2018 Vol. 47, No. 11
column
- Invited paper
- Laser technology and application
- Laser technology
- Infrared technology and application
- Photoelectric measurement
- Atmospheric optics
- Space optics
- Optical manufacturing and craftwork
- Advanced optical materials
- Advanced optical material
- Optical communication and optical sensing
- Photoelectric navigation and control
- Information acquisition and identification
2018, 47(11): 1102001.
doi: 10.3788/IRLA201847.1102001
Infrared polarization imaging has potential advantages in anti-jamming target detection and man-made object recognition in complex environment, and can obtain the physical and chemical characteristics of the target surface. The application of division-of-time, division-of-amplitude and division-of-aperture infrared polarization imaging technique is limited to the insufficiency of volume, weight and power consumption. Miniaturization, integration and real-time imaging equipment are the premise of the widespread application of infrared polarization imaging. Intelligent analysis of the acquired data is the basis of its application. In this paper, a new developed infrared polarization intelligent sensing system was introduced, which collected the infrared polarization data of the target scene in real-time by using the division-of-focal-plane imaging technology. By combining the deep learning with the division-of-focal-plane polarization imaging closely, the high quality polarization image restoration and the intelligent sensing of moving target in typical scenes were realized.
2018, 47(11): 1102002.
doi: 10.3788/IRLA201847.1102002
Horizontal torsion balance impulse device is an effective approach to study the impulse couple produced by laser and working materials ablation. The measuring process was susceptible to the noise so that the analytical method for the way how the noise impacted on the system parameters calibration error and the impulse measuring error was put forward. The method was using the Monte Carlo number simulation method according to the relationship between the system parameters calibration error and the signal-to-noise ratio and the relationship between the impulse measuring error and the signal-to-noise ratio based on impulse instantaneous effect. This method can be used to analyze the influence characteristics how the noise impacts on the system parameters calibration error and the impulse measuring error so as to provide practical suggestions for the error analysis and the structure design.
2018, 47(11): 1106001.
doi: 10.3788/IRLA201847.1106001
Based on the distance weight function of laser pulse, the velocity estimation method of turbulent wind field was studied, which can solve the problem of fining wind speed measurement with Doppler information to detection clear air turbulence. The spatial averaging of the velocity values was taken as a unit of the distance gate. The localized estimations of the wind speed were obtained by convolving the distance unit velocity and the laser pulse distance weight function. Considering the transmission characteristics of the Gaussian laser pulse in the turbulent wind field, which included the effective spatial broadening of the laser pulse to realize the measurement of the turbulence velocity and the application of the lidar in the detection of turbulence. According to the direct speed estimation method and the fast linear average approximation method, the transmission characteristic of the laser pulse was introduced to express the statistical mean value of the radial wind speed of the turbulence. The results show that in the wind field with obvious turbulence conditions, while the high precision pulse distance weighting method has a relatively small velocity standard deviation under the premise of preserving the real wind field attribute. It shows good performance in wind speed correction, improves the measuring performance of lidar on turbulent wind field.
2018, 47(11): 1106002.
doi: 10.3788/IRLA201847.1106002
The precision of line of sight reproduction is a key factor of precision evaluation in Hardware-in-The-Loop(HWIL) simulation system for laser guided weapon. Base on the analysis on static and dynamic errors of line of sight in total, the movetion model with definite physics signification was set up by adopting multi-body system theories. After that, the model was verified by using the measure data of angle of sight in various motion including sine, exponent and typical scenario. The verification shows that the simulation results meet well with the measurement results as the error is less than 2.68' and average error is less than 0.3', and the model can describe the variation rules of angle of sight.
2018, 47(11): 1106003.
doi: 10.3788/IRLA201847.1106003
The microstructure of laser deposited TA15 titanium alloy was investigated and high cycle fatigue property including crack initiation and crack propagation at room temperature was analyzed. The fatigue fracture surface and microstructure of longitudinal section were examined by optical microscopy (OM) and scanning electron microscopy(SEM). The results indicate that as-deposited macrostructure consists of directional column grains with extremely fine basket-weave microstructure. After double-annealing treatment, coarse lamellar-like basket-weave microstructure was obtained. The crack initiation region was characterized by crystallographic cleavage facets of lamellar. The crack tended to propagate tortuously, which was related to different orientations of lamellar. Its propagation direction in certain areas was parallel or approximately perpendicular to lamellar and the secondary cracks in the crack propagation region helped consuming energy and improved the fatigue life.
2018, 47(11): 1106004.
doi: 10.3788/IRLA201847.1106004
At present, there are two models applied in the study at home and abroad in an attenuation model of rain transmisson, which are scattering model and shading effect model. However, the shading effect model has a theoretical defect in dealing with large-sized raindrops located near the laser field of view, and the scattering model requires an enormous amount of computation caused by the multi-scattering problem at the far end of the field of view. This paper presented an improved algorithm for the raindrop attenuation model which was based on projected area of raindrops at receiver. The algorithm corrected the case when a single raindrop was obscured within the viewing angle of the receiving lens. The model was simulated by MATLAB, and the attenuation correlation curves of the improved attenuation model, the scattering model and the shading effect model were obtained. Finally, the accuracy of the improved algorithm was verified by the natural rain field experiment. The results show that compared with the shading effect model, the accuracy of improved model is improved by 54.6% when the transmission distance is 100 m and the rainfall rate is 1.2 mm/h. It is shown that the improved algorithm can improve the accuracy of the raindrop attenuation model. The research of the project provides a theoretical support for the development of the blue green laser atmospheric communication detection technology.
2018, 47(11): 1106005.
doi: 10.3788/IRLA201847.1106005
Aiming at laser heating the specimen locally to detect cracks, and the signal-to-noise ratios fell when surface cracks in material with low thermal conductivity were imaged, a detection algorithm of surface microcrack which compared the adjacent thermal signals in cylinder ferrite components was proposed. The thermal signal at each position on moving cylinder was reconstructed based on geometric model, then the Euclidean distance along the laser scanning direction was used as a feature to image. The relative algorithm parameters about cutting area of thermal signal and the position of reference signal were confirmed by simulation analysis. The specimen were test, which had 5-35 m wide crack on 6 cylinder ferrite surface. The results show that this approach can enhance the signal-to-noise ratio by 1 to 2 times compared with conventional approach at the line-laser scanning speed of 2.66 mm/s, and it can image the shape of cracks evidently.
2018, 47(11): 1106006.
doi: 10.3788/IRLA201847.1106006
The VAD (Velocity-Azimuth Display) method, which is used to retrieve wind field based on one wind lidar system and the assumption of uniform wind in the same level, has been widely used in the industry. To guarantee the accuracy, the azimuthal range of lidar and number of scanning should meet some requirements, which affects measurement efficiency. Based on this, a new wind retrieval method of VAD used for Doppler lidar based on gradient descent algorithm was developed. The gradient descent algorithm was used to replace present Fourier series expansion for the solution of VAD. The convergence and calculation speed were improved by analyzing the factors that affect algorithm convergence and determining the iteration step length and the number of iterations, respectively. In order to demonstrate this modified VAD method, the wind data of coherent Doppler lidar was compared with standard wind cup anemometer (IEC 61400-12-1). The correlation coefficients of the 10 min-averaged wind speed and direction were up to 0.99 in the case that the azimuth range and the number of radial velocity were 60 and 7, with wind speed standard deviation and bias of 0.52 m/s and 0.02 m/s, and with wind direction standard deviation and bias of 5.1 and 3.6. The results prove that this modified VAD method could improve Doppler measurement efficiency and applicability, and guarantee its accuracy at the same time, which improves the system capability for the monitoring of dynamic complex wind field.
2018, 47(11): 1106007.
doi: 10.3788/IRLA201847.1106007
In order to realize the effective evaluation of the effect of laser angle deception, the laser angle deception interference effect evaluation system was constructed, and the structure and function of the target motion simulation subsystem, the laser guided missile simulation sub-system and the interference effect evaluation subsystem were introduced in detail. Combined with the interference effect evaluation method, the relevant experiment was designed. Through the detailed analysis of the experimental data, the interference effect was evaluated. In the experiment, when the laser pulse period was 50 000 microseconds, the interference laser was set up 2, 3, 4, and -3 microseconds ahead of guidance laser, and the solutions of point deviations were 154.14, 167.03, 174.93, and 0.52 meters respectively; When the laser pulse period was 51 200 microseconds, the interference laser was set up 2, -2, and 3 microseconds ahead of guidance laser, and the solutions of point deviations were 396.86, 0.53, and 396.86 meters respectively. The results show that the interference of the pilot emitter can be achieved when the interference pulse leading pulse enters the seeker gate simulator. Through this experiment, it was found that the seeker simulator tracks the interference of laser spot itself in laser angle deception interference, rather than the interference laser and indicating the laser energy center. The deviation of the placement point for the assessment of indicators, the interference effect were evaluated and analyzed, and the results can provide technical support for laser guidance and confrontation evaluation.
2018, 47(11): 1106008.
doi: 10.3788/IRLA201847.1106008
In order to reduce the thermal deformation of the light guide mirror, the finite volume method was employed to solve the three-dimensional turbulent heat transfer equation and the temperature field of the laser irradiated region was obtained. In this thesis, the effects of laser power, irradiation time, coolant velocity, mirror materials, the distance between channel and mirror on the temperature field were discussed. The average temperature and the standard deviation of temperature of irradiation zone were regarded as the main indexes to evaluate the cooling effect. It is found that the greater the laser power is, the greater the temperature in various directions is. The temperature rise is faster in the initial stage of laser irradiation and it tends to be gradual in the latter. The larger the coolant velocity is, the lower the average temperature and the standard deviation of temperature are. Different properties of the mirror materials also have influence on the heat transfer effect, but the distance between channel and mirror has little effect on the temperature field of the copper mirror.
2018, 47(11): 1106009.
doi: 10.3788/IRLA201847.1106009
During laser deposition manufacturing process, the forming width of the single track is mainly controlled by the melt pool width. However, high geometric accuracy is premised on the stable size of the melt pool. In order to establish an empirical model described relationship between the melt pool width and main process parameters (laser power, scanning speed, and powder feeding rate), turn off laser control in uneven speed stage was used and Kalman filtering was applied to denoise the measured data of the melt pool width. An empirical model between the process parameters of laser deposition and the width of molten pool was established based on orthogonal experimental design with a goodness-of-fit of 94%, and the maximum error was less than 4.5%. The results of single variable experiments conducted to the model show that the melt pool width has a positive correlation to the laser power and a negative to the scanning speed. The experimental results were in good agreement with the regression analysis.
2018, 47(11): 1106010.
doi: 10.3788/IRLA201847.1106010
Three dimensional optical storage based on femtosecond laser is one of the most important methods to realize high density and super-high density optical storage. The absorption spectrum of a new micro explosion material(Sm0.5Ce0.5(DBM)3 Phen dye doped with PMMA as substrate) was measured and analyzed, the fluorescence spectra before and after excitation were obtained by using 514.5 nm laser as laser source, the characteristics of electron rotation resonance spectra before and after excitation were obtained by using 800 nm femtosecond laser as excitation source, the change of storage point size and storage point readout gray value under different femtosecond laser pulse energy was analyzed, the four layer optical information storage of femtosecond laser was realized, the distance between the points is 4 m and the distance between layers is 16 m. The experimental results show that this material can be well applied to 3D optical information storage.
2018, 47(11): 1106011.
doi: 10.3788/IRLA201847.1106011
The numerical analysis was conducted on the temperature and stress fields of single crystal silicon irradiated by the combined laser by the finite element method. The damage effect of the single crystal silicon which was respectively irradiated by the combined laser and continuous laser was compared, which was under the condition that the average power density of combined laser was equal to the continuous laser. The results show that combined laser is more conducive to realize thermal damage of single crystal silicon than continuous laser. The Von Mises stress, axial stress and hoop stress in single crystal silicon is higher when the model is irradiated by the combined laser than when it is under continuous lasers. The combined laser damage in monocrystalline silicon is stronger than continuous laser.
2018, 47(11): 1105001.
doi: 10.3788/IRLA201847.1105001
High power single frequency fiber lasers are extensively applied in coherent detection and power spectrum beam combination etc. The suppressing method of stimulated Brillouin scattering was analyzed. The influences of amplification level on stimulated Brillouin scattering were studied. A single frequency fiber laser with linewidth of 70 kHz was used as seed source. And through two stage amplified, the central wavelength of 1 064.1 nm, linewidth of 70 kHz and power of 180 W were achieved respectively. The optical-optical efficiency is 71.1%. And the beam quality is Mx2=1.2 and My2=1.21. The output power before and after changing amplifier characteristic was compared. And the reason that output power increased was analyzed. The stimulated Brillouin scattering gain coefficient was reduced by varying amplifier temperature distribution. Then stimulated Brillouin scattering threshold was promoted. Finally, this makes the output laser power increase greatly after varying amplifier temperature distribution. The output power of this laser is only limited by pump power. If the pump power is increased, the higher power of single frequency all fiber laser will be achieved.
2018, 47(11): 1105002.
doi: 10.3788/IRLA201847.1105002
With the rapidly increasing applications of high power laser diode(HPLD) in extreme environments, the reliability of bonding interface has become one of the critical bottlenecks affecting the HPLD's performance and lifetime. In this work, failure behavior and lifetime of a single-bar CS-packaged HPLD under -55-125℃ thermal-shock were analyzed by finite element method(FEM). Based on Anand constitutive model and Darveaux energy accumulation theory, the reliability of indium bonding layer on the edge and at the central position after the themal-shock was compared. It shows that the bonding interface on the edge has the highest stress (0.042 5 GPa) and lowest lifetime (3 006 cycles), in other words, the edge is the riskiest element of the bonding interface. In addition, the lifetimes of three kinds of bonding layers on the edge, including indium, 80Au20Sn and nanosilver paste, were simulated to be 3 006, 4 804 and 4 911 cycles, respectively. The results show nanosilver paste and 80Au20Sn have longer lifetimes and better reliability, which are better bonding materials in the packaging of high power laser diodes used in extreme enviroments.
2018, 47(11): 1105003.
doi: 10.3788/IRLA201847.1105003
The double wavelenghs short pulse laser was developed with the high mode volume and variable reflectivity mirror(VRM). The thermal lens and the thermal birefringence produced by diode-lasers pumped rod laser medium was compensated, which presented a short-pulse energy of 140 mJ and 1 064 nm laser output with a pulse width of 17.76 ns at a repetition rate of 500 Hz. The beam quality value was M21.6, and the energy instability(RMS) value of 20 minutes was less than 0.3%. The result of resonator was corresponded with Master Oscillator Power-Amplifier(MOPA) technology, but it was close and neat. The maximum laser energy of 96 mJ at 532 nm was demonstrated by extra-cavity second-harmonic generation(SHG) with type-Ⅱ angle phase-matched GTR-KTP crystal, the KTP crystals with resistance to grey trace effect was grown by hydrothermal method. The maximum efficiency of SHG was 68.6%, and the beam quality value was M22.1. The 1 064 nm and 532 nm laser were output at same axis with energy regulation.
2018, 47(11): 1105004.
doi: 10.3788/IRLA201847.1105004
Influences of the bias states of saturable absorbers on bistable InGaAsP multi-quantum-well(MQW) common cavity tandem section(CCTS) semiconductor lasers were investigated experimentally and theoretically. The experiment demonstrated that the bistability characteristic of P-I curves can be more significant with increasing reversed bias voltage in the saturable absorber(SA), and a negative differential resistance phenomenon was found in V-I curves. When the voltage was -3 V, the hysteresis width was broadened to 13.5 mA, with the on-off ratio up to 21:1. The theoretical analysis proves that higher passive voltage in SA and shorter carrier escape time can result in better bistability. The maximum on-off ratio as high as 107:1 promises that a common cavity two-section laser can be switching between the two-steady state.
2018, 47(11): 1105005.
doi: 10.3788/IRLA201847.1105005
The theoretical analysis and experimental study of the instability phenomenon of a Nd:YAG Q-switched short pulse laser was demonstrated. During the operation of the short pulse laser, there were many factors that can cause the instability phenomenon. During the experiment it was found that the interference pulse which can enter into the cavity though the output mirror can cause the instability of the short pulse laser. Based on the basis of thory, the influence of external interference light on the output light characteristics of short pulse Q-switched laser was simulated and verified by experiments.The characteristics of energy and pulse width were discussed respectively. The results show that the greater the energy of interference pulse is, the more serious the instability phenomenon is. When the interference pulse energy is 60 mJ, the loss of output energy of the short pulse laser can be more than 15%. The pulse width is 1.15 times of the original, the instability phenomenon is also more serious at the pump end of the short pulse Q-switched later. When the input energy is 60 mJ the pulse width is 10 ns, the loss of output energy of the short pulse Q-switched laser reaches 80% of the original.
2018, 47(11): 1105006.
doi: 10.3788/IRLA201847.1105006
Influence factors of compactness of DF laser with cooling gas ejector were analyzed. Ratio of Laser Power to Gas Source Volume(RPGV) was chosen as DF laser compactness evaluation index and was calculated at different conditions. According to the result, RPGV increases at first, and then decreases with increasing nozzle array mass flux. RPGV gets maximum value when nozzle array mass flux is about 3.3 gs-1cm-2. In the case of same laser effluent parameters, increasing ejector driving gas total pressure leads to a bigger RPGV, but its effect on RPGV gradually becomes weak. Compared with helium as ejector driving gas, adopting nitrogen and air as ejector driving gas leads to higher RPGV.
2018, 47(11): 1105007.
doi: 10.3788/IRLA201847.1105007
Crystalline Raman amplifier is an important way to obtain high beam quality, high spectral purity and high power Raman laser. The normalized transport equations of the external cavity Raman amplifier were derived by inducing four normalized composite parameters. A set of universal theoretical curves describing the operation of Raman amplifiers were obtained by numerical solving the transport equations, and the influence of the complex normalized variables on the performance of the Raman amplifiers was analyzed. The dependences of the magnification of the Raman pulse peak intensity, pulse shape of the output Raman laser, and the conversion efficiency from pumping laser to output Raman laser on the pumping pulse intensity, the relative width of the pumping pulse and Raman seed pulse, and the time overlap of the pumping pulse and Raman seed pulse were studied in detail. The optimum working condition of crystalline Raman amplifier was explored. The normalized theory was verified with actual experimental data. It is indicated that the theoretical results are consistent with the measured data. The normalized rate-equation model is proved to be precise and feasible.
2018, 47(11): 1105008.
doi: 10.3788/IRLA201847.1105008
A compact, intra-cavity widely tunable continuous-wave singly resonant optical parametric oscillator (SR-OPO) was reported based on a MgO-doped periodically poled lithium niobate (MgO:PPLN). A diode-pumped Nd:YVO4 laser at 1 064 nm was employed as the pump source of this SR-OPO with a compact linear cavity. The MgO:PPLN crystal used contained seven different periodically poled gratings from 28.5 to 31.5 m with a step of 0.5 m between the neighbor periods. The output wavelengthes at the different grating periods of MgO:PPLN crystal was measured, which was well matched with the theoretical value. The widely tunable SR-OPO output signal wavelength range from 1.43 to 1.67 m and idler wavelength range from 2.93 to 4.16 m were achieved. The output power as the function of grating periods and pump power was investigated. Under an incident pump power of 14.5 W, a maximum signal output power of 2.94 W at 1 595 mm and an idler output power of 1.45 W at 3 190 nm were obtained with the temperature controlled at 35℃ and the period set at 31 m. The diode to OPO total output conversion efficiency reached 28.5%.
2018, 47(11): 1105009.
doi: 10.3788/IRLA201847.1105009
Heat seeking weapons such as man-portable air defense system (MANPADs), various IR guiding missile are the main threaten for civil aircraft and military aircraft. As the appearance of IR imaging seeker, the effect of traditional IR interference equipment and infrared flares are limited. Otherwise, direct IR countermeasure (DIRCM) system has been effective means. In this paper, the international research on DIRCM and key techniques for laser of DIRCM was reviewed. Furthermore, calculating method for dazzling area of imaging detector was given. At the same time, the research trends of DIRCM and laser of DIRCM were forecasted in the future.
2018, 47(11): 1104001.
doi: 10.3788/IRLA201847.1104001
Detection distances of the hypersonic aircraft based on a point source infrared detectability were predicted under the ground-based and space-based observation platforms. Two-temperature N-S equations were solved and the fluid-solid conjugation heat transfer technique were used for calculations of the surface temperature. Absorption coefficients of species were evaluated by the line-by-line method, and the radiative transfer equation was solved with the line-of-sight method to obtain intrinsic radiation characteristics of the HTV-2 type vehicle. The detectability of the two platforms was calculated considering the atmospheric transmittance, background and path radiation parameters. Results show that the radiation intensity of the target is determined by surface emissions comparing with the gas radiation. The intensity integrated within the 3-5 m band is high nearly an order of magnitude than that within the 8-12 m band. Under the condition of a constant sensitivity, the maximum detection range is strongly dependent on the spectral regions and observation angles. The maximum detection distances under ground-based and space-based stations are 450 km and 1 450 km for the 3-5 m band, and 300 km and 550 km for the 8-12 m band, respectively.
2018, 47(11): 1104002.
doi: 10.3788/IRLA201847.1104002
The black porcelain far-infrared radiation plate, which is made of vanadium slag, has a wide range of sintering temperature, extrusive coloring role and excellent ceramic performance. The content of transition metal oxide in the fouth cycle is more than 80%. The radiation rate was up to 0.95, and after 2 000 hours of 650℃ accelerated aging test, the radiation rate does not change, and the surface layer does not fall off. By SEM analysis on fracture morphology and microstructure, the blank plate was composed of ilmenite, board-ilmenite and anemousite, and the particles were mechanically mixed, and black porcelain plate was composed of grain, vitreous body and pore, and most metal oxide in raw material were enriched in the grain, and the formation of cordierite and spodumene, zircon and other minerals were surrounded by vitreous body, which has excellent chemical stability. Non-toxic, harmless, non-radioactive, was a kind of far-infrared radiant of low cost, long life, high efficiency.
2018, 47(11): 1104003.
doi: 10.3788/IRLA201847.1104003
According to the requirement of the butting short and middle waves long linear IRFPA detectors integrating and coupling with the inline pulse tube cryocooler, the difficulties of the Dewar package were discussed. By studying the temperature uniformity and the supporting structure of long butting substrate, the cold loss and the vacuum life of the large-size Dewar, the three-dimensional thermal output method of the multi-point S type thermlink combined with the conductive layer was proposed, and the supporting structure of bridge with the dual substrate was designed, which were to solve the key technologies of higher temperature uniformity of the long butting substrate, the lower thermal stress of the integrated detector and depth of focus control, space environmental adaptability, lower cold loss and longer vacuum life, the Dewar assembly for the dual-band long linear FPA had been successfully developed, and tested by serial space environment adaptability tests, the results show that those main performances do not change obviously. The Dewar assembly satisfys the requirements of the space application.
2018, 47(11): 1104004.
doi: 10.3788/IRLA201847.1104004
Satellite remote sensing is an important means to study the infrared radiation characteristics of the earth's atmosphere background. Due to the influence of atmosphere and the limitation of sensor observation conditions, it is impossible to obtain multi-meteorological and multi-detection radiation data. Aiming at this problem, the spectral radiation characteristics of vegetation, water and rock were analyzed based on JHU spectral database. Based on the spectral response of sensors, a model of surface radiation band transformation model based on spectral correlation was established for 3-5 m. The error was calculated by the stepwise regression method, and the model error was less than 10%. Using MODIS, AIRS and other multi-source remote sensing products, and according to the surface-atmosphere-sensor radiation transfer model, the mid-infrared image of the earth background radiation was simulated. It can simulate the mid-infrared image of the earth background radiation with different temporal and spatial resolution and detection conditions. The results show that the simulation of mid-infrared image with multi-source remote sensing data can achieve large-scale and fine texture image simulation which can be used in remote sensing research.
2018, 47(11): 1104005.
doi: 10.3788/IRLA201847.1104005
Pulsed thermographic image has the disadvantages of low-contrast, fuzzy-edge, and non-uniformity of illumination for the defect detection, thus, a defect determination method which combines digital detail enhancement (DDE) technology with maximum entropy multi-threshold segmentation method was proposed for the improvement of pulsed thermographic image. Firstly, the contrast between defects and the background was improved significantly after the image was processed with digital detail enhancement algorithm optimized with adaptive contrast enhancement (ACE) algorithm, and reducing the influence of illuminative non-uniformity on defect recognition. Secondly, the target defects with maximum entropy multi-threshold segmentation method optimized with genetic algorithm, and the contours of each defect with eight neighborhood method to get the contour pixels in a certain sequence. Finally, based on the sequential contour pixels, the perimeter and the area of each defect could be estimated respectively with Euclidean distances formula and Green's theorem. The experimental result shows that this method is feasible to estimate defect size quantitatively, and digital detail enhancement technology could improve the defect detectability of pulsed thermographic system in a certain extent.
2018, 47(11): 1117001.
doi: 10.3788/IRLA201847.1117001
In microassembly, zoom vision system was usually used to solve the contradiction between measuring scope and accuracy. However, new problems of dynamic calibration and real-time automatic focusing were also introduced as a side-effect. For this reason, the calibration and automatic focusing technology of zoom micro-vision system were described. For calibration, the principal point of image was determined by method of convertible magnification. Based on planar target, the linear calibration under fixed magnification was firstly performed by homography matrix decomposition of single view. Then the distortion model and the quantum-behaved particle swarm optimization (QPSO) were employed sequentially to do nonlinear optimization for the linear calibration result. After nonlinear optimization, the maximum re-projection error was 0.13 pixel and the average re-projection error was about 0.1 pixel. Furthermore, the calibration for magnification at arbitrary working condition was completed by Gaussian curve fitting. For real-time automatic focusing, method of maximum gradient threshold of eight-neighborhood and gradient threshold were used, for the traditional gray gradient function only considered the fixed gradient direction and was susceptible to noise. Compared with other several gray gradient focusing function, this method had good unimodality and noise immunity.
2018, 47(11): 1117002.
doi: 10.3788/IRLA201847.1117002
For the purpose of realizing the all-fiber gas detection system with high sensor sensitivity, using the Hollow Core-Photonic Crystal Fiber (HC-PCF) as gas cell, a dual-optical path differential near-infrared carbon dioxide detection experimental system based on virtual instruments LabVIEW and the absorption spectroscopy around wavelength 1 572.48 nm of carbon dioxide molecule was developed. The system response time was about 100 s by inflating the HC-PCF of 1.8 m long from two ends under the pressure of 0.1 MPa. The detection system was calibrated with carbon dioxide of standard concentration. Carbon dioxide with known concentration of 2%, 5%, 10% and 100% were tested respectively and the experimental results showed that the detection errors relative to standard concentration were no more than 2% and the maximum standard deviation of measured concentration were 3.32% in 100 minutes. In addition, the optical path of gas absorption reaches 1.8 m and the system detection sensitivity of 5.981 810-5 W/ppm was achieved.
2018, 47(11): 1117003.
doi: 10.3788/IRLA201847.1117003
The distortion of the space remote sensing camera was an important parameter, the test accuracy of which was directly related to the image processing precision after getting the image. For the space non-mapping remote sensing camera, the requirement for the distortion of the optical system was not as high as mapping remote sensing camera at the beginning of the design. So its distortion of the optical system was large in general. For this kind of remote sensing camera, especially those with large FOV, it's necessary to test distortion of the camera accurately. This can provide more accurate initial condition for the calibration in-orbit. Based on the precision of angle measuring method, the mathematical model of space remote sensing camera in view of the large distortion was established in this paper, and a reasonable and feasible test idea was proposed for the large FOV and arc distortion of the camera. The high accuracy test to the distortion of the under test camera was completed, and the results were ideal. The practical test results show that the accurate of distortion is better than 1.8 m(1). The test accuracy can meet the high requirements of test precision for under test camera. So this method has reference significance to the distortion test of the space non-mapping remote sensing camera.
2018, 47(11): 1117004.
doi: 10.3788/IRLA201847.1117004
In order to realize the high precision 3D reconstruction for deep-hole inner surface geometry, a 3D measurement system was built based on the structured light. First, the constitution and relevant measurement principle of the system were introduced, the assertion was proved that the distance between the image and the actual was approximately linear in a given range. The assertion lays a solid theoretical foundation for the following measurement. Then, the deep-hole model object and the model in which the corresponding inner surface was unfolded into a plane which were measured using the structured light. The measurement proves the feasibility of the measurement scheme and the actual effect of the measurement system. The measurement results show that the measurement scheme is feasible in theory, the measurement accuracy of the system can reach sub-pixel in practical applications and the absolute deviation is controlled within 0.034 7 mm range. Finally, in the actual measurement of the inner surface of the deep-hole parts inner surface, the high precision 3D reconstruction for deep-hole inner surface geometry was realized.
2018, 47(11): 1117005.
doi: 10.3788/IRLA201847.1117005
As the output end of the high power fiber laser resonator, the reflectivity value of the output coupler(OC) was small. When the OC reflectivity was measured by the transmission spectrum method, the instability of the light source power or the error form measured spectrometer can cause a large error in the result of OC's reflectivity. Based on Fresnel reflection principle, a method of measuring OC reflectivity by reflectance spectrum was proposed. Validating the method by experiments, the results show that the measurement accuracy and stability of the method have been improved remarkably. At the same time, the inaccuracy of bandwidth measurement caused by this method was analyzed, and a method of using index matching liquid was proposed to solve the problem.
2018, 47(11): 1117006.
doi: 10.3788/IRLA201847.1117006
A Michelson interferometer was constructed to measure the spectra generated by a terahertz (THz) gas laser pumped by a CO2 laser. The hyperfine spectra at 2.52 THz and 3.11 THz generated in CH3OH gas pumped by the 9P36 and 9R10 laser lines of the CO2 laser was measured with the frequency resolution of around 1 GHz. The measurement results showed that the THz laser was monochromatic and had very narrow linewidth. The measured wavelength was consistent with the nominal value. Velocity measurement of target on the translation mirror was also performed based on this interferometer. Two methods for acquiring velocity were proposed, demonstrating good accordance with the set values for both fixed and variable velocities. It is concluded that the Michelson interferometer could be used to accurately measure the spectrum of a THz source, and the velocity measurement was also possible with the help of a monochromatic THz source, laying the basis for THz applications like spectroscopy, imaging, etc.
2018, 47(11): 1117007.
doi: 10.3788/IRLA201847.1117007
The footprints of a satellite laser altimeter have an elevation accuracy of the decimeter order, which satisfies the elevation accuracy needs of ground control points (GCP) for mapping. However, the horizontal accuracy of footprints is only few tens of meters, and only the footprints illuminating on flat ground targets can be used as GCPs. In this paper, the waveform model was derived and used to develop a waveform simulator of laser altimeters. Compared with the current method of waveform matching, the new simulator considered more detailed effects arising from the device and target, e.g., time and spatial distribution of lasers, surface profile, and surface reflectivity. The airborne LiDAR point cloud and the Geoscience Laser Altimeter System(GLAS) data were involved to match the best-fit waveform by maximizing the correlation coefficients of the simulated waveform and GLAS waveform, and the precise location of every GLAS footprint could be acquired where the correlation coefficient was the maximum. The results show that, the mean of maximum correlation coefficients is more than 0.9 during the GLAS operating periods with normal received energies, and the horizontal accuracy of footprints is approximately 2 m after the waveform matching. The proposed method can be used to extract the laser GCPs on complex relief of the surface.
2018, 47(11): 1117008.
doi: 10.3788/IRLA201847.1117008
A small volume, light weight, portable laser Doppler nanometer displacement telemetry system was presented that meet the demand of nanometer detection for the ultra-stable platform in the aerospace industry. In the electrical module, the system adopted the demodulation scheme based on digital zero intermediate frequency, thus the decrease of the analog devices was helpful to improve the detection resolution and precision of the system. Digital zero intermediate frequency demodulation method for the nanoscale vibration amplitude was analyzed theoretically and implemented. The proof experiment shows that the minimum phase of 1, equal to vibration amplitude 2.15 nm detectable capacity is achieved. PI-E501 standard vibration source, placed at 10 meter distance from the system, was employed to testify the performance of the laser Doppler nanometer displacement telemetry system and telemetry with amplitudes of 1000, 200, 10 nm at the frequency 10 Hz and 1000 Hz was achieved. This system performance verification experiment shows that the laser Doppler nanometer displacement telemetry system achieve the ability of dozens of herts to hundred herts frequency, microns or even smaller vibration amplitude detection for the ultra-stable platform in the aerospace industry.
2018, 47(11): 1117009.
doi: 10.3788/IRLA201847.1117009
A new type of flexible hinges was proposed, which were double sided circular-parabolic hinges. The theoretical structure model of the hinges was established. The Castigliano's second theorem and calculus theory were used to calculate the main performance indexes that were compliance and rotational accuracy of the hinges. The theoretical calculation and finite element analysis of the compliance and rotational accuracy were carried out. At the same time, the structural parameters that affected the hinges' performance were studied. The results show that the theoretical values of compliance and rotational accuracy were better than those of the finite element analysis, and the consistency was greater than 92%. And the minimum cutting thickness t had the greatest influence on the change of hinges' compliance. As a new type of hinge, compared with other flexible hinges, the circular-parabolic hinges combined the advantages of straight circular hinges and parabolic hinges. At that time, the hinges had stronger rotation performance and weaker load sensitivity, and the thermal adaptability was stronger. The design of the circular-parabolic hinges provids guidance for the design of the support structure including using in the space environment.
2018, 47(11): 1117010.
doi: 10.3788/IRLA201847.1117010
The selection of sparse regularization functions directly affects the effect of sparse non-negative matrix factorization of hyperspectral unmixing. At present, the L0 or L1 norms are mainly used as sparse measures. L0 has good sparsity, but it is difficult to solve; L1 is easy to solve, but the sparsity is poor. An approximate sparse model was presented, and was applied to the multi-layer NMF (AL0-MLNMF) in hyperspectral unmixing. The algorithm made the observation matrix multilevel sparse decomposition improve the precision of hyperspectral unmixing, and improve the convergence of the algorithm. The simulation data and real data show that the algorithm can avoid falling into the local extremum and improve the NMF hyperspectral unmixing performance. Algorithm accuracy has greater improvement effect than several other algorithm, RMSE reduces 0.001-1.676 7 and SAD reduces 0.002-0.244 3.
2018, 47(11): 1111001.
doi: 10.3788/IRLA201847.1111001
Polarized imaging in horizontal direction is an effective method to observe targets at ground.Due to the scattering and absorbing effects of aerosol and molecule in the atmospheric transfer path, the target polarized information composies other polarized information, which would limit the characteristics extraction of targets. It is very important to study the effects of atmospheric polarization. For the problem of polarized observation in horizontal near ground, the atmospheric transfer properties under different aerosol optical depth were simulated based on the single scattering hypothesis. And the experiment on atmospheric polarized properties transfer was performed outdoor. The result of simulation indicates that the contribution of surfaces could be ignored;the contribution of atmosphere to total polarized reflectance increases with the increase of the aerosol optical depth. The value of degree of line polarization which was simulated under the same observing conditions with the experiment outdoor at different time, was consistent with the experiment, and the relative error was in the range 0.1.The basic theory of investigation on both polarized radiative transfer and atmospheric correction near ground was proposed.
Atmospheric optical turbulence severely restricts the performance of optical systems. In order to reduce the influence of atmospheric turbulence and meet the application of photoelectric engineering, it is very important to accurately estimate the atmospheric optical turbulence profiles in different scenes. Based on the Tatarski optical turbulence parameterization scheme and the representative outer scale models, the meteorological data measured by the sounding instrument were used to estimate optical turbulence profiles of inland area(Hefei), sea-land interface (Maoming) and open sea, respectively. The estimations were compared with the observed profiles at Hefei and Maoming. There is a good consistency both in trend and magnitude, which provides the evidence for estimating the atmospheric optical turbulence profile of open sea with this model. The results show that the model can precisely estimate the optical turbulence profiles in different environments. In addition, it is found that the occurrence of upper air optical turbulence is closely related to wind shear and temperature gradient.
2018, 47(11): 1111003.
doi: 10.3788/IRLA201847.1111003
A kind of array laser guide star (LGS) based adaptive optics (AO) system was independently proposed in purpose to overcome inherent problems in current wavefront sensing techniques. It can effectively eliminate focus anisoplanatism and improve its own wavefront sensing accuracy, drastically widen the scope of atmospheric turbulence that a LGS AO system can detect, and lower the requirement of an AO system for the brightness of LGSs. Its closed-loop working process was interpreted. Based on this working process, its simulation model was built and its wavefront sensing process was numerically simulated based on array LGS. At last, the accuracy of wavefront reconstruction was estimated and the errors of simulation was analyzed. Simulation results have shown that the accuracy of wavefront reconstruction is favorable and residual correction error is 11%, which invalidates the feasibility of using array LGS for wavefront sensing.
2018, 47(11): 1111004.
doi: 10.3788/IRLA201847.1111004
The change of effective aperture in adaptive optics system may lead to light shortage among some of the Hartmann-shack sensor sub-apertures and functional failure in a number of actuators, making the matching layout between system sub-aperture location and actuator location changes. The correspondence between the control voltage input of actuator and the feedback output of sub-aperture, therefore, changes consequently. In response to the effective layout change of the adaptive optics system, this paper firstly discussed the influence of the change of aperture on adaptive optics system and analyzed the reasons for instability. It then put forward a new method based on 0-1 fault model to model the partial failure situation in the system so as to modify proportional-integral control algorithms. Finally, it proved that through experiments using the 0-1 fault model can guarantee the stable operation of the system, but the failure of some parts of the adaptive optics system will lead to the decrease of the correction ability of the system to the wavefront aberration.
2018, 47(11): 1111005.
doi: 10.3788/IRLA201847.1111005
Image quality assessment is the basic research work in the field of ground-based photoelectric detection, which is closely related to other post-processing tasks. The quality representation and index extraction of no-reference and objective adaptive optics images were focused on, and the basic framework and current research status on image quality evaluation were summarized. An adaptive optics image quality perception model based on non-linear energy normalization was proposed. Based on the characteristics of adaptive optics system and human visual perception, two no-reference and objective quality indices were then extracted, which could be used in the frame selection, recovery and other key tasks to achieve automatic image quality evaluation or automatic detection of image content change, the evaluation results and subjective evaluation of human eyes show a favorable consistency.
2018, 47(11): 1111006.
doi: 10.3788/IRLA201847.1111006
To capture the space-borne remote sensing aerosol data with high signal-to-noise ratio (SNR), according to the chain of the imaging system, the main factors on the SNR of spectrometer were presented. Combined with the imaging system response model and the expression of SNR, a modular design method for high SNR of spectrometer imaging circuit system was proposed for visible detectors and infrared detectors. From the overall design to the module design of Cloud and Aerosol Polarization Imager (CAPI) imaging circuit development plan was described. The radiation calibration experimental results indicate that the minimum SNR of visible channel image under typical radiance conditions is 50.9 dB, the minimum SNR of infrared channel image under typical radiance conditions is 62.3 dB. The design method of visible detectors and infrared detectors provides references for other spectrometer imaging circuit system in remote sensing fields.
2018, 47(11): 1113001.
doi: 10.3788/IRLA201847.1113001
To meet the higher demands of the earth and space observation, the aperture of space telescope mirror has took step to 10 m order of magnitude from 1 m with an ever-increasing trend. As a key technology for the space telescope, the large aperture mirror support is related directly to the surface shape accuracy and stability of the mirror, and crucial to the actual observation ability and even the success of the telescope mission. Three main forms of mirror support were discussed and their applicability were compared. The influential factors on the mirror mount design were summarized and based on this summary some key points and principles for support design were discussed. Combined with analysis on support technique research progress at home and abroad, the key techniques such as optimization on the number and location of support points, athermal design and un-stressed assembly and the trend of development were scrutinized. It is expected to provide reference for large space telescope of our country and thus promote leapfrog development in the new round of space exploration.
2018, 47(11): 1113002.
doi: 10.3788/IRLA201847.1113002
Aiming at the problems that the main structure of a mini-optical device in space is too heavy, the ground gravity deformation is too large and the base frequency is too low, the optimization mathematical model was established with the objective of minimum mass and RMS of the random acceleration response, the fundamental frequency and the deformation as the constraint conditions. The topology optimization design of the main structure of the mini-optical device and the engineering analysis of the optimized main structure were carried out. The results show that the mass of the main structure of mini-optical device is 12.5 kg, which is reduced by 68.71%; The fundamental frequency is increased from 11.18 Hz to 268.7 Hz after optimization; The maximum deformation is 0.3 m. The magnification of the acceleration response of the optical-load installation is 1.2 which is better than system specification 1.5. Mechanics and thermal experiments were carried out to examine the performance of the main structure of mini-optical device. The detection results meet the overall index, which proves the main structure has good performance, the optimization method is effective and feasible.
In order to realize high-precision mass production of small diameter dual aspherical chalcogenide glass lenses, cooling gap in cooling stage was studied to reveal its influence on lens molding quality through simulation and experiments. Firstly, high temperature viscoelastic mechanical, structural relaxation and interface heat transfer model of the chalcogenide glass molding was analyzed and applied to simulation study. Secondly, molding simulation of target lens was carried out, and influence of cooling gap conditions on internal temperature, stress distribution, and profile deviation of the lenses were discussed. Finally, the molding experiments corresponding to simulation were conducted. The influence of cooling gap conditions on the surface form accuracy PV, surface roughness Ra and profile deviation of the molded lenses were analyzed, and simulation and experimental results were also compared to verify the validity of simulation model and its results. Simulation results show that the stress was the smallest when cooling gap is 0.1 mm, which is 3.897 MPa. The profile deviations of molded lens ASP1 and ASP2 were 1.054 m and 0.858 m, respectively. The experimental results show that surface quality of molded lens with cooling gap of 0.1 mm was the best. The PV values of ASP1 and ASP2 are 170.8 nm and 223.6 nm respectively, Ra values are 22.7 nm and 24.9 nm respectively, and maximum profile deviations are 0.896 m and 0.738 m respectively. Therefore, minimum cooling gap is 0.1 mm. The simulation results showed good agreement with experimental results. The cooling gap has some influence on molding quality of small diameter dual aspherical chalcogenide glass lenses. The determination of minimum cooling gap can effectively improve surface quality of molded lenses.
2018, 47(11): 1142002.
doi: 10.3788/IRLA201847.1142002
To realize the engineering application of the high frequency and high precision tiling error compensation, a novel method for error compensation of large-aperture tiled-grating compressor was presented by using a small-aperture mirror. The relationship between the amount of mirror compensation and the tiling error was analyzed for two-pass Z-type compressor. The influence of the compensated tiling error on the focus energy was quantitatively compared with the numerical simulations, which was combined with the ray-tracing method and principle of Fraunhofer far field diffraction. The validity was verified and the error tolerances for direct drive and mirror compensation were obtained. The results show that this method can decrease the precision demand significantly for tiled-grating.
2018, 47(11): 1121001.
doi: 10.3788/IRLA201847.1121001
Chemical vapor deposition method was used to manufacture bulk ZnS materials (CVD-ZnS). Nodular growth phenomenon in bulk CVD-ZnS was studied systematically. Through the analysis of microstructure and macrostructure, some growth centers with larger size were seen as the origin of nodular cells. Growth direction of nodular cells was changed to cross direction, while growth rate of nodular cells was faster than other normal grains. All of these factors led to the spherical objects on the surface of products. A turbinate structure was observed from nodular cell in cut-plane samples as well. Meanwhile, according to the different nodular phenomena, the main mechanisms of different growth centers were discussed. The counteracting methods, based on above conclusions, were explored and confirmed through different deposited experiments. Thus, the nodular growth in CVD-ZnS could be restrained effectively.
2018, 47(11): 1121003.
doi: 10.3788/IRLA201847.1121003
A femtosencond laser and a nanosecond laser were used to ablate the graphite target in the oxygen atmosphere and high vacuum respectively, and two kinds of diamond-like carbon films were prepared on the silicon substrates. Then their optical constants were estimated by fitting the infrared transmissivity curves. Double-layer diamond-like carbon film with different thickness combinations on the silicon samples were designed and prepared:the layer deposited by femtosencond laser in the oxygen atmosphere was taken as the infrared anti-reflective layer because of its low refractive index and high transmissivity; the layer deposited by nanosecond laser in the high vacuum was taken as the protective layer based on its high hardness and corrosion resistance. The tests show that transmissivity of the samples in the medium infrared band decreases by 0.5%~3% and the surface hardness of the samples increases by 7.2-24.7 GPa when the thickness of the protective layer increases. Results of the corrosion resistance tests show that the protective layer has the well corrosion resistance, but it can not prevent the alkaline liquor from soaking into the deeper depth to corrupt the lower anti-reflective layer if the thickness of the protective layer is very thin. The research result can offer the experiment basis for the designs of double-layer or multi-layer films in the different fields.
2018, 47(11): 1121004.
doi: 10.3788/IRLA201847.1121004
The effect of particle size, pH value and dispersant on the rheological properties, Zeta potential, viscosity and stability of slurry and its mechanism were studied. The experimental results show that the viscosity of slurry increases and the stability increases with the decrease of particle size at the same shear rate. When no dispersant is added in the slurry, the absolute value of Zeta potential of the ultra-fine magnesium aluminate spinel slurry under acidic condition is higher than that in alkaline condition. While, in the presence of dispersant, the pH value corresponding to the isoelectric point moves in an acidic direction, and the percentage of dispersant required for preparing low viscosity slurry decreases with the increase of solid content. pH value and dispersant content have the best range, if too high or too low, the rheological and stability of the slurry will be worse. The absolute value of the Zeta potential is just one aspect that affects the stability of the slurry, and if the dispersant is excessively large, even if the slurry particles Zeta potential absolute value is large, and the slurry will produce agglomeration and flocculation.
Due to its safety and high efficiency, photothermal therapy has been actively explored as minimally invasive approach to cancer therapy. The selection of nanoparticles to achieve photo thermal conversion efficiently is based on the absorption properties of the nanoparticles. Finite difference time domain method(FDTD) was used to calculate spectral absorption efficiencies for seven common types of gold nanoparticles:nanospheres, nanoshells, nanorods, nanosheets, nanocages, nanostars, and nanoflowers. The calculated results clearly demonstrate the dependence of absorption efficiencies and resonance wavelengths on the geometrical parameters of the nanoparticles. Via the volume absorption efficiencies, photothermal performance of the seven types of gold nanoparticles is compared quantitatively. The gold nanosheets are proved to offer the most superior photothermal performance in the near-infrared region (NIR) among the seven types of nanoparticles. From the vector distributions of the electric current densities, it is clearly shown that the resonant electric currents in the gold nanoparticles play the major role on the ultra large absorption cross-section in the NIR.
High performance ultraviolet(UV) photodetectors(PDs) are critical for the high-speed optical communication and environmental sensing. Here, the performance of ZnO PDs was improved by directly fabricating photoelectric device on the ZnO nanowires(NWs) networks made by chemical vapor deposition (CVD) without any seed layer or metal catalyst. Results showed that the photocurrent of the ZnO NWs networks PDs is 60 A, which was about 15 times of the single ZnO NW PDs. The response mechanism of ZnO NWs networks PDs was investigated in detail. Specially, the interconnections in ZnO NWs networks creat NW-NW junction barriers, which dominate the inter-wire charge transport. The fast tuning of NWs networks junction barrier height under the UV radiation, which contributes to the enhanced performance of the ZnO NWs networks UV PDs.
2018, 47(11): 1122001.
doi: 10.3788/IRLA201847.1122001
The self-pumped phase conjugate mirror(PCM) feature using the stimulated Brillouin scattering(SBS) phenomenon has great application value in improving the laser phase distribution and the energy concentration of the spot. Based on the phase conjugation characteristics of back scattered SBS light, the influence of different degree of distortion and different sampling aperture on SBS-PCM correction was numerically simulated. The SBS-PCM wavefront distortion compensation system was established to verify the compensation effect of different influencing factors. The simulation and experimental results show that under the condition of weak distortion, the spot distortion is more uniform and regular than the strong distortion after compensation, and meanwhile spot energy concentration is higher. In the case of strong distortion, large sampling aperture shows the advantage of better correction. Simulation and experimental results show that SBS-PCM has strong wavefront distortion correction capability.
2018, 47(11): 1122002.
doi: 10.3788/IRLA201847.1122002
The orbital angular momentum(OAM) beam loaded with the QPSK modulated signal was used as the transmission carrier to research the crosstalk of OAM multiplexed state under different atmospheric turbulence intensity, atmospheric turbulence was simulated by several phase screens. The study of the intensity and phase of the beam showed that there was obvious flickering phenomenon, when the light intensity of OAM multiplexed state was affected by turbulence. The greater the turbulence intensity, the greater impact was. The spiral spectrum was used to analyze the OAM multiplexed state dispersion degree between different turbulence intensity. With the increase of turbulence intensity, dispersion degree between OAM states increased, and the strong turbulence led to the OAM multiplexed state beam distortion. Meanwhile, considering the mode crosstalk between OAM multiplexed state and the inter-symbol interference of OAM states of each carrying information by the mixed noise model caused by atmospheric channel. The bit error rate(BER) changing with propagation distance under different atmospheric turbulence intensity was comparatively studied. The results show that the system BER increases with the increase of the propagation distance. Under strong turbulence the error rate of the light beam tends to be stable as the transmission distance increases to some extent. Under the weak turbulence the error rate of the light beam increases with the increase of the transmission distance.
2018, 47(11): 1122003.
doi: 10.3788/IRLA201847.1122003
Luby transform (LT) code is a rateless linear code, which has good channel adaptability and low complexity. A concatenated coding scheme of CRC code and LT code (CRC-LT code) was proposed to ensure the reliability of FSO system and improve the coding gain of LT code in FSO system by adjusting overhead. A new analytic model was developed to derive the data restoration probability with given conditions of channel. Finally, simulation experiments were performed over Gamma-Gamma channel model, and the relationships among data restoration probability, channel condition, SNR and overhead were given. The results show that CRC-LT code has better coding gain and can effectively enhance the reliability of the FSO system by increasing overhead.
2018, 47(11): 1122004.
doi: 10.3788/IRLA201847.1122004
In the quantum communication network, quantum routers can store and forward quantum clusters with limited length. In the metropolitan area network(MAN) and wide area network(WAN), date volumes are very large, as a result, a large number of quantum clusters can not be stored and forwarded because of the length constraint problem and can only be transmitted in the form of quantum packets. In order to solve the above problem, a fragment transmission scheme of quantum cluster was proposed, it fragmented the quantum clusters, which were not able to be stored and forwarded by the quantum router, so that the fragmented quantum cluster could satisfy the storage and forwarding condition of routers and could be directly transmitted. The simulation results show that in the MAN and WAN, a large number of quantum clusters need to be fragmented because of the large amount of date, so compared with the existing data transmission scheme based on quantum cluster, the proposed fragment transmission scheme of quantum cluster can achieve the data transmission by consuming the short time and less quantum entanglement resources, and own the better practical value.
2018, 47(11): 1131001.
doi: 10.3788/IRLA201847.1131001
A hybrid active disturbance rejection control (ADRC) scheme for stable loop was proposed. In order to make the semi-strapdown seekers have strong robustness under the coupling disturbances induced by disturbance torques and scale error and other uncertain perturbations. Firstly, the mathematic model of the semi-strapdown stable platform was established. Secondly, a hybrid ADRC system for the stable platform of a semi-strapdown seeker was designed. The influence of controller parameters on the control performance was analyzed by studying the frequency characteristics of ADRC, and the design principle of control parameters was given. Finally, the hybrid ADRC scheme was verified by mathematical simulation. The simulation results show that, compared with the traditional controller, the hybrid ADRC achieves better control accuracy and can effectively overcome the influence of disturbance torque and scale error on the seeker. The amplitude of the disturbance rejection rate (DRR) can be reduced by about 67.9% under the typical attitude disturbance frequency(2 Hz). The research results can provide guidance for the design of semi-strapdown seeker stable control system.
2018, 47(11): 1126001.
doi: 10.3788/IRLA201847.1126001
A novel image inpainting method based on sparse representation which combined image clustering and dictionary learning was proposed to solve the problems of long iteration time, bad adaptation and non-ideal results when using one single dictionary. Firstly, the broken image was divided into blocks and generated index matrix. Then Steering Kernel Regression Weight (SKRW) algorithm was used for image clustering. By exploring the inner structures of image and the information of intact area, blocks were sorted into categories based on their similarities of SKRW. Then each category had their own overcomplete dictionary by self-adaptive locality-sensitive dictionary learning. By building a self-adaptive local adaptor, the rate of convergence and the adaptability of sparse dictionary were improved. Multi-dictionaries were matched with different image structures, so the image would have a more accurate sparse representation. The dictionaries were updated until convergence, along with sparse coefficients as well. The image was finally restored after replacing patches back. Experimental results show that the proposed algorithm can repair the damaged images better than the state-of-the-art algorithms in both visual effect and objective evaluations. In addition, the time consumption is greatly reduced in comparison with the other algorithms.
2018, 47(11): 1126002.
doi: 10.3788/IRLA201847.1126002
In order to solve the problem of driver halation caused by the abuse of high beam lights at night, the anti-halation method of visible and infrared image fusion was proposed based on improved Curvelet transform in IHS color space. The method could effectively express the two-dimensional detail information of the image by improving the Curvelet transform, and improved the image clarity. The proposed fusion strategy of self-adjusting low-frequency coefficient weights could remove the halation information and avoid its participation in the fusion process. The color information in the original image was preserved by combining with the IHS transform to avoid color distortion. Subjective and objective analysis of the experiment results show that the method can eliminate the halation more completely. Compared with IHS-wavelet fusion, standard deviation, average gradient, edge intensity and entropy of the fusion image increase by 47.15%, 53.10%, 52.46% and 4.45%, respectively, its contrast and clarity are significantly enhanced, the details are also more abundant, and the visual effect of the human eye is better. The method is helpful for the driver to observe the road condition ahead, make judgment in advance, eliminate safe hidden trouble and improve the safety of night driving.
2018, 47(11): 1126003.
doi: 10.3788/IRLA201847.1126003
In order to accurately register and stitch the sequence images of the inner wall of the barrel, and get a image with high field of view and high resolution, a fast SIFT image stitching method with edge detection according to the characteristics of the overlap region of the images was proposed. It took full account of the characteristics of the images and could quickly segment the sub-region that possessed the most abundant anomalous information by detecting the edge of the region of interest. Then, it extracted SIFT feature points of the sub-region and matched them accurately by RANSAC. After that, a novel fusion method based on the weight of Sigmoid function weight was used to realize the seamless fusion between sequence images. This method can maximize the clarity of the fused image and the integrity of the detailed information. Experimental results show that the improved algorithm is much less time-consuming than that of traditional SIFT algorithm. Its computational efficiency has improved about 80% in feature points extraction process and the efficiency of the whole registration process has been also improved. The subjective evaluation and the various objective evaluation values of the fusion results by this fusion method are superior to other fusion methods.
2018, 47(11): 1126004.
doi: 10.3788/IRLA201847.1126004
The interaction of moving submerged target and fluid will generate specific wave patterns, such as the Kelvin wave and the Bernoulli dome, which provides possibility for the airborne and spaceborne radar to get the parameters including location and velocity of the target using photoelectric detection. It has become an important research direction. In order to study the characteristics of the wave pattern, a mathematic model was established by using the 3-D incompressible Reynolds-averaged Navier-Stokes (RANS) equations, RNG k- turbulence model and the volume-of-fluid (VOF) method. The simulation result of the wave patterns of the submerged target at different depths and velocities reveals the relationship between the parameters and the wave pattern. The result obtained is significant for the simulation and detection technology of real submarines.
2018, 47(11): 1126005.
doi: 10.3788/IRLA201847.1126005
Based on the the positional relationship between damage points and characteristics of optical damage dark field image, a registration method using connection vector feature matching was designed. The method firstly preprocessed the reference image and the image to be registered, and then extracted the center coordinates of the contour of the damage point as the position value of the damage point. Then the connection vector of the damage points was constructed, the main direction was obtained and the connection vector feature in the main direction was calculated, the exact match was achieved through the fine matches. Finally, the affine transformation parameter was calculated by using the RANSAC algorithm. The method had rotational invariance, scale invariance and high registration accuracy. The computational efficiency and registration precision of this method and SIFT algorithm were compared and analyzed. The experimental results show the more effectiveness of the proposed method in dark field image.
2018, 47(11): 1126006.
doi: 10.3788/IRLA201847.1126006
LK optical flow is an accurate and efficient feature tracking method which can be used to improve the performance of the image registration algorithm. For the registration problem of image sequence by time, a real-time and robust registration algorithm combining LK optical flow and improved FAST corners was proposed. The improved FAST corners was tracked by using the LK optical flow based on image pyramid and the registration parameters were calculated by adopting a robust homography estimation algorithm. In the experimental part, a real image sequence by time was used to verify the performance of the proposed algorithm from two aspects:registration accuracy and registration speed. The average re-projection error was 0.16 with the processing speed of 30 Hz. The experimental results show that the proposed algorithm can extract stable FAST corners and match the features between images efficiently and accurately, which solve the real-time registration problem of image sequence by time.
