Contents
2018
Volume: 38 Issue 1
49 Article(s)
Export citation format
[in Chinese]
Underwater Image Restoration Based on Background Light Estimation and Dark Channel Prior
Xie Haoling, Peng Guohua, Wang Fan, and Yang Cheng
A new underwater image restoration method under natural light is proposed according to the ocean optics definition of background light. Optical parameters of water (attenuation coefficient and dissipation coefficient) used to calculate the background light are estimated based on reasonable hypothesis and deduction of oA new underwater image restoration method under natural light is proposed according to the ocean optics definition of background light. Optical parameters of water (attenuation coefficient and dissipation coefficient) used to calculate the background light are estimated based on reasonable hypothesis and deduction of optical theory formula. The relationship between scattering coefficient and wavelength is used to calculate the values of transmission functions of three channels (red, green and blue), and guided filtering is used to refine the transmission image. Finally, the underwater image is reconstructed with an inverse solving imaging model. Experimental results show that the proposed algorithm has some advantages in restoring the original color of the scene and removing the backscattering..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 1, 101002 (2018)
Atmospheric Optics and Oceanic Optics
Echoing Characteristics of Coherent Lidar in Different Aerosol Environments
Xiao Dong, Yihua Hu, Shilong Xu, and Hao Liu
Based on Mie scattering theory, the main process of semi-analytic Monte Carlo simulation is illustrated to research the backscattering properties of aerosol particles to linearly polarized laser in horizontal direction. Four typical environments, five typical aerosol components and three humidity conditions are chosen Based on Mie scattering theory, the main process of semi-analytic Monte Carlo simulation is illustrated to research the backscattering properties of aerosol particles to linearly polarized laser in horizontal direction. Four typical environments, five typical aerosol components and three humidity conditions are chosen from optical property libraries of aerosols and clouds. The depolarization ratio, polarization ratio and returned photon number are calculated at 1.5 μm and 2.0 μm, respectively. The variation laws of polarization properties of backscattered laser are acquired with changing of particle sizes of different kinds of aerosol components. Besides, the echoing characteristics of backscattered laser are obtained in four typical aerosol environments. At last, the laser power ratio needed in different environments to achieve the same detection performance is analyzed, which is of reference value to the design and analysis of the coherent lidar systems for the long range and high accuracy observation..
Acta Optica Sinica
- Publication Date: Mar. 28, 2018
- Vol. 38, Issue 1, 0101001 (2018)
Channel Compensation Based on Pulse Laser Propagating in Atmosphere
Haifeng Yao, Xiaolong Ni, Chunyi Chen, Shoufeng Tong, Huilin Jiang, and Zhi Liu
In order to investigate the propagation characteristics of rectangular pulse laser in atmosphere,a mathematical model of pulse signal propagation in atmosphere is established and a compensation algorithm for channel is proposed. A propagation experiment of 100 MHz rectangular pulse is carried out between two buildings In order to investigate the propagation characteristics of rectangular pulse laser in atmosphere,a mathematical model of pulse signal propagation in atmosphere is established and a compensation algorithm for channel is proposed. A propagation experiment of 100 MHz rectangular pulse is carried out between two buildings with a distance of 6.2 km, and the compensation algorithm for channel is verified by FPGA compliling software. The experimental results indicate that the pulse signal is distorted after passing through the atmospheric channel. The performance of atmospheric channel can be considered as a low-pass system in the frequency domain and signals with high frequency larger than 430 MHz are suppressed. With the channel compensation algorithm, the distortion of rectangular optical pulse is suppressed effectively, the system bandwidth is improved, and the signal noise ratio is increased by 5 times. The bit error rate decreases to about 10 -6 when the optical signal noise ratio is 10 dB..
Acta Optica Sinica
- Publication Date: Apr. 11, 2018
- Vol. 38, Issue 1, 0101003 (2018)
Diffraction and Gratings
A Rapid Simulation Method for Diffraction Spectra of EUV Lithography Mask Based on Improved Structural Decomposition
Zhang Heng, Li Sikun, and Wang Xiangzhao
Fast and accurate diffraction simulation for extreme-ultraviolet lithography mask with complex patterns is achieved via combination of the expanded absorber model and optimized multilayer film model. The modified thin-mask absorber model is expanded to enable simulation of absorber shifting. Equivalent-layer model and Fast and accurate diffraction simulation for extreme-ultraviolet lithography mask with complex patterns is achieved via combination of the expanded absorber model and optimized multilayer film model. The modified thin-mask absorber model is expanded to enable simulation of absorber shifting. Equivalent-layer model and single-surface approximation model are adapted for defective and defect-free multilayer film simulation respectively. For incident angle larger than 10°, the simulation accuracy of the defective multilayer film is improved when the ideal reflection of single surface is modified with the equivalent-layer model. Simulation speed is enhanced by concurrent computing tensor product and vectorization concurrency. For defect-free mask with different simulation parameters, the modified method achieves better simulation accuracy and speed (critical dimension errors within 0.4 nm compared with the rigorous method) than the domain decomposition method. For defective mask, the critical dimension change versus absorber shifting is accurately simulated by the modified method, and the simulation errors are within 0.6 nm (compared with rigorous method) for a mask of 240 nm pitch while the modified method is 150 times faster than the rigorous method..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 1, 105001 (2018)
Multilayer Waveguide Bragg Grating Based on Hybrid Surface Plasmon Polaritons
Quan Wang, Jing Xiao, Qiqin Wei, and Ping Liu
According to the excitation mechanism of hybrid surface plasmon polaritons and the waveguide structure of traditional hybrid surface plasmon polaritons, a multilayer waveguide Bragg grating is proposed. Two low refractive index materials, SiO2 and NaF, are used as the core layer in the structure. At the communication wAccording to the excitation mechanism of hybrid surface plasmon polaritons and the waveguide structure of traditional hybrid surface plasmon polaritons, a multilayer waveguide Bragg grating is proposed. Two low refractive index materials, SiO2 and NaF, are used as the core layer in the structure. At the communication wavelength of 1550 nm, the structure of the grating is studied and optimized for the transmission distance and the mode field limitation ability of the light wave. And the relationship between the grating period number and the reflectivity of light wave is further analyzed. Simulation results show that the transmission distance and the effective mode field area of the Bragg grating are 178.12 μm and 0.203 μm 2, respectively. The structure not only reduces the loss due to the light field limitation at the metal surface, but also reflects relatively strong mode field limitation. The reflectance can reach 71.9% when the grating period number is 60, and the structure has a good filtering characteristic..
Acta Optica Sinica
- Publication Date: Mar. 29, 2018
- Vol. 38, Issue 1, 0105002 (2018)
Design and Fabrication of Bionic Broadband Antireflective Microstructure on Zinc Selenide
Liang Fei, Yun Cui, Dongyun Wan, Peng Chen, and Jiao Xu
The optical properties of parabolic cone array microstructure of zinc selenide are researched by finite-difference time-domain method. The effects of microstructure parameters, such as period, height, filling factor, and profile shape on the reflectivity are discussed. Structural parameters corresponding to good antireThe optical properties of parabolic cone array microstructure of zinc selenide are researched by finite-difference time-domain method. The effects of microstructure parameters, such as period, height, filling factor, and profile shape on the reflectivity are discussed. Structural parameters corresponding to good antireflection effect are obtained. The parabolic cone period microstructure is prepared by twice interference lithography and reactive ion etching technology according to the simulated results. The surface morphology is analyzed by field emission scanning electron microscopy, and the transmittances of the zinc selenide with double-sides polished and single-side microstructures are respectively measured with the utilization of the Fourier transform infrared spectrometer. The measured results illustrate that the average transmittance of samples with single-sided microstructure is 10% higher than that of double-sided polished zinc selenide at 2-5 μm wavelengths, and the transmittance reaches a maximum value of 82% at 2.3 μm..
Acta Optica Sinica
- Publication Date: Mar. 29, 2018
- Vol. 38, Issue 1, 0105004 (2018)
Fiber Optics and Optical Communications
Frame Synchronization Compensation Algorithm for Visible Light Implicit Imaging Communication
Li Mingchao, Hu Yunpeng, Yao Xiangwen, Tang Yanqun, and Shen Zhixiang
To solve the unsynchronized problem between the transmitter end and the receiver end in visible light implicit imaging communication, we analyze the characteristics of display camera link, and summarize the unsynchronized problems as frame loss and frame fusion. Aiming at the frame loss and frame fusion, we establish aTo solve the unsynchronized problem between the transmitter end and the receiver end in visible light implicit imaging communication, we analyze the characteristics of display camera link, and summarize the unsynchronized problems as frame loss and frame fusion. Aiming at the frame loss and frame fusion, we establish a reasonable mathematical model for received frames. Based on the model, a frame loss detecting algorithm is proposed by analysis of spatial mean characteristics of difference frame absolute values, and a frame fusion fuzzy region detecting algorithm is proposed by utilization of row mean characteristics of difference frame absolute values and row variance characteristics of difference frames. The simulation and experimental results show that the proposed frame synchronization compensation algorithms can solve the frame loss and frame fusion effectively, achieve good frame synchronization effect, improve system bit error rate performance, and complete reliable transmission of implicit information..
Acta Optica Sinica
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 1, 106002 (2018)
Carrier Recovery Technology of Optical Phase Locked Loop in Coherent Laser Communication System
Yang Liu, Shoufeng Tong, Shuai Chang, Yansong Song, Yan Dong, Yi Dong, and Zhe An
By modeling and analyzing on the carrier recovery based on COSTAS optical phase locked loop, we obtain the closed-loop transfer function, error function and carrier signal that to be recovered of the system. Then we design composite control to realize the fast and small range tracking by using the acousto optic frequenBy modeling and analyzing on the carrier recovery based on COSTAS optical phase locked loop, we obtain the closed-loop transfer function, error function and carrier signal that to be recovered of the system. Then we design composite control to realize the fast and small range tracking by using the acousto optic frequency shifter in the inner ring, and quickly pull into capture tape by control laser in the outer ring. In order to get the good carrier recovery and signal demodulation, we design the phase detection module based on exclusive-OR gate (XOR) to analyze the phase detector. The phase detection ranges from -42 ° to +42 °, and phase detector gain achieves 14.4 mV/(°) when the loop bandwidth is 1.5 MHz. The experimental results show and that the carrier recovery and signal demodulation is good when the code rate is 5 Gb/s, and the error rate is 1.55×10
-8 when the signal power reaches -40.4 dBm. With the rate increasing or decreasing, the system performance decreases, but the system can recover the carrier signal and demodulate the data. This system can provide references for homodyne coherent communication laboratory verification.
.
Acta Optica Sinica
- Publication Date: Mar. 27, 2018
- Vol. 38, Issue 1, 0106001 (2018)
Cascade Scheme Based on Multiple-Input Multiple-Output in Spatial Optical Communication
Yang Cao, Xun Zhang, Xiaofeng Peng, and Fatao Ren
Aiming at the problem of error diffusion in multiple-input multiple-output free-space optical (MIMO-FSO) communication system, we propose a cascaded code(LT-PC) scheme of the Luby transform (LT) code and the parity check (PC) code. The LT-PC scheme can locate and delete wrong packets by adding a checker based on LT codAim
ing at the problem of error diffusion in multiple-input multiple-output free-space optical (MIMO-FSO) communication system, we propose a cascaded code(LT-PC) scheme of the Luby transform (LT) code and the parity check (PC) code. The LT-PC scheme can locate and delete wrong packets by adding a checker based on LT code. The performance of the LT code is compared with that of the LT-PC code. The LT-PC code is verified by the simulation under the systems with different number of MIMO groups and communication distances. Different atmospheric turbulence intensity channels are also simulated. The results show that the LT-PC code can improve the success rate of decoding when the decoding overhead is less than 0.5. In the same turbulence environment, the system with antenna number of 3×3 has about 3 dB coding gain compared with the system with antenna number of 2×2. After using the LT-PC code, the improving range of the coding gain is 0.5 dB~2 dB when the bit error rate is about 10 -5. In the strong turbulence environment, the LT-PC code still has certain advantages over the LT code with the increase of the communication distance when the numbers of antennas are the same.
.Acta Optica Sinica
- Publication Date: Mar. 28, 2018
- Vol. 38, Issue 1, 0106003 (2018)
A Joint Frequency Offset and Phase Estimation Scheme Based on Cascaded EKF and LKF
Bingjie Hou, Yanfu Yang, Qian Xiang, Qun Zhang, and Yong Yao
A co-processing scheme of frequency offset and phase noise based on cascade extended Kalman filter (EKF) and block-processed linear Kalman filter (LKF) is proposed. The EKF is responsible for preliminary estimation of frequency offset. The LKF is responsible for tracking frequency offset and phase noise accurately. RelA co-processing scheme of frequency offset and phase noise based on cascade extended Kalman filter (EKF) and block-processed linear Kalman filter (LKF) is proposed. The EKF is responsible for preliminary estimation of frequency offset. The LKF is responsible for tracking frequency offset and phase noise accurately. Relationship between the optimal block length and the tuning parameter Q, linewidth tolerance, frequency offset estimation range and frequency offset tracking speed of algorithm are discussed and analyzed in detail. The results show that the scheme has fast convergence performance, and can achieve high estimation accuracy of frequency offset and phase estimation. Moreover, the frequency offset drift can reach 320 MHz/μs. Compared with traditional blind phase search method, the scheme has high frequency offset tolerance and low implementation complexity. Finally, the carrier recovery performance for quadrature phase shift keying (QPSK) optical communication system is experimentally studied, and the carrier frequency offset estimation performance under different optical signal-to-noise ratios and block data lengths is given..
Acta Optica Sinica
- Publication Date: Mar. 29, 2018
- Vol. 38, Issue 1, 0106004 (2018)
Fast Polarization Feedback Algorithm for Quantum Key Distribution with Aerial Fiber for Power Grid
Pengyi Tang, Guochun Li, Song Gao, Gang Yu, Yunqi Dai, Yao Xiang, Dongdong Li, Yinghua Zhang, Bing Wu, Ziyan Zhao, Dequan Gao, Jianhong Liu, and Jian Wang
Photon polarization state in aerial fiber for power grid is susceptible to the rapid external random disturbances, which leads to low coding rate of polarization-coded quantum key distribution (QKD) system or even zero coding rate. To counter the rapid change of polarization state in the link, we design polarization fePhoton polarization state in aerial fiber for power grid is susceptible to the rapid external random disturbances, which leads to low coding rate of polarization-coded quantum key distribution (QKD) system or even zero coding rate. To counter the rapid change of polarization state in the link, we design polarization feedback system (FPF), and describe the working principle of the system. The key polarization feedback algorithms in the system are studied, including the selection of evaluation function and search algorithm of polarization convergence, the selection of monitoring conditions of polarization feedback cycle and coding cycle, and the adaptive selection of monitoring threshold. The whole system is measured on actual aerial fibers. The test results show that the system and algorithm can solve the problem of QKD code in intermediate-distance installed aerial fiber..
Acta Optica Sinica
- Publication Date: Apr. 11, 2018
- Vol. 38, Issue 1, 0106005 (2018)
Temperature Dependence of Transverse Magnetic Error in a Polarization Maintaining Fiber Optic Gyroscope
Xuyou Li, Pan Liu, Xingxing Guang, Yanda Guo, Qingwen Meng, and Guangchun Li
An investigation of the temperature dependence of transverse magnetic error in the polarization maintaining fiber optic gyroscope (PM-FOG) with non-skeleton coil is presented. It is found that the transverse magnetic error changes with the temperature, which can result from the temperature dependence of linear birefrinAn investigation of the temperature dependence of transverse magnetic error in the polarization maintaining fiber optic gyroscope (PM-FOG) with non-skeleton coil is presented. It is found that the transverse magnetic error changes with the temperature, which can result from the temperature dependence of linear birefringence and Verdet constant of polarization maintaining fiber (PMF). Based on Jones matrix method, the relationship between the transverse magnetic error and temperature in PM-FOG is deduced, and the experimental verification is carried out. The experimental results show that for the non-skeleton coil with length of 1 km, radius of 6 cm, linear birefringence of 2027 rad·m
-1, and maximum twist rate of 0.382 rad·m
-1, the transverse magnetic error changes from 26.51 (°)·h
-1 to 30.43 (°)·h
-1, under 1 mT transverse magnetic field and the temperature range of -40 ℃ to 60 ℃.
.
Acta Optica Sinica
- Publication Date: Mar. 29, 2018
- Vol. 38, Issue 1, 0106006 (2018)
Fourier Optics and Signal Processing
Folding Reflective 2f System Optical Correlator
Tuo Yang, Ping Xu, Liang Zhou, Jun Yu, Xiongchao Li, and Haixuan Huang
In order to further reduce the volume of optical correlator, an optical correlator for folding reflective 2f system is designed. The optical path adopts folding reflective structure. Digital micro lens replaces physical lens in the traditional correlator to reduce the volume of the structure and improve the system inteIn order to further reduce the volume of optical correlator, an optical correlator for folding reflective 2f system is designed. The optical path adopts folding reflective structure. Digital micro lens replaces physical lens in the traditional correlator to reduce the volume of the structure and improve the system integration. The structural design conditions and structural parameters of the folding reflective 2f correlator are given theoretically based on equivalent optical path method. The optimal trade-off share duplexed filter (SDF) is designed for the correlator, and the simulation analysis is performed by a self-compiled program. Simulation results indicate that the correlator still has good distortion invariant recognition performance when the target is subject to scaling and rotation distortion..
Acta Optica Sinica
- Publication Date: Mar. 29, 2018
- Vol. 38, Issue 1, 0107001 (2018)
Imaging Systems
Optical Coherence Tomography Based on Dynamic Speckle
Junbo Chen, Yaguang Zeng, Zhiling Yuan, and Zhilie Tang
Processing method of laser speckle imaging is introduced into optical coherence tomography (OCT). Spectra varying with time are acquired at the same position. The spectra at each moment are transformed into OCT structure by the Fourier transform along the direction of wave vector. The OCT structure information at the sProcessing method of laser speckle imaging is introduced into optical coherence tomography (OCT). Spectra varying with time are acquired at the same position. The spectra at each moment are transformed into OCT structure by the Fourier transform along the direction of wave vector. The OCT structure information at the same position and different moments is solved, and is then computed along the dimension of time by the Fourier transform to obtain the frequency spectrum of speckle. Imaging parameter is defined as the ratio of dynamic speckle to static counterpart in the frequency spectrum. The phantom experiment demonstrates feasibility of the method. The method is also applied to extracting blood vessel of a mouse ear, and the three-dimensional vascular structure is obtained..
Acta Optica Sinica
- Publication Date: Mar. 28, 2018
- Vol. 38, Issue 1, 0111001 (2018)
Field Calibration of Multiband High Resolution Imaging System with New Vacuum Solar Telescope
Rui Wang, Zhi Xu, Yuchao Chen, Zhenyu Jin, Yongyuan Xiang, Yu Fu, and Kaifan Ji
To achieve the filed matching of multiband images obtained by new vacuum solar telescope (NVST) with a high accuracy of 0.1″, a method called pinhole aperture filed calibration is proposed and applied to the experimental analysis about the photosphere [TiO(705.8 nm)] channel and chromosphere [Hα(656.28 nm)] channel of To achieve the filed matching of multiband images obtained by new vacuum solar telescope (NVST) with a high accuracy of 0.1″, a method called pinhole aperture filed calibration is proposed and applied to the experimental analysis about the photosphere [TiO(705.8 nm)] channel and chromosphere [Hα(656.28 nm)] channel of NVST. A pinhole-array aperture (11×11 pinholes) is used to the calibration of the rotation, scaling and translation relationships between the fields of the two channels. As a result, the high accuracy field matching of two-field solar images with the accuracy reaching up to 0.031″ is accomplished by affine transformation. It is also found that the matching residual is not uniform in the entire field (about 2') and the maximum residual is about 0.076″ at the edge of the filed. The values of the calibration parameters are changing with the variation of optical platform position, and the matching difference of filed is 0.05″, which is within the precision of the resolution requirement. The estimated accuracy is also supported by the analysis of measured data from TiO channel and Hα channel..
Acta Optica Sinica
- Publication Date: Mar. 29, 2018
- Vol. 38, Issue 1, 0111002 (2018)
Improved Stochastic CT Reconstruction Based on Particle Swarm Optimization for Limited-Angle Sparse Projection Data
Hongxia Gao, Lan Luo, Yinghao Luo, Zhanhong Chen, and Ge Ma
Because of the sampling scope and quantity limitation in the computed tomography (CT), the completeness of sparse projection data is very low, which leads to a huge search space for the reconstruction algorithm. The iterative algorithm based on convex optimization can not converge to the global minima in finite time duBecause of the sampling scope and quantity limitation in the computed tomography (CT), the completeness of sparse projection data is very low, which leads to a huge search space for the reconstruction algorithm. The iterative algorithm based on convex optimization can not converge to the global minima in finite time due to the fixed search path. Particle swarm optimization has global search capability, but costs tremendous computation and memory. To improve the quality of reconstruction from incomplete projection data, a new stochastic sparse reconstruction algorithm based on particle swarm optimization is proposed. Firstly, the initial solutions with diversity are generated by the stochastic strategy to ensure the search capability. Secondly, the proposed algorithm stochastically chooses either gradient descent direction or random direction based on the local best known solution and the global best known solution in the iteration, to ensure the efficiency of this algorithm and the diversity of search directions. Finally, to avoid trapping in local optimum, the random initial populations are generated based on the fitness evaluation, which represents the current situation. The contrast reconstruction experiments are conducted on both noise-free and noisy limited-angle sparse projection data. The experimental results demonstrate that the proposed algorithm is efficient and evidently superior in reconstruction quality and robustness compared to common iterative algorithms based on convex optimization or particle swarm optimization..
Acta Optica Sinica
- Publication Date: Apr. 11, 2018
- Vol. 38, Issue 1, 0111003 (2018)
Dual-Wavelength Image-Plane Digital Holographic Microscopy Based on Bi-Color LED Chips
Lijun Deng, Xingyan Huang, Lüming Zeng, Zhen Huang, and Guodong Liu
Dual-wavelength image-plane digital holographic microscopy based on bi-color LED chips is proposed. Firstly, a red LED chip with central wavelength of 670 nm and a green LED chip with central wavelength of 521 nm are packaged as a hemispherical LED chip. Composite holograms at different wavelengths and phase shift are Dual-wavelength image-plane digital holographic microscopy based on bi-color LED chips is proposed. Firstly, a red LED chip with central wavelength of 670 nm and a green LED chip with central wavelength of 521 nm are packaged as a hemispherical LED chip. Composite holograms at different wavelengths and phase shift are recorded with a color CCD camera. The phase distribution and surface profile of the sample are reconstructed based on the color separation technology, phase shifting technology and dual-wavelength phase extracting technology. The feasibility of the proposed method is demonstrated by the experimental results..
Acta Optica Sinica
- Publication Date: Mar. 29, 2018
- Vol. 38, Issue 1, 0111004 (2018)
Valid Aircraft Detection System for Remote Sensing Images Based on Cognitive Models
Yuqingyang Hou, Jicheng Quan, and Yongming Wei
In view of the problems in the traditional aircraft detection algorithms and the existing machine learning detection algorithms, one concept of valid aircraft detection is proposed for remote sensing images. With the full convolution detection and segmentation network based on the deep learning in the cognitive model, In view of the problems in the traditional aircraft detection algorithms and the existing machine learning detection algorithms, one concept of valid aircraft detection is proposed for remote sensing images. With the full convolution detection and segmentation network based on the deep learning in the cognitive model, one valid aircraft detection system is designed and simulated. A cognitive model for detection is constructed, and the function of each module is designed. The experimental results certify the effectiveness of this system, and this system provides a new thinking way and method for the development of intelligent detection of multiple objectives..
Acta Optica Sinica
- Publication Date: Mar. 29, 2018
- Vol. 38, Issue 1, 0111005 (2018)
Instrumentation, Measurement and Metrology
Extraction of Structure Line Segments from Point Clouds Using Voxel-Based Region Growing
Minglei Li, Wenpeng Zong, Guangyun Li, and Li Wang
Aiming at the problems remaining in existing extraction method of structure line segment such as low efficiency and reliability, an efficient extraction method for structure line segments from point clouds through voxel-based region growing is proposed. Firstly, point cloud is voxelized and segmented, and the distributAim
ing at the problems remaining in existing extraction method of structure line segment such as low efficiency and reliability, an efficient extraction method for structure line segments from point clouds through voxel-based region growing is proposed. Firstly, point cloud is voxelized and segmented, and the distributing regions of structure line segments are recognized through voxel-based nearest neighbors searching. Then, the distributing regions of structure line segments are segmented through voxel-based region growing. Finally, corresponding line segments are extracted and optimized in these segmented regions according to the equations of their supporting planes, and the accuracy of the results are assessed. The test experiments are performed, and the feasibility, accuracy and efficiency of the proposed method are verified by obtaining the processing and comparison results of adopted point clouds. The experimental results indicate that the efficiency is increased more than 10 times and the accuracy is improved about 0.25 times, which verifies that the proposed method has high accuracy and efficiency as well as the ability of achieving relatively more ideal results.
.Acta Optica Sinica
- Publication Date: Mar. 29, 2018
- Vol. 38, Issue 1, 0112001 (2018)
Measurement of Liquid Diffusion Coefficient Based on Double Liquid-Core Cylindrical Lens: Equivalent Observation Altitude Measurement Method
Yan Xia, Weidong Meng, Yan Chen, Fangxi Song, and Xiaoyun Pu
A method to measure liquid diffusion coefficients based on double liquid-core cylindrical lens (DLCL): equivalent observation altitude measurement method is introduced. The front liquid core of DLCL is used as both diffusive pool and main imaging element, and the rear liquid core is used as aplanatic auxiliary element.A method to measure liquid diffusion coefficients based on double liquid-core cylindrical lens (DLCL): equivalent observation altitude measurement method is introduced. The front liquid core of DLCL is used as both diffusive pool and main imaging element, and the rear liquid core is used as aplanatic auxiliary element. A fixed altitude of DLCL is selected as observation position. Based on the Fick’s second law, the liquid diffusion coefficient is calculated according to the relationship between the diffusion image width and time. The diffusion coefficient of 0.33 mol/L KCl aqueous solution is D=1.8530×10
-5 cm
2/s, which is measured at the room temperature (25 ℃) and by equivalent observation altitude measurement method. The relative error between the measured results and the literature values is 0.65%. The proposed method makes use of the advantage of DLCL that can reduce the spherical aberration in certain range of refractive index, which makes the liquid diffusion coefficients have the characteristics of high accuracy (relative error is less than 1%), high speed (measurement time is about 60 min), and the visualization of diffusion process.
.
Acta Optica Sinica
- Publication Date: Apr. 05, 2018
- Vol. 38, Issue 1, 0112002 (2018)
Shape Measurement Based on Deformation of Two-Dimensional Optical Lattice
Qiuyu Ling, Chunguang Hu, Ridong Zha, Xiaodong Hu, and Xiaotang Hu
A reflector is the core element of optical instruments, and the precision measurement of its shape has always been an important part of research areas. A method for rapid shape measurement based on the deformation of two-dimensional optical lattice is proposed based on the variable spatial periodic distribution opticalA reflector is the core element of optical instruments, and the precision measurement of its shape has always been an important part of research areas. A method for rapid shape measurement based on the deformation of two-dimensional optical lattice is proposed based on the variable spatial periodic distribution optical lattice generated by the modulation of optical fields. Based on the theory of geometric optics and space three-dimensional transformation, a mathematic correlation model between a two-dimensional optical lattice deformation and a three-dimensional shape of reflector is established. A surface reconstruction algorithm based on lattice centroid is proposed. The measurement range and single pixel resolution of the proposed measurement method are analyzed. The multi-dip angle experiments are carried out, and a submicron measurement of the reflector with a diameter of 10.5 mm is achieved. The feasibility of the method is verified when we compare the test data with the measurement data of the commercial interferometer. In addition, the method has the characteristics of high precision, fast speed and strong adaptability..
Acta Optica Sinica
- Publication Date: Apr. 09, 2018
- Vol. 38, Issue 1, 0112003 (2018)
Analysis of Attitude Measurement Accuracy and Indoor Evaluation Method of Photoelectric Theodolite
Huaixue Zhao, Liude Tian, Jianke Zhao, Xun Xue, Liang Pan, and Tao Wang
In order to realize indoor test and evaluation of attitude measurement accuracy of photoelectric theodolite, an attitude measurement method of photoelectric theodolite is developed. Based on Monte Carlo method, the error sources are analyzed. Main influencing factors on attitude measurement accuracy are obtained, and aIn order to realize indoor test and evaluation of attitude measurement accuracy of photoelectric theodolite, an attitude measurement method of photoelectric theodolite is developed. Based on Monte Carlo method, the error sources are analyzed. Main influencing factors on attitude measurement accuracy are obtained, and a detection method for indoor attitude measurement accuracy is proposed. Based on outfield theoretical trajectory, target attitude and measuring station coordinates, the original data of attitude measurement is obtained by inverse attitude measurement theory. The original data is input into the photoelectric theodolite to obtain the test target attitude. The theoretical target attitude and the test target attitude are compared, and the attitude measurement accuracy of the attitude measurement equipment is obtained. According to this method, the attitude measurement accuracy of a certain type of attitude measurement equipment is tested. Attitude measurement accuracy of the attitude measurement equipment can be obtained by experiments. The heading angle measurement error is not larger than 1.9°, pitch angle measurement error is not larger than 0.4°..
Acta Optica Sinica
- Publication Date: Mar. 28, 2018
- Vol. 38, Issue 1, 0112004 (2018)
Exposure Time Optimization for Line Structured Light Sensor Based on Light Stripe Reliability Evaluation
Taotao Li, Feng Yang, Ce Li, and Liang Fang
Optimization methods of camera's exposure time based on line structured light stripe reliability evaluation are studied, and the reliability evaluation results are used as reference indexes for optimization of exposure time. Firstly, existing light stripe reliability evaluation model is improved by combination withOptimization methods of camera's exposure time based on line structured light stripe reliability evaluation are studied, and the reliability evaluation results are used as reference indexes for optimization of exposure time. Firstly, existing light stripe reliability evaluation model is improved by combination with the characteristics that light stripe cross section obey Gaussian distribution, and then Gaussian reliability evaluation model is constructed. With the extraction method of sub-pixel light stripe center, light stripe centers are extracted from stripe images acquired with different exposure times. Extraction results are evaluated by Gaussian reliability evaluation model to obtain the values of evaluation reliability C and gray level R. Then, the influence mechanism of exposure time t on the evaluation results are analyzed respectively. Variation models of t-C and t-R are built, and the camera's optimal exposure time is finally obtained through analysis of variation models. Experiments take the high-precision spline and cement pavement model under light intensity of 230 lux as an experimental measurement object. Results show that measurement with the optimized exposure time is more reliable and more efficient. Mean residual sum of squares of the single light strip measurement is about 0.03 mm
2. The average texture depth of reconstructed model is only 9.8% away from actual model.
.
Acta Optica Sinica
- Publication Date: Mar. 29, 2018
- Vol. 38, Issue 1, 0112005 (2018)
Polarization Performance in Space Ultraviolet Remote Sensing Spectral Instruments
Hanshuang Li, Bo Li, and Shurong Wang
To improve the performance of instrument and the inversion of remote sensing data, we analyze the influence of instrument optical system films on polarization. The xenon lamp, collimation system, Brewster polarizer and ultraviolet spectrometer are used to build a set of polarization response testing system. P polarizedTo improve the performance of instrument and the inversion of remote sensing data, we analyze the influence of instrument optical system films on polarization. The xenon lamp, collimation system, Brewster polarizer and ultraviolet spectrometer are used to build a set of polarization response testing system. P polarized light and S polarized light polarization response characteristics of the instrument are measured in the range from 200 nm to 320 nm ultraviolet wavelength band. The test result indicates that the instrument shows different polarization responses under P polarized and S polarized light irradiation. When the polarization is changing from S to P, the peak wavelength of ultraviolet spectrometer response changes from 290 nm to 275 nm. Meanwhile, the energy of ultraviolet spectrometer under double pieces diffuser reduces by 40%~75% in comparison with single piece diffuser; under single piece diffuser and double pieces diffuser, spectrometer polarization response values both get maximum at 265 nm wavelength, while under double pieces diffuser, the polarization response of spectrometer is closer to unit value, and the variation of response to different polarization states is reduced, which is more suitable for the calibration requirement of the synchrotron radiation source..
Acta Optica Sinica
- Publication Date: Mar. 28, 2018
- Vol. 38, Issue 1, 0112006 (2018)
Lasers and Laser Optics
Theoretical Design and Experimental Research on High Power Yb∶YAG Ceramic Slab Laser Amplifier
Mi Li, Tangjian Zhou, Liu Xu, Qingsong Gao, Jian Zhang, Yingcheng Wu, Dan Wang, Hao Hu, Chun Tang, Yi Yu, Zhenhai Wu, Jianmin Li, Yong Shi, and Na Zhao
A Yb∶YAG ceramic slab is designed theoretically and fabricated, and the high power laser output is achieved at 1030 nm under room-temperature with InGaAs diode pumping, 1030 nm seed laser injecting and double-pass amplifying. The amplified laser power is 5.97 kW when the total pumping power is 19.98 kW and the injectedA Yb∶YAG ceramic slab is designed theoretically and fabricated, and the high power laser output is achieved at 1030 nm under room-temperature with InGaAs diode pumping, 1030 nm seed laser injecting and double-pass amplifying. The amplified laser power is 5.97 kW when the total pumping power is 19.98 kW and the injected power of the seed laser is 1.18 kW. The optical-to-optical conversion efficiency is 24.0% and the slope efficiency is 27.9%. The transmission wavefront of the Yb∶YAG ceramic slab is measured and the output powers with different coupling efficiencies and working temperatures are simulated. The experimental results show that the high power laser output can be achieved in Yb∶YAG under room-temperature with high intensity pumping and high intensity seed laser injecting..
Acta Optica Sinica
- Publication Date: Mar. 29, 2018
- Vol. 38, Issue 1, 0114001 (2018)
Machine Vision
Research on Parameter Calibration of Projection Correction System
Fan Yang, Cheng Han, Baoxing Bai, and Chao Zhang
In the process of the parameter calibration of projector camera system, the recognition accuracy of corner is low and the noise immunity is poor. To solve the above problems, a new projection color pattern feature image and a sub-pixel corner detection algorithm are introduced to increase the accuracy of corner detectiIn the process of the parameter calibration of projector camera system, the recognition accuracy of corner is low and the noise immunity is poor. To solve the above problems, a new projection color pattern feature image and a sub-pixel corner detection algorithm are introduced to increase the accuracy of corner detection and recognition. In the process of photon signal transmission, the projector-camera can cause photon signal loss due to the coupling of system channel, therefore, the system coupling is modeled and analyzed. And a system coupling correction scheme is proposed, which effectively reduces the system coupling crosstalk. In the process of calculating the system calibration parameters, due to the interference of external factors, the error of the calibration parameters of the projector is large. Considering that the projector camera has epipolar geometry constraint relationship, a projective geometry constrained optimization method based on imaging feedback is proposed to optimize the system parameters. The experimental results show that this method can achieve 0.25 pixel accuracy. Meanwhile, it has high plane parallelism and linear verticality. Projection distortion correction experiments show that the distortion correction effect of projection screen basically accords with human visual viewing consistency..
Acta Optica Sinica
- Publication Date: Mar. 28, 2018
- Vol. 38, Issue 1, 0115001 (2018)
Variable Weight Cost Aggregation Algorithm for Stereo Matching Based on Horizontal Tree Structure
Jianjian Peng, and Ruilin Bai
In the cost aggregation methods based on tree structure, the weight support region is selected only by color information, and therefore it is easy to produce mismatching problem in the image boundary area. A variable weight cost aggregation algorithm for stereo matching based on horizontal tree structure is proposed toIn the cost aggregation methods based on tree structure, the weight support region is selected only by color information, and therefore it is easy to produce mismatching problem in the image boundary area. A variable weight cost aggregation algorithm for stereo matching based on horizontal tree structure is proposed to solve the problem. The initial disparity value is obtained by the cost aggregation of horizontal tree, the horizontal tree is reconstructed with initial disparity value and color information, and the final disparity map is obtained on the updated tree structure by cost aggregation. In the disparity refinement stage, an improved non-local disparity refinement algorithm is proposed with the pixel points that do not satisfy left-right consistency constraint introduced into the matching cost volume, which improves the matching accuracy of final disparity map. Performance evaluation experiments on all 31 Middlebury stereo pairs demonstrate that the proposed algorithm achieves an average error matching rate of 6.96% in the non-occluded areas without disparity refinement, and the cost aggregation takes 1.52 s on average..
Acta Optica Sinica
- Publication Date: Mar. 28, 2018
- Vol. 38, Issue 1, 0115002 (2018)
RGB-D Scene Image Fusion Algorithm Based on Sparse Atom Fusion
Fan Liu, Pengyuan Liu, Junning Zhang, and Binbin Xu
To solve the problems of difficulty of feature fusion and low efficiency of joint recognition in color image and depth image(RGB-D), a new algorithm of RGB-D scene image fusion is proposed based on K singular value decomposition (KSVD) and maximum correlation minimum redundancy atoms (mRMR) principle. Firstly, the featTo solve the problems of difficulty of feature fusion and low efficiency of joint recognition in color image and depth image(RGB-D), a new algorithm of RGB-D scene image fusion is proposed based on K singular value decomposition (KSVD) and maximum correlation minimum redundancy atoms (mRMR) principle. Firstly, the features of the sparse KSVD image and the dictionary atoms corresponding to the sparse coefficients are used as the parameters of feature fusion to fully express the whole information of image. Secondly, the mRMR principle of mutual information is used to determine the characteristic atom combination which has minimum dimensions and minimum correlation among different dimensions. Finally, the sparse coefficients are fused by the maximization principle to obtain the effective information fusion between two images. Experimental results show that the proposed algorithm has advantages over principal component analysis-K singular value decomposition and non-subsampled contour transform-K singular value decomposition fusion algorithms in terms of information entropy, mutual information and edge preservation, which improves recognition accuracy and success rate of the image targets effectively..
Acta Optica Sinica
- Publication Date: Mar. 29, 2018
- Vol. 38, Issue 1, 0115003 (2018)
Dense Stereo Matching Based on Cross-Scale Guided Image Filtering
Jie Liu, Jianxun Zhang, Yu Dai, and He Su
To solve problems of the difficulty to meet the real-time requirements and the low matching accuracy of existing local stereo matching algorithms at some special regions, such as weak textured surfaces and the discontinuity boundary of depth, a dense stereo matching algorithm based on cross-scale guided image filteringTo solve problems of the difficulty to meet the real-time requirements and the low matching accuracy of existing local stereo matching algorithms at some special regions, such as weak textured surfaces and the discontinuity boundary of depth, a dense stereo matching algorithm based on cross-scale guided image filtering is proposed. An image segmentation technology is used to realize pre-segmentation of stereo images and the aggregation radius of pixels in the segmented region is obtained. This radius is used as a guide, and kernels with three different sizes are used to carry out filtering in the cost space of stereo image. The regularization term is introduced to ensure the consistency of the aggregated cost, so as to obtain a more efficient aggregate cost. A simple and efficient winner-take-all strategy is used to obtain the initial disparity. The experimental results based on Middlebury test bench show that the proposed algorithm has both real time capability and high efficiency..
Acta Optica Sinica
- Publication Date: Mar. 29, 2018
- Vol. 38, Issue 1, 0115004 (2018)
Materials
Effect of Polyethylene Glycol on Microstructure and Self-Cleaning Properties of Titanium Dioxide Films
Xilian Sun, Penghui Chen, Lang Zhou, and Mujahid Mohammad
By the sol-gel method, the polyethylene glycol (PEG2000) doped TiO2 films are prepared. The effects of additive amount of PEG2000 on the microstructure, surface morphologies, transmissivity, and self-cleaning properties of TiO2 films are investigated. With the ultraviolet lights as light sources, the effects of PEG2000By the sol-gel method, the polyethylene glycol (PEG2000) doped TiO2 films are prepared. The effects of additive amount of PEG2000 on the microstructure, surface morphologies, transmissivity, and self-cleaning properties of TiO2 films are investigated. With the ultraviolet lights as light sources, the effects of PEG2000 concentrations on the photocatalytic activity of TiO2 films are analyzed. The results show that all the structures of the prepared films are anatase; the microstructure of TiO2 films can be regulated and controlled by the regulation of the additive amount of PEG2000 and thus their optical and self-cleaning properties are controlled..
Acta Optica Sinica
- Publication Date: Mar. 29, 2018
- Vol. 38, Issue 1, 0116001 (2018)
Luminescence Properties and Ce
3+→Tb
3+ Energy Transfer in CaYAlO4∶Ce
3+, Tb
3+ Phosphors
Caihua Chen, Kai Chen, Lili Meng, Lixia Zhang, and Lifang Liang
CaY1-x-yAlO4∶xCe3+, yTb 3+ phosphors are synthesized by the sol-gel method. The effects of single-doped Ce3+ or Tb3+ rare earth ions and their co-doping on the luminescence properties of the phosphors are discussed. The results show that the synthesized phosphors are pure samples with the tetragonal structure. The CaY1CaY1-x-yAlO4∶xCe
3+, yTb
3+ phosphors are synthesized by the sol-gel method. The effects of single-doped Ce
3+ or Tb
3+ rare earth ions and their co-doping on the luminescence properties of the phosphors are discussed. The results show that the synthesized phosphors are pure samples with the tetragonal structure. The CaY1-xAlO4∶xCe
3+ phosphors emit blue light peaking at around 445 nm under an excitation wavelength of 368 nm. The CaY1-yAlO4∶yTb
3+ phosphors emit green light peaking at 418, 440, 491, 548, 589, and 625 nm under an excitation wavelength of 246 nm. In Ce
3+/Tb
3+ co-doped phosphors, the energy transfers from Ce
3+ to Tb
3+, which makes the luminescence of Tb
3+ enhanced. When the Ce
3+ and Tb
3+ co-doped phosphors are under an excitation wavelength of 368 nm or 378 nm, Tb
3+ emits a strong green light. The intensities of blue and green lights can be tuned by adjusting the doping concentrations of Ce
3+ and Tb
3+.
.
Acta Optica Sinica
- Publication Date: Mar. 29, 2018
- Vol. 38, Issue 1, 0116002 (2018)
Growth and Optical Properties of Lithium Tantalate Single Crystals Doped with Indium and Neodymium
Chongjun He, Weili Li, Jiming Wang, Xiaorong Gu, Tong Wu, and Youwen Liu
The congruent lithium tantalate (LiTaO3) single crystals doubly-doped with Nd3+ and In3+ ions are grown by the Czochralski method. The ultraviolet-visible absorption spectra of these single crystals are measured, the defect structures of these single crystals are analyzed, and the threshold of the doping concentration The congruent lithium tantalate (LiTaO3) single crystals doubly-doped with Nd
3+ and In
3+ ions are grown by the Czochralski method. The ultraviolet-visible absorption spectra of these single crystals are measured, the defect structures of these single crystals are analyzed, and the threshold of the doping concentration of In
3+ ion is obtained. When the doping concentration of In
3+ ion reaches this threshold, the optical damage resistance ability of In∶Nd∶LiTaO3 crystals enhances significantly. The replacement of the anti-site T
aLi4+ by In
3+ ions enhances the photo-conductivity of crystals and weakens the photorefractive effect. The full width at half maximum of the absorption peak of In∶Nd∶LiTaO3 crystals at the wavelength of 0.808 μm is 15 nm, and the absorption cross-section is 5.26×10
-21 cm
2. With a 0.808 μm semiconductor laser as the pumping source, a strong luminescence band of Nd
3+ ions appears at the wavelength of 1.06 μm. These study results show that the In∶Nd∶LiTaO3 crystals can be applied in high power photonic or integrated optoelectronic devices as the multi-functional crystals.
.
Acta Optica Sinica
- Publication Date: Mar. 29, 2018
- Vol. 38, Issue 1, 0116003 (2018)
Microscopy
Spot Array Optimization of Parallel Confocal Imaging Based on Digital Micromirror Device
Qian Zhu, Xibin Yang, Simin Li, Hui Li, Chi Wang, Shoupeng Liu, Junming Jian, and Daxi Xiong
The flexibility of a digital micromirror device (DMD) helps to realize parallel confocal imaging. A parallel confocal imaging system based on DMD is designed and built. The influences of DMD spot array on axial resolution, lateral resolution and image contrast are analyzed to obtain the best spot array parameters. ResuThe flexibility of a digital micromirror device (DMD) helps to realize parallel confocal imaging. A parallel confocal imaging system based on DMD is designed and built. The influences of DMD spot array on axial resolution, lateral resolution and image contrast are analyzed to obtain the best spot array parameters. Results show that, the smaller the spot size is, the higher the lateral and axial resolution are. When the spot distance is larger than the spot size, the imaging horizontal resolution is not improved obviously with the increasing distance between spots. The imaging contrast is the highest when the spot interval equals to four times of spot size for 1×1 micromirror. That is to say, the optimal spot array is that spot size equals to 1×1 and spot interval equals to four times of spot size. For an objective lens with a numerical aperture of 0.25, the lateral resolution of optimal spot array is superior to 512 lp/mm, and its axial resolution can reach 7.82 μm, which reaches diffraction limit. When the optimal spot array is used to image three-dimensional body grating, it has higher resolution and obvious optical sectioning effect than that of wide field imaging, and has no much difference compared with that of laser scanning confocal imaging. The parallel confocal imaging system based on DMD achieves optical sectioning imaging with high resolution and high imaging contrast on the premise of high speed imaging. It has certain advantages and application prospects in real-time imaging and three-dimensional imaging..
Acta Optica Sinica
- Publication Date: Mar. 29, 2018
- Vol. 38, Issue 1, 0118001 (2018)
Nonlinear Optics
Generation and Propagation Regulation of Airy Solitons in Saturable Nonlinear Medium
Weijun Chen, Jikai Yang, Chunyang Liu, Liankai Wang, Yining Mu, and De Song
The generation and propagation regulation of Airy solitons in saturable nonlinear medium are numerically investigated by split-step Fourier method. For a single incident Airy beam, stably propagated breathing solitons are generated within a certain initial amplitude range. The intensity of solitons increases and breathThe generation and propagation regulation of Airy solitons in saturable nonlinear medium are numerically investigated by split-step Fourier method. For a single incident Airy beam, stably propagated breathing solitons are generated within a certain initial amplitude range. The intensity of solitons increases and breathing period decreases with the increase of initial amplitude, but the solitons width remains unchanged. With the increase of decay coefficient, mean peak intensity of the solitons has two extreme values, and it is found to first increase, then decrease and increase again. Left tilted Airy solitons can be generated with a negative launch angle, and right tilted Airy solitons can be generated with a positive launch angle. When two incident Airy beams interact with each other, the interaction can be weakened with the same negative launch angles, and the interaction can be strengthened with the same positive launch angles. Furthermore, the propagation direction of solitons or soliton pairs can be controlled by different launch angles..
Acta Optica Sinica
- Publication Date: Mar. 29, 2018
- Vol. 38, Issue 1, 0119001 (2018)
Optical Design and Fabrication
Enhancement of Light Extraction Efficiency of LED by Bionic Moth-Eye Structure with Frustum of a Cone
Shunrui Liu, Li Wang, Yanjun Sun, Jun Wang, Yue Wang, Tianqi Wu, Yanbing Leng, and Lianhe Dong
In order to improve the light extraction efficiency of light-emitting diode (LED), according to the equivalent medium theory, microstructure array with frustum of a cone is designed and fabricated in the LED passivation layer (SiNx) surface. The influence of the fill factor of the bottom surface, bottom diameter, heighIn order to improve the light extraction efficiency of light-emitting diode (LED), according to the equivalent medium theory, microstructure array with frustum of a cone is designed and fabricated in the LED passivation layer (SiNx) surface. The influence of the fill factor of the bottom surface, bottom diameter, height and angle of the micro structure on the light extraction efficiency of LED is emphatically analyzed through simulation.to improve light extraction efficiency of LED. The results show that when the micro structure of the fill factor of the bottom surface is 0.55, the radius of bottom surface is 220 nm, the height is 245 nm, and the side slope angle is 70°, the light extraction efficiency of the device is optimized. Which is 4.85 times as much as the device without surface micro structure. The sub-wavelength nanostructure is prepared on the surface of LED passivation layer by nanosphere lithography technology, and the comparison test of electroluminescent between the proposed structure and LED chip without surface micro structure is carried out. The results show that the luminous efficiency of the samples with micro structure at 20 mA and 150 mA working current are 4.41 times and 4.36 times of the reference samples without micro structure. The calculated results and the experimental results are consistent, which means that the structure produced by the LED passivation layer can effectively improve the light extraction efficiency..
Acta Optica Sinica
- Publication Date: Mar. 29, 2018
- Vol. 38, Issue 1, 0122001 (2018)
Optical Devices
Slotted and Staggered Design of LED Sunflower Radiator
Fan Tang, and Zhenning Guo
In order to enhance the cooling capacity of the light emitting diode (LED) radiator and reduce the weight of it, a slotted and staggered design is incorporated into the traditional LED sunflower radiator. The three-dimensional model of radiator is built by Solidworks software, and thermal simulation is carried out by FIn order to enhance the cooling capacity of the light emitting diode (LED) radiator and reduce the weight of it, a slotted and staggered design is incorporated into the traditional LED sunflower radiator. The three-dimensional model of radiator is built by Solidworks software, and thermal simulation is carried out by Flow Simulation, which is the plug of Solidworks. Using the traditional sunflower radiator as a basic model, the average error between the actual temperature of the four monitoring points and the simulated temperature is 4.6%, which is within the allowable range. This result confirms the correctness of the simulation steps. Then, the influences of number and length of seams on the highest temperature of LED chip are studied, and the results show that the slotted and staggered design effectively enhances the convection cooling performance of the LED radiator. The highest temperature of the LED chip is 122.15 ℃ while the input power is 26 W, the number of seams is 9 and the length of seams is 1 mm. Under the same set of model parameters, the highest temperature of the LED with slotted and staggered radiator is reduced by 8.68 ℃ compared to the one with traditional sunflower radiator, and the weight of radiator is also reduced by 6.85 g. The slotted and staggered design is in favor of delaying the forming of thermal boundary layer and improving distribution of flow field, which enhances the cooling capacity and reduces the weight of sunflower radiator under the nature convection conditions..
Acta Optica Sinica
- Publication Date: Mar. 28, 2018
- Vol. 38, Issue 1, 0123001 (2018)
Ultra-Broadband Infrared Absorber Based on LiF and NaF
Xi Chen, Wenrui Xue, Chen Zhao, and Changyong Li
Grating-type ultra-broadband infrared absorber based on LiF and NaF is designed, and its absorption characteristics are researched by using finite-difference frequency-domain method. Research results show that grating-type absorbers consist of LiF(or NaF) and dielectric material, and they all have wider absorption bandGrating-type ultra-broadband infrared absorber based on LiF and NaF is designed, and its absorption characteristics are researched by using finite-difference frequency-domain method. Research results show that grating-type absorbers consist of LiF(or NaF) and dielectric material, and they all have wider absorption band. The absorption bands are located at different infrared wavebands. The two absorption bands can be connected by using LiF, NaF and dielectric material together in the absorber. In the range of incident wavelength of 15-45 μm and the range of incident angle of 0°-80°, the absorptivity of the absorber is more than 80% with the optimization of parameters, which realizes broadband absorption. The layer number of the composite layer has the biggest effect on the absorptivity, and the minimal effect is the thickness of the dielectric layer..
Acta Optica Sinica
- Publication Date: Mar. 28, 2018
- Vol. 38, Issue 1, 0123002 (2018)
Optics at Surfaces
Graphene Surface Plasmon Polaritons Based Photoelectric Modulator with Double Branched Structure
Zhiquan Li, Dandan Feng, Xin Li, Landi Bai, Tonglei Liu, Zhong Yue, and Erdan Gu
A graphene/dielectric/graphene sub-wavelength waveguide structure with double branched structure is constructed. The frequency-selection characteristic of branch structure is combined with the electrical tunable characteristic of graphene, and the dynamic modulation of the intensity of incident light from visible lightA graphene/dielectric/graphene sub-wavelength waveguide structure with double branched structure is constructed. The frequency-selection characteristic of branch structure is combined with the electrical tunable characteristic of graphene, and the dynamic modulation of the intensity of incident light from visible light to mid-infrared can be achieved. Surface plasmon polaritons keep the light energy within the nanoscale dielectric slit, which causes the modulator to break the diffraction limit and enhance the interaction between graphene and light. Effects of the chemical potential, branch length and dielectric material of graphene on the output light intensity of the waveguide structure are analyzed by finite element method. Simulation results indicate that, when the incident light wavelength is 1550 nm, the branch length is 315 nm and the chemical potential decreases from 0.80 eV to 0.78 eV, the extinction ratio reaches 6.77 dB. Compared with the conventional modulator, the proposed photoelectric modulator can guarantee the high extinction ratio and modulation efficiency, and it is small in size and the structure is compact and simple, which can meet the requirements of large scale integration applications..
Acta Optica Sinica
- Publication Date: Apr. 11, 2018
- Vol. 38, Issue 1, 0124001 (2018)
Physical Optics
Multiple-Component Polarized Bidirectional Reflectance Distribution Function Model for Painted Surfaces Based on Kubelka-Munk Theory
Min Yang, Yonghua Fang, Jun Wu, Fangxiao Cui, Dacheng Li, Yue Wu, and Tao Wang
To represent scattering polarization properties of painted surfaces, a multiple-component polarized bidirectional reflectance distribution function (BRDF) model is established on the basis of the Kubelka-Munk (KM) theory with the consideration of surface scattering and volume scattering. The model introduces the mirrorTo represent scattering polarization properties of painted surfaces, a multiple-component polarized bidirectional reflectance distribution function (BRDF) model is established on the basis of the Kubelka-Munk (KM) theory with the consideration of surface scattering and volume scattering. The model introduces the mirror parameter to characterize surface scattering contributions, and improves the traditional polarized BRDF model to make the new polarized BRDF model containing five parameters (real and imaginary parts of complex refractive index, surface roughness, relative diffuse reflectance coefficient, and mirror parameter) more consistent with the actual scattering polarization of painted surfaces. The degrees of polarization of black and green painted surfaces at different observation geometries are obtained by the outdoor experiment. The genetic algorithm is used to obtain key parameters based on measured data. The results show that the simulated results coincide with the experimental data for different painted surfaces, and the accuracy is improved by the introduction of mirror parameter. This work can be used as a basis for the extraction and effective identification of painted target polarization feature..
Acta Optica Sinica
- Publication Date: Mar. 29, 2018
- Vol. 38, Issue 1, 0126002 (2018)
Quantum Optics
Entanglement Evolution Characteristics of Quantum Rabi Models with Two Arbitrary Qubits
Yuhu Xu, Xuezao Ren, and Xueying Liu
The entanglement dynamics in a two-qubit Rabi model is discussed by the extended coherent states (ECS) method. The two qubits are initially prepared in an exchange-symmetric Bell state and the initial state of the light field is the vacuum state. The entanglement evolution characteristics are analyzed under different tThe entanglement dynamics in a two-qubit Rabi model is discussed by the extended coherent states (ECS) method. The two qubits are initially prepared in an exchange-symmetric Bell state and the initial state of the light field is the vacuum state. The entanglement evolution characteristics are analyzed under different transition frequencies of qubits and different coupling strengths between light fields and qubits. The results show that, in the case of weak coupling, when the differences between the transition frequencies of two identical qubits and the frequency of the light field are equal, the entanglement evolution is almost identical. When the transition frequencies of two non-identical qubits are symmetrically detuned relative to the frequency of the light field, the entanglement degree is larger than that for two identical qubits; the larger the detuning is, the stronger the entanglement is, and the entanglement evolution period has an inverse relationship with the detuning. Under the resonance conditions and when the coupling strengths are different, the phenomenon of the principal peaks and the secondary peaks appearing alternately in the entanglement evolution process of two qubits. If the coupling strength between one qubit and the light field is kept to be constant, the stronger the coupling strength of the other qubit is, the higher the secondary peaks become but, the principal peaks always reach the maximum entanglement. The entanglement evolves periodically in the whole process..
Acta Optica Sinica
- Publication Date: Mar. 29, 2018
- Vol. 38, Issue 1, 0127001 (2018)
Remote Sensing and Sensors
Atmospheric Correction Method for Sentinel-2 Satellite Imagery
Wei Su, Mingzheng Zhang, Kunping Jiang, Dehai Zhu, Jianxi Huang, and Pengxin Wang
Sentinel-2 is the second satellite of the world's environmental and safety monitoring system ‘Copernicus plan’, and it is an important data source for future remote sensing applications with high temporal-spatial resolution image. The simplified model for atmospheric correction (SMAC), 6S model and Sen2cor method aSentinel-2 is the second satellite of the world's environmental and safety monitoring system ‘Copernicus plan’, and it is an important data source for future remote sensing applications with high temporal-spatial resolution image. The simplified model for atmospheric correction (SMAC), 6S model and Sen2cor method are used to carry out atmospheric correction for Sentinel-2 satellite imagery. The upper atmospheric apparent reflectance is converted to surface reflectance, and analysis combining with measured spectral data of ground objects is carried out. After the atmospheric correction of Sentinel-2 satellite image, the spectral curves of the image and measured objects have the same change tendency with a high fitting degree. The atmospheric correction results of three models have strong correlation and high precision. The accuracy of Sen2cor method is the highest, whose determination coefficient (R2) is 0.8196, and root-mean-square error (Ermse) is 0.0388, followed by 6S model and SMAC. From the analysis of normalized differential vegetation index (NDVI), we find that NDVI values calculated by SMAC have the highest correlation with measured values, whose R2 is 0.6389, and Ermse is 0.093, followed by 6S model and Sen2cor method. Results show that the atmospheric correction accuracy of three methods is high. When the sentinel-2 satellite imagery is corrected, the image quality is improved obviously, and the availability is increased.
.
Acta Optica Sinica
- Publication Date: Mar. 28, 2018
- Vol. 38, Issue 1, 0128001 (2018)
Acquisition Method of Zero Stadia Standard Image for Satellite Imaging Simulation
Lanxia Wang, Wenyu Cui, Weining Yi, Honglian Huang, and Chuan Chen
Full link simulation of high resolution satellite imaging is the main means to evaluate the effect of satellite pre-launch. The zero stadia standard image is the necessary standard to verify the accuracy of the basics on imaging simulation link. When the ground equipment acquires zero stadia image, it is difficult to oFull link simulation of high resolution satellite imaging is the main means to evaluate the effect of satellite pre-launch. The zero stadia standard image is the necessary standard to verify the accuracy of the basics on imaging simulation link. When the ground equipment acquires zero stadia image, it is difficult to obtain zero stadia standard image directly by vertical observation to earth because of the problems such as the inconformity of the observation angle and the satellite, the heavy workload and difficulty of qualification. Through the establishment of ground zero stadia standard measurement system, vertical image with wide width is obtained by rail line shooting, geometric correction and image mosaic. Then, the zero stadia reflectance image is obtained by quantifying the synchrotron radiation correction method. Finally, on the observation platform 2.6 m away from the ground, the zero stadia standard image (reflectivity image) with the area of 10 m×10 m and the resolution of sub-meter level is obtained. Compared with the reflectance of the ground testing, the results show that the error of the zero stadia standard image (reflectivity image) is less than 5%, which can provide a standard for the accuracy verification of basic link of sub-meter high resolution satellite imaging simulation link..
Acta Optica Sinica
- Publication Date: Mar. 29, 2018
- Vol. 38, Issue 1, 0128002 (2018)
Study on Matched Filtering Process Based on Long-Range Pulsed Laser Heterodyne Detection
Shisong Wu, Heyong Zhang, Tingfeng Wang, Jin Guo, Chunhui Yan, and Tao Lü
Based on the long-range pulsed laser heterodyne detection system, the expression of signal and noise of the system is deduced. The matched filtering algorithm processing of the pulsed laser heterodyne detection system is given. The detailed application process of matched filtering technique in target detection of mediuBased on the long-range pulsed laser heterodyne detection system, the expression of signal and noise of the system is deduced. The matched filtering algorithm processing of the pulsed laser heterodyne detection system is given. The detailed application process of matched filtering technique in target detection of medium-range missiles and international space station is simulated. The influence of the target range, the scattering cross section area and the digital sampling rate on the detection capability is analyzed. The simulation results show that, under the digital processing capability of 100 MHz sampling rate, the Monte Carlo simulation of 500 matching filtering process is carried out. For the medium-range missile with the scattering cross section area of 5 m
2 and the distance of 100 km, the carrier-to-noise ratio of echo signal is 3.29 dB, the carrier-to-noise ratio of echo signal after matched filtering is 25.13 dB, the signal strength increases 152 times, the range accuracy is 27 m and the range rate accuracy is 0.17 m/s. For the international space station with the scattering cross section area of 100 m
2 and the distance of 500 km, the carrier-to-noise ratio of the echo signal is -6.12 dB, the carrier-to-noise ratio of the echo signal after matched filtering is 18.49 dB, the signal strength increases 289 times, the range accuracy is 117 m and the range rate accuracy is 2.1 m/s. The smaller the target range is, the larger the radar cross section area is, and the higher the digital sampling rate is, the stronger the ability of the matched filtering to extract and enhance the signal is.
.
Acta Optica Sinica
- Publication Date: Mar. 29, 2018
- Vol. 38, Issue 1, 0128003 (2018)
Sensitivity of Intercalibration Uncertainty on Spectral Sampling of Space-Based Radiance Standard
Shenwei Chen, Na Xu, Tie Dai, Xinyi Zhou, Hao Lü, and Yueming Cheng
The space-based radiance standard is of great significance for the study of the satellite observing climate change. The establishment of the space-based radiance standard can not only improve the relative accuracy of satellite observations, but also meet the traceable needs of other satellites through intercalibration.The space-based radiance standard is of great significance for the study of the satellite observing climate change. The establishment of the space-based radiance standard can not only improve the relative accuracy of satellite observations, but also meet the traceable needs of other satellites through intercalibration. The spectral resolution of the hyperspectral standard remote sensor in space for intercalibration has a significant effect on the intercalibration relative accuracy. The simulations of spectral radiances by modes of MODTRAN and AER LBL are used as proxy data of the hyperspectral remote sensor in reflective solar bands and thermal emissive bands, respectively. The influence of spectral sampling on the observation of spectral radiation and the uncertainty of the radiation standard intercalibration caused by the spectral sampling are analyzed. Considering five kinds of underlying surfaces and six kinds of atmospheric conditions, the difference of spectral radiation under different spectral sampling frequencies is compared, and the spectral uncertainty of the space-based radiance standard intercalibration is evaluated with the utilization of the sensitivity experiment method with MERSI-II as the target remote sensor. The results show that the larger the spectral sampling frequency, the greater the difference in spectral radiation. The maximum radiation difference is up to 100% in atmospheric absorption spectra, low signal spectra, and near ultraviolet solar dark-line spectra. In the atmospheric window, the spectral sampling frequency better than 4 nm can produce radiance to meet the on-obit intercalibration standard with an uncertainty less than 0.3% in reflective solar bands, and the spectral sampling frequency better than 2 cm
-1 can also produce radiance temperature to meet the on-obit intercalibration standard with an uncertainty less than 0.1 K in thermal emissive bands. In the near ultraviolet solar dark-line spectra and the atmospheric absorption region, the intercalibration of reflective solar bands is very sensitive to the spectral sampling. The uncertainty of intercalibration is up to 40% at a sampling frequency of 4 nm in the channel with a central wavelength of 1.38 μm. The spectral sampling of 0.8 cm
-1 can produce radiance temperature to meet the on-obit intercalibration standard with an accuracy of 0.1 K in the weak atmospheric absorption channel with a central wavelength of 7.2 μm in thermal emissive bands.
.
Acta Optica Sinica
- Publication Date: Apr. 11, 2018
- Vol. 38, Issue 1, 0128004 (2018)
Cloud Detection of ZY-3 Satellite Remote Sensing Images Based on Deep Learning
Yang Chen, Rongshuang Fan, Jingxue Wang, Wanyun Lu, Hong Zhu, and Qingyuan Chu
The cloud detection method of ZY-3 satellite remote sensing images based on deep learning is proposed to solve the problem of the images with few image bands and limited spectral range. Firstly, we obtain the feature of remote sensing images measured with the unsupervised pre-training network structure of principal comThe cloud detection method of ZY-3 satellite remote sensing images based on deep learning is proposed to solve the problem of the images with few image bands and limited spectral range. Firstly, we obtain the feature of remote sensing images measured with the unsupervised pre-training network structure of principal component analysis. Secondly, we put forward the adaptive pooling model, which can well mine images in order to reduce the loss of image feature information in the pooling process. Finally, the image features are input into the support vector machine classifier to obtain the cloud detection results. The typical regions are selected for cloud detection experiments, and the detection results are compared with that of the traditional Otsu method. The results show that the proposed method has high detection precision and is not limited by the spectral range, and it can be used for the multi-spectral and panchromatic images cloud detection of ZY-3 satellite..
Acta Optica Sinica
- Publication Date: Mar. 29, 2018
- Vol. 38, Issue 1, 0128005 (2018)
Scattering
Measurement and Light Focusing by Transmission Matrices of Scattering Media Based on Phase-Only Modulation
Ming Zhao, Meijing Zhao, Chengwei Sun, and Wenhai Xu
The general measurement method of transmission matrices based on phase-only modulation is proposed and the experimental setup is established for the measurement of the transmission matrices. The identity matrix modulation and the Hadamard matrix modulation are employed respectively in the measurement of the transmissioThe general measurement method of transmission matrices based on phase-only modulation is proposed and the experimental setup is established for the measurement of the transmission matrices. The identity matrix modulation and the Hadamard matrix modulation are employed respectively in the measurement of the transmission matrices, and the focusing of light waves through scattering media is realized. The experimental results show that the focusing point intensity of the transmission matrix measured based on the identity matrix is 19 times the background light intensity, while the focusing point intensity of the transmission matrix measured based on the Hadamard matrix is 16 times the background light intensity..
Acta Optica Sinica
- Publication Date: Mar. 28, 2018
- Vol. 38, Issue 1, 0129001 (2018)
Ultrafast Optics
Intense Femtosecond Filamentation by Superposed Gaussian Beam
Zhenming Song, Sen Yang, Hui Gao, and Takashi Nakajima
Femtosecond pulse filamentation has wide applications in many fields. Extending the lengths of filamentation and accompanied plasma channel are the key to application. By solving the extended nonlinear Schr dinger equation coupled with the electron density equation, we can get the following conclusion that the performaFemtosecond pulse filamentation has wide applications in many fields. Extending the lengths of filamentation and accompanied plasma channel are the key to application. By solving the extended nonlinear Schr dinger equation coupled with the electron density equation, we can get the following conclusion that the performance of femtosecond filamentation and plasma channels in Kerr media can be significantly improved if an superposed Gaussian beam with the same energy is used instead of an ordinary single Gaussian beam as the incident beam. According to theoretical calculation of the upper threshold power for self-focusing, the self-focusing upper threshold power of superposition Gaussian beam is larger than that of single Gaussian beam. Hence, superposed Gaussian beam as incident beam is particularly useful to extend the filament length and avoid multi-filamentation when the incident pulse energy is high..
Acta Optica Sinica
- Publication Date: Mar. 29, 2018
- Vol. 38, Issue 1, 0132001 (2018)
Vision, Color, and Visual Optics
Color Fusion Algorithm of Dual-Band Images Based on CbCr Look-up Table
Bingyang He, Zhiquan Zhang, Qiang Li, and Xiaoyu Jiang
Natural color fusion of low-light visible images and infrared images can significantly improve abilities of human vision for situation perceiving and targets detecting in low-light environment. Sample-based color fusion is a fast, effective and real-time natural color fusion algorithm. In view of the problems of existiNatural color fusion of low-light visible images and infrared images can significantly improve abilities of human vision for situation perceiving and targets detecting in low-light environment. Sample-based color fusion is a fast, effective and real-time natural color fusion algorithm. In view of the problems of existing algorithms in construction of color look-up table and utilization of grayscale information, we propose a new color fusion algorithm of dual-band images based on CbCr look-up table. We obtain the mapping f(Y1,Y2)→(Cb,Cr) between luminance and chromaticity by using the back propagation neural network to nonlinearly fit the two-dimensional luminance vector (Y1,Y2) and the two-dimensional chromaticity vector (Cb,Cr) of image simples, and construct the CbCr look-up table based on the mapping. When color fusing, the chromaticity Cb,Cr of fused image are obtained by the CbCr look-up table and the input luminance Y1,Y2 of dual-band grayscale images. The luminance YF of fused image is obtained by the image fusion of luminance Y1,Y2 based on two-layer Laplacian pyramid transformation. The luminance Y1,Y2 are calibrated to diminish color mapping errors owing to environmental changes. The experimental results show that the fused images based on proposed algorithm have natural color, rich details and are more conducive to (hot) targets detection. The dual-band fusion results obtained by the proposed algorithm are almost as good as or even better than the fusion results by Toet method in definition, colorfulness, and mapping accuracy..
Acta Optica Sinica
- Publication Date: Mar. 28, 2018
- Vol. 38, Issue 1, 0133001 (2018)
X-Ray Optics
Small-Angle X-Ray Scattering Tomography Based on Micro-Focusing Kirkpatrick-Baez Mirrors
Tao Hu, Wenqiang Hua, Yudan Wang, Yuzhu Wang, Ping Zhou, Chunxia Hong, Fenggang Bian, and Tiqiao Xiao
Small-angle X-ray scattering tomography (SAXS-CT) is a non-destructive structural characterization method for nanostructure analysis of heterogeneous materials and its space distribution. The SAXS-CT system based on micro-focusing Kirkpatrick-Baez (KB) mirrors is developed at Shanghai Synchrotron Radiation Facility (SSSmall-angle X-ray scattering tomography (SAXS-CT) is a non-destructive structural characterization method for nanostructure analysis of heterogeneous materials and its space distribution. The SAXS-CT system based on micro-focusing Kirkpatrick-Baez (KB) mirrors is developed at Shanghai Synchrotron Radiation Facility (SSRF). Samples of Phyllostachys edulis and injection-molded polylactic acid are chosen for experimental verification. The results show that the spot size of the SAXS-CT system can be focused below 20 μm. For the Phyllostachys edulis sample, the position distribution and scattering difference of vascular bundle and parenchyma cell, and the orientation characteristic of nano-fibers are obtained. For the injection-molded polylactic acid sample, the lamella structure inside the sample exhibits the layered distribution characteristic, and the distribution and long spacing of lamella is acquired. The experimental results confirm the reliability and practicality of the SAXS-CT system..
Acta Optica Sinica
- Publication Date: Mar. 29, 2018
- Vol. 38, Issue 1, 0134001 (2018)
© Copyright 2018-2021 | Chinese Laser Press. All Rights Reserved 沪ICP备15018463号-20