Chinese Version Light学术出版中心
Latest Issue
Issue 1 ， 2008
-
Experimental Study on Quantum Efficiency of a Microchannel Plate in 12nm～40nm
Abstract：In order to measuring the quantum efficiency (QE) of a microchannel plate (MCP), a method advanced was to measure the current transmited from the MCP indirectly by measuring the voltage directly. The Extreme Ultraviolet radiation was firstly calibrated by a transferred standard detector and then illuminated the MCP, the current from the MCP was measured and the QE of the MCP was compputed in 12nm～40nm. The rusult indicated that the value of the QE was from 2% to 12.3% in above wave band and dropping with increasing wavelength. Finally, the reason making the QE low was analyzed.- 21
- |
- 6
- |
- 8
Published：2020-08-12 -
Application of BP Neural Networks in Non—linearity Correction of optical tweezers
Abstract：Optical tweezers is the probe studied weak force measurement， Measurement Range and Measurement Accuracy of force are important index of the system of optical tweezers. BP optimizations for neural networks to correct the non—linearity of calibration of the force of optical trap are provided in this paper． The range of measurement of the system of optical tweezers of data is improved without increasing the complexity of hardware. With the comparison of BP method and curve fitting method, it is presented that the nonlinear correction method based on neural network has high measurement precision. Experimental results of Nano-Optical-Tweezers system show that in such a way, the performance of the system is effectively improved.Keywords：optical tweezers ；BP neural networks；non—linearity Correction；- 54
- |
- 5
- |
- 6
Published：2020-08-12 -
LD pumped intracavity frequency doubled Nd:YAG/LBO laser of 473nm with low noise operation
Abstract：Lager amplitude fluctuations of output power at high-frequency are observed in laser-diode pumped intracavity frequency-doubled Nd:YAG/LBO blue laser of 473nm without special intracavity elements .This is called the “Blue problem” which seriously restrict the development and applications of the blue laser of 473nm in many fields . To suppression the high-frequency noise of frequency-doubled output of the blue laser , method of decrease reabsorption losses in quasi-three-level laser system through increase intracavity circulating intensity of fundamental wave and decrease length of laser crystal was used . Two LD of 2W as pumped source and a Nd:YAG crystal of 1.0mm length were used in experiment . Blue laser of output power at 195mW with low noise operation was obtained by intracavity doubling through LBO material of 10mm length . Experiment indicated that the (peak-peak)/mean value of frequency-doubled output power of the blue laser are lower than 1% . Not any hopping of output power of the laser are observed in 1h and not any intracavity elements to control state of longitudinal mode are introduced .Keywords：Intracavity frequency doubled laser;Noise;quasi-three-level;Reabsorption losses- 40
- |
- 6
- |
- 5
Published：2020-08-12 -
Research on rapid detection and influence regularity of subsurface damage of optical materials in lapping process
Abstract：Subsurface damage (SSD) generated in lapping process directly influences service performances of optical elements, which must be entirely removed in the following polishing process, however, the rapid inspection of SSD is unresolved for it is covered under surface. For the purpose of rapid, accurate, and non-destructive measurement of SSD produced in lapping process, a theoretical model of relationship between SSD and surface roughness (SR) was established through investigating median and lateral crack system in brittle surface induced by sharp indenter, and contribution of elastic stress field to the median crack propagation was also considered in the loading cycle. SSD depth of lapped K9 glass was measured by magnetorheological finishing (MRF) spot technique, in order to verify the validity of the relationship model. Finally, influences of lapping parameters on SSD depth were investigated experimentally, then, an effective lapping procedure was proposed in order to improve the machining efficiency of optical elements. The results show that there exists monotone increasing non-linear correlation between SSD depth and SR in optical lapping process, power of the power function is 4/3. Moreover, the influence of granularity of abrasive grains on SSD depth is more significant than lapping plate hardness, and the influence of lapping pressure and lapping plate revolution velocity can be neglected.Keywords：Subsurface damage (SSD);Indentation;optical materials;lapping;Magnetorheological Finishing (MRF)- 55
- |
- 16
- |
- 20
Published：2020-08-12 -
A new Technology for Lightweight large Primary Mirror of Theodolite
Abstract：In order to optimize conceptual lightweight structure for 2m aperture theodolite primary mirror, according minimum flexibility principle, the papers optimizes conceptual lightweight structure with FEA topology method. From the computation result, major remain radial is close for different mirror material, in which the outside radial is 889.5mm, the inner is 235mm, the middle radial places are 720-730mm, 620-630mm; the mean lightweight rate of non-circular type is about 70%, the circular is to 50%. From optimization data of Zerodur mirror, natural frequency comes to 300Hz, location reaction force declines largely relatively. Comparing the deformation of SiC mirror surface with uniform lightweight structure, the displacement of non-uniform circular structure and close hexagon structure is close to 0.42-0.45e-5mm, while the uniform circular and open hexagon is 0.58-0.59e-5mm; and the natural frequency of uniform distribution circular is 1200Hz, while the non-uniform is 1680Hz, and the hexagon 1620-1670Hz. We get the conclusion, for the gravity load on mirror surface distributes nonlinear, the distribution of lightweight structure is uniform, which helps to control mirror surface deformation and natural frequency , to referent to lightweight design.Keywords：primary mirror of theodolit;lightweight;FEA topology method;deformation;natural frequency;nonlinear distribution- 53
- |
- 5
- |
- 2
Published：2020-08-12 -
Optical design of Large Aperture Segmented Mirror system
Abstract：based on the aberration balance of Three-Mirror-Anastigmatic (TMA), a kind of segmented optical design way is introduced, with long focal length, wide field of view (FOV). Segmented system is completely simulated and analyzed by using the way of Fresnel diffraction integral for the exit pupil wavefront; the initial design is modified result from the error analysis and distribution of non-sequential surface; the high order asphere & bigger aperture system is optimized to balance the aberration and make the system more redundancy. A segmented synthetic aperture optical system is designed, whose primary mirror is segmented, EFL 44m, f/8, 0.6°×0.06° FOV. Iterating the design scheme and error analysis, a good design is obtained.Keywords：optical design;segmented mirror;error analysis;non-sequential surface;space telescope- 34
- |
- 8
- |
- 7
Published：2020-08-12 -
Study on Supersmooth Surface Polishing Process Technology for Zerodur Based on HHT
Abstract：In order to obtain high quality supersmooth surface of zerodur, a sophisticated supersoomth surface polishing method—stable eccentric immersed polishing was adopted. Firstly, the property and microstructure of zerodur were analysed, and the technical condition for supersoomth surface polishing was proposed. Secondly, the principle and technical process of the polishing method were discussed. By this polishing technology, the sub-nano scale supersmooth surface of zerodur was successfully and stably obtained. Roughness reached to Ra0.3nm. Lastly, through the transform from roughness curve to Hilbert spectrum, the effects between polishing technological parameters and surface roughness were found. The results show that, the adoption of HHT for the measurement and evaluation of supersmooth surface can provide effective instruction to the practical polishing process, and redounds to obtain high quality supersmooth surface.- 29
- |
- 6
- |
- 4
Published：2020-08-12 -
The Study of 30.4nm Filter in the Normal Incidence Imager
Abstract：The multilayer mirrors are primary reflectors used in the normal incidence telescope for 30.4nm radiation, but they also have very high reflectivity in ultraviolet, visible light and near infrared wave band, therefore it is very necessary to use some special filter to remove these longer radiations. It is important for the performance of filter to select proper material and thickness. Confirm that aluminum is the best material for 30.4nm filter by computing the linear absorption coefficient for several kinds of materials as a function of wavelength based on atomic scattering factor. And considering the transmission and hardness, the filter’s thickness is decided. Improved the spectrum measurement instrument made of Mcpherson model 247 grazing incidence monochromator and gas hollow cathode source, it is fit for transmission measurement and the wavelength scanning error is ±0.17Å~±0.97Å .Measured the prepared filter’s transmission range from 25.6nm to 1000 nm using it，the result shows its transmission is 58.85% at 30.4 nm. It is demonstrated that the filter can be used in the 30.4nm imaging system since the further measurement dedicates it can prevent UV、visible and near infrared light effectively.Keywords：EUV Filter;Linear-absorbtion-coefficiency;Reflectance;Transmission;Monochromator- 21
- |
- 4
- |
- 2
Published：2020-08-12 -
Research on application of femtosecond laser multi-focus on parallel fabrication
Abstract：The femtosecond laser often makes parallel fabrication via multi-beam, which is split by the beam splitters. This ordinary method can not control the fabricated parallel outcomes flexibly in practical application. In this article, the parallel fabrication of micro waveguides is realized by controlling the multi-focus of femtosecond laser in optical media. The controlling factors which affect the fabrication are summarized. And the mechanism and factors are theoretically analyzed. This method is relatively flexible on the controlling of the parallel fabricating, because it doesn’t depend on any beam splitters. This fabrication method brings forward a revolutionary way of the parallel fabrication of femtosecond laser.Keywords：femtosecond laser;multi-focus;parallel fabrication;optical-waveguide- 30
- |
- 7
- |
- 3
Published：2020-08-12 -
Study on pulsed phase analysis of depth measurement for infrared thermal wave nondestructive evaluation
Abstract：In order to realize the defects’ depth measurement in the infrared thermal wave nondestructive evaluation, pulse phase thermography was introduced. Pulse phase method analyzes pulse data by Fourier transform to temporal signals, and measure the depth according to the relation of thermal wave’s frequency to conduction depth. In this paper, the experimental result of Al flat bottom holes sample is obtained by phase curves in Matlab and thermographs in VC++ under different frequencies. The initial result shows the theoretical depth and factual depth has d≈1.98μ , and pulse phase infrared thermography is an assistant way for subsurface defects detection of material and structure.Keywords：pulse phase thermography;Fourier transform;infrared thermal wave;blind frequency- 47
- |
- 7
- |
- 11
Published：2020-08-12 -
Relative luminance and VUV excitation spectra measurement for PDP phosphors
Abstract：Abstract：Emission spectra, relative luminance and excitation spectra characteristics are important factors in the field of phosphors research. Measurement of emission spectra is relative simple, its precision and repeatability can be ensured within 1% more easily, but relative luminance and excitation spectra is difficult to have precision and repeatability of 1% affected by test method. In this article, one method that phosphors surface diffuse reflection intensity is measured to improve relative quantum efficiency accuracy of phosphors for PDP in UV-VUV range between 120nm to 300nm, the relative quantum efficiency measuring precision is below 1% and the comparative subtle excitation spectrum curve is obtained, the spectra resolution is 1nm. At last, the measurement of excitation spectrum of (BaMgAl10O17：Eu) blue phosphors and (LaPO4:Tb,LaPO4:CeTb ,YPO4：Tb )three green phosphors is taken.Keywords：phosphors;relative luminance;VUV excitation spectra- 52
- |
- 6
- |
- 4
Published：2020-08-12 -
A Study on Focal Depth characteristic of Hybrid Refractive-Diffractive Element with Long Focal Depth
Abstract：In order to know the ability of the hybrid refractive-diffractive element for extending focal depth, the logarithmic phase function based on uniform-intensity principle is analyzed and the relationship is set up between focal depth, optical f/# and fabrication parameters of the hybrid refractive-diffractive element with logarithmic phase function. The simulation analysis of on-axis intensity distribution of the element is performed based on Fresnel diffraction formula with different parameters. Simulation results indicate that for determinate focal length and wavelength, the factor in focal depth compared with same f/# spherical refractive lens is determined by profile depth of diffractive element: when the profile depth is increased, the factor is larger and the on-axis intensity distribution in focal depth offers great uniform characters. For determinate focal depth value, when the optical f/# is decreased, the uniform character of on-axis intensity distribution in focal depth is better.Keywords：focal depth;hybrid refractive diffractive optical element;element with long focal depth- 46
- |
- 12
- |
- 1
Published：2020-08-12 -
Modeling and simulation of piezoelectric cantilever generators
Abstract：To enhance the energy-generating capability of a piezoelectric cantilever generator with given dimensions, the analysis models were established to simulate the influence of the exciting method , structural parameters as well as material properties of the piezoelectric cantilevers on energy generation. The research results show that there are different optimal thickness ratio (OTR) for the piezoelectric monomorph cantilever generator (PMCG) and piezoelectric bimorph cantilever generator (PBCG) to obtain maximal electrical energy using the same dimension and excitation, and the maximal energy generated from the PBCG is about 2 times that from the PMCG. With the increasing of the Young’s modulus ratio (YMR), the OTRs of the two generators all decrease. When aluminum and molybdenum plates are used for substrate, the PBCG and PMCG achieve the OTR of (0.7,0.32) and (0.45,0.2), respectively. With the same thickness ratio (0.5) and external excitation, YMR exerts different influence on energy generation of the two generators, and the PBCG generates more electrical energy than the PMCG when YMR is under 3.3.- 39
- |
- 5
- |
- 57
Published：2020-08-12 -
Measurement modeling for 6-DOF parallel-link coordinate measuring machinebased on particle swarm optimization
Abstract：In order to get forward position (measurement model) of a 6-DOF (six-degrees-of-freedom) parallel-link coordinate measuring machine (CMM), and overcome the shortcomings of numerical method that the accuracy for the forward kinematics can be influenced easily by the selection of the initial values, an unconstrained optimization model is established and the particle swarm optimization (PSO) algorithm is used for optimizing the model. The unconstrained optimization model of a 6-DOF parallel-link CMM for forward position based on the inverse position model of parallel-link mechanism which is presented. The PSO algorithm is used for solving the optimization problem, and then the forward position can be obtained. The simulation results indicate that 80 particles’ operation precision is about 0.5μm by the 55 times’ operations and the average time is about 3s. The PSO algorithm has the higher speed of calculation and the higher precision for measurement modeling and solution of parallel-link CMM.Keywords：Parallel-link CMM;Measurement modeling;Particle swarm optimization;Inverse kinematics;forward kinematics- 52
- |
- 8
- |
- 7
Published：2020-08-12 -
Research on Inertial Piezoelectric Rotary Actuator Based on Changing Positive Pressure
Abstract：Based by controlling the orderly changes of the PZT moving mechanism and positive pressure between supporting faces in mechanical way, a novel kind of inertial piezoelectric rotary actuator is proposed. Structure models of the rotary actuator is designed, the moving principle is analyzed, the prototype of new inertial piezoelectric rotary actuator is designed and manufactured, the performance of the actuator is tested，the dynamic formulation of inertial actuator is established, by using matlab software, the kinetic simulation of the actuator is carried out, the displacement and speed simulation curve of the actuator is conducted, the structure of newly inertial actuator is designed and manufactured. The motion theory and dynamic formulation of the actuator are proved through comparing the results of simulation and experiment。Keywords：piezoelectricity;inertial drive;friction;rotary;microactuator- 25
- |
- 4
- |
- 1
Published：2020-08-12 -
Application of FEA to coronary stent design
Abstract：OBJECTIVE:the shortage ratio and dogboning ratio of the new style stent expanded were calculated to determine whether the strcture is reasonable.METHOD:the unrestricted stent was expanded in FEA software ANSYS9.0,the technology of finite element analysis of stent expansion from its initial status including geometry modeling、material selection、meshing、boundary conditions、loads definition in the condition which interacting stent、artery and plaque that unconsidered was studied. RESULTS:The shortage ratio and dog boning ratio of stent calculated based on the FEM results were separately 10.9% and 2.57%. To validate the simulation, a real stent was expanded; the experiment proved the error between the real expansion result and the finite element analysis result were separately 0.3%and1.32%.. CONCLUSION: the expanded stent was uniformity ,the structure designed is correct. Using finite element to simulate the coronary stent was feasible, which could help the design and use of the stent. Keywords: Coronary stent finite element analysis expansiKeywords：Coronary stent;finite element analysis;expansion- 45
- |
- 6
- |
- 4
Published：2020-08-12 -
Power-supply performance of a piezoelectric generator for remote controls
Abstract：A piezoelectric electrical-energy generator was presented to provide endless and real-time electrical energy for remote controls. In view of the operation method and load performance of remote controls, pulse-excitation and press- excitation were utilized to impulse a piezoelectric cantilever generator to generate electrical energy. The influence of the two exciting methods on electrical energy generation and effective duration of power supply (EDPS) to constant current load was investigated experimentally. The results show that the piezoelectric generator achieves more electric energy and longer EDPS under pulse-excitation than that under press-excitation. When pulse-excitation is used, the EDPS decreases with the increasing of the current load, and there is an optimal natural frequency for the piezoelectric generator to achieve the longest EDPS. The electrical energy from the piezoelectric generator measured 40x15x0.5mm is available for a car remote control to sent signals successfully, and the information-transfer distance is up to 15m.Keywords：piezoelectric;electrical-energy generator;remote control;power supply- 76
- |
- 5
- |
- 6
Published：2020-08-12 -
The Application of Adaptive Angle-rate Estimator in The Gimbal of MGCMG
Abstract：Considering that the high accuracy moment output of magnetically suspended control moment gyroscope (MSCMG) depends on high accuracy moment output of gimbal, high accuracy opto-electric encoder or resolver is desired for position control. To eliminate the noise produced by the difference calculation of position signal, an adaptive algorithm for angle-rate estimation with low-noise and changeable bandwidth is proposed. This paper analyses the stability of estimator first, then designs the adaptive algorithm of the proportion gain of forward channel adjusted real-time by using the least square method. The MATLAB is used for simulating the data got by experiments, which makes the fluctuation for stable speed reduce 88%. Then, experiments are carried out on MSCMG, while the estimator is added to feedback route of velocity loop, thereby the fluctuation for speed curve reduces 71.5% without influence of bandwidth.Keywords：CMG;velocity estimation;quantized error;least square method error analysis- 29
- |
- 9
- |
- 10
Published：2020-08-12 -
Research of insulated bimorph in piezoelectric pump with double functions
Abstract：In order to improving piezoelectric pump’s work efficiency a insulated bimorph with double functions is proposed through processing insulation of bimorph. The insulated bimorph as driving piezoelectric pump’s component can curve on two directions and form the outputs. A double functions piezoelectric pump’s structure is expounded that a insulated bimorph forms two antrums. Some elastic curved surface differential equations of insulated circular piezoelectric composite laminates are derived from the elastic thin plate bending theory with small deflection. The project and course of insulated process of bimorph were introduced and analyzed. The experimental results showed that the Insulated bimorph not only has insulated characteristic but also favorable tenacity and consideration. Its attack voltage advances 20～30V than uninsulated bimorph. A new piezoelectric component with double function is offered for correlative manufacture and scientific research.- 30
- |
- 5
- |
- 3
Published：2020-08-12 -
Instantaneous Kinematic Characteristic of 3-UCR Parallel Robot
Abstract：Based on principal screw theory and imaginary mechanism method, the kinematic characters of a three degree-of-freedom spatial parallel manipulator with three UCR limbs were analyzed. According to the topologic structure of limbs, the screw coordinate system was set-up and the kinematics of limbs was analyzed. By the relation of the matrices of influence coefficient between limbs and moving platform, the kinematic model with the screw coordinates was established. It is showed that the matrices of influence coefficient is only dependent on the inputs and kinematic parameters and the method to analyze instantaneous motion is fit for others kinds of lower-DOF parallel manipulators. The instantaneous pitches of the principal screws gained decide that the kind of manipulator have always three DOFs with one translation and two rotations. By the numerical example when the moving platform is parallel to the base, the results of the pitches of principal screws validate the kinematic characters of the parallel manipulator.Keywords：parallel manipulator;principal screw theory;imaginary mechanism method;instantaneous motion- 53
- |
- 6
- |
- 5
Published：2020-08-12 -
Calibration of phase shifter in Spectral Domain OCT System
Abstract：In this paper, A calibration method for PZT phase shifter is developed, which is used in Spectral Domain OCT (SDOCT). Two steps are included in the calibration process: the first step is the rough calibration by the method of detecting and tracking the fringe patterns; the second step is fine calibration by a difference spectrum method with a precision increase of 6%. The experimental results in real differential SDOCT system show that a signal-to-noise ratio (SNR) increase of 10% is acquired by the method mentioned above.Keywords：Spectral Domain OCT;Differential Spectral Domain OCT;Piezoelectric transducer;Phase shifter;Filter- 25
- |
- 4
- |
- 1
Published：2020-08-12 -
MSMC Algorithm for Visual Tracking
Abstract：A new Sequential Monte Carlo-Mean Shift Monte Carlo(MSMC) algorithm is proposed for visual tracking in image sequences. The MSMC invokes Mean Shift to converge the samples with smaller weight to the local maximum ones, and can maintain the diversity with fewer samples, so the computational load can be decreased greatly. Experimental results in real video data show that the algorithm outperforms in terms of accuracy in estimating the target position and completing in real-time.Keywords：visual tracking;Sequential Monte Carlo;Mean Shift;local maximum- 39
- |
- 4
- |
- 4
Published：2020-08-12 -
Nonuniformity Correction Algorithm Based on the Infrared Focal Plane Array Readout Architecture
Abstract：The performance of an infrared imaging system is affected by spatial fixed-pattern noise, which is mainly due to the different photoresponse of each detector in a focal plane array for the same irradiance. In addition, the nonuniformity of the readout, which is involved in multichannel image data processing, causes the further noise. A novel nonuniformity correction algorithm based on the infrared focal plane array readout architecture is developed, which corrects the aggregate nonuniformity by two separate steps. First, the nonuniformity from the readout amplifiers is corrected by using the constant statistics method. Second, the noise resulting from the detectors is eliminated by exploiting the improved neural network method. The strength of the proposed algorithm lies in its high convergent speed and low computational complexity, and the performance is demonstrated with both simulated and real infrared imagery.Keywords：infrared focal plane array;nonuniformity correction;fixed-pattern noise;constant statistics;neural network- 46
- |
- 4
- |
- 7
Published：2020-08-12 -
The Object tracking Algorithm of TV Guiding System for UAV Based on Particle Filter
Abstract：In order to realize auto guidance for attack UAV, a TV guiding system was designed. To solve the nonlinear filter problem in guidance system, the particle filter algorithm is proposed. A resampling algorithm was put forward after a careful analysis on the degeneracy phenomenon. The weight value of each sample was directly used to determine whether this sample should be kept or be discarded and how many times a sample should be reused. An adaptive threshold based on statistical analysis was employed here to classify the small weights and the large ones. A correlation tracking method based on particle filters was proposed. The experimental results indicate the guidance precision of new resampling algorithm excelled the old one .Keywords：attack UAV;particle filter;correlation tracking;degeneracy problem;resampling- 31
- |
- 6
- |
- 13
Published：2020-08-12 -
Near-ground Channel Measurements and Analysis for Wireless Sensor Networks in Suburban
Abstract：Computer simulations are currently essential way to research and develop wireless sensor networks (WSN) protocols, rather than deploying high-cost test-beds. However, simulation results rely on physical layer assumptions，which are not accurate enough to capture the real behavior of WSN. So modeling the propagation characterization is very important for simulation, especially for the resource constrained of WSN. Most of the applications for WSN consider the nodes to be at ground level. However, there is a lack of radio propagation characterization by measurements. In this paper, we measured the path loss model of the near-ground propagation in suburban, and useful model parameters are provided by linearity regression. In addition, we also measured the irregularity of radio propagation near ground, and analysis the impact on wireless sensor networks.- 30
- |
- 8
- |
- 13
Published：2020-08-12 -
Face Illumination Compensation Based on Wavelet Transform
Abstract：A novel illumination compensation algorithm for face recognition under non-uniform illumination conditions was presented. Firstly, the face images were transformed from spatial domain to logarithm domain, and the 2-dimensional wavelet transform was calculated. Secondly, coefficients of low-frequency sub-band image were discarded for face illumination compensation in logarithm domain. The effect of face illumination compensation was denoted by face recognition rate because that the intention of illumination compensation was to improve the performance of face recognition. The proposed approach was compared with the discrete cosine transform (DCT) method in logarithm domain on Yale B face database. The experimental results show that the average error rate of the proposed approach can reach 0.18%, which is superior to the DCT method for face illumination compensation in logarithm domain. Additionally, the experimental results on CAS_PEAL face database indicate that the performance of the proposed algorithm is equivalent to the DCT method.Keywords：face recognition;face illumination compensation;wavelet transform- 39
- |
- 6
- |
- 5
Published：2020-08-12 -
Extended arithmetic of the equal correlation peak
Abstract：On the basis of ECPSDF algorithm analysis, the exemplar in space domain is used to replace the training image , and the constraint condition is reconstructed. The EECPSDF algorithm is presented. Simulative results and experimental results show that the EECPSDF algorithm can improve performance of matched filtering better, which have larger distortion tolerance and higher average correlation peak than ECPSDF algorithm.Keywords：optical correlation recognition;matched filtering;ECPSDF arithmetic;EECPSDF arithmetic- 38
- |
- 8
- |
- 8
Published：2020-08-12 -
An exterior attitude measurement system based on linear CCD for spatial object
Abstract：This paper designs an attitude measurement system with nine linear CCD cameras combination for spatial object, which overcomes the conflict between the speed and the accuracy with area image sensors for attitude measurement. The system can realize the real-time measurement for the measured object’s exterior attitude by separate real-time reconstruction for the 3D coordinates of point cooperation targets placed on the measured object under world coordinate system and the spatial solution. Based on the research for relative positions and one-one relationship between the point cooperation targets and the camera optical subsystems, the interference problem among many point cooperation targets was solved. A new optical system construction is designed to improve measurement accuracy and save space. The local calibration for the 1D cameras and global calibration were realized for the multi-cameras’ measurement system. The test results show that the attitude measurement system can obtain the ideal high accuracy and real-time measurement, and has some advantages such as simple cooperative target and cheap et al.Keywords：Linear CCD;attitude measurement;cooperation targets;multi-cameras measurement system- 34
- |
- 8
- |
- 24
Published：2020-08-12 -
Auto-focusing Evaluation Function for Microscope Using Weighted Neighborhood Correlation
Abstract：Objective: A new auto-focusing function for microscope images using the analysis on the four neighborhood gray level correlation has been presented, which is based on the study of the focusing principles and imaging processing of the microscope with the astigmatism considered as an ill factor to the focusing results. Method: firstly, to compute the four neighborhood gray level correlation of each pixel in every image sampled in the focusing processing. Then, to impair the influence of the astigmatism, some remedy measures such as weighted the correlation value by distances between the pixel and image center should be done in computing the focusing evaluation function, which is a quadratic polynomial about the average of the pixel neighborhood correlation. At last, analysis the variations of the function value of the sequential images, the focusing image corresponding the maximum function value. Result: the experiment results indicate that compared with the classical method, our function achieves the focusing sensitivity factor 0.3185~0.3268 higher, and improve the focusing correct rate with 0~40% under noise conditions. Conclusion: Our auto-focusing evaluation function can accurately estimate the focusing extents, and achieve high sensitivity and strong noise immunity.Keywords：auto-focusing algorithm;correlation;astigmatism- 36
- |
- 6
- |
- 12
Published：2020-08-12 -
Study on Video Background Extraction Based on Textural and Statistical Features
Abstract：Background extraction is a fundamental problem in video surveillance and motion tracking. Considering actual conditions in traffic video surveillance where image brightness varies over time and crossroad vehicle occupancy often keeps high, a new background extract method is put forward based on textural and statistical features. First, textural description of the image is established with grayscale-primitive cooccurence matrix. Then the textural feature is used to roughly evaluate the presence of moving targets in a region. In the next step, background pixels are determined according to the mixed Gaussian distribution model, by which the background of video sequence is extracted. Finally, the multi-resolution method is introduced to improve the computational efficiency. Experimental results show that the proposed method allows various changes of lighting conditions, and extracts exact background scenes even in vehicle-packed crossroad with only 1/4 computation period of the original method. Therefore, the method can better satisfy the requirements of background extraction algorithm, which needs to be robust and automatically adapt to complex environment.Keywords：Background extraction;Textural feature;Mixed Gaussian distribution;Multi-resolution computation- 42
- |
- 6
- |
- 9
Published：2020-08-12
Article
Loading...
0