2019 Vol. 48, No. 10
2019, 48(10): 1002001.
doi: 10.3788/IRLA201948.1002001
As a kind of smart surface, metasurfaces are usually composed of sub-wavelength nano-antenna arrays which are specially designed and processed with characteristic sizes close to or less than their working wavelengths. Metasurfaces can arbitrarily modulate the amplitude, phase and polarization of the light field. It has the advantages of ultra-thinness, ultra-small pixels, broadband, low loss, easy processing, flexible design and great functionality. This paper reviews the research progress of metasurfaces in holographic display, wavefront modulation and polarization conversion, active tunable, nonlinear wavefront modulation, and looks forward to the future development trend of metasurfaces. As an ultra-thin and miniaturized wavefront modulation device, metasurfaces have great information capacity and are more suitable for the future development of highly integrated micro optoelectronic systems. Metasurfaces provide potential feasibility and new perspectives for a plethora of applications such as holographic display, beam shaping, vortex beam generation, data storage, encryption and anti-counterfeiting, metalens and dispersion control, color printing, asymmetric transmission, nonlinear optics, the spin-Hall effect of light, optical communication, integrated optoelectronics. They are expected to replace the traditional optoelectronic devices and show broad prospects for future development.
2019, 48(10): 1004001.
doi: 10.3788/IRLA201948.1004001
The Vacuum Infrared Hyperspectral Radiance Temperature Standard Facility for Infrared Hyperspectral radiance calibration was established at National Institute of Metrology for calibrating the radiance temperature of infrared remote sensing payloads. The state-of-the art of the system was introduced, such as, the structure, the new designed standard blackbody, the calibration method and the traceability. The vacuum reduced background chamber was built for the customer blackbodies. The standard blackbodies, including the variable temperature blackbodies and the fixed-point blackbodies, were designed. The radiance temperature of the customer blackbodies were calibrated by the standard blackbodies through a Fourier transform infrared spectrometer. The temperature range of the new designed standard blackbody was from 125 K to 500 K with a 30 mm in diameter and 0.999 7 emissivity of the cavity. The radiance temperature standard uncertainty of the blackbody was better than 0.026 K@300 K/10 m. The fixed point blackbodies included a mercury blackbody, a gallium blackbody and an Indium blackbody. The cavities diameter were all 25 mm, and the uncertainty of the fixed blackbodies was better than 0.020 K@300 K. The system could support the requirements of lots of infrared remote sensing payloads. This facility can provide the radiance temperature tracebility for most infrared remote sounders with low uncertanty, high sprectral resolution and strong extensibility.
2019, 48(10): 1004002.
doi: 10.3788/IRLA201948.1004002
In order to study the effect of the ratio of oxidant to reducing agent on the performance of trilead tetraoxide/Mg/teflon mixed powder(Pb3O4/Mg/PTFE), keeping the formula of oxidant and changing the ratio of oxidant to reducing agent, 5 different formulations were designed. The uniformly mixed powder was compressed into a cylinder with a tablet press. The 7.5-14 m thermal imager was used to observe the combustion process of the tablet, and the burning time, mass burning rate, radiation area, radiation, and radiation intensity of each sample were obtained. The results show that with the increase of the proportion of reducing agent, the mass burning rate first increases and then decreases. When the ratio of oxidant to reducing agent is 1:1, the maximum mass burning rate is 5.03 g/s. The temperature of the flame increases with the proportion of reducing agent first and then decreases. When the ratio of oxidant to reducing agent is 1:2, the maximum temperature of the flame reaches a minimum of 754.29℃. With the increase of proportion of the reducing agent, the radiance grows first and then drops. When the ratio of oxidant and reducing agent is 1:1, the radiance reaches the maximum of 1 869.21 Wm-2sr-1. The radiation intensity reaches the maximum of 97.61 Wsr-1. Visible in the 7.5-14 m band, when the ratio of oxidant and reducing agent is 1:1, the radiation characteristics of the sample is best.
2019, 48(10): 1004003.
doi: 10.3788/IRLA201948.1004003
HgCdTe FPA pixel performance of high-reliability and long-life is worse, degraded and failed over time in service life. To determine its storage life, the test time should be shortened by class B test, the constant stress of ALT or ADT should be greater than that of high temperature +90℃,2 160 h. The high acceleration stress screening test HASS should be forced to develop the defect to expose the possible early failure before the quantitative acceleration test. According to the high temperature storage test performance degradation test data of the HgCdTe FPA Dewar assembly, the statistical model was used to convert the failure time or performance parameter degradation characteristics. The storage life was greater than 50 years under rated stress level st +25℃. More than 3 000 h the high temperature storage test results show that the pixel performance tends to be better before 1 500 h because residual technological stress is released. Baking for 20 days in a vacuum environment of high temperature +80℃ does not cause deterioration of pixel performance.
2019, 48(10): 1004004.
doi: 10.3788/IRLA201948.1004004
Evaluation of infrared stealth effectiveness of aircraft imaging targets was important for the development of aircraft's infrared stealth technology and operations of stealth and anti-stealth. An evaluation method for infrared stealth effect of aircraft imaging target was proposed, which was based on the principles of imaging detector and the characteristics of each stage of image processing. The evaluation indexes of aircraft's infrared stealth effectiveness as imaging target which can reflect the influence of background and decoy jamming were established based on multiple infrared image features. Then, the simulation model of infrared imaging detector was established, and the rationality of the evaluation indexes was verified. Finally, based on the evaluation indicators, the effectiveness of different stealth techniques and the application of decoy jamming on the stealth effectiveness of the aircraft were evaluated. The results have instructive meanings for aircraft's infrared stealth and anti-stealth.
2019, 48(10): 1005001.
doi: 10.3788/IRLA201948.1005001
By optimizing the PI controller parameter tuning method of the motor that drives the grating, the positioning accuracy and stability of the servo motor were enhanced, and the line selection output of the single-path tunable TEA CO2 laser was improved and the tuning interval was shortened. The frequency domain model of the method of Permanent Magnet Synchronous Motor (PMSM) was deduced by the parameter. The analytical expression of the servo three-loop Proportional Integral (PI) was derived and set according to the actual requirements of the project. The PML40-530B8ANL AC direct drive motor and G-POLHOR10P100EE-E0 drive were used to build the optical path experimental device to verify the above parameters. The overshoot of the turntable positioning system is 4.86%, and the adjustment interval is 19.5 ms. Based on the turntable system, a fast-tuning TEA CO2 laser was built, and the laser weak line energy stability experiment was carried out during a tuning interval of 20 ms. The single pulse energy of the 9P(44) line is 74 mJ, the energy fluctuation range is 3.35%, and the energy stability was increased by 3.62 times.
2019, 48(10): 1005002.
doi: 10.3788/IRLA201948.1005002
In order to realize the long distance transmission of discharge initiated repetitive-pulsed HF laser, and produce a high quality laser of large volume in the shorter resonant cavity, the structural design, simulation calculation and experimental study of the passive branch confocal unstable resonant cavity were carried out. The simulation results show that with the increase of the magnification M, the energy of far-field light focal spot was gradually increased with the increase of magnification, and the energy transferred to the light spot center. In addition, the light spot size and the divergence angle of far-field were gradually decreased as well. The experimental results show that with the increase of the magnification M, the variation of the far-field intensity distribution, the light spot size and the divergence angle were consistent with the simulation results. But the output laser energy actually increases first and then decreases. Considering the requirements of high beam quality and high energy, in the case of normal flow field, the far-field divergence angle of repetitive-pulsed HF laser was 2.37 times diffraction limit magnification when M was 3, and the laser energy was slightly lower than the stable resonant cavity(about 94.6% of stable resonant cavity), which satisfies the requirements of long distance transmission.
2019, 48(10): 1005003.
doi: 10.3788/IRLA201948.1005003
To insure that a high peak power ultraviolet laser pulse of the short pulse XeCl excimer laser system was obtained, experimental study on laser output characteristic of the compact XeCl excimer laser by pumped electron-beam form four directions was carried out. Via varieties of total pressure and component molar rate of gas mixtures in laser chamber, charge voltage of laser and thickness of titanium foil utilized as the anode, effects of them on pulse energy were showed. With the result that the optimal operation condition for the compact XeCl excimer laser by pumped electron-beam was discovered, the energy of the laser pulse of about 200 ns duration at half-amplitude exceeded 100 J under the optimal operation condition,and the electro-optical efficiency was about 5.81. In addition, the pulse jitter of the compact XeCl excimer laser was experimentally researched, and the pulse jitter was little 20 ns. Researches show that a little 20 ns pulse jitter and 103 J high energy ultraviolet laser pulse of the compact XeCl excimer laser by pumped electron-beam is obtained, and the result may be meeting demands of the short pulse XeCl excimer laser system.
2019, 48(10): 1005004.
doi: 10.3788/IRLA201948.1005004
In the seeker gate, whether the guidance signal can enter and whether the high-frequency interference is advanced is a probability problem. The probabilistic analysis method was used to discuss the probability (guidance probability) of the guided laser entering the gate and the probability (advance probability) of the first pulse of the high-frequency laser leading the guided laser. By studying the relationship between the guidance probability and the standard deviation of the laser light extraction time (standard deviation of laser timing) and the relationship between the guidance probability and the gate width, it was concluded that when the gate width was 6.18 times the standard deviation of the laser timing, the guided laser can be considered to completely enter the seeker gate. Based on the guidance probability, the relationship between the advance probability and the number of high-frequency pulses in the gate was obtained; the relationship between the advance probability and the gate width at different high-frequency laser frequencies was gained. When there were 4 high-frequency pulses in the gate, the advance probability was 98.21%. Therefore, from the laser guidance, the seeker gate width can be selected according to the standard deviation of laser timing to achieve accurate guidance; from the high-frequency interference effect, the high-frequency interference frequency can be determined according to the seeker gate width to achieve effective interference.
2019, 48(10): 1005005.
doi: 10.3788/IRLA201948.1005005
The random moving and jitter of the target rotation center will lead to the projection center mismatch in the process of laser reflection tomography. The phase retrieval algorithm was employed to reconstruct the fault image. The phase errors caused by random motion by repeated intensity iteration was eliminated to reduce reconstruction error and restore target image. Aiming at the slow convergence speed and poor accuracy of G-S algorithm,the modulus weighting algorithm was provided to restore projection data. The simulation experiments show that the convergence speed and convergence accuracy of the algorithm are increased by more than 1.2 times. The mean square error of the three sets of reconstructed images in the simulation experiments is reduced from 2.487 5 to 0.792 7. The target image contour also be sharper by the method. The field experiments show that the image reconstruction artifact can be effectively eliminated and the imaging quality of the laser reflective tomography system is improved.
2019, 48(10): 1005006.
doi: 10.3788/IRLA201948.1005006
In order to study the spectral characteristics of heavy metal plasma in the atmosphere near an industrial zone in Shenyang, double pulse laser-induced breakdown spectroscopy (DP-LIBS) was used to measure and analyze the characteristics of main heavy metal laser-induced breakdown spectra in the atmosphere. By comparing the plasma spectrum of samples excited by single pulse (SP) and double pulse (DP). It was found that DP-LIBS can enhance the intensity of plasma spectrum. The DP-LIBS spectral intensity with the interval time of two pulsed lasers was studied, and the maximum enhancement of the heavy metal plasma spectrum was obtained when the pulse interval was 15 s. At the same time, the DP-LIBSs technology will also improve the stability of the sample plasma spectrum, and the relative standard deviation of the spectrum line will be reduced from 6% to about 3%. Finally, the changes of electron temperature and electron density with the time interval of double pulse were studied.
2019, 48(10): 1005007.
doi: 10.3788/IRLA201948.1005007
Coherent beam combining (CBC) of fiber laser array can improve the total output laser power while maintaining good beam quality, thus improving the laser brightness. CBC of fiber laser array has been a research hotspot in the field of laser technology and has attracted much attention. At present, lots of CBC experiments have been successfully established and verified in the laboratory. However, there is few long distance propagation experiment carried out in real turbulent atmospheric environment. The ability of compensating the phase distortions introduced by the turbulent atmosphere still needs to be tested and verified experimentally. The target-in-the-loop technique is an important and useful method to realize the coherent combining of array beams at the target surface in a real long-distance turbulent atmospheric environment. CBC of fiber lasers based on target-in-the-loop technique becomes a key goal and an important research direction since it has been proposed. Based on the adaptive fiber collimator array and conformal projection system, a target-in-the-loop CBC system of six fiber amplifiers was established, which successfully compensated the phase distortions and realized CBC at the target surface through a kilometer-scale propagation distance with atmospheric turbulence.
2019, 48(10): 1005008.
doi: 10.3788/IRLA201948.1005008
Aiming at the problem of error in single Lidar detection of horizontal wind field in civil aviation airport area, a support vector regression based model for estimating horizontal wind field of double Lidars was proposed. The model was based on the wind speed of two Lidars overlapping scanning regions, and the horizontal wind speed at the intersection points was used to estimate the horizontal wind speed of other data points in the radial direction. Firstly, the three characteristics of radial wind speed, horizontal wind speed and distance in the overlapping area were extracted. The overlapping area data points were used as the training set. After the same dimension was normalized, the penalty factor and kernel function parameters were set, and the initial estimated value was obtained by support vector regression. Then, the radial wind speed of the single Lidar was used as the a priori condition to estimate the horizontal wind speed of the adjacent radial points in the non-overlapping area. Then, the radial wind speed of the single Lidar was used as the a priori condition to estimate the horizontal wind speed of the adjacent radial points in the non-overlapping area. The estimated results were extended to a new training set, and the training set was gradually expanded to estimate the horizontal wind speed in the non-overlapping area. Finally, the error of the stepwise estimation of the method was analyzed by the measured data. The influence of wind speed and echo signal-to-noise ratio on the estimation performance of the method was analyzed. The results show that the root mean square error of the wind field estimated by the method is better than that of the single radar. The method expands the range of the horizontal wind field detected by the dual Lidars and improves the utilization of the Lidars.
2019, 48(10): 1005009.
doi: 10.3788/IRLA201948.1005009
The waveform decomposition method of Lidar pulse signal is an important way to extract the waveform parameters, which provides significant data sources for retrieving the elevation, slope, roughness and reflectance of target. A waveform decomposition algorithm on variable component parameter random sampling method (WDVCM) was proposed to process waveforms with poor SNR and certain overlapping. The algorithm regarded the compounded Gaussian function as the optimization model, and achieved the decomposition and extraction of raw waveforms by generating randomly characteristic parameters and deleting or creating Gaussian component, based on the energy function and the standard deviation of fitting as the criterion for parameter optimization. About 4584 raw waveforms in a stripe of Geoscience Laser Altimeter System (GLAS) developed by National Aeronautics and Space Administration (NASA) were processed using the WDVCM. The result indicates that proportions of fitting waveforms originated from WDVCM and NASA with correlation coefficient over 0.95 are 99% and 97% respectively. Wherein, the ratio with the differences of correlation coefficient less than 0.05 is about 98%. The averages of standard deviation coefficient (SDC) of fitting waveforms provided by WDVCM and the NASA are 2.21 and 3.28, and about 89% of SDC of fitting waveforms processed by WDVCM is less than that from NASA. It proves that the WDVCM is more applicable for decomposing overlapping waveforms with better fitting effect.
2019, 48(10): 1005010.
doi: 10.3788/IRLA201948.1005010
Laser absorbers are necessary for high power laser facilities to achieve effective control of the stray lights. However, the boundaries of the absorber light receiving surfaces are easily to be damaged by the laser, which may cause the pollution of the clean environment inside the facility. To solve this problem, based on methods of finite element analysis, light field distribution in medium of high-power laser absorber with its boundary of light receiving surface under conditions of no-transition, plan transition and curved surface transition were simulated. Effects of absorption glass boundary on light field were analyzed. Transformation regularity of the intensity and position of light field peak inside the medium were obtained. The results indicate that the damage of the absorber may be caused by the curved surface transition of the boundary. This research provides a reference for research of laser damage and absorber designing.
2019, 48(10): 1005011.
doi: 10.3788/IRLA201948.1005011
Based on the principles of optical imaging and the method of triangular laser ranging, a method was proposed to measure the distance of an underwater target by three point laser sources and underwater camera. Theoretical models were built for the cases when the target was perpendicular to the laser beams, when there was a rotation angle and a pitching angle between the target and the laser beams. Mathematical relationships was established between underwater distance and geometric parameters of the laser spot pattern in the underwater image. Based on theoretical models, formulas for distance calibration were deduced. To verify the feasibility and accuracy of the proposed method, a prototype of the laser ranging system was implemented and tested in air and underwater. Experimental results show that the maximal measurement error is 35 cm and the mean value is less than 15 cm for a range within 8.4 m. The system has the potential to be used for accurate ranging at short distance underwater.
2019, 48(10): 1005012.
doi: 10.3788/IRLA201948.1005012
A picosecond beam with Gaussian profile was efficiently shaped into a super-Gaussian profile beam by a circular aperture combined with a spatial filter-image relaying system. By studying the influence of the size of the filter aperture on the shaping effect in the spatial filter-image relaying system, the experimental results for maintaining the filling factor of the super-Gaussian beam greater than 0.76 in the propagation distance of 200 mm to 500 mm was obtained, and the corresponding efficiency of this beam shaping method was over 32%. Then, the beam with a super-Gaussian distribution was amplified. By using the thermal lens of semiconductor laser side pumped Nd:YAG crystal to replace the lens in the 4F image relaying system, the structure of the super-Gaussian picosecond laser amplification system can be simplified. After double-passing the single Nd:YAG crystal, a picosecond super-Gaussian profile beam with a near-field fill factor of 0.72, 1 kHz repetition rate, 11 ps duration and 3.0 mJ single-pulse energy was obtained, and the corresponding peak power intensity was up to 8 GW/cm2.
2019, 48(10): 1005013.
doi: 10.3788/IRLA201948.1005013
Laser perforation is a forward-looking technology in the oil well completion engineering, which has great application value for improving oil recovery. In order to improve the laser power and laser transmission safety used in oil well laser perforation, 10 kW-laser space incoherent combining was realized by using 19 fiber-transmitted 972 nm semiconductor lasers. By studying the effect of the radii, separation distances of collimated laser beams on the spot overlapping efficiency of combined laser beam, and simulating cross section energy distribution of combined laser beam, the structure design of a 191 space incoherent beam combiner was completed. A space incoherent combined laser beam with a single beam shape was achieved within the beam combining length of 300 mm, with a maximum combined power of 10.441 kW, a focal spot diameter of 21 mm, a line width of 2.46 nm and a combined efficiency of 98.2%. Ground laser perforation experiments for sandstone and steel plate were performed using the 10 kW spatial incoherent beam laser with perforation depths of 570 mm and 70 mm, respectively.
2019, 48(10): 1013001.
doi: 10.3788/IRLA201948.1013001
The oblique angle of the fiber coupling to the upper surface of the optical chip, is one of the key factors affecting the optical coupling efficiency. Contrary to the low efficiency, poor precision and instability of the traditional angle measurement methods, the coordinate system re-establishment method combined the image processing technology were adopted to realize the rapid and precise measurement of the oblique angles. Firstly, based on conventional image angle measurement method, a targeted checkerboard was introduced to calibrate coordinate system, thus reducing the errors caused by slight rotations of the optical axis, which would happen at the time that the CCD optical amplification system acquiring the image information of the tiny optical fiber. Then to reduce the influence of noise while ensuring the detection accuracy of the linear characteristics of the fiber, Hough transform method and image thinning method, which were two classic methods to extract the linear parameters of the fiber, were compared. Combining the triangular relationship of the linear elements on the projection surface, the oblique angle of the coupling fiber was finally obtained. The experimental results show that the line extraction algorithm based on Hough transform can measure oblique angle of the coupling fiber optic under small size with higher accuracy and speed, the error is about 0.1 and the average operation time is 0.370 seconds.
2019, 48(10): 1013002.
doi: 10.3788/IRLA201948.1013002
Focusing on the measurement efficiency of white light interferometry in vertical large-scale scanning process, a fast white light interference signal processing method based on effective signal extraction was proposed. The bimodal spectrum distribution model of the white LED light source was established, and the simulation experiments were carried out by using this model. From the simulation results, the minimum sampling interval length required by different algorithms at a specific sampling step was given, which reduced data volume without changing the measurement accuracy and allowed the calculation to start before the end of sampling. To eliminate the fluctuation of background value in vertical large-scale scanning process, a background value extraction method based on background set was introduced. By comparing with several signal processing methods, it was proved that the extraction method can effectively eliminate the influence on measurement accuracy. Finally, the proposed method was applied to the self-designed white light interferometer and a U disk interface was tested in using Fourier transform method. The results show that the total time from scanning to obtaining surface height information is reduced by 49.02%.
2019, 48(10): 1013003.
doi: 10.3788/IRLA201948.1013003
To verify the feasibility of tracking moving targets of micro-nano satellite using reaction wheel as actuator to adjust attitude, the physical simulation system of micro-nano satellite photoelectric tracking based on single-axis air-bearing platform was designed. Firstly, in order to improve the accuracy of physical simulation system, the disturbance torques of reaction wheel and air-bearing platform were analyzed separately; Secondly, aiming at disturbance torques and asymmetry of acceleration and deceleration time constants of reaction wheel itself, a flywheel control strategy combining gain scheduling and moment compensation was designed; Then, the tracking control system of analog micro-nano satellite was designed by using double closed-loop with velocity-forward control structure; Finally, in order to test the tracking performance of the simulation system, the tracking experiment of one-dimensional target with sinusoidal motion was completed. The experiment shows that the tracking accuracy reaches 0.4 for sinusoidal moving targets with maximum velocity of 9 ()/s and maximum acceleration of 4.5 ()/s2, which demonstrates that the micro-nano satellite using reaction wheel as actuator can track moving targets by attitude maneuver.
2019, 48(10): 1013004.
doi: 10.3788/IRLA201948.1013004
An efficient carrier removal method in off-axis interferometry to retrieve specimen phase distribution was proposed using image rotation and complex encoding. One rotated interferogram was obtained by rotating the specimen interferogram 180. The specimen interferogram and its rotated interferogram were firstly complex-encoded into a synthetic interferogram. After implementing Fourier transform, the two cross-correlation orders can be separated and then extracted by applying two band pass filters to the spectrum. The results containing phase distribution, carrier information of specimen interferogram and rotated interferogram can be obtained by implementing inverse Fourier transform. Through a division operation, carrier can be removed without complex calculation, phase unwrapping, or prior knowledge of the system. The feasibility and validity of the method were demonstrated by simulations and experiments. The obtained results show that the method can accurately retrieve specimen phase. The method consumes only 23.32% processing time of the original interferogram rotation method when retrieving thin specimen phase.
2019, 48(10): 1013005.
doi: 10.3788/IRLA201948.1013005
With the rapid progress of frontier research such as quantum control technology, nuclear-magnetic-resonance gyroscope(NMRG), which features significant advantages of high precision, small size, low power consumption and so on, has become one of the main development directions of high precision micro-miniature gyroscope in the future. Transverse relaxation time of Xe nucleon contained in the vapor cell is an important parameter to measure the performance of the vapor cell, which directly affects the random gyro angle migration. Accurate and rapid measurement of transverse relaxation time is conducive to the development of vapor cell with better performance. Based on the deduced principle of transverse relaxation time measurement of nucleon and LabVIEW software platform, an automatic measurement system for the transverse relaxation time of vapor cell nucleon was designed, which realized the functions of temperature control, xenon resonance frequency finding, magnetic field control and data processing and storage. The experimental results show that the automatic test system which has high measurement efficiency and test precision, stable and reliable work ability, and good man-machine interaction provides an effective measurement to test the vapor cell performance of NMRG.
A new type optical fiber sensor which realized the simultaneous measurement of temperature, pressure and flow rate was proposed, and some research work on its principle, structure and process design was carried. The flow rate sensitization structure combined by target and cantilever, thin-walled cylinder pressure structure were integrated on a sensing probe, 4 fiber Bragg gratings (FBG) were adopted to measure the temperature, pressure and flow rate simultaneous. By making addition or difference between two pairs of FBG resonance wavelength shift, the cross sensitivity between temperature and flow rate, pressure was solved. Meanwhile, the calibration system was developed, this system can achieve relatively accurate calibration and measurement of the proposed multi-parameter sensor.
2019, 48(10): 1013007.
doi: 10.3788/IRLA201948.1013007
An airborne infrared multispectral scanner can image remotely both in downward-looking and side-looking modes, by solving the contradiction among spectral resolution, high spatial resolution and large FOV imaging with whole device whiskbroom working mode. A theoretical accuracy of the object positioning error can be acquired by simulating the imaging geometry, which indicates that the angle measuring accuracy of the infrared multispectral scanner is the main error source, and should be precise enough to guarantee the linear whisk broom stripe images' pixel-level mosaic accuracy. Subsequently, a method of angular error compensation was adopted to reduce the long term and short term error. After compensation, the angle precision was ten times higher than before through labrotary test, and the accuray remained stable by environmental test. Also, the airborne flight test verifies the effectiveness of the compensation technology, the image relative geometric positioning accuracy is less than one pixel(10), which can meet the requirements of image mosaic.
2019, 48(10): 1013008.
doi: 10.3788/IRLA201948.1013008
Attitude disturbance caused by the random impact of airstream is the main disturbance source of the aircraft opto-electronic system. At the effect of the axis friction and mass imbalance of the system, the line-of-sight(LOS) stabilization is affected seriously due to the disturbance. In order to effectively suppress the influence of disturbance moment, a two-axis opto-electronic system dynamic model with outer pitch and inner azimuth was established, and the disturbance transfer relationship which contained the disturbance factors and movement coupling was obtained. A disturbance torque estimated method with extended Kalman filter(EKF) based on the dynamics model was proposed, and the feed-forward control loop of disturbance torque was established, consequently the disturbance torque was compensated at the real time, the system LOS stabilization was improved substantially. A semi-physical simulation experiment using flght simulation test table was carried out. The experiment result shows that the RMS result of LOS stabilization accuacy is 0.026 4 mrad of pitch and 0.029 0 mrad of azimuth frame with feed-forward method, which improve 64.1% and 69.6% compared to disturbance observer (DOB) method.
2019, 48(10): 1014001.
doi: 10.3788/IRLA201948.1014001
Based on two ways of light interference to LLL(Low-light-level) imaging system, the transmission model of light interference was established. Response characteristics of LLL imaging system was also analysed, and quantitative relation model of light radiant energy with response characteristics was also established. With simulation platform designed based on the data of theory and practice, low-light-level imaging under light interference was simulated. Computing results of gray mean, mean-square error and correlation function indicate that the quality of low-light-level imaging is directly related to the position and lightness of light interference source. The different position also can lead to different trend of correlation function. The light interference experiment was carried out, whose results were in agreement with simulation. It also indicate that the contrast between target and background is increased under light interference. And it is gradually decreased with increasing interference distance untill less then without interference.
2019, 48(10): 1017001.
doi: 10.3788/IRLA201948.1017001
Short-medium wave infrared detectors can work both in the low light night vision band and medium band at the same time, which can meet the requirement of complex detection environment. Infrared detector are widely used in military and civil fields. In order to improve the precision of infrared detector and shorten the response time, it is necessary to develop a wide band film with high transmittance that meets the system requirements in the short-medium band. The evaluation function of the variable scale algorithm was optimized based on the Baumesiter anti-reflection membrane design theory. A new weighted evaluation function model was established to design the membrane system structure with low sensitivity and high tolerance in the water absorption band of 2.6-3.3 m. The influence of different ion source assisted deposition parameters on the spectral characteristics of MgF2 was studied by optimizing the preparation technology for the water absorption band. Meanwhile,a step annealing process was used to obtain an effective method to reduce the water absorption. Finally,the spectral transmittance of the prepared film was greater than 96.5%.
2019, 48(10): 1017002.
doi: 10.3788/IRLA201948.1017002
Theoretical thermal desorption and in situ temperature programmed desorption(TPD) were developed to study the degassing of contaminants adsorbed in III-nitride photocathodes assembly. In the frame of Malev'sadsorption-diffusion outgassing theory, one dimensional slab was used to model the photocathodes assembly. By using the first and the second Fick'slaw, the expressions of the special gas concentration, the specific gas outgassing rate and the amount of degased specific gas over the time in the degassing process were obtained. To make it more intuitional, these parameters were ploted over time within different diffusion coefficient magnitude at the approximation of fourth order. In the TPD method for III-nitride photocathodes assembly, residual gas mass spectrum was thoroughly studiedat different constant temperature stage to determine which gases were desorbed into the vacuum. The least square method was employed to fit the expression of the specific outgassing rate at the constant temperature of 1 000 K, and the diffusion coefficient D for outgassing N2 was 510-5 cm2/s in the dynamic method of degassing process. By combining theoretical analysis with TPD experiments, the heating up temperature for sufficient outgassing the contaminants from the III-nitride photocathodes assembly was evaluated and verified.
2019, 48(10): 1017003.
doi: 10.3788/IRLA201948.1017003
Aiming at the shortcomings of traditional hyperspectral imaging system, such as large volume and weight, complicated structure of optical machine and high cost, it was urgent to meet the needs of miniaturization. The research on the design and preparation of distributed Bragg reflector(DBR) in hyperspectral imaging chip was carried out, and the simulator of multilayer film structure was developed. The fabrication of 5-layer film DBR and 7-layer film DBR were completed according to the structural design. The visible/near-infrared spectrophotometer was used to measure the reflectivity of the DBR, and the simulator for comparison, due to the existence of flaw in the actual preparation of the DBR, resulting in a error of 3%, The multilayer film structure simulator can guide the preparation of the actual DBR and lay the foundation for the hyperspectral imaging chip.
2019, 48(10): 1017004.
doi: 10.3788/IRLA201948.1017004
Microbial aerosols, as an important component of atmospheric aerosols, can affect atmospheric radiation characteristics through absorption or scattering. At present, the research on the optical properties of microbial aerosols is mostly limited to single-band or single germplasm. It is impossible to generalize the generality and particularity of microscopic aerosol optical properties, which is not conducive to comprehensively analyze the effects of microbial aerosols on atmospheric radiation characteristics. Herein, the spectral reflectances of three eukaryotic microbe and three prokaryotic microbes in the waveband from 0.25 to 15 m were measured. Based on the Kramers-Kroning algorithm, the complex refractive index (CRI) m was calculated and the FTIR spectra of microbes were analysed. The similarities and differences between the optical properties of the 0.25-15 m band of eukaryotic and prokaryotic microorganisms were compared. The conclusion can help to comprehensively understand and quantitatively calculate atmospheric radiation characteristics, provide theoretical support for microbial aerosol remote sensing detection and type identification, and provide new ideas for the development of new functional materials.
2019, 48(10): 1017005.
doi: 10.3788/IRLA201948.1017005
The vanadium oxide thin film with high quality was prepared on c-Al2O3 substrate for the first time by magnetron sputtering with rapid thermal process(RTP). Firstly, the surface particle size of the film was uniform, the surface root mean square roughness was about 16.75 nm, the major components of the film were VO2 and V2O5, V4+ content was about 78.59%. The prepared vanadium oxide thin films had the stable property of thermal-excited phase transition; Secondly, the terahertz transmission modulation was characterized by terahertz time-domain spectroscopy system(THz-TDS). The result indicated that the transmission ratios of the film increased with increasing optical excitation power; Finally, the amplitudes of the THz waves for vanadium oxide without any obvious fluctuation after the optimized process conditions of preparation and transmission ratios were nearly stable within repeated testing by in-site test, could be widely used for THz devices such as modulators and switches.
2019, 48(10): 1016001.
doi: 10.3788/IRLA201948.1016001
The application of CdZnTe photon counting detectors was achieved based on a linear array photon counting module. Two kinds of typical counting performance (C1, C2) have been observed when CdZnTe photon counting detectors were exposed to high flux X-ray beams. The X-ray pulse height spectrum characteristics, rise time of preamplifier pulse signal and defect level of the two typical CdZnTe detectors were studied and the intrinsic relationship between the above three results and the photon counting performance were demonstrated. Based on these results, the influence of temperature on the photon counting performance of the C2 detectors was studied. Increasing temperature can restrain the failure of detector induced by polarization effect and increase the counting rate, i.e. when the temperature rises to 33℃, the counting performance of the detector was significantly improved. Finally, the multi-energy region imaging results of C2 detectors at different temperatures were obtained using the linear array photon counting module, which showd that raising temperature significantly increase the image contrast and improve the imaging quality. The study provides an effective means to improve the performance of CdZnTe photon counting detectors by controlling external conditions.
2019, 48(10): 1016002.
doi: 10.3788/IRLA201948.1016002
In order to improve the photoelectric signal quality from position-sensitive anode of waveguide-gate thin film complex detector and reduce the influence of the multi-path broadening of the electron beams caused by the thin gate film, a direct extraction method of the complex detection signal of the waveguide gate based on micro channel plate was studied. According to the scattering physical model of electron beams with low energy in multimedia materials, the trajectory of incident low-energy electron beams was simulated by Monte Carlo statistical method in the gate film. Further more, accuracy deviation of signal extraction of the anode resulted from noises introduced from the waveguide gate was respectively analyzed under uniform distribution and Gaussian distribution. Accuracy deviation of signal extraction of the anode affected by the radial position shift of transmission electron beams in the process of transmission through the thin gate film was analyzed as well. The preamplification mode and series voltage controlled multi-stage cascade amplification mode were researched for weak photoelectric signal pulses came through the thin gate film to the anode. A fourth order Chebyshev low pass filtering method based on a circuit topology named Sallen-Key was proposed under additive Gauss distribution noise to reduce the influence of waveguide gate film on signal-to-noise ratio and make frequency response characteristics of signal wave form better. A peak sample and hold circuit of multi signal channels was presented as well. A complete and special platform was constructed to achieve the extraction of position sensitive signal from the waveguide-gate complex detection device, combined with parallel single point grounding connection mode of the whole readout system of anode signal and the direct extraction of position sensitive charge on wedge stripe anode. The signal extraction method of the device's anode was verified in a vacuum chamber. The quasi-Gaussian impulse extraction signal with 2 s pulse width and 200 kHz frequency was obtained.
2019, 48(10): 1023001.
doi: 10.3788/IRLA201948.1023001
Miniaturized portable spectral imaging was increasingly used in daily life, providing more convenience for people's lives. Citrus was one of the fruits that people often eat and store in their daily life. In the smart refrigerator, citrus was not conducive to identification and classification due to similar varieties. Spectral imaging technology used its characteristic wavelengths to realize its recognition. A new type of single-chip spectral imaging chip was used to build a compact and portable spectral imaging system. Spectral recognition technology was used to realize the classification and identification of citrus fruits, and cross-validation was carried out by batch samples, simultaneously establish the relationship between spectral resolution and accuracy, by constraining the spectral resolution, which effectively improved the classification and recognition accuracy of citrus fruits. Spectral resolution was less than 20 nm, and recognition accuracy could reach more than 95%.
2019, 48(10): 1026001.
doi: 10.3788/IRLA201948.1026001
Division of focal plane(DoFP) polarization imaging detector are composed of integrated micro-polarizer array on a focal plane array sensor, which make the DoFP polarimeters capture the polarization information real-time. However, it is difficult to perform the DoFP demosaicking and reconstruct the polarization information due to noise. A PCA-based spatial-temporal adaptive denoising method was presented to work directly on the DoFP videos. For each DoFP patch to be denoised, similar patches were selected within a local spatial-temporal neighborhood. The principal component analysis was performed on the selected patch to remove the noise. The spatial-temporal information of DoFP video was used to construct the sample patches. The proposed method worked directly on the DoFP video without explicit motion estimation. And then a fast bilateral filtering algorithm was used to remove the residual noise in different polarization channels of DoFP images. The experimental results on simulated and real noisy DoFP sequences demonstrate that the proposed denoising method can significantly reduce the noise-caused polarization artifacts and outperform other denoising methods.
2019, 48(10): 1026002.
doi: 10.3788/IRLA201948.1026002
Based on high-order nonlinear mixing model, a multi-objective hyperspectral unmixing algorithm was proposed, which solved the problem that the traditional method cannot obtain higher unmixing accuracy due to the outliers of hyperspectral image data. The proposed algorithm took the reconstruction error and spectral angle mapper as the objective functions and optimized them in order to reduce the outliers influence of hyperspectral data on the solution of optimization model and improve the two evaluation indicators. Then, the difference search algorithm was used to solve the multi-objective optimization model and overcame the tendency of the traditional gradient-based optimization method to fall into the local extremum problem and further improved the unmixing accuracy. The experiment results show that the proposed algorithm has more accurate endmembers abundance estimation and higher unmixing accuracy.
2019, 48(10): 1026003.
doi: 10.3788/IRLA201948.1026003
A dynamic track planning algorithm for disaster detection UAVs was proposed. When a major disaster such as an earthquake or flood, in order to obtain the disaster environment information for the first time, the UAV portable detection device can be used to detect the disaster ready information and images, and the information can be transmitted in real time. A dynamic track planning algorithm based on the framework of cultural algorithm was proposed. Firstly, the model was constructed for different terrains in the environment, and the corresponding function model was designed for obstacles such as mountains and peaks, and a digital map was constructed. The dynamic track planning was performed on the map model. The flight path planning algorithm can make the UAV independently plan the flight path during the flight process, realize ultra-low altitude flight, make the information collection more accurate, and effectively assist the rescue strategy. It was proved that the feasibility and effectiveness of the algorithm were verified by simulation and comparison with various algorithms.
2019, 48(10): 1026004.
doi: 10.3788/IRLA201948.1026004
Aiming at the issues of low ship detection rate caused by the failure of background modeling in the dynamic complex environment of traditional ship detection methods, a rapid ship detection algorithm based on gradient texture histogram features and multilayer perceptron was proposed. The feature fusion between gradient and texture histogram of the target was performed using multilayer perceptron, constructing the feature space for ship targets. Firstly, the region proposal model based on binarized normed gradient feature was trained to quickly generate a small number of ship candidate windows with high recall rate and then the gradient texture histogram features were extracted from each candidate window. Secondly, a multilayer perceptron was designed as a ship classifier to distinguish the gradient texture histogram features. Experimental results show that the proposed algorithm has an average precision of 90.0% and an average time of 20.4 ms/frame in multiple maritime scenes, which effectively realizes rapid ship detection in maritime scenes.
