2017 Vol. 46, No. S1
2017, 46(S1): 1-6.
doi: 10.3788/IRLA201746.S106001
Porosity is the main drawback during welding of galvanized steel sheets. In order to investigate the escape process of the zinc vapor produced during laser welding of galvanized high-strength steel plate (DP780), a high speed camera was used to record this escape process and channels. Based on the observation, the formation mechanism of internal porosity and external porosity was summarized, and the two-channel dynamic balance control method of zinc vapor escape was summarized based on this mechanism. By observing the test process and analyzing the actual formation rate of porosity, it is proved that the dynamic balance of the two escape channels can reduce the porosity of the welded joint. The experimental results show that, by improving the dynamic equilibrium of escape route of zinc vapor, the porosity of welded joints decreases 3.99 times. It shows that this method can well explain the splashing and external porosity defects of galvanized high strength steel plate, and improve the welding process parameters, so as to improve the efficiency of zinc vapor escape and the welding quality and appearance of galvanized high strength steel plate.
A metal thickness measurement system was presented, in which laser was used for exciting the ultrasounds, while interferometer and piezoelectric transducer(PZT) were adopted for receiving longitudinal acoustic waves. In accordance with mechanism of laser ultrasonic generation, the directivity model for longitudinal acoustic beam and the influencing factors were established and determined respectively, and formulas of two receiving modes were given as well. The effect of defocusing amount on thickness measurement was investigated, discovering phenomena that it would first increase then decrease finally disappear varying with increase of defocusing amount under the same laser pulse energy, consistent with the theoretical results, confirming the effectiveness of the study results.
2017, 46(S1): 13-17.
With the application of laser jamming technology in the field of infrared imaging guidance weapons, the research of laser jamming effectiveness and anti-jamming technology are also paid more and more attention, and they are also closely related to the laser jamming model. In order to construct a high confidence laser jamming model, firstly, the physical model of laser jamming and the characteristics of full link transmission were analyzed, and a theoretical model of laser jamming spot was established. At the same time, the influence law of different wavelength laser in atmospheric transmission and the variation law of irradiance with different divergence angle with distance were analyzed. Finally, the results of laser illumination camera experiment and digital simulation were compared, and the coherence between the laser jamming solar flare model and the laser jamming spot was verified.
2017, 46(S1): 18-23.
doi: 10.3788/IRLA201746.S106004
The commonly used BRDF function model in the active laser imaging system was analyzed in this paper. In order to further simplify the SUN model, real refractive index function was introduced to descript the characteristics of medium. On the basis of the traditional BRDF theory, a methed based on image analysis was proposed to analyze the BRDF values of targets in the active laser imaging system. Laser active imaging system was used to illuminate the target sample plate and image, and the target image was obtained by changing the angle between the target plate and the imaging system. The BRDF values of targets were calculated with the gray values of those images, and then the BRDF curves were obtained. Experimental measurement and simulation analysis were carried out for different materials. The results indicate that the reflection of specular reflection is stronger in the range of small angle, and the reflection of diffuse reflection targets can be detected within a larger angular range. The test results directly reflect the imaging performance, which can reflect the BRDF characteristics of different target materials. The results provide data and theoretical basis for the design of the laser active detection system of the space target and the performance analysis of the system.
2017, 46(S1): 24-28.
doi: 10.3788/IRLA201746.S106005
Using laser in centimeter scale space debris removal has important application prospect. Impulse coupling characteristics of laser ablated material of space debris was experimentally studied. Laser of 532/1 064 nm wavelength and 8/15 ns pulse width were used in experiment, and aluminum as the ablation target. Torsional balance system was used to measure impulse, and influence of laser parameter on impulse coupling coefficient was studied. Experiment results show that impulse coupling coefficient of Al shows a trend from rise to decline, and exists the optimal value. When ablation depended on gasification mechanism, decrease wavelength or increase pulse width can effectively improve impulse coupling coefficient; When ablation depended on ionization mechanism, plasma shielding effect of 532nm laser is weakened, achieving the optimal impulse coupling coefficient on initial formation of plasma.
2017, 46(S1): 29-35.
doi: 10.3788/IRLA201746.S106006
The number concentration of dust aerosol particles is hard to be directly measured, but it is one of the most important factors affecting the laser transmission characteristics. Based on the mass concentration of dust aerosol particles, using the size distribution of particles, the formula for calculating the number concentration of particles was deduced. Under the condition of sand and dust, the transmission characteristics of laser was studied by using Mie theory and Monte Carlo method, the relationship of the transmission attenuation and transmittance with wavelength and the mass concentration were analyzed, curve of visibility along with particle mass concentration was given, and the calculation results of Mie theory and Monte Carlo method were compared. The results show that, in the choice of several wavelengths, the transmission attenuation is minimum when wavelength is 10.6 m (about 58% of that in the 1.06 m), with the increase of mass concentration, the visibility decreased rapidly and then decreased slowly, whose trend is near hyperbolic curve. The method, basing on the mass concentration of particles(this parameter can be measured directly), can calculate the laser transmission characteristics of dust aerosol, which has very important theoretical significance in practical application.
The photonic laser propulsion is a new propulsion concept, which uses the thrust amplification generated by multiple momentum exchange and photon energy recycling through photon oscillation in external cavity composed of two HR mirrors. The experimental study and results related to photonic laser propulsion based on oscillation in external cavity of Gray and Edwards were analyzed. The principle of thrust amplification was introduced; the thrust calculated equations were deduced; the thruster simulation model was built. Finally, COMSOL was used to study and analyze the oscillation cavity's parameters'(cavity mirrors' distance, curvature radius, diameter, relative angle and aperture position) impact on thrust amplification by ray trace method, providing the establishment of future experiments with design basis and theory guidance. The simulation results indicate that in condition of 1 000 W and reflectivity 0.999, the maximum amplification factor 61 and maximum photon thrust 409 N can be realized, satisfying the needs of space missions.
2017, 46(S1): 43-49.
doi: 10.3788/IRLA201746.S106008
The high-power Q-switched pulse fiber laser was constructed. The high power pulse fiber laser was amplified to 101.4 W with the MOPA structure, with the output central wavelength of 1 064.52 nm. The repetition frequency of the pulse was 100 kHz with pulse width of 138.4 ns. The optical to optical conversion efficiency of master amplifier was about 80%. The laser stripping experiment system based on the high-power fiber pulse laser was constructed and it was applied in stripping the surface varnish layer of high-speed rail carriage. The effects of energy density and galvanometer scanning speed on the stripping of varnish were studied. The stripping threshold of the varnish layer was 19 108 mJ/cm2, stripping thickness was about 22 m. The damaged threshould was 34 392 mJ/cm2, the stripping efficiency could be up to 1 m2/h.
2017, 46(S1): 50-55.
doi: 10.3788/IRLA201746.S106009
In order to reveal the degeneration mechanism of triple-junction solar cell under intense light radiation, an n-on-1 mode irradiation experiment utilizing a 1 070 nm CW laser as the intense light source was carried out. By summarizing the I-V curves measured after each irradiation, it was found that the short current in triple-junction solar cell will increase when the laser intensity reach to 11.1 W/cm2, other than monotonically decrease with laser intensity increasing in single-junction solar cell. Combined with the relationship between short-circuit current and shunt resistance of current limiting sub-cell and QE of sub-cell, a theory was put up to explain the mechanism of this phenomenon, which indicates that it is the reduction of the shunt resistant in current limiting sub-cell failures its current limiting ability, and finally leads to short circuit current increasing. This theory was verified by equivalent circuit calculation with a simulation program with integrated circuit emphasis.
2017, 46(S1): 56-62.
doi: 10.3788/IRLA201746.S106010
The illumination effects of intense light on detectors are attracting wide interests. A whole process simulation framework of the illumination effects was introduced. The framework was consisted of four component, including the propagation of light, the heat transfer on FPA, the transport process of photodiode and the effects of post process circuit. We are attempting to reduce the coupling between each component through proper interface design, which leads to better adaptability for various physical models. A simple example with this framework was calculated. An analytic model including only diffracting effects was considered, and the differences of Gaussian and parallel light were discussed. In the heat transfer component, the Fourier's Law was introduced, and a simplified heat sink configuration was used. In the transport process component, the drift-diffusion equation including temperature effects was used to calculate the transport effects of photo diodes. The influences of neighboring pixels were neglected. In the post process circuit component, the Correlated Double Sample (CDS) configuration was used. The results show good agreement with previous work.
2017, 46(S1): 63-68.
doi: 10.3788/IRLA201746.S117001
Glint is the strong noise in the marine targets detection and it must be reduced. The traditional method that deploys one parallel line polarizer can only suppress the s-component of the glint. And the effectiveness of suppressing is due to the geometry of the sun and the detector. So the traditional method can only be used in few scenario. A new imaging system mounted two line polarizers was developed on the foundation of the theoretically analyzing the polarization characters of glint and marine targets. The experiment results show that under the condition of the non-Brewster angle specular reflection, while zenith angle of the light source and the imaging system without polarizer are 65, the contrast of the target image is 0.05. When the imaging system is mounted with only one parallel polarizer the contrast is 0.45, while mounted with two line polarizers which the angle between the two polarization directions is 45 the contrast is 0.9, and which the angle is 75 the contrast is 0.41. So the imaging system with two line polarizers which have reasonable design of polarization direction can effectively suppress glint interference, improve the contrast between the target and the background, which can improve the effect of marine targets detection covered in glint.
The vision position and attitude measurement system is an important part of the service system on orbit. Accurate measurements of the position and attitude of target spacecraft components are the prerequisite for successful completion of service operations on orbit. However, in the space radiation environment, the photoelectric sensitive parameters of the CMOS image sensor are attenuated under the irradiation of the space charged particles, which results in the performance degradation of the visual position attitude measurement system. After the CMOS sensor is irradiated by 3.0 MeV proton, the standard deviation of position calculation increases rapidly with the increase of irradiation fluence. When the proton fluence is 7.361010 p/cm2, the standard deviation of position calculation is 4.41-17.86 times as much as before irradiation. The standard deviation of attitude calculation decreases with the increase of radiation fluence. When the proton fluence is 7.361010 p/cm2, the standard deviation of attitude calculation is 2.76-5.85 times as much as before irradiation. The accuracy of attitude calculation is better than that of position calculation. That is to say, the proton irradiation has a greater effect on the position calculation accuracy of the visual sensor. The results lay the foundation for mastering the space radiation effect of vision system.
2017, 46(S1): 74-81.
doi: 10.3788/IRLA201746.S117003
In the process of propagation in the atmosphere, the laser is randomly disturbed by atmospheric turbulence, which leads to the laser intensity scintillation effect, and influences imaging lidar's target detection. In order to explore the influence of atmospheric turbulence on the power distribution of target echo, in this paper, a numerical simulation method was used to investigate the target-echo power distribution caught by imaging lidar of 5 m5 m gray ceramic tile in the situation of turbulence. Based on the FFT spectral inversion method which can construct atmospheric turbulence phase screens, lidar equation and the analyzing of the aperture smoothing theory on scintillation effect, the target echo, which is in front of the detector, caught by 128128-pixel imaging lidar with different turbulence intensity was simulated; at the distance of 2 000 m, and the atmospheric refractive index structure constant is 210-16 m-2/3-210-13 m-2/3, the target echo-power normalized mean square deviation relative to which considered the situation of no turbulence was 0.72-0.93, and the actual atmospheric refractive index structure constant which is 3.3210-16 m-2/3 was obtained, under actual conditions, at the distance of 500-2 000 m, the target echo-power normalized mean square deviation relative to which considered the situation of no turbulence was 0.19-0.81, Simulation experimental results show that, under the strong atmospheric turbulence and long-distance transmission conditions, considering the influence of atmospheric turbulence on the laser echo, the laser echo power distribution fluctuates larger relative to which not considering the influence of turbulence, so the influence of turbulence on imaging lidar target detection can't be ignored.
2017, 46(S1): 82-89.
doi: 10.3788/IRLA201746.S117004
With the further development of modern tongue diagnosis, reasonable use of tongue 3D color point cloud data has become a key step in TCM diagnosis and treatment of various diseases and obtaining the objective and quantitative information. By combining modern 3D point cloud processing technology with traditional TCM diagnosis experience, an algorithm for the Euclidean cluster segmentation of tongue based on the Fast Point Feature Color Histogram(FPFCH) eigenvalue and the region segmentation based on normal of tongue crack extraction was proposed. The FPFCH eigenvalues consisted of the extended Fast Point Feature Histogram(FPFH) component and the Hue(H) color component as the discriminant condition of the tongue point cloud after the Euclidean cluster segmentation. The area was segmented by judging the threshold of the normal line angle and the point cloud of the tongue crack was extracted. A large number of experiments show that the algorithm can effectively complete the tongue segmentation and tongue crack extraction, which provides technical support for the research of object diagnosis of the tongue.
2017, 46(S1): 90-95.
doi: 10.3788/IRLA201746.S113001
In order to solve the problem of low accuracy in the calculation of space objective optical cross section(OCS), the improved Phong model based on the BRDF data of the space object was used, and the surface of the satellite model was folded. In the STK, the motion scene of the satellites in different precession states was designed. The OCS timing data of these satellites were calculated respectively. The influence of the precession angle on the optical scattering characteristics of the satellite was found by comparing the data periodically. Further research shows that when the precession angle of the satellite is small, the rotation speed of the satellite can be retrieved from the optical scattering characteristic data of the satellite. When the precession angle of the satellite is larger than the critical value(for the scenario designed in this paper, the value is 30), it becomes impossible to invert the periodicity of the satellite from the optical scattering characteristic data of the satellite.
2017, 46(S1): 96-103.
doi: 10.3788/IRLA201746.S113002
The problem of multi-sensor detecting and multi-target tracking was mainly studied. Firstly, the observability was analyzed according to the detecting geometry of double satellite, and the state equations and measurement equations were established according to the turning model based on gravity. Secondly, for the problem that fight path tracking abnormity exists in the situation of tracking multi-target, the SME filter algorithm based on binary polynomial was raised. Finally, in order to improve the tracking accuracy, the improved UKF algorithm based on the iteration was raised. The simulation indicates that all targets can be well tracked with the BPGM-SME algorithm. Compared with UKF algorithm, the improved UKF algorithm can get better convergence effect, and the tracking accuracy is better.
2017, 46(S1): 104-109.
doi: 10.3788/IRLA201746.S113003
Space-based two-dimensional turntable is the main load-bearing structure of space photoelectric detection equipment, and the collimation frame is the key support component of turntable, so its stiffness characteristics are vital for the performance of turntable. In order to decrease the mass and improve the stiffness performance, the structure of collimation frame was topologically optimized based on the variable density theory by finite element software-MSC. Patran/Nastran. Modal shape of collimation frame was regarded as the deformation of model under the thrust. The model was optimized with stiffness maximization as the objective function, the ratio of residual volume as the constraints. The results show that the model weight after optimization is lighten 1.32 kg and the first-order natural frequency increases 14.5 Hz compared with the model of experience design. The maximum deformation is relatively reduced by 22.4% and the maximum stress value is relatively reduced by 42.6% under the action of gravity in the Z direction and the statics characteristic of model are increased significantly in the other directions. The dynamic characteristics of the collimation frame are improved significantly with the weight reduction. Modal experiment was done for the optimization model and the results indicate that the finite element analysis is correct. Therefore, it is feasible to use the method of topology optimization to design the structure of collimation frame.
2017, 46(S1): 110-114.
doi: 10.3788/IRLA201746.S121001
The four-heterostructure photonic crystal (AmaBmbCmc)m(DndBnbDnd)n(CmcBmbAma)m optical filtering properties were structured and studied by using transfer matrix method. The results show that it can realize adjustable multi-channel optical filtering function in the photonic crystal. When the number of periods m=6, n=1, ma=mb=mc=nb=nd=1, there are two narrow separate transmission peak in the transmission spectrum of the photonic crystals and it can realize dual-channel optical filtering function; when the periods number m increases, photonic crystal keep two-channel filter function, but the quality of dual channel optical filtering will be increased. When the periods number n increases, the number of the narrow transmission peak for the long wave will gradually increase, the photonic crystal implement n+1 channel optical filtering function; when the periods number nd increases, the number of narrow transmission peak will be increased by times and it can realize multiple sets of dual channel optical filter function. The four-heterstructure photonic crystal optical transmission characteristics can provide theoretical basis for designing a new type of tunable channel in designing photonic crystal optical filter.
2017, 46(S1): 115-119.
doi: 10.3788/IRLA201746.S121002
The modulation of quality factor by polarization in the photonic crystal quantum well as (FG)5(GFG)2(GF)5 was studied by using the transfer matrix method. The results show that:when vertical incidence, there are three independent transmission peaks as 100% transmissivity in the photonic crystal quantum well, and it can be an optical filter with three channels. For short wavelength, whether it is TE polarization or TM polarization, the quality factor of optical filtering will be decreased when the angle of incidence be increased. For medium long wavelength, when the angle of incidence be increased, the quality factor of optical filtering will be decreased in TE polarization, but decrease quickly in TM polarization. For long wavelength, all of the TE or TM polarization, the quality factor of optical filtering will be decreased when the angle of incidence be increased, and the growing more faster in TE polarization. When the angle of incidence be increased, the independent transmission peaks will blueshift in both of TE or TM polarization, the photonic crystal can be used as an optical switch. The rules can be designed for new photonic crystal omnidirectional reflector and provide theoretical basis for optical switch device.
2017, 46(S1): 120-124.
doi: 10.3788/IRLA201746.S121003
This research constructed and studied the optical transmission characteristics of heterostructure photonic crystal ABC)6D(ABC)6, that the physical thicknesses dA, dB, dC and dD of A, B, C and D can be used to adjust the transmission peak wavelength in the heterostructure photonic, to achieve short-wave and long-wave dual-channel optical switching, and the response sensitivity are different when the optical thin films thickness is changed by different dielectric medium. For short-wave channel optical switch, the transmission peak wavelengh will be increased with the thickness of dA, dB, dC and dD become thicker,this change is most sensitive to the response of dC, second to dB, and weakest to dA. For long-wave channel optical switch, with dA, dB, dC and dD increasing respectively, the transmission peak wavelengh moves to the long wave direction, this change is most sensitive to the response of dC, second to dD, and weakest to dA. The optical transmission characteristics of quaternary heterogeneous structure photonic crystal can provide a reference for the photonic crystal design of the new optical switch or filter devices.
2017, 46(S1): 125-130.
doi: 10.3788/IRLA201746.S121004
Chemical effect of polishing slurry and rotational speed are very important for Material Removal Rate(MRR) and surface quality during polishing. Under different rotational speed, the slurries with different pH were used for the analysis of spinel wafers lapping, and the effects of pH slurries on MRR and surface quality were explored. Through making the slurries with different pH, both groups of experiments were carried out of chemical mechanical polishing(CMP) at the speeds of 80 r/min and 100 r/min. The MRRs of spinel were measured using the lost weight analysis law, and the surface roughness was checked with a roughness instrument. They were used to analyze the effects of pH and rotational speed on lapping accuracy, and were also used to explore the mechanism of CMP. The results show that the MRRs increase with the rising of acid or alkaline, and that their roughness decreases instead. Of them, alkaline slurries have a greater effect on MRR and roughness. With the increase of rotational speed, MRR and surface roughness can also be increased obviously. A suitable speed should be considered carefully. The study will lay an experimental foundation for exploring further the chemical mechanical polishing mechanism.
2017, 46(S1): 131-136.
doi: 10.3788/IRLA201746.S126001
With the wide application of high-tech reconnaissance and precise guided weapons, military engineering faces more and more serious threats and challenges. Engineering decoy technology is an important means to improve the survivability of military engineering in wartime. Systematic classification of engineering camouflage decoys was done, and statuses of real shape and virtual decoy technology were presented, construction methods and application characteristics were introduced emphatically. Then the main development trend of decoy was forecasted. This paper provides an important reference for deceptive camouflage in large military engineering target.
2017, 46(S1): 137-142.
doi: 10.3788/IRLA201746.S126002
Multi-view laser point cloud registration is the basis of three dimension reconstruction, and the extraction of overlapping regions in multi-viewpoint laser point clouds is of great values to improve the efficiency of laser point cloud registration. A method of overlapping regions extraction based on region segmentation was presented, the spectral clustering was used to segment the point clouds of each viewpoint according to the geometric structure, and then a multi-dimensional shape descriptor was created for each region. The Euclidean distances were calculated for each extracted descriptor, the area with nearest Euclidean distance between descriptors was the overlapping area between point clouds. Experiments show that the algorithm is stable to the laser point clouds noise and the initial position, and the algorithm could still complete the extraction of overlapping regions in the case of large differences between point clouds. With the simulated multi-viewpoint point clouds, the overlap ratio increased by an average of 14.3%. And with the actual multi-viewpoint point clouds, the overlap ratio increased by an average of 13.3%.
2017, 46(S1): 143-150.
doi: 10.3788/IRLA201746.S126003
In order to study and analyse the influence the number of and quality of the training samples on the classification accuracy better, Helen city in Heilongjiang Province was chosen as the research required experimentation area, using Landsat 8 remote sensing images as the data source, the effects of the number and quantity of training samples on the classification accuracy were studied respectively by using the maximum likelihood, neural network and support vector machine three kinds of methods, and several experiments were made on these three kinds of classification methods. The final result shows that:(1) when the training sample quality is relatively constant, the degree of response of the same classification method to the same number of training samples as well as the degree of response of the different classification methods to the number of training samples are different, and the classification accuracy has different degree of volatility, with the increase of the number of training samples, the volatility will decrease, when the number of training samples reaches a certain degree, the mean of classification accuracy will tend to be relatively stable; (2) when the number of training samples is constant, the same classification methods as well as the different classification methods have different degree of response to the training samples of the same quality grade; the degree of response of the same classification method to the different training samples quality level is also different.
