective quality control. However, the general use of routine quality control is restricted by the limited availability of reference substances. Using an easily available single marker as a reference standard to determine multiple or total analogs should be a practical option. METHOD: In this study, the Ultra-HPLC method was used for the baseline separation of the main components in ginseng extracts. Using a plant chemical component database, ginsenosides in ginseng extracts were identified by Ultra-HPLC-MS analysis. The charged aerosol detection(CAD) system with post-column compensation of the gradient generates a similar response for identical amounts of different analytes, and thus, the content of each ginsenoside in ginseng extracts was determined by comparing the analyte peak area with the reference standard(determination of total analogs by single marker, DTSM). The total ginsenoside content was determined by the summation of reference standard and other ginsenoside components. RESULTS: The results showed that DTSM approaches were available for the determination of total ginsenosides in a high purity ginseng extract because of the removal of impurities. In contrast, DTSM approaches might be suitable for determination of multiple ginsenosides without interference from impurities in the crude ginseng extract. CONCLUSION: Future practical studies similar to the present study should be conducted to verify that DTSM approaches based on CAD with post-column inverse gradient for uniform response are ideal for the quality control of plant products.展开更多
Although the structured light system that uses digital fringe projection has been widely implemented in three-dimensional surface profile measurement, the measurement system is susceptible to non-linear error. In this...Although the structured light system that uses digital fringe projection has been widely implemented in three-dimensional surface profile measurement, the measurement system is susceptible to non-linear error. In this work, we propose a convenient look-up-table-based （LUT-based） method to compensate for the non-linear error in captured fringe patterns. Without extra calibration, this LUT-based method completely utilizes the captured fringe pattern by recording the full-field differences. Then, a phase compensation map is established to revise the measured phase. Experimental results demonstrate that this method works effectively.展开更多
Supercontinuum generation and compression in a length of 50-ram photonic crystal fiber with pulse of nanojoule energy are investigated theoretically and experimentally. Chirped mirror pair is used for dispersion compe...Supercontinuum generation and compression in a length of 50-ram photonic crystal fiber with pulse of nanojoule energy are investigated theoretically and experimentally. Chirped mirror pair is used for dispersion compensation and pulse compression. Pulse characteristics are measured by frequency-resolved optical gating. And 19-fs pulse is generated.展开更多
To improve the transmission performance of XCTD channel, this paper proposes a method to measure directly and fit the channel transmission characteristics by using frequency sweeping method. Sinusoidal signals with a ...To improve the transmission performance of XCTD channel, this paper proposes a method to measure directly and fit the channel transmission characteristics by using frequency sweeping method. Sinusoidal signals with a frequency range of 100 Hz to 10 k Hz and an interval of 100 Hz are used to measure transmission characteristics of channels with lengths of 300 m, 800 m, 1300 m, and 1800 m. The correctness of the fitted channel characteristics by transmitting square wave, composite waves of different frequencies, and ASK modulation are verified. The results show that when the frequency of the signal is below 1500 Hz, the channel has very little effect on the signal. The signal compensated for amplitude and phase at the receiver is not as good as the uncompensated signal.Alternatively, when the signal frequency is above 1500 Hz, the channel distorts the signal. The quality of signal compensated for amplitude and phase at receiver is better than that of the uncompensated signal. Thus, we can select the appropriate frequency for XCTD system and the appropriate way to process the received signals. Signals below1500 Hz can be directly used at the receiving end. Signals above 1500 Hz are used after amplitude and phase compensation at the receiving end.展开更多
Introduction of the stepwise phase dispersion compensation layer allowed broadband achromatic metalens to have a high numerical aperture,which enabled high-resolution metalens imaging.
A new strategy has been presented to overcome the long-term dilemma of simultaneously achieving high numerical aperture,large aperture size,and broadband achromatism of flat lenses.A stepwise phase dispersion compensa...A new strategy has been presented to overcome the long-term dilemma of simultaneously achieving high numerical aperture,large aperture size,and broadband achromatism of flat lenses.A stepwise phase dispersion compensation(SPDC)layer is introduced as a substrate on which the meta-atoms are positioned.展开更多
We propose a passive compensation fiber-optic radio frequency（RF） transfer scheme with a nonsynchronized RF stable source during a round-trip time, which can avoid high-precision phase-locking and efficiently suppre...We propose a passive compensation fiber-optic radio frequency（RF） transfer scheme with a nonsynchronized RF stable source during a round-trip time, which can avoid high-precision phase-locking and efficiently suppress the effect of backscattering only using two wavelengths at the same time. A stable frequency signal is directly reproduced by frequency mixing at the remote site. The proposed scheme is validated by the experiment over a 40 km single mode fiber spool using nonsynchronized common commercial RF sources. The influence of the stability of nonsynchronized RF sources on the frequency transfer is investigated over different length fiber links.展开更多
文摘In the field of deep space exploration,the rapid development of terahertz spectrometer has put forward higher requirements to the back-end chirp transform spectrometer(CTS)system.In order to simultaneously meet the measurement requirements of wide bandwidth and high accuracy spectral lines,we built a CTS system with an analysis bandwidth of 1 GHz and a frequency resolution of 100 kHz around the surface acoustic wave(SAW)chirp filter with a bandwidth of 1 GHz.In this paper,the relationship between the CTS nonlinear phase error shift model and the basic measurement parameters is studied,and the effect of CTS phase mismatch on the pulse compression waveform is analyzed by simulation.And the expander error optimization method is proposed for the problem that the large nonlinear error of the expander leads to the unbalanced response of the CTS system and the serious distortion of the compressed pulse waveform under large bandwidth.It is verified through simulation and experiment that the method is effective for reducing the root mean square error(RMSE)of the phase of the expander from 18.75°to 6.65°,reducing the in-band standard deviation of the CTS frequency resolution index from 8.43 kHz to 4.72 kHz,solving the problem of serious distortion of the compressed pulse waveform,and improving the uneven CTS response under large bandwidth.
基金supported by the National Key R&D Program of China(No.2022YFA1602201)the international partnership program of the Chinese Academy of Sciences(No.211134KYSB20200057).
文摘Various electromagnetic signals are excited by the beam in the acceleration and beam-diagnostic elements of a particle accelerator.It is important to obtain time-domain waveforms of these signals with high temporal resolution for research,such as the study of beam–cavity interactions and bunch-by-bunch parameter measurements.Therefore,a signal reconstruction algorithm with ultrahigh spatiotemporal resolution and bunch phase compensation based on equivalent sampling is proposed in this paper.Compared with traditional equivalent sampling,the use of phase compensation and setting the bunch signal zero-crossing point as the time reference can construct a more accurate reconstructed signal.The basic principles of the method,simulation,and experimental comparison are also introduced.Based on the beam test platform of the Shanghai Synchrotron Radiation Facility(SSRF)and the method of experimental verification,the factors that affect the reconstructed signal quality are analyzed and discussed,including the depth of the sampled data,quantization noise of analog-to-digital converter,beam transverse oscillation,and longitudinal oscillation.The results of the beam experiments show that under the user operation conditions of the SSRF,a beam excitation signal with an amplitude uncertainty of 2%can be reconstructed.
基金Supported by the National Natural Science Foundation of China(61071165)the Program for NewCentury Excellent Talents in University(NCET-09-0069)the Defense Industrial Technology Development Program(B2520110008)~~
文摘As same as the conventional inverse synthetic aperture radar（ISAR）, the compressed ISAR also requires the echo signal based motion compensation, which consists of the range alignment and the phase autofoeusing. A phase autofocusing algorithm for compressed ISAR imaging is presented. In the algorithm, phase autofocusing for the sparse ISAR echoes is accomplished using the eigenvector method. Experimental results validate the effectiveness of the algorithm.
基金supported by the National Natural Science Foundation of China[Grant Nos.62205367 and 62141506]the Suzhou Basic Research Pilot Project[Grant Nos.SSD2023006 and SJC2021013]the National Key Research and Development Program of China[Grant No.2023YFF1205700].
文摘Maintaining the s-polarization state of laser beams is important to achieve high modulation depth in a laser-interference-based super-resolution structured illumination microscope(SR-SIM).However,the imperfect optical components can depolarize the laser beams hence degenerating the modulation depth.Here,we first presented a direct measurement method designed to estimate the modulation depth more precisely by shifting illumination patterns with equal phase steps.This measurement method greatly reduces the dependence of modulation depths on the samples,and then developed a polarization optimization method to achieve high modulation depth at all orientations by actively and quantitatively compensating for the additional phase difference using a combination of waveplate and a liquid crystal variable retarder(LCVR).Experimental results demonstrate that our method can achieve illumination patterns with modulation depth higher than 0.94 at three orientations with only one LCVR voltage,which enables isotropic resolution improvement.
基金National Natural Science Foundation of China(Grant Nos.61825505,91536217,and 61127901).
文摘We demonstrate the transmission of a microwave frequency signal at 10 GHz over a 112-km urban fiber link based on a novel simple-architecture electronic phase compensation system.The key element of the system is the low noise frequency divider by 4 to differentiate the frequency of the forward signal from that of the backward one,thus suppressing the effect of Brillouin backscattering and parasitic reflection along the link.In terms of overlapping Allan deviation,the frequency transfer instability of 4.2×10-15 at 1-s integration time and 1.6×10-18 at one-day integration time was achieved.In addition,its sensitivity to the polarization mode dispersion in fiber is analyzed by comparing the results with and without laser polarization scrambling.Generally,with simplicity and robustness,the system can offer great potentials in constructing cascaded frequency transfer system and facilitate the building of fiber-based microwave transfer network.
基金This work is funded by the Scientific and Technological Projects of Henan Province under Grant 152102210115.
文摘Nonlinear response is an important factor affecting the accuracy of three-dimensional image measurement based on the fringe structured light method.A phase compensation algorithm combined with a Hilbert transform is proposed to reduce the phase error caused by the nonlinear response of a digital projector in the three-dimensional measurement system of fringe structured light.According to the analysis of the influence of Gamma distortion on the phase calculation,the algorithm establishes the relationship model between phase error and harmonic coefficient,introduces phase shift to the signal,and keeps the signal amplitude constant while filtering out the DC component.The phase error is converted to the transform domain,and compared with the numeric value in the space domain.The algorithm is combined with a spiral phase function to optimize the Hilbert transform,so as to eliminate external noise,enhance the image quality,and get an accurate phase value.Experimental results show that the proposed method can effectively improve the accuracy and speed of phase measurement.By performing phase error compensation for free-form surface objects,the phase error is reduced by about 26%,and about 27%of the image reconstruction time is saved,which further demonstrates the feasibility and effectiveness of the method.
基金Project supported by the Scientific and Technological Research Council of Turkey (TBTAK) (Grant No. 107T533)Erciyes University Research Funds (Grant No. FBD-08-593)
文摘The phase diagrams in the mixed spin-3/2 and spin-2 Ising system with two alternative layers on a honeycomb lattice are investigated and discussed by the use of the effective-field theory with correlations. The interaction of the nearest-neighbour spins of each layer is taken to be positive （ferromagnetic interaction） and the interaction of the adjacent spins of the nearest-neighbour layers is considered to be either positive or negative （ferromagnetic or antiferromagnetic interaction）. The temperature dependence of the layer magnetizations of the system is examined to characterize the nature （continuous or discontinuous） of the phase transitions and obtain the phase transition temperatures. The system exhibits both second- and first-order phase transitions besides triple point （TP）, critical end point （E）, multicritical point （A）, isolated critical point （C） and reentrant behaviour depending on the interaction parameters. We have also studied the temperature dependence of the total magnetization to find the compensation points, as well as to determine the type of behaviour, and N-type behaviour in Neel classification nomenclature existing in the system. The phase diagrams are constructed in eight different planes and it is found that the system also presents the compensation phenomena depending on the sign of the bilinear exchange interactions.
基金supported by the National Key R&D Program of China(No.2021YFA1400800)National Natural Science Foundation of China(Nos.12374363,12074444,and 11704421)+2 种基金Guangdong Basic and Applied Basic Research Foundation(No.2020B0301030009)Guangdong Provincial Natural Science Fund Projects(2024B1515040013)Guangdong Provincial Quantum Science Strategic Initiative(GDZX2306002,GDZX2206001)。
文摘Flat optics have attracted interest for decades due to their flexibility in manipulating optical wave properties,which allows the miniaturization of bulky optical assemblies into integrated planar components.Recent advances in achromatic flat lenses have shown promising applications in various fields.However,it is a significant challenge for achromatic flat lenses with a high numerical aperture to simultaneously achieve broad bandwidth and expand the aperture sizes.Here,we present the zone division multiplex of the meta-atoms on a stepwise phase dispersion compensation(SPDC)layer to address the above challenge.In principle,the aperture size can be freely enlarged by increasing the optical thickness difference between the central and marginal zones of the SPDC layer,without the limit of the achromatic bandwidth.The SPDC layer also serves as the substrate,making the device thinner.Two achromatic flat lenses of 500 nm thickness with a bandwidth of 650–1000 nm are experimentally achieved:one with a numerical aperture of 0.9 and a radius of 20.1µm,and another with a numerical aperture of 0.7 and a radius of 30.0µm.To the best of our knowledge,they are the broadband achromatic flat lenses with highest numerical apertures,the largest aperture sizes and thinnest thickness reported so far.Microscopic imaging with a 1.10µm resolution has also been demonstrated by white light illumination,surpassing any previously reported resolution attained by achromatic metalenses and multi-level diffractive lenses.These unprecedented performances mark a substantial step toward practical applications of flat lenses.
文摘Motion compensation is a key step for inverse synthetic aperture radar (ISAR) imaging. Many algorithms have been proposed. The rank one phase estimation (ROPE) algorithm is a good estimator for phase error widely used in SAR. The ROPE algorithm is used in ISAR phase compensation and the concrete implementation steps are presented. Subsequently, the performance of ROPE is analyzed. For ISAR data that fit the ROPE algorithm model, an excellent compensation effect can be obtained with high computation efficiency. Finally, ISAR real data are processed with ROPE and its imaging result is compared with that obtained by the modified Doppler centroid tracking (MDCT) method, which is a robust and good estimator in ISAR phase compensation.
基金supported by National Natural Science Foundation of China(No.52275540).
文摘Microsphere assisted microscopy(MAM)has been rapidly developed to meet the measurement needs of microstructures.MAM can be integrated with optical interference microscopy(OIM)to achieve high lateral resolution surface profile measurement.However,the microspheres introduce intricate phase changes,resulting in optical path asymmetry which is very challenging to compensate for.This limitation constrains the application of MAM in OIM.In this paper,simulation analysis reveals that the phase transmission of the microsphere is influenced by parameters such as microsphere diameter and its relative position to the sample.It is concluded that a unique compensation process must be adopted for each individual microsphere.Addressing this issue,we proposed a phase compensation algorithm based on the three-dimensional position control of the microsphere and integrated it into our combined system of MAM and white light interferometry(WLI),reducing the phase errors introduced by the microspheres while enhancing the lateral resolution of optical system.This approach improved the profile measurement accuracy,offering a perspective for optically measuring the surface profile of intricate microstructures.
基金Project(2012(PS-2012-090))supported by the Pukyong National University Research Abroad Fund,Korea
文摘This work proposes a new strategy to improve the rotor position estimation of a permanent magnet synchronous motor(PMSM) over wide speed range. Rotor position estimation of a PMSM is performed by using sliding mode observer(SMO). An adaptive observer gain was designed based on Lyapunov function and applied to solve the chattering problem caused by the discontinuous function of the SMO in the wide speed range. The cascade low-pass filter(LPF) with variable cut-off frequency was proposed to reduce the chattering problem and to attenuate the filtering capability of the SMO. In addition, the phase shift caused by the filter was counterbalanced by applying the variable phase delay compensation for the whole speed area. High accuracy estimation result of the rotor position was obtained in the experiment by applying the proposed estimation strategy.
基金Project supported by the National Basic Research Program (973) of China (No. 2004CB719800) and the Specialized Research Fund for the Doctoral Program of Higher Education (No. 20030284024)
文摘In this paper, the authors present the transmission line (TL) realization of one-dimensional subwavelength resonator formed by a pair of conventional right-handed material (RHM) and left-handed material (LHM). In such resonator, a novel reso- nant mode with the resonant frequency depending on the length ratio of the RH/LH TL sections occurs as a consequence of the full phase compensation due to the backward wave in the LH TL section. The theoretical circuit-model analyses are supported by simulation and experimental evidence on resonators with different RH/LH length ratios.
基金Supported by the Aeronautic Scientific Foundation(No.98F5118)
文摘This paper first studies the phase errors for fine-resolution spotlight mode SAR imaging and decomposes the phase errors into two kinds, one is caused by translation and the other by rotation. Mathematical analysis and computer simulations show the above mentioned motion kinds and their corresponding damages on spotlight mode SAR imaging. Based on this analysis, a single PPP is introduced for spotlight mode SAR imaging with the PFA on the assumption that relative rotation between APC and imaged scene is uniform. The selected single point is used first to correct the quadratic and higher order phase errors and then to adjust the linear errors. After this compensation, the space-invariant phase errors caused by translation are almost corrected. Finally results are presented with the simulated data.
基金supported by the National Natural Science Foundation of China(81303246)the Jiangsu Provincial Natural Science Foundation of China(BK2011815)+1 种基金the ‘Qing Lan’ Project from Jiangsu Provincial Framework Teacher Support Schemethe Projects of priority-discipline for colleges and universities of Jiangsu Province
文摘AIM: Variation in structure-related components in plant products prompted the trend to establish methods, using multiple or total analog analysis, for their effective quality control. However, the general use of routine quality control is restricted by the limited availability of reference substances. Using an easily available single marker as a reference standard to determine multiple or total analogs should be a practical option. METHOD: In this study, the Ultra-HPLC method was used for the baseline separation of the main components in ginseng extracts. Using a plant chemical component database, ginsenosides in ginseng extracts were identified by Ultra-HPLC-MS analysis. The charged aerosol detection(CAD) system with post-column compensation of the gradient generates a similar response for identical amounts of different analytes, and thus, the content of each ginsenoside in ginseng extracts was determined by comparing the analyte peak area with the reference standard(determination of total analogs by single marker, DTSM). The total ginsenoside content was determined by the summation of reference standard and other ginsenoside components. RESULTS: The results showed that DTSM approaches were available for the determination of total ginsenosides in a high purity ginseng extract because of the removal of impurities. In contrast, DTSM approaches might be suitable for determination of multiple ginsenosides without interference from impurities in the crude ginseng extract. CONCLUSION: Future practical studies similar to the present study should be conducted to verify that DTSM approaches based on CAD with post-column inverse gradient for uniform response are ideal for the quality control of plant products.
基金the financial support provided by the National Natural Science Foundation of China(11472267 and 11372182)the National Basic Research Program of China(2012CB937504)
文摘Although the structured light system that uses digital fringe projection has been widely implemented in three-dimensional surface profile measurement, the measurement system is susceptible to non-linear error. In this work, we propose a convenient look-up-table-based （LUT-based） method to compensate for the non-linear error in captured fringe patterns. Without extra calibration, this LUT-based method completely utilizes the captured fringe pattern by recording the full-field differences. Then, a phase compensation map is established to revise the measured phase. Experimental results demonstrate that this method works effectively.
文摘Supercontinuum generation and compression in a length of 50-ram photonic crystal fiber with pulse of nanojoule energy are investigated theoretically and experimentally. Chirped mirror pair is used for dispersion compensation and pulse compression. Pulse characteristics are measured by frequency-resolved optical gating. And 19-fs pulse is generated.
基金financially supported by the National Key Research and Development Program of China(Grant No.2016YFC1400400)
文摘To improve the transmission performance of XCTD channel, this paper proposes a method to measure directly and fit the channel transmission characteristics by using frequency sweeping method. Sinusoidal signals with a frequency range of 100 Hz to 10 k Hz and an interval of 100 Hz are used to measure transmission characteristics of channels with lengths of 300 m, 800 m, 1300 m, and 1800 m. The correctness of the fitted channel characteristics by transmitting square wave, composite waves of different frequencies, and ASK modulation are verified. The results show that when the frequency of the signal is below 1500 Hz, the channel has very little effect on the signal. The signal compensated for amplitude and phase at the receiver is not as good as the uncompensated signal.Alternatively, when the signal frequency is above 1500 Hz, the channel distorts the signal. The quality of signal compensated for amplitude and phase at receiver is better than that of the uncompensated signal. Thus, we can select the appropriate frequency for XCTD system and the appropriate way to process the received signals. Signals below1500 Hz can be directly used at the receiving end. Signals above 1500 Hz are used after amplitude and phase compensation at the receiving end.
文摘Introduction of the stepwise phase dispersion compensation layer allowed broadband achromatic metalens to have a high numerical aperture,which enabled high-resolution metalens imaging.
文摘A new strategy has been presented to overcome the long-term dilemma of simultaneously achieving high numerical aperture,large aperture size,and broadband achromatism of flat lenses.A stepwise phase dispersion compensation(SPDC)layer is introduced as a substrate on which the meta-atoms are positioned.
基金supported by the National Natural Science Foundation of China(NSFC)(Nos.61627817 and 61535006)
文摘We propose a passive compensation fiber-optic radio frequency（RF） transfer scheme with a nonsynchronized RF stable source during a round-trip time, which can avoid high-precision phase-locking and efficiently suppress the effect of backscattering only using two wavelengths at the same time. A stable frequency signal is directly reproduced by frequency mixing at the remote site. The proposed scheme is validated by the experiment over a 40 km single mode fiber spool using nonsynchronized common commercial RF sources. The influence of the stability of nonsynchronized RF sources on the frequency transfer is investigated over different length fiber links.
