2016 Vol. 45, No. 2
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In recent years,light-weight unmanned airborne spectral imaging technology has become hotspot research and attracted much attention in the field of spectral remote sensing technology at home and abroad owing to its plenty of advantages, such as free route, low cost. The mature application of staring acousto-optic spectral imaging technology with area FPA injects new momentum into light-weight unmanned aerial vehicle(UAV) remote sensing area. Firstly, the technical approach of staring spectral imaging technology was introduced, and then acousto-optic spectral imaging technology was discussed combined with lunar exploration application. After the completion of developing the UAV payload prototype, the application experiment had been carried out, and the test data was analyzed and evaluated. Finally, the application of light-weight UAV payload based on acousto-optic spectral imaging technology was also discussed and looked ahead in the paper.
2016, 45(2): 203002.
doi: 10.3788/IRLA201645.0203002
The charge collection efficiency of electron bombarded active pixel sensor(EBAPS) was simulated while the EBAPS with uniformly doped P type substrate. The photoelectron scatting trajectories in dead layer and electron multiplier layer were simulated based on the low-energy electron-solid interaction model and Monte Carlo method. Meanwhile the influence factors how affecting the energy loss rate were studied. According to semiconductor theory, the influence factors(B atoms doping concentration, film thickness and the incident electron energy) how affecting the charge collection efficiency were studied. The final charge collection efficiency's simulation results are consistent with the reported(4 keV, uniformly doping) measured results, which means the simulation result can provide theoretical guidance for the fabrication of high gain EBAPS.
2016, 45(2): 204001.
doi: 10.3788/IRLA201645.0204001
The windows of IR detection systems becomes the main factor of the aero-thermo-radiation effect, which reduces the performance of these IR systems, or even makes these systems fail. By analyzing thermal radiation propagating in IR windows, a participating medium, an evaluation method for aero-thermo-radiation effect of the non-isothermal IR windows was proposed, based on the experimental results of the isothermal state, include self-radiation and transmittance. Aim to an MWIR detection system of a hypersonic vehicle, aero-thermo-radiation effect of a sapphire IR window was evaluated in 3.7-4.8m. The results indicate that, as the sapphire IR window is exposed in high-temperature and high-speed airflow, the aero-thermo-radiation effect of the window intensifies as temperature rises rapidly, the transmittance drops about 10%, still bigger than 0.9, otherwise the self-radiation enhances 458 times approximately, equal to that of blackbody about 125℃. For sapphire windows in 100-350℃, which thickness are smaller than 20 mm, as thickness increases, the transmittance decreases, self-radiation increases, and total radiation behind sapphire windows is increased, of which the ratio of self-radiation increases. So, self-radiation would drive detector into saturation easily, of which the influence on the MWIR detection system is bigger than that of transmittance.
2016, 45(2): 204002.
doi: 10.3788/IRLA201645.0204002
A technique of dynamic IR scene generation based on MEMS was presented. The theoretical model of IR scenes display film based on visible/infrared image film transducer was established. The MEMS technological processes of fabricating the film were introduced. The film with 512512 pixels was produced, and the pixel size of the film was 35m. Based on the IR scene generation film an IR dynamic scene generator was built. The performances of the IR dynamic scene generator were studied experimentally. The IR scenes display film based on visible/infrared image film transducer can be used in two wave bands from 3m to 5m and 8m to 12m. The spatial resolution of the IR dynamic scene generator is 14 lp/mm. In the wave band from 3m to 5m, the equivalent blackbody temperature can be from 250 K to 440 K, and in the wave band from 8m to 12m, the equivalent blackbody temperature can be from 250 K to 400 K.
2016, 45(2): 204003.
doi: 10.3788/IRLA201645.0204003
Infrared focal plane array rotation search system catches attention because of simple system structure, high flexibility and low cost compared with the linear array search system. The dim-small target detecting technology under complex background is a difficult subject in infrared focal plane array rotation search system. In order to effectively suppress background noise and reduce false alarm caused by complex background, constant false alarm rate algorithm based on weighted feature of linear target was presented aiming at the research of imaging properties of infrared focal plane array rotation system. Firstly, the discrete potential target image was obtained initially by background suppression and threshold segmentation. Next, three characteristics of linear target were analyzed and the total weighted value was calculated by quantifying and weighting. Finally, the weighted value was mapped to the discrete target image and the image sequence about the weighted value was achieved, then a new segmentation threshold obtained by CFAR algorithm was applied to suppress the background interference and reduce false alarm and false positives. The experiment results show that the proposed method can significantly reduce the false alarm caused by the complex background in infrared focal plane array rotation search system and can ensure to detect the dim-small target.
2016, 45(2): 204004.
doi: 10.3788/IRLA201645.0204004
Water-based infrared stealth coating in 8-14m wavebands was studied from three aspects, matrix resin, filler and the properties of coating. Infrared emissivity in 8-14m wavebands was measured by infrared emissometer, infrared absorption was measured by infrared spectrometer(IR), and the surface morphology of the coating was observed by scanning electron microscope(SEM). The results show that acrylic resin are infrared transparent in 8-14m wavebands and suitable for matrix resin; the aluminum paste with low infrared emissivity is easily disperse in water-based coating and suitable for filler. The size, content and form of filler are great influence on the emissivity of coating. Steel plate was chosen as a substrate, the acrylic resin as matrix resin. When the size of the aluminum paste is 2000 mesh, the aluminum paste with 50% leafing aluminum is chosen as the filler, and the content of filler is 15%, the coating infrared emissivity is 0.34.
2016, 45(2): 204005.
doi: 10.3788/IRLA201645.0204005
Test conditions as excitation intensity, excitation duration and engagement force between horn and test object are important factors affecting defect thermal signal in sonic infrared imaging. Experimental statistics and simulated results show that the increase of the excitation intensity and the excitation duration will enhance crack heating. However, the increase of the engagement force will enhance firstly and then weaken crack heating. Moreover, the effects of the test conditions on crack heating are interactive, and inappropriate test conditions will induce a test-stopping alarm. Based on the effect analysis of testing conditions on crack thermal signals and alarm incidents, a multivariate nonlinear regression model and a logistics regression model were adopted to estimate probability of detection and alarm during test, which will finally determine the value range of test conditions. The optimization methods proposed in this paper will provide theoretical direction for test scheme in sonic infrared imaging technology.
2016, 45(2): 204006.
doi: 10.3788/IRLA201645.0204006
Based on the basic theory of infrared radiation, infrared tri-wavelength vectors group altering low coupling between emissivity and infrared temperature measurement was derived to isolate the object emissivity and infrared temperature measurement. In order to optimize the tri-wavelength vectors group, a non-dimensional emissivity model was established and the most suitable wavelength range was identified. Aiming at optimizing the linear function of emissivity, the bending index n was introduced. The appropriate wavelength range to guarantee exactness of result of tri-wavelength vectors group was presented. The tri-wavelength measurement was demonstrated in a laboratory experiment with four sulfide ore samples. The results show that the fitting of tri-wavelength measurement with true temperature is better than that of common infrared temperature measurement. The fractional error of tri-wavelength measurement significantly is less than the common. The availability and accuracy of tri-wavelength measurement are verified. The tri-wavelength measurement ensures the measurement accuracy as well as expands the scope of common thermal infrared imager application and ensures the numerical accuracy of infrared prediction in the spontaneous combustion of sulfide ores.
2016, 45(2): 204007.
doi: 10.3788/IRLA201645.0204007
Pulsed infrared thermal wave testing, which typically uses reflective-type incentives, is a new non-destructive testing technology. In view of the reflection method with big defect depth quantitative detection error, transmission infrared thermal wave method was systematically analyzed in order to improve the detection precision. The principle of infrared measurement of defect depth was discussed by analyzing the material in pulsed thermal excitations of one-dimensional heat transfer model. The relationship between the characteristics of time and defect depth was established by the peak time method of the first order differential of surface temperature, so the quantitative detection on the depth of defect was realized. The sample of PVC flat with artificial slot wedge defects was used. The depth of defects were detected by comparative experiments between transmission and reflection methods, and the measurement errors were analyzed. The results show that reflection method in quantitative calculation for defects requires selecting reference region, while transmission method does not rely on the reference avoiding the error resulted from it. Moreover, transmission method directly heats surface defects, so short response time can be obtained and the defect depth precision are improved greatly by solving the characteristic time of the defect.
2016, 45(2): 206001.
doi: 10.3788/IRLA201645.0206001
According to the model, which is based on the three-level rate equations, the threshold characteristics of side-pumped Rb vapor laser was fistly analyzed. The nonlinear absorption of a Bar laser side-pumped Rb vapor laser and the pumped laser propagation in the cell were simuiated in this model. In addition, the distribution of small signal gain under the condition of pumped threshold was well described by this model. In an example, the influence of cell's length, temperature, gas pressure, gas composition, focus length of focus lens and the parameters of resonant cavity on side-pumped Rb vapor laser was analyzed. The result shows that optimizing proportion of helium and methane can decrease threshold power effectively. Threshold power has combined impact of temperature and cell's length. High window transmittance and no more than 70% output coupling can make threshold keep in a lower level.It will be helpful to design key components and to optimize systems.
2016, 45(2): 206002.
doi: 10.3788/IRLA201645.0206002
The line width of pulsed quantum cascade lasers(QCL) increases with the device heating up during the driving pulse, so QCL drivers need to generate ultra-short current pulse. Generally, pulses of 5 ns to 15 ns durations can reach the Fourier transform limit. However, due to the existence of parasitic parameters, narrow pulses will lead to overshoot or oscillation. Therefore, the current commercial QCL drivers can not meet this requirement. To obtain narrower line width of QCLs, a frequency compensation method based on conventional pulse constant current circuit was proposed in this work to eliminate overshoot and oscillation. And a stable pulse laser driving circuit was also designed which can output 0-2 A pulse current, with 8.4-200 ns pulse width, 4 ns rising time, and 1% overshoot. Function test was carried out with a QCL with 4.6m center wavelength made from Institute of Semiconductor of Chinese Academy of Sciences, and a Fourier transform infrared spectroscopy. The laser line width decreased almost linearly from 0.35 cm-1 to 0.12 cm-1, when the driving pulse width decreased from 100 ns to 10 ns. Experimental results show that the driver is able to output stable narrow pulses, which is suitable for narrow line width driving of QCLs and their applications.
2016, 45(2): 206003.
doi: 10.3788/IRLA201645.0206003
It is necessary to know the laser scattering characteristics of sea surface in different sea conditions when designing the laser radar using in super-low altitude. According to the design requirements, low altitude radar work situation was simulated by the wave tank facility to solve the difficulty of actual sea environment testing, and the quantitative control of influence factors of sea surface laser scattering was realized. By using the laser scattering measurement system, the near field laser scattering data of various states and different beam irradiation angles were obtained, and the laser scattering characteristics of sea surface with regular sinusoidal wave and irregular PM spectrum were given by statistical analysis. The result shows that there are large differences between sea surface and Lambertian surface and mirror reflection should be main ingredients in the sea surface scattering distribution. Laser scattering echo fluctuation changes with the spatial wavelength of the sea surface wave and the cattering size increases with the increase of grazing angle. Furthermore, the higher the sea condition is, the stronger the corresponding scattering echo is at a fixed grazing angle, but scattering echo size will not change with the sea conditions when the grazing angle is large enough.
2016, 45(2): 206004.
doi: 10.3788/IRLA201645.0206004
Pulsed laser radar detection performance is associated with laser optical pulse emitted by laser light source, and the performance of power supply directly determines the quality of optical pulse. According to the requirements of laser radar system, the high power MOSFET was used as switching device and the driving circuit model was established, designed and analyzed. The driving circuit with 10 ns minimum pulse width, 3.5 ns rising time and 50 kHz pulse repetition frequency was obtained successfully after much experiments. The optical peak power of LD nearly reached 60 W, and it was successfully applied in laser radar as laser emission part. The 3 cm/10.77 m accuracy can satisfy the requirement of a laser radar.
2016, 45(2): 206005.
doi: 10.3788/IRLA201645.0206005
A three-dimensional finite element analysis thermal model for laser transmission welding technique of polycarbonate(PC) was developed. Power distribution of moving heat source was implemented into DFLUX subroutine, written in FORTRAN programming language to simulate the temperature distribution during the laser transmission welding process. The effect of process parameters on the weld strength and weld width was analyzed. Data gained by numerical simulation was compared to data obtained by laser transmission welding experiments, and good agreement was found between the two trends. It was observed that for a particular value of the laser power, good bonding between two thermoplastic materials is a function of laser scanning speed. Too high speed will not produce any significant increase in temperature at the two material interfaces to have a good chemical bonding. On the other hand, too slow speed will cause excessive increase in temperature resulting in burnout condition for polycarbonate. For the ranges of parameters investigated in the current study, it was observed that for a laser heat flux of 40 W, good bonding occurs for a laser scanning of 40 mm/s. This shows that the finite element analysis can be used for optimization of process parameters.
2016, 45(2): 206006.
doi: 10.3788/IRLA201645.0206006
Researches on the laser deposition repair of GH4169 nickel-based superalloy with defects of through-groove damage were conducted. The reasons of occurring defects such as gas porosities and ill bonding in the repaired zone were analyzed. And flawless samples were obtained through optimizing laser process parameters. The microstructure characteristic and mechanical properties of laser deposition repair component were investigated, and the local heat treatment of the laser deposition repair component was done. The results indicate that there is a dense metallurgical bond between the repaired zone and the substrate with the optimized process parameters. The tensile strength of laser deposition repair component can be significantly improved with the local heat treatment.
2016, 45(2): 206007.
doi: 10.3788/IRLA201645.0206007
The laser drilling holes processing experiment was conducted on the silicon under the radiation of a 1064 nm nanosecond repetitive pulse laser. Variation rule of holes' diameter transferring with laser pulse number and the depth of the holes could be both observed through this experiment. Meanwhile it analyzed the thermodynamic process of pulse laser irradiating silicon as well. The result shows that being confined by the narrow hole, the hot plasma expands rapidly inside the channel. It transmits a large fraction of its energy to the hole walls by radiative and convective heat transport, thereby contributing to the radial expansion of the hole. The hole depth growth rate have linear increase with pulse number when the pulse number is under 6, after that it becomes slower and slower until remain stable, which is mainly due to plasma shielding effect.
2016, 45(2): 206008.
doi: 10.3788/IRLA201645.0206008
Groove surface texture was widely used in the frictional mechanical part, such as mechanical seal, cylinder liner and piston ring, whose performance depends on its geometric parameter of the texture. Therefore, it is important to process the surface texture efficiently with accurate geometric parameter. Groove surface textures were fabricated on high-speed steel by lasers with different output powers, repetition frequencies and scanning speeds. Comprehensive experiments with three levels and three factors were designed to study the relationships between texture topographies and the three processing parameters. The experimental results showed that the depth and width of the groove surface texture slightly increased firstly and then decreased with the rise of laser repetition frequency. Moreover, with the incensement of laser scanning speed, the depth of the groove surface texture increased firstly and then decreased, but the width of the groove surface texture continued to rise. Variance analysis showed that laser scanning speed and repetition frequency had more obvious influence on the width and depth of groove surface texture than the output power. High-quality groove surface texture would be processed on the high-speed steel by laser with the output power of 10W to 14W, the repetition frequency of 20kHz to 30kHz and the scanning speed of about 1000mm/s. Meanwhile, indentation testing indicated that the hardness on marginal area of surface texture markedly increased.
2016, 45(2): 211001.
doi: 10.3788/IRLA201645.0211001
The profiles of spectral pass bands' limb radiance by SABER(Sounding of the Atmosphere using Broadband Emission Radiometry) were simulated in the bands of 15m and 4.3m emission for CO2 by using the updated software of SHARC, and the simulated results were compared with corresponding SABER measurements to analyze the CO2 non-LTE radiative transfer properties and to validate the model. The comparisons show that SHARC can simulate the middle latitude atmosphere condition's CO2 limb radiation with a reasonable accuracy for applications. However, for some special atmosphere conditions, such as Arctic summer's atmosphere, the model has some deviations because of its algorithm's shortcoming. It is expected to improve the algorithm to contain more sophisticated chemical-kinetic processes and achieve better middle and upper atmospheric parameters, which make more accurate simulation of non-LTE radiative transfer properties.
2016, 45(2): 211002.
doi: 10.3788/IRLA201645.0211002
Under the given condition, reflected intensity of the top of atmosphere and transmitted intensity arriving at the ground were simulated when aerosol particles average effective radius and complex refractive imaginary part index was different, as well as the effect of aerosol vertical distribution on reflection and transmission intensity and flux of different height. The result shows that when the aerosol optical thickness is fixed, the effect of aerosol vertical distribution on reflection and transmission is great under 15 km, and the smaller aerosol particles average effective radius and complex refractive index imaginary part of aerosol particles, then the larger reflected intensity of the top of atmosphere and transmitted intensity arriving at the ground. Therefore, in order to accurately calculate atmospheric radiation, not only the aerosol optical thickness but also aerosol particles average effective radius, complex refractive index and aerosol vertical distribution should be taken into consideration, and just using the empirical value of the aerosol model will bring bigger error.
2016, 45(2): 211003.
doi: 10.3788/IRLA201645.0211003
The temporal characteristics of Aerosol Optical Depth(AOD) and Angstrom exponent were analyzed using the sun photometer(CE318) data from September 2012 to August 2014 in north-west region of Hefei. It shows the aerosol optical depth in Hefei is higher in the whole year. The annual mean AOD is 0.600.15 from September 2012 to August 2013 and 0.730.23 from September 2013 to August 2014. The aerosol wavelength exponent in Spring is the least and the optical depth in the autumn is the least. The study of AOD and atmospheric water vapor content shows a positive correlation. The back trajectory analysis indicates that Hefei area is mainly influenced by northwest currents(about 42%) in spring, influenced by southward currents(about 50%)in summer, influenced by northward currents(about 39%) in autumn and influenced by northwest in the high altitude. The relationship between MODIS retrieved and sun photometer CE318 shows a good agreement and the correlation coefficient is above 0.70.
2016, 45(2): 217001.
doi: 10.3788/IRLA201645.0217001
In order to realize the best performance receiving ranging system based on single photon counting, based on the constant integration time, the system output SNR and range precision were studied with the increased laser power. First, the arm probability was introduced to the linear SNR model based on fixed frequency multi-pulse accumulation detection system. Monte Carlo simulation and theory simulation all proved that with the increased laser power, the SNR got larger and became stable. Then the range deviation model was settled, with the increased laser power, range precision enhanced and became stable by Monte Carlo simulation. Experimental results indicate that based on high background noise, the maximum of SNR can be obtained with emitting laser power at about 400W at 50 ms integrated time. Range precision reaches the optimal level at 6 mm. Finally, theory and experiment all prove that the optimal performance receiving of SNR and precision is achieved on single photon counting ranging system.
2016, 45(2): 217002.
doi: 10.3788/IRLA201645.0217002
In order to ensure the measurement accuracy of precise photoelectric encoders in harsh working environment, a kind of automatic compensation system based on the high-resolution digital potentiometer, DSP and CPLD for the Moire fringe photoelectric signal was established. Firstly, the principle and composition of automatic compensation system was introduced. Meanwhile, the compensation algorithms for the components of Moire fringe signal deviation was integrated. And the compensation model for photoelectric signal subdivision error was established. The system hardware design and software design were expounded. The system error of the compensation system was further analyzed. A 24 bit photoelectric encoder was selected as the experimental object to analyze and test the compensation system. The experimental results show that DC level drift, amplitude deviation, orthogonality deviation, and the second, third and fifth harmonic deviation are simultaneously compensated. The actually static subdivision error is reduced to 0.61. The compensation system can realize the automatic correction of Moire fringe signal subdivision error in the working state.
2016, 45(2): 217003.
doi: 10.3788/IRLA201645.0217003
As the large optoelectronic tracking device has the features of high tracking and measuring precision, large inertia and small field, it has no ability to search targets in large sky scope. Generally, it depends on the leading information from radars to find targets. Once the information's error exceeds the field of the device, it's hard for the optoelectronic tracking device to find the target. A quick helical search method in small sky scope was proposed based on the leading information. According to system model simulation and experiments, the method helped the large optoelectronic tracking device to capture target quickly when the target's leading information error outranged the field. The acquisition probability of targets was increased from 20% to 70% when the leading information error was less than twice of the device field. The turntable runned smoothly when applying this search method, and the searching parameters can be changed flexibly according to properties of different optoelectronic devices, features of targets and targets guiding error. It greatly improves acquisition probability of targets, and it is a kind practical and effective method for large optoelectronic device to find targets quickly in small sky scope. This method has high versatility.
2016, 45(2): 217004.
doi: 10.3788/IRLA201645.0217004
The accuracy of traditional optical power acquisition instruments is not high, so they are unable to show the change of the optical power clearly in short term during the experiment, while data collection system for collecting voltage can be a good solution to this problem. On the basis of introducing working principle of 1310 nm SLD light source, a driving circuit was designed, which can make SLD operate steadily by controlling current under the condition with a constant temperature. With the theoretical analysis and experimental verification, a new method of monitoring SLD output optical power by its voltage drop was provided, then true and reliable experimental data were obtained. From the driving experiment for SLD, it has proved that the output power has a certain relationship with driving current and voltage, and results show that the output power has a good linear relationship with the current, a good positive correlation index with the voltage. Taking advantage of collected voltage to monitor SLD output light power can greatly improve the test precision and data resolution, at the same time provides new electrical parameters for the SLD degenerate life test.
2016, 45(2): 217005.
doi: 10.3788/IRLA201645.0217005
The main errors considered during online calibration of strapdown inertial navigation system(SINS) include bias error, scale factor error, installation error. The more the error parameters, the difficult calibration process, and the rocket can not do line movement during calibration stage before launch, which let the most of the error parameters unobservable. If the main parameters affecting navigation accuracy can be determined, the calibration algorithm and the calibration process can be simplified, the efficiency of calibration is improved. Based on this idea, the rotation projectile was compared to the rotation INS, starting from the error equation, the errors on the flight onboard INS was analyzed by extracting the DC component, the main parameters affecting navigation accuracy were drawn. Then a way was designed by using the speed error change around motorization maneuver. The differential equations needn't be solved, the amount of computation was reduced greatly. Simulation results show that simple calibration scheme solves the problem of lack of incentives during launch preparation stage, and the problem can not be effectively calibrated.
2016, 45(2): 217006.
doi: 10.3788/IRLA201645.0217006
The international completed optical/infrared telescopes were reviewed and summarized, the construction of the next generation of telescopes was analyzed, including scientific purposes, optical structure, carry instruments, performance parameters and so on. The technical characteristics and development trend of the next generation of telescopes were studied. Lessons from abroad were drawn in such aspects as planning, engineering application, combining with the reality of China, some thoughts and suggestions were put forward.
2016, 45(2): 217007.
doi: 10.3788/IRLA201645.0217007
The progress of Mars exploration and the science objective of Mars camera were presented. The characteristics of space camera and Mars camera were analyzed. The research achievements of the research group in the past several years on Mars camera were presented. Research contents include:spectrum characteristics of Mars surface material, spectral band setting of Mars exploration optical remote sensor, nadir illumination analysis at orbit arc near Mars, solar altitude angle changes with time at orbit point near Mars, histogram distribution characteristic analysis of Mars surface elevation data, image motion caused by velocity to height ratio error because of Mars surface elevation, Mars camera engineering model research, imaging experiment with Mars camera engineering model etc. It summarizes the past research and may facilitate further research on the Mars camera. The manufactured Mars camera fits for observation imaging of Mars surface on Mars orbit.
2016, 45(2): 218001.
doi: 10.3788/IRLA201645.0218001
In order to improve the dynamic performance of infrared seeker's stabilization platform and diminish the negative effect of vibration environment on the stabilized accuracy and image quality of electro-optical load, a topology optimization based on the variable density theory was studied. In the topology optimization of the main frame of infrared seeker's stabilization platform, the maximum stiffness was taken as an objective function and the volume ratio constraint was taken as response functions by using the software of NX/TOSCA. The stiffness and modal performance of the main frame structure after optimization were analyzed by comparing with experience design. The results show that the mass of the main frame is reduced tremendously by 32.4% under the condition of the improved dynamic performance, the maximum deformation is reduced from 3.2m to 2.8m, and the first order natural frequency is improved from 1567 Hz to 1953 Hz, that is beneficial to the lightweight level of ascension and the performance improved. Finally, the dynamic performance of the main frame is verified by vibration test and stabilized accuracy test, which proved the result of the topology optimization. This topology optimization method will provide help to structure design of the other important parts.
This paper focuses on the thermal barrier effect of magnesium-fluoride conformal dome. Firstly, the real flight process was simulated and a finite element analysis model of the fairing aerodynamic heating and internal heat transfer were established under different flight speeds, the aerodynamic-thermal loads and the average temperature of dome was calculated. Secondly, according to the basic principles of infrared detection, each temperature dome heat radiation and its effects on the imaging quality of the detection system were analyzed, the critical temperature of dome was calculated when detector reached the saturation condition to study the mechanism of the thermal barrier effect. Finally, imaging tests were carried out for validation of analytical results. The results show that the critical temperature of dome when detector reaches the saturation condition is about 460 K, the thermal barrier effect is remarkable under the condition of Ma=4 and final guidance in Ma=3. In order to accelerate the infrared imaging guided weapons flight speed, the thermal barrier effect must be corrected. The conclusions has certain reference for understanding the mechanism of the thermal barrier effect and correction methods.
2016, 45(2): 220002.
doi: 10.3788/IRLA201645.0220002
Titanium alloy is well known with difficult machinability, which limits its application in many fields unavoidably. In the current study, electric pulse treatment(EPT) was firstly employed to treatment the titanium alloy. The microstructure and mechanical properties had been changed after the treatment. It is found that EPT technology can improve plasticity of titanium alloy, and the hardness, elasticity modulus and yield stress of titanium alloy will decrease after EPT. The result of cutting test proves that the EPT can decrease the cutting force and improve the surface quality.
2016, 45(2): 220003.
doi: 10.3788/IRLA201645.0220003
Precision mechanical polishing was one of the primary techniques for the fabrication of optical components with both high-precision and high-quality surfaces. However, few studies have been reported on the removal rate characteristics of silicon carbides(SiC) in high finish quality polishing processes. SiC was an important ceramic material for many critical industrial and aerospace applications. A theoretical investigation and a series of polishing experiments in computer controlled precision polishing process were presented. And a better understanding of removal mechanisms of SiC surfaces was also proposed for optimizing surface quality. Head speed, tool pressure, tool offset and polishing angle were selected to analyze the surface removal tendency. The Taguchi method was used as an efficient method to optimize the polishing conditions and reduce excessive experimental requiring. Moreover, the results imply the polishing parameters combinations required to achieve the desired surface finish and better application of removal characteristic.
2016, 45(2): 222001.
doi: 10.3788/IRLA201645.0222001
A prototype for the typical optical single-sideband(SSB) modulated radio-over-fiber(ROF) system was presented by employing a phase-shifted superstructure Bragg grating. The grating has different transmission characteristics with different oblique angle. So, the different transmission peak could be obtained with different phase shift inserted into different positions. Then it was used in SSB modulation scheme as a filter. In the scheme, the lower sideband experiences higher attenuation due to the negative slope in reflectivity spectrum. Thus the conversion from dual-sideband(DSB) to single sideband with carrier(SSB+C) can be easily achieved by using only one phase-shifted superstructure fiber Bragg grating. Also, the optical carrier-to-sideband ratio(OCSR) can be optimized by using grating with different oblique angle. In this paper, the OCSR could be optimized from 33.02 dB to 1.31 dB and a 60 GHz millimeter-wave was detected after photodiode. What's more, a min BER of 1.966e-44 with 30-km fiber length was implemented which means that only using one phase-shifted superstructure FBG can improve the link performance greatly.
2016, 45(2): 222002.
doi: 10.3788/IRLA201645.0222002
To study the effect of local oscillator power, detector characteristics and polarization on signal-to-noise ratio(SNR) of the space coherent optical communication, the SNR were studied under different working conditions. The effect of characteristic parameters of the detector under different work status and the local oscillator power on the SNR was discussed. The effects on SNR was verified through the experiment. Results show that the characteristic parameters of the detector limit the value of the local oscillator power. Actually, the maximum SNR is less than the theoretical value in coherent optical communication, the optimum value of local oscillator power is greater than the theoretical value, and the closer the two polarization direction of the light beam, the greater the output SNR, the smaller the optimum value of local oscillator power.
2016, 45(2): 222003.
doi: 10.3788/IRLA201645.0222003
The polarization dependent gain(PDG) of fiber Raman amplifiers(FRAs) with bidirectional pumps was investigated systematically for the first time, by numerical method based on the nonlinear coupled equations describing the properties of fiber Raman amplifiers. The FRA with four pumps has 14 structures. First of all, the general PDG characteristics of the 14 different FRAs were investigated, and then the PDG characteristics of a specific structure were analyzed in detail, including the PDG induced by pump-signal Raman interaction, by pump-pump Raman interaction and by signal-signal Raman interaction. The results show that(1) the more backward pumps generates the smaller mean PDG values under constant number of pumps,(2) when the total number of pumps and the number of backward pumps are both constant, the backward pump wavelength has little effect on the PDG, and(3) the PDG of a bidirectionally pumped FRA is mainly determined by pump-signal Raman interaction. These results are useful and important for reducing the PDG of an FRA.
2016, 45(2): 222004.
doi: 10.3788/IRLA201645.0222004
An up-tapered fiber strain sensor based on Mach-Zehnder interferometer(MZI) was proposed and demonstrated. With the MZI as a filter, the laser was finally generated in the optical fiber ring resonator through comb filtering at the gain spectrum of erbium-doped fiber. The MZI could work as filter as well as carry on the sensor of optical fiber axial strain, and thus realize the output wavelength of the laser blue-shifts with the increase of strain. The experiment result shows that the sensor around the wavelength of 1557 nm exhibits the axial strain sensitivity of 3 pm/ by monitoring the wavelength shift. Moreover, the up-tapered MZI fabrication process is very simple, cost effective and high mechanical strength.
2016, 45(2): 228001.
doi: 10.3788/IRLA201645.0228001
For the problem of deblurring of multiple observed images of moving objects with different blur kernels, a joint three-dimension deblurring method for multiple observed images was proposed. Unlike existing deblurring methods to remove 2D blur for single observed image without considering relationship of blur kernels in multiple observed images, the relationship of different PSF paths of multiple observed images was explored. The movement in three-dimension space was projected into each observed image planes, hence, the inherent relationship between the two PSF paths of two observed images can be set up. At first, motion blur kernels of two view images were estimated using single observed image debluring method and the blur kernels with one pixel width was refined. When having estimated two PSF paths, the other PSF paths could be calculated and optimized by using the relationship of PSF paths in multiple observed images. Then 3D blur of the observed images could be removed by using the proposed method. The experiment results for multiple observed images demonstrate that the proposed approach is efficient and effective in removing 3D blur and reconstruction.
2016, 45(2): 228002.
doi: 10.3788/IRLA201645.0228002
For the problem of high-precision tracking of space area targets, a method of tracking area targets with high-precision was proposed. Sum of weighted absolute differences(SWAD) matching algorithm and sub-pixel fitting algorithm were used to extract precise position of the target. The template was updated during tracking. The conventional infinite impulse response filter approach used for template updating was improved. A variable coefficient template updating method was proposed. This method had small amount of computations, and creditability evaluation was not needed. The template updating coefficient was determined by gray values of current template and current best matching area. Images with different target brightness, and images after scale transformation for simulating target attitude change, were used to compare matching error of proposed method and conventional method. Results show that method proposed in this paper has better adaptability to changes of target attitude. Finally, collimator and simulation target were used to simulate far-field non-cooperative target. Indoor demonstration experiment was set up and the experiment shows that high-precision target tracking with image matching is feasible.
2016, 45(2): 228003.
doi: 10.3788/IRLA201645.0228003
The huge amount of hyperspectral images creates challenges for data storage and transmission, thus it is necessary to employ efficient algorithm for hyperspectral images compression. An efficient lossy compression algorithm based on spectral classification was presented in this paper. The C-means algorithm was performed on the hyperspectral images to realize the unsupervised classification. According to the classification map, an adaptive Karhunen-Love transform was performed on each class vector with the same spatial location in the spectral orientation to remove the spectral correlation, and then two dimensional wavelet transform was performed on each principle component. In order to achieve the best rate-distortion performance, the embedded block coding with optimized truncation coding was performed on all the principle components to produce the final bit-stream. Experimental results show that the proposed algorithm outperforms other state-of-the-art algorithms.
2016, 45(2): 228004.
doi: 10.3788/IRLA201645.0228004
In view of the fact that spatial resolution and spectral resolution of remote sensing images taken by satellite becomes more and more greater, in some applications, it is needed to compress the multispectral images. An image registration method by phase correlation and affine transformation was proposed in order to improve the multispectral image compression quality. The proposed method effectively improved the correlation between the image spectrums. Aiming at the multispectral image compression problem, the Karhunen-Love, KL transform method, which was used for eliminating correlation between spectrums in the image, and the low complexity two-dimensional wavelet encoding method were put forward. Compared with JPEG2000 independent compression method for each spectrum in an image, the Peak Signal to Noise Ratio, PSNR of decompression image by the proposed method improved 2.1 dB in average. Experimental results show that, under the same compression ratio, in this paper the proposed method can obtain better image quality than the JPEG2000 spectral image independent compression method.
2016, 45(2): 228005.
doi: 10.3788/IRLA201645.0228005
Polarization imaging technology is a method that acquires the object images by collecting the polarization information of the target radiation or reflected signals. In particular, compared with the light intensity detection, it has unique advantages in the artificial target detection and surface recognition. Due to the short range and low quality of the conventional polarization imaging in complex imaging environment, a new kind of polarization imaging technology based on compressed sensing was proposed. The basic principle of compressed sensing theory was elaborated. By constructing reasonable sampling matrix and reconstruction algorithm, the specific imaging system was designed. Besides, the feasibility of this technology was confirmed through the imaging experiment. The study results in the air show the system can reconstruct the polarization images of the pre-positioned target. Additionally, in the existing experimental conditions, some measures are investigated and proposed to improve the system imaging performance.
2016, 45(2): 229001.
doi: 10.3788/IRLA201645.0229001
Using the way of laser in centimeter scale space debris removal has been the hot research topic around world.The characteristics of impulse coupling and reducing the speed and de-orbit with space debris induced by laser irradiation are utilized in their removal.According to the two characteristics,four key problems,that were space debris plasma plume induced by laser ablation,measurement of space debris impulse by laser ablation,space debris orbit estimating and laser parameters in space debris removal,were discussed in detail.The concerned technology difficulties,the adopting research methods and the realized ability level were analyzed.Based on the above discussion,it can provide solid basis for its future project realization.
2016, 45(2): 229002.
doi: 10.3788/IRLA201645.0229002
The effect of expansion moving and impulse coupling in pulse laser and aluminum target debris were investigated, the spatial and temporal distribution rules of velocity and pressure in aluminum target debris and plasma were analyzed by numerical simulation, and the quantitative relation of impulse coupling coefficient and laser power densities was also discussed. Further, a dynamic deorbit model of ground-based pulse laser irradiating small scale space debris in low earth orbit(LEO) was established, and the effects of orbital eccentricity and perigee altitude with different number of pulses were simulated in the process of removing small scale space debris in LEO. The results indicate that the small scale space debris in LEO could be deorbited availably by optimal impulse coupling coefficient when the number of pulses was 180 times, orbital eccentricity was 0.071 based on the condition of this paper. The prospective achievements can provide technical guidance for the application of high power laser removing space debris in LEO.
2016, 45(2): 229003.
doi: 10.3788/IRLA201645.0229003
To contribute to the improvement of China's radar debris tracking capability and capacity, efforts have been made to make the newly built Qujing incoherent scattering radar capable of LEO debris surveillance, in addition to its standard space environment observations. Firstly, a brief introduction of the Qujing radar and its operational parameters were given, followed by the discussion of the debris tracking sensitivity. The modified radar system was operated on November 18, 2014, to experiment its debris tracking capability. The experiments show that the measured ranges agree well with external values, and this confirms the debris tracking feasibility of the Qujing radar. After the planned system upgrades, the Qujing radar is expected to track debris objects as small as 5 cm, and the tracking capability and capacity, including the natural celestial bodies, would be greatly enhanced through the networking with other radars.
2016, 45(2): 229004.
doi: 10.3788/IRLA201645.0229004
Optical angles and laser ranging data are two common types of space debris accurate tracking data. After a great deal of simulated experiments, the performance of debris orbit determination and prediction were investigated using these two types of data, in an effort to understand their characteristics and use these sparse data in a better manner in the future. At first, the simulated angular data of 1 accuracy and ranging data of 1 m accuracy were generated using Consolidated Prediction Format(CPF) orbits of Starlette and Larets in January, 2015 for four observation stations in China. Then, orbit determination cases using data from single station and two stations were formed. For all orbit determination cases, data from either full pass or shorter pass were used in orbit computations. Result shows that the Orbit Prediction(OP) results using angular data are more stable than those using ranging data. Specifically, about 75% of 1-2 day OPs using angular data of two 90 second passes have accuracy better than 20. It also shows that the OP performances using two single-station passes are very similar to those using two passes from two stations.
2016, 45(2): 229005.
doi: 10.3788/IRLA201645.0229005
The structure of laser retro-reflector array dominates the distribution of the effective reflection area and influences the intensity of echo signals. However, for the special purpose of compact experimental satellites the observational activities are only performed in the certain sky region by the ground station. But the laser retro-reflector needs tens of square centimeters of the effective reflection area, and the weight and size are limited. For that the reasonable design of the normal pointing of the cube corners within the retro-reflectors array should be implemented in order to achieve the requirements of large reflection area. The calculation model of the effective reflection area for laser retro-reflector with different normal pointing cube corner was derived and taking laser retro-reflector array designed for one of the regional observational satellites as an example, the simulated calculation and the laboratory test of the effective reflection were given. The results show that the simulations of the effective reflection area of laser retro-reflector for satellite regional observation accord with the testing results. The practicability of the design of laser retro-reflectors for satellite regional observation lays the foundation of its further applications in the future.
2016, 45(2): 229006.
doi: 10.3788/IRLA201645.0229006
The phase unwrapping methods are widely used in the field of optical testing, which can be divided into the path dependant type and the path independent type. Generally, the former is faster but more sensitive to the noises, while the latter is more robust but suffers from the problems of slow iterative speed and high time consuming. To solve this problem, a new path independent phase unwrapping method was proposed, which was based on the zonal reconstruction technique. Using this method the wrapped phase in the rectangle pupil can be unwrapped directly without any iteration, and the sample-recombining acceleration strategy was designed to reduce the calculation time greatly which made the algorithm faster than other path independent methods. In addition, to unwrap the phase in the irregular pupil the Gerchberg type iteration was used which can converge in a few steps. The precision of the direct unwrapping for the regular pupil was validated by the simulations, as well as the effect of the acceleration strategy. Besides, the ability to process irregular pupil problem was demonstrated by unwrapping the phase obtained in the experiment.
