2020 Vol. 49, No. S1
2020, 49(S1): 20190352.
doi: 10.3788/IRLA20190352
In order to take control of the space, the advanced countries have already developed extensively anti-satellite laser weapon, and have the anti-satellite ability of first step. Ground-based anti-satellite laser weapon can perform soft and hard damage to target such as satellite in orbit. Its technology is the most mature and has become an important part of future outer space attack and defense combat weapon system. It is highly valued by all countries in the world. Considering the purpose of ground-based anti-satellite, the introduction and analysis of public reported American ground-based laser system were emphasized. The system concept, operational concept, key component, test mode and shooting mode were shown, and the key function parameters relevant to the system were also analyzed, which provided a reference for studying the United States possible anti-satellite laser weapon and satellite target defense from laser striking.
2020, 49(S1): 20200090.
doi: 10.3788/IRLA20200090
The phase matching BBO was utilized as a frequency-doubling crystal to produce continuous ultraviolet laser with a central wavelength of 261.37 nm and the blue laser diodes with different wavelengths were used to pump the Pr:YLF in different ways. Two different wavelength blue laser diodes (444 nm and 469 nm) were used to pump Pr:YLF separately with V-shaped folded cavity structure. The two blue laser diodes were combined as the pumping source to increase the pumping power while retaining the high polarization absorption efficiency of Pr:YLF crystal after optimization. The length of Pr:YLF crystal was 5 mm, the doping concentration was 0.5%. Continuous 261.37 nm ultraviolet laser output with the maximum output power of 245 mW was obtained when the pumping power was 2 800 mW. The optical-to-optical efficiency was about 8.75%.
2020, 49(S1): 20200114.
doi: 10.3788/IRLA20200114
A rubidium-vapor laser pumped by a pulsed titanium sapphire laser was presented to investigate the dynamics of diode-pumped rubidium-vapor lasers. The vapor cell was filled with 70 kPa methane and 6 atm He at room temperature. The laser generated an average power of 208 mW, according to the conversion efficiency of 19% from absorbed 779.8 nm pump light to 795 nm laser. High peak power of 693 W rubidium-vapor laser was achieved with a 100 ns (FWHM) pulse width at a repetition rate of 3 kHz. Our experiments illustrate that the reabsorption of the Rb-He-CH4 mixtures will be a significant limitation in DPALs with the high pump power intensity. It can be deduced that the pump power intensity threshold of the Rb-He-CH4 system (6 atm He, 70 kPa CH4 at room temperature) at 418 K should be >200.6 kW/cm2 if LDs with a linewidth of 0.9 nm are adopted as the pump source.
2020, 49(S1): 20200145.
doi: 10.3788/IRLA20200145
The bi-static laser ranging technology can improve the detection capability of the laser ranging system. Therefore, the bi-static laser ranging mode has been well applied to the space debris laser ranging. The measured total distance can be used to estimate parameters such as the target positions. However, it encounters difficulties from the complexity of the normal equations involved in the precise orbit determination, and reducing the total distance to the distance from the target to each station (reduced distance) can simplify the normal equations. In this paper, a high-precision laser ranging test platform with one transmission and two receptions was established by combining the Yunnan Observatory's 1.2 m telescope 10 Hz common optical path laser ranging system with the 53 cm binoculars kilohertz conventional laser ranging system. Multiple passing satellites were conducted in the laser ranging experiment, and the directly measured total distance and the distance from the target to stations were obtained. The results show that differences between the distance from the target to the 1.2 m telescope and to the 53 cm binoculars are in line with expectation, and the distance precision reaches the order of centimeters, which could be used to study the distance reduction method for the debris laser ranging system of off-site transceiver.
2020, 49(S1): 20200165.
doi: 10.3788/IRLA20200165
The evolution characteristics of an Airy beam in PT symmetric medium by using split-step Fourier method was investigated. Then the impact of truncation width, modulation depth, and modulation width on the propagation properties of soliton generated from an Airy beam was discussed in detail. The results illustrate that when an Airy beam propagates in a PT symmetric medium, a soliton with periodic variation is shedded at the main peak position and a lateral offset is generated. Moreover, it is demonstrated that with decreasing truncation width a, increasing modulation depth P and modulation factor w, the peak-to-average power ratio of a soliton from Airy beam increases, which causes the beam interference and beam distortion become more and more. With decrement of modulation depth P and increment of modulation factor w, the peak intensity and peak-to-average power ratio of a soliton from an Airy beam jump obviously, leading to decreasing propagation stability of a soliton. However, the shedding soliton can still propagates stably in a long distance.
2020, 49(S1): 20200184.
doi: 10.3788/IRLA20200184
Laser technology is the key technology in laser ranging system. In the application of high performance ranging, the requirements of laser include high peak power and good stability. In order to achieve far away laser ranging, a large current and high stability driving circuit for pulse laser was designed. The mathematical model of the circuit was established, and the influence of the key parameters on the pulse constant current source was analyzed by using Matlab simulation software. The simulation results show that the voltage swing rate of the open-loop operational amplifier, the time constant of the later stage circuit and the circuit noise have an effect on the average value of the output current, the rise time and the stability. Finally, the test results show that the circuit module can generate 20 A pulse constant current, the stability is about 99%, and it can drive the pulse laser to work, which meets the requirements of ranging system.
2020, 49(S1): 20200262.
doi: 10.3788/IRLA20200262
Based on the established laser thermal conduction model and photoelectric conversion physical model of single-junction GaAs solar cells, the effects of pulse laser irradiation temperature and photoelectric conversion on single-junction GaAs solar cells were simulated and studied. Two different types, 532 nm and 808 nm, were studied. Under different irradiation energy and incident angle, the solar cell temperature, voltage-current characteristics, photoelectric conversion efficiency and other properties were changed by the pulsed laser with different wavelengths. The simulation results show that the smaller the angle between the incident laser and the normal direction of the solar cell, the greater the electric power of the solar cell output under the same laser irradiation intensity, 532 nm and 808 nm wavelength lasers have little difference in temperature caused by GaAs battery irradiation. 808 nm wavelength laser has a larger absorption coefficient for GaAs materials than 532 nm wavelength laser. Solar cells can absorb more energy and have a higher response. Single-junction GaAs cells irradiated with 808 nm wavelength laser can output more electrical power and bring greater photoelectric conversion efficiency.
2020, 49(S1): 20200101.
doi: 10.3788/IRLA20200101
The abuse of new psychoactive substances seriously endangers social stability and personal physical and mental health, and brings great difficulties to law enforcement due to its characteristics of camouflage, deceptiveness and fashion. Therefore, we developed a portable handheld Raman spectrometer based on a large numerical aperture lens (F/#=2.0) and transmissive volume phase grating. In addition, we conducted a systematic Raman spectrum test on 32 newly non-medicinal narcotic and psychotropic drug added by the ministry of public security, then established the corresponding Raman database. This research work will provide powerful reference and basis for anti-drug law enforcement.
2020, 49(S1): 20200108.
doi: 10.3788/IRLA20200108
In order to obtain new resonance modes for frequency selection of the metasurface, one or two slits were introduced into the all-dielectric resonance unit, all-dielectric frequency selective metasurface based on this type resonance unit was designed by using the local characteristics of electromagnetic field by slit. After simulating its transmission characteristics, it was found that when the long side of the slit and the direction of the incident electric field were the same, a stop band could appear at the low frequency, and the electromagnetic field was mainly distributed between the resonance units. When the long side of the slit was perpendicular to the direction of the incident electric field, a stopband and a passband could appear at the high frequency. Meanwhile, with the increase of the resonance frequency,the local characteristics of the electromagnetic field were more obvious and were better limited within the slit. By adjusting the width, number and spacing of slits, the operating frequency of the metasurface could be adjusted in a large frequency range. At the same time, the relative position of the slit and incident electric field could be changed by rotation to realize the reconfiguration of the metasurface. These theoretical results provide important theoretical guidance for the design of more complex resonant units based on slit.
2020, 49(S1): 20200113.
doi: 10.3788/IRLA20200113
Surface defects and contamination of optical elements may reduce the infrared detector ability. There are different level of surface defects on the window and filter in dewar. Optical simulation software LightTools was used to calculate the optical parameter. Meanwhile, to evaluate the optical characteristics of the systems, the concepts of stray radiation coefficient and signal-to-clutter ratio were introduced, so the defect tolerance can be reasonably judged. Then, when the filter position changed, the effect of surface defects on Dewar was analyzed by simulation. The results show that with the level of surface defects increasing, the non-uniformity of the image increased and the signal strength decreased. And at the same grade of defects, the closer the filter is to the chip, the more defects affect the Dewar optical characteristics, as a result, when encapsulating Dewar, it is important to strictly control the surface defect tolerance and arrange the location of the filter reasonably.
2020, 49(S1): 20200134.
doi: 10.3788/IRLA20200134
A structural design of a sub-wavelength dual guided-mode resonance (GMR) grating transmission filter was proposed on the basis of the rigorous coupled wave theory (RCWA). The fundamental concept was to use a symmetrical dual GMR grating structure to constrain all electromagnetic energy in the waveguide layer, resulting in efficient resonance peak. In addition, two double GMR grating structures were realized by cascading two single GMR grating structures with or without an air gap. The simulation results show that the filtering effect utilizing the double GMR grating structure without the air layer can be realized at 1 550 nm, whose peak transmittance is about 100% and half-value width (FWHM) can reach to 0.012 nm. The double GMR grating flat-top filter structure with the air layer of 2.13 μm, utilizing the GMR in conjunction with Fabry-Perot resonance (FPR), has a peak transmittance of about 100% at a resonance wavelength of 1 550 nm and a FWHM of 0.15 nm with the flatness of 0.1 dB. The proposed two compact and simple structures show promising potential for optical filtering and sensing applications.
2020, 49(S1): 20200195.
doi: 10.3788/IRLA20200195
A green OLED display with ITO/NPB(50 nm)/Alq3(60 nm)/Al(100 nm) structure was developed by using NPB as hole transport material and Alq3 as electron transport and light-emitting material. STM32f103c8t6 singlechip module, HC-06 bluetooth module, clock circuit module, reset circuit module and power module were used to constitute the wireless bluetooth control system, the OLED display was introduced as the human-machine interface display module of information transmission, and the information to be released by the user was transmitted to the display panel of the system through the way of mobile APP editing and bluetooth transmission. The bluetooth control system of the panel consisted of three sub modules:the first sub module was the information processing core based on 51 single chip microcomputer; the second sub module was the bluetooth module; the third sub module was the Android smartphone APP part. The whole system had many advantages:(1) OLED display had self illumination, high contrast, thin thickness, wide viewing angle and fast reaction speed; (2) if the content of OLED display needs to be modified, it could be modified in real time and wirelessly only by connecting OLED display with mobile phone software.
2020, 49(S1): 20200064.
doi: 10.3788/IRLA20200064
Ta2O5/Al2O3 laser gyro mirrors have been exposed in oxygen, air, argon and neon plasma respectively. Plasma was generated by capacity coupling Radio Frequency(RF) discharge technology. The effect of plasma pressure, plasma exposing time and plasma type on optical loss of Ta2O5/Al2O3 laser gyro mirrors was studied. The phenomenon and mechanism, for the optical loss change of Ta2O5/Al2O3 laser gyro mirrors was analyzed and discussed, by using comparing experiments, Energy Disperse Spectroscopy(EDS) and X-ray photo-electron spectroscopy(XPS). Ta2O5/Al2O3 laser gyro mirrors exposed in oxygen showed biggest total loss, which arrived 15 ppm(1 ppm=1×10-6). The value was 2 to 4 times of Ta2O5/Al2O3 laser gyro mirrors exposing in air, Ne and Ar plasma. The total loss changing was caused by the absorption of outermost 2LAl2O3 layer in Ta2O5/Al2O3 laser gyro mirrors. When Ta2O5/Al2O3 laser gyro mirrors exposing O2 plasma and Ar plasma alternately, the partial reversible changing phenomenon of 2LAl2O3 layer's absorption loss was found. The partial reversible changing phenomenon was discussed by XPS analyzing. The results show that the absorption loss changing is related to the exchanging of free oxygen and argon, occurred between outermost 2LAl2O3 layer and plasma. Some measures and suggestions are proposed to improve the stability of Ta2O5/Al2O3 laser gyro mirrors exposed in plasma.
2020, 49(S1): 20200135.
doi: 10.3788/IRLA20200135
In order to reduce the measurement errors of space attitude measuring instruments such as the star trackers, and improve the centroid accuracy of star point, a calibration method based on the phase-shifting interferometry principle was proposed, by studying the influence of the image detector's pixels geometric offset on the centroid accuracy of star point. The simulation model of image detector based on the properties of pixel response nonuniformity with pixels geometric offset was built, and the star centroid calculation was carried out in simulation. The simulation results proved that the pixels geometric offset of the image detector would produce parts of systematic errors to the centroid accuracy of star point. The image-detector pixel calibration results showed that under the condition of adding pixels geometric offset with the RMS value of 0.03 pixels and the 5% Gaussian white noise in the amplitude ratio, the calibration accuracy of the image detector pixel calibration method was better than 3×10-4 pixel(1σ). The research results turned to be a feasible scheme for the calibration technology of the pixels geometric offset of image detector, and had great significance to improve the measuring accuracy of attitude measuring instruments such as the star trackers.
2020, 49(S1): 20200149.
doi: 10.3788/IRLA20200149
For the pulse laser detection system using APD circuit, the existing peak extraction method could only detect the linear region of the unsaturated waveform, but not the nonlinear region of the saturated waveform, which made the detection range of the system extremely limited. Therefore, in view of the problem that the current system could not be detected in the nonlinear area, a linear and nonlinear unified response model based on APD circuit was established, and based on the response model, the waveform integration method and the nonlinear area energy inversion model were developed, which could be used to detect the saturated waveform in the nonlinear area, and the ideal inversion fitting of the model to the waveform in the nonlinear area was verified by experiments. The experimental results show that the fitting value had a linear relationship of 1.001 with the actual value, and the maximum relative error of the waveform integration method was only 4.69%, while the detection range was widened to 10.25 times of the peak extraction method, which proved that the method and the model could be used to detect the pulse laser in the non-linear area, and it could be applied to improve the detection range and detection ability of the pulse laser detection system based on APD circuit power.
2020, 49(S1): 20200158.
doi: 10.3788/IRLA20200158
In order to reveal the heat generation mechanism of crack during ultrasonic infrared thermography testing, an experiment was finished about testing a crack specimen when preload force was 100 N, 150 N and 200 N respectively based on the influence of preload force on heat generation of defects, and some results were obtained. It was observed that preload force was a direct ratio of the temperature evolution at crack field. Besides, the heat generation at both ends of the crack was significantly higher than the middle section, the hot spot in tip was most obvious, and the circle hot spot was most bright. Based on single degree of freedom damped system by displacement excitation and heat source temperature field superposition principle, a simple mathematical model for heat generation of crack under ultrasound excitation was proposed. After the temperature evolution of the reference point P1 and the crack tip point P2 was calculated by the theory model, it was found that the temperature evolution of P1 was consistent with the experiment result, and the error would decline between the temperature evolution of P2 and the temperature evolution curves and the temperature evolution rise was consistently between the both when the preload force increased. This model can describe the heat generation process at crack and provide a model foundation for the testing parameters optimization of ultrasonic infrared thermography testing, with certain theoretical significance and engineering value.
2020, 49(S1): 20200095.
doi: 10.3788/IRLA20200095
Target aircraft is regarded as the carrying platform of surface source infrared decoy, of which kinematic and radiation characteristics impact the development trend of infrared confrontation. Considering the economy of test cost, the algorithm was used to optimize simulation models of infrared decoy, and then the influence of flight parameters of target aircraft on jamming effectiveness of surface source infrared decoy was analyzed. Firstly, the target maneuver from database of maneuver was extracted, while the model of aircraft infrared radiation was established. Secondly, the optimization algorithm of missile tracking and anti-interference was introduced, and the solving procedures of combustion optimization algorithm in detail was analyzed. Finally, the flight parameters of target aircraft and the indicator of effectiveness evaluation were selected, based on which, the simulation results were compared with testing data to verify the reasonability of simulation result. It's concluded that the simulation results of jamming effectiveness of surface source infrared decoy match the testing data, satisfying the demand of jamming effectiveness evaluation.
The Direct Simulation Monte Carlo method was used to describe the motion, collision and energy transfer effects of a finite number of simulated molecules. The non-equilibrium flow field characteristics of the high-altitude plume were calculated, and the macroscopic parameters of the plume were obtained by statistical average method. On this basis, the Voigt line function was used to describe the broadening of the thin gas, and line-by-line integration was used to obtain the narrow-spectrum gas radiation. The physical transform equation, combined with the backward Monte Carlo method, were used to calculate the radiation transfer equations of the high-altitude plume. The applicability of the flow and radiation calculation models was verified using theoretical and experimental data. The flow and narrow spectrum infrared radiation characteristics of a small thrust engine were calculated and analyzed by using the above model. The results show that:due to the rapid expansion of the high-altitude plume, the density decreases rapidly, which leads to a significant non-equilibrium effect; the gas is affected by the velocity inertia, and the gas of different molecular weights will have a diffusion separation effect; the gas spectrum is thin and narrow, with Doppler broadening, and the peak of radiation moves to the middle wave, 4.7 μm CO and 6.5 μm H2O emission band radiation energy account for a larger share. The radiance in the axis direction is concentrated within the distance of twice the diameter of the nozzle, while the radiance distributed in the radial direction is concentrated in the shock region and the inner flow region within the separation wave line, and the radiance in other regions decreases exponentially.
2020, 49(S1): 20200188.
doi: 10.3788/IRLA20200188
The vibration absorption system of the infrared sight is very important for the infrared sight to bear high impact. The vibration absorption effect directly affects the shooting accuracy and reliability of the weapon. Based on response surface method, the parametric modeling and finite element analysis of the infrared sight and its vibration absorption were carried out in ANSYS Workbench. The response surface curve of the maximum displacement response of the vibration absorption system to the structural parameters was simulated under the impact load of 200 g, and then the sensitivity of the structural parameters of the vibration absorption connection device to the maximum displacement response was set:the change rate of the maximum displacement response to the structural parameters, which judged the sensitivity of the maximum displacement response to the structural parameters and guided the direction of optimization. The influence of structural parameters such as width, height and thickness of leaf spring on the maximum displacement response was optimized. The results showed that the width of leaf spring group was the most sensitive parameter. The results of optimization analysis could be directly used to guide the structural design of the vibration absorption system of infrared sight.
2020, 49(S1): 20200091.
doi: 10.3788/IRLA20200091
Image fusion is one of the important contents in the field of image processing. The traditional fusion algorithm fuses the source images and processes them according to certain rules. Although a good fusion effect can be achieved, the algorithm requires high image registration, then the fusion image also has the problem of loss of details, and the problem that the target is not obvious enough. To improve the above problems, the characteristics of the infrared image, visible image and the infrared target were analyzed, target detection was used in image fusion, and the DOG filter was used to extract the targets in the infrared image. The fusion coefficient matrix was obtained through multi-scale DOG image calculation, and then the fusion sub-map was calculated. Finally, a fusion image with obvious targets and good details was obtained,and the requirement for image registration was reduced. Five commonly used evaluation indicators, as well as the signal-to-clutter ratio and background similarity, were used to evaluate the fusion image. Experimental results show that the proposed algorithm is superior to the commonly used image fusion methods in both subjective vision and objective evaluation indicators.
2020, 49(S1): 20200092.
doi: 10.3788/IRLA20200092
In recent years, the application of CPU-GPU heterogeneous system in the field of optical remote sensing image data processing has received wide attention. Firstly, the architecture and development of CPU-GPU heterogeneous system were introduced. Next, the process of optical remote sensing image data processing was introduced. Then, the application of CPU-GPU heterogeneous system in optical remote sensing image preprocessing, follow-up processing data processing was introduced. Finally, the application of CPU-GPU heterogeneous system in optical remote sensing image data processing system was analyzed and summarized. The analysis shows that the CPU-GPU heterogeneous system is feasible and has a wide prospect in the field of optical remote sensing image data processing, but still needs to solve the key problems such as parallelizing design and optimization of the algorithm, the load balance of CPU and GPU, which is of great significance to promote the application of the CPU-GPU heterogeneous system in the optical remote sensing image data processing.
2020, 49(S1): 20200093.
doi: 10.3788/IRLA20200093
Hyperspectral imaging can provide more spectral information than an ordinary RGB camera. The spectral information has been beneficial to numerous applications, such as monitoring natural environment changes and classifying plants and soils in agriculture. The hyperspectral images reconstruction from a single RGB image is severely unconstrained problem. Previous methods need additional components or the spectral response by commercial camera. An end-to-end conditional generative adversarial network was proposed with modified residual network as backbone. The feature pyramid was used inside the network and a scale attention module was designed to fuse local and global information. In order to provide more accurate solution, another distinct architecture was proposed, named WNet. Experiments manifested the superiority of the proposed method over other representative methods in terms of quality and quantity. Experiments used both synthesized RGB images using public hyperspectral data and real-world image by ordinary camera demonstrate that proposed method outperforms the state-of-the-art. The WNet drops 45% and 50% in terms of RMSE and relative RMSE on the ICVL dataset than sparse coding.
2020, 49(S1): 20200096.
doi: 10.3788/IRLA20200096
According to the requirement of high resolution and wide range for hyperspectral imaging in the field of remote sensing, a high-speed spectral imager electronic system with high resolution and high reliability was developed, which was suitable for the application of Large Aperture Interferential Imaging Spectrometer(LASIS). The multiple four channel parallel ADC chips for analog-to-digital conversion was used, with V5 series FPGA as the core processor and high-speed SerDes chip for image data transmission. At last, the imaging performance and reliability of our high-speed imaging circuit were validated. All these measures provide technical support for China to enter the leading position in the field of space remote sensing, and also provide useful reference for further development of high-resolution hyperspectral imaging remote sensing.
2020, 49(S1): 20200121.
doi: 10.3788/IRLA20200121
Accurate segmentation of cells and nuclei is the key technology in computer-assisted diagnosis of cervical cancer. In this paper, a multi-active contour method, which was based on semantic segmentation of the U-Net model, was proposed for overlapping cells segmentation. First, each sample image was labeled as three parts:background, cell and cell nucleus. Then, the U-Net model was trained to segment the cervical images to obtain the cell and cell nucleus; meanwhile, the cell clump information could be obtained. The active contour for each cell was initialized according to the distance from the pixel point to the cell nucleus, and the energy functional was established based on shape prior of cells, the edge prior of images and the mutual prior between different contours. Finally, every single cell was segmented by minimizing the proposed energy functional. Experiment comparisons show that the segmentation method proposed in this paper can segment cervical cells under complex conditions, including independent cells, overlapping cells and their nuclei. The experimental results also prove the effectiveness of proposed method.
2020, 49(S1): 20200173.
doi: 10.3788/IRLA20200173
Aiming at the problem of residual network super-resolution reconstruction by residual algorithm, an improved deep composite residual network model for residual calculation was proposed. In this research, the original residual block was improved, which could make full use of all the convolutional layer feature information inside the residual block to improve the quality of the generated image; a double-layer composite structure was set to deepen the depth of the model structure, it could enhance the feature extraction of the image by the model and could extract more image features; the image feature information was enhanced using the method of transfer learning through transfer learning in the deep network structure, making the performance of the model more stable. The application experiment of the Tiangong-1 grayscale image show that the improved deep residual dense network proposed in this study performs well in the Tiangong-1 grayscale image super-resolution reconstruction, and has application value and research significance in the field of satellite imagery.
2020, 49(S1): 20200106.
doi: 10.3788/IRLA20200106
In the field of plant lighting, since the illuminated surface of the cultivation system changes continuously with the growth of the plant, the design of the plant lighting system need to consider the lighting situation and effect in the whole growth cycle and the space occupied by the plant growth process, so that it can provide the high illumination uniformity of the whole growth space. However, the extensive traditional plant lighting solutions are only optimized for a specific reference plane, which can not achieve the effect of high spatial illumination uniformity. Focusing on this issue, the lighting space of the whole plant culturist was taken as the research object, based on the theory of space lighting, and the recently proposed inverted light source and the traditional top array light source design scheme were taken as references to propose a dual light source module LED plant lighting system. The light source was set on both sides of the top and the bottom, and the high spatial uniformity were achieved through the complementary mixing of the two parts of light source. Taguchi method was used to simplify the experimental process, the variation analysis was used to optimize the key structural parameters, and the influence of light source distribution curve on the performance of plant lighting system was further studied. After several times of optimization, the optimal design of illumination uniformity of horizontal and vertical surfaces is 93.48% and 88.54% respectively, color-mixed uniformity is 90% and 87.13% respectively, and light energy utilization rate of planting surface is 41.63%.
2020, 49(S1): 20200124.
doi: 10.3788/IRLA20200124
In order to explore the origin and evolution of the universe, the large survey telescope will break through the existing detection depth and observation area to help humans solve more scientific frontiers unresolved issues. The meter-level corrector is different from ordinary transmission optical systems. To make the performance of the corrector meet the design requirements, the basic principles and general methods of lens support design were summarized and analyzed, a finite element model of elastomer support was established, and the analysis of key parts in the support structure was optimized. At the same time, the displacement and deformation, stress changes and imaging quality changes of the lens and the cell under different gravity loads were considered. The results show that when the elevation angle changes from 0° to 90°, the normalized point source sensitivity (PSSn) value of the elastomer support at least 0.973 1, and its surface shape error, stress and displacement also meet the system design requirements. The work has guiding significance for the design and optimization of similar large aperture systems.
2020, 49(S1): 20200200.
doi: 10.3788/IRLA20200200
With the composition and task form of spacecraft becoming more and more complex, more and more spacecraft were equipped with micro camera to realize visual telemetry of key objectives and their acting process in orbit. A three-dimension directed perception model based on rectangle view of micro camera was proposed for the view coverage problem of micro camera on spacecraft in this article, where pitch angle,yaw angle and roll angle of view could be adjusted to change sensing direction and view coverage area of camera. The criterion for spatial point coverage was established simultaneously. Then, genetic algorithm was used to optimize the installation site of cameras and pitch angle,yaw angle and roll angle of their view in order to achieve the coverage enhancement of the target motion space area. The proposed method was applied to optimize view coverage of lunar surface sampling space area. Computer simulating results show an effective performance of the proposed method for improving coverage ratio by view of micro camera.
2020, 49(S1): 20200207.
doi: 10.3788/IRLA20200207
Free space optical communication(FSO) is a communication system that realizes two-way information transmission through laser without optical fiber. It has the characteristics of wide bandwidth, good confidentiality, strong anti-interference, no frequency application, small size and low power consumption. Despite the high security of the FSO communication system, beam overflow still threatens the security of the communication. The use of chaotic encryption in communication can effectively improve the security of the system. In this paper, the differential chaos keying(DCSK) Gamma-Gamma turbulence model was used to improve the security of the FSO communication system, the expression of the system bit error rate was derived. Through the image data transmission of spatial channel, and the statistical histogram, pixel correlation and plaintext sensitivity were analyzed on the received data, the results show that the system has good security performance.
A frequency-domain variable density downsampling method was applied to the reconstruction of compressive sensing tomography for non-amplifying in-line hologram. The purpose was to extract a small amount of information from the frequency-domain of non-amplifying in-line hologram and realize the reconstruction of compressed sensing tomography from a small amount of data in the frequency-domain of the hologram. Here, firstly it introduced the principle of combining three variable density downsampling with compressive sensing tomography reconstruction of hologram. Three kinds of variable density downsampling respectively were radial distribution, spiral distribution and exponential distribution variable density downsampling. Secondly, it carried out simulation and test experiments and analyzed the reconstruction quality of the methods for variable density downsampling combined with compressive holography. By experiments, it could be seen that:(1) three kinds of variable density downsampling could realize the extraction of a small amount of data for hologram in the frequency domain; (2) with the increase of sampling rate, the compression sensing tomography reconstruction quality of a small amount of data obtained by variable density reduction sampling was continuously improved; (3) under the sampling rate of less than 50%, exponential distribution downsampling had higher reconstruction quality than the other two methods (for example, in the case of low downsampling rate of 15%, the reconstruction quality of exponential distribution was more obvious than the other two methods); (4) under the sampling rate of more than 50%, the tomographic reconstruction quality of the three downsampling modes was relatively high and basically consistent.
