Articles in press have been peer-reviewed and accepted, which are not yet assigned to volumes /issues, but are citable by Digital Object Identifier (DOI).
Fiber time delay fluctuations measurement based on one-way transfer
Wei Heng, Lu Lin, Pu Tao, Zheng Jilin, Zhao Jiyong, Zhang Baofu, Wu Chuanxin
Accepted Manuscript  doi: 10.3788/IRLA20200018
[Abstract](12) [FullText HTML](7)
In order to be compatible with the existing optical communication network, a time delay fluctuations measurement based on "single-fiber one-way" transfer scheme was proposed. Based on the temperature-induced variation of group velocity dispersion effect and Sellmeier equation, a proportionality model for calculating the one-way delay fluctuations was established with detecting the delay difference fluctuations between two propagating optical signals at given different wavelengths and accurate temperature measurement. Assuming proportionality coefficient in the model was the ratio between one-way delay fluctuations and one-way dual wavelength delay difference fluctuations. By simulation, the impact of fiber link parameters, such as temperature and wavelength difference, on proportionality coefficient was discussed. The experimental platform for one-way time transfer over 75 km fiber was conducted and the experimental results show that the measured proportional coefficient is −258.4, close to the theoretical proportional coefficient −277.3, and the corresponding one-way delay variation error is 660 ps. The measured results validate the correctness of the proposed model as well as the possibility of fiber time delay fluctuations measurement based on one-way transfer.
Signal processing method for shaped pulse and analysis of radiation flux deviation in low temperature
DU Hua-bing, SUN Ao, SHANG Wan-li, HOU Li-fei, CHE Xing-sen, YANG Yi-meng, YANG Guo-hong
Accepted Manuscript  doi: 10.3788/IRLA20200181
[Abstract](27) [FullText HTML](20)
Flat response X-ray diodes have been widely used in large-scale laser devices at home and abroad for the measurement of angularly distributed X-ray radiation flux. In practical experiments, flat-response X-ray diodes measure radiation flux images that have a step change in a shaped pulse-driven radiation source. In order to ensure a good signal-to-noise ratio, a single signal will be connected to multiple channels of the oscilloscope, and then the signals of different channels will be processed, and the final image with good signal-to-noise ratio will be stitched. The research in this paper mainly introduces this data processing method and gives theoretical calculations. At the same time, a theoretical approximation and numerical simulation of a deviation in the calculation of the low temperature radiation flow reduction are made, and the relative uncertainty of the deviation is obtained. Coupled with the uncertainty of all factors, the curve of the overall uncertainty of the flat-response X-ray diode as a function of the radiation temperature is obtained, which realizes precise diagnosis and completes the experimental needs for diagnosis.
Random laser radiation behavior of liquid crystal in photonic crystal fiber carrier
Wu Rina, Song Yunhe, Lu Jiaqi, Gao Rui, Li Yeqiu, Dai Qin
Accepted Manuscript  doi: 10.3788/IRLA20200171
[Abstract](26) [FullText HTML](16)
A hollow-core photonic-crystal fiber filled with a mixture of nematic liquid crystal TEB30A, chiral agent S-811 and laser dye PM597 is pumped by a frequency-doubled Nd: YAG laser with a wavelength of 532 nm. The laser emission spectra is measured and the random laser radiation behavior in the photonic-crystal fiber carrier is investigated. When side-pumping is applied to the fiber, the emitted random laser with a wider radiation direction from the side face has a wavelength range of 590−605 nm and an FWMH of 0.3 nm. When end-pumping is employed to the fiber, the emitted random laser from the end face has a wavelength range of 580−605 nm and an FWMH of 0.3 nm. After the sample is heated to the isotropic temperature, the laser emission with both pumping methods is shut down. The experimental results demonstrate that the dye doped liquid crystal mixture in the micropore induce the random laser emission in the photonic-crystal. The change in the mean free path of photon transport and the fluctuation of the dielectric tensor of chiral nematic liquid crystals with temperature are the main factors affecting the laser intensity.
Development of beam brightness enhancement based on diamond Raman conversion
BAI Zhen-xu, CHEN Hui, LI Yu-qi, YANG Xue-zong, QI Yao-yao, DING Jie, WANG Yu-lei, LÜ Zhi-wei
Accepted Manuscript  doi: 10.3788/IRLA20200098
[Abstract](626) [FullText HTML](569)
High brightness laser sources with different wavelengths play an important role in the fields such as military, industrial, and life sciences etc. However, due to the intrinsic spectral and thermophysical properties of current available laser gain materials, it is difficult to take into account the wavelength and output power of the traditional inversion lasers, which even leads to the decrease of beam brightness. To overcome this problem, beam cleanup by using nonlinear optical technology have been carried out in recent years, which is directly transferring the low-quality beam generated from inversion lasers into high-beam quality through the effects such as stimulated Raman or Brillouin scattering. Among them, with excellent properties such as high Raman gain coefficient, high thermal conductivity and wide spectral transmission range, diamond exhibits excellent beam brightness enhancement characteristics while realizing high efficiency Raman conversion, which provides a new technical path to generate high power and high brightness laser beam. Here, the development of brightness enhancement based on first-order and cascaded Raman conversion of diamond is reviewed, and its future applications are discussed.
Research Progress in Metal-Inorganic Semiconductor-Metal Photodetectors
Gao Linhua, Cui Yanxia, Liang Qiangbing, Liu Yanzhen, Li Guohui, Fan Mingming, Hao Yuying
Accepted Manuscript  doi: 10.3788/IRLA20201025
[Abstract](30) [FullText HTML](37)
The metal-semiconductor-metal photodetectors (MSM-PDs) have received great attention in areas of optical fiber communication, sensing, missile guidance, etc., due to their inherent merits of high speed, high sensitivity, and easy integration. This review focuses on MSM PDs with the semiconductor layer made of inorganic materials. Firstly, it introduces the basic structures of MSM-PDs, including the planar and vertical configurations. Then, the working principles of MSM-PDs are introduced. In addition to the common photoconductive and Schottky principles, the principle of hot carrier photodetectors with the metal layer as the light absorbing part is also introduced. Subsequently, the research progresses of MSM-PDs made of inorganic materials such as GaAs、InGaAs、Si/Ge have been described in detail. Additionally, the research progress of using metallic micro/nano structures to extend the response of wide energy band semiconductor based MSM-PDs to infrared wavelength range is presented. Finally, the full text is summarized and the future development of MSM-PDs is prospected.
Development of Coaxiality Measurement System of Turbine Components and Stud Standard Parts
Zhang Bo, Zhang Wengjian, Lei Lihua
Accepted Manuscript  doi: 10.3788/IRLA20200216
[Abstract](30) [FullText HTML](25)
Turbocharger and gearbox were widely used in the precision machinery manufacturing industry. The dimensional accuracy of Turbo parts and stud standard parts was an important guarantee for the assembly accuracy of Turbo parts and gearbox, among which coaxiality was a key parameter for the dimensional accuracy of Turbo parts and stud standard parts. According to the demands of coaxiality measurement for turbine components and stud standard parts, a set of checking fixture was developed, and a software based on LabVIEW was built for the measurement. The coaxiality of stud standard M12 was measured by experiment and the uncertainty of measurement was evaluated. The experimental results show that the coaxiality error obtained from the four measurements is 6.3–6.5 μm, and the extended uncertainty reaches 2.6 μm. The results show that the developed coaxiality measurement system is suitable for the high precision measurement of the coaxiality of turbine parts and stud standard parts.
Optical system design of star sensor with long focal length and athermalization
Wu Yanxiong, Qiao Jian, Wang Liping
Accepted Manuscript  doi: 10.3788/IRLA20200061
[Abstract](49) [FullText HTML](46)
Optical system is the core component of autonomous navigation star sensor to realize the collection of star light and high-precision attitude measurement. The influence mechanism and evaluation method of the accuracy of optical system for detecting different color temperature stars were studied and analyzed, and the wavelength weight distribution model of optical system design was established. According to the application requirements, a long focal star sensor optical system based on space satellite platform was designed, with the focal length of 95 mm, the relative aperture of F / 2.4, the field view of 8°×8°, the spectrum range of 450- 1 000 nm, and the energy concentration of more than 85% in 3×3 pixels. Based on the regular glass materials, the lateral color aberration of the optical system was corrected under ultra-wide spectral range and long focal. The lateral color aberration of the full field was less than 0.9 μm. The results of accuracy analysis show that the accuracy of centroid position is less than 0.36 μm in the range of 2 600−9 800 K, and the change of focal length is less than 2.7 μm in the range of 0−40 ℃, and the accuracy of centroid position caused by temperature is less than 0.45 μm.
Research on ultra-low power consumption methane detection system based on NDIR technology
Zhao Qingchuan
Accepted Manuscript  doi: 10.3788/IRLA20200140
[Abstract](24) [FullText HTML](30)
In order to meet the needs of low power consumption methane detection technology, an ultra-low power consumption infrared methane sensor and system based on non-dispersed infrared spectroscopy is developed, which is based on the characteristics of methane gas molecules having main absorption peak in the infrared band of 3.2 μm~3.4 μm. The selection of LED and PD devices and the design of optical path are studied based on the analysis of the principle of infrared differential detection. The power consumption of infrared methane sensor is reduced to 10 mW by using LED packets of pulses current drive technology. The influence of temperature change on the measurement of methane concentration is studied by experimental method, the temperature compensation algorithm formula is obtained by data analysis and linear fitting of normalization method. The performance experiment is carried out on the detection system platform, and the basic performance parameters are given. The system has the advantages of low power consumption, anti-interference of water vapor and good detection stability, and has important application value.
Design of the phase adjustment mechanism of the CCR array and its phase-locked experiment
Yu Tao, Li Xinyang, Li Feng, Geng Chao
Accepted Manuscript  doi: 10.3788/IRLA20190568
[Abstract](2795) [FullText HTML](727)
In order to correct the piston phase error of the corner cube reflector (CCR) array, a multi-element one-dimensional phase precise adjustment mechanism was designed, and a method of piston phase error detection and adjustment based on the coherent synthesis principle was proposed. Firstly, a mechanical device was designed to adjust the phase of a single corner cube reflector. Then, based on the principle of far-field imaging, the influence of piston phase error on far-field diffraction imaging was analyzed. Secondly, based on the difference of far-field facula, a method of measuring and adjusting the piston phase error of pyramid array was proposed. The experimental results show that the phase precise adjustment mechanism of the CCR array can achieve the adjustment accuracy of 0.1 μm level. By observing the far-field image of the reflected beam of the CCR array, adjusting the relative position of the CCR array, the PIB of the reflected beam is raised to 0.49, and the far-field image is close to the results of simulation. The piston phase error correction of the sub aperture of the CCR array is basically realized, and it improves the use efficiency of CCR array and expands the use scenarios of CCR array.
Visual monitoring method for atmospheric disturbance of moving objects
Zhang Yue, Su Yun, Gao Peng, Wang Xu, Dong Shikui, Zhang Xuemin, Zhao Hao
Accepted Manuscript  doi: 10.3788/IRLA20190535
[Abstract](27) [FullText HTML](21)
A method for visual monitoring atmospheric disturbance caused by flight of moving objects in the atmosphere was established. Method of light transmission in atmospheric disturbance, method of monitoring light deflection in atmospheric disturbance, and method of high-precision disturbance detection were three parts of the monitoring method in this paper. Based on the analysis of the principle of light deflection caused by atmospheric disturbance, calculation methods of refractive index, refractive index gradient, and light deflection transmission were researched. Based on principle of Background Oriented Schlieren, method for analyzing the influence of various parameters on monitoring system performance was proposed. Integral pixel search and sub-pixel location made up the high-precision detection method for detecting atmospheric disturbance. Related mathematical models with those three methods were established and simulation analysis was developed. The visual monitoring method proposed in this paper can be used in monitoring the atmospheric disturbance in the landing process of spacecraft returning to the earth and in the aerodynamic opening process of parachute. And it also could be used in monitoring the interaction between supersonic commercial aircraft and the atmosphere. The results of this paper provided an important method and approach to monitor atmospheric disturbance for optimizing aerodynamic shape.
System design for beam coupling and alignment monitoring of chip spectrometer
Liu Zhiying, Jiang Xin, Li Mingyu, Jia Wenbo
Accepted Manuscript  doi: 10.3788/IRLA20190532
[Abstract](18) [FullText HTML](23)
Aiming at the problem of the beam coupling and alignment monitoring of the chip spectrometer, an integrated optical system was proposed for avoiding the wear of the receiving end at chip spectrometer and the shielding of the optical fiber. The system consists of a front coupling system, a rear monitor system and a composite sharing system. The composite sharing system needs to cooperate with the front coupling system and the rear monitor system to complete the beam coupling and alignment monitoring functions respectively. The final system was designed by multiple combinations, a coupling system and a monitoring system were designed for a 6 μm incident fiber and a 20 μm×20 μm chip spectrometer receiving end at 1 550±50 nm. The energy analysis of the coupled system was performed by LightTools. The coupling efficiency was 0.733. The final system has a simple structure and can perform beam coupling and alignment monitoring at the same time, which provides a new method for the beam coupling and monitoring of chip spectrometers.
Study on LM algorithm in mueller's ellipsometry calibration method
Guan Yuqing, Fu Yunxia, Sun Jiayuan, HAN Zhi-guo, Zhang Bo, Kong Ming, Cao Chengming, Lei Lihua
Accepted Manuscript  doi: 10.3788/IRLA20200204
[Abstract](16) [FullText HTML](16)
According to the transmission method of polarized light in Muller ellipsometry method, this paper presents a method for calibrating the optical element parameters in ellipsometry system. By establishing a nonlinear least squares model of outgoing light intensity with respect to orientations of transmission axis of the polarizer and analyzer and orientations and retardation of the rotation compensator, the initial parameters are iterated with Levenberg-Marquardt (LM) algorithm. Accurate values of optical element parameters can be obtained, so as to achieve the calibration of components. Through the simulation experiment, using the SiO2/Si standard sample with the known Muller matrix and the calibration value of (24.90 ± 0.30) nm, the residual square sum of the light intensity value is calculated based on LM algorithm. When numbers of iterations accumulate to 50, the sum of squares converges of the residuals of the measurement and calculation is limited to 0.24. Then compared with the traditional multi-point calibration method, the feasibility of solving optical parameters based on LM algorithm is verified. Fitting results are validated by SiO2/Si standard sample with calibration value of (91.21±0.36) nm. Calculated film thickness is 91.53 nm and the relative error is 0.35%. Results prove that LM algorithm has advantages of rapidly converging and high precision in the parameter calibration of the Mueller ellipsometry system.
Fast phase unwrapping method based on multiple pigeonhole adaptive sorting
Wei Pengxuan, Huang Zhi, Zheng Xiao, Liu Haitao, Wu Xiang, Wan Yongjian
Accepted Manuscript  doi: 10.3788/IRLA20200032
[Abstract](17) [FullText HTML](17)
In order to improve the measurement accuracy and efficiency of the single-shot structured light measurement system, the phase unwrapping algorithm of the most important step in the three-dimensional reconstruction of structured light was improved. A phase unwrapping algorithm based on multiple pigeonholes adaptive sorting was proposed, which efficiently suppressed the error transmission during the unwrapping process and significantly improved the calculation efficiency. Firstly, the unreliability function of a pixel is defined according to the second-order difference of the pixels, and adjacent pixels are combined into a pixel group. Secondly, the pigeonholes with different ranges of unreliability values was constructed adaptively to meet the requirements of error transmission, and then pixel groups were placed into the pigeonholes with corresponding parameters in turn. Finally, the phase unwrapping was performed in ascending order according to the unreliability value of the pigeonholes. The verification experiments were carried out in a monocular structured light system. The experimental results show that the phase unwrapping algorithm proposed improves the efficiency by 38.37% compared with the original algorithm, and the accuracy of the point cloud solution has been greatly improved. It effectively optimizes the relevant performance of the measurement system.
Influence of Gaussian mirror parameters on LD-pumped Nd:YAG laser
MENG Pei-bei, SHI Wen-zong, JIANG Shuo, QI Ming, DENG Yong-tao, LI Xu
Accepted Manuscript  doi: 10.3788/IRLA20200127
[Abstract](20) [FullText HTML](17)
The influence of eccentricity and laser performance of LD-pumped Nd:YAG laser was investigated experimentally at different parameter Gaussian mirrors. Largest energy, narrowest width and smallest divergence can be obtained simultaneously only when the optical axis, laser crystal axis and Q-switch axis were in agreement, furthermore the optical axis went through the reflectivity center of Gaussian mirror. When eccentricity appeared, the energy, pulse width and divergence degraded more with smaller reflectivity radius or larger center reflectivity of Gaussian mirror. For 2.5 mm reflectivity radius and 30% central reflectivity Gaussian mirror, energy decreased 7%, pulse width increased 33%, and divergence increased 20% under 0.5 mm eccentricity. For laser performance, the smaller the reflectivity radius or center reflectivity of Gaussian mirror, the better the beam quality and the smaller the optical-to-optical efficiency. Considering the eccentricity influence and laser performance, 2.75 mm reflectivity radius and 20% center reflectivity Gaussian mirror was optimum. When the pump energy was 984 mJ, output energy of 128 mJ, pulse width of 7.3 ns, and beam quality M2 factor of 4.6 at 1064 nm were achieved, corresponding to the optical-to-optical efficiency of 13%. The experimental results in this paper can be a reference of the laser design and alignment.
Star Map Recognition Method of L2 Normal Distance
Wang Zewen, Wang Guangjun, Liu Xiaobo, She Jinhua
Accepted Manuscript  doi: 10.3788/IRLA20200040
[Abstract](17) [FullText HTML](21)
Based on the Hausdroff distance, this paper presents a star map recognition method that does not depend on the rotation direction and focal length of the star sensor. When constructing the data point set of Hausdroff distance, this paper uses the relative Euclidean distance corresponding to norm L2 as the set element to solve the influence of star sensor rolling angle on star pattern recognition. On the other hand, due to the influence of the focal length of star sensor, there are errors between the star sensor image and the standard reference image. When constructing standard data point elements, consider that if a data point set contains another data point set, the L2 normal distance between at least two data points between the two data point sets is the same. Therefore, the relative distance is scaled, and the relative spatial distance in each set is divided by the smallest relative spatial distance in the set to form a new set of data points. This method is not necessary to calibrate the star sensor image due to different focal lengths influence. The paper presents the calculation formula and implementation steps and the simulation results. The experimental results show that the algorithm can obtain the star map recognition results correctly and get the attitude information of star sensor in the case of star sensor rotation, scale transformation, etc.
Effect of aspheric particles on laser polarization characteristics
ZHAN Jun-tong, ZHANG Su, Fu Qiang, Duan Jin, Li Ying-chao,
Accepted Manuscript  doi: 10.3788/IRLA20200150
[Abstract](7) [FullText HTML](28)
The polarization scattering characteristics of spherical particle swarm have been studied, but in the real environment, the shape of particles is non-spherical, and the multiple scattering polarization characteristics of non-spherical particles have not been obtained. In this paper, the aspheric particle scattering model is improved based on the T matrix calculation method to obtain the scattering amplitude matrix of aspheric particles. Analyzing the influence of different horizontal and vertical axis ratios, shape and wavelength on the polarization characteristics of ellipsoidal particles, cylindrical particles and Chebyshev particles by computer simulation. The results showed that: for ellipsoid particles, the maximum polarization degree changed from 130° to 90° after the eccentricity changed from 2 to 3, and the polarization degrees of 450 nm, 532 nm and 671 nm increased by 50%, 25% and 24% respectively. Cylindrical particle long and short axis interchange has little effect on the change of polarization. The surface irregularity of chebyshev particles changed from 3 to 8, the polarization degree increased by 18%. The research results provide a theoretical basis for the multiple scattering characteristics of the aspheric particle group, finally solve the problem of the difference in polarization transmission characteristics between the real environment and the ideal environment.
An Optical Design of a Laser Tracker
JI Xiaohui
Accepted Manuscript  doi: 10.3788/IRLA20200088
[Abstract](1157) [FullText HTML](465)
In order to improve the search range and imaging resolution of the ground target by the laser tracker, a method of searching and tracking the target with a common aperture laser tracker under an airborne platform is presented and the optical system is designed. The laser tracker is fixed on the aircraft by strap down, it improves its stability. The R-C reflection telescopic system with common aperture is adopted to emit the laser and receive laser echoes, which reduces the overall size and improves the imaging resolution. The scanning search target is realized by double optical wedge component, and the search frequency is increased and the search field of view is enlarged. The relationship between the rotation angle of double optical wedge and the angle of outgoing optical deflection is given. The design results show that when the aperture of the system is φ300 mm and the focal length is 2100 mm, the overall size is 685 mm, the search and scan field of view is ±5°, the imaging field is ±0.08°, the maximum size of the imaging spot speckle is 2.417 μm, and the MTF value of the system is greater than 0.4 at 50 lines per millimeter, which meets the imaging requirements. When the target distance is three kilometers, the searchable range reaches 526 meters, and the four-meter-sized target can be recognized with a imaging resolution of two seconds.
1 123 nm Q-switched Nd: YAG laser based on gold nanocages and MoS2 saturable absorbers
Zhang Bin, Li Ying, Liu Binghai
Accepted Manuscript  doi: 10.3788/IRLA20200084
[Abstract](350) [FullText HTML](263)
Based on gold nanocages (GNCs) and MoS2 as saturable absorber (SA), respectively, passively Q-switched Nd: YAG lasers at 1 123 nm were demonstrated. When Q-switched laser with GNCs as SA, Q-switched pulse with the shortest pulse duration of 253 ns and maximum pulse repetition rate of 326 kHz was achieved under the pump power of 6.04 W with the maximum average output power of 221 mW. Compared with the experimental results of MoS2 Q-switched laser, the gold nanocage Q-switched laser has higher output power and efficiency, narrower pulse width and higher repetition rate. These results indicated a great potential of the GNCs film as SA in the near-infrared region.
Filter-based technology for evaluating proportions of high-order harmonics and its application
SUN Ao, DU Hua-bing, HOU Li-fei, SHANG Wan-li, CHE Xing-sen, ZHANG Wen-hai, WEI Min-xi, YANG Guo-hong, YI Rong-qing, YANG Yi-meng, JIANG Shao-en, WANG Feng, YANG Jia-min
Accepted Manuscript
[Abstract](33) [FullText HTML](49)
In order to meet the high requirements of the data measurement in the inertial confinement fusion experiment, experimental instruments must be developed in the direction of absolute measurement, and the requirements for calibration are also higher. Beijing Synchrotron Radiation Facility provides a good X-ray source for calibration in China. By measuring the current of a standard detector with or without a filter on a soft-X-ray source of beam line 4B7B in BSRF, the transmittance curves of different filters for monochromatic X-ray are studied and a fitted theoretical transmission curve is established. According to this, the proportion of second harmonic in the monochromatic light source was calculated, the results show that the second harmonic in the soft X-ray energy segment is mainly concentrated in the 180-300 eV and 450-800 eV, the share is mostly 15% below, the maximum can reach about 25%. Then, the calibration of the flat-response filter transmittance and the X-ray diode sensitivity was corrected using the calibration results, making their results more realistic and reliable. The technique for evaluating the proportions of high-order harmonics based on filter calibration experiments is highly efficient and accurate. It has good application value and can make the calibration result more accurate after data correction.
Powerful iodine stabilized He-Ne laser as wavelength reference
WANG Jian-bo, YIN Cong, SHI Chunying, WANG Hanping, CAI Shan,    
Accepted Manuscript  doi: 10.3788/IRLA20200111
[Abstract](953) [FullText HTML](412)
In order to meet the requirement of high output power of the laser monochromatic light source in the precision measurement, a high-power iodine stabilized He-Ne laser system with a fully enclosed, integrated structure was developed. The principle of saturation spectral detection, the method of absorption peak recognition and locking and the frequency stability of iodine stabilized laser were studied. Firstly, the basic principle of detecting saturation absorption spectrum of iodine molecular using the three harmonic method was introduced, and its mechanism of eliminating the power background was analyzed. Then, the stability of the integrated resonant cavity in the iodine stabilized laser was demonstrated, and the effects of axial expansion and lateral asymmetric deformation on the output power were discussed in detail. After that, the correspondence between the profile of laser output power and the iodine molecular saturation absorption peaks was presented, the feasibility of using the secondary harmonic signal to achieve absorption peak recognition was introduced, and the long-term locking ability of high-stability resonant cavity was demonstrated. Finally, the wavelength stability and reproducibility of high-power iodine stabilized He-Ne laser were analyzed. The experimental results shown that the standard deviation for the frequency jitter of high-power iodine stabilized He-Ne laser was 33 kHz, the stability at 1000 s and the reproducibility in three months were 4.1×10−13 and 3.3 kHz (7.0×10−12), respectively. Its absolute frequency was 3.0 kHz lower than the recommended value by the International Committee for Weights and Measures (CIPM).
Energy control algorithm of high frequency KrF excimer laser
Feng Zebin, Zhou Yi, Jiang Rui, Han XiaoQuan, Sun Zexu, Zhang Hua
Accepted Manuscript  doi: 10.3788/IRLA20200043
[Abstract](443) [FullText HTML](303)
Energy stability and dose accuracy are important indicators of high-repetition frequency excimer lasers for semiconductor lithography, which must be controlled by high-precision control algorithms. For the purpose of energy characteristic control, during the design of the algorithm, firstly, the single-pulse energy characteristics of the excimer laser were analyzed. Base on the analysis, a simulation model of the output energy of the excimer laser was established and had been experimentally proven to be effective. Then, the energy stability control algorithm, the double closed-loop dose accuracy control algorithm based on PID and the dose accuracy control algorithm based on decision algorithm were designed respectively and the control effects of the algorithms were tested separately on the simulation model. The simulation analysis results showed that the dose accuracy control algorithm based on the decision algorithm was more adaptable. The algorithm base on decision was validated on a KrF excimer laser with a repetitive frequency of 4 KHz. Controlled by the algorithm, the 3σ of laser energy stability less than 5% and the dose accuracy less than 0.4%, which satisfied the requirements of semiconductor lithography. The effectiveness of the energy characteristic control algorithm in the research had been proved in both simulation and actual experiments.
Development of solid-state high voltage switch for pulsed gas laser
Yang Yinhui, Zheng Yijun, Zhu Ziren, Sun Ke, Tang Huajiang, Tan Rongqing, Su Xinjun
Accepted Manuscript  doi: 10.3788/IRLA20200045
[Abstract](15) [FullText HTML](19)
A solid-state high voltage switch for pulsed gas laser based on magnetic pulse compression system is developed experimentally. In the experiment, the output efficiency of the magnetic compression switch is maximized by adjusting the reset current and load resistance. After compression by two-stage magnetic switch, the pulse width is about 5% of the original. The rising time after compression is about 180 ns, and the amplitude is about 16 kV. The first-stage magnetic compression efficiency is 89.2%, the second-stage magnetic compression efficiency is 97.7%, and the total compression efficiency reached 87.2%. After receiving the laser, measured output laser pulse energy is about 20 mJ, the output laser pulse half-height and width are about 85 ns.
Development on High Precision CO2 Isotope Measurement System Based on Infrared TDLAS Technology
Hou Yue, Pengquan Zhang, Guanyi Yu, Huang Kejin
Accepted Manuscript  doi: 10.3788/IRLA20200083
[Abstract](969) [FullText HTML](429)
For natural gas distribution monitoring, it is very important to measure the CO2 isotope with high precision. In this paper, the tunable diode laser absorption spectrum (TDLAS) technology is adopted to realize the high precision CO2 isotope measurement through the absorption spectrum line of 13CO2/12CO2 at 4.3 μm. The measurement system consists of a mid-infrared interband cascade laser (ICL) operating in a continuous wave mode, a long-path multipass cell (MPGC) and a mid-infrared mercury-cadmium telluride (MCT) detector. Aiming at the problem that the intensity of 13CO2 and 12CO2 absorption spectra is affected by the temperature, an MPGC high precision temperature control system is developed. In the experiment, five CO2 gases of different concentrations are configured to calibrate the measurement system, and the response linearity is up to 0.9996. The results show that when the integral time is 92 s, the isotope measurement precision is as low as 0.0139‰, which has practical application value.
Image clarification and Point cloud calculation under turbulence by light field camera
Zhang Xuanzhe, Wang Yan, Wang Jiahua, Hou Zaihong, Du Shaojun
Accepted Manuscript  doi: 10.3788/IRLA20200053
[Abstract](1107) [FullText HTML](558)
Image clarification and Point cloud calculation under turbulence is finished, by Improved information extraction algorithm of light field camera, based on phase space optics. This algorithm is more fully to use RAW data, because of adopting four dimensional density function to describe the structure of compound eye, and therefore, it can resist the influence of turbulence on local sub-aperture images, acquiring target point cloud steady, calculating the depth map and clarifying turbulence-degraded image. Light field camera based on such method acquire more than 4 k accurate wavefront distribution, when used for detection of indoor target behind the turbulence pool and outdoor target 500 m far from the camera, and outputting 3D point clouds and clear image successfully for both of them.
Study on laser polarization characteristics of visible light band in different humidity environments
ZHAN Jun-tong, ZHANG Su, Fu Qiang, Duan Jin, Li Ying-chao, Jiang Hui-lin
Accepted Manuscript  doi: 10.3788/IRLA20200057
[Abstract](815) [FullText HTML](707)
In order to improve the efficiency of polarization detection and obtain the polarization transmission characteristics in haze environment, this paper analyzes the influence of humidity in haze environment on polarization characteristics. Establish a polarization transmission model by improved Monte Carlo method, building a near-real water mist environment. Verifying the polarization model by laboratory experiments, comparing and analyzing the change of polarization degree and polarization state of linear polarized light on 450 nm, 532 nm and 671 nm under different humidity conditions, the confidence of simulation model >60%. The results show that the polarization degree of polarized light decreases with the increase of humidity of water-fog environment. The humidity values of the descending point of polarization degree are 50%, 70% and 90% when the laser wavelengths are 450 nm, 532 nm, 671 nm, respectively. For water mist, which is easily affected by humidity, polarized light with longer wave length should be selected as far as possible for transmission detection in visible band.
Hybrid phase retrieval with chromatic dispersion in single-lens system
Cheng Hong, Liu Yong, Hu Jiajie, Zhang Xiaolong, Deng Huilong, Wei Sui
Accepted Manuscript  doi: 10.3788/IRLA20200017
[Abstract](577) [FullText HTML](536)
Phase retrieval is to recover the original phase information by using the intensity information obtained from observation. Transport of intensity equation (TIE), as a traditional non-interference phase retrieval technique, can compute the losing phase information from only a minimum of two intensity measurements at closely spaced planes by solving the equation. This method usually requires the acquisition of intensity images by moving the object to be tested or CCD, which inevitably results in mechanical errors. A new phase retrieval method called chromatic dispersion-hybrid phase retrieval(CD-HPR) is proposed. The object is imaged at the same position by setting different wavelengths of light after passing through the single-lens system, in-focus and defocus intensity images are obtained without mechanical movement, and the initial phase information of an object is calculated from the phase retrieval technique based on TIE by combining the relationship between the defocus amount and the wavelength. Next angular spectrum iteration is used to improve the initial phase information. In this simulation, the RMSE between the phase recovered by this method and the original phase is 0.1076. At the same time, the phase of the lens array was restored by experiment. The error between the experimental result and the real parameter is 3.4%, which proves the correctness and effectiveness of the proposed method. This method extends the limitation of the traditional method that requires the light source to be monochromatic and improves the calculation accuracy.
Accepted Manuscript
[Abstract](2795) [FullText HTML](760)
Q-switched fiber laser with Ti: Bi2Te3 of different concentration
Pan Wei, Chen Hua-long, Wan Tie-bin, Zhang Hong-wei, Jin Liang, Zhang He, Xu Ying-tian, Zou Yong-gang, Shi Lin-lin, Ma Xiao-hui
Accepted Manuscript
[Abstract](4688) [FullText HTML](1458)
Nonlinear optical switch based on two-dimensional material is the core device of Q-switched fiber laser. The concentration of two-dimensional material optical switch will directly affect its nonlinear optical absorption characteristics, thus changing the time-domain characteristics of the pulse. Therefore, the influence of two-dimensional material concentration on Q-switched optical pulse is studied, and a saturable absorption optical switch based on Ti: Bi2Te3 with different concentration is made through experiments. The influence of Ti: Bi2Te3 concentration on nonlinear optical absorption characteristics is analyzed, and the relationship between the modulation depth, pulse width, repetition frequency and single pulse energy of Q-switched optical pulse with different concentration Bi2Te3 is obtained. Finally, the Ti: Bi2Te3 concentration is optimized for the resonator parameters. When the pump power is 71 MW, the central wavelength is 1560 nm, the pulse width is 8 μ s, the repetition frequency is 14.2 kHz, the average output power is 2.15 MW, and the corresponding single pulse energy is 151.4 NJ.
Depolarization Mechanism and Compensation Scheme of Radially Polarized Beams
YANG Ce, PENG Hong-pan, CHEN Meng, MA Ning, XUE Yao-yao, DU Xin-biao, ZHANG Xie
Accepted Manuscript  doi: 10.3788/IRLA202049.20200038
[Abstract](608) [FullText HTML](1760)
Depolarization mechanism and compensation scheme of radially polarized beams under non-uniform pumping are investigated. Theoretical analysis shows that, for the non-uniform pumping status, the thermal induced shear birefringence caused by the thermally induced shear stress within the cross-section of the isotropic crystal is the main reason for the depolarization of the radially polarized beams. Related experiments were designed to evaluate the depolarization of the radially polarized beams which under non-uniform pumping conditions by using two methods of thin-film polarizer (TFP) measurement and purity measurement, in which the TFP measurement method is used to detect the overall depolarization of radially polarized beams and the purity measurement method is used to detect local depolarization of radially polarized beams. With a peak pump power of 1.1 kW, the depolarization measured by the two evaluation methods is 2.34% and 2.53%, respectively. Based on the theoretical analysis and evaluation results, a combination of phase modulation and spatial mode matching was considered in the design of the depolarization compensation scheme, which improved the depolarization of the radially polarized beams by 59%. Meanwhile, a picosecond radially polarized beam with a pulse energy of 19.36 mJ, a purity of 90.13%, and a beam quality M2 factor of 3.8 was achieved.
The vibration isolation system for transportation of main mirror of a large Antarctic telescope
Yue Zhongyu, Cui Xiangqun, Gu Bozhong
Accepted Manuscript
[Abstract](15) [FullText HTML](31)
The Antarctic Observatory of China contains an optical telescope with a diameter of 2.5 meters primary mirror. Before installed, the telescope needs to be transported from the Zhongshan Station to the Kunlun Station by sled with violent vibration. In this paper, the vibration isolation system of the primary mirror for transportation is researched. First of all, the theoretical model of vibration isolation system is established and the performance of two-stage vibration isolation system is analyzed by the four-terminal parametric method. Then, the historical data from the expedition team is studied and the allowable dynamic condition of the primary mirror is calculated. The two-stage vibration isolation system consisting of a leverage buffer structure and a polyethylene foam structure is proposed and the performance of this vibration isolation system is researched. The results show that the vibration isolation system can meet the requirement. When load the most extreme impact signal which is measured by the expedition team, the maximum acceleration of the main mirror module is less than 5 g, and the z-direction moving range of the module is about 1.2 meters. This system can be used in the transport of the main mirror of the 2.5-meter telescope in the Antarctic. The vibration isolation system proposed in this paper is valuable for transportation of other fragile structures.
Picosecond multi-pulse burst pump KGW infrared multi-wavelength Raman generator
YANG Ce, CHEN Meng, MA Ning, XUE Yaoyao, DU Xinbiao, JI Lingfei
Accepted Manuscript
[Abstract](2784) [FullText HTML](730)
Picosecond infrared multi-wavelength Raman generator which adopted multi-pulse pumped KGW scheme was reported. A mathematical model was developed to investigate the effect of multi-pulse burst pumping regime on the vibrational mode of the Raman active molecule. The simulated results show that the response oscillation of the Raman active molecule to the multi-pulse burst pumping regime is more active and durable compared with the traditional single pulse pumping regime, which promotes the weakened molecule oscillation to return the natural frequency multiple times. The enhancement effect is beneficial to improve the Raman gain, reduce the Raman threshold, and increase the Raman conversion efficiency. During the experiment of picosecond multi-pulse pump KGW Raman crystal, the three-pulse burst pumping regime improves the Raman gain more than two times, reduces the threshold of stimulated Raman scattering more than 50%, and increases the Raman conversion efficiency more than 16% for 768 cm–1 Raman mode and 22% for 901 cm–1 Raman mode. Based on the three-pulse burst pumping regime, a 1 kHz mJ-level picosecond infrared multi-wavelength Raman generator was designed, which achieved the pulse energy of 1.39 mJ, the maximum Raman conversion efficiency of 29.6% for the 768 cm–1 vibrational mode of KGW, and the pulse energy of 1.38 mJ, the maximum Raman conversion efficiency of 25.7% for the 901 cm–1 vibrational mode of KGW. In addition, the Raman laser can radiate up to eight infrared Raman lines simultaneously for both the two vibrational modes of the KGW crystal, which covers the range of 800–1 700 nm.
Numerical study on backward light amplification and damage in high-power fiber laser
Sheng Quan, Si Hanying, Zhang Haiwei, Zhang Junxiang, Ding Yu, Shi Wei, Yao Jianquan
Accepted Manuscript
[Abstract](3859) [FullText HTML](2019)
The amplification of both continuous-wave (CW) and pulsed backward signal in high-power master-oscillator-power-amplifier based fiber laser are investigated using rate equation model. The results show that the CW backward light would be amplified significantly by the high-power amplifier and thus decrease the laser output seriously. For the pulsed backward signal, the pulse energy would not be amplified obviously since the energy storage is absent in CW fiber laser. Considering the damage threshold of the fiber and devices including end-cap and fiber Bragg grating (FBG), the amplification of CW backward light may damage the FBG of the laser oscillator, and the backward laser pulse with millijoule level pulse energy may damage the fiber, while there also exists the risk of end-cap damage when pulsed backward laser incidents.
Effects of gain distribution on self-similar amplification of picosecond pulses
Zhang Yun, Liu Bowen, Song Huanyu, Li Yuan, Chai Lu, Hu Minglie
Accepted Manuscript
[Abstract](5014) [FullText HTML](2175)
The effects of gain distribution on self-similar amplification of picosecond pulses in a Yb-doped fiber laser system are studied by numerical simulation. Ultrashort laser pulses amplified in self-similar amplification theoretical model is established to analyze the impact of pump configuration, fiber length and total gain coefficient on the self-similar amplification evolution and laser output performance. Detailed numerical simulation reveals that the best self-similar amplification result can be found for different cases, where high-quality self-similar pulses with ~100 fs transform-limited pulse duration are obtained. It is demonstrated that the self-similar evolution speed in a forward-pumping scheme is faster than that in a backward-pumping scheme for a fixed seed pulse. Furthermore, the results indicate that for the self-similar amplifier with different fiber lengths and gain coefficients, the forward-pumping scheme shows better evolution results in lower seed energy and longer wavelength range, while the backward-pumping scheme is more suitable for the higher seed energy and shorter wavelength range.
Thermal damage of monocrystalline silicon irradiated by long pulse laser
Guo Ming, Zhang Yongxiang, Zhang Wenying, Li Hong
Accepted Manuscript
[Abstract](13) [FullText HTML](31)
In view of the thermal damage law and mechanism of monocrystalline silicon for millisecond pulsed laser, the temperature of monocrystalline silicon irradiated by millisecond pulsed laser is measured by high precision point temperature meter and spectral inversion system. Then the temperature evolution process is analyzed. Also, the temperature state during the whole process of thermal damage of monocrystalline silicon irradiated by millisecond pulsed laser and the corresponding damage structure are studied. The results of this study show that the peak temperature of laser-induced monocrystalline silicon increases with the increase of energy density when the pulse width is fixed, When the pulse width is between 1.5 ms-3.0 ms, The temperature decreases with the increase of pulse width. Temperature rise curve shows inflection point when it is close to the melting point (1687 K), the reflection coefficient is from 0.33 to 0.72. During the gasification and solidification stages, it also shows the gasification and the solidification plateau periods. Thermal cleavage damage of monocrystalline silicon precedes thermal erosion damage. Stress damage dominates under low energy density laser irradiation, while thermal damage dominates under high energy density laser irradiation. The damage depth is proportional to the energy density and increases rapidly with the increase of the number of pulses.
Study on Longitudinal Forced Convection Heat Transfer for High Power Slab Media
HE Jianguo, LI Ming, MO Zeqiang, WANG Jinduo, YU Jin, DAI Shoujun, CHEN Yanzhong, GE Wenqi, LIU Yang, FAN Lianwen
Accepted Manuscript
[Abstract](6184) [FullText HTML](1381)
Thermal problem becomes more prominent in the highly-pumped laser gain mediums, for which, the forced convective heat transfer with the advantages of reliability and durability is widely used. However, a flow direction induced temperature gradient always appear within the laser operating substance during the convective heat transfer. Subsequently, it is significantly responsible for the detrimental thermal stress which mainly cause the wave front distortion. Herein, considering the idea of temperature matching between flow field and the operating substance, a cooling configuration for double face pumped slab cristal based on longitudinal forced convective heat transfer is presented, which shows a more efficient cooling and achieves a most homogeneous temperature distribution within the crystal. The influences of flow rate, state of flow field and surface roughness are systematically studied and tell that a fully developed flow state, higher flow rate and rougher surface lead to an improvement in cooling capability. In the simulation with 30 L/min flow rate, the calculated convective heat transfer coefficient is as high as 104 W/m2/K, and even higher when a more coarse surface is implemented. Furthermore, a module based on the configuration is fabricated and the experimental results agree well with the simulation, which shows a good temperature distribution and very weak thermal lensing is achieved.
Glass Fiber Supporting Structure of Dewar used in large infrared focal plane
CHEN Fang, GAO Chao, LUO Shikui
Accepted Manuscript  doi: 10.3788/IRLA20200060
[Abstract](398) [FullText HTML](339)
To improve the imaging quality, a pulse tube cryocooler is used in the remote sensor, and it is installed in the dewar assembly to make the infrared focal plane work in very low temperature. The thermal resistance between the cold head and the heat head should be big enough to improve the refrigeration efficiency of the pulse tube cryocooler. The thin-walled pulse tube connects the cold head and the heat head, and its radial support stiffness is too low to bear the vibration of satellite during launching. The traditional scheme is to add metal pole support structure, but the structure will bring additional heat leakage and the thermal deformation caused by the temperature difference of metal pole structure will cause the detector deformation which will affect the imaging quality. A glass fiber support structure is proposed. The glass fiber has the advantages of high tensile modulus, low thermal conductivity and very small area, and with reasonable position design this structure will improve the radial support stiffness and reduce the heat leakage. Because of the characters of low Bending Stiffness, the thermal deformation cannot pass to the detector. Compared to the metal pole support structure, the thermal resistance of glass fiber support structure increases by 3730 times, and solves the problems of high vibration resistance and low heat leakage.
Design of hybrid refractive-diffractive infrared dual-bandzoom optical system
YANG Hong-tao, YANG Xiao-fan, MEI Chao, CHEN Wei-ning
Accepted Manuscript  doi: 10.3788/IRLA20200036
[Abstract](497) [FullText HTML](410)
In this paper, the influence models of different diffraction elements on diffraction efficiency are established, and the diffraction efficiency among single diffraction element, harmonic diffraction element and double diffraction element was compared. The advantages of using double diffraction elements in infrared optical system are analyzed. The average diffraction efficiency of different material combinations is calculated. Based on this, a hybrid infrared dual-band and dual-field optical system suitable for airborne platform is designed. The resolution of the large field of view is 1.5 m@16 km.The long and the short focal length are 960 mm and 480 mm respectively. The zoom function is realized by switching the mirror to ensure the optical axis stability. The simulation results show that the MTF curves are smooth and close to the diffraction limit under the large temperature difference of −40 ℃~60 ℃.The RMS radius is within the radius of airy spots, and the minimum characteristic size of the binary diffraction surface is 6.9 μm. The design results meet the engineering requirements.
Incoherent digital holographic color imaging with high accuracy of image registration
Ren Hong, Bu Yuan-zhuang, Wang Xi, Li Yu, Du Yan-li, Gong Qiao-xia, Li Jin-hai, Ma Feng-ying, Su Jian-po
Accepted Manuscript  doi: 10.3788/IRLA20200022
[Abstract](898) [FullText HTML](848)
Fresnel incoherent correlation holography is a new technology which can record incoherent object holograms and has important applications in biomedical imaging and 3D remote sensing. The problem of image fusion registration in hyperspectral imaging, Three groups of double lens phase masks with constant focal lengths at 492 nm, 562 nm and 672 nm are designed and fabricated. The spatial light modulator calls the masks of three wavelengths in turn and records the holograms of the objects under the corresponding wavelengths, which owe to the spatial light modulator are programmable. Because of the three-color recorded light is modulated by the corresponding wavelength mask, the spot position size of the CCD surface is the same. The reconstructed images have constant lateral magnification, which can improve the image registration accuracy and avoid complicated spatial registration algorithm of spectral images. The system truly achieves high-precision registration and real-time fusion of holographic color imaging. The color 3D image obtained from the dice holograms has high color reconstruction after numerical reconstruction and color fusion.
Study on non-uniformity of ROIC for IRFPA
SHANG Chao, Wang Jinchun, Zhang Xiaobing
Accepted Manuscript
[Abstract](1702) [FullText HTML](933)
The ROIC has an important influence on the non-uniformity of the IRFPA device. The non-uniformity model of general system unit is established by using the taylor series of the dynamic nonlinear system function, and the ROIC non-uniformity model is established according to common architecture of analog ROIC. The spatial distribution characteristic of circuit statur parameters is modeled by mixing perlin noise and gaussion noise. The non-uniformity is evaluated with the spatial components of standard three demensions noise model. The time to sptial convertion from array signals to serial outputs is simplified by equal size convertion matrix. The non-uniformity of noise, multi-channel buffers and resposing nonlinearity is analized. The non-uniformity of a 320×256 array ROIC is evaluated by simulation and improved by circuit optimization based on our model. Simulaiton results show that it can be used to evaluate the non-uniformity and to assist with non-uniformity engineering optimization of ROIC at the system level.
Optic Design of two-stage Zoom Scanning Infrared System with Array Detector
DING Xue-zhuan, Zhou Pan-wei, Wang Shi-yong, Yu Yang, Li Fan-ming
Accepted Manuscript  doi: 10.3788/IRLA20200007
[Abstract](410) [FullText HTML](325)
A two-stage zoom array detector scanning infrared optical system is proposed. On the basis of traditional infrared secondary imaging optics, a two-stage zoom front telescope system is added to realize two-stage zoom by moving the zoom group along the optical axis. The zoom group adjusts the distance along the optical axis, and realizes the compensation of different working temperature and different object distances. In the middle parallel light path, a galvanometer is introduced, and the galvanometer is used to scan back in the corresponding angle range at a specific frequency, which can compensate for the object movement during the exposure time caused by the rotation of the scanning platform, and keep the image clear and stable during the rotation scanning without any shadow. The system is very compact, and can be widely used in the infrared searching and tracking system.
Influence of turbulent fluctuations on the infrared radiation characteristics of round jet flow
Luo Lei, Ji Honghu, Lu Haohao, Zhang Chen
Accepted Manuscript  doi: 10.3788/IRLA202049.20200030
[Abstract](916) [FullText HTML](980)
To investigate the influence of turbulent fluctuation on the infrared radiation (IR) characteristics of high-temperature round gas jet flow, the instantaneous and time-averaged values of temperature and species concentration of a high temperature round jet flow was calculated using the Large Eddy Simulation, and then the IR characteristics of the jet flow was calculated by two methods: one is based on mean temperature and another is on instantaneous temperature. The results show that the time-averaged values of the spectral IR intensity, the integral IR intensity and the IR brightness calculated by the second method are higher than that calculated by the first method. Both the differences between the results of the two methods and the IR fluctuation increase with the turbulent fluctuation and mixing layer thickness increasing, and the area that is affected the strongest by the turbulent fluctuations is the vicinity of the trailing of the high-temperature core zone in the jet flow. The difference between the IR brightness calculated by the two methods gradually decrease along the radial direction. For the round jet flow at Re=86 000 and the ratio of the temperature of surrounded air and the jet inlet temperature is 0.35, the integral IR intensity at the 90° detection direction calculated by the second method is higher than that calculated by the first method by 23.6%.
Design of the freeform imaging system with large field of view and large relative aperture
Chen Bingxu, Liao Zhiyuan, Cao Chao, Bai Yu, Mu Da
Accepted Manuscript  doi: 10.3788/IRLA202049.20200005
[Abstract](910) [FullText HTML](809)
In recent years, freeform surfaces have been used increasingly in off-axis reflective imaging systems with high performance levels. In this paper, the initial structure obtained based on vector aberration theory and genetic algorithm, by using a biased input field and an offset aperture stop, utilizing freeform surfaces described by XY polynomials to increase degrees of freedom to correct off-axis aberrations, the cooled off-axis reflection optical system with both a large FOV(field-of-view) and a large relative aperture is designed. The working band of the system is LWIR(long wavelength infrared radiation) 8~12 μm, the focal length is 400 mm, the F-number is 2, the FOV is \begin{document}$ 8^{\circ} \times 5^{\circ} $\end{document}, and the average root mean square (RMS) wavefront error of the system is 0.037054λ(λ=9 μm).The detector's cold stop matches the exit pupil of the optical system which ensure a 100% efficiency of the cold diaphragm. The system has a high energy concentration and a good image quality.
Optical design of continuous zoom polarization video microscope
LIU Xin, CHANG Jun, CHEN Wei-lin, DU Shan, Wu Chu-han, XU Xiang-xin, ZHU Yi
Accepted Manuscript  doi: 10.3788/IRLA202049.20200003
[Abstract](610) [FullText HTML](488)
Aiming at the problems of low imaging contrast and difficult recognition of traditional microscopes in low-illuminance environments, our paper proposes to design a continuous zoom polarization video microscope objective in combination with division-of-focal-plane polarization imaging technique. The objective lens works in the visible light band, with a zoom range of 1×−6.5×, an object-line field of view of 1.70 mm−11.1 mm, a total length of 220 mm, a working distance of 22 mm, and image distance of 14 mm. And the system is followed by a polarization detector to obtain the target's polarization information. After simulation analysis, the image plane is stable in the zoom range, and the imaging quality is close to the diffraction limit in each zoom state. The system can not only obtain images of different magnifications of the target on the electronic display and alleviate visual fatigue, but also obtain the polarization information of the target, improve the recognition probability of the target, the observation efficiency and the imaging quality in the case of low illumination.
Design of large aperture multi-spectra channel wavefront measurement system
Zhang Yu, Yang Zhongming, Liu Zhaojun, Wang Jihong
Accepted Manuscript  doi: 10.3788/IRLA202049.20190559
[Abstract](864) [FullText HTML](651)
With the development of wavefront measurement technology, the large aperture and multi-spectra channel wavefront measurement system has become a research hotspot in the field of wavefront measurement. The large aperture and multi-spectra channel wavefront measurement system is mainly composed of fore RC shrink-beam system、dimming component、beam splitters and wavefront sensors.The system with an effective aperture of 450 mm has working wavelengths of 0.5−0.8 μm, 0.9−1.7 μm and 3−5 μm. The design parameters of the optical system are given, the selection of optical element parameters in the system is described. The modeling and simulation of the optical system are completed by Zemax. The design scheme of the mechanical system is finished, and integrated optical-mechanical-thermal analysis of the system are completed. The parameters of the large aperture and multi-spectra channel wavefront measurement system are tested, the results show that the effective aperture of the wavefront measurement system is larger than 450 mm, at the environment of −10 ℃~50 ℃, the system can measure wavefronts in the visible, near-infrared, and mid-infrared bands with high precision and stability, the stability of the wavefront measurement system is better than 0.05λ (RMS, λ=532 nm).
Control method of adaptive optical system based on conjugate combined model of aberration
Yong Jiawei, Guo Youming, Rao Changhui
Accepted Manuscript
[Abstract](4304) [FullText HTML](1155)
In the concentric aperture circle of the unit circle, some Zernike modes have certain coupling, and the corresponding coupling aberrations will cancel each other in a certain concentric aperture after superposition. In this paper, Zernike polynomial is used to decompose the correction residuals of the deformation mirror. Through the analysis, it is found for the first time that that there is a coupling relationship described above between the main pattern items of the residuals, and the coefficients of the coupling terms will change regularly with the adjustment of the control signal of the deformation mirror, thus presenting different combinations of the coupling terms. In this paper, it is proposed to adjust the mirror surface shape by optimizing the control voltage vector of the deforming mirror, so that the conjugate aberration in the residual can achieve the best coefficient matching. In this way, the root mean square of aberration (RMS) in the circle of concentric aperture of the pupil can be reduced, and finally the image quality of the system can be improved. Simulation was carried out for point target imaging and extended target imaging respectively, and the results show that the optical image obtained by this method has better quality than that obtained by traditional method. This control method has a good application prospect when the deformation mirror has a large fitting residual.
Optical communication and sensing
Validity of beam propagation characteristics through oceanic turbulence simulated by phase screen method
Niu Chaojun, Wang Xiaobin, Lu Fang, Han Xiang’e
2020, 49(7): 20190452.   doi: 10.3788/IRLA20190452
[Abstract](7) [FullText HTML](3) [PDF 1262KB](0)
Oceanic turbulence is an important factor to restrict the application of underwater optical communication. Phase screen method is a simple and effective way to simulate the propagation process of complex beams through turbulence. The constraints of parameter setting for phase screen simulated oceanic turbulence based on the sampling principle and turbulence effects were firstly discussed here. Furthermore, the theoretical expressions of propagation characteristics of Gaussian beam through oceanic turbulence from weak to strong fluctuation regime were derived. Our goal in this research was to testify the validity of phase screen method in oceanic turbulence by comparison of major statistical characteristics of Gaussian beam propagating in oceanic turbulence simulated by phase screen method and the theoretical expressions derived. Results show good match between simulation results and theory formulas for long exposure beam radius and centroid displacement under different turbulence conditions, as well as the scintillation index under weak fluctuation regime. However, results show significant mismatch between numerically estimated and theoretically predicted values for the on-axis scintillation index in strong fluctuation regime.
Lasers & Laser optics
Optical design
Design of zoom fish-eye lens systems
Hou Guozhu, Lu Lijun
2020, 49(7): 20190519.   doi: 10.3788/IRLA20190519
[Abstract](2731) [FullText HTML](1169) [PDF 1320KB](27)
The zoom fish-eye lens had the characteristics of much larger field-of-view angle, much larger relative aperture, and much larger anti-far ratio. In the work described in this paper, the initial structure of a fish-eye lens with fixed focal length was firstly designed using the theory of a plane symmetric optical system. And then the initial structure components of the fish-eye lens were divided into two groups, the former-group and the rear-group, and then the entire zoom fish-eye lens system was optimized using Gaussian optical theory. Finally, a zoom fish-eye lens system with good imaging quality was obtained. This fish-eye lens system had a field-of-view angle of 180° with an 8 mm short focal length and a field-of-view angle of 90° with a 16 mm long focal length. Its relative aperture was 1/3.5. The design results show that the modulation transfer function of this zoom lens system at different focal lengths is no less than 0.45 when the spatial frequency is 50 lp/mm. This zoom fish-eye photographic objective lens had higher imaging quality than other zoom fish-eye lenses.
Design of large-aperture variable-direction mirror for space remote sensing camera
Zhang Fengqin, Dou Lianying, Pang Shoucheng, Li Qinglin
2020, 49(7): 20200008.   doi: 10.3788/IRLA20200008
[Abstract](7) [FullText HTML](5) [PDF 1579KB](0)
With the development of remote sensing technology, new camera requires large aperture variable-direction mirrors with higher accuracy. A new type of back support structure with highly stable support design was proposed for 1 000 mm×700 mm large-aperture variable-direction mirror. Compared with the conventional design, it had the characteristics of small volume envelope, light weight and wide adaptability. The mirror was made of ULE, and the light weight form of honeycomb layer was used. The mirror was mounted by means of a 3-point ball joint flexures system on the back. The stress in reflector assembling and the influence of thermal stress on the orbit was eliminated. It reached the stress-free support of the mirror. The problem of consistency between the ground test and in orbit was solved through the design of gravity unloading structure and the optimization of the unloading force. The simulation analysis shows that the surface RMS is 0.006λ(λ=632.8 nm) at 90° mirror testing direction. The surface RMS is 0.005λ at 75° camera imaging testing direction Ⅰ. The surface RMS is 0.011λ at 45° camera imaging testing direction Ⅱ. The first order modal of the component is 83.2 Hz, which has a high design stiffness and can meet the requirements of the mechanical environment during launch. This large-aperture variable-direction mirror design can meet the needs of new types of remote sensor and can provide a reference for the design of similar mirrors.
Structural design optimization of space gravitational wave telescope primary mirror system
Wang Chenzhong, Hu Zhongwen, Chen Yi, Xu Mingming, Chen Lisi
2020, 49(7): 20190469.   doi: 10.3788/IRLA20190469
[Abstract](49) [FullText HTML](36) [PDF 2281KB](8)
The structure and supporting components of the primary mirror system of space gravitational wave telescope were designed and optimized. The side three-point support was used to restrain the mirror body with the primary mirror, and the selection and layout of support points were studied. The mirror adopted a semi-enclosed structure with back drill holes, which can achieve large bending stiffness. The lightweight structure of the mirror was optimized by finite element calculation combined with multi-objective genetic algorithm. The lightweight ratio of the mirror structure reached 74% without reducing the surface accuracy. An adjustable bi-axis bipod flexure hinge structure composed of two non-barrier series flexibility elements was designed, which can compensate the surface error of the mirror. The mathematical model of the flexible hinge parallel mechanism acting on the mirror was established, and the parameters were analyzed based on MATLAB. The parameters were corrected by finite element method. Finally, the analysis of mirror shape under space thermal load was carried out. The results show that the error of mirror shape is better than λ/60, which meets the design requirements.
Optical design of infrared dual band/dual field of view seeker
Mao Yankai, Zhao Zhenyu, Zhang Guohua, Shi Guangyu
2020, 49(7): 20190490.   doi: 10.3788/IRLA20190490
[Abstract](33) [FullText HTML](30) [PDF 1345KB](3)
At present, most of the strapdown seekers use the combination of infrared single band and single field of view to match and intercept the target, but this method is susceptible to factors such as target/background characteristic, detector performance, field of view in increasingly complex battlefield environment. On the basis of retaining the original single medium wave infrared large field of view of a strapdown seeker, a new type of IR dual band/dual field of view seeker was proposed by adding two long wave large and small field of view. By using the image fusion of medium and long wave dual band and the switching of dual field of view under long wave infrared, the difference between target and background feature information was highlighted, which can effectively improve the interception probability of missile to target. The optical system was designed with CODE V software. The whole system adopted the common aperture optical design, which had good imaging quality and meets the system requirements.
Integrative design of structure control for two-axis fast steering mirror with flexible support
Ai Zhiwei, Ji Jianbo, Wang Pengjv, Li Jing, Zhou Haoyang
2020, 49(7): 20190479.   doi: 10.3788/IRLA20190479
[Abstract](9) [FullText HTML](4) [PDF 1848KB](3)
To predict and confirm the frequency characteristics and time-domain performance of the fast steering system (FSM) in the structural design stage, a two-axis flexible-supported FSM was studied and tested. A new flexible support structure was proposed, and the main structural parameters of the FSM system were designed based on the performance index of FSM which is decided by the beam requirement of laser transmission system. The dynamic mathematical model of the system was studied, and the control mode and parameters of the closed-loop system were determined. The rigid-flexible coupling model of the swing part of the system was established, and the structural non-linear model was obtained. The joint simulation test of the system and the motion system were carried out based on the model above. The simulation results show that the resonance frequency of the system in the direction of motion is 54 Hz, and the errors between the calculated result and the finite element result is both 3.8%, and position closed loop bandwidth is 203 Hz which is right to the index. The output results in time domain show that the overshoot of the system is 3.5% and the adjustment time is 10 ms, the deviations from the theoretical results are 3% and 5 ms.
Infrared technology and application
640×512 digital InGaAs detector assembly
Zhong Shengyou, Chen Nan, Fan Mingguo, Zhang Jiqing, Zhu Qin, Yao Libin
2020, 49(7): 20190495.   doi: 10.3788/IRLA20190495
[Abstract](13) [FullText HTML](6) [PDF 1539KB](1)
Digital InGaAs detector significantly orients the development of short wave (SW) infrared detector technology, it not only can increase integrated level of the system, but also can develop the imager’s performance. The key point to realize the digital InGaAs detector is integrating ADC into the readout integrated circuit (ROIC) and realize digital ROIC (DROIC). The 640×512 DROIC was designed and fabricated, it interconnected InGaAs detector focal plane array with In and realized digital InGaAs detector assembly. The proposed digital InGaAs detector assembly was tested, and the measurement results show that its readout noise is 230 μV, peak quantum efficiency is 65%, detectivity under 300 K temperature is 1.2×1012 cm Hz1/2 / W, and the power consumption is 94 mW when frame rate is 60 Hz. The measurement results indicate that the digital InGaAs detector assembly has some features as low readout noise, high linearity, wide transmission bandwidth, good resistance to interference and so on.
Simulation analysis of influence of aerodynamic heating effect of dome window on rosette scan system
Lv Yinhuan
2020, 49(7): 20190520.   doi: 10.3788/IRLA20190520
[Abstract](531) [FullText HTML](437) [PDF 1463KB](18)
Aiming at the influence of the aerodynamic heating effect of the high-speed vehicle on the optical performance of the vehicle, the heat radiation model of the dome window of the vehicle was established. On this basis, the simulation control program was programmed, and the optical automatic tracing was realized by using TracePro software, and the thermal effect of the dome window produced during the scanning of the entire optical system, as well as the effects of individual optical moving parts when scanned separately were dynamically simulated. Through the analysis of the transmission path of stray light caused by thermal effect in the process of rosette scanning, the proposed improvement measures were obtained, which provided a reference for the optical performance analysis and environmental failure research of high-speed vehicle.
Influences of weather conditions on vehicular infrared assistant driving performance
Wang Hongpei, Luan Guangqi, Tian Chao, Wang Jiaxiao, Yang Peng, Sun Mingzhao
2020, 49(7): 20190507.   doi: 10.3788/IRLA20190507
[Abstract](911) [FullText HTML](655) [PDF 1504KB](5)
Based on comprehensive analysis of vehicle infrared assisted driving safety braking process, infrared static detection model and dynamic detection model, the model of visual range for assistant driving safety was established. The relationship between maximum safe speed, road condition, infrared detection performance was analyzed. It is found that it is mainly related to sliding adhesion coefficient and detection distance. Through the correction calculation of infrared detection distance, the maximum safe speed at night was simulated. The results show that it is mainly affected by the temperature difference between target and background. Emphasis is laid on foggy and rainy weather for example analysis. The results show that foggy weather mainly affects the detection distance, especially when the visibility is less than 1 km, and the maximum safe speed need be controlled at 21-25 km/h when the visibility is 5 km. Rainy weather will affect the sliding adhesion coefficient and detection distance. The maximum safe speed control under infrared recognition is the main method for assistant driving. When rainfall intensity is 50 mm/h, the maximum safe speed need be controlled at 12-14 km/h.
Infrared light field relay imaging system based on micro field lens array
Wang Tengfei, Chen Yonghe, Fu Yutian
2020, 49(7): 20190548.   doi: 10.3788/IRLA20190548
[Abstract](64) [FullText HTML](31) [PDF 1173KB](10)
Light field imaging is a method of imaging by acquiring light field information and refocusing on a specific plane. With the limitation of the light field camera structure, the detector is generally modified to achieve coupling of the microlens array and the detector. It is not applicable to infrared light field cameras. To this end, a novel structure of a micro field lens array combined with a relay lens was proposed. This new structure utilized a relay lens to image the intermediate image plane at a 1:1 ratio and eliminated the vignetting of the relay lens through the micro field lens array. The modulation transfer function curve of the system was calculated by the slanted edge method. The image quality of direct coupling, relay lens coupling and new structure coupling were compared. According to different refocus planes, the curve value of the new coupling structure at Nyquist frequency was increased by 5%-240% compared with that of the relay lens coupling structure. It was close to the curve value of the direct coupling structure. The new structure can realize coupling and avoid the sharp decrease of system image quality. It plays an important role in the infrared field camera.
Photoelectric measurement
Networking method of multi-view stereo-vision measurement network
Qiao Yujing, Jia Baoming, Jiang Jingang, Wang Jingyi
2020, 49(7): 20190492.   doi: 10.3788/IRLA20190492
[Abstract](1001) [FullText HTML](1177) [PDF 1486KB](8)
Stereo-vision network measurement was the core technology for 3D measurement. In order to ensure the full coverage and reconstruction accuracy of 3D reconstruction, the camera needed to be intensively shot during the measurement process, resulting in slow 3D measurement and large calculation.Therefore, a multi-view stereo-vision measurement network networking method was proposed to solve the above problems. Firstly, the object model was obtained by SFM technology (motion recovery structure), establishing the ellipsoid reference coordinates, estimating the optimal distance between the camera and the object to be tested, and arranging the initial viewpoint position. Secondly, the minimum number of cameras, to achieve full coverage 3D imaging, was filtered based on visual constraints to cluster analysis and loop iteration of the initial viewpoint. Finally, the measurement experiment was carried out, and the ellipsoidal measurement network with the lampshade as the object to be tested was arranged. The comparison of the number of cameras, coverage and measurement accuracy with the spherical measurement network was carried out at different depths of field. The experimental results show that 22 viewpoints are selected through the final iteration of the method, so that the coverage rate reached 100%. The standard deviation of the measurement accuracy was stable to 1.1 mm and the measurement efficiency was significantly improved compared with the spherical network. The original appearance of the object to be tested was restored through the 3D reconstruction of the lampshade rendering, which verified the feasibility of the proposed method.
Design of a hybid ultrasound and digital holography imaging system for detection of internal micro-defects
Wang Xing, Gao Lei, Wang Yan, Wang Haitao
2020, 49(7): 20190518.   doi: 10.3788/IRLA20190518
[Abstract](2525) [FullText HTML](1359) [PDF 1613KB](9)
Non-contact detection of internal micro-defects of the micro-electro-mechanical system and minimechanism required a high accuracy and strong penetration test. The current detection methods were difficult to achieve high precision while also having strong penetrating power. In response to the above problems, a composite system of ultrasonic detection and digital holography imaging was designed. Ultrasonic detection technology had strong penetrating power, and digital holographic imaging had higher resolution. The composite system designed included a near-field ultrasonic subsystem, an digital holographic subsystem and a synchronous control subsystem. In the near-field ultrasonic subsystem, the generated near-field ultrasonic wavefields passed through the internal defect of the sample and formed the surface ultrasonic wavefield on the surface of the sample. The digital holographic subsystem mainly measured and analyzed the transient morphology of the surface ultrasonic wavefields, and the internal defect information contained in the surface ultrasonic wavefield could be analyzed. The experimental results show that the system can measure the transient 3D topography of the ultrasonic wavefield by analyzing the ultrasonic wavefield, and can effectively detect internal defects of 50 μm.
Detection of microcrack in inductor based on orthogonal scanning line laser thermography
Wang Xiaona, Zhang Yishu, Hou Dexin, Ye Shuliang
2020, 49(7): 20190522.   doi: 10.3788/IRLA20190522
[Abstract](603) [FullText HTML](470) [PDF 16690KB](17)
In the detection of microcrack on the surface of ferrite inductors, traditional machine vision detection has problems such as low signal-to-noise ratio and low detection accuracy. In order to solve these problems, a microcrack thermography detection system based on line laser orthogonal scanning was built. The surface temperature change of the sample was recorded by the thermal imager and imaged. Sub-maximum filtering was used to eliminate non-uniformity and edge contour interference of the thermographic image. And the multi-directional fan-shaped filtering was used to obtain the grayscale image of the sample in different directions. Finally, qualitative detection of microcracks on the surface of the inductor was realized by BP neural network and morphological processing. The results show that all cracks and microcracks are correctly imaged based on 610 samples in two specifications. The automatic identification algorithm has a false detection rate of 5%, a crack miss detection rate of 6%, and a microcrack detection rate of 10%. The system detects 20 to 35 inductors every 5 s and can be used for automated quality inspection in production.
Boresight parameters calibration method of VMLS system based on reference planar features constraint
Yu Jiayong, Cheng Lang, Tian Maoyi, Lu Xiushan, Ma Longcheng, Zhou Maolun, Cao Yuefei, Li Guoyu
2020, 49(7): 20190524.   doi: 10.3788/IRLA20190524
[Abstract](2984) [FullText HTML](1553) [PDF 1579KB](17)
The vehicle mobile laser scanning (VMLS) system is a highly integrated multi-sensor measurement system. The accuracy of the VMLS system depends on the accuracy of not only the integrated sensor, but also the calibration of boresight parameters between the laser scanner and the integrated navigation system. Considering the convenience and effectiveness of the calibration method of the boresight parameters and the accuracy evaluation of the VMLS system, a calibrating method of the boresight parameters of the VMLS system based on the reference planar features constraint was proposed. The proposed method was based on the direct georeferencing of lidar measurements including the boresight parameters. The equation used the minimum distance deviation from laser footpoint to reference plane as the constraint. In addition, considering the correlation between rotation and offset amount of the boresight parameters, the stepwise solving method was composed to separate boresight angle and offset parameters. Finally, through the datum acquired from calibration field and check fields, the internal and external accuracy of VMLS system were evaluated. The experimental results show that the proposed method can effectively eliminate the influence of boresight errors. After calibration, the internal accuracy is 0.007 m and the external accuracy is 0.024 m.
Defocus projection three-dimensional measurement based on deep learning accurate phase acquisition
Zhao Yang, Fu Jia'an, Yu Haotian, Han Jing, Zheng Dongliang
2020, 49(7): 20200012.   doi: 10.3788/IRLA20200012
[Abstract](23) [FullText HTML](15) [PDF 1454KB](6)
The digital fringe projection three-dimensional (3D) measurement technology can generate a sinusoidal fringe pattern for 3D measurement by defocusing a binary fringe pattern. It can achieve extremely high projection speed and has great potential in the field of high-speed 3D measurement. However, the binary fringe pattern inevitably contains higher-order harmonics, resulting in a phase error introduced into the calculated phase, thereby reducing the accuracy of high-speed 3D measurement. A 3D measurement method for defocused projection based on deep learning accurate phase acquisition was proposed. The image feature processing capability based on deep learning algorithm can remove the phase errors introduced by higher-order harmonics. An end-to-end deep convolutional neural network from noise phase to precise phase was constructed by this method and the phase error introduced by higher-order harmonics was reduced. Finally, high-speed and accurate 3D measurement could be achieved by this method. Firstly, the theoretical analysis proved the feasibility of the proposed method. Then, simulation and experiments were performed to further verify the effectiveness and accuracy of the proposed method. Compared with the existing high-speed 3D measurement methods, the proposed method can ensure measurement speed while ensuring measurement accuracy.
Optical devices
Study on depolarizers applied for a grating spectrometer
Tan Ting, Wu Tongzhou
2020, 49(7): 20190544.   doi: 10.3788/IRLA20190544
[Abstract](8) [FullText HTML](7) [PDF 4122KB](0)
The image quality of the grating spectrometer is often affected by the polarization characteristics of the incident light. In order to solve this problem, a depolarizer is usually added to the spectrometer to reduce the polarization response of the instrument. The birefringence property of the crystalline material can produce a depolarization effect on the optical principle, therefore it is often used to process into various types of depolarizers. Based on the principle of the matrix optics, the Muller matrix and residual polarization theoretical expression of a H-V depolarizer and a double Barbinet depolarizer were deeply discussed. The relationship among residual polarization of a double Barbinet depolarizer and working wavelength, its wedge angle, entrance pupil diameter and incident light polarization angle was given respectively. Based on these theories, a double Barbinet depolarizer applied for a grating spectrometer was developed. It could be obtained by calculation that when the wedge angle and the pupil diameter of the double Barbinet depolarizer was 0.6° and 20.6 mm respectively, the residual polarization of the depolarizer was better than 3% in the wavelength range of 0.4-0.9 μm. What’s more, the double image distance met the application requirements, so it can be widely used in engineering practice.
Radiation effects of 0.18 μm CMOS APS by proton irradiation
Cai Yulong, Li Yudong, Wen Lin, Feng Jie, Guo Qi
2020, 49(7): 20190433.   doi: 10.3788/IRLA20190433
[Abstract](41) [FullText HTML](40) [PDF 1229KB](8)
Complementary metal-oxide-semiconductor (CMOS) image sensors can easily be susceptible to proton irradiation in space applications. A proton irradiation experiment of a domestic commercial CIS was conducted on the ground, and the cumulative radiation effect and single event effect were studied by using offline and online image acquisition methods. The proton-induced cumulative radiation effects were studied by analyzing the dark signal degradation after irradiation, and histogram and generation mechanism of dark signals were analyzed from the aspects of total dose and displacement damage. Online testing results show that proton-induced single event transients in active pixel array include transient bright spot, transient bright cluster, and transient bright line. The interaction mechanism of proton and CIS was analyzed to discuss the different single event transient phenomena. No single event latch-up and single event function interruption in the peripheral circuits of the CIS was observed in the experiments.
Image processing
Image recognition method of anti UAV system based on convolutional neural network
Xue Shan, Zhang Zhen, Lv Qiongying, Cao Guohua, Mao Yiwei
2020, 49(7): 20200154.   doi: 10.3788/IRLA20200154
[Abstract](17) [FullText HTML](9) [PDF 2583KB](2)
In view of the serious impact and threat to public security of UAV's undocumented flight and random flight, an anti UAV system was proposed. Recognition of UAV is one of the key points in the realization of anti UAV system. An image recognition method based on convolutional neural network was proposed. The self-made optical system was used to collect images of different UAVs and birds, and convolutional neural network and support vector machine for UAV small sample recognition were designed. The convolution neural network was used to identify MNIST data set, UAV image and bird image respectively. At the same time, support vector machine was used to identify UAV and bird image, and the experiment was carried out. The experimental results show that the recognition accuracy of the convolutional neural network is 91.3% in MNIST data set, 95.9% in UAV recognition and 88.4% in support vector machine (SVM). The experimental results show that the proposed method can identify UAVs, birds and different types of UAVs, and the recognition result is better than that of SVM. It can be used for the identification of UAVs in anti UAV system, which provides reference for similar research.
Application of trust region method in infrared image sequence processing
Wan Litao, Xiong Nanfei, Wang Dong, Wang Zijun
2020, 49(7): 20190505.   doi: 10.3788/IRLA20190505
[Abstract](2723) [FullText HTML](1591) [PDF 7038KB](19)
In the process of collecting thermal images of infrared nondestructive testing (NDT) with light source as the excitation, due to the influence of uneven heating, environmental radiation and other factors, the collected thermal image sequence has problems such as high background noise, low contrast and poor display effect of defects, which are easy to cause the omission of defects. In order to improve the defect detection rate, infrared thermal image sequence processing technology based on Trust Region Reflective (TRR) algorithm was proposed. Firstly, the background noise surface with uneven heating was fitted by TRR algorithm, and the background surface obtained by fitting was subtracted from the original thermal images to remove the background noise caused by uneven heating. Then, Principal Component Analysis (PCA) algorithm was used to extract the defect feature information of the thermal image sequence after removing the background, so as to further improve the signal-to-noise ratio of the infrared thermal wave images. Finally, the defect region was segmented by region-growing algorithm. The experimental results show that a combination of these algorithms can effectively improve the signal-to-noise ratio of the infrared thermal image, thus improve the defect detection rate.
Lightweight feature fusion network design for local feature recognition of non-cooperative target
Xu Yunfei, Zhang Duzhou, Wang Li, Hua Baocheng
2020, 49(7): 20200170.   doi: 10.3788/IRLA20200170
[Abstract](15) [FullText HTML](8) [PDF 1678KB](2)
The Non-cooperative Detection Network(NCDN) model is a kind of local feature detection network based on lightweight convolution neural network. In SSD model, the feature fusion strategy was introduced to meet the detection requirements at different distances, and the robustness of the model to the reduction of local feature resolution caused by image scale transformation was improved; the number of convolution channels in mobilenetv2 was compressed with different compression ratios to obtain lightweight feature extraction network; local feature labeling and training of speed data were set to verify the applicable distance range of NCDN. The experimental results show that the mAP of the model can reach 0.90 within 45 m, and the accuracy loss of the model is only 5% after saving 75% of the calculation amount in channel compression. It meets the requirements of on orbit detection accuracy and calculation amount.
Optical fabricaion
Removal of the single point diamond turning marks by spiral sine trace bonnet polishing process
Wang Peng, Zhang Hao, Jia Yapeng, Yang Kun, Li Weihao
2020, 49(7): 20200212.   doi: 10.3788/IRLA20200212
[Abstract](23) [FullText HTML](11) [PDF 1814KB](5)
Single point diamond turing (SPDT) technology has been widely used in the high precision optical surface processing field. However, the micro-nano texture which is mainly composed of turning marks remain on the turned surface will affect performance of optical systems. Therefore, it’s necessary to remove the turning marks for improving the surface quality. Removal of the single point diamond turning marks was studied in the paper. It was found that the removal efficiency was highest when the polishing direction was perpendicular to the turning marks. A new polishing trace called spiral sine trace was presented based on the finding. The design principle was introduced in detail. Contrast experiment of different polishing tracks consisting of spiral sine trace, spiral trace and raster trace utilizing bonnet polishing was carried out. Result shows that the improvement effect of micro-nano texture in spiral sine trace was obviously superior to two other kinds of trace. A germanium aspherical surface manufactured by SPDT was smoothed by spiral sine bonnet polishing. The results shows that the roughness of surface Ra reduce from 1.28 nm to 0.4 nm before and after polishing, the regular turning marks transform to random micro-nano texture, and above all, the surface figure accuracy isn’t damaged during the smoothing process.
Processing technology of cutting ZnS crystal
Li Shijie, Xu Chao, Huang Yuetian, Wang Shouyi, Liu Weiguo
2020, 49(7): 20190567.   doi: 10.3788/IRLA20190567
[Abstract](10) [FullText HTML](3) [PDF 1689KB](4)
With the wide application of ZnS crystal optical elements in infrared optical system, the surface quality of ZnS crystal optical elements is more and more demanding, but due to the brittleness of the material, it is difficult to obtain high quality surface roughness. In order to obtain high quality surface of ZnS crystal, the principle of cutting and fly-cutting based on single point diamond lathe was introduced, as well as the factors affecting surface roughness. And then the influence of different parameters of diamond tool and different processing parameters on the surface roughness of ZnS flat element was studied by single variable method through process experiment. The quality of the machined surface was tested by microscope and white light interferometer, and the processing parameters were optimized by feedback. Finally, based on the optimal processing parameters, high quality ZnS flat optical elements with surface roughness Sa of about 1 nm were obtained in the both different methods. The results provide technical support for the development of high quality optical elements of ZnS crystal and have good engineering application value.
Special issue on infrared extinction technology
Research progress on artificially prepared infrared extinction materials and their extinction properties(Invited)
Gu Youlin, Lu Wei, Fang Jiajie, Zheng Chao, Chen Xi, Wang Xinyu, Hu Yihua
2020, 49(7): 20201018.   doi: 10.3788/IRLA20201018
[Abstract](2599) [FullText HTML](3025) [PDF 1109KB](16)
As an important means to weaken the performance of infrared imaging equipments or systems, artificially prepared infrared extinction materials have become the research object of many countries, and have achieved staged research results. The research status of artificially prepared infrared extinction materials is introduced from metal materials, expanded graphite, nano-materials, water-based foam, biomaterials and composite materials. The particle aggregation models of extinction materials such as particle and cluster, cluster and cluster are described. Several typical extinction calculation methods such as Mie scattering method, discrete dipole approximation method, T matrix method, and finite-difference time-domain method are introduced. According to the analysis, the infrared extinction materials prepared manually in the future will develop in the direction of long duration, low cost, various forms of release, environmental protection and non-toxic.
Development of anti-infrared smoke material and its extinction performance(Invited)
Wang Xuanyu
2020, 49(7): 20201019.   doi: 10.3788/IRLA20201019
[Abstract](10) [FullText HTML](7) [PDF 973KB](4)
In order to promote the research and application transformation of anti-infrared smoke screen materials, the research status, main problems and development trend of the materials were systematically analyzed from the material development and research on extinction performance. The results show that the research of carbon black and red phosphorus based hot smoke materials mainly focus on the improvement of the formula. The cold smoke materials, such as layered super-molecular, ultrafine ceramic powder, nano powder and biomaterials, have made remarkable achievements in structural design and synthesis technology. At present, there are some problems in the research, such as the lack of environment-friendly anti-infrared smoke screen materials, the difficulty of extinction theory innovation and so on. In the future, low cost-effectiveness ratio and environment-friendly anti-infrared smoke materials will become the development focus in this field.
Preparation of carbon coated ferromagnetic composite materials by one-pot and IR extinction performance(Invited)
Bao Lixia, Qiao Xiaojing, Yang Ming
2020, 49(7): 20201020.   doi: 10.3788/IRLA20201020
[Abstract](13) [FullText HTML](7) [PDF 1939KB](2)
Carbon coated ferrite precursor was prepared by one-pot hydrothermal method, which was calcined at 950 ℃ with N2 protection to obtain carbon coated ferromagnet composite materials. The morphology and composition of the materials were analyzed by XRD, FT-IR and SEM, and the effects of reaction time, the ratio of starch and glucose on the morphology and IR extinction of the composite were studied. The IR extinction coefficients of materials in the range of 2.5-25 μm were measured and calculated by KBr method of FT-IR. The results show that the samples have good morphology and extinction performance, that were prepared under the conditions of reaction time of 20 h and 18 h and the ratio of starch and glucose of 9:3 and 6:10. In the range of 4-10 μm, the extinction coefficient of sample 5 and 7 is greater than 0.3 m2/g and the maximum is 0.37 m2/g.
Infrared extinction properties of typical aerosol particles(Invited)
Shi Jiaming, Li Zhigang, Chen Zongsheng, Lv Xiangyin
2020, 49(7): 20201021.   doi: 10.3788/IRLA20201021
[Abstract](745) [FullText HTML](441) [PDF 1305KB](15)
Graphite and aluminum powders are typical aerosol particles whose infrared (IR) extinction properties are important to the IR obscuring performances of the smoke ammunitions containing these powders. Mass extinction coefficients (MECs) of the two materials with different sizes are measured in a smoke chamber. The relationship between the powder size and the IR extinction property is analyzed, with the difference between their extinction properties being discussed. Moreover, test accuracy is studied at different temperatures of the target and the background. The results show that the IR extinction property gets better as the size of the graphite powder decreases. Due to its better dispersivity, larger radius-thickness ratio and larger IR refractive index, aluminum powder shows better extinction properties than graphite powder of the same size. The IR MECs of aluminum powder (1 000 meshes) are respectively 1.78 m2/g (3.7- 4.8 μm) and 2.01 m2/g(7.5-14 μm), with those of graphite powder of the same size being 1.02 m2/g and 1.01 m2/g respectively. In addition, test results are found to be closely related to the initial temperatures of the target and the background, showing the necessity of appropriate settings of the temperature.
Analysis of extinction characteristics of sandstorm to infrared radiation(Invited)
Wang Hongxia, Sun Honghui, Zhang Qinghua
2020, 49(7): 20201022.   doi: 10.3788/IRLA20201022
[Abstract](13) [FullText HTML](6) [PDF 1667KB](5)
The extinction and attenuation characteristics of seven modes of sandstorm in China for 0.86 -20 μm band infrared radiation were analyzed based on Mie scattering theory and Monte Carlo method. The results show that for the small size dust particles, the extinction effect is mainly the result of scattering in the near and middle infrared, and for the large size dust particles, the infrared extinction is the result of absorption and scattering. The attenuation rate difference of single scattering and multiple scattering of sandstorm are compared. The attenuation rate of multiple scattering is less than that of single scattering under the same condition, and the difference decreases with the increase of visibility. The multiple scattering attenuation rate calculated based on Monte Carlo method is more comprehensive than the extinction coefficient to reflect the influence of sandstorm on infrared radiation intensity attenuation. The infrared attenuation intensity of six kinds of large particle mode sandstorm is greater than that of small particle mode sandstorm, and the attenuation rate increases with the increase of wavelength. The attenuation rate of the small particle mode duststorm fluctuates obviously with the change of wavelength, with a peak value in the range of 7.9–12.5 μm, and is not sensitive to the wavelength in the range of 13–20 μm.
Experimental study on extinction characteristics of aqueous foam(Invited)
Pan Gongpei, Du Xuefeng, Zhao Jun
2020, 49(7): 20201023.   doi: 10.3788/IRLA20201023
[Abstract](632) [FullText HTML](540) [PDF 2606KB](9)
Aqueous foam is widely used as a kind of stealth way in the scene of optoelectronic countermeasure. The existing optoelectronic jamming stealth technology has such problems as short acting time, single band and environmental pollution, which makes it difficult to effectively counter dual-mode and multi-mode precision guidance weapons. Aiming at the above problems, the aqueous foam formulation was studied. The extinction performance experiments of aqueous foam against visible light, infrared (3−5 μm, 8−14 μm), laser (1.06 μm, 10.6 μm), millimeter wave (3 mm, 8 mm) and centimeter wave (2 cm, 3 cm)were implemented. The shielding and interference effects of aqueous foam aiming at thermal imagery of 8−14 μm band were measured. The extinction mechanism of aqueous foam was discussed. The study shows that the curtain barrier formed by aqueous foam cloud or compositing with artificial fog is expected to acquire a new type of smokescreen weapon with the advantages such as full-wave band and environment friendly.
Invited paper
An upgraded combined atmospheric radiative transfer CART2(Invited)
Wei Heli, Dai Congming, Wu Pengfei, Tang Chaoli, Zhao Fengmei, Wu Xing, Rao Ruizhong, Wang Yingjian
2020, 49(7): 20201024.   doi: 10.3788/IRLA20201024
[Abstract](9) [FullText HTML](8) [PDF 2500KB](3)
Using the HITRAN2016 database, a new database of atmospheric molecular absorption coefficients was obtained by recalculating and fitting, which was applied to the upgraded 2nd edition of the Combined Atmospheric Radiative Transfer (CART2). A CART2P1 program module with a spectral resolution of 0.1 cm−1 has been added. Compared to CART 1.0, atmospheric molecular absorption takes into account weaker molecular absorption lines. The comparisons to LBLRTM between the calculated results of MODTRAN5 and CART showed that CART2 can accurately simulate the absorption of atmospheric molecules; the calculated results agree well with the real measured ground-based infrared high-resolution solar spectrum. The atmospheric transmittance and environmental background radiation calculated by CART2 with a finer 0.1 cm−1 spectral resolution can distinguish discrete atmospheric molecular absorption lines, which can be applied to radiative transfer calculations for medium-to-high spectral resolution optical engineering or some laser engineering.
Lasers & Laser optics
Status and development trend of high power slab laser technology
Wang Huihua, Lin Longxin, Ye Xin
2020, 49(7): 20190456.   doi: 10.3788/IRLA20190456
[Abstract](14) [FullText HTML](10) [PDF 1518KB](4)
As a typical high-power solid-state laser, high average power zigzag slab lasers achieved great progress in past two decades. Which fields got many innovations, such as face-pumped slab amplifier, multi-segment bonded slab structure, high-brightness pumped Yb: YAG slab amplifier and so on. This paper reviewed the technology progress of the slab lasers, including its design principles, transmission power amplification rules and various improvement methods for optimizing performance.On the basis of the general discussion on the laser power calibration capability of the slats, the technical development trend of improving the output power and beam quality was analyzed and discussed. It was expected that there will be considerable development space for high average power slab laser technology in the future.
Modeling research on angle measurement accuracy of four-quadrant detector of laser seeker
Qiu Xiong, Wang Shicheng, Liu Zhiguo, Xu Weibo
2020, 49(7): 20190453.   doi: 10.3788/IRLA20190453
[Abstract](10) [FullText HTML](10) [PDF 1254KB](4)
The accuracy of the four-quadrant detector on the target directly affects the guidance precision of the laser guided weapon. Therefore, it is very important to study the accuracy of the four-quadrant detector. In this paper, the method of computation and simulation analysis was adopted, based on the uniform distribution of the pulse peak power density at the entrance of the seeker, and the noise interference current obeyed the Gaussian distribution, and the beam deflection angle error model of the laser seeker was established; however, the beam deflection angle error had random probability due to noise interference, so the mean and standard deviation of the beam deflection angle error were used as the measurement of the four-quadrant detector angle measurement accuracy. The relationship was established between the mean and standard deviation of the beam deflection angle error and the optical parameters of the seeker, the spot radius, the incident angle of the diffuse reflection laser, the noise interference current, and the pulse peak power density at the entrance of the seeker. Taking the standard deviation of the deflection angle of the seeker beam as an example, the simulation analysis was carried out in combination with the application background.
Single-frequency laser based on single-pass QPM frequency doubling of Tm-doped fiber MOPA
Zhang Pengquan, Du Tiejun, Shi Yijun
2020, 49(7): 20200112.   doi: 10.3788/IRLA20200112
[Abstract](331) [FullText HTML](235) [PDF 1084KB](10)
In order to obtain a 0.9 μm near-infrared continuous-wave single-frequency laser output, a 50 mm long PPLN crystal was used to perform single-pass frequency doubling of the continuous-wave 1 925.08 nm single-frequency laser output of the Tm-doped fiber MOPA, and the temperature was matched by focusing parameters and quasi-phase optimized to achieve 96.95 nm second harmonic output up to 9.07 W at a fundamental optical power of 43.4 W, with a conversion efficiency of 20.9%.The second harmonic was in single longitudinal mode with M2 factors of 1.36 and 1.52 on x and y directions, respectively. The influence of focusing parameter and temperature on the conversion efficiency was experimentally investigated. The relationship between the focusing parameter and phase matching temperature acceptance was also discussed. The experimental results show that Tm-doped fiber laser quasi-phase matching one-way frequency doubling is an effective method to obtain 0.9 μm band continuous wave single frequency laser output.
Anti-interference temperature control for VCSEL laser
Han Tian, Zhang Yulin, Miao Cunxiao, Liu Jianfeng, Xue Shuai
2020, 49(7): 20190461.   doi: 10.3788/IRLA20190461
[Abstract](39) [FullText HTML](21) [PDF 1933KB](7)
Due to its low power consumption, small size, high modulation frequency and easy integration, VCSELs are widely used in the field of magnetic detection. As a high-precision sensor, the atomic magnetometer reduces the measurement accuracy due to the unstable output of the laser during the measurement of the magnetic field. A controller that can resist change in ambient temperature was designed to deal with the instability of the output of the laser due to environmental disturbance. Firstly, the high-resolution temperature solution was realized by the ADAU1401A chip with DSP core and DPSD method. Then the temperature control mathematical model was established by means of system identification. Finally, the disturbance observer and internal model control principle were applied to design anti-disturbance and low overshoot robust controller. The experimental results show that the control accuracy of interference is ±0.003 °C at 70 °C, and the control accuracy is ±0.001 5 °C at room temperature, which lays a foundation for stable output of laser and high-precision magnetic field measurement.
Laser & laser optics
Miniaturized mid-infrared MgO: PPLN optical parametric oscillator with high beam quality
Bai Xiang, He Yang, Yu Deyang, Zhang Kuo, Chen Fei
2020, 49(7): 20190512.   doi: 10.3788/IRLA20190512
[Abstract](11) [FullText HTML](7) [PDF 1252KB](3)
In order to meet the engineering application of mid-infrared laser, a miniaturized mid-infrared MgO: PPLN optical parametric oscillator (MgO: PPLN-OPO) with high beam quality was presented. The pump source was an acousto-optical Q-switched Nd: YVO4 laser. By pumping the MgO: PPLN crystal, the mid-infrared laser with high efficiency and high peak power was obtained. And the mid-infrared beam quality was improved by adding an aperture in the cavity. The whole laser was cooled by thermoelectric cooling and air cooling. Therefore, the size of the laser was miniaturized. Experimental results indicate that the acousto-optical Q-switched Nd: YVO4 laser can realize the pulse laser with the highest power of 9.3 W at 1.064 μm. The corresponding optical to optical conversion efficiency is 27.2% and the peak power is ~27.5 kW. With the Nd: YVO4 laser pump, the MgO: PPLN-OPO can output the pulse laser at 3.765 μm. When adding the aperture in the cavity, the maximum output power of the MgO: PPLN-OPO decreases from 1.20 W to 1.08 W. However, the beam quality improves obviously. The Mx2 and My2factors change from 1.89 and 1.98 to 1.20 and 1.29, respectively. The pulse width and the peak power of mid-infrared laser are 8.4 ns and ~4.3 kW, respectively.