By using the theory of measured phase operator proposed by Barnett and Pegg, dynamic properties of the phase of a field are studied. The time evolution and squeezing of measured phase operators of a coherent field int...By using the theory of measured phase operator proposed by Barnett and Pegg, dynamic properties of the phase of a field are studied. The time evolution and squeezing of measured phase operators of a coherent field interacting with a two-level atom in the cavity with or without the Kerr medium are investigated. The influences of virtual cavity field on squeezing of measured phase operator are studied. Our numerical results show that the squeezing effects are clearly influenced by Kerr medium parameters, the field intensity, and the detuning. Moreover, the influence of the virtual-photon field makes more quantum noise in the evolution of measured phase operators. Key words Jaynes-Cummings model (JCM) - Kerr medium - measured phase operator - squeezing - virtual photon PACS 2001 4250Dv展开更多
We study the higher order fluctuations and squeezing of quadrature operators in the squeezed thermal states. In terms of measured phase operators, we discuss the fluctuations and squeezing of phases in these states....We study the higher order fluctuations and squeezing of quadrature operators in the squeezed thermal states. In terms of measured phase operators, we discuss the fluctuations and squeezing of phases in these states. We conclude that the condition of higher order squeezing for quadrature components of the field is order independent and the fluctuations of measured phase operators are temperature independent.展开更多
Using computer-controlled liquid crystal display (LCD) as an image processor and a CCD camera as a detector, phase-only correlation measurement is performed with the aid of joint transform correlation method (JTC). Th...Using computer-controlled liquid crystal display (LCD) as an image processor and a CCD camera as a detector, phase-only correlation measurement is performed with the aid of joint transform correlation method (JTC). This computer -controlled LCD-CCD image processing system may be a powerful tool for defect detection, position control and pattern recognition. It enables new possibilities in analog real-time image processing. This is of great interest in microelectronic manufacturing today and in the future.展开更多
Based on the frequency-to-time mapping relation of the linearly chirped pulse, the temporal phase shift induced by a laser-excited wake in a helium gas jet is measured using a chirped-pulse spectral interferometry wi...Based on the frequency-to-time mapping relation of the linearly chirped pulse, the temporal phase shift induced by a laser-excited wake in a helium gas jet is measured using a chirped-pulse spectral interferometry with ～ 140 fs resolution over a temporal region of I ps in a single shot. In this measurement, the image of the wake is obtained with one-dimensional spatial resolution and temporal resolution limited only by the bandwidth and chirp of the pulse. The ＇bubbles＇ feature of the wake structure, along with multiple wakes excited by the main lobe and the side lobe of a laser focal-spot, is captured simultaneously.展开更多
We propose a simple iterative algorithm based on a temporally movable phase modulation process to retrieve the weak temporal phase of laser pulses. This unambiguous method can be used to achieve a high accuracy and to...We propose a simple iterative algorithm based on a temporally movable phase modulation process to retrieve the weak temporal phase of laser pulses. This unambiguous method can be used to achieve a high accuracy and to simultaneously measure the weak temporal phase and temporal profile of pulses, which are almost transform- limited. A detailed analysis shows that this iterative method has valuable potential applications in the charac- terization of pulses with weak temporal phase.展开更多
The magnetization behavior of a CuFeO2 single crystal grown by the floating zone technique is investigated with a pulsed high magnetic field. We observe a series of field-induced multi-step-like transitions with hyste...The magnetization behavior of a CuFeO2 single crystal grown by the floating zone technique is investigated with a pulsed high magnetic field. We observe a series of field-induced multi-step-like transitions with hysteresis, of which the critical magnetic fields are temperature-dependent and show anisotropy. By using a pulsed high magnetic field up to 75 T, the magnetization behavior shows that the critical transition magnetic fields of spin- flip/flop shift to lower field regions with an increase in temperature. According to the magnetization curves, a complete magnetic phase diagram is depicted.展开更多
A new error compensating five sample phase shifting algorithm which is insensitive to phase shift error is proposed to retrieve the phase distribution of a fringe pattern. It includes two steps. First, the linear ...A new error compensating five sample phase shifting algorithm which is insensitive to phase shift error is proposed to retrieve the phase distribution of a fringe pattern. It includes two steps. First, the linear phase shift error is estimated using four sample images. Then, the phase distribution is calculated with error corrected by using the phase shift error estimated in the first step. As the equations of error estimation and phase calculation are simple, this new algorithm is practical as well as effective. Computer simulations were carried out to verify the effectiveness of the algorithm. Results of two other well known error compensating algorithms are also presented, which show the new algorithm is the least sensitive to phase shift error.展开更多
This paper presents a new technique for measuring the bunch length of a high-energy electron beam at a bunch-by-bunch rate in storage rings.This technique uses the time–frequency-domain joint analysis of the bunch si...This paper presents a new technique for measuring the bunch length of a high-energy electron beam at a bunch-by-bunch rate in storage rings.This technique uses the time–frequency-domain joint analysis of the bunch signal to obtain bunch-by-bunch and turn-by-turn longitudinal parameters,such as bunch length and synchronous phase.The bunch signal is obtained using a button electrode with a bandwidth of several gigahertz.The data acquisition device was a high-speed digital oscilloscope with a sampling rate of more than 10 GS/s,and the single-shot sampling data buffer covered thousands of turns.The bunch-length and synchronous phase information were extracted via offline calculations using Python scripts.The calibration coefficient of the system was determined using a commercial streak camera.Moreover,this technique was tested on two different storage rings and successfully captured various longitudinal transient processes during the harmonic cavity debugging process at the Shanghai Synchrotron Radiation Facility(SSRF),and longitudinal instabilities were observed during the single-bunch accumulation process at Hefei Light Source(HLS).For Gaussian-distribution bunches,the uncertainty of the bunch phase obtained using this technique was better than 0.2 ps,and the bunch-length uncertainty was better than 1 ps.The dynamic range exceeded 10 ms.This technology is a powerful and versatile beam diagnostic tool that can be conveniently deployed in high-energy electron storage rings.展开更多
Using the Pegg-Barnett formalism we study the phase probability distributions and the squeezing effects of measured phase operators in the nonlinear coherent states introduced by R.L. de Matos Filho and W. Vogel to de...Using the Pegg-Barnett formalism we study the phase probability distributions and the squeezing effects of measured phase operators in the nonlinear coherent states introduced by R.L. de Matos Filho and W. Vogel to describe the center-of mass motion of a trapped ion and the q-coherent states. Moreover, we have obtained the completeness relation of nonlinear coherent states and proved that the q-Fock state \n>(q) introduced in many papers is, in fact, the usual Fock state.展开更多
In deep space exploration,many engineering and scientific requirements require the accuracy of the measured Doppler frequency to be as high as possible.In our paper,we analyze the possible frequency measurement points...In deep space exploration,many engineering and scientific requirements require the accuracy of the measured Doppler frequency to be as high as possible.In our paper,we analyze the possible frequency measurement points of the third-order phase-locked loop(PLL)and find a new Doppler measurement strategy.Based on this finding,a Doppler frequency measurement algorithm with significantly higher measurement accuracy is obtained.In the actual data processing,compared with the existing engineering software,the accuracy of frequency of 1 second integration is about 5.5 times higher when using the new algorithm.The improved algorithm is simple and easy to implement.This improvement can be easily combined with other improvement methods of PLL,so that the performance of PLL can be further improved.展开更多
Based on the basic principle of Time-Of-Flight cameras,a novel MATLAB/SIMULINK model is proposed to measure phase delay of a modulated light signal which represents the distance from camera to object. Subsequently,by ...Based on the basic principle of Time-Of-Flight cameras,a novel MATLAB/SIMULINK model is proposed to measure phase delay of a modulated light signal which represents the distance from camera to object. Subsequently,by discussing influence factors of phase measurement,it is found that the integration time,the sampling time,and the aliasing effect have important effect on improving the accuracy of phase measurement. Interestingly,by analyzing different integration time and sampling time, it is found that the best integration time and sampling time are 0.05 ms and 10 ns,respectively. In this case(i.e.,in absence of the aliasing effect),the variation range of the distance error is between 1 mm and 11 mm in the interval of one period. Especially,under the consideration of the aliasing effect,the average value of distance error is half of that in absence of the aliasing effect. This improves the accuracy of the distance measurement greatly.展开更多
The properties of measured phase operators in damped odd and even coherent states have been studied. The fluctuations associated with measured phase and their squeezing in these states are investigated. The phase prop...The properties of measured phase operators in damped odd and even coherent states have been studied. The fluctuations associated with measured phase and their squeezing in these states are investigated. The phase properties in damped superposition coherent states are considered too with the help of measured phase operators. These fluctuations and their squeezing are affected by damping and evolve with time elapsing.展开更多
We propose an approach to detect an unknown quantum state of the atom(s) by measuring the phase shifts of the transmitted photons through a dispersively-coupled cavity. In the framework of the input-output theory, we ...We propose an approach to detect an unknown quantum state of the atom(s) by measuring the phase shifts of the transmitted photons through a dispersively-coupled cavity. In the framework of the input-output theory, we derive the relations between the phase shifts of the transmitted photons and the states of the atom(s) in the cavity. It is shown that due to the dispersive interaction between the cavity and the atom(s), information about the atomic state can then be extracted by measuring the phase shifts of the transmitted photons through the cavity. The feasibility of the proposal is also discussed with the experimental parameters by numerical method.展开更多
The design and realization of a new generation of infra-red electronic distance measurement (IR EDM) system are presented.A DSP(Digital Signal Process) phase detector based on high speed analog-to-digital converter an...The design and realization of a new generation of infra-red electronic distance measurement (IR EDM) system are presented.A DSP(Digital Signal Process) phase detector based on high speed analog-to-digital converter and DSP technique has been designed,in order to improve the precision and reliability of IR EDM system.As a result,the EDM system developed with a DSP phase detector has a precision of 3 mm in the measuring range of 2 km.展开更多
Integrated profile is one of the basic characteristic of X-ray pulsar. Gaussian function fit is used to model the components of X-ray pulsar profile, and it is combined with Poisson distribution model of X-ray pulsar ...Integrated profile is one of the basic characteristic of X-ray pulsar. Gaussian function fit is used to model the components of X-ray pulsar profile, and it is combined with Poisson distribution model of X-ray pulsar to analyze Cramer-Rao low bound （CRLB） of phase, phase rate estimation and relation between CRLB and profile components. Then, a time domain method using minimum entropy is proposed for profile phase and phase rate estimation, and its effectiveness is explained using simulation examples.展开更多
Different from the traditional way of using piezoelectric （PZT）phase shifter to measure phase difference, a new method is designed to calculate it between signals in the two arms of a homodyne fiber interferometer. ...Different from the traditional way of using piezoelectric （PZT）phase shifter to measure phase difference, a new method is designed to calculate it between signals in the two arms of a homodyne fiber interferometer. A simple homodyne fiber interferometer system is then established to measure the interference photoeurrent and the photocurrents from the two fiber arms generated by the signal power on a temperature control plat. The homodyne fiber interferometer system is composed of fiber and sensitive to the variation of temperature. Thus, is necessary to study the temperature characteristics in the phase measurement of homodyne fiber interferometer. The experimental results show that the variation of the phase difference of signals in the two fiber arms is proportional to the variation of temperature.展开更多
Dispersed fringe sensor （DFS） is an important phasing sensor of next-generation optical astronomical telescopes. The measurement errors induced by the measurement noise of three piston estimation methods for the DFS...Dispersed fringe sensor （DFS） is an important phasing sensor of next-generation optical astronomical telescopes. The measurement errors induced by the measurement noise of three piston estimation methods for the DFS including leastsquared fitting （LSF） method, frequency peak location （FPL） method and main peak position （MPP） method, are analyzed theoretically and validated experimentally in this paper. The experimental results coincide well with the theoretical analyses. The MPP, FPL, LSF are used respectively when the DFS operates with broadband light （central wavelength： 706 nm, bandwidth： 23 nm）. The corresponding root mean square （RMS） value of estimated piston error can be achieved to be 1 nm, 3 nm, 26 nm, respectively. Additionally, the range of DFS with the FPL can be more than 100 μm at the same time. The FPL method can work well both in coarse and fine phasing stages with acceptable accuracy, compared with LSF method and MPP method.展开更多
The ambiguity resolution in the field of GPS is investigated in detail. A new algorithm to resolve the ambiguity is proposed. The algorithm first obtains the floating resolution of the ambiguity aided with triple diff...The ambiguity resolution in the field of GPS is investigated in detail. A new algorithm to resolve the ambiguity is proposed. The algorithm first obtains the floating resolution of the ambiguity aided with triple difference measurement. Decorrelation of searching space is done by reducing the ambiguity covariance matrix＇s dimension to overcome the possible sick factorization of the matrix brought by Z-transformation. In simulation, the proposed algorithm is compared with least-squares ambiguity decorrelation adjustment （LAMBDA）. The result shows that the proposed algorithm is better than LAMBDA because of lesser resolving time, which approximately reduces 20% resolving time. Thus, the proposed algorithm adapts to the high dynamic real-time applications.展开更多
With the development of optical coherence tomography,the application optical coherence elastography(OCE)has gained more and more attention in biomechanics for its unique features including micron-scale resolution,real...With the development of optical coherence tomography,the application optical coherence elastography(OCE)has gained more and more attention in biomechanics for its unique features including micron-scale resolution,real-time processing,and non-invasive imaging.In this review,one group of OCE techniques,namely dynamic OCE,are introduced and discussed including external dynamic OCE mapping and imaging of ex vivo breast tumor,external dynamic OCE measurement of in vivo human skin,and internal dynamic OCE including acoustomotive OCE and magnetomotive OCE.These techniques overcame some of the major drawbacks of traditional static OCE,and broadened the OCE application fields.Driven by scientific needs to engineer new quantitative methods that utilize the high micron-scale resolution achievable with optics,results of biomechanical properties were obtained from biological tissues.The results suggest potential diagnostic and therapeutic clinical applications.Results from these studies also help our understanding of the relationship between biomechanical variations and functional tissue changes in biological systems.展开更多
A portable analog lock-in amplifier capable of accurate phase detection is proposed in this paper. The proposed lock-in amplifier, which uses the dual-channel orthometric signals as the references to build the xy coor...A portable analog lock-in amplifier capable of accurate phase detection is proposed in this paper. The proposed lock-in amplifier, which uses the dual-channel orthometric signals as the references to build the xy coordinate system, can detect the relative phase between the input and x-axis based on trigonometric function. The sensitivity of the phase measurement reaches 0.014degree, and a detection precision of 0.1 degree is achieved. At the same time, the performance of the lock-in amplifier is verified in the high precision optical oxygen concentration detection. Experimental results reveal that the portable analog lock-in amplifier is accurate for phase detection applications. In the oxygen sensing experiments, 0.058% oxygen concentration resulted in 0.1 degree phase shift detected by the lock-in amplifier precisely. In addition, the lock-in amplifier is small and economical compared with the commercial lock-in equipments, so it can be easily integrated in many portable devices for industrial applications.展开更多
文摘By using the theory of measured phase operator proposed by Barnett and Pegg, dynamic properties of the phase of a field are studied. The time evolution and squeezing of measured phase operators of a coherent field interacting with a two-level atom in the cavity with or without the Kerr medium are investigated. The influences of virtual cavity field on squeezing of measured phase operator are studied. Our numerical results show that the squeezing effects are clearly influenced by Kerr medium parameters, the field intensity, and the detuning. Moreover, the influence of the virtual-photon field makes more quantum noise in the evolution of measured phase operators. Key words Jaynes-Cummings model (JCM) - Kerr medium - measured phase operator - squeezing - virtual photon PACS 2001 4250Dv
文摘We study the higher order fluctuations and squeezing of quadrature operators in the squeezed thermal states. In terms of measured phase operators, we discuss the fluctuations and squeezing of phases in these states. We conclude that the condition of higher order squeezing for quadrature components of the field is order independent and the fluctuations of measured phase operators are temperature independent.
基金National Studying Abroad Foundation Management Commission of China!(No. 98822014)
文摘Using computer-controlled liquid crystal display (LCD) as an image processor and a CCD camera as a detector, phase-only correlation measurement is performed with the aid of joint transform correlation method (JTC). This computer -controlled LCD-CCD image processing system may be a powerful tool for defect detection, position control and pattern recognition. It enables new possibilities in analog real-time image processing. This is of great interest in microelectronic manufacturing today and in the future.
基金Supported by the National Natural Science Foundation of China under Grant No 61377102the Defense Industrial Technology Development Program under Grant No B1520133010
文摘Based on the frequency-to-time mapping relation of the linearly chirped pulse, the temporal phase shift induced by a laser-excited wake in a helium gas jet is measured using a chirped-pulse spectral interferometry with ～ 140 fs resolution over a temporal region of I ps in a single shot. In this measurement, the image of the wake is obtained with one-dimensional spatial resolution and temporal resolution limited only by the bandwidth and chirp of the pulse. The ＇bubbles＇ feature of the wake structure, along with multiple wakes excited by the main lobe and the side lobe of a laser focal-spot, is captured simultaneously.
基金Supported by the National Natural Science Foundation of China under Grant No 61205103
文摘We propose a simple iterative algorithm based on a temporally movable phase modulation process to retrieve the weak temporal phase of laser pulses. This unambiguous method can be used to achieve a high accuracy and to simultaneously measure the weak temporal phase and temporal profile of pulses, which are almost transform- limited. A detailed analysis shows that this iterative method has valuable potential applications in the charac- terization of pulses with weak temporal phase.
基金Supported by the National Natural Science Foundation of China under Grant No 11104091the Guangxi Key Laboratory of Information Materials of Guilin University of Electronic Technology under Grant No 1210908-05-K
文摘The magnetization behavior of a CuFeO2 single crystal grown by the floating zone technique is investigated with a pulsed high magnetic field. We observe a series of field-induced multi-step-like transitions with hysteresis, of which the critical magnetic fields are temperature-dependent and show anisotropy. By using a pulsed high magnetic field up to 75 T, the magnetization behavior shows that the critical transition magnetic fields of spin- flip/flop shift to lower field regions with an increase in temperature. According to the magnetization curves, a complete magnetic phase diagram is depicted.
文摘A new error compensating five sample phase shifting algorithm which is insensitive to phase shift error is proposed to retrieve the phase distribution of a fringe pattern. It includes two steps. First, the linear phase shift error is estimated using four sample images. Then, the phase distribution is calculated with error corrected by using the phase shift error estimated in the first step. As the equations of error estimation and phase calculation are simple, this new algorithm is practical as well as effective. Computer simulations were carried out to verify the effectiveness of the algorithm. Results of two other well known error compensating algorithms are also presented, which show the new algorithm is the least sensitive to phase shift error.
基金supported by the National Key R&D Program(No.2022YFA1602201)。
文摘This paper presents a new technique for measuring the bunch length of a high-energy electron beam at a bunch-by-bunch rate in storage rings.This technique uses the time–frequency-domain joint analysis of the bunch signal to obtain bunch-by-bunch and turn-by-turn longitudinal parameters,such as bunch length and synchronous phase.The bunch signal is obtained using a button electrode with a bandwidth of several gigahertz.The data acquisition device was a high-speed digital oscilloscope with a sampling rate of more than 10 GS/s,and the single-shot sampling data buffer covered thousands of turns.The bunch-length and synchronous phase information were extracted via offline calculations using Python scripts.The calibration coefficient of the system was determined using a commercial streak camera.Moreover,this technique was tested on two different storage rings and successfully captured various longitudinal transient processes during the harmonic cavity debugging process at the Shanghai Synchrotron Radiation Facility(SSRF),and longitudinal instabilities were observed during the single-bunch accumulation process at Hefei Light Source(HLS).For Gaussian-distribution bunches,the uncertainty of the bunch phase obtained using this technique was better than 0.2 ps,and the bunch-length uncertainty was better than 1 ps.The dynamic range exceeded 10 ms.This technology is a powerful and versatile beam diagnostic tool that can be conveniently deployed in high-energy electron storage rings.
文摘Using the Pegg-Barnett formalism we study the phase probability distributions and the squeezing effects of measured phase operators in the nonlinear coherent states introduced by R.L. de Matos Filho and W. Vogel to describe the center-of mass motion of a trapped ion and the q-coherent states. Moreover, we have obtained the completeness relation of nonlinear coherent states and proved that the q-Fock state \n>(q) introduced in many papers is, in fact, the usual Fock state.
基金supported by the National Natural Science Foundation of China(Grant Nos.11773060,11973074,U1831137 and 11703070)National Key Basic Research and Development Program(2018YFA0404702)+1 种基金Shanghai Key Laboratory of Space Navigation and Positioning(3912DZ227330001)the Key Laboratory for Radio Astronomy of CAS。
文摘In deep space exploration,many engineering and scientific requirements require the accuracy of the measured Doppler frequency to be as high as possible.In our paper,we analyze the possible frequency measurement points of the third-order phase-locked loop(PLL)and find a new Doppler measurement strategy.Based on this finding,a Doppler frequency measurement algorithm with significantly higher measurement accuracy is obtained.In the actual data processing,compared with the existing engineering software,the accuracy of frequency of 1 second integration is about 5.5 times higher when using the new algorithm.The improved algorithm is simple and easy to implement.This improvement can be easily combined with other improvement methods of PLL,so that the performance of PLL can be further improved.
基金National Natural Science Foundation of China(6127404361233010)Hunan Provincial Natural Science Fund for Distinguished Young Scholars(2015JJ1014)
文摘Based on the basic principle of Time-Of-Flight cameras,a novel MATLAB/SIMULINK model is proposed to measure phase delay of a modulated light signal which represents the distance from camera to object. Subsequently,by discussing influence factors of phase measurement,it is found that the integration time,the sampling time,and the aliasing effect have important effect on improving the accuracy of phase measurement. Interestingly,by analyzing different integration time and sampling time, it is found that the best integration time and sampling time are 0.05 ms and 10 ns,respectively. In this case(i.e.,in absence of the aliasing effect),the variation range of the distance error is between 1 mm and 11 mm in the interval of one period. Especially,under the consideration of the aliasing effect,the average value of distance error is half of that in absence of the aliasing effect. This improves the accuracy of the distance measurement greatly.
文摘The properties of measured phase operators in damped odd and even coherent states have been studied. The fluctuations associated with measured phase and their squeezing in these states are investigated. The phase properties in damped superposition coherent states are considered too with the help of measured phase operators. These fluctuations and their squeezing are affected by damping and evolve with time elapsing.
基金Supported by the Special Funds of the National Natural Science Foundation of China under Grant Nos.11247032 and 11247207the National Fundamental Research Program of China under Grant No.2010CB923104
文摘We propose an approach to detect an unknown quantum state of the atom(s) by measuring the phase shifts of the transmitted photons through a dispersively-coupled cavity. In the framework of the input-output theory, we derive the relations between the phase shifts of the transmitted photons and the states of the atom(s) in the cavity. It is shown that due to the dispersive interaction between the cavity and the atom(s), information about the atomic state can then be extracted by measuring the phase shifts of the transmitted photons through the cavity. The feasibility of the proposal is also discussed with the experimental parameters by numerical method.
文摘The design and realization of a new generation of infra-red electronic distance measurement (IR EDM) system are presented.A DSP(Digital Signal Process) phase detector based on high speed analog-to-digital converter and DSP technique has been designed,in order to improve the precision and reliability of IR EDM system.As a result,the EDM system developed with a DSP phase detector has a precision of 3 mm in the measuring range of 2 km.
基金supported by the National Hi-Tech Research and Development Program of China ("863" Project) (Grant No. 2007AA12Z323)the National Natural Science Foundation of China (Grant No. 60772139)
文摘Integrated profile is one of the basic characteristic of X-ray pulsar. Gaussian function fit is used to model the components of X-ray pulsar profile, and it is combined with Poisson distribution model of X-ray pulsar to analyze Cramer-Rao low bound （CRLB） of phase, phase rate estimation and relation between CRLB and profile components. Then, a time domain method using minimum entropy is proposed for profile phase and phase rate estimation, and its effectiveness is explained using simulation examples.
基金supported by the National Natural Science Foundation of China (60372061)Basic Fund for the Scientific Research Project of Jilin University (200903296)
文摘Different from the traditional way of using piezoelectric （PZT）phase shifter to measure phase difference, a new method is designed to calculate it between signals in the two arms of a homodyne fiber interferometer. A simple homodyne fiber interferometer system is then established to measure the interference photoeurrent and the photocurrents from the two fiber arms generated by the signal power on a temperature control plat. The homodyne fiber interferometer system is composed of fiber and sensitive to the variation of temperature. Thus, is necessary to study the temperature characteristics in the phase measurement of homodyne fiber interferometer. The experimental results show that the variation of the phase difference of signals in the two fiber arms is proportional to the variation of temperature.
基金Project supported by the National Natural Science Foundation of China(Grant No.61008038)
文摘Dispersed fringe sensor （DFS） is an important phasing sensor of next-generation optical astronomical telescopes. The measurement errors induced by the measurement noise of three piston estimation methods for the DFS including leastsquared fitting （LSF） method, frequency peak location （FPL） method and main peak position （MPP） method, are analyzed theoretically and validated experimentally in this paper. The experimental results coincide well with the theoretical analyses. The MPP, FPL, LSF are used respectively when the DFS operates with broadband light （central wavelength： 706 nm, bandwidth： 23 nm）. The corresponding root mean square （RMS） value of estimated piston error can be achieved to be 1 nm, 3 nm, 26 nm, respectively. Additionally, the range of DFS with the FPL can be more than 100 μm at the same time. The FPL method can work well both in coarse and fine phasing stages with acceptable accuracy, compared with LSF method and MPP method.
文摘The ambiguity resolution in the field of GPS is investigated in detail. A new algorithm to resolve the ambiguity is proposed. The algorithm first obtains the floating resolution of the ambiguity aided with triple difference measurement. Decorrelation of searching space is done by reducing the ambiguity covariance matrix＇s dimension to overcome the possible sick factorization of the matrix brought by Z-transformation. In simulation, the proposed algorithm is compared with least-squares ambiguity decorrelation adjustment （LAMBDA）. The result shows that the proposed algorithm is better than LAMBDA because of lesser resolving time, which approximately reduces 20% resolving time. Thus, the proposed algorithm adapts to the high dynamic real-time applications.
基金supported in part by grants from the National Institutes of Health(NIBIB,R21 EB005321,R01 EB005221,R01 EB009073NCI RC1 CA147096,S.A.B.).
文摘With the development of optical coherence tomography,the application optical coherence elastography(OCE)has gained more and more attention in biomechanics for its unique features including micron-scale resolution,real-time processing,and non-invasive imaging.In this review,one group of OCE techniques,namely dynamic OCE,are introduced and discussed including external dynamic OCE mapping and imaging of ex vivo breast tumor,external dynamic OCE measurement of in vivo human skin,and internal dynamic OCE including acoustomotive OCE and magnetomotive OCE.These techniques overcame some of the major drawbacks of traditional static OCE,and broadened the OCE application fields.Driven by scientific needs to engineer new quantitative methods that utilize the high micron-scale resolution achievable with optics,results of biomechanical properties were obtained from biological tissues.The results suggest potential diagnostic and therapeutic clinical applications.Results from these studies also help our understanding of the relationship between biomechanical variations and functional tissue changes in biological systems.
文摘A portable analog lock-in amplifier capable of accurate phase detection is proposed in this paper. The proposed lock-in amplifier, which uses the dual-channel orthometric signals as the references to build the xy coordinate system, can detect the relative phase between the input and x-axis based on trigonometric function. The sensitivity of the phase measurement reaches 0.014degree, and a detection precision of 0.1 degree is achieved. At the same time, the performance of the lock-in amplifier is verified in the high precision optical oxygen concentration detection. Experimental results reveal that the portable analog lock-in amplifier is accurate for phase detection applications. In the oxygen sensing experiments, 0.058% oxygen concentration resulted in 0.1 degree phase shift detected by the lock-in amplifier precisely. In addition, the lock-in amplifier is small and economical compared with the commercial lock-in equipments, so it can be easily integrated in many portable devices for industrial applications.
