2015 Vol. 44, No. 4
An eye-safe, all fiber, single mode, fiber laser based on master oscillator power amplifier configuration was presented. The advantages and disadvantages were compared between using a directly modulated diode laser and an electro-optical modulated continuous-wave diode as seed laser in sub-Mega Hertz, nanosecond fiber amplifier. The main restriction of power scaling in nanosecond fiber laser was pulse split. 10 m core double cladding erbium ytterbium co-doped fiber was employed as gain fiber of power amplifier. The directly modulated seed laser was then amplified by only two stage amplifiers. Finally, a peak power of 1.02 kW with 4.07 ns pulse duration at 200 kHz pulse repetition frequency with single-mode output was obtained and it is applicable in three dimensional video imaging lidar system.
2015, 44(4): 1110-1114.
In high dynamic environment,accelerometer size effect becomes a dominant error effect source for accurate navigation of Strapdown Inertial Navigation System(SINS). In this paper, the mechanism of size effect error, which is due to separate acceleration measurement points, was analyzed theoretically as well as size effect error caused by RLG dither. The error model of the accelerometer size effect was derived. Considering the non-orthogonal installation scheme of the accelerometer triad, dynamic calibration model involving size effect compensation was derived. Using the navigation velocity as the observation, a general error equation for the accelerometer triad was established. Through a convenient test scheme, the parameters of the size effect were determined. A series of swaying tests showed that the size effect error compensation could effectively improve the navigation accuracy.
2015, 44(4): 1115-1120.
In the target recognition of ladar, the accurate estimation of target pose can effectively simplify the recognition process. The existing PDVA algorithm as a method of target 3D pose estimation is mainly for ground structured targets. This method uses the planar normals of rigid targets as the vectors in the positive direction of the axes in model coordinate system(MCS) to estimate the 3D pose angles of targets, and its effectiveness has been verified by experiments. However, it is time consuming when determining the positive direction vectors of the axes in MCS and affecting the efficiency of the algorithm. In this paper, an improved PDVA algorithm was proposed and a method of clustering center neighborhood discriminant(CCND) was used for accelerating the determination process of positive direction vectors of the axes in MCS. The simulation experiments were performed with four military vehicle models. The results show that the average running time of the improved PDVA algorithm only accounts for about 66% of the PDVA algorithm, and it greatly improves the efficiency of target 3D pose estimation.
2015, 44(4): 1121-1125.
In order to study the molecular structure characteristics of 1,1-diamino-2,2-dintroethylene (FOX-7, a novel material with high energy and low sensibility), the absorption spectra of the explosive in the frequency range from 0.2 to 2.3 THz were detected by terahertz time-domain spectroscopy. The terahertz absorption spectra and the characteristic peaks were obtained. The article also simulated absorption spectra of FOX -7 single molecule and molecular crystal within 0.2-2.4 THz region using density functional theory (DFT), which showed that the interaction between molecules played a major role in forming absorption peaks of FOX-7. Besides, the vibrational modes of the characteristic peaks in the experimental absorption spectra were analyzed and identified. The absorption peak at 1.59 THz was mainly due to the swinging vibration of nitro and amido groups, and the peak at 2.12 THz originated from two kinds of vibrations (the swinging, torsion vibration of the nitro and amido groups).
2015, 44(4): 1126-1133.
To study the process of laser clad Al/Ti composite powder above 7050 aluminum, a three dimensional model was established, which can simulate the molten pool size, the temperature gradient, cooling rate and the shape control factor in the condition of different defocusing amount. The simulated results show that the width and depth of the molten pools are positively correlated to the defocusing amount, but negatively correlated after the defocusing amount reaches 20 mm. Both the max temperature gradient numerical value and the best cooling condition appear in the Z direction, which also indicate the growth direction of grains mainly concentrates on the Z direction. The cooling speed reaches the highest and the grain size is small when the defocusing amount is 40 mm. The cooling speed is lowest and grain size is big when the defocusing amount is 80 mm. Moreover, the shape control factor is biggest and the crystal microstructure is columnar when the defocusing amount is 60 mm, and the shape control factor is smallest with cellular crystal microstructure when the defocusing amount 80 mm. Finally, the simulated results about both the grain size and the crystal microstructure of the molten pool are verified by the experiment study.
2015, 44(4): 1134-1140.
Based on the long-term observations from Beijing sodium lidar of Chinese Meridian Project, 162 monochromatic gravity waves was distinguished in the sodium layer during the 2208 hours' observation in 253 nights(from 2010 April to 2011 September). The vertical wavelength, wave period, wave amplitude and its growth factor of every monochromatic gravity wave were precisely extracted with the method derived by Yang et al.(2008). Statistical results reveal that there are systematic relationships between those wave parameters, and they respectively are z=0.226Tob0.530、KE=6.6610-10 kz-3.091 and KE=8.9710-6 fob-1.696. Those results partially agree well with the results predicted by Gardner's(1994) diffusive filtering theory. However, it is found incorrect to regard the wave-induced eddy diffusivity as the only main damping processes of gravity waves. It is suggested that the damping processes caused by other possible factors also play important roles in the saturation and dissipation mechanisms of gravity waves.
2015, 44(4): 1141-1144.
In the Tm, Ho laser system, the optimum transmittance and pulse duration was practiced using the rate equations theory. In a 2 m ring resonator, the Tm, Ho: LuLF laser material was side-pumped from three directions and Q-swtiched of acoustic-optic device. The output coupler of 20% and 30% transmittance was compared. In the 20% transmittance coupler, it was demonstrated that the Q-switched laser pulse energy of 58.0 mJ with an optical to optical efficiency of 1.45%. The 62.9 mJ energy was obtained with the optical to optical efficiency of 1.57% in the 30% transmittance coupler. And the 48.7% of dynamic to static ratio was obtained in the same injection. The pulse duration was 417.2 ns when 3.25 J energy was injected. The experiment values are in consistent with the simulation results.
2015, 44(4): 1145-1149.
In order to improve mechanical properties of 1Cr5Mo heat-resistant steel welded joints, the surface was modified with CO2 laser, and the tensile tests were conducted to research the effect of LHT(laser heat treatment) on tensile properties of welded joints. The rupture modes and the fracture morphologies were analyzed with SEM(scanning electron microscopy), the changes of chemical elements in the sample surface before and after LHT were analyzed with EDS(energy disperse spectroscopy), and the effects of residual stress and retained austenite on tensile properties were discussed. The results show that the fracture of the samples before and after LHT are ductile rupture, the rupture properties have been improved. After LHT, the strengthened layer of compressive residual stress and refined grains are generated in the sufrace, which cause yield strength and tensile strength to increase by 3.4% and 13.7%, and the tensile properties increased. The content of retained austenite decreases in the sample surface after LHT, which causes the section reduction rate to decrease by 18.61%, the elongation rate nearly doesn't change, and the ability of uniform deformation has improved.
2015, 44(4): 1150-1157.
The surface-type infrared decoy is an effective interference equipment to jam infrared imaging guided missile. It can jam the approaching infrared imaging guided missile by simulating the infrared signatures of the fighter to be protected. Firstly, the mechanism of surface-type infrared decoy for jamming infrared imaging guided missile was analyzed. Secondly, the radiation and moving models of surface-type infrared decoy were built. Then, the change rules of the surface-type infrared decoy's position, area and gray-scale were analyzed. The infrared images of the surface-type infrared decoy were generated. Finally, regarding the jamming success probability as the jamming effect evaluation criterion of surface-type infrared decoy, the jamming success probability in different distances and different quantities were calculated, and the simulation results were analyzed. The simulation results show that the surface-type infrared decoy can realistically simulate the spectral radiation distribution characteristic of fighter, which can effectively jam the infrared imaging guided missile and greatly improve the battlefield survivability of fighter.
2015, 44(4): 1158-1163.
The influences of infrared optical system structure parameters, which caused by temperature change, was analyzed. And the condition of infrared optical system athermal design was provided. Then, the temperature characteristic of diffractive optical element was discussed, and it was introduced into infrared optical system athermal design. A long-wave infrared optical system with hybrid refractive/diffractive was designed by ZEMAX. The system was composed of three lenses, which used only two materials of Ge and ZnS, including five spherical surfaces and a diffractive surface. Its operating band was 8 to 12 m, the filed of vision angle was 10.2, the focal length was 45 mm, the F/number was 1.5 and the total length was 70 mm.The design result shows that the image quality of the system can approach the diffraction limit at the working temperature of -40 ℃ to 60 ℃. The modulation transfer function(MTF) is greater than 0.6 in the full filed of vision when the Nyquist frequency of detector is 20 lp/mm, and 87% of the energy is focused in single pixel. The imaging quality of the system is good, and athermal design is realized. The optical system has many advantages, such as compact structure, small volume, light weight and so on. It can be applied to martial or special infrared system.
2015, 44(4): 1164-1171.
In order to suppress the effects of stray light radiation on imaging for mid-infrared plane grating spectrometer system. First, the sources of stray light for spectrometer system were investigated, the baffle, vane and Lyot stop were designed. Then a new method of combining shutter barrier and stray light collector was proposed to solve the shortage of using normal light barrier to suppress the higher order diffraction stray light, and Solidworks and Tracepro softwares were used to model, analyze and compare the system. Finally, the sytem using an infrared thermopile array detector according to blackbody radiation theory was calculated and analyzed. Final analysis results show that the Point Sources Transmittance of the spectrometer can reach the level of 10-11, effective emissivity is 1.3%, two results show that the stray light suppression can meet the requirements.
2015, 44(4): 1172-1177.
The problems of baseline drifting and distortion of mixed gases infrared spectra in the application field and the uncertain choice of the Rubberband's piecewise quantity were discussed. In the situation of the spectrometer resolution of 4 cm-1 and mid-infrared band for the hydrocarbon gases, the baseline estimation and correction would be more ideal in the case of the piecewise quantity was set in the 50-120 and piecewise cubic Hermite interpolation method was selected to fit the baseline points by the ergodic method. For the problem of absorption points,which was mistaked as the baseline points, first of all, the obvious absorption points within the segment were eliminated by the method of the median and deviation. And then, the baseline points were selected by the partial least square method and certain threshold was set in the residual baseline points. Lastly, the selected baseline points was used to estimate the baseline by piecewise cubic Hermite interpolation method in the whole band. From the baseline correction result of the measured spectra, the provided method was simple and fast, and also suitable for on-line continuous analysis applications.
2015, 44(4): 1178-1185.
To study the influence of temperature change on the spectrum quantitative analysis of greenhouse gases and carbon isotope ratio,at first, the view that the quantitative analysis of greenhouse gases and 13CO2 value was mainly determined by the absorption coefficient was analyzed theoretically, and the calculation method of the absorption coefficient was also studied. Then referring to the HITRAN database, the temperature dependence of line intensity, FWHM and absorption coefficient were studied, the results show that the effect of line intensity is stronger than the FWHM on the absorption coefficient when the pressure is constant at 1 atm while the temperature changes. At last, the temperature dependence of greenhouse gases and carbon isotope ratio quantitative analysis based on Fourier transform infrared spectroscopy(FTIR) method was confirmed through a series of experiment, and these experiments also present that the variation of carbon isotope is more serious than the greenhouse gases variation when the temperature changes, the 13CO2 value will change 14.37 while the temperature changes 1 ℃. This study is the theoretical basis for the design of the temperature monitoring and controlling system of greenhouse gases and carbon isotope ration monitoring instrument based on FTIR with high-precision.
2015, 44(4): 1186-1192.
People-counting systems for image acquisition are usually complicated and expensive. In this paper, with detailed analysis of the pyroelectric effect and infrared sensor, BISS0001 integrated signal processing chip were chosen to design an amplifier circuit for the RE200B pyroelectric infrared sensor, in order to study its output waveforms under various human movement states. A people-counting system was designed, with double pyroelectric infrared sensors as the signal acquisition unit and a Cortex-M3 microcontroller as the control core, and its main algorithms were researched. The experimental results demonstrate that different body movement states can be accurately characterized using the output waveforms of the RE200B pyroelectric infrared sensor and the movement directions can be precisely distinguished by the people-counting system based on double pyroelectric infrared sensors designed in this paper. Furthermore, the system realizes real-time counting, and can be applied to a wide range of areas including human body detection and counting.
2015, 44(4): 1193-1197.
According to the less accessibility characteristics for the detection of defects will result in detection ineffective and quantitative inaccurate. The study focused on the subject of aluminum plate,based on infrared nondestructive testing technology, combined with principal component analysis and probabilistic neural network(PNN)on the normal area and three kinds of cavity defects area for the recognition and area of quantitative evaluation. Firstly, research during the cooling process of heating aluminum plate,the initial characteristics were obtained from the sequence grey value of normal and three kinds of cavity defects area on the basis of sequence infrared image. And the principal component analysis was used to extract initial characteristics. Finally, combined with the probabilistic neural network, the cavity defects were identified and quantitatively evaluated in pixels. And the support vector machine was used to carry on the comparative study. Experimental results show that the evaluation accuracy rates of the normal and the three kinds of cavity defects area were 99.6%, 97.0%, 94.7% and 93.0% respectively, compared with the evaluation results of support vector machine, the proposed research method has higher accuracy. Research demonstrates that using principal component analysis and PNN, based on the temporal characteristics, to achieve the effectiveness and accuracy of the cavity defects identification and quantitative analysis of the area in units of pixels.
2015, 44(4): 1198-1202.
Focus on color fusion for infrared and visible images with low contrast between target and background issues, a contrast enhancement method for infrared and visible image was presented based on HSI color space. Firstly, the contrast of infrared and visible images was enhanced using local histogram equalization and median filter, then the infrared target was extracted from the enhanced infrared image after fuzzy threshold segmentation. Finally, the two enhanced images and the segmentation infrared target were fused into the three components of a HSI image in terms of a simple linear fusion strategy and color transfer. To enhance the color contrast between the target and the background, a scaling factor was introduced into the transferring equation in the H channel during color transfer process. The experimental results show that, compared with other algorithms, the color fusion images of hot target and color contrast between low temperature object and background abtained by the presented method enhance obviously. At the same time, the details of visible images are endowed with natural color similar to that of the light color images during the day, which is more confortable to the human's visual perception.
2015, 44(4): 1203-1207.
Moir fringe, Fourier transform and digital phase shifting techniques are combined together to realize high precision phase calculation and wavefront reconstruction for the single interferogram. First, four digital phase shifting fringes, which the frequency is similar with the original fringe tested, were generated by computer, and phase shifting Moir fringesare formed by superposition of original and digital fringes. Then, the phase of original interferogram was obtained through Fourier transform, double frequency filtering, inverse Fourier transform and phase shift technology. Finally, the wavefront shape related original interferogram was reconstructed by wavefront fitting. The experimental result shows that this technology not only removes both of nonlinear error from traditional hardware phase shifting and spectral shift error, and get wavefront with high precision for single interferogram, but also simplifies the mechanical structure of system. At the same time, it reduces the demands on the environment, so it is very much suitable to use in work shop.
2015, 44(4): 1208-1217.
Based on Xilinx XC2V3000 chip, a multi-channel irradiation resistance enhanced (Time-to-Digital Converter, TDC) system was designed. 16-channel high-precision time measurement was achieved within 2 FPGAs in a single board. With multi-redundant delay-chain structure, each measuring channel consisting of three physical timing links, and the anti-SEU ability was enhanced by triple modular redundancy. The channel uniformity calibration correction technology was applied to solve the multi-channel uniformity issues. Experimental results prove that the system meets the requirements of a 3D imaging laser radar, with an accuracy of 62.9 ps and a good uniformity. Meanwhile, the technical solution provides has a character of low power consumption, light weight etc.
2015, 44(4): 1218-1222.
The workspace Measuring and Positioning System(wMPS) is an indoor large-scale positioning system based on the intersection of rotating laser planes. It can provide 3D coordinates with metrological accuracy, applicable in the measurement and test tasks of manufacturing and assembly. As a large-scale measurement system, the contradiction between its measurement range and measurement precision is more intense than the small-to-medium-scale measurement system. How to find the optimal measurement point or the optimal measurement area centered with this point is an important and significant problem. Moving away from the measurement principle of the measurement system, compared with the traditional theodolite, an evaluation model was presented, which used the condition number of the coefficient matrix of the measurement equation as the indicator of the quality of intersection, then the Particle Swarm Optimization algorithm was introduced to solve the optimal measurement point. The experimental results show that the proposed evaluation model and the problem-solving method are correct and effective; they produce the minimum uncertainty around the calculated optimal point, and lay the foundation for the future research on the transmitter-layout problem.
2015, 44(4): 1223-1228.
As an important trend in the future, multiple heads star tracker is not only of higher reliability and autonomy, but also of higher precision and dynamic performance than classical star tracker. In order to achieve the best performance, system parameters optimization for multiple heads star tracker is needed. A mathematical model of multiple heads star tracker was developed firstly, particularly on the star imaging and attitude determination. Then an analytic expression of accuracy was deduced, and the error sources affecting the attitude accuracy were analyzed. Finally, the effects of the field of view and the relative alignment on the accuracy were discussed systematically based on the simulation results. The results show that the relation between field of view and accuracy depends on the angular rate. The accuracy is improved with smaller field of view at lower angular rate, while with larger field of view at higher angular rate. And multiple heads star sensor reaches the highest precision when the boresights are orthogonal.
2015, 44(4): 1229-1235.
In order to meet the high precision ground calibration and testing of sun sensor in satellite control system, a realistic simulation of solar radiation characteristic of high precision collimated solar simulator design was presented, according to the characteristics of simulator with high thermal power. The main component of the Xenon lamp in combination with the condenser lens, steering plane mirror and optical integrator was designed in detailed structure of the heat-ray control structure. Using Ansys software for thermal simulation to ensure the rationality and optimality of thermal control structure. By the actual detecting, the designed solar simulator can simulate the real characteristics of solar radiation, collimation angle is less than 32', unevenness is better than 1.6% when the irradiation surface is less than 100 mm; unevenness is better than 4.2% when the irradiation surface is (100-300) mm, meeting the high precision ground calibration and testing of sun sensor.
2015, 44(4): 1236-1242.
An eight-step broadband light phase shifting algorithm was proposed for the determination of three dimensional micro textures. The actual phase step was calibrated to eliminate the phase shifting error, from the difference between the phase values of two neighbored sampling of the broadband light interference signal. The microscopic interference fringes with phase shifting error of the oblique SiC flat were analyzed. The standard deviation is 1.646 nm, showing excellent agreement with the result obtained without phase shifting error. The proposed method, insensitive to envelop variation and phase shifting error of the interference signal, is practical and accurate for understanding three dimensional micro textures.
2015, 44(4): 1243-1248.
The polarization effect of the imperfect lens components changes the analysis matrix of the polarimetry system, so the optimum configuration of the system shifts. In order to maximize SNR of the aerosol polarimeter, the polarization degree of the imperfect lens components was computed by means of Jones matrix, and the optimum azimuth angles of polarizers were found to minimize the condition number of the system analysis matrix and the parameter Tr(BBT), respectively. After optimizing, the optimum angles of polarizers at 670 nm channel and 1 641 nm channel were found, respectively. The condition number of the system analysis matrix reduced from 1.836 0 to 1.689 4 at 670 nm channel, while that of the system analysis matrix fall from 1.977 7 to 1.771 4 at 1 641 nm channel. It is indicated that the results of these two optimization methods are consistent, and both of the SNRs are is improved about 10% at 670 nm and 1 641 nm channels.
2015, 44(4): 1249-1253.
Guide star selection is a crucial part of star tracker design. For thin field-of-view star tracker, guide star catalogholes are common as stars are not evenly distributed. To optimize the guide star selection for star tracker with thin field of view, the selection method based on spherical spiral points was modified. Building a new guide star catalog by increasing the number and changing the positions of spherical spiral points, which was usually adopted, was abandoned. Some new stars which can effectively decrease guide star catalogholes into the guide star catalog were proposed. The weights to measure stars' ability of decreasing guide star catalog holes were constructed and the adding star process was carried out on the order of the weights descending. And the new star added into guide star catalog was required far away from the guide stars to keep the guide stars even. Simulations expressed that the modified method got less and evener guide stars than the original method with similar guide star catalog holes, which shows the superiority of the modified method.
2015, 44(4): 1254-1259.
The original positioning method for digital zenith camera has the problems that its calculation process is complicated and during the process some errors are introduced. By changing the way of time compensation and optimizing the iteration core, an improved positioning method was proposed. The mean in tangent plane is calculated by this method, so it can eliminate the errors in original method. Besides, by this method, the positioning process can also be simplified by avoiding the repeated calculation of tangent transformation and inverse tangent transformation. The efficiency and accuracy of these two methods were compared through experiments. The result shows that, the efficiency of improved method is more than 6 times higher than the original one; the declination calculated by improved method is 1.05 m more accurate than the original 15 m. Therefore, compared with the original method, the positioning accuracy is improved with the improved method.
2015, 44(4): 1260-1266.
An alt-azimuth shafting structure with high precision standard bearings was designed for a 600 mm scaled down model telescope system, which is for studying the large telescope thin mirror active optics technology. It has more benefits including quick installation and adjusting, high interchangeability, and easy maintenance. The altitude shafting is consisted of a pair of radial angular contact ball bearings. The azimuth shafting is consisted of thrust ball bearing and double-row cylinder roller bearing. The lowest three order natural frequencies and the modes were resolved by the finite element simulation software Patran. The error sources were analyzed, which are mainly affecting the shafting rotating accuracy. The measuring results were processed by harmonic theory and it shows good performance in the altitude shafting wobble error of 4.2 , and the azimuth shafting wobble error of 9.3. Desirable imaging was got in the stars observing test at the testing field. The design can prove reliability of the shafting structure, and offer a reliable guidance and advanced path for developing the high precision shafting of medium and small sized telescope.
2015, 44(4): 1267-1272.
To improve the optical performance of optical window on the condition of high Mach flying, the structures of flight number field, density field, temperature field and pressure field corresponding to three kinds of aircraft on the angle of attack conditions on 0, 5 and 10 were provided and compared in this paper, as well as the influence to the optical properties of optical system. Firstly, three typical kinds of aircraft models were established based on the windward area of the aircraft head; secondly, the flight conditions on the angle of attack of 0 , 5 and 10 as well as the flight initial environment were provided; then, according to the Navier-Stokes equation and the turbulent model, the flow field distributions corresponding to the three kinds of aircraft model on the conditions of 0, 5 and 10 were obtained and analyzed; finally, taking the optical system on the operating condition of the flat -head aircraft as an example, the Modulation Transfer Function(MTF) on the operating conditions of the three kinds of attack angle were compared and analyzed. By the analyzed results, the Mach field and the destiny field, the temperature field and press field have the same distribution respectively; in the same flight velocity and angle of attack, the optical window of the aircraft owning large windward side has larger temperature and press than the optical window of small windward side aircraft; being the same aircraft, the operating condition of larger angle of attack corresponds to large flow field around the optical window. When the angles of attack are 0, 5 and 10, the values of MTF are 0.188, 0.097 and 0.028, respectively. The work of this study may provide a theoretical basis for the optimization of optical window on the operating condition of high Mach.
2015, 44(4): 1273-1277.
Active support based on axial force correction was widely applied to optical mirror support, while the research of moment correction was infrequency. In order to profoundly develop such study, the active support based on moment correction was introduced in the foundation of force correction. First, according to the principle of active support, the category of active correction for mirror surface was introduced. Especially, the difference between force correction and moment correction was compared in detail. Then a lightweight mirror with the aperture of 400 mm was selected to be calculated and optimized in statics, according to applying three groups equivalent moments. As a result, the mirror deformation was reduced from 331 nm to 9.35 nm, the rate of optimization was 97%. In conclusion, the active support based on moment correction was effective, and a new idea was introduced for an smart and diversified active support.
2015, 44(4): 1278-1283.
The spatial resolution of ground-based telescopes was greatly limited by the effects of atmospheric turbulence. Lucky imaging can efficiently reduce the blurring effects of atmospheric turbulence with low cost, uncomplicated instrument and easy actualizing solution. Lucky imaging system is based on the 50cm telescope at Xinglong Observatory. It consists of filters, subsystem of barlow lens which increases the focal length of telescope, subsystem of data acquisition and subsystem of data reduction. The moon, globular clusters and close binary stars were observed in good seeing conditions, by using the lucky imaging system. Sharp images of the lunar surface, and FWHM of 0.6 of stars which is two times better than the diffraction of the 50cm telescope were obtained successfully. The experimental results show that this system can greatly improve the spatial resolution of ground-based telescopes, and it would play an important role in subsequent high resolution astronomical observations.
2015, 44(4): 1284-1289.
Logarithmic axicon (LA) was proposed to overcome the defocus in the spherical compound eye imaging utilizing its focal line. The depth of field of LA was designed to meet the requirements of all the channels of the compound eye. On-axis and off-axis characteristics of LA were studied based on numerical simulation. Mass production of LA was achieved by diamond cutting and molding technology. Experimental results show that the on-axis point spread function(PSF) keeps constant along the propagation, while the off-axis PSF is cross-shaped. The intersection of the cross can be extracted and used to determine the spot centroid in off-axis imaging. The proposed method is helpful to eliminate the intrinsic defocus effects of spherical lens and improve the positioning accuracy and imaging quality of the spherical compound eye system.
2015, 44(4): 1290-1296.
In this thesis, the detail design of the system was discussed, including inspection system and the surface plasmon resonance (SPR) sensors based on taper technology. An Optical Fiber Sensor comparison scheme based on SPR detection of measuring the salinity of water sample was formulated to meet some practice requirements,such as accuracy, fast, small size and high sensitivity RIU(Refractive index units). The influence of each parameter on the optical fiber SPR sensor system design was simulated by using Matlab and C++, which gave a theoretical base for the choice of suitable parameters in device design. Then a new detection system, combing with optics, mechanism and electronic technology, was designed. According to the taper technology and mode field analysis theory, result of preliminary experiment shows that this device is basically met the design requirements such as compact, portable, good linearity and highly RIU. SPR experiments about NACL-water mixture with different salinity are implemented in this new device, and experimental results show that accurate detection on single sample can be achieved, and the detecting of the resonance wavelength differentiation is 0.15 nm, moreover, the detecting results has high linearity and good stability, and the refraction index(RI) detecting deviation is less than 0.002.
2015, 44(4): 1297-1300.
A method to determine the phase difference in a 33 fiber coupler by the all fiber optic current transducer was presented. The theoretical model of the response of an all fiber optic current transducer, according to the principle of the Sagnac interferometer, to the parameters of phase difference of a 33 fiber coupler and the interference fringe was established. An objective function was constructed by calculating the sum of square error of the measured response and the predicted response with different couples of unknown parameters. An optimization algorithm was used to obtain the phase difference and the interference fringe. Experimental research was carried out on a commercial 33 coupler, and the measurement result agrees well with the theoretical estimation.
2015, 44(4): 1301-1305.
In order to thoroughly understand the characteristics of the temporal spectrum of atmospheric scintillation and provide references for engineering design and performance evaluation of the optics system employed in the atmosphere, the generally analytic expression of the atmosphere scintillation power spectrum was theoretically deduced and the frequency domain characteristics of atmospheric scintillation under different propagation conditions was numerically investigated. For horizontal path with an aperture receiver, in the high frequency area, the scintillation power spectrum of the plane wave obeys the power law with an exponent of -17/3, while the scintillation power spectrum of the spherical wave obeys the power law with an exponent of -11/3; for the whole layer downlink path, the scintillation power spectra obey the power law with an exponent of -17/3 in the high frequency area, and there is a slow transformation area between the low frequency area and the high frequency area. The larger the aperture becomes, the wider the slow transformation area grows; besides the frequency spectrum width of the low frequency area and the slow transformation area is about 150 Hz under typical atmosphere conditions for plane wave.
2015, 44(4): 1306-1310.
An optimized scheme was proposed to generate optical triangular pulses by using chirped fiber Bragg grating(FBG) and Mach-Zehnder modulator. Optical triangular pulses were obtained based on dispersion character of standard single-mode fiber substituted for a chirped FBG combined with optical carrier suppression modulation. The obtained triangular pulses' linear feature was optimized by simulation analysis of length, modulation index, and appropriate apodization of FBG. The simulation results indicate that the distortion of finally generated triangular pulses increase with the modulation index's raising under the same chirp coefficient. The length of fiber grating and the apodization also have an obvious impact on the triangular pulses. Compared with the present generator, the proposed system has distinct advantages of simple configuration and the triangular pulses have better linear characteristic own to the small size chirped fiber grating replacing the long distance optical fiber.
2015, 44(4): 1311-1316.
According to the resources, missions and restraints of the data relay satellite optical network, a scheduling algorithm based on improved self-adaptive genetic algorithm was put forwarded. Considering the multi-relay satellite, multi-window, multi-optical-antenna and multi-mission PRI, the model was established. The missions were scheduled by the scheduling operates: the ascertainment of current mission scheduling time and the refreshment of latter mission time-window. The whole weight of the scheduled missions was set as the cost value and the scheduling schemes were optimized by the self-adaptive genetic algorithm. The simulation scene including 3 relay satellites, 12 user satellites, 6 antennas and 60 missions, the result reveals that the algorithm obtains satisfactory results in both time and optimization which is suitable in multi-user, multi-mission and multi-optical-antenna recourse scheduling.
2015, 44(4): 1317-1322.
Silver nanoparticles, combine with PCF and surface enhanced Raman scattering(SERS), form SERS PCF sensor, and has been applied widely. But in practical, the PCF structure and the performance of SERS substrate have fatal influence on sensor. To exert sensor's practical applications fully, the influence of HCPCF(hollow core PCF) and silver nanoparticles substrate structure on sensor were researched and analyzed, then the novel HCPCF and silver nano-substrate were designed to suit for SERS PCF sensor. Through numerical calculation, the air filling fraction of designed HCPCF is 56.30%. When incident wavelength is 785 nm, there is the photonic bandgap in HCPCF, and HCPCF can transmit fundamental mode, so it suits SERS sensor very well. And silver nanosphere whose radius is 38 nm, and separation distance is 0.7 nm has maximum SERS enhancement factor. The results show that when incident wavelength is 785 nm, the designed HCPCF can supply perfect active area, and the shape, size and separation distance of silver nanoparticles have serious influence on SERS performance, moreover SERS performance rely on incident wavelength seriously.
2015, 44(4): 1323-1328.
Dynamic test data fitting method was widely used in Gyro dynamic north algorithm at present. In this study, rapid dynamic north method based on cross-correlation function was presented to overcome the shortcomings of the weak denosing effect and large amount of data in dynamic test data fitting method and to deduce find north principle formula. This method firstly modulated the output signal of a ring laser gyro and accelerometer to create a certain frequency triangular amplitude modulation wave by continuous constant speed rotation. Then, calculated the cross-correlation function of two lines with the same frequency reference signal and the output signal of gyro and accelerometer separately, based on the nature of the cross-correlation function associated with the frequency, which to eliminate the accuracy effect of find north by inertial device drift and noise. The simulation results show that the new algorithm can realize all-attitude north finding in high precision and the error of azimuth angle and attitude angle is less than 0.01 after 30 s find north. The experiment on the north-finder results indicates that this algorithm can effectively restrain all kinds of noise in the measurement process of inertial devices, and the standard deviation is about 32.7 for 5 min, which can basically satisfy the requirement of high precision north-finding.
2015, 44(4): 1329-1334.
A subwavelength conductor gap silicon(CGS) hybrid plasma waveguide was theoretically analyzed, which consisted of a thin low-index layer sandwiched between a silver strip and a high index silicon structure. The guiding properties of surface plasmon polaritons, such as propagation length and mode field area, were investigated for different rib widths and silica gap layer thickness. As a result, an effective modal area of 0.08 m2 and the propagation length of 430 m can be achieved simultaneously. Based on which, the silicon slab based CGS waveguide can be formed by increasing the width of silicon rib, it should be noted that the structure can generate the larger effective refractive index value of 2.8 and the propagation length of 1.74 mm, moreover, it provided a more strong confinement of the optical field such as 0.025 m2 thickness SiO2 gap. In addition, more simple structure and CMOS compatible fabrication process make these conductor gap silicon plasmonic waveguide a promising candidate for realizing high integration density plasmonic circuits.
2015, 44(4): 1335-1342.
To improve the thermal stability of Al/Zr multilayers, eighteen Al(1 wt.%Si)/Zr multilayers with different thickness(0.4 nm, 0.6 nm and 0.8 nm) of Si barrier layers were prepared by using the direct-current magnetron sputtering system. All the multilayers were annealed from 100 ℃ to 500 ℃ in a vacuum furnace for 1 h. To evaluate the effect of Si barrier layers on the thermal stability of Al/Zr system, the multilayers were characterized by grazing incidence X-ray reflectance(GIXR) and X-ray diffraction (XRD). From the alloy-interlayer model in the GIXR, the roughness of Al layer decreases with increasing thickness of Si barrier layers, while the roughness of Zr layer increases. Based on the XRD, the changing trends of crystal sizes of Al and Zr can explain the results in the GIXR. Comparing with the multilayers without Si barrier layers in the annealing process, the sample with Si barrier layer(0.6 nm) have better structural performance, of which the multilayers could have a stable structural performance above 300 ℃.
2015, 44(4): 1343-1348.
As a new type of spectroscopic devices, acousto-optic tunable filter(AOTF) has been widely used in spectral detection. Firstly, the dispersive principle and drive performance of AOTF were introduced, and some key performances of AOTF were discussed. Secondly, a set of analysis system for these performances was proposed. This system, with a monochromator as the light source, was based on multi-band acquisition, and was used to test the parameters of broad-spectral-range AOTF such as relation between driving frequency, diffraction efficiency and spectral resolution at different wavelength. The spectrum range covered from 400 nm to 3 200 nm. The intensity stability of light was better than 98%. The spectral resolution was less than 0.4 nm at 450 nm, 2.0 nm at 2 400 nm. Taking short-to-middle wave infrared AOTF as an example, the function and performance of the analysis system were verified finally, and the result shows the system suffices requirement of the design, and because of the high efficiency and convenience, the system has a high value for engineering application.
2015, 44(4): 1349-1353.
Ge/Si Separate-Absorption-Charge-Multiplication(SACM)-APD, as a new type of silicon APD, has become the focus of research. The device structure and its main parameters of Ge/Si SACM-APD(including quantum efficiency, responsivity, dark current, etc) were investigated in detail from the theory analysis and simulation. The simulation results show that the avalanche breakdown voltage is 25.7 V, the internal quantum efficiency is 90%, the maximum responsibility is up to 55 A/W when the gain is 1. The device is most sensitive in the spectral range of 750-1 500 nm. The peak wavelength of the APD is 1 050 nm. Under the condition of high bias and high light intensity, the electric field profile can be affected through the space charge of these electrons and holes.
2015, 44(4): 1354-1358.
Numerical simulations were performed on the photonic band gap (PBG) properties of the photonic crystal fibers(PCFs) possessing a clad with the cladding holes triangle-lattice distributed and a round fiber core using the full-vector plane-wave expansion method. Through the comparative analysis on the relationship of the PBG property and the structure parameters(cladding hole diameter dclh, cladding hole pitch and cladding hole filling ration f) between traditional(air-silica) and all-solid-state(nonair-silica) PCFs, a design of an all-solid-state PCF was given out which operates at the communication wavelength of 1 550 nm with the parameters dclh=1.0 m, =2.0 m and f=0.23 at the conditions of fiber core diameter dco=5.3 m and cladding hole material's refractive index nclh=1.65. Further numerical simulation shows that this resulting PCF has a gap width up to 43 nm.
2015, 44(4): 1359-1364.
The cracks of the road is a very important index to assess the quality of a road, since the different classes of the cracks are closely related to evaluate the dangerous degree of the road and the design of the repair strategy. Focusing on the common cracks including horizontal, vertical, block shape and chap cracks, a cracks classification method based on orientation and density characters was described. The main idea of the proposed method was to adopt the differences of the orientation and density distribution of the cracks to distinguish the different cracks. The orientation feature was first utilized to classify the direction cracks and non-direction cracks, and then by using the density feature to distinguish the block and the chap cracks. In order to check the effectiveness of the proposed method in this paper, using a large number of practical test data, by comparing with other algorithms, the results show that this proposed method has higher classification accuracy.
2015, 44(4): 1365-1369.
Dynamic random-dot stereograms which can eliminate the effects caused by psychological clues of stereo vision were used to study the depth motion characteristics of stereo vision. The effects on Stereo Visual Comfort(SVC) of the depth motion characteristics including motion positions, motion directions and motion velocities were analyzed by subject experiments and a prediction model of visual comfort and motion velocity during depth motion was built. The results show that depth motion induced perspective and depth motion make different visual comforts under crossed disparity(before the screen) or uncrossed disparity(after the screen) in dynamic random dot stereograms. The Pearson Correlation Coefficient(PCC) of three types of depth motion achieves 0.956, 0.972, 0.977, respectively, which indicates that the prediction model can more accurately predict the SVC.
The satellite attitude calculation method for linear CCD imaging the same region of non-uniform scene was presented, and a nonlinear relative radiometric calibration method based on histogram matching was put forward. Firstly, when it was needed to perform relative radiometric calibration task, the initial drift angle was calculated, according to which the yaw angle could be adjusted to ensure on-orbit satellite performing the calibration imaging mode. Secondly, in calibration imaging process the yaw angle was controlled to ensure all CCD detectors imaging the same region. Finally, after obtaining the same region image with CCD camera, histogram matching method was used to establish high-precision nonlinear relative radiometric calibration model. The simulation results show the magnitude and time interval of yaw angle adjustment with various attitudes, such as nadir imaging, roll attitude, pitch attitude, roll and pitch attitude, etc, and also analyze the error factors and the uncertainty of drift angle. This method needs neither the ground uniform scaling field, nor lots of on-orbit images for statistical analysis. More importantly, each track satellite images can meet the calibration condition, which avoids the unreliable problem of calibration source itself caused by the unstable of images between different tracks.
2015, 44(4): 1377-1381.
Cubature Kalman Filter(CKF) is one of new nonlinear filters, its accuracy and efficiency are better than Extended Kalman Filter(EKF) and Unscented Kalman Filter(UKF). But the traditional CKF was proposed based on third order cubature rule and the filter accuracy was restricted. So the spherical-radial cubature rule was expended from third order to fifth order, the fifth order cubature rule based on two kinds of cubature point was used, a new fifth order CKF was proposed. The restriction of traditional CKF in theoretic accuracy was improved by the new fifth order CKF. The simulation results of the maneuvering target tracking show the validity and feasibility.
2015, 44(4): 1382-1389.
The color provides much more information than the gray. Considering that the color facial image contains much more identification information than the gray facial image, the chroma Mahalanobis distance map was introduced into color face recognition. Based on the YCbCr color space, the information of chroma and brightness for one color facial image can be separated. Then Mahalanobis distance maps based on chroma information were constructed, at the same time, gray maps based on brightness information can be extracted by orignal color facial images. An algorithm for color face recognition using adaptive feature fusion based on chroma Mahalanobis distance map and gray map was presented. Based on energy values of wavelet packet sub-nodes, normalized feature vectors of chroma Mahalanobis distance maps and gray maps were constructed, respectively. Then identification feature vectors were constructed using several feature fusion methods, and fusion parameters were selected adaptively according to fusion effects. So feature complementation of chroma and brightness was achieved. Results of face recognition were obtained by the classifier based on the variance similarity degree. Experiments show that the algorithm has the characteristics of high recognition rate and good robustness.
2015, 44(4): 1390-1396.
Affected by global climate change, the permafrost in northeast high latitude permafrost area of our country was degraded significantly, and the water phase change seriously affected the mechanical indexes of soil during the thawing process of frozen soil. Due to the permafrost melting of high latitude permafrost regions in China in recent years, a plurality of freeway roadbed has landslide, and uneven subsidence and other geological disasters had repeated in the northern part of Heilongjiang Province. In order to study the island permafrost distribution, choosing the K153-K183 Road area from Bei'an to Heihe expressway as the study area, the 3 Landsat 7 ETM+ image data converging the study area was choosen respectively on March, May, September in 2009. The surface temperature map of the corresponding date was obtained and the relationship between ground temperature and NDVI, DEM was analyzed through the retrieval of the infrared surface temperature in the study area using the radiation transfer equation method. Then the map layer of the inversion results was classified using natural breakpoint classification. The distribution map of the low temperature area of the corresponding moment was obtained through the analysis and the artificial interpretation of the surface temperature change of the study area. Frozen soil distribution map was obtained in the study area in 2009 on the intersection operation of the low temperature zone. It had a good consistency comparing with the expressway permafrost investigation results from Bei'an to Heihe.
