Journals >Infrared and Laser Engineering
Contents
2019
Volume: 48 Issue 9
39 Article(s)
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Visible light optical coherence tomography in biomedical imaging
Ji Yi
Optical coherence tomography (OCT) is a widely used optical imaging modality for three-dimensional structural and functional imaging. The prevalent OCT systems use an invisible light laser source beyond 800 nm and up to 1 500 nm to allow deep image penetration in biological tissues. Recently, visible light OCT (vis-OCTOptical coherence tomography (OCT) is a widely used optical imaging modality for three-dimensional structural and functional imaging. The prevalent OCT systems use an invisible light laser source beyond 800 nm and up to 1 500 nm to allow deep image penetration in biological tissues. Recently, visible light OCT (vis-OCT) using a short wavelength range between 400 nm to 700 nm has gained significant progress and attracted interest in its unique capability of high resolution imaging and spatially-resolved spectroscopy. In this article, we will briefly review the recent advance of vis-OCT imaging and its potential biomedical applications..
Infrared and Laser Engineering
- Publication Date: Jan. 01, 1900
- Vol. 48, Issue 9, 902001 (2019)
Research on InP-based HEMT terahertz detector enhanced by bow-tie antenna at room temperature
Li Jinlun, Cui Shaohui, Zhang Jing, Zhang Zhenwei, Zhang Bowen, Ni Haiqiao, and Niu Zhichuan
InP-based HEMT samples were prepared by molecular beam epitaxy(MBE). The sample mobility at room temperature reached 10 289 cm2/(V·s). The terahertz detector coupled with a bow-tie antenna was fabricated by photolithography, etching, magnetron sputtering, spot welding. The bow-tie antenna used in the device was opInP-based HEMT samples were prepared by molecular beam epitaxy(MBE). The sample mobility at room temperature reached 10 289 cm2/(V·s). The terahertz detector coupled with a bow-tie antenna was fabricated by photolithography, etching, magnetron sputtering, spot welding. The bow-tie antenna used in the device was optimized by simulation with HFSS, so that the optimized antenna parameter of S11 was -40 dB, the voltage standing wave ratio(VSWR) was 1.15, gain was 6 dB and impedance matching with the two-dimensional electronic gas(2DEG) channel. The device was measured by VDI′s 0.3 THz Schottky diode terahertz source. The measurement results show that the device noise equivalent power (NEP) is 4 nW/Hz1/2 at room temperature, and the detection response rate is 46 V/W, the device response time is better than 330 μs..
Infrared and Laser Engineering
- Publication Date: Jan. 01, 1900
- Vol. 48, Issue 9, 919001 (2019)
High power 110 GHz balanced Schottky diode frequency doubler
Tian Yaoling, He Yue, Huang Kun, Jiang Jun, and Miao Li
Generation of power at higher terahertz frequencies typically requires several stages of multiplication, which put forward the demand for high power devices at earlier stages. For higher power capacity and efficiency, the doubler circuit was realized based on ceramic substrates with high thermal conductivity. Moreover,Generation of power at higher terahertz frequencies typically requires several stages of multiplication, which put forward the demand for high power devices at earlier stages. For higher power capacity and efficiency, the doubler circuit was realized based on ceramic substrates with high thermal conductivity. Moreover, with the accurate Schottky diode equal model, a high power 110 GHz balanced doubler was analyzed and designed in HFSS and ADS using symmetry boundary condition. With an input power of 28 dBm, the measured results showed that the maximum output power and efficiency of the doubler range from 102 to 114.2 GHz are 108 mW and 17.6% respectively, providing sufficient power for the chain..
Infrared and Laser Engineering
- Publication Date: Jan. 01, 1900
- Vol. 48, Issue 9, 919002 (2019)
Measurement of minority carrier lifetime in silicon by high speed terahertz detector
Zhang Zhao, Chen Xieyu, and Tian Zhen
Using pulse trigger signal to generate non-equilibrium carriers in semiconductor, a method for minority carrier lifetime mapping of semiconductor was proposed, with the aid of a terahertz continuous wave source and an ultrafast-response probe, which can apply for characterizing transient carrier dynamics in semiconductUsing pulse trigger signal to generate non-equilibrium carriers in semiconductor, a method for minority carrier lifetime mapping of semiconductor was proposed, with the aid of a terahertz continuous wave source and an ultrafast-response probe, which can apply for characterizing transient carrier dynamics in semiconductor. Based on the above-mentioned design principles, a non-contact minority carrier lifetime measuring system was set up by using the optical pump as the periodic excitation, whose time window was from nanosecond to second and temporal resolution was the order of nanosecond. The system owned various advantages, such as simple device, convenient operation and low cost. The non-equilibrium minority carrier lifetime of monocrystalline silicon with different doping types, different doping concentration, and different thickness were measured by using our system. Finally, the photo-generated carrier lifetime of the monocrystalline silicon was measured through changing the optical pump power. Result shows that the minority carrier lifetime of monocrystalline silicon increases with the enhancement of pump power. The wide-working-window and high-time-resolution detection of terahertz fast processes, which is realized by the proposed system, can be applied for the fast imaging and rapid bio-response detection at the terahertz range..
Infrared and Laser Engineering
- Publication Date: Jan. 01, 1900
- Vol. 48, Issue 9, 919003 (2019)
[in Chinese]
Preliminary application of stellar occultation in the near-space
Sun Mingchen, Tu Cui, Hu Xiong, Gong Xiaoyan, and Guo Wenjie
Atmospheric stellar occultation technology can detect information about the density of various trace components and atmospheric temperature and so on in the planetary atmosphere. The above parameters were obtained by using the atmospheric transmittance. An occultation model was established based on the principle of steAtmospheric stellar occultation technology can detect information about the density of various trace components and atmospheric temperature and so on in the planetary atmosphere. The above parameters were obtained by using the atmospheric transmittance. An occultation model was established based on the principle of stellar occultation. The spectral absorption characteristics of gas molecules were analyzed, and then transmittance of various atmospheric components were obtained through simulating how it worked by model. The atmospheric component density was obtained by inversion of atmospheric transmittance and this model was verified through the comparison of MSISE-00. The results of the two were in good agreement. Furthermore, the signal-to-noise ratio and relative error of the spectrum were estimated, and signal-to-noise ratio and relative error about different stars were discussed, and then the range of magnitude of the target stars was given. The preliminary results show that the target stars in the range of -1.45-3.55 is used as the light source for detection, the signal-to-noise ratio is above 100, and the relative error of measurement is as low as 1%. The results of this paper provide preliminary theoretical guidance for the development of stellar occultation detection in the near-space of the Earth and other planetary..
Infrared and Laser Engineering
- Publication Date: Jan. 01, 1900
- Vol. 48, Issue 9, 909001 (2019)
[in Chinese]
Test method of stray light on mirror surface of laser gravitational wave telescope
Xu Jiesu, Hu Zhongwen, Xu Teng, Li Honglan, Li Qian, and Yao Mengyuan
The source of stray light of the laser gravitational wave telescope is mainly the reflected stray light generated by the thin beam incident on the mirror surface. When the laser light intensity of 1 W was incident, the stray light intensity needs to be suppressed to less than 10-10 W, otherwise the measurement accuracyThe source of stray light of the laser gravitational wave telescope is mainly the reflected stray light generated by the thin beam incident on the mirror surface. When the laser light intensity of 1 W was incident, the stray light intensity needs to be suppressed to less than 10-10 W, otherwise the measurement accuracy of the main parameter optical path difference will be seriously affected. Aiming at the background of this application, the feasibility of Bidirectional Reflection Distribution Function(BRDF) parameters for mirror surface reflection characteristics reconstructed by stray light test data was considered when the thin beam incident on the mirror surface. In the traditional measurement of BRDF, four corners were required. The system was complex and inconvenient for real-time application. Based on the isotropic optical elements and the symmetry of mirror stray light model, considering the plane mirror, curved mirror and beam diffraction effect, measurement error and other factors, a method reconstructing the BRDF parameters by one-dimensional measurement the scattering of several points with the plane mirror rotation in the meridian plane was proposed, and the feasibility and measurement accuracy were verified by numerical methods..
Infrared and Laser Engineering
- Publication Date: Jan. 01, 1900
- Vol. 48, Issue 9, 913001 (2019)
Time-varying periodic disturbance suppression of laser seeker testing system based on spatial iterative learning control
Huo Xin, Wu Aijing, Wang Mengyu, and Xing Baoxiang
The laser seeker testing system is a special testing equipment for the parameter calibration and performance testing of the laser seeker. Its performance and precision determine the quality of the seeker. In order to improve the performance of a laser seeker testing system and restrain the influence of time-varying perThe laser seeker testing system is a special testing equipment for the parameter calibration and performance testing of the laser seeker. Its performance and precision determine the quality of the seeker. In order to improve the performance of a laser seeker testing system and restrain the influence of time-varying periodic disturbance on the testing system, an iterative learning control method based on spatial domain was proposed. By analyzing the time-domain and position-domain spectrum of the disturbance components at different velocities, it was obtained that periods of the disturbances were time-varying but position-fixed. Based on the idea of iterative learning, an iterative learning control structure of the spatial domain was carried out. According to the convergence condition of the algorithm and the phase delay characteristic of the filter, the control parameter principles were derived and the phase compensation methods were demonstrated. Its application effect was verified by experiments. The experiment under the command of maximum rotation speed shows that the steady-state tracking error of angular position is decreased by 65.8%, and further, the corrected steady-state tracking error of angular position is decreased by 61.5% after adopting the iterative learning control method of spatial domain..
Infrared and Laser Engineering
- Publication Date: Jan. 01, 1900
- Vol. 48, Issue 9, 913002 (2019)
Phase unwrapping method based on dual-frequency heterodyne combined with phase encoding
Han Xu, Wang Lin, and Fu Yanjun
In order to complete phase unwrapping with a heterodyne of high frequency fringe and achieve high accuracy measurement, a phase unwrapping method of dual frequency heterodyne combined with phase coding was proposed. Firstly, two wrapping phases were obtained by two sinusoidal stripes, and one heterodyne phase was obtaiIn order to complete phase unwrapping with a heterodyne of high frequency fringe and achieve high accuracy measurement, a phase unwrapping method of dual frequency heterodyne combined with phase coding was proposed. Firstly, two wrapping phases were obtained by two sinusoidal stripes, and one heterodyne phase was obtained by heterodyne processing; Secondly, the phase coding fringe was used to obtain the fringe order, and the heterodyne phase was unwrapped by fringe order; Finally, the two wrapping phases were unwrapped by continuous heterodyne phases, and the phase information of the object was obtained by using the continuous phase of the highest frequency. The experimental results show that the RMS error of the measurement is 0.038 mm. The period of dual-frequency heterodyne synthesis did not need to cover the whole field of view, thus breaking the limitation of frequency selection in traditional dual-frequency heterodyne method, which could be used for high accuracy measurement with higher frequency fringes. High frequency fringe can be used for high accuracy measurement even if there is error of phase principal value..
Infrared and Laser Engineering
- Publication Date: Jan. 01, 1900
- Vol. 48, Issue 9, 913003 (2019)
Optical parameters measurement of infrared filter based on envelope-full spectral fitting inversion method
Li Kaipeng, Wang Jizhou, Wang Duoshu, Wang Yunfei, and Dong Maojin
The high performance measuring methods to measure the optical parameters of infrared band-pass filter with complex multilayer were significantly important to improve the design and technology of the infrared filter development. Firstly, the traditional spectral measurement methods were fully analyzed, and an envelope-fThe high performance measuring methods to measure the optical parameters of infrared band-pass filter with complex multilayer were significantly important to improve the design and technology of the infrared filter development. Firstly, the traditional spectral measurement methods were fully analyzed, and an envelope-full spectral fitting inversion method was proposed. The basic idea, physical model and optimization algorithm of the new method were discussed in detail. Secondly, a technique for fabricating a single-layer film and infrared filter with high transmittance and wide cut-off medium-band bandpass in the 2 000-8 000 nm spectral range was designed, and the experiments to compare the difference between the actual spectrum and the spectrum calculated with the optical parameters measured by the new method were performed. The results show that the new method not only has very high precision performance, but also can identify the quality of the film process and can determine the dispersion of the film by the measurement results. The another set of experiments on the measurement of optical parameters of infrared filter illustrates that, compared with traditional full spectrum fitting inversion method, the new method not only has high-precision measurement results, but also can quickly and accurately locate the divergence between the actual plating thickness and the design thickness with the measured optical parameters, then a better high-performance infrared filter was developed..
Infrared and Laser Engineering
- Publication Date: Jan. 01, 1900
- Vol. 48, Issue 9, 913004 (2019)
[in Chinese]
Underwater LED optical communication technology of real-time error detection
Ye Demao, Liu Yuan, Wang Yantao, and Wang Yongjin
In order to reduce the influence of error coming from installation of communication terminals and pointing error of maneuvering targets in underwater working environment, the structure of underwater optical communication system was given. The light spot recognition and positioning algorithm based on intelligent bubble In order to reduce the influence of error coming from installation of communication terminals and pointing error of maneuvering targets in underwater working environment, the structure of underwater optical communication system was given. The light spot recognition and positioning algorithm based on intelligent bubble elimination was proposed. The effect of bubbles on link stability of underwater optical communication was well solved. The simulation results show that the algorithm has good robustness. Considering the characteristics of low attenuation in blue and green spectrum under water, an emission scheme of six lamps (central wavelength λ=450 nm) based on beam combination was designed, and a link model based on error parameters was proposed. In the simulation channel environmentof pure sea water, the experimental results show that the receiving power of the receiver was more than -20 dBm through 50 m channel attenuation when the distribution of transmitted light intensity was the flat-top and the divergence angle was less than 10°. Meanwhile, the eye diagram opened well. Otherwise, the performance dropped sharply..
Infrared and Laser Engineering
- Publication Date: Jan. 01, 1900
- Vol. 48, Issue 9, 918001 (2019)
Simulation analysis of the influence of various parameters on output pulse distortion of group velocity control in microring resonator
Liu Xin, Kong Mei, Xu Yameng, and Wang Xueping
When using microring resonators to realize group velocity control, the influences of various parameters on optical pulse transmission cannot be neglected. The parameters lead to the pulse broadening and the pulse distortion. The expressions of the second-order and third-order dispersions in single ring resonator were dWhen using microring resonators to realize group velocity control, the influences of various parameters on optical pulse transmission cannot be neglected. The parameters lead to the pulse broadening and the pulse distortion. The expressions of the second-order and third-order dispersions in single ring resonator were derived based on the transmission characteristics of the microring resonator. Aiming at the resonator without loss/gain, the pulse distortions resulted from the higher-order dispersions and the input pulse center wavelength were analyzed, during using microring resonator to realize the control of the group velocity. In addition, the influence of loss/gain on output pulse distortion of single ring resonator was derived. The results show that the second-order dispersion leads to pulse broadening and the third-order dispersion is accounted for the pulse distortion and the position of the central wavelength of the input pulse affects the depth of the pulse splitting bottom while the loss and gain affect the pulse distortion. This work provides design basis for applications of microring resonators in group velocity control..
Infrared and Laser Engineering
- Publication Date: Jan. 01, 1900
- Vol. 48, Issue 9, 918002 (2019)
All-optical phase regeneration in free-space optical communication networks
Sun Yue, Huang Xinning, Wen Yu, and Xie Xiaoping
Based on the application requirements of high-speed optical data multi-hop transmission in free-space optical communication network, and aiming at the problem that the signal quality of phase-modulated laser link after long-distance transmission in space degraded, the all-optical phase regeneration for binary phase shiBased on the application requirements of high-speed optical data multi-hop transmission in free-space optical communication network, and aiming at the problem that the signal quality of phase-modulated laser link after long-distance transmission in space degraded, the all-optical phase regeneration for binary phase shift keying modulated high-rate signal, based on the phase-sensitive four-wave mixing (FWM) effect in high nonlinear fiber (HNLF) was proposed. Numerical analysis with Matlab was carried out to find out the factors affecting the regeneration results. Then based on the OptiSystem simulation tool, an all-optical phase regeneration system for a 10 Gbit/s differential phase shift keying (DPSK) optical signal was constructed. Combining the link budget for geosynchronous (GEO) to optical ground station (OGS), system performance in three situations, namely back-to-back (B2B), phase-noised as well as noised-and-regenerated, were compared and analyzed. Simulation results and numerical analysis results show that compared with the system without regeneration after degradation, the bit-error-ratio (BER) of the noised-and-regenerated system improves nearly 4 orders of magnitude, while the output optical signal-to-noise-ratio (OSNR) increases nearly 3 dB. The results indicate that all-optical phase regeneration in free-space optical communication system can achieve all-optical phase regeneration of phase modulation signal. It can effectively promote the performance of spatial coherent laser communication system and can be used in the all-optical data relay of high speed free-space optical communication network relay nodes..
Infrared and Laser Engineering
- Publication Date: Jan. 01, 1900
- Vol. 48, Issue 9, 918003 (2019)
Design of free space optical communication system based on Raptor10 code
Ao Jun, Tan Xinyuan, Ma Chunbo, and Tang Chengpeng
Atmospheric turbulence is a major limiting factor in free-space optical communication systems, causing intensity flicker and phase fluctuations in the beam. In order to cope with the influence of atmospheric turbulence and background light on wireless laser communication, a wireless laser communication system was desigAtmospheric turbulence is a major limiting factor in free-space optical communication systems, causing intensity flicker and phase fluctuations in the beam. In order to cope with the influence of atmospheric turbulence and background light on wireless laser communication, a wireless laser communication system was designed and implemented. The system used the digital fountain code Raptor10 code to improve the reliability and anti-interference ability of the communication system. In addition, the Barker code was used as the frame header and pulse position modulation(PPM) mode, and the data coding, modulation, frame synchronization, demodulation and decoding were completed with the field programmable gate array(FPGA) as the core. The emission source was a 532 nm laser and the detector used a single point APD from Silicon Sensor. Finally, the entire wireless laser communication system was tested in 2 km of free space, and the test results were stable and reliable..
Infrared and Laser Engineering
- Publication Date: Jan. 01, 1900
- Vol. 48, Issue 9, 918004 (2019)
Optimum design for comb-index core fiber with large mode area
Miao Xiaofang, Wu Peng, and Zhao Baoyin
The wave-guide structure of the large mode area fiber with a comb-index core was optimized by adding a high refractive index platform in the outer layer of the fiber core, which provided a performance promotion on the parameters of mode field area, mode field distribution and bending resistance. The simulation results The wave-guide structure of the large mode area fiber with a comb-index core was optimized by adding a high refractive index platform in the outer layer of the fiber core, which provided a performance promotion on the parameters of mode field area, mode field distribution and bending resistance. The simulation results show that the optimized refractive index distribution increases the fiber′s mode field area by more than 700 μm2, and reduces bending loss of the fundamental mode from 6 dB/m to 0.1 dB/m at the same bending radius compared with the original comb-index distribution. Moreover, the mode field distributions including Gauss-like distribution, flattened distribution and hollow distribution, can be obtained by simply modulating the refractive-index parameters of the outermost platform, which may meet the needs of special laser processing industry..
Infrared and Laser Engineering
- Publication Date: Jan. 01, 1900
- Vol. 48, Issue 9, 918005 (2019)
Optimization design of bending performance for ultralow loss hole assisted fiber
She Yulai, Zhou Dejian, and Chen Xiaoyong
A two-dimensional axisymmetric finite element model for fiber bending was established. The fiber bending performance was analyzed by finite element method. The fiber bending loss, the effective mode field area and the splice loss were calculated respectively. The multi-objective orthogonal optimization was combined witA two-dimensional axisymmetric finite element model for fiber bending was established. The fiber bending performance was analyzed by finite element method. The fiber bending loss, the effective mode field area and the splice loss were calculated respectively. The multi-objective orthogonal optimization was combined with gray relational analysis method in the design for fiber bending performance which was carried out taking the bending loss and splice loss as objective functions, taking the distance b from the core to the trench, the width of trench c, the depth of trench Δt and the radius of air holes r as design variables. The results show that the bending loss of optimized fiber decreases from 0.127 8 dB/m to 1.749 8×10-4 dB/m, the effective mode field area of optimized fiber decreases from 94.741 μm2 to 82.37 μm2, the splice loss of optimized fiber reduces from 0.174 3 dB to 5.805×10-4 dB. Compared with the standard single-mode fiber, it is found that the effective mode area of the proposed fiber decreases from 209.21 μm2 to 82.3 μm2 with the bend radius of 3 mm and the splice loss decreases from 7.535 8 dB to 5.805×10-4 dB. The proposed fiber can also ensure the transmission quality of the system in the case of small bending radius..
Infrared and Laser Engineering
- Publication Date: Jan. 01, 1900
- Vol. 48, Issue 9, 918006 (2019)
[in Chinese]
Coupling implementation of pixel polarization imaging system
Li Jiaxin, Bai Tingzhu, Cui Zhigang, Song Cuifen, and Cheng Zeming
The coupling technology of the pixel polarization imaging system was studied by aligning the pixel polarizer array with the CCD photosensitive element. Aiming at the problem that the polarizer group array and CCD size do not match, a variety of process methods were used for processing, and a complete coupling alignmentThe coupling technology of the pixel polarization imaging system was studied by aligning the pixel polarizer array with the CCD photosensitive element. Aiming at the problem that the polarizer group array and CCD size do not match, a variety of process methods were used for processing, and a complete coupling alignment process was proposed. The imaging system developed in this paper can obtain four Stokes components with different polarization directions through one imaging detector. After operation and post-processing, it could also obtain the linear polarization image and the linear polarization angle image of the captured object, which realized the polarization enhancement of the image. The required polarization image facilitates the acquisition of target information in a complex environment..
Infrared and Laser Engineering
- Publication Date: Jan. 01, 1900
- Vol. 48, Issue 9, 925001 (2019)
Single-pixel imaging experiment through 34 km horizontal atmosphere
Li Mingfei, Kan Baoxi, Huo Juan, Yan Lu, and Liu Yuanxing
Experimental setup of long distance and high resolution single-pixel imaging system was set up. Images of natural target were obtained through 34 km outdoors horizontal atmosphere in daylight, about 0.8 m resolution was achieved. The multiple resolution level of Hadamard matrix was used as measurement basis, and owing Experimental setup of long distance and high resolution single-pixel imaging system was set up. Images of natural target were obtained through 34 km outdoors horizontal atmosphere in daylight, about 0.8 m resolution was achieved. The multiple resolution level of Hadamard matrix was used as measurement basis, and owing to 25% compressive sampling and differential measuring by two photon-multiplier tubes, video frame rate of 2 Hz@128×128 pixels was achieved with the proposed hardware and fast Walsh transform algorithm. An signal-to-noise ratio(SNR) was defined based on human-computer interaction interface to estimate the qualities of the recovered images. The relationship between image qualities and exposure times were researched. The proposed scheme has the potential application in long distance and high resolution infrared imaging with low cost setup..
Infrared and Laser Engineering
- Publication Date: Jan. 01, 1900
- Vol. 48, Issue 9, 925002 (2019)
[in Chinese]
Study on the mechanism of dark current degradation of HgCdTe photovoltaic devices induced by γ-irradiation
Wang Zhiming, Zhou Dong, Guo Qi, Li Yudong, Wen Lin, Ma Lindong, Zhang Xiang, Cai Yulong, and Liu Bingkai
Aiming at the problem that the infrared detector is degraded by the high-energy particle irradiation in the space application, the effect of γ-ray on the dark current of the medium-wave HgCdTe photovoltaic device was studied. The HgCdTe device was irradiated with 60Co-γ rays at room temperature and 77 K. After the irraAiming at the problem that the infrared detector is degraded by the high-energy particle irradiation in the space application, the effect of γ-ray on the dark current of the medium-wave HgCdTe photovoltaic device was studied. The HgCdTe device was irradiated with 60Co-γ rays at room temperature and 77 K. After the irradiation test, the low temperature irradiated device was subjected to 77 K low temperature annealing and room temperature annealing. By comparing the I-V characteristics, R-V characteristics and zero-bias dynamic resistance R0 parameters of the device before and after irradiation, the influence mechanism of γ-irradiation on the dark current of the HgCdTe device was analyzed. The test results show that the dark current of the device does not show obvious degradation after irradiation at room temperature under the total dose of 7 mrad(Si). Under 77 K temperature irradiation conditions, the dark current of the device increases with the dose, and the dark current degradation amplitude is related to the bias during the irradiation test. Studies have shown that the degradation of dark current was caused by gamma irradiation causing ionization damage in the device, resulting in an increase in the interface state and hole trap charge density in the device's CdTe passivation layer..
Infrared and Laser Engineering
- Publication Date: Jan. 01, 1900
- Vol. 48, Issue 9, 916001 (2019)
Influence of thin-film residual stress and surface impurities on fatigue life of deformable mirror
Yu Xia, Wang Jiaqiu, and Zhang Bin
Considering the influence of the thin-film residual stress and surface impurities of deformable mirrors (DMs), the stress analysis model of the DM with high reflectivity films was built up by the use of the finite element analysis software ANSYS. The fatigue damage characteristics of the DM for wavefront correction proConsidering the influence of the thin-film residual stress and surface impurities of deformable mirrors (DMs), the stress analysis model of the DM with high reflectivity films was built up by the use of the finite element analysis software ANSYS. The fatigue damage characteristics of the DM for wavefront correction process were analyzed based on the stress-cycle (S-N) curve and the Miner cumulative damage theory, and the influence of the thin-film residual stress and the surface impurity size on the fatigue life of the DM was discussed in detail as well. The results indicate that, under the condition of the thermal-mechanical coupling, the fatigue damage of the DM tends to speed up due to the thermal effect. For a given distortion wavefront to be corrected, the dynamic cyclic load of the DM is stronger with the increasing thin-film residual stress of the DM, and the fatigue life is shorter simultaneously. Besides, the residual stress mainly affects the fatigue life on the surface of the DM. For the given thin-film residual stress of the DM, the fatigue life also decreases due to larger surface stress caused by the increasing PV value of the distortion wavefront. When the surface impurities are irradiated by the high-power continuous laser, and are above a certain size, the fatigue life of the DM decreases with the increasing impurity size. However, the fatigue life of the DM is rarely affected when the sizes of the impurities are smaller enough. Furthermore, the thin-film residual stress will further increase the fatigue damage of the DM caused by surface impurities..
Infrared and Laser Engineering
- Publication Date: Jan. 01, 1900
- Vol. 48, Issue 9, 916002 (2019)
Influence of temperature gradient on thermal stability tolerance of large aperture reflective mirror
Yang Xun, Xu Shuyan, Li Xiaobo, Zhang Xusheng, and Ma Hongcai
In order to investigate the influence of temperature on the radius of curvature and the RMS value of the large aperture SiC reflective mirror, a finite element model was established for a 2 m-aperture SiC primary mirror of a space telescope, and the effects of uniform temperature field, axial temperature gradient and rIn order to investigate the influence of temperature on the radius of curvature and the RMS value of the large aperture SiC reflective mirror, a finite element model was established for a 2 m-aperture SiC primary mirror of a space telescope, and the effects of uniform temperature field, axial temperature gradient and radial temperature gradient on the radius of curvature and RMS of the mirror were analyzed. The accuracies of the simulation method and results were verified by experiment theoretical arithmetic. The results show that the influence of temperature gradient on the radius of curvature and the RMS value of the mirror is much greater than the effect of uniform temperature. The change of curvature radius is most sensitive to the axial temperature gradient, and the RMS value of the surface figure is most sensitive to the radial temperature gradient. The change in radius of curvature caused by the 1 ℃ axial temperature gradient is 48 times greater than the change in radius of curvature caused by the same uniform temperature rise. The RMS of surface figure caused by the ±1 ℃ radial temperature gradient can be 202 times larger than that caused by the same uniform temperature rise. The influence of axial temperature gradient and radial temperature gradient on the thermal stability tolerance must be considered in determining the thermal control index of the mirror..
Infrared and Laser Engineering
- Publication Date: Jan. 01, 1900
- Vol. 48, Issue 9, 916003 (2019)
Design of diffractive optical element based on discrete sampling encryption algorithm
Li Meixuan, Li Hong, Zhang Siqi, Zhang Wenying, and Guo Ming
In order to meet the high uniformity and different illumination mode requirement of the mask plane of the immersion lithography illumination system, the illumination mode converter system was studied. Diffractive Optical Elements (DOE) were used to generate various illumination modes, started from grating structure, thIn order to meet the high uniformity and different illumination mode requirement of the mask plane of the immersion lithography illumination system, the illumination mode converter system was studied. Diffractive Optical Elements (DOE) were used to generate various illumination modes, started from grating structure, the process of converting the grating into DOE by two-step transformation was analyzed. And a discrete sampling encryption algorithm was proposed. By examples of quadrupole illumination DOE with sampling width 1-5 μm, the correspondence relationship between the DOE feature size, diffraction efficiency and the intensity distribution non-uniformity was disclosed. The design results show that as the sampling line width decreases, the diffraction efficiency and uniformity of the shaped beam will be greatly improved. The 16-step illumination mode conversion DOE with feature size of 1.76 ?滋m×1.76 ?滋m was fabricated by contact lithography.The optical non-uniformity and diffraction efficiency of DOE under different illumination modes were tested by setting up an optical test platform. The results meet the design requirements and verify that the discrete sampling encryption algorithm can effectively guide the design of the DOE for the illumination mode transformation system..
Infrared and Laser Engineering
- Publication Date: Jan. 01, 1900
- Vol. 48, Issue 9, 916004 (2019)
Design and fabrication of an etching diffraction grating based on photonic crystal reflection mirrors
Yuan Pei, Wang Yue, Wu Yuanda, An Junming, Zhang Jiashun, and Zhu Lianqing
As wavelength division multiplexing/de-multiplexing devices, etching diffraction gratings (EDGs) are promising to be widely used in the optical communication systems. A new kind of EDG was designed and fabricated on silicon on insulator (SOI) platform with top silicon layer of 220 nm, which applied hexagonal-lattice aiAs wavelength division multiplexing/de-multiplexing devices, etching diffraction gratings (EDGs) are promising to be widely used in the optical communication systems. A new kind of EDG was designed and fabricated on silicon on insulator (SOI) platform with top silicon layer of 220 nm, which applied hexagonal-lattice air-hole photonic crystals as its reflection mirrors. Simulated results show that compared with the traditional EDGs based on stepped-grating reflection mirrors, the EDG based on photonic-crystal reflection mirrors could reduce the fabrication difficulty, decrease the insertion loss and realize the polarization maintenance theoretically. Afterwards, the EDG based on photonic-crystal reflection mirrors was fabricated with one step of deep ultraviolet lithography (DUVL) and one step of inductively coupled plasma (ICP) etching. The measured results show that the insertion loss of the device is 9.51-11.86 dB, and the crosstalk of it is 5.87-8.72 dB, which can be further improved by optimizing its fabrication process and optimizing the location of the output waveguides..
Infrared and Laser Engineering
- Publication Date: Jan. 01, 1900
- Vol. 48, Issue 9, 916005 (2019)
[in Chinese]
Modeling of spectrum irradiance distribution in the optical axis of underwater light sources
Hu Bo, Wu Chaopeng, Yang Yong, Zhang Xu, Song Hong, and Tao Jun
A model for spectrum irradiance distribution with respect to the distance in the optical axis of underwater light sources was proposed based on the theory on light propagation and the attenuation of water on light. Model structure was built from physics and unknown parameters were determined by numerical methods. By utA model for spectrum irradiance distribution with respect to the distance in the optical axis of underwater light sources was proposed based on the theory on light propagation and the attenuation of water on light. Model structure was built from physics and unknown parameters were determined by numerical methods. By utilizing the specific structure of the model, an identification approach was proposed where independent parameters were determined in different steps. The procedures for parameter identification were given in details. To validate the accuracy of the model and the feasibility of parameter identification, the model was further tested with underwater measurement data of an artificial light source. Results show that the model estimation is quite close to the measurement data and the root-mean-square value of the modeling error is only 4% of the measurement data, thus indicating high accuracy of the model. Application of this method can be found in modeling of underwater light field and underwater image processing..
Infrared and Laser Engineering
- Publication Date: Jan. 01, 1900
- Vol. 48, Issue 9, 910001 (2019)
[in Chinese]
Review of on-orbit radiometric calibration technology used in infrared remote sensors
Sheng Yicheng, Dun Xiong, Jin Weiqi, Guo Yixin, Zhou Feng, and Xiao Si
With the growing demand of quantitative remote sensing and near-space target detection technology, the radiometric calibration technology with high reliability and high accuracy, the on-orbit radiometric calibration device has become an essential orientation in quantitative remote sensing. The on-orbit radiometric caliWith the growing demand of quantitative remote sensing and near-space target detection technology, the radiometric calibration technology with high reliability and high accuracy, the on-orbit radiometric calibration device has become an essential orientation in quantitative remote sensing. The on-orbit radiometric calibration of an infrared remote sensing system includes non-uniformity correction(relative radiometric calibration) and absolute radiometric calibration. Absolute radiometric calibration is defined in terms of a sensor′s response on a physical, real-world scale, measured in internationally defined units. Based on the introduction of the basic calibration principles, the latest development in infrared on-orbit radiometric calibration devices was reviewed and the technical features of the radiometric calibration method was analyzed. Furthermore, our recent research progress was introduced based on internal calibration sources and combined with starring image in high dynamic range(HDR) relative radiometric calibration methods was introduced. The research promotes the development of infrared on-orbit radiometric calibration devices and technology..
Infrared and Laser Engineering
- Publication Date: Jan. 01, 1900
- Vol. 48, Issue 9, 904001 (2019)
Application research of sensor output digitization for compact near infrared IOT node
Wei Yang, Wang Xuquan, Wei Yongchang, Liu Xu, Huang Zhangcheng, Huang Songlei, and Fang Jiaxiong
The rise of the Internet of Things (IOT) spectral analysis technology has driven the development of near infrared spectroscopy sensors toward miniaturization, digitization and intelligence. A specific digitization research on InGaAs spectral sensor was reported to meet the digital and intelligent development of InGaAs The rise of the Internet of Things (IOT) spectral analysis technology has driven the development of near infrared spectroscopy sensors toward miniaturization, digitization and intelligence. A specific digitization research on InGaAs spectral sensor was reported to meet the digital and intelligent development of InGaAs focal plane Arrays (FPA). A new compact near infrared spectral node was developed integratedly with digital output spectral sensor circuit using self-developed analog to digital convertor (ADC) chip. The proposed node integrated 202 effective spectral channels with a wavelength range of 900 nm to 1 700 nm and a spectral resolution better than 16 nm. The wavelength accuracy and repeatability was less than 1 nm and 0.3 nm, respectively. The signal to noise ratio (SNR) of node system was about 500:1, and the frame scanning time was about 3 ms. The research results show that the compact IOT spectral node meets the practical application requirements of near infrared spectral analysis, and provides technical supports for the sensor on-chip digitization and IOT near infrared spectral analysis applications..
Infrared and Laser Engineering
- Publication Date: Jan. 01, 1900
- Vol. 48, Issue 9, 904002 (2019)
Modeling and evaluation of infrared seeker in high temperature window
Chai Guobei, Zhao Xiaoning, Liu Wei, Bao Wenzhuo, Xie Xiaoyang, and Li Qiang
The high temperature window of a hypersonic vehicle can have a severe impact on the imaging performance of the infrared seeker. In order to quantitatively analyze the high temperature window effect, the imaging and quantitative characterization model of the infrared seeker in high temperature window was established thrThe high temperature window of a hypersonic vehicle can have a severe impact on the imaging performance of the infrared seeker. In order to quantitatively analyze the high temperature window effect, the imaging and quantitative characterization model of the infrared seeker in high temperature window was established through the coupling of the signal response characteristics of the infrared seeker and the high temperature thermal radiation characteristics. The quantiative charateriation model was verified by high temperature window experiment of typical infrared seeker system. Based on the quantitative characterization model, combined with the ship radiation data obtained from the external field test, the imaging results of the infrared seeker under various temperature windows were calculated, and the imaging performance of the infrared seeker under the high-temperature window was evaluated. The analysis results indicate that when the window temperature exceeds 250 ℃, the naked eye can hardly distinguish the ship through the image; when the window temperature exceeds 300 ℃, the target resolution and tracking cannot be achieved by the seeker recognition algorithm..
Infrared and Laser Engineering
- Publication Date: Jan. 01, 1900
- Vol. 48, Issue 9, 904003 (2019)
Scheduling approach of mobile radar/infrared radiation control
Zhang Yunpu, Xu Gongguo, Shan Ganlin, and Duan Xiusheng
To reduce the radiation risk of mobile radar/infrared cooperative tracking, a scheduling approach of mobile radar/infrared radiation control was proposed. Firstly, a target tracking model was established based on the moving state of the platform and the target, and the tracking accuracy was predicted by using the cubatTo reduce the radiation risk of mobile radar/infrared cooperative tracking, a scheduling approach of mobile radar/infrared radiation control was proposed. Firstly, a target tracking model was established based on the moving state of the platform and the target, and the tracking accuracy was predicted by using the cubature Kalman filter. Secondly, the radar radiation model was established by introducing the radiation effect, and the prediction methods of the radar radiation status and the system radiation cost were given. Then, the objective function of non-myopic scheduling was constructed with tracking accuracy satisfying task requirements as constraints and non-myopic radiation cost minimization as optimization objectives. Finally, a decision tree search algorithm was designed to solve the problem of high computational complexity. The simulation results show that the proposed scheduling approach has better radiation control effect than the myopic scheduling approach. When the decision step is 3, the radiation cost decreases by 26.5%. Compared with the fixed position scheduling approach, the proposed approach can improve the tracking performance and reduce the radiation cost. When tracking low-speed targets, the tracking error and radiation cost are reduced by 29.9% and 30.5%, respectively..
Infrared and Laser Engineering
- Publication Date: Jan. 01, 1900
- Vol. 48, Issue 9, 904004 (2019)
Infrared imaging modeling and image simulation of limb background for space target detection
Yu Kun, Guo Biao, and Cong Mingyu
The limb infrared sounding is an effective means of detecting the space target with weak radiation. The infrared radiation characteristics of the limb background have an important influence on the target detection and tracking. The radiation statistical characteristics of the limb background were modeled by the measuriThe limb infrared sounding is an effective means of detecting the space target with weak radiation. The infrared radiation characteristics of the limb background have an important influence on the target detection and tracking. The radiation statistical characteristics of the limb background were modeled by the measuring images: the background radiance had different distribution patterns in the vertical and horizontal directions of the horizon projection in the image. The vertical distribution was related to the tangent height. The horizontal direction could be approximated as a normal distribution, and the coefficient of variation ranged from 0.01 to 0.05. Based on the modeling results, a fast simulation method of limb background infrared image was proposed. The experimental results show that the simulation image and the measuring image have high consistency, which verifies the effectiveness of the imaging model and simulation method. The time of the fast simulation method is 1/200 of the conventional pixel-by-pixel simulation method, which can meet the requirements of real-time simulation. The research results can be applied to the fields of infrared camera design and target detection algorithm testing..
Infrared and Laser Engineering
- Publication Date: Jan. 01, 1900
- Vol. 48, Issue 9, 904005 (2019)
Research on stray radiation of infrared detection optical system based on ray-tracing
Zhang Faqiang, Zhang Weiguang, and Wan Wenbo
Analysis and suppression of stray radiation are significant component to infrared detection optical system design. Stray radiation will add the noise of system, and reduce the system detection ability of system on target. The stray radiation sources of infrared detection system were analyzed in this paper, and the theoAnalysis and suppression of stray radiation are significant component to infrared detection optical system design. Stray radiation will add the noise of system, and reduce the system detection ability of system on target. The stray radiation sources of infrared detection system were analyzed in this paper, and the theory of stray radiation based on ray-tracing was introduced. Then, the thought of backward ray-tracing based on an infrared detection optical system was advanced. After the characteristics of key surfaces were analyzed, the absorbing membrane of mechanical surface was introduced to suppress the stray radiation. The analysis results meet the requirements of stray radiation suppression..
Infrared and Laser Engineering
- Publication Date: Jan. 01, 1900
- Vol. 48, Issue 9, 904006 (2019)
Study on distributed cooperative guidance law for infrared imaging guided missiles
Gao Ye, Zhou Jun, Guo Jianguo, and Ji Hua
Aiming at the problem of infrared guided imaging missiles cooperative attack, a novel collaborative detection oriented distributed cooperative guidance law considering the restrict of FOV, consensus of impact time and impact angle was proposed based on the network synchronization principle. Firstly, motion equations inAiming at the problem of infrared guided imaging missiles cooperative attack, a novel collaborative detection oriented distributed cooperative guidance law considering the restrict of FOV, consensus of impact time and impact angle was proposed based on the network synchronization principle. Firstly, motion equations including relative distance and FOV were established. With the help of coordinate transformation, the consensus problem of impact time and impact angle was converted into the consensus problem of relative distance and FOV. Secondly, the modified component of pure proportional guidance and tangential acceleration based on the distributed synchronization strategy were derived considering restrict of FOV. Finally, sufficient condition to achieve simultaneous attack was proposed, and the parameter design method was given. The proposed guidance law does not rely on the central node and adapts the non-constant velocity. Besides, it has the advantage of considering restrict of FOV and low communication cost. The proposed guidance law is suited for distributed cooperative guidance for infrared imaging guided missiles..
Infrared and Laser Engineering
- Publication Date: Jan. 01, 1900
- Vol. 48, Issue 9, 904007 (2019)
[in Chinese]
Suppressing self-focusing effect in high peak power Nd:YAG picosecond laser amplifier systems
Lv Siqi, Lu Shang, and Chen Meng
The output average power of all-solid-state picosecond amplifier suffered from self-focusing effect existed in the gain crystals. Through introducing the compensation element-gallium arsenide（GaAs）plate, the damage due to self-focusing effect has been avoided and the suppressing mechanism has been studied through theorThe output average power of all-solid-state picosecond amplifier suffered from self-focusing effect existed in the gain crystals. Through introducing the compensation element-gallium arsenide（GaAs）plate, the damage due to self-focusing effect has been avoided and the suppressing mechanism has been studied through theoretical analysis and experimental research for high peak power Nd:YAG crystal picosecond amplifier systems. The nonlinear refractive index coefficient of GaAs was obtained by calculation, and the relationship between the thickness of GaAs plate and the length of Nd:YAG rod under the optimal effect of suppressing self-focusing was given by numerical simulations. Under the condition that the center wavelength of the incident picosecond laser beam is 1 064 nm, the repetition frequency is 1 kHz, and the peak power density is about 12 GW/cm2, experiments on the effect of GaAs plates with different thicknesses(200 μm and 550 μm) to reduce the self-focusing damage in Nd:YAG rod have been completed. With optimization of thickness of the GaAs plate, the compensation method demonstrates high efficiency under high peak power picosecond pulses condition especially for Nd:YAG amplifier..
Infrared and Laser Engineering
- Publication Date: Jan. 01, 1900
- Vol. 48, Issue 9, 905001 (2019)
A magnitude modulation method of laser diode based on real-time power feedback
Xue Mengfan, Peng Dongliang, Rong Yingjiao, Shentu Han, Luo Ji′an, Chen Zhikun, and Liu Zhiwei
The conventional magnitude modulation method of laser diode(LD) has defects, such as unstable modulated magnitude and nonlinear distortion, therefore a new LD magnitude modulation method based on the real-time power feedback was proposed in this paper. Photodiode(PD) was employed to monitor the output power of LD. And The conventional magnitude modulation method of laser diode(LD) has defects, such as unstable modulated magnitude and nonlinear distortion, therefore a new LD magnitude modulation method based on the real-time power feedback was proposed in this paper. Photodiode(PD) was employed to monitor the output power of LD. And the operating current of LD was adjusted automatically according to the monitored output power of LD, by which the output power of LD varied with modulation signal. Finally, a prototype was built and tested. In the range of 20 ℃ to 40 ℃, The -3 dB bandwidth of prototype was up to 20 MHz， the stability of modulated magnitude was less than 4% and maximum nonlinear error was only 0.1%. The results show that the stability of LD output power is improved; the nonlinear distortion of modulated wave is also reduced, with linear working range of semiconductor lasers expanded..
Infrared and Laser Engineering
- Publication Date: Jan. 01, 1900
- Vol. 48, Issue 9, 905002 (2019)
Transmission method of analog signal in excimer laser system
Pan Ning, Liang Xu, Lin Ying, Pan Bingbing, and Fang Xiaodong
Several analog signal transmission system under harsh electromagnetic interference environment was introduced, and a method of transmission was designed. Firstly, the analog signal was converted into a frequency signal through the detector and sent through the fiber transmitter. Secondly, the fiber signal was received Several analog signal transmission system under harsh electromagnetic interference environment was introduced, and a method of transmission was designed. Firstly, the analog signal was converted into a frequency signal through the detector and sent through the fiber transmitter. Secondly, the fiber signal was received and the frequency of the optical signal was measured within the configurable regularized time and then the analog signal was calculated instead of using the traditional method which converted analog signal to digital signal after frequency-to-voltage conversion. This system not only got the reduced total conversion time and improved response speed, but also can obtain different precision according to system requirements by adjusting converting time. Tested on a 248 nm KrF excimer laser, the system realized high-precision online monitoring of the slow-changing working gas pressure signal compared with traditional method, and then it also measured the fast-responsed energy signal of pulse laser up to 90 Hz well. By calculating the Pearson coefficient, the acquired value of the scheme tends to be consistent with the original signal to meet the application requirements..
Infrared and Laser Engineering
- Publication Date: Jan. 01, 1900
- Vol. 48, Issue 9, 905003 (2019)
Design of current drive and alternating current temperature control system for high-precision laser
Miao Cunxiao, Xing Guozhu, Liu Jianfeng, Wan Shuang′ai, Yang Jing, and Yan Xiaoqiang
As an important part of the atomic magnetometer, the semiconductor laser′s wavelength and power are mainly determined by current and temperature. However, the traditional DC temperature control system would cause magnetic field interference to the atomic magnetometer. Aiming at high-precision current control, temperatuAs an important part of the atomic magnetometer, the semiconductor laser′s wavelength and power are mainly determined by current and temperature. However, the traditional DC temperature control system would cause magnetic field interference to the atomic magnetometer. Aiming at high-precision current control, temperature control and magnetic field interference, a laser constant current source driving system and Alternating Current(AC) temperature control system were developed. Firstly, a high-precision laser constant current source driving system based on power amplifier was designed. Secondly, the AC temperature modulation demodulation detection and AC heating drive system were designed. Finally, the STM32 controller, high-precision AD acquisition and DA output combined with temperature fuzzy adaptive PID control algorithm were used for high-precision temperature control. The experimental results show that the temperature control accuracy is ±0.005 ℃ at 42 ℃, and the current stability is ±0.5 μA at 32 mA, which lays a foundation for laser optical power and wavelength stability..
Infrared and Laser Engineering
- Publication Date: Jan. 01, 1900
- Vol. 48, Issue 9, 905004 (2019)
Influence of thermal transfer on temperature drift compensation in nonplanar four-frequency differential laser gyros
Zhao Hongchang, and Wang Zhiguo
In order to reduce the temperature sensitivity of the zero drift in four-frequency differential laser gyro (FFDLG), the mathematical compensation model and the thermal design of the installation structure were studied. The relationship between zero drift and temperature of the FFDLG was studied by high and low temperatIn order to reduce the temperature sensitivity of the zero drift in four-frequency differential laser gyro (FFDLG), the mathematical compensation model and the thermal design of the installation structure were studied. The relationship between zero drift and temperature of the FFDLG was studied by high and low temperature tests. In the first test, the FFDLG was fixed in the shielding box by an ordinary copper support. Due to the asymmetry of the temperature changes in the two discharge branches, the temperature change rate was a significant term of the mathematical compensation model. In the second test, a special copper support was designed to make the temperature in the two discharge branches change symmetrically, so the importance of temperature change rate in the mathematical compensation model was greatly reduced. After the support was improved, the root mean square (RMS) of residual bias after compensation decreased from 0.018 Hz to 0.01 Hz. Even if only a polynomial of temperature was used in the compensation model, an RMS of residual bias of 0.012 Hz could be achieved. The results show that: when designing FFDLG system, the thermal design of the installation structure can improve the compensation effect of the mathematical model. Temperature compensation is an effective method to improve the accuracy of the FFDLG. An FFDLG with an RMS of residual bias of 0.013 (°)/h in the range of -40-60 °C was obtained after improvement in the installation structure and temperature compensation..
Infrared and Laser Engineering
- Publication Date: Jan. 01, 1900
- Vol. 48, Issue 9, 905005 (2019)
Application of Lyot birefringent filters in DF chemical laser
Yang Zhen, Ren Xiaoming, Zhao Haitao, Liu Xiankui, Wang Jie, and Guo Jianzeng
Considering the effect of modulation depth, tuning rate, free spectral range, walk-off angle, a type of birefringent filters (BRFs) was designed, which consisted of the same three sapphire crystals plates. The birefringent filters′ thickness was 9 mm. They were placed parallelly with the same axis. In order to reduce tConsidering the effect of modulation depth, tuning rate, free spectral range, walk-off angle, a type of birefringent filters (BRFs) was designed, which consisted of the same three sapphire crystals plates. The birefringent filters′ thickness was 9 mm. They were placed parallelly with the same axis. In order to reduce the reflection loss of the surface, light incidented through BRFs at Brewster′s angle. According to design the tilt angle between optic axis to the surface of the plate which was 63°, tuning was accomplished by rotating the plates as a whole about an axis perpendicular to the surface; finally the spectrum from 3.6 to 4.3 μm can be output. Considering the mismachining tolerance of BRFs and the deviation of incident angle adjustment, the calculation was accomplished from different tilt angle and incident angle respectively, the output wavelength correction can be realized by rotating the plates. BRFs are low-cost and easy to use. Besides, they have a good function of tuning and selecting the different frequency. It′s useful to study the characters of DF chemical lasers′ spectrum..
Infrared and Laser Engineering
- Publication Date: Jan. 01, 1900
- Vol. 48, Issue 9, 905006 (2019)
[in Chinese]
Effects of synthetic scene sampling-rate and scanning direction on subpixel line target simulations
Li Yulun, Yang Zhen, Ma Xiaoshan, and Li Haitao
The influence of ground scene sampling-rate and sensor scanning direction has been examined to accurately simulate the sub-pixel line target in synthetic spectral imagery. Both theoretical analysis and simulation experiments were proposed. The geometric relation between the pixels of the satellite detector and the grouThe influence of ground scene sampling-rate and sensor scanning direction has been examined to accurately simulate the sub-pixel line target in synthetic spectral imagery. Both theoretical analysis and simulation experiments were proposed. The geometric relation between the pixels of the satellite detector and the ground scene was inferred. Hough line transform was adopted to describe the radiometric property and spatial distributions of the simulated line target. Results were analyzed with the DataFrame. It is concluded that the aliasing error increases notably with the angle between the scanning direction and line varying in the range near 0°, 90°. The line becomes less significant and fake lines appear. The similar phenomenon exists in the angle range near 45°. However, the aliasing effect is relatively mild, thus providing robustness to the simulation. To a certain extent, sampling with a more intensive rate improves the line′s significance, but cannot eliminate the blur-introduced errors of spatial location. These results can be used to evaluate the simulation fidelity, and design appropriate models..
Infrared and Laser Engineering
- Publication Date: Jan. 01, 1900
- Vol. 48, Issue 9, 926001 (2019)
Correction method of image distortion of fisheye lens
Lu Lijun, Liu Meng, and Shi Ye
A new method to correct the image distortion of a fisheye lens was presented. The relationship of radial position of the chief ray at a projection plane and image plane was obtained by tracing the chief ray through the optical system, then a Fourier series was applied to fit the relation curve. Finding the inverse funcA new method to correct the image distortion of a fisheye lens was presented. The relationship of radial position of the chief ray at a projection plane and image plane was obtained by tracing the chief ray through the optical system, then a Fourier series was applied to fit the relation curve. Finding the inverse function of the expression of the series, the image without distortion can be obtained in terms of the resultant distorted image. Correction of image distortion of two fisheye lenses was simulated numerically with the method, experiments of distortion correction of two pictures taken with one of fisheye lenses, Nikon 16 mm/F2.8 lenses, were performed. The results show that residual radial height error of the restored image to the object is quite small(less than 0.25%) when the projection plane coincides with the object plane. The experiments also demonstrate that the method is feasible..
Infrared and Laser Engineering
- Publication Date: Jan. 01, 1900
- Vol. 48, Issue 9, 926002 (2019)
Distortion rectification of linear imaging for space unstability targets
Sun Riming, Li Jiangdao, Lin Tingting, Li Ronghua, and Ji Lin
The un-cooperation and motion uncertainty of space unstablility targets make it difficult to obtain directly their real 3D shapes using the linear measurement. The distoration rectification method of linear imaging for space unstablility targets was presented through the temporal and spatial relations of the same corneThe un-cooperation and motion uncertainty of space unstablility targets make it difficult to obtain directly their real 3D shapes using the linear measurement. The distoration rectification method of linear imaging for space unstablility targets was presented through the temporal and spatial relations of the same corner point on the continuous linear array images. Firstly, a general linear imaging model of space unstability targets was set up based on the imaging mechanism of the linear imaging radar and motion law of space unstability targets. Then, the motion parameters of spin and nutation of space unstability targets was obtained by use of the progressive estimation mechanism according to the local similarity and global continuity of motion. Finally, the distorted linear array image column was rectified by column and then the real 3D shape of space targets was obtained according to these motion parameters based on the above linear imaging model. Experimental results illustrate the effectiveness of the proposed method for different kinds of motion states under the uncooperative and single-load condition and the conditional stability of our proposed method about the selection of frame numbers, which ensures that the spin axes would resolve around the nutation axis turning one circle. It provides guidance and reference for the applications of our method on the other linear measurement need..
Infrared and Laser Engineering
- Publication Date: Jan. 01, 1900
- Vol. 48, Issue 9, 926003 (2019)
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