2015 Vol. 44, No. 1
2015, 44(1): 1-5.
Background disturbance is the main factor affecting the testing results of infrared radiation characteristics with non-full field of view (FOV). In this paper, according to Planck's radiation law, the methods of measuring and calculating radiation characteristics of targets with non-full FOV were established with formula derivation and disturbance offset. On this basis, the infrared emissivities of aluminum plate and carbon nanotubes(MWCNTs)composite coatings were tested comparatively by using a SR-5000N spectroradiometer with both full FOV and non-full FOV. The results show that with non-full FOV, the infrared emissivities obtained by this method are in accord with the results measured with full FOV and can reflect the true spectral characteristics of the samples. This progress can effectively solve the FOV limitations to the radiation characteristics test of the target and greatly expand its application field.
2015, 44(1): 6-11.
On the basis of the heat transfer, a three-dimensional heat conduction model was proposed. The coating applied sinusoidal variation of heat flux was analyzed using large-scale finite element analysis software ANSYS. The use of two loading and subtraction effectively overcome the effects brought about by the constant part and environmental factors. Then data fitting method for seeking phase was discussed. Changing loading frequency, multiple sets of the quantitative relationship curves were obtained. From the theoretical point of view, the relationship of the phase between the modulation frequency and thickness were revealed. Finally, using the linear stages in curves, the quantitative relationship between phase and thickness was identified. A theoretical basis for precise measurements of coating thickness using infrared lock-in method was provided.
2015, 44(1): 12-16.
Detection probability and false alarm probability are two of the most important performance index of an infrared search and track (IRST) system. Detection probability and false alarm probability were decided by the performance of system hardware and detection algorithm, etc. The influence factors to system detection probability and false alarm probability were analyzed in this paper; the model of relationship between pipeline detection, detection probability and false alarm probability was established; the influence of pipeline detection to system detection probability and false alarm probability were studied. The simulation was conducted and the experiment results were analyzed. The system total detection probability or total false alarm probability will increase when the single frame detection probability or single frame false alarm probability increase, respectively. If the pipeline length is fixed, system total detection probability and total false alarm probability will decrease when the number of required detection frames increase.
Based on volume scattering data at 0.86 um, a new method for retrieving aerosol size distribution functions was put forward. According to the characteristics of aerosol size distribution, size distribution function n (r) was broken into two part, whole-trend function H (r) and detail-describing function (r), and a new series of basis functions were advanced and employed to approach (r). To overcome ill-posed nature in retrieval process, Tikhonov regularization method was combined with Mie scattering theory to strengthen the capabilities to void the influence of measurement noise and errors caused by numerical integration. Retrieval simulations are performed with size distribution data measured by Anhui Institute of Optics and Fine Mechanics, which represents three different kinds of aerosol, urban, rural and oceanic. Results show that, when radius of particles is larger than 0.2 um, the curve of retrieved size distribution function nearly coincides with that of actual size distribution, and their correlation coefficient is larger than 0.98 on condition that measurement noise isn't larger than 50%. Good robustness is also exhibited in the model put forward here; however when radius is smaller than 0.15 um, there is some deviation when measurement noise is large. To overcome this problem, Junge-correction method and accumulation-mode-compensation method were put forward, corrected results of retrieval size distributions show great consistency with actual size distribution. Compared with retrieval method based on intelligent algorithm, method here is more effective and less time-consuming, and has advantage in retrieving the detail characteristics of aerosol size distribution.
2015, 44(1): 27-35.
Non-contact infared radiation temperature measurement has the advantages such as fast response speed, accurate and convenient. In order to realize accurate measurement of the temperature of low-middle temperature objects (50-400℃), a system of dual waveband colori-metric temperature measurement based on the theory of dual waveband colori-metric temperature measurement was established. Firstly, the devices need to be calibrated accurately to fit curve which needs a variety of interpolation algorithm for correction. Then, the blackbody with given temperature's was measured as a reference.Experimental results indicate that the system of dual waveband colori-metric temperature measurement can precisely obtain the true temperature of low-middle temperature objects without the presence of target launch rate. The standard deviation of the object is within 3℃when the calibrated confidence is 0.95, which proves the validity of this experiment system. The construction of the experimental device for accurate measurement of low temperature object in the real temperature has important research significance.
2015, 44(1): 36-41.
Aspergillus niger spores is an important part of bio-aerosols, and its mass extinction coefficient is an important parameter for study on electromagnetic attenuation characteristics of aspergillus niger spores. The reflection spectra before and after aspergillus niger spores inactivation within the 2.5-15 um waveband were measured by squash method. The complex refractive index of aspergillus niger spores in the infrared waveband was calculated by using Kramers-Kroning (K-K) relation. Then, based on Mie scattering theory, the mass extinction coefficient before and after aspergillus niger spores inactivation in the infrared waveband were obtained, and the results were analyzed and discussed. The results show that average mass extinction coefficient has a decrease of 4.6 percent in the 3-5 um waveband and a decrease of 89.5 percent in the 8-14 um waveband. In light of this, to retain activity of aspergillus niger spores will play an important role in the increasing of its electromagnetic attenuation abilities.
2015, 44(1): 42-47.
The radiation characteristics of high-temperature gas flow have important application in detection, discrimination and aerothermal environment prediction for hypersonic vehicles. Based on a band model and considering the visible and infrared radiation of the ablation products of silicon-based materials for heat-shield, the method and code were developed to compute spectral parameter of ablation products and the radiation characteristics of high temperature gas flow field. The flow field parameters resulted from the numerical simulation and used the code, the radiation characteristics of flow over a model in a free-flight ballistic range and hypersonic blunt body were computed, and particularly the ablation effects were studied. The research shows that the ablation products have important effects on infrared radiation of the flow field.
2015, 44(1): 48-52.
Super-resolution (SR) imaging is a technology based on oversampling to reduce the aliasing and increase the image resolution. Pixel active area (PAA) model is essential in SR related research. The difference of MTF with the widely used square model and the Zshape model we proposed was calculated to simulate the practical infrared focal plane array (IRFPA) production. The cause of the difference was analyzed. Furthermore, a hypothesis was proposed, which the smaller the difference between the closest and the farthest distances from the PAA boundaries to the pixel center, the greater the MTF of IRFPA will be. Different PAA shapes were discussed and the MTFs of these shapes were calculated. The calculation results verify the hypothesis we proposed. These results also show that the circle PAA is the most ideal model and it should be used as a reference for IR FPA design.
2015, 44(1): 53-58.
A system solutions was proposed that utilized the platform composed of stripe type laser sensor and industrial robot for scanning and detecting workpiece, imaging for its contour as well. Stripe type laser sensor obtained the three-dimensional point cloud data of the workpiece contour by scanning in movable way. Then combined with the specific algorithm, point cloud data was dealt with through denoising, interpolation processing, which made the point cloud data reflect the objective morphology of artifacts more truly. Finally according to the information of point cloud data, binary images of the workpiece contour was generated. In the experiment, the precision of imaging can reach to 0.1 mm. Thereby, imaging, detection and location for the workpiece are realized instead of traditional CCD camera in some special industrial occasions, solving the problem that traditional CCD is lack of anti-interference ability.
2015, 44(1): 59-64.
The laser spot image quality is one of the important index of laser guided weapons. In order to check the index, the advantages and disadvantages of general laser spot testing technology were analyzed. According to the several factors affecting the test precision field of laser spot, a testing system of high accuracy laser spot outfield detection based on the double CCD with the indirect method of non-contact type was designed. The system had various functions like recording the spot and image processing, realtime monitoring, calculation of laser coding and error value, spatial variation of energy density foward lens and the laser pulse leakage rate and other functions. It also had characteristics of testing large dynamic range, high resolution, anti external interference was strong, easy to use etc. It can do the test and analysis of laser facula evaluating field with high precision. The test system can solve the problems in the field of laser spot test through the test analysis and application of the external field,it have played an important role in the process of the field test outdoor.
2015, 44(1): 65-70.
Electrochemical deposition combine with pulse laser by using the thermal shock effect of laser, which can improve deposition efficiency and processing quality. The copper was deposited by a compound processing of laser and electrochemical in an experimental system established. The mechanism of the electro-deposition with the thermal shock of the laser was analyzed. These forces created by the laser make cathode substrate produce elastic deformation, changing the electrode potential and current density, improved the electro-deposition quality. Through the processing experiment, the effect of deposition efficiency and processing quality under different average laser power density were studied and discussed. The results show that when the average laser power density between the 100 kW/cm2 to 400 kW/cm2, the good deposition quality can be obtained. And the maximum deposition rate can be obtained when the average laser power density about 200 kW/cm2.
2015, 44(1): 71-75.
CW intracavity frequency-doubled Raman laser has become an important approach of CW yellow laser, and the formula which directly described the variation of the laser output with input pump power and laser parameter was not given. A theoretical model of continuous-wave intracavity frequency-doubled Raman laser based on normalized rate equations with plane-wave approximation was built. By solving these normalized rate equations, the expression which described the variation of normalized yellow laser output with the normalized input and normalized laser parameter was obtained, and the theoretical curves which were also obtained. The relations between the normalized output and normalized input as well as normalized parameters was discussed. The model can be used to help the design of the lasers.
2015, 44(1): 76-79.
To study the effects of the positive focal shift on the impulse coupling coefficients about the CO2 pulse laser focus on the aluminium target at air ambient. By changing the distance from the focus to the target, the relation between the positive focal shift and the impulse coupling coefficients is achieved. The experimental result indicates that coupling coefficients declined from 4.48 10-5 Ns/J to 1.6810-5 Ns/J, when the focal shift changes from 0 to 20 mm.While the focal shift increase between the 20 mm and 35 mm,the coupling coefficients rise and reach 2.21 10-5 Ns/J, then decrease to 1.91 10-5 Ns/J at the 45 mm.The two-dimensional model theory of laser supported detonation wave interacting with solid target was used to calculate the coupling coefficients. The trends of theory and experiment are same.
2015, 44(1): 80-84.
In inertial confinement fusion (ICF) driver design, by varying the polarization of beamlets, a orthogonal polarization control plate (OPCP) is applied to achieve incoherent superposition of beamlets on target for improving illumination uniformity. The model for the transmittance function of OPCP was built up. The depolarizing characteristics and uniformity of focal spot of single beam and of multi-beam superposition were simulated numerically and analyzed. The effects of the element number of OPCP on the characteristics of focal spot were further discussed. The results show that, the depolarized laser beam could be achieved by using the orthogonal polarization control plate, and the light field exhibits partially polarization in time scale. The complementary combination of orthogonal PCPs is better for the superposition of depolarized multi-beams. Moreover, the depolarizing effect remains almost unchanged with the element number of OPCP. Thus, the number of elements could be fewer to reduce requirements of processing technology.
2015, 44(1): 85-90.
Based on the Gaussian beam propagation theory, and combined with the structure of the laser diode stack, the fast axis beam model of the laser diode stacks was established. And considered with the divergence angle and directional factor of each diode laser array, the calculation for the fast axis beam quality of the diode laser stacks was amended which was finally verified by the experiment. The result shows that compared with the experimental measurements, the calculation error of this model is only 2.14%. Compared with the ones before amending, which are 24.16% and 18.36%, the new calculation method is improved a lot in accuracy and can reflect the fast axis beam quality of diode laser stacks more exactitudly.
The influences of frequency drift of laser source on phase sensitivity optical time domain reflectometer(-OTDR) was investigated. One-dimensional pulse-response model of Rayleigh backscattering in a single-mode fiber was employed to analyze the trace-to-trace fluctuations induced by frequency drift. In laboratory test, an unbalanced Mach-Zehnder interferometer (MZI) with path-length difference of 100m was employed to monitor the frequency drift real-time, and the performances of -OTDR system using three lasers with different frequency drift rate were compared to testify the theoretical analysis. Both the theoretical and the experimental results show that the frequency drift of laser source is an important source for the fluctuations of -OTDR waveform, and the trace-to trace fluctuations increase as the growing of frequency drift. Moreover, it is difficult to distinguish the fluctuations induced by frequency drift and the fluctuations induced by intrusion event in time-domain when the frequency drift is up to several hundreds of MHz/min. However, the differences between them are more evident in frequency-domain. The conclusion is useful for choosing laser sources and improving the performance of -OTDR.
2015, 44(1): 96-101.
In order to precisely analyze electron temperature and electron density of aluminum alloy, the Laser Induced Breakdown Spectroscopy was adopted. The second harmonic of a pulsed Nd:YAG laser (532 nm) has been used for the ablation of aluminum alloy E311 in air at atmospheric pressure and the laser-induced plasma characteristics were examined in detail. The electron density of 4.31016 cm-3 was inferred from the Stark broadening (0.12 nm) of the profile of Fe (I) 381.59 nm. In order to minimize relative errors in calculation of the electron temperature, an improved iterative Boltzmann plot method with eight iron lines (370.56, 386.55, 387.25, 426.05, 427.18, 430.79, 432.57, 440.48 nm) is used. Experimental results show that the electron temperature is 8 699 K with the regression coefficient of 0.999. The calibration curve for iron based on Fe (I) 404.58 nm was established using a set of six samples of standard aluminum alloy (E311, E312, E313, E314, E315, E316) and the detection limit was 0.077 9 wt%. The plasma was verified to be optically thin and in local thermodynamic equilibrium based on the experimental results.
2015, 44(1): 102-106.
Laser micro-propulsion is a new laser-powered electric propulsion technology, which uses the mechanical effect generated by laser-matter interaction. Liquid as propellant is the latest points of interest. Impulse coupling characteristics of interaction between liquid and laser decided the merits of propulsive performance. Torsion pendulum device was used to measure the micro-impulse. Monopropellant gel propellant, GAP and glycerol were used as propellant. Impulse and impulse coupling coefficient were measured under different laser energy. GAP obtained higher impulse coupling coefficient and was further studied. The results show that impulse coupling characteristics of GAP are better. Impulse coupling coefficient is generally greater than 500 uN/W, maximum is 1 493.0 uN/W. However, specific impulse and ablation efficiency are relatively low. Maximum specific impulse is 140 s; maximum ablation efficiency is 37.6%.
2015, 44(1): 107-111.
Ti60 alloys were fabricated by using direct laser deposition (DLD) technology and it was studied that the effects of hot isostatic pressing (HIP) on defects, microstructure and tensile properties of the DLD Ti60 alloys. The results show that there are two typical kinds of defects in the DLD Ti60 alloys, which are pores and lack of fusion. After HIP treatment, pores and the small size of lack of fusion are eliminated. There are columnar crystals at the bottom and the middle of the as-deposited specimens, but at the top of the specimens are equiaxed grains. The microstructure is widmanstatten structure, which is composed of alpha laths and beta between the laths. After HIP and double annealing treatment, the grain boundary alpha melting, the most of the original beta grain boundaries disappear, alpha laths coarsening, the length-width ratio decreases, and the microstructure becomes basket-weave microstructure. Compared with the forgings, the as-deposited specimens have a high tensile strength with a low plasticity, after HIP and double annealing treatment, the plasticity of the as-deposited specimens exceeds the standards of the forgings.
2015, 44(1): 112-117.
LADAR target simulator is the key component of the HWIL system for LADAR,which is designed to simulate the LADAR return projection. One of the key technologies of target simulator is object modeling. The method of object modeling was performed and mathematic models were given based on coordinate transformation. The overall information of target was obtained through data registration on the part of the target information from different angles of scanning. Then according to the viewpoint of coordinate transformation, the target information was obtained by arbitrary viewpoint in the space, which was provided for image generation system to generate an image. Theoretical results agree well with the values measured experimentally. Therefore, the accuracy of modeling was verified by experiment. This method can provide a feasible way for LADAR target simulator to acquire the information of the target.
2015, 44(1): 118-121.
Because of laser radar having extremely high detection sensitivity, the micro-Doppler effect is obvious in laser radar detection process. At present, the study of micro-Doppler of rotor blades is almost based on the hovering helicopter, however, helicopters are taking various motion in the actual condition. In this paper, the RCS of a helicopter rotor was calculated, and a micro-Doppler model of a helicopter rotor was established. Based on the model, taking the AH-64 armed helicopter for example, the micro-Doppler effect of the rotor blades in radar detection process was simulated and calculated, of which was taking the uniform linear moving and the face upward moving. The results show that the motion state of the helicopter can be judged primarily through analyzing the range profiles of the distance and the frequency spectrum of the micro-Doppler effect of a helicopter's blades in radar detection process, which provides some reference for moving helicopter identification by micro-Doppler.
2015, 44(1): 122-126.
The tertiary mirror pointing assembly(M3PA) of the thirty meters telescope(TMT) is the largest tertiary mirror in the world. The tracking and pointing performance of M3PA is better than any other telescopes which have been built, and the working condition is even worse. So the designers face an enormous challenge. The tracking system includes the bottom rotator axes and the tilt axes. The study of this paper focused on the tilt axes. There were two bearing arrangement methods for the tilt axes. The first one used two single angular contact bearing to stand the shaft. The second used two double rows angular contact bearings. They both met the requirement when the M3PA was vertical. But the first method became invalid when the M3PA was horizontal, while the second can provide a better support about 15.1 Hz of the first modal frequency. Then some FEA were done to find out the carrying capacity of the bearings. The results show that the maximum load applied on the rollers is up to 5 000 N, while the maximum stress is up to 2 300 MPa. Otherwise, the load distribution just likes a cosine curve. So it can be found that the analysis is believable. In addition, there are evident load applied on the four rows rollers, which proves that the bearing arrangement can disperse the load effectively. It can be concluded that the selection of the bearing arrangement is a good choice for TMT tilt axes design.
2015, 44(1): 127-133.
In order to overcome the limitations of conventional calibration method and realize high precision in-flight radiometric calibration of GF-1 PMS sensors, a new wide dynamic radiometric calibration method using multi-test sites was presented, and the uncertainty of this method was analyzed. Firstly, the wide dynamic radiometric calibration theory was introduced and the characteristics of test sites was described. Besides, the GF-1 satellite to field synchronous observing campaign with multi test sites was designed. Secondly, based on measured data and wide dynamic calibration model, the calibration of PMS sensors was finished. Finally, the uncertainty and feasibility of this calibration algorithmic were discussed. The radiometric properties of GF-1 PMS sensors have changed comparing with the prelaunch laboratory calibrated results, and the biggest change is close to 7.72%. And the uncertainty of wide dynamic radiometric calibration of PMS sensors based on multi-test sites is 5.35%. The obtained precision of calibration coefficients meets the requirements of remote sensing radiance's retrieval, and the method provides a reference for further calibration of high resolution satellite.
2015, 44(1): 134-140.
Wind load is one of the main factors that affects the performance of ground-based telescopes, in order to investigate the function of wind load and the influence degree on the telescope, firstly, the telescope, dome, and exterior flow field geometry were established. Secondly, Computational Fluid Dynamics (CFD) was used to analyze the instantaneous distribution of the air's velocity, pressure and static pressure on primary mirror, at three different altitude angular(30, 60, 120), when the wind at the speed of 10 m/s. Finally, the primary mirror surface accuracy was gotten after removed the rigid body displacement through the finite element method. The simulation results show that static pressure power spectral density of the primary mirror is close to the measured data of Gemini telescope, better simulate the practical effect of the wind load. The RMS values of the mirror surface deformation caused by wind load are 3.74E-1 nm, 2.5E-2 nm, 1.71E-1 nm meet the surface accuracy requirement.
2015, 44(1): 141-147.
Miniature spectrometer is one of the main research directions in recent years. For the design requirements of the miniature spectrometer data acquisition system, the high-resolution data acquisition system was designed using TCD1304DG linear CCD. The system used FPGA EP4CE15 as the controlling core, the Analog Front End (AFE) chip as the main chip of the signal processing. The AFE chip integrated Programmable Gain Amplifier (PGA) and 16-bit analog-digital convertor. High-speed data transmission circuit with USB2.0, the PC software of the spectral acquisition were designed, which realized the real-time processing of spectral data. The designed scheme of miniature integrated circuit meets the characteristics and requirements of the spectrometer of miniaturized and is portable to be used.
2015, 44(1): 148-156.
Fully-steerable radio telescope rotates in two directions during its operation which results in different kinds of upwind postures and complex wind load distributions on its reflector. In order to get the wind load distribution and obtain the corresponding wind load of the reflector structure, the 110 m (F/D=0.3) telescope was chose to be built in Xinjiang. First, the computational fluid dynamics software FLUENT was used for its average surface pressure distribution simulation and the corresponding wind tunnel tests were conducted to verify the validity of CFD simulations on the average surface pressure distribution of the reflector. By comparing the numerical simulation and experimental results, the surface wind load characteristics of the rotating parabolic reflector were revealed. Subsequently, the wind load characteristics were analyzed numerically for the change of its directions for several typical radio telescope structures and the results were given for different apertures, different focal ratios. The results provide valuable reference for similar structure in its wind resistant design.
2015, 44(1): 157-161.
A novel aspherical zoom curved compound eye structure was proposed. The curved substrate was segmented into three same sector areas, and the microlens array of every area could image the target object which had a certain distance to the compound eye. So the focal length can be controlled within certain scope. The focal length and the size of microlens were calculated by the area and the position, and the spherical surface of microlens were all optimized into aspheric surface. Finally, from the ray tracing simulated result of the new curved compound eye, the spherical aberration of microlens is decreased to about one percent compared with the initial model, the compound eye can realize focal length regulation and the problem of spherical aberration at the edge can solve effectively. So the performance of imaging is greatly improved.
2015, 44(1): 162-169.
The magneto-conductance effect is used to describe the changes of the current of the OLED (organic light-emitting diode), whose organic functional layer has no ferromagnetic material. In the presence of external magnetic field, the current in the device would be changed significantly since the diode is sensitive to the magnetic field. The magnitude of the magnetic field could be got through comparing the value of current with the curve of B-I which was measured and stored in the computer. Therefore, this special effect could be used to produce the new type of sensor of magnetic field. If the complex excited state and the process of spin relaxation in the OLED could be studied thoroughly, the new luminescence materials could be synthesized and the new structure could be designed which can help us improve the performances of OLED. Furthermore, the magnetic field can have a significant influence on the excited state process in the diode which can be a tool to study the underlying mechanisms of OLED. Up to now, the tremendous progress has been made in the field of magneto-conductance effect. This article summarized the background, progress, the major achievement and the possible microscopic mechanism in the field of magneto-conductance effect. In addition, the prospect in the field of magneto-conductance effect has been made.
2015, 44(1): 170-175.
The residual linear birefringent of sensing fiber, temperature and vibration sensitivity severely influence the accuracy of Sagnac fiber optic current sensor (S-FOCS). A sensing fiber can be used in FOCS with spun high birefringent fiber (S Hi-Bi fiber) was designed. This S Hi-Bi fiber includes three sections: two terminal sections with variable spin-rate along fiber were utilized to substitute the fiber quarter-wave plates, respectively converting the light polarization state from the linear one to the circle one, and vice versa; and the middle section with a uniform spin-rate was utilized as the current sensing fiber which maintains the circular polarization state and compress the residual linear birefringent during the light propagation. In addition, the sensing fiber was wound into a special geometric structure so that the Sagnac phase shift was inherently eliminated and the sensing result did not depend on the position of the current conductor. In theory, used the coupled-mode theory the evolution of the light polarization state was simulated when linear polarization states light incident into the sensing fiber. A novel Sagnac fiber optic current sensor with vibration insensitivity based on this spun high birefringent fibers was proposed.
2015, 44(1): 176-181.
The solar panel is power source in the photovoltaic lighting system, and the output characteristic is a significant factor as assessing energy transformation and maximum power point tracking (MPPT) efficiency. In this paper, the module of the solar panel was built by using Matlab/Simulink, and the equivalent circuit of solar panel was also been simulated accurately. On one hand, the output power firstly increased if the voltage grew, and then decreased if the voltage continually grew. On the other hand, the output power could increase when the temperature decreased or when the intensity of illumination increased. In addition, the voltage at the maximum power would decrease if the number of the paralleled solar panels increased, but the tendency would keep the same when the number of the solar panel was bigger than 3. And the maximum output power would increase with the number of the series'panels increasing. However, the maximum output power would remain unchanged when the number of the panels was more than a certain quantity. This present work can provide theoretical support for building the photovoltaic lighting system.
2015, 44(1): 182-187.
For solving the problems about Ge system chalcogenide glass fiber's relatively high loss, etc, high-purity Ge28Sb12Se60 glass was prepared by chemical and physical methods of purification. The absorptions caused by C, H, O impurities were obviously reduced in IR band. Ge28Sb12Se58S2 chalcogenide glass tube with precision wall and fine optical properties was prepared by means of tube-rotating technique. Fibers with core-cladding structure were drawn by rod-in-tube method. The diameter of the fiber is 501.5 um and the bending test showed the diameter of the circle is 5 mm. The fiber loss is 2.2 dB/m (except those at 2.87 and 4.5 um).
2015, 44(1): 188-194.
For large-aperture primary mirror hydraulic support system, a simple and reliable precision guiding mechanism is needed to give a larger stroke range (mm) for cylinders, which did not require lubrication and maintenance. In this paper, a flexible metal membrane was designed for the cylinder guiding and radial positioning. With the method of finite elements and nonlinear geometry algorithms adopted, an analysis was carried on the flexible membrane with different topologies, it was shown that V-shape metal membrane could well overcome stress stiffening and maintain the stability of flexibility; with flexibility as the optimization target, optimize the V-shape position and geometry dimensions of membrane V-shape, and the guiding flexibility of metal membrane was improved by 14.2%; established the experimental platform, did experiments and verify the simulation results. According to the experiment and simulation results, the V-shape membrane is found not only having a good flexibility in the vertical surface direction, but also ensuring the stability of flexibility by avoiding stress stiffening. These founds give a certain guidance in the design and application of the guiding mechanism for hydraulic support cylinders and active micro-displacement actuator.
2015, 44(1): 195-200.
A three-plate-type polarization state generator (PSG) was designed and the transformation of Stokes parameters was derived according to the structure characteristics of PSG. Based on the principle of Tabu Search (referred to as TS) algorithm, a control algorithm was proposed which was able to not only achieve the rapid transformation between the polarization states but also reduce the bias-voltage across the crystal. The simulation results show that, by using this control algorithm, the PSG can transform the linear polarization into arbitrary polarization and the precision can arrive to 0.07%. If the Stokes parameter S2 and S3 were restricted to the specific region on the Poincare sphere, the desired polarization state was generated by this control algorithm and the control voltage amplitude was ensured within 120 V. Last, the experimental results show that,this control algorithm could satisfy the requirement of encoding in continuous variables coherent optical communication of single beam.
2015, 44(1): 201-204.
In order to expand the low reflective properties of silicon solar cells in a perfect frequency range, a kind of optical microstructures composed of period arranged square pillar was designed. On the base of the effective medium theory, the reflectivity of silicon solar cells changing with the pillar's altitude and duty cycle was studied. Then, a structural model was set by simulation software MEEP. The results of the simulated research demonstrate that the optical microstructures can very effectively reduce the reflection in a perfect optical frequency range.
2015, 44(1): 205-209.
A fiber-optic distributed sensor based on Michelson interferometers for detecting the time-varying disturbance was presented in the paper. The proposed sensor is constituted of two Michelson interferometers with an optical fiber delay loop. The disturbance causes a phase modulation which is detected by the proposed sensor and converted to the location information. The interference signals received by the photo detectors through capacitive coupling separated directly to eliminate the DC component are preprocessed by the peak-to-peak value calculation method. The phase information of the preprocessed signals is acquired by the Hilbert transform, phase unwrapping and the corresponding trigonometric equations calculation. The frequency spectrum analysis and the mathematical operations are then conducted to locate the disturbance. Experimental results obtained with a 20 km long sensing fiber are discussed in the paper. The proposed distributed disturbance sensor has the significant advantages of capability of real time sensing, insensitive to the polarization state and low cost.
2015, 44(1): 210-214.
The acousto-optic modulator (AOM) is an important component of fiber-optic distributed vibration sensing system based on -OTDR which can modulate the CW light to pulsed light. The frequency of AOM directly affects the dynamic performance of the system. Based on the sensing mechanism of the system, the influence of modulation frequency on the frequency response was analyzed theoretically. The results show that the utmost frequency of the vibration signal regenerated by the system is limited by the modulation frequency. The range of frequency response extends with the increase of the modulation frequency, which means the limitation of frequency response increases and the distortion of the vibration signal decreases when a laser source with constant optical power is utilized. On the contrary, the high frequency vibration signal will be severely distorted when the modulation frequency is insufficient.
All-optical logic gates are the basic unit of all-optical computer and all-optical network in the field of communication in the future. A variety of structures and methods has been proposed for the implementation of all-optical logic gate, however, the bottleneck of this technique has emerged, which is how to cascade the individual all-optical logic gates to achieve more complex logical relationships. The existing schemes for all-optical logic gate, generally, don't have excellent cascade to realize multilevel connection. And the existing analysis on the cascade usually stays on the theoretical level without combination with the realistic situation, which have little sense for the practical application. This work has presented a novel ultrafast all-optical NOT gate based on high nonlinear Sagnac interferometer, has built its mathematical model and digital model, has adopted Gauss pulse as input light for simulation, which is more realistic, and has analyzed the system cascade on the basis of simulation results. The analysis of cascade has taken into account the influence of fiber loss and walk-off effect. The basic conclusions in this article show that the proposed scheme of all-optical logic gates can maintain excellent cascade under practical situation with interference factors.
All-optical multicasting by exploiting various optical nonlinearities has received considerable attention for performing data routing function from a single node to several destinations directly in the optical domain. Based on the self-phase modulation and followed spectral filtering, simultaneous one-to-six channels all-optical wavelength multicasting for a 40 Gbit/s RZ signal with 100 GHz channel spacing in a dispersion flattened highly nonlinear photonic crystal fiber was achieved. Dynamic characteristic of proposed wavelength multicasting scheme was further exploited. The results show proposed scheme has wide operating wavelength range and high tolerance to signal power fluctuation.
2015, 44(1): 228-232.
The superfluorescent fiber source (SFS) is an ideal source for fiber optic sensors (FOSs), because of the high stability. Relative intensity noise (RIN) of a SFS is proven to be an most important factor limiting the performance of FOSs. As the RIN cannot be suppressed effectively using an analog circuit, in this paper, a digital RIN suppressing system executed with intensity modulator was presented. To demonstrate this method, a semi-physical simulation was propose in which the RIN was reduced by 20 dB at the center frequency. This method is more effective than the former analog one by simulation. This digital RIN suppressing system is of great value to improve the performances of FOSs.
2015, 44(1): 233-238.
Substandard ratio error under full temperature (-40-60℃) is one of the factors that restrains the practical application of domestic All Fiber Optical Current Transformer(FOCT). The Verdet constant of the sensing fiber changes with the fluctuation of mean wavelength when the light goes through. Then the output ratio is influenced which decreases the accuracy of the system. The relation between the fluctuation of mean wavelength and system ratio error was analyzed thoroughly and validated experimentally. Also, influence on the mean wavelength caused by the entire optical components was theoretically analyzed, and the degree of influence and the variation trend were experimentally measured. A method was put forward to make the polarizer and the fiber delay line have a temperature self-compensation on the variation of mean wavelength, and thus the change of mean wavelength was reduced. While the 0.2 s class accuracy requirement is guaranteed, the impact can be lowered as much as possible.
2015, 44(1): 239-243.
The phase modulation technique is the key technique to obtain the angular rate in resonator fiber optic gyro (R-FOG). Adopting the appropriate modulation parameters, the performance of the gyro can be greatly improved. Based on the phase modulation spectroscopy expression, and the relationship between the amplitude of modulated carrier signal and the amplitude of phase modulation voltage, the method for determining the optimized phase modulation parameters was proposed. Using the method, the backreflection noise can be effectively suppressed, while the optimized sensitivity of the gyro can also be ensured; The half-wave voltage of the modulator was measured using the self-heterodyne interferometer technique with sine wave phase modulation. And the relationship between the amplitude of modulated carrier signal and the amplitude of phase modulation voltage was obtained, which was consistent with the theoretical analysis; The fiber ring resonator (FRR) was composed of a 12 m length polarization maintaining fiber and a polarization maintaining fiber coupler with the coupling ratio 50豫. The diameter of the resonator was 0.15 m. The rotation experiments under various angular rates were conducted, and the dynamic range and output nonlinearity of the R-FOG were 480 ()/s and 3%, respectively.
2015, 44(1): 244-248.
The mean wavelength dependence on pump power in an Er-doped superfluorescent fiber source of double-pass backward configuration was studied. Data presented shows that mean wavelength variations with pump power can be reduced to-9 ppm/mW for selected pump powers by using an Erdoped fiber filter. And the total mean wavelength instability of the fiber source is less than 33 ppm(peak-to-peak) over the-40℃ to 60℃. The bandwidth reaches 17 nm. The pump power is 55 mW at 974.2 nm and the output power reaches 5.83 mW with 5-m Er-doped fiber.
2015, 44(1): 249-253.
In order to make the space camera to work under the condition of appropriate temperature, the active thermal control system based on temperature level was proposed. Firstly, the condition of temperature balance was analyzed and the active thermal control strategy was ascertained. Secondly, the system composition and work principle were introduced. Thirdly, the temperature control indexes of active thermal control were determined under the condition of no essential influence to image quality. Finally, the algorithm of temperature control was determined. Experimental results indicate that the active thermal control system can make the camera in temperature balance based on the active thermal control strategy, the difference in temperature between primary mirror and reference temperature is no more than 1℃, the circumferential difference in temperature of primary mirror is no more than 1℃, the difference in temperature between primary mirror and secondary mirror is no more than 2℃ and the difference in temperature between primary mirror and third mirror is no more than 5℃, the results of temperature control are satisfied the requirements of control indexes of the active thermal control strategy and the camera work temperature.
2015, 44(1): 254-259.
In order to measure the wavefront aberration of optical system with the high accuracy, the improved fiber phase-shifting point diffraction interferometer was introduced, its working principle was introduced, and the parameters of the key components of the interferometer including laser source and fiber were selected and analyzed. After the test, the laser power stability was about 1%(10 min), the spot size was in the allowable range of the optimum coupling efficiency, the beam position stability was about 6 um, the coherence length was about 1 cm, the above were all in the allowable range of testing accuracy; No polarization-maintaining single-mode fiber was selected, its core diameter was 3.5 um, the fiber endface was coated transflective metal film, the high fringe contrast and light energy utilization were realized, and the wavefront reference source was designed, it's convenient for the polishing, coating and clamping of fiber endface. Finally, the selected components were used to build experimental device of fiber phase-shifting point diffraction interferometer, above works provide preparation for ultimately achieving high accuracy test of the wavefront aberration of optical system.
2015, 44(1): 260-265.
Aiming at the affection of Morifringe signal quality for high-precision encoder interpolation error,a method of analysis based on quality of morifringe signals for high precision optical encoder was presented. The signal parameters were obtained with using signal reconstruction and Fourier transform algorithm, which reflects the real Morisignal quality. The accuracy of interpolation error of measurement was improved. While the encoder is motion, the data acquisition card samplings two photoelectric signal with a phase difference of /2. The signal waveform was got by reconstruction algorithm of sampling the signal. Through the discrete Fourier transform algorithm analyzing reconstruction waveform, the parameters like DC component, amplitude, phase, and harmonic component were solved. Finally, dynamic interpolation error is obtained based on relationship between the signal parameters and interpolation error by experimental verification. Experimental results show that, the interpolation error of a 24-bit absolute rotary optical encoder was measured. Interpolation extreme errors are +0.48 and-0.21. Compared with traditional method of interpolation error measurement, this method measures quickly. It is applicable to real-time detection of encoder dynamic interpolation error at the actual work site.
2015, 44(1): 266-272.
For rockets can only do two degrees of freedom in angular motion in the preparation phase before the launch, causing some parameters are not significant deficiencies. In this paper, based on the context of transformation of the guided rockets, a calibration solution was made which joined the roll campaign in the preparation phase before the launch and the corresponding observability analysis method was proposed. First, a 21-dimensional error model was established. And the observability analysis method was used to analyze the observability of the error parameters, then a comparison of the three phases was made. Results show that multiple parameters become considerable because the roll motion and other parameters'observability are also significantly improved. Finally, the singular value decomposition method was used to verify the calibration of the proposed programs and observability analysis method. Results show that almost all parameters'singular values are greater than 1, fully embodies the effectiveness of the roll motion to the error parameter estimation and the feasibility of observability analysis.
2015, 44(1): 273-278.
In order to realize 3D visualization velocimetry of microfluidic, an micro-particle tracking velocity measurement system based on optics coherence tomography was established and the principles of the system, algorithms such as image extraction of micro-particles, matching, and velocity computation were investigated. First, velocity measurement system based on optics coherence tomography and scanning and imaging method were presented. Then, micro-particles in fluid were detected using median filtering, OTSU binarization method and volume filtering to realize 3D visualization of flow characteristics. Finally, to find an optimal matching of micro-particles, the cost function was defined using the quadratic distance between particles, as well as the quadratic differences in the intensity moment of order 2, and velocity was computed using 3D coordinates of particles. Experimental results such as 3D particle images, and velocity vector with micrometer spatial resolution in convective flow were given. It is important for the velocity measurement of the complex microfluidic and study of microfluidic devices.
2015, 44(1): 279-284.
In order to verify the measuring accuracy of the shape center location of the target by using CCD camera, a novel method was proposed in this paper as making use of testing the distance error from the feature points to the shape center location of target image plane indirectly. The measuring principle of testing the shape center location of target based on CCD camera was introduced. In order to extract coordinate values of the shape center location and feature points of target conveniently, the LED sources were installed at the corresponding positions of simulated target. According to the corresponding relation between the target and the image coordinates, the data processing methods of verificatng the measuring accuracy of shape center location were given. The experiments were repeated twice. The results of measuring accuracy of shape center location are A1 mrad, E1=0.021 mrad, A2=0.032 mrad, E2= 0.015 mrad, and two experimental results are basically identical. The results show that the method of verify the measuring accuracy of shape center location of target using CCD camera is evaluated exactly and conveniently.
2015, 44(1): 285-290.
Concerning the difficulties such as small measuring range and complicated operation in traditional train speed measure device, a new speed measuring system for dynamic clearance limit measurement of high-speed train is designed based on scanning laser radar. The scanning laser radar fixed in the position of 10 meters from the train. According to the principle of pulsed time-of-flight laser ranging, after the train enters the scan range the scanning laser radar scans the train point by point along the direction of train obtains the body contours. Process measurement data of cars with least square method to obtain the track and direction of the train. The travel distance of the train during two adjacent measurement cycle can be measured through piecewise linear interpolation. Complete the train speed measurement through the above work. Field experiments show that the system is easy to operate with capacity of 600 km/h and the system measurement error is less than 1.2% meets the demand of high-speed train velocity measurement.
2015, 44(1): 291-297.
Based on the analysis of long-term sounding data in the arid environment, different seasonal fitting formulas on refractive index, which varied with heights, were obtained. The formulas were used to calculate atmospheric refraction, atmospheric dispersion and ranging of space target under the certain condtion by the opto-electronic tracking equipments of different wavelengths. The results show that, for atmospheric refraction, the result of winter is greater than the result obtained by standard atmosphere, and is greater than the results of the remaining three seasons. For atmospheric dispersion, the difference between 0.55 um and 1.3 um, and the difference between 0.55 um and 3.9 um in spring are more than the results of the other seasons. The differences between different wavelengths are small on condition that the elevation is larger than 55. For ranging correction, the varied characteristics of different wavelengths in different seasons have slight differences, and the characteristics of summer and autumn are similar. The ranging value of 3.9 um is more sensitive than other wavelengths. As a reference, the above results can be provided for certain applications on opto-electronic engineering.
2015, 44(1): 298-304.
Oxygen absorption rate is the core of passive ranging technology calculation which used oxygen A band. The cloudless sky background radiation and blackbody radiation which contained oxygen A absorption bands was researched. The oxygen absorption rate distribution of cloudless sky background was calculated under the different conditions of observation zenith angle, times and solar zenith angle used CART. Then the calculation results was compared with the oxygen absorption rate of blackbody radiation with different observation zenith angle at different distances. The results show that the oxygen absorption rate of blackbody radiation is greater than the oxygen absorption rate of cloudless sky background radiation when the detection distance is more than 3 km. So depending on different viewing conditions to set the oxygen absorption rate threshold will improve the detection probability of the target and reduce the influence of background radiation on passive ranging.
2015, 44(1): 305-309.
Based on the extended Huygens-Fresnel principle and the quadratic approximation of Rytov's phase structure function, the analytical expression for the cross-spectral density function of the Gaussian Schell-Model (GSM) array beams propagating in atmospheric turbulence was derived. The degree of spatial coherence of GSM array beams in atmospheric turbulence was investigated numerically. The result shows that the spatial coherence properties of the GSM array beams are determined by the coherent length of beamlets, the transmission distance, the refractive index structure constant of atmospheric turbulence and the relative radial fill factor of the source in common. It also shows that the spatial coherence of the GSM array beams ends as Gaussian distribution, but multiple peaks are existed during the transmission, the width of the degree of coherence becomes smaller with the transmission distance continues increase which means that the degree of spatial coherence turns worse.
2015, 44(1): 310-316.
The distribution of oxygen density is relatively stable in the atmosphere. It changes little with latitude and season. Its absorption bands step across 762 nm which is easy to be obtained by non-cryogenic detectors. No other absorption spectrum of atmospheric constituents add to this band. Accordingly, the single station passive ranging based on O2 absorption characteristics and Beer's law was proposed. The absorption rate near 762 nm and 690 nm was used to calculate distance by baseline fitting. An inherent error term was found in application of Lambert-Beer law. It was defined as Nonlinear Initial Value (NIV). Its innate character is the radiation intensity between the lines caused by limitations of instrument characteristics. It can not be eliminated. The experimental platform was built to calculate the distance. For 113 degrees east longitude, 38 degrees north latitude, different seasons, times and weather conditions, a large number of samples were collected to establish the database. Each sample is a relationship between absorption rate and distance in one set of constraints. Empirical model was gotten through statistical fitting. The Nonlinear Initial Value (NIV) in theoretical model was corrected in real time. The distance inversion accuracy is 2.7%.
The problems of laser beam propagation in strong turbulence and the propagation along a slant path are hot and hard points in the subject of light propagation in random media. A model of the second-order moment of laser beam in any turbulence condition was elected. First the expression of the mutual coherent function was derived by using the extended Huygens-Fresnel principle. The model with three parameters for the second-order moment was created and the recursion formulas for the parameters were derived. The iteration formula of the parameters were used to calculated the effective beam radius and the length of coherence in the strong turbulence and in turbulence along a slant path. Compared with the results obtained by directly using the extended Huygens-Fresnel principle in strong turbulence, the effective beam radius obtained by the iteration formula is smaller and the corresponding coherence length is larger. The iteration method also shows that the characteristics of the uplink and downlink laser beam along a slant path are different.
2015, 44(1): 321-326.
Among the experiments of terahertz confocal scanning imaging, the image quality of the system remains to be improved for the reason that the terahertz laser used in the system can not constantly output and the signal acquisited by the detector is weak, etc. Digital image restoration is an effective method to save the cost and the space of confocal scanning imaging system. Based on the consideration above, a composite method was put forward for the use of the terahertz confocal scanning image restoration. This composite method is based on two-step background suppression, median non-local means (MNLM) filtering and gray level transformation. A comparison with median filtering, open operation and non-local means filtering was made after using this composite method on the real terahertz images. The results of real terahertz imaging processing show that this composite method has a good effect of image restoration and the image contrast is obviously enhanced in particular.
2015, 44(1): 327-334.
A new denoising algorithm was proposed to keep the fine features of hyperspectral remote sensing imagery effectively. Firstly, the noise-adjust principal components analysis (NAPCA) was performed on the hyperspectral datacube. Then output channels of the low-energy NAPCA were transformed into the wavelet domain by 2-D complex wavelet transform(CWT). The BivaShrink function was used to shrink the wavelet coefficients. And then 1-D CWT denoising method was used to remove the noise of the each spectrum of the low-energy NAPCA datacube. The AVIRIS images Jasper Ridge, Lunar Lake and Low Altitude were used for the simulated experiment. Compared with the HSSNR and the PCABS, the signal-to-noise ratio (SNR) is improved by 4.3-7.8 dB and 0.8-0.9 dB via the proposed method in this paper, which shows that the proposed method is feasible. It is shown that the proposed method is correctable and available according to the experimental results of the real datacube OMIS.
2015, 44(1): 335-340.
Leaf area index (LAI) is an important parameter of crop diagnosis and yield prediction. The LAI of winter wheat obtained from Beijing city had been estimated successfully by support vector machine regression (SVR) model built with LAI and wavelet coefficients of hyperspectral reflectance. The inversion results of this paper method and other five methods, such as selected vegetation indices and partial least-square (PLS) regression models, were analyzed. It was found that the sensitive bands to assess LAI were 680 nm, 739 nm, 802 nm, and 895 nm, and the corresponding wavelet decomposition scales were 8, 4, 9, and 8 determined by continuous wavelet transform(CWT), respectively. The decision coefficient (R2) of regression equation between LAI and wavelet coefficient was significantly higher than that of between LAI and canopy reflectance. The SVR model based on wavelet coefficients performed best with R2 of 0.86, and RMSE of 0.43, while the regression models based on two common spectral vegetation indices (NDVI and RVI) performed poor in estimating LAI of winter wheat's multiple birth period (R2 0.76, RMSE0.56). It can conclude that the pretreatment method of CWT is better effective for selecting sensitive spectral characteristics to LAI. Meanwhile, SVR is more suitable for developing model in LAI estimation than PLS regression. The combination of CWT and SVR is feasible to realize remote sensing inversion of LAI in the whole growth period of winter wheat.
2015, 44(1): 341-347.
Based on the equations of missile motion with respect to the desired terminal line of sight (DTLOS), the extended proportional navigation and extended optimal guidance law with impact angle constraint was deduced for lag-free system when-n power of time-to-go was introduced into the object function. The concept of the generalized optimal guidance law (GOPL) was proposed and the expressions and meaning of which in two different frames of reference were demonstrated. For the GOPL in the DTLOS frame, the analytical solutions of the closed-form trajectory were derived according to the method of power series and the analytical position, velocity and acceleration command were obtained. Finally, the analytical solutions were validated by the simulation results.
2015, 44(1): 348-353.
To solve the problem of the distribution uniformity and construction rapidity of guide star catalog, a method for guide star selection was proposed, which was based on Polar Coordinates Subdivision Method (PCSM) and separation-magnitudeweighting method. In order to ensure the distribution uniformity of guide star, the guide star was selected near the reference points on spherical surface neighbourhood, and to insure the results does not overstepp coordinate boundary; by using k-vector method to search candidate stars which was in reference points neighbourhood, the speed of the algorithm could be improved obviously; at last, considering the guide star performance of distribution uniformity and brightness, guide star was selected by separation-magnitudeweighting method. Simulation results show that the algorithm is simple in realization, and it has strong universality,and the selected guide stars have good uniform distribution.
2015, 44(1): 354-362.
A multiple features fusion and bandwidth adaptive mean shift tracking algorithm had been proposed. The iterative solution expressions of location and bandwidth had been established with fully parameterized bandwidth matrix based on M-estimator. The fused weight image had been produced with intensity and local standard deviation. The target template model had been generated by the combination of previous target template model and the mean value of the determined target models in the previous frames. An enlarged bandwidth matrix had been employed in the iterative solution of location vector to ensure location accuracy. To prevent the bandwidth from exploding in the presence of background clutter or imploding on self-similar target, regularization terms had been introduced. The visual results and evaluation measures show that the proposed tracking algorithm has the best performance compared with other three scale adaptive mean shift tracking algorithms.
2015, 44(1): 363-369.
Aimed at the maximum window size problem of LiDAR morphological method on unknown region, a morphological filter of iterative multi-scale opening by reconstruction (IMORF) was proposed on the basis of traditional morphological filtering algorithms. Multi-scale opening by reconstruction (MORF) was utilized to get maximum window size automatically, which can help user settle the suitable window size problem of unknown region. MORF was used iteratively to settle the classification error of the low objects that were nearby high and large objects. The experimental results for ISPRS urban data show that IMORF can classify terrain and off-terrain points effectively, and the mean of TypeⅠ, Type Ⅱand total error are 3.10%, 6.05% and 4.11% respectively. Compared with other traditional filtering methods,the mean of Type ⅠError and Total Error of IMORF are minimum with Type ⅡError increased not obviously.
2015, 44(1): 370-376.
Due to the strapdown image seeker cannot measure the inertial line-of-sight (LOS) rate directly, an arithmetic for estimating the LOS rate based on extended Kalman filter (EKF) was presented. The LOS rate decoupling expression under ideal condition was deduced. The model for estimating available guidance information based on EKF equations was established. Then according to the features of operational use of the man-portable guided munitions, the hit probability was analyzed by Monte Carlo method, the Circular Error Probable(CEP) met the operational requirements. The engineering feasibility of guidance system is verified by hardware-in-the-loop simulation. The results show that the arithmetic is an effective solution for estimating available guidance information for strapdown image guided man portable munitions. The technical approach of strapdown image seeker with estimation arithmetic of guidance information is suitable for engineering application.
2015, 44(1): 377-383.
The main purpose of carrier phase smoothing pseudo-range is to reduce large random error of pseudo-range measurement values, by using high-precision carrier phase measurement values as the supplementary information. In view of the unknown time-varying noise in GPS pseudo-range measurement, an algorithm of adaptive attenuation factor kalman filter (AFKF) was put forward, which was based on maximum a posteriori (MAP) time-varying noise statistical estimator. In order to avoid the divergence of filtering process, the effect of old data could be gradually forgotten by using estimator with attenuation weighted factors, while the proportion of new data could be increased. Simulation analysis was carried out on the measured data of tracking station of a International Global Navigation Satellite System Service (IGS), by using the AFKF algorithm combining with carrier phase smoothing pseudo-range principle. And the double differential and the three differential pseudo-ranges were proposed to intuitively reflect the effects of different algorithms. Experimental results show that the AFKF algorithm can obtain better effect in application of pseudo-range smoothing, compared with the standard KF algorithm.
2015, 44(1): 384-390.
In this paper, a double-threshold filter strategy was proposed and experimentally tested to improve the accuracy of photon counting imaging with an electron multiplying charge-coupled device, by taking into account the addition bias noise and Pseudo-photon noise during photon counting mode. Photon counting event detection was achieved by using amplitude threshold and frequency threshold filter to eliminate the bias noise and Pseudo-photon noise. Based on Bayesian estimation on multi-imaging, an optimal detection rule was found with minimum error cost. Experiment indicates that double-threshold filter strategy improves the photon detection accuracy than usual integrate method, and is suitable for imaging in ultra-low-light conditions such as biological dim light detection.
2015, 44(1): 391-397.
Different scales local binary patterns (LBP) extract different micro-structures, which contain important discriminative information for infrared face recognition. To capture the correlation between different scales, a new infrared face recognition method based on multi-scale LBP co-occurrence histogram was proposed in this paper. In traditional multi-scale LBP-based features, correlation in different micro-structures was ignored. To consider such correlation in infrared faces, co-occurrence histogram of multi-scale LBP codes was used to represent the infrared face. Multi-scale LBP co-occurrence histogram not only preserved great invariance to environmental temperature, but also greatly enhanceed the discriminative power of the descriptor as co-occurrence matrix of LBP code well captureed the correlation between different scale micro-structures around the same central point. The experimental results show the recognition rates of infrared face recognition method based on multi-scale LBP co-occurrence histogram can reaches 99.2% under same condition and 91.2% under variable ambient temperatures, outperform that of the classic methods based on LBP and multi-scale LBP histogram.
