2018 Vol. 47, No. 3
2018, 47(3): 302001.
doi: 10.3788/IRLA201847.0302001
Ghost Imaging Lidar via Sparsity Constraints (GISC Lidar),which belongs to a novel staring imaging Lidar mechanism, has been proven to be capable of high detective sensitivity, high resolution and high noise resistance. In order to promote GISC Lidar to practical application, the paper reviews the GISC Lidar mechanism and the recent research status of domestic and overseas, then highlights the core issues that GISC Lidar needs to solve in practical application and some recent achievements that the group has obtained. Finally, a simple outlook about the development trend of GISC Lidar has been prospected and discussed.
The applications, configure and technique developments of three main atmospheric environment observation targets(cloud-aerosol, wind field, and atmospheric molecule) were analyzed, and the characteristics and development trend of space-borne atmospheric environment observation lidar were summarized, based on the study of detection principle, technical system, system configure, application state, application scope and constraint condition, etc. Space-borne atmospheric environment observation lidar payloads should be designed according to scientific mission, application requirements and technical characteristics, using the advantages of space-borne lidar, and on the basis, the development trend and research focus of space-borne atmospheric environment observation technology and application were prospected.
2018, 47(3): 303001.
doi: 10.3788/IRLA201847.0303001
With the advantages of high sensitivity and carrying rich information, laser coherent detection technology has been used widely in military, mapping, communications and other fields. Coherent detection is developing rapidly in laser radar and laser communication applications, but it has not been carried out on a large scale in laser fuze. With coherent detection applied to laser fuze, the speed of targets can be obtained by detecting the laser Doppler signals, and the anti-interference ability of natural environment can be improved greatly by using the velocity difference between the target and the interference. A brief introduction of the principle and the characteristics of coherent detection was given, and then four kinds of coherent laser fuze system, the principle and system composition of a typical linear frequency modulation coherent laser fuze were discussed in detail. At present, coherent laser fuze was still in its infancy, which enhanced the system capabilities obviously and had a broad application prospects, and it deserved further study by relevant research institutes for expediting the engineering application process of coherent laser fuze.
2018, 47(3): 303002.
doi: 10.3788/IRLA201847.0303002
Aiming at the problem that air to air missile laser fuse is easily interfered by cloud, smoke and ground sea clutter, a laser gray imaging fuze technology for air to air missile was proposed. The push broom linear array detection method was used, which was progressive scanning gray imaging with the intersection motion of missile and target according to amplitude information of laser echo. The progressive target recognition algorithm was used to deal with the gray outline image accumulated by line to realize the precise detection of laser fuze, so its anti-interference ability can be improved. The test results of the prototype show that the scheme of the laser gray imaging fuze technology is feasible, the hardware realizability is high, and the image data obtained from the test can provide technical reserve for anti-jamming research of laser fuze.
2018, 47(3): 303003.
doi: 10.3788/IRLA201847.0303003
Aiming at the fragmentation dispersion characteristic of prefabricated fragment ammunition, fuze-warhead coordination was designed based on prefabricated fragment ammunition controlled by laser proximity fuze. Ideal warhead explosion height was obtained through formula deduction, Matlab software simulation and calculation of target damage at a equivalent area. Under this condition of the ideal explosion height, the laser fuze was designed through selecting appropriate laser beam detection field. Thus a optimal design of fuze-warhead coordination under specified conditions was completed. Results showed that:in the the range of 5 m of the missile dispersion, 60 pitch angle and 5 m3 m3 m command vehicle target, effective fragment density is the biggest at the warhead explosion 4-6 m height. Detection probability and height of the laser proximity fuze are analyzed and calculated at the height interval of the detonating height, the optimal beam emission angle of laser fuze is from 17 to 30. This design is of practical reference value for the application of the prefabricated fragment ammunition controlled by laser fuze.
2018, 47(3): 303004.
doi: 10.3788/IRLA201847.0303004
The laser fuze has advantages of strong anti-electromagnetic interference, high fixed angle and ranging precision, and small size. However, laser fuze's application isn't wide in air defense missiles because of the high false alarm rate. By analyzing the levels of signal feature extraction methods, the contributions of laser echo signal's features to anti-jamming performance and coordinated efficiency of fuze and warhead were discussed, including its energy, delay, pulse width, and information fusion. Then, based on an air defense missile's panoramic laser fuze, the target recognition algorithm was designed using linear array detector. The reliability of target detection is improved obviously, while the visibility of smoke coming down to 110 m, the laser fuze can still detect target exactly.
2018, 47(3): 303005.
doi: 10.3788/IRLA201847.0303005
To comprehensively evaluate the detection capability of the laser fixed-distance fuze, and obtain the variation in detection capability with the detection distance, the analytic equation of the distribution of pulsed laser ranging was established by deriving the echo equation of pulsed laser ranging, and an error quantification evaluation method was also proposed. The influence of detection distance on echo signal and the indicators of detection capability were analyzed and evaluated, and the results were verified by experiments. Results indicate that the detection of fuze is reliable within its reliable range. In addition, the random ranging error tends to initially decreases and then increases while the system error has the trend to increase gradually as the detection distance decrease. The maximum reliable range of fuze is 84.8 m and the random error is 0.22-0.73 m in the reliable range, thus satisfying the requirement of remote fixed-distance fuze. Besides, with the increase of the threshold, the range error can be obviously improved a lot, although the reliable range is caused to be reduced. The variation rules and evaluation methods in this work can provide a theoretical basis for the design and application of the pulsed laser fuze.
2018, 47(3): 310001.
doi: 10.3788/IRLA201847.0310001
In order to realize the error analysis of the bionic compound eye imaging system, a method of error analysis was introduced. The mathematical model was established. By finding the conversion matrix of the coordinate system, the transformation between the geodetic coordinate and the coordinate system with the subeye as the original point was realized. The equation of quantity relation between the rotation angle and the parameters of the bionic compound eye, that is, the measurement equation of the system, was derived. By using the method of function error, the measurement equation was transformed into an error function equation, and the error analysis was carried out. The experiment was set up, and the experimental data were collected. The feasibility of the analysis method was verified by comparing the calculated values with the actual measurement data. Theory calculated rotation angle systematic error is 3'14. Actual measured rotation angle error is 3'15. The calculated value of the theory is in agreement with the actual measured value, which proves that the error analysis method is feasible.
2018, 47(3): 310002.
doi: 10.3788/IRLA201847.0310002
As a special transflective focusing element, the lobster eye lens has important application value in the field of high energy such as X-ray, and in the visible light, infrared band has potential applications. Focused on improving the imaging quality of the lobster eye lens, the diffraction interference factor and the diffraction field of the variable periodic glare grating were discussed theoretically. The inner wall of the lobster eye channel was micro-formed by the variable periodic blazed gratings, and simulating the structure of one-dimensional lobster eye had been micro-formed. The simulation results show that the focal length is 100 mm, effective semi aperture 95 mm bores the existing structure in coke. The dispersion spot diameter at focal plane is reduced from 10 mm to 1 mm, the energy concentration increases from 75% to 89.62%, and the spot diameter and the concentration of light energy at the focal plane at different incident altitudes are both increased.
2018, 47(3): 306001.
doi: 10.3788/IRLA201847.0306001
Specific to synthetic aperture ladar(SAL), the impact of signal phase error on synthetic aperture imaging was analyzed. Laser signal was modeled, the impact of laser signal coherence on SAL azimuthal resolution was analyzed, one solution by delaying the local oscillator signal was proposed. The impact of nonlinear distortion in LFM signal on range resolution was analyzed. To solve the problem of the random initial phase error introduced in the process of laser LFM signal modulation and amplification, one nonlinear distortion and phase error calibration correction method based on reference channel was proposed. Experiment and simulation results are shown.
2018, 47(3): 306002.
doi: 10.3788/IRLA201847.0306002
Coherent Wind Lidar can obtain the atmospheric wind velocities through measuring the frequency shift of laser back from the atmospheric aerosol caused by Doppler effect. The scattered energy propagating back toward the receiver is very weak. So the frequency extraction from the weak signal belongs to the field of frequency estimation. The zero-padding Fast Fourier Transform(FFT) algorithm applied to the frequency extraction of the Coherent Wind Lidar has the advantage of algorithm simplicity, fast operation and high stability. Compared with the pulse-pair(PP) algorithm and the improved PP algorithm, zero-padding FFT algorithm was validated to have an obvious advantage in processing weak signal of Coherent Wind Lidar. In addition, the simulation with MATLAB shows that the measurable SNR of the weak signal can reach -26.6 dB by using the zero-padding FFT algorithm in the condition of 3 000 pulses non-coherent integration (128 samplings in one range gate). At last, the wind velocity test data gotten by the Coherent Wind Lidar was processed by improved PP algorithm and the zero-padding FFT algorithm, and through the processing results gotten by two algorithms, the advantage of zero-padding FFT algorithm is verified the advantage again.
2018, 47(3): 306003.
doi: 10.3788/IRLA201847.0306003
The bio-ceramic coatings containing low silicon was synthesized on TC4 titanium alloy pre-coated HA and SiO2 powder by laser cladding with continuous wave CO2 laser. Microstructure morphology, composition and phase distributions of the composite coating were investigated respectively by scanning electron microscopy(SEM), X-ray energy-dispersive spectroscopy(EDS), X-ray diffractometer(XRD). The bioactivity of coating was investigated preliminarily in the simulated body fluid(SBF). The corrosion behavior of the coating in the SBF was studied by the potentiodynamic scanning of electrochemical corrosion. The results show that the low silicon content bio-ceramic coating was well metallurgical bonded with TC4 titanium substrate. The corrosion potential of cladding layer was improved 84.4 mV compared with substrate in SBF, the corrosion current density decreased by about 6 times compared with base material, large amount of bone like apatite was deposited on the surface of the composite coating in SBF after seven days, which show well corrosion resistance and excellent biological activity.
2018, 47(3): 306004.
doi: 10.3788/IRLA201847.0306004
The optical nonlinear absorption and nonlinear refraction properties of CdTe and CdS quantum dots(QDs) were investigated by Top-hat Z-scan technique. The experimental condition of Top-hat Z-scan was at a wavelength of 532 nm and a pulse width of 190 fs. Under the the action of femtosecond laser pulses, the experimental results show that the nonlinear absorption of CdTe QDs is saturable absorption and the nonlinear absorption of CdS QDs behave as reverse saturable absorption. The nonlinear refraction of CdTe QDs self-defocusing, and CdS QDs show self-focusing. The nonlinear absorption coefficients of CdTe QDs and CdS QDs with dimensions of 2.6 nm and 2.4 nm are -9.2610-14 m/W, 0.7810-14 m/W, respectively, and the nonlinear refractive index coefficients are -0.8610-20 m2/W, 1.4610-20 m2/W, respectively, and the third-order nonlinear polarizabilities are 2.7210-15 esu and 1.3610-15 esu, respectively. It was shown that the optical nonlinear absorption and nonlinear refraction of cadmium semiconductor QDs with different materials under the similar sizes are different. Based on the experimental results, the mechanism was analyzed.
2018, 47(3): 306005.
doi: 10.3788/IRLA201847.0306005
Based on the welding characteristics of laser deep penetration welding, a three-dimensional transient thermal-flow coupling model of laser welding was established in the process when filler was melted into molten pool. The effect of filler metal filling mode on the three-dimensional shape of keyhole and the flow behavior of molten pool was studied. Finally, the influence mechanism of filler metal filling on keyhole stability was analyzed. The results show that filler metal in the form of a free transition into the molten pool had larger impact on the keyhole shape, causing the keyhole to close and collapse. The filler metal in the form of filling along the edge of the molten pool into the molten pool had relatively small impact on the keyhole shape, the keyhole bottom appeared concave phenomenon. After filler metal filled into the molten pool, two clockwise flow vortices were produced behind the keyhole wall, which made the flow behavior of the molten pool more complex.
2018, 47(3): 304001.
doi: 10.3788/IRLA201847.0304001
Establishing jamming effectiveness evaluation system of surface source infrared decoy was the key link of effectiveness evaluation. Considering the occasionality of experimental conditions and the economy of test cost, a simulation system was proposed. Firstly, the mathematical model of aircraft and missile was established, and the motion law and radiation factor were fully considered, and the algorithm optimization model was added. Secondly, the motion diffusion model and infrared image model of infrared decoy were established. The combustion optimization algorithm was used to improve the efficiency of the solution. Finally, the effectiveness evaluation index of interference was selected, and the rationality of the simulation system was verified by example simulation and comparison with the measured data. The simulation results show that the established effectiveness evaluation simulation system is feasible and effective, which is close to the experimental results, and meets the requirements of evaluating the effectiveness of the non-point source decoy jamming.
The surface structure of camouflage screen is mostly complex, and modeling calculation has high requirements for computing power. Surface structure disturbs the flow field around to influence the convection heat transfer and affects the surface temperature of the camouflage. In this paper, porous medium parameters of different values were attempted to ensure it had the same effect on the surface to get the simplification from the camouflage screen surface model to the porous medium model. Local modeling was established to analyze the influence of three typical camouflage screen surface structure on flow field around and its temperature field so that the corresponding porous medium wss found. The results show that this simplified method can greatly reduce the computational cost. This method can simulate the surface temperature of camouflage screen with large suface to evaluate the camouflage effect. The simplified model is used for outdoor bungalow situation. The infrared characteristics of outdoor bungalows and the ambient are simulated under natural conditions and the situation added and without camouflage simplified model respectively to analyze camouflage effect in day and night.
2018, 47(3): 304003.
doi: 10.3788/IRLA201847.0304003
In order to improve the fidelity of the IR hyperspectral target characteristic simulation, an influence model was presented in this paper to calculate the influence of the nearby building on the target final radiation at certain wavelength. A virtual experiment scene was constructed with 1976 U.S. standard atmosphere. Simulation experiments were done based on the constructed virtual scene in 3.0-5.0m at intervals of 0.01m, and the calculation results were compared with the target reflected solar radiation and the target self-radiation. Experiments results show that the radiation influence from the building are higher than the target reflected solar radiation or the target self-radiation at some waveband ranges, which means the radiation influence is the most critical radiation in some images of the image cube. It proves the influence model presented in this paper is necessary and important in hyperspectral simulation. Through the analysis of simulation results, the building surface temperature, atmosphere transmittance and the valid radiation area are determined to be the 3 key factors to affect the influence radiation of nearby building.
2018, 47(3): 304004.
doi: 10.3788/IRLA201847.0304004
The traditional three-dimensional guidance law generally divides three-dimensional space into vertical plane and horizontal plane respectively, which may lead to the lack of coupling information. It also doesn't take heat flux of infrared seeker and constraint of terminal velocity into account. To solve this problem, a guidance law based on the missile of adjustable thrust was proposed in the instantaneous rotary line-of-sight plane of rotary line-of-sight frame. The acceleration instruction in the direction of perpendicular to line-of-sight was designed to satisfy the criterion of motion camouflage strategy. Meanwhile, an overload instruction in the direction of line-of-sight was built with variable weighted change rate of heat flux limit and ideal overload which can satisfy the constraint of terminal velocity. Simulation results demonstrate that the designed guidance law has a good performance with the heat flux limit of infrared seeker, constraint of terminal velocity and available axial overload limit when attacking the high maneuvering target and initial misalignments of infrared seeker exists. The rate of line-of-sight is under 3 ()/s, so it has certain engineering application value.
2018, 47(3): 318001.
doi: 10.3788/IRLA201847.0318001
A model identification method based on the singular value decomposition and eigensystem realization algorithm(ERA) using Hankel matrix, was proposed for K mirror turntable of 2 m telescope to identify the model's order and parameters. Firstly, the plant was excited using the sweep signal and the position feedback signal was recorded, the test data were analyzed through the power spectrum density function to get the frequency response function of the system. Secondly, the singular value decomposition(SVD) was adopted to identify the Hankel matrix of the system to acquire the order model of the K mirror turntable. Finally, the ERA was adopted to identify the Hankel matrix to acquire the model parameters of the system. The experiment results show that the minimum order of the K mirror turntable is 6, the magnitude phase measurement accuracies of transfer function are 0.31 dB and 0.87 in middle frequency range respectively, compared with the hierarchical identification method, the identification accuracies are improved 50.7% and 23% separately. Results indicate that the proposed method can determinate a balanced and minimal order state-space representation equal to the system's dynamic performance, which is practical and effective in model order determination and parameter estimation.
2018, 47(3): 318002.
doi: 10.3788/IRLA201847.0318002
In order to ensure that the extreme ultraviolet camera can point the earth exactly, monitor and research 30.4 nm radiation generated by the earth plasmasphere roundly and chronically, the control system of pointing mechanism was designed and developed. Firstly, the structure and the operating principle of control system were introduced. Secondly, the key modules of control system were designed in detail. Then, a control algorithm based on Hall sensor positioning was presented. Finally, the error sources of control system were analyzed in detail. The results of calculated errors and the work on lunar indicate that the control algorithm based on Hall sensor positioning is correct and effective, the control error of pointing mechanism is no larger than 0.1 and satisfies the requirement of extreme ultraviolet camera technical indexes.
2018, 47(3): 321001.
doi: 10.3788/IRLA201847.0321001
Current commercial wide-angle infrared lenses usually adopt simple fixed-focus design structures and lack proper athermalized design. To improve the performance of current wide-angle infrared lenses, the design principle of zoom optical systems and the theorem of passive athermalization were utilized to develop an athermalized continuous zoom wide-angle infrared lens. The effective focal length of the proposed system was 10-24 mm(zoom ratio:2.4:1), the field of view(FOV) was 34-90, the operating wavelength was 8-12m, and the F number was 2.8. Considering the fact that infrared lenses were widely used in environments with large temperature variations, the proposed system was designed as a combination of six lens elements, including three fabricated with the chalcogenide glass of NBU-IR2(Ge20Sb15Se65) and three fabricated with conventional infrared materials such as germanium(Ge) and zinc sulfide(ZnS). By carefully allocating optical powers among the lens elements and properly controlling their air-spacing thicknesses, athermalization was realized by the proposed system design, in addition to the performance of continuous optical zoom. Simulation results show that the proposed system can produce thermal images with a close-to-diffraction-limit performance for the temperature range of -40 to 60℃. The Modulation Transfer Functions(MTFs) of the system are higher than 0.25 for the entire FOV. The system also has a compact/light-weight structure that only includes one aspheric surface on a chalcogenide glass lens element. Modern precision molding technique can be used to fabricate aspheric surfaces on chalcogenide glasses so that the fabrication costs of the proposed system can be controlled. The overall system design is suitable for the application of vehicle night vision.
2018, 47(3): 321002.
doi: 10.3788/IRLA201847.0321002
To study the impact of the polymorphic biological particles on the electromagnetic equipment such as target detection, the artificially prepared flocculent biological particles were equivalent to bullet rosette particles. Then the biological particles with different number and length of branches were built, and the discrete dipole approximation(DDA) method was used to calculate the extinction efficiency factor for biological particles. The results show that the structures of biological particles have great impact on the broadband extinction performance. The extinction performance of biological particles is positively correlated to the number and length of branches in the far infrared waveband and is positively correlated to its length of branches but independent of its number of branches in the millimeter waveband. Based on studying the relationship of extinction efficiency factor with the number and length of branches, the biological particles average extinction efficiency factor in the far infrared waveband was constructed. The model provides a reference for the further extinction performance study and morphology control of biological particles.
2018, 47(3): 321003.
doi: 10.3788/IRLA201847.0321003
Aiming at current conditions and shortages of laboratory dynamic experiment of extinction materials, test device and method, which was used to test composite extinction performance of biological materials in ultraviolet and infrared band, was presented based on single optical path. The device mentioned above was designed and made, transmittance of ultraviolet and infrared band, and mass concentration of self-made biological materials smoke in the smoke box were respectively 29.597%, 14.514%, and 0.389 g/m3. Average mass extinction coefficient of biological material in ultraviolet and infrared band were respectively 0.794 75 m2/g, 1.241 59 m2/g based on data processing system. Experimental result shows that the designed device is used to test composite extinction performance of biological materials in ultraviolet and infrared band based on single optical path successfully, and enriches test methods of multiband extinction performance of biological materials further.
2018, 47(3): 321004.
doi: 10.3788/IRLA201847.0321004
The effect of annealing in atmospheric environment on Ta2O5 thin films was researched, which were prepared by ion beam sputtering. The annealing temperatures ranged from 150℃ to 550℃, and the interval was 200℃. The optical band gap (1-4 eV) of the Ta2O5 thin film was characterized by the Cody-Lorentz dielectric model. And the microstructure vibration was characterized by the oscillator model in the range of infrared region(400-4 000 cm-1). The results show that the turning point of the annealing temperature appeared between 150℃ and 350℃. The extinction coefficient of the thin film increased when the annealing temperature was above the turning point. The variation of Urbach energy was in accordance with the extinction coefficient, but the variation of band gap was opposite. By analyzing the microstructure vibration in infrared, it's found that the stoichiometry defect of the protoxide was in the Ta2O5 films.
In order to study the characteristics of aerosol size distribution and complex refractive index in typical areas of China, the atmospheric aerosol was measured by using various equipments like aethalometres, visibility meters, integrating nephelometers and optical particle counter(OPC). The effective complex refractive index based on Mie scattering theory was calculated. Then, the aerosol size distribution was retrieved from the observation, and the relation between extinction and absorption coefficient with respect to wavelength was also analyzed in these typical areas. It shows that the mean values of real part of refractive index nr in these area are all around 1.5, while the imaginary parts ni are 0.01, 0.017, 0.016 and 0.008 in Xinjiang, Tianjin, Hefei and Xiamen, respectively. The number size distribution can be described by Junge size distribution in Xinjiang, while it can be described by both Junge size distribution and lognormal distribution in Tianjin, Hefei and Xiamen. The relation between extinction and absorption characteristics of aerosol and wavelength was described. The results are important for research on the climatic effects of aerosols.
2018, 47(3): 311002.
doi: 10.3788/IRLA201847.0311002
The effectiveness of polarization navigation depends heavily on the ability to derive effective all-sky polarization distribution information from different atmospheric conditions. Based on the simulation of vectorial atmospheric transport equation, the properties of all-sky distribution of degree and angle of polarization under cloudless clear and turbid atmosphere were analyzed, and the effects of different atmospheric turbidity, solar orientation, observed altitude and observed band on the polarization distribution were studied, and then the effectiveness of polarization navigation under different atmospheric conditions was discussed. The results show that the solar orientation determines the overall pattern of the all-sky polarization information. The turbid atmosphere has obvious influence on the polarization information of the near ground. When the whole layer of the optical thickness increases to more than 2, the degree of polarization will be reduced to below 0.1, in this case, the detection of the polarization information becomes more difficult, and not conducive to the navigation. While the middle and upper atmosphere dominated by clear skies are less affected by turbid atmosphere, the distribution of polarization information is stable and in accordance with the distribution of Rayleigh single scattering, which can ensure the effectiveness of navigation during the daytime. And the long waveband is more suitable as the observation band for polarization navigation within the limits of visible band under cloudless clear atmosphere.
2018, 47(3): 317001.
doi: 10.3788/IRLA201847.0317001
To solve the line-of-sight problem when using multi-linear CCD cameras in large equipment(such as aerospace field) measuring process, a novel monocular 3D coordinate measurement method based on orthogonal cylindrical imaging was proposed. The system consisted of an orthogonal cylindrical imaging camera and an optical target. The measurement could be finished without multi-cameras intersection by using space resection. Measurement principle of orthogonal cylindrical imaging camera and intrinsic parameter calibration were analyzed. Structure parameter and calibration of optical target were designed. Measuring method with orthogonal cylindrical imaging camera and optical target was emphatically studied. Mathematical model of coordinate calculation was derived. In a 1 000 mm1 000 mm1 000 mm measurement volume that was 3 m away from the camera, the distance measurement accuracy of the proposed method was respectively better than 0.4 mm and 0.7 mm in the horizontal, height and depth direction. For coordinate measurement, the accuracy was better than 0.5 mm. Experimental results showed that the method was feasible and valid with good accuracy.
2018, 47(3): 317002.
doi: 10.3788/IRLA201847.0317002
The ground-based SAR, as a new type of ground remote sensing technology, is widely used in the field of microdeformation monitoring because of its high precision, all-weather, flexible and real-time continuous observation. Based on the deep research on the key technical problems of micro-deformation monitoring of ground-based SAR, combined with the characteristics of foundation pit monitoring, the method of weighted median filter denoising was used to improve the signal-to-noise ratio of interferogram and weaken the noise phase difference. The method of atmospheric correction based on the PSC network was proposed to reduce the impact of meteorological disturbances and weaken the atmospheric phase difference. The improved methods were applied to the foundation pit monitoring experiment. The experimental results show that the weighted median filter and PSC network weather correction effectively weaken the phase change caused by noise and atmospheric, and achieve monitoring accruacy of submillimeter. In order to verify the accuracy of ground-based SAR monitoring, the synchronous observation is carried out using high-precision total station, the monitoring results are consistent with the results of ground-based SAR, which verifies the reliability and feasibility of ground-based SAR technique in monitoring the microdeformation of pits.
2018, 47(3): 317003.
doi: 10.3788/IRLA201847.0317003
Driven by the increasing demands of the general purpose in computation and image display, Graphics Processing Unit(GPU) has been developed and used in many fields, such as medical field, scientific calculations, image processing etc.. But, its application in 3D shape measurement is still a beginning. In this paper, two 3D shape measurement systems based on Fourier Transform Profilometry(FTP) and tri-frequency heterodyne method were implemented with Compute Unified Device Architecture(CUDA) technology to speed up their 3D shape construction of a measured static or dynamic object. In the first 3D shape measuring system based on tri-frequency heterodyne method, a high-speed digital projection module and a synchronously triggered camera were used to record 12 deformed fringe images on the surface of a small object. The experimental result demonstrates that the efficiency of the unwrapping phase calculation by GPU is improved 2 089 times than that of CPU for doing same task on 12 images with 1 360 pixel1 024 pixel each. In the second system based on FTP, only one deformed fringe image was recorded by a camera, then transferred into GPU and processed by the programmed CUDA algorithm to restore the corresponding 3D shape. Compared with the traditional processing method by CPU, the time consumption of FTP method completed by GPU is shortened 27 times for a 1 024 pixel1 280 pixel image.
2018, 47(3): 317004.
doi: 10.3788/IRLA201847.0317004
In the high precision pulse laser ranging system based on sine wave, due to the factor of high frequency signal crosstalk, or electronic and optical devices with nonlinear and other factors, which would cause pulse time-of-flight periodic error, the range accuracy is reduced. The method of calculating the timing error by using the measuring data of the range finder in a certain distance was presented. An error compensation function curve was constructed by least square fitting, this curve was discretized in a sinusoidal reference period, the discrete data was stored into the single chip. In the distance measurement, the error compensation function curve was used as the reference, the compensation of pulsed time-of-flight periodic error was realized. The method had the advantages of simple principle, reliable data, convenient operation and so on. After the error compensation of the laser pulse measurement, the distance error is within 3 mm.
2018, 47(3): 317005.
doi: 10.3788/IRLA201847.0317005
According to the factors of velocity disturbance of the carrier and measurement noise that affected control accuracy of the photoelectric platform, two control strategies of active disturbance rejection control(ADRC) and filtering control were designed. Firstly, the law of disturbance in the mathematical model of velocity stabilized loop of servo control system for the photoelectric platform was analyzed, the disturbances equivalent was made and the notion of general disturbances was proposed, and then the ADRC controller based on reduced-order extended state observer(ESO) was designed. Furthermore, Kalman filter was used to process the measurement noise in the system, thus the error of estimation of the ESO was reduced. Finally, was conducted thoroughly the contrast tests between the traditional PI control system with the Kalman-ADRC control system designed in this paper. The experimental results demonstrate that, with the same designed bandwidth, the stabilization time of step response of the Kalman-ADRC control system is reduced by 32.53% and the overshoot amplitude is reduced by 72.73% compared with the PI control system; when using swing table to introduce a sinusoidal disturbance with an amplitude of 1 and a frequency of less than 2.5 Hz, the disturbance isolation degree of the Kalman-ADRC control system gains an increase of 54.67%compared with the PI control system; when the parameters of the system model varied within the range of 15%, the Kalman-ADRC control system still has an excellent performance in disturbance isolation degree, presenting strong robustness. It is thus concluded that the Kalman-ADRC control system can meet the boresight stabilized performance requirements of the photoelectric platform, and has great practical value in improving the accuracy of boresight stabilization.
2018, 47(3): 320001.
doi: 10.3788/IRLA201847.0320001
Terahertz technologies are believed to find various applications such as security screening, medical imaging, nondestructive inspection etc. For high speed, high sensitivity, and portable terahertz imaging applications, Terahertz Focal Plane Arrays(THz-FPAs) were designed and demonstrated based on self-mixing mechanism in AlGaN/GaN high-electron-mobility transistors (HEMT). The THz-FPAs with an array size of 3232 were realized by flip-chip bonding a detector array and a readout integrated circuit(ROIC) based on silicon CMOS technology. Each pixel detector consisted of two HEMTs which were configured in a differential output scheme so as to enhance the voltage responsivity, reject the common-mode voltage noise, and increase the sensitivity. The differential detector signals were amplified in the ROIC and converted to digital data by an Analog-to-Digital Converter(ADC) in a printed-circuit board(PCB) which also hosted a Field-Programmable Gate Array (FPGA) for data acquisition and conversion. The data converted into a video stream was sent to a personal computer through the Camera Link interface. The focal plane array was used to demonstrate imaging of terahertz beam spot, terahertz interference ring pattern, and a rotating plastic blade under terahertz illumination all with a frame rate up to 30 Hz.
2018, 47(3): 320002.
doi: 10.3788/IRLA201847.0320002
Multi-band filter is the key component of the detector of space optical-remote-sensing camera. It was used for multispectral band-pass filtering and the encapsulation of detector. Because of the complicate feature sizes and films, the designing and environment adaptability assessment of multi-band filter were more complicated than the panchromatic or monochromatic filter. Physical dimension of filter substrate, filter window size, on-die pixel-location-symbol window size and on-filter alignment mark were the feature sizes of a multi-band filter, whose designing and calculating method for these feature sizes were given. Influences of designing or manufacturing error of the multi-band filter were also analysed, such as filter-and-die alignment precision, detector butting precision on focal plane assembly, and spectral response characteristic of camera system. An environmental assessment method for multi-band filter was also proposed, and the assessment method was based on the existing environment adaptability assessment standard for spacecraft. Finally an application example of multi-band filter designing and environmental assessment from some space camera was given.
2018, 47(3): 320003.
doi: 10.3788/IRLA201847.0320003
Correlated double sampling is an indispensable processing technique for CCD signal conditioning. It can effectively reduce the reset noise. The double sampling clock phases are critical parameters determining correlected double sampling(CDS) technique's effectiveness. To automatically determine the CDS clock phases, a pseudo-contrast based method was proposed. Through globally searching the maximum of the pseudo-contrast function by changing the signal sampling location and the reset sampling location in a fixed scene imaging set-up, the CDS clock phases could be determined automatically. Principle of the method was explained in detail. A test bench system was designed to verify the proposed methods. Experimental results show the effectiveness of the proposed method with an uncertainty about 3%, the robustness to different light intensities and better SNR performance compared to the conventional method.
2018, 47(3): 320004.
doi: 10.3788/IRLA201847.0320004
A scattering model of the optical component substrate under different levels of defects has been established based on Mie scattering theory, and then the scattering characteristics of the replication of substrate defect have been analyzed quantitatively when the particle contamination exists on the surface of the optical component. On this basis, a R-C optical system has been taken as an example, and stray radiation characteristics of the system have been simulated and analyzed by using the ASAP optical analysis software for the case of the primary mirror substrate under different levels of defects. Furthermore, according to the calculation method of the signal to noise ratio(SNR), the SNR of the system has also been carried out and analyzed. The results indicate that the SNR of the system decreases with the increasing of the defect levels of primary mirror substrate for a given radiant temperature of the sky background, and the influence of the SNR decreases with the increasing of the radiant temperature of the sky background for a fixed defect level of primary mirror substrate. Finally, for the primary mirror particle contamination of 300 grades (the particle surface coverage is 0.03%) and its substrate defect levels under five cases such as I-10, I-20, I-30, Ⅱ and Ⅲ, the relative SNR(relative to the ideal primary mirror) of the system are 0.932, 0.920, 0.906, 0.832 and 0.807, respectively when the radiant temperature of the sky background is 200 K. Thus, when the optical properties of components become worse, the levels of optical component defects should be strictly controlled within Ⅱ level to ensure the effective detection of the weak signal with low SNR.
2018, 47(3): 326001.
doi: 10.3788/IRLA201847.0326001
The CSK algorithm was used to extract a least square classification of moving objects from image fragments in this paper, and the multichannel color features was introduced to calibrate the moving objects. Through the cyclic hypothesis of periodicity of the kernel function in the current image fragments, the CSK algorithm was applied to compensate the lack of target gray-level features describing capacity with CSK algorithm in some extent. The PCA was used to reduce the feature dimension, remove feature redundant information, improve the updating speed of classifier parameters. The problem of moving target tracking could be solved when CSK algorithm classifier parameters were updated linearly and could not adapt to large changes of target. Experiments were performed on the algorithm dataset of the benchmark test platform and the dataset of test data. The experimental results of target color kernel tracking algorithm (TCKCT) show that the algorithm has a better tracking effect in the case of the illumination changing, the background clutter, the target deformation existing, the target moving velocity is faster and the target motion amplitude is larger. The experimental results of UAV tracking remote control car further verify the characteristics of TCKCT algorithm and good real-time performance can meet the target tracking requirements of UAV. It has a good practical application prospect.
2018, 47(3): 326002.
doi: 10.3788/IRLA201847.0326002
In order to obtain more characteristic information of optical targets and achieve the goal of target recognition, the scintillation of target echo was considered as one of the means of target recognition by utilizing the difference of modulation characteristics of different target echoes in turbulent atmosphere. The random phase screen was used to generate round trip atmospheric turbulence by power spectrum inversion, using hard edged apertures to expand into finite series sum forms and Collins diffraction integral formula, the complex amplitude distribution of the reflected light of corner reflector, lens and reflector of Lambertian diffuse target was derived. The influence of turbulence intensity and target size on the scintillation index of the three target echoes was analyzed and verified by experiments. The results show that the scintillation index of optical target and diffuse reflection echo have obvious differences, the overall difference is an order of magnitude. With the increase of diameter, optical target echo scintillation index shows a decreasing trend on the whole; The scintillation index of corner reflector and lens target echoes in the numerical difference is not obvious, but the method of plotting the echo scintillation index over time by multiple test results can be used to distinguish the two roughly. This method can quickly identify the optical target from the diffuse background, and also provide a reference value for the classification and recognition of the optical object.
