Structured illumination microscopy(SIM)is one of the most widely applied wide field super resolution imaging techniques with high temporal resolution and low phototoxicity.The spatial resolution of SIM is typically li...Structured illumination microscopy(SIM)is one of the most widely applied wide field super resolution imaging techniques with high temporal resolution and low phototoxicity.The spatial resolution of SIM is typically limited to two times of the diffraction limit and the depth of field is small.In this work,we propose and experimentally demonstrate a low cost,easy to implement,novel technique called speckle structured illumination endoscopy(SSIE)to enhance the resolution of a wide field endoscope with large depth of field.Here,speckle patterns are used to excite objects on the sample which is then followed by a blind-SIM algorithm for super resolution image reconstruction.Our approach is insensitive to the 3D morphology of the specimen,or the deformation of illuminations used.It greatly simplifies the experimental setup as there are no calibration protocols and no stringent control of illumination patterns nor focusing optics.We demonstrate that the SSIE can enhance the resolution 2–4.5 times that of a standard white light endoscopic(WLE)system.The SSIE presents a unique route to super resolution in endoscopic imaging at wide field of view and depth of field,which might be beneficial to the practice of clinical endoscopy.展开更多
Three-dimensional(3D)lidar has been widely used in various fields.The MEMS scanning system is one of its most important components,while the limitation of scanning angle is the main obstacle to improve the demerit for...Three-dimensional(3D)lidar has been widely used in various fields.The MEMS scanning system is one of its most important components,while the limitation of scanning angle is the main obstacle to improve the demerit for its application in various fields.In this paper,a folded large field of view scanning optical system is proposed.The structure and parameters of the system are determined by theoretical derivation of ray tracing.The optical design software Zemax is used to design the system.After optimization,the final structure performs well in collimation and beam expansion.The results show that the scan angle can be expanded from±5°to±26.5°,and finally the parallel light scanning is realized.The spot diagram at a distance of 100 mm from the exit surface shows that the maximum radius of the spot is 0.506 mm with a uniformly distributed spot.The maximum radius of the spot at 100 m is 19 cm,and the diffusion angle is less than 2 mrad.The energy concentration in the spot range is greater than 90%with a high system energy concentration,and the parallelism is good.This design overcomes the shortcoming of the small mechanical scanning angle of the MEMS lidar,and has good performance in collimation and beam expansion.It provides a design method for large-scale application of MEMS lidar.展开更多
Image quality in positron emission tomography(PET)is affected by random and scattered coincidences and reconstruction protocols.In this study,we investigated the effects of scattered and random coincidences from outsi...Image quality in positron emission tomography(PET)is affected by random and scattered coincidences and reconstruction protocols.In this study,we investigated the effects of scattered and random coincidences from outside the field of view(FOV)on PET image quality for different reconstruction protocols.Imaging was performed on the Discovery 690 PET/CT scanner,using experimental configurations including the NEMA phantom(a body phantom,with six spheres of different sizes)with a signal background ratio of 4:1.The NEMA phantom(phantom I)was scanned separately in a one-bed position.To simulate the effect of random and scatter coincidences from outside the FOV,six cylindrical phantoms with various diameters were added to the NEMA phantom(phantom II).The 18 emission datasets with mean intervals of 15 min were acquired(3 min/scan).The emission data were reconstructed using different techniques.The image quality parameters were evaluated by both phantoms.Variations in the signal-to-noise ratio(SNR)in a 28-mm(10-mm)sphere of phantom II were 37.9%(86.5%)for ordered-subset expectation maximization(OSEM-only),36.8%(81.5%)for point spread function(PSF),32.7%(80.7%)for time of flight(TOF),and 31.5%(77.8%)for OSEM+PSF+TOF,respectively,indicating that OSEM+PSF+TOF reconstruction had the lowest noise levels and lowest coefficient of variation(COV)values.Random and scatter coincidences from outside the FOV induced lower SNR,lower contrast,and higher COV values,indicating image deterioration and significantly impacting smaller sphere sizes.Amongst reconstruction protocols,OSEM+PSF+TOF and OSEM+PSF showed higher contrast values for sphere sizes of 22,28,and 37 mm and higher contrast recovery coefficient values for smaller sphere sizes of 10 and 13 mm.展开更多
The high-altitude detection of astronomical radiation(HADAR)experiment is a new Cherenkov observation technique with a wide field of view(FoV),aimed at observing the prompt emissions ofγ-ray bursts(GRBs).The bottlene...The high-altitude detection of astronomical radiation(HADAR)experiment is a new Cherenkov observation technique with a wide field of view(FoV),aimed at observing the prompt emissions ofγ-ray bursts(GRBs).The bottleneck for this type of experiment can be found in determining how to reject the high rate of nightsky background(NSB)noise from random stars.In this work,we propose a novel method for rejecting noise,which considers the spatial properties of GRBs and the temporal characteristics of Cherenkov radiation.In space coordinates,the map between the celestial sphere and the fired photomultiplier tubes(PMTs)on the telescope's camera can be expressed as f(δ(i,j))=δ'(i',j'),which means that a limited number of PMTs is selected from one direction.On the temporal scale,a 20-ns time window was selected based on the knowledge of Cherenkov radiation.This allowed integration of the NSB for a short time interval.Consequently,the angular resolution and effective area at 100 GeV in the HADAR experiment were obtained as 0.2°and 10^(4)m^(2),respectively.This method can be applied to all wide-FoV experiments.展开更多
The laser beam divergence angle is one of the important parameters to evaluate the quality of the laser beam.It can not only accurately indicate the nature of the beam divergence when the laser beam is transmitted ove...The laser beam divergence angle is one of the important parameters to evaluate the quality of the laser beam.It can not only accurately indicate the nature of the beam divergence when the laser beam is transmitted over a long distance,but also objectively evaluate the performance of the laser system.At present,lidar has received a lot of attention as a core component of environment awareness technology.Micro-electromechanical system(MEMS)micromirror has become the first choice for three-dimensional imaging lidar because of its small size and fast scanning speed.However,due to the small size of the MEMS micromirror,the lidar scanning system has a small field of view(FOV).In order to achieve a wide range of scanning imaging,collimating optical system and wide-angle optical system are generally added to the system.However,due to the inherent properties of the optical lens,it is impossible to perfect the imaging,so the effects of collimating and expanding the beam will be different at different angles.This article aims to propose a measurement system that dynamically measures the divergence angles of MEMS scanning lidar beams in different fields of view to objectively evaluate the performances of scanning lidar systems.展开更多
The methods of estimating the minimum allowed value of IFOV (instantaneous field of view) of the detector in a rosette scan system are investigated. The common method for the estimation of IFOV is described. A new met...The methods of estimating the minimum allowed value of IFOV (instantaneous field of view) of the detector in a rosette scan system are investigated. The common method for the estimation of IFOV is described. A new method which uses the maximum distance between two neighboring petals as the estimated value of IFOV is developed and a comparison between the common method and the new method is given. It is concluded that the minimum allowed value of IFOV of rosette scanning is over estimated by the common method while this value can be calculated accurately with the new method.展开更多
In this paper, an autonomous orbit determination method for satellite using a large field of view star sensor is presented. The simulation of orbit under atmospheric drag perturbation are given with expanded Kalman fi...In this paper, an autonomous orbit determination method for satellite using a large field of view star sensor is presented. The simulation of orbit under atmospheric drag perturbation are given with expanded Kalman filtering. The large field of view star sensor has the same precision as star sensor and a sufficient filed of view. Therefore ,the refraction stars can be observed more accurately in real time. The geometric relation between the refracted starlight and the earth can be determined by tangent altitude of the refraction starlight. And then the earth center can be determined in satellite body frame. The simulation shows that the precision of the mean square deviation of satellite’s position and velocity is 5m and 0.01m/s respectively. The calculated decrement of the semi-major axis in one day is close to the theoretical result, and the absolute error is in the range of decimeter when the altitude of orbit is 750 km. The simu- lateion of orbit of different initial semi-major axis shows that the higher the altitude of orbit is, the smaller the dec- rement of the semi-major axis is, and when the altitude of orbit is 1700 km the decimeter of the semi-major axis is 10-7 km.展开更多
In the past three decades,laser warning systems(LWS)have emerged in great importance,as the development of laser-guided weapons,such as airborne Hellfire missiles,has increased,posing an imminent threat to vital areas...In the past three decades,laser warning systems(LWS)have emerged in great importance,as the development of laser-guided weapons,such as airborne Hellfire missiles,has increased,posing an imminent threat to vital areas and VIPs.The laser warning station(LWS)can detect,classify,identify,and give alarm from laser threat at a very short time with high sensitivity.Therefore,the designers of this system must take into account the detectability and field of view to cover the area to be secured.The main contribution in this research is an analytical design of LWS that consists of 24 detector elements,distributed in two arrays(2×12)circularly.Also,calculating the best distance between the detectors according to the laser beam spot size.In addition,enhancement laser warring sensor detection capability and detection performance FOV between the detectors to increase coverage area up to 360°.Moreover,decreasing dead zone area between the laser detectors element.Mathematical calculations and illustrations made to reach the best systematic design.展开更多
基金partially supported by the Gordon and Betty Moore Foundation Grant No.5722
文摘Structured illumination microscopy(SIM)is one of the most widely applied wide field super resolution imaging techniques with high temporal resolution and low phototoxicity.The spatial resolution of SIM is typically limited to two times of the diffraction limit and the depth of field is small.In this work,we propose and experimentally demonstrate a low cost,easy to implement,novel technique called speckle structured illumination endoscopy(SSIE)to enhance the resolution of a wide field endoscope with large depth of field.Here,speckle patterns are used to excite objects on the sample which is then followed by a blind-SIM algorithm for super resolution image reconstruction.Our approach is insensitive to the 3D morphology of the specimen,or the deformation of illuminations used.It greatly simplifies the experimental setup as there are no calibration protocols and no stringent control of illumination patterns nor focusing optics.We demonstrate that the SSIE can enhance the resolution 2–4.5 times that of a standard white light endoscopic(WLE)system.The SSIE presents a unique route to super resolution in endoscopic imaging at wide field of view and depth of field,which might be beneficial to the practice of clinical endoscopy.
基金the Shenzhen Fundamental Research Program(Grant No.JCYJ2020109150808037)the National Key Scientific Instrument and Equipment Development Projects of China(Grant No.62027823)the National Natural Science Foundation of China(Grant No.61775048)。
文摘Three-dimensional(3D)lidar has been widely used in various fields.The MEMS scanning system is one of its most important components,while the limitation of scanning angle is the main obstacle to improve the demerit for its application in various fields.In this paper,a folded large field of view scanning optical system is proposed.The structure and parameters of the system are determined by theoretical derivation of ray tracing.The optical design software Zemax is used to design the system.After optimization,the final structure performs well in collimation and beam expansion.The results show that the scan angle can be expanded from±5°to±26.5°,and finally the parallel light scanning is realized.The spot diagram at a distance of 100 mm from the exit surface shows that the maximum radius of the spot is 0.506 mm with a uniformly distributed spot.The maximum radius of the spot at 100 m is 19 cm,and the diffusion angle is less than 2 mrad.The energy concentration in the spot range is greater than 90%with a high system energy concentration,and the parallelism is good.This design overcomes the shortcoming of the small mechanical scanning angle of the MEMS lidar,and has good performance in collimation and beam expansion.It provides a design method for large-scale application of MEMS lidar.
基金supported by the Tehran University of Medical Sciences under Grant No.36291PET/CT and Cyclotron Center of Masih Daneshvari Hospital at Shahid Beheshti University of Medical Sciences。
文摘Image quality in positron emission tomography(PET)is affected by random and scattered coincidences and reconstruction protocols.In this study,we investigated the effects of scattered and random coincidences from outside the field of view(FOV)on PET image quality for different reconstruction protocols.Imaging was performed on the Discovery 690 PET/CT scanner,using experimental configurations including the NEMA phantom(a body phantom,with six spheres of different sizes)with a signal background ratio of 4:1.The NEMA phantom(phantom I)was scanned separately in a one-bed position.To simulate the effect of random and scatter coincidences from outside the FOV,six cylindrical phantoms with various diameters were added to the NEMA phantom(phantom II).The 18 emission datasets with mean intervals of 15 min were acquired(3 min/scan).The emission data were reconstructed using different techniques.The image quality parameters were evaluated by both phantoms.Variations in the signal-to-noise ratio(SNR)in a 28-mm(10-mm)sphere of phantom II were 37.9%(86.5%)for ordered-subset expectation maximization(OSEM-only),36.8%(81.5%)for point spread function(PSF),32.7%(80.7%)for time of flight(TOF),and 31.5%(77.8%)for OSEM+PSF+TOF,respectively,indicating that OSEM+PSF+TOF reconstruction had the lowest noise levels and lowest coefficient of variation(COV)values.Random and scatter coincidences from outside the FOV induced lower SNR,lower contrast,and higher COV values,indicating image deterioration and significantly impacting smaller sphere sizes.Amongst reconstruction protocols,OSEM+PSF+TOF and OSEM+PSF showed higher contrast values for sphere sizes of 22,28,and 37 mm and higher contrast recovery coefficient values for smaller sphere sizes of 10 and 13 mm.
基金supported by the Key R&D Program of Sichuan Province (Nos. 2019ZYZF0001 and 2020YFSY0016)the National Natural Science Foundation of China (Nos. 11873005,12047575, 11705103, 11635011, U1831208, U1632104, 11875264U2031110)
文摘The high-altitude detection of astronomical radiation(HADAR)experiment is a new Cherenkov observation technique with a wide field of view(FoV),aimed at observing the prompt emissions ofγ-ray bursts(GRBs).The bottleneck for this type of experiment can be found in determining how to reject the high rate of nightsky background(NSB)noise from random stars.In this work,we propose a novel method for rejecting noise,which considers the spatial properties of GRBs and the temporal characteristics of Cherenkov radiation.In space coordinates,the map between the celestial sphere and the fired photomultiplier tubes(PMTs)on the telescope's camera can be expressed as f(δ(i,j))=δ'(i',j'),which means that a limited number of PMTs is selected from one direction.On the temporal scale,a 20-ns time window was selected based on the knowledge of Cherenkov radiation.This allowed integration of the NSB for a short time interval.Consequently,the angular resolution and effective area at 100 GeV in the HADAR experiment were obtained as 0.2°and 10^(4)m^(2),respectively.This method can be applied to all wide-FoV experiments.
基金Project supported by the National Key Scientific Instrument and Equipment Development Projects of China(Grant No.62027823)the Shenzhen Fundamental Research Program(Grant No.JCYJ2020109150808037)the National Natural Science Foundation of China(Grant No.61775048)。
文摘The laser beam divergence angle is one of the important parameters to evaluate the quality of the laser beam.It can not only accurately indicate the nature of the beam divergence when the laser beam is transmitted over a long distance,but also objectively evaluate the performance of the laser system.At present,lidar has received a lot of attention as a core component of environment awareness technology.Micro-electromechanical system(MEMS)micromirror has become the first choice for three-dimensional imaging lidar because of its small size and fast scanning speed.However,due to the small size of the MEMS micromirror,the lidar scanning system has a small field of view(FOV).In order to achieve a wide range of scanning imaging,collimating optical system and wide-angle optical system are generally added to the system.However,due to the inherent properties of the optical lens,it is impossible to perfect the imaging,so the effects of collimating and expanding the beam will be different at different angles.This article aims to propose a measurement system that dynamically measures the divergence angles of MEMS scanning lidar beams in different fields of view to objectively evaluate the performances of scanning lidar systems.
文摘The methods of estimating the minimum allowed value of IFOV (instantaneous field of view) of the detector in a rosette scan system are investigated. The common method for the estimation of IFOV is described. A new method which uses the maximum distance between two neighboring petals as the estimated value of IFOV is developed and a comparison between the common method and the new method is given. It is concluded that the minimum allowed value of IFOV of rosette scanning is over estimated by the common method while this value can be calculated accurately with the new method.
基金Project CXJJ-84 supported by Science and Technology Innovation Foundation of Chinese Academy of Science
文摘In this paper, an autonomous orbit determination method for satellite using a large field of view star sensor is presented. The simulation of orbit under atmospheric drag perturbation are given with expanded Kalman filtering. The large field of view star sensor has the same precision as star sensor and a sufficient filed of view. Therefore ,the refraction stars can be observed more accurately in real time. The geometric relation between the refracted starlight and the earth can be determined by tangent altitude of the refraction starlight. And then the earth center can be determined in satellite body frame. The simulation shows that the precision of the mean square deviation of satellite’s position and velocity is 5m and 0.01m/s respectively. The calculated decrement of the semi-major axis in one day is close to the theoretical result, and the absolute error is in the range of decimeter when the altitude of orbit is 750 km. The simu- lateion of orbit of different initial semi-major axis shows that the higher the altitude of orbit is, the smaller the dec- rement of the semi-major axis is, and when the altitude of orbit is 1700 km the decimeter of the semi-major axis is 10-7 km.
文摘In the past three decades,laser warning systems(LWS)have emerged in great importance,as the development of laser-guided weapons,such as airborne Hellfire missiles,has increased,posing an imminent threat to vital areas and VIPs.The laser warning station(LWS)can detect,classify,identify,and give alarm from laser threat at a very short time with high sensitivity.Therefore,the designers of this system must take into account the detectability and field of view to cover the area to be secured.The main contribution in this research is an analytical design of LWS that consists of 24 detector elements,distributed in two arrays(2×12)circularly.Also,calculating the best distance between the detectors according to the laser beam spot size.In addition,enhancement laser warring sensor detection capability and detection performance FOV between the detectors to increase coverage area up to 360°.Moreover,decreasing dead zone area between the laser detectors element.Mathematical calculations and illustrations made to reach the best systematic design.
