Journals >Laser & Optoelectronics Progress
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2017
Volume: 54 Issue 10
60 Article(s)
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Atmospheric Optics and Oceanic Optics
Design of Underwater Zoom Lens for Marine Monitoring
Ma Haikuan, Cao Xuan, Chu Dongzhi, Wu Ning, Ma Ran, Zhang Shuwei, and Shi Qian
In order to monitor the working status of marine ecological monitoring instruments, a three-gear zoom optical system with large relative aperture is designed. This system is designed with Zemax software and its total length is 200 mm. The system uses a 6.4 mm×4.8 mm CCD camera, and the three-gear zoom focal lengthIn order to monitor the working status of marine ecological monitoring instruments, a three-gear zoom optical system with large relative aperture is designed. This system is designed with Zemax software and its total length is 200 mm. The system uses a 6.4 mm×4.8 mm CCD camera, and the three-gear zoom focal lengths are 8, 14, and 28 mm, respectively. The relative aperture remains at 1/1.4 during zoom process. The maximum field of view is 52° with short focus. At maximum field angle, when the Nyquist frequency is 42 lp/mm, the modulation transfer function (MTF) of the system at 0 field of view is 0.8, the average MTF is 0.7 at 0.707 field of view, and the average MTF value at 1 field of view reaches 0.6. In 10 μm range, the diffraction encircled energy is 90%, and distortion control is in a reasonable range. The system has high zoom ratio, simple structure and large relative aperture. It is suitable for monitoring the marine ecological monitoring instruments and can timely feedback their working status information. Therefore it greatly reduces the maintenance cost of marine ecological monitoring equipment..
Laser & Optoelectronics Progress
- Publication Date: Jan. 01, 1900
- Vol. 54, Issue 10, 100101 (2017)
Atomic and Molecular Physics
Temperature Measurement Technology Based on Double Line of Atomic Emission Spectra
Hu Xiaotao, Hao Xiaojian, and Duan Xianggang
Based on the temperature measurement principles of double line of atomic emission spectrum, the photoelectric pyrometer based on silicon photomultiplier is proposed, and the structure and temperature measurement principle of the photoelectric pyrometer are introduced. Al I 690.6 nm and Al I 708.5 nm are selected from tBased on the temperature measurement principles of double line of atomic emission spectrum, the photoelectric pyrometer based on silicon photomultiplier is proposed, and the structure and temperature measurement principle of the photoelectric pyrometer are introduced. Al I 690.6 nm and Al I 708.5 nm are selected from the atomic spectra database as the temperature measurement element spectral lines. The temperatures of aluminum burnt in pure oxygen are obtained by photoelectric thermometer and compared with temperatures measured by the thermocouple. The results show that the average relative error of temperatures measured by the two methods is 1.5%, which proves the feasibility of the proposed method..
Laser & Optoelectronics Progress
- Publication Date: Jan. 01, 1900
- Vol. 54, Issue 10, 100201 (2017)
Parallel Implementation of Synthetic Aperture Imaging Algorithm for Endoscopic Ultrasound
Li Wei, Chen Xiaodong, Li Jiake, Wang Yi, and Yu Daoyin
In order to improve the computational efficiency of synthetic aperture imaging algorithm in the medical endoscopic ultrasound system, the synthetic aperture imaging approach with parallel implementation on graphics processing unit (GPU) is proposed. Firstly, the basic principle and image reconstruction process of synthIn order to improve the computational efficiency of synthetic aperture imaging algorithm in the medical endoscopic ultrasound system, the synthetic aperture imaging approach with parallel implementation on graphics processing unit (GPU) is proposed. Firstly, the basic principle and image reconstruction process of synthetic aperture algorithm are introduced. Then, the algorithm is analyzed in parallel processing. Finally, synthetic aperture imaging algorithm for endoscopic ultrasound based on GPU is implemented by using the flexible architecture of single instruction multiple threads (SIMT) of compute unified device architecture (CUDA) programming mode. Multiple simulation experiments of scattering points imaging are compared and analyzed, and the imaging experiment verifications of iron wire, cyst prosthesis and pigskin tissue are carried out by using a self-built endoscopic ultrasound experimental system. The experimental results show that the proposed method can greatly improve the computational efficiency while keeping the same imaging quality and results. When the calculated data size is 1.47 GB (5305×581×64×8 byte), the maximum speedup ratio reaches 50.93..
Laser & Optoelectronics Progress
- Publication Date: Jan. 01, 1900
- Vol. 54, Issue 10, 102001 (2017)
Detectors
Effects of Bias Spectral Characteristics on Spectral Response of Solar Cells
Shi Qiang, Bian Jieyu, and Liu Zhengxin
Using monocrystalline silicon, multicrystalline silicon and simulated amorphous silicon solar cells as research objects, we study the influences of bias spectral characteristics such as irradiance and spectral distribution on the spectral response (SR) of solar cells. The SR of solar cells is related to the bias light.Using monocrystalline silicon, multicrystalline silicon and simulated amorphous silicon solar cells as research objects, we study the influences of bias spectral characteristics such as irradiance and spectral distribution on the spectral response (SR) of solar cells. The SR of solar cells is related to the bias light. The SR at long wavelength region increases and the short-circuit current of solar cell increases linearly with the increase of irradiance of bias light. The spectral distribution of bias light also has influence on the SR of solar cell. Large spectral mismatch degree induces large difference in SR measurement. Therefore, the irradiance and spectral distribution of bias light should be as close as possible to the IEC standard in order to improve the accuracy of SR measurement of solar cells..
Laser & Optoelectronics Progress
- Publication Date: Jan. 01, 1900
- Vol. 54, Issue 10, 100401 (2017)
Distributed Particle Swarm Optimization Target Tracking Based on Pyroelectric Sensing
Wang Zebing, Cui Baozhen, Qin Li, and Yang Wei
The direction angle sequence of the target is collected by the pyroelectric infrared sensing equipment, and the target tracking scheme without distance measuring is realized with the help of particle swarm optimization (PSO) algorithm. When the array layout is large, the collected length of direction angle sequence incThe direction angle sequence of the target is collected by the pyroelectric infrared sensing equipment, and the target tracking scheme without distance measuring is realized with the help of particle swarm optimization (PSO) algorithm. When the array layout is large, the collected length of direction angle sequence increases, the dimension of algorithm search space increases, and the tracking precision decreases. Through splitting sequence, the distributed particle swarm optimization algorithm (DPSO) integrated multi-node cooperative decision is used to realize the real-time target tracking in the large array of infrared detecting system. And the tracking accuracy meets the requirements. The experimental results show that the proposed method can effectively extend the application of the basic PSO algorithm in pyroelectric sensing..
Laser & Optoelectronics Progress
- Publication Date: Jan. 01, 1900
- Vol. 54, Issue 10, 100402 (2017)
Diffraction and Gratings
Design and Optimization of Wavelength Tunable Guide Mode Resonance Filter
Jiang Xiaowei, Wu Hua, and Wang Fei
Based on liquid crystal, a wavelength tunable guide mode resonance filter (WTGMF) with a center wavelength of 1.55 μm is designed and optimized by using the rigorous coupled wave method. From calculation, the thicknesses of anti-reflection layer and substrate both have influence on the resonance line width of the filteBased on liquid crystal, a wavelength tunable guide mode resonance filter (WTGMF) with a center wavelength of 1.55 μm is designed and optimized by using the rigorous coupled wave method. From calculation, the thicknesses of anti-reflection layer and substrate both have influence on the resonance line width of the filter. The thinner the thickness of anti-reflection layer is, the wider the resonance line width is. However, there is always an optimum substrate thickness to minimize the line width. When the substrate thickness is 300 nm, the resonance width is the narrowest with only 0.96 nm. In addition, the main factor that determine the wavelength tuning range of WTGMF is the thickness of the liquid crystal layer. The tuning range increases with the increase of the thickness of the liquid crystal layer and finally reaches stability. When the thickness of the liquid crystal layer reaches 1600 nm, the wavelength tuning range reaches the maximum of 39 nm..
Laser & Optoelectronics Progress
- Publication Date: Jan. 01, 1900
- Vol. 54, Issue 10, 100501 (2017)
Fiber Optics and Optical Communications
Reconfigurable Optical Add-Drop Multiplexer Based on Space Division Multiplexing
Yang Kang, Li Guoyu, Li Yan, Zhang Mu, and Jia Sumei
In order to meet the requirements of uploading and downloading large-capacity data in all-optical networks, a reconfigurable optical add-drop multiplexer (ROADM) based on wavelength division multiplexing (WDM), polarization division multiplexing (PDM) and space division multiplexing (SDM) is proposed, which can improveIn order to meet the requirements of uploading and downloading large-capacity data in all-optical networks, a reconfigurable optical add-drop multiplexer (ROADM) based on wavelength division multiplexing (WDM), polarization division multiplexing (PDM) and space division multiplexing (SDM) is proposed, which can improve the uploading and downloading capacity of optical add-drop multiplexer (OADM) by 12 times. The OADM system based on WDM and PDM is built experimentally and performances are analyzed. Results show that the OADM based on WDM and PDM can achieve dense WDM and realize PDM steadily. The stability of the polarization state at main output port achieves 0.01, the splitting ratio of fast and slow axes at polarization beam splitter output port is close to 1∶1, and the insertion loss is lower than 9 dBm. The OADM models based on photonic lantern (PL) and SDM are established, and the multimode multiplexing of six-mode and three-mode are realized respectively. Results show that the effective refractive index difference between different modes of OADM based on PL and SDM is larger than 6×10-4, which indicates low inter mode interference and high isolation degree..
Laser & Optoelectronics Progress
- Publication Date: Jan. 01, 1900
- Vol. 54, Issue 10, 100601 (2017)
High Sensitivity Torsion Sensors Based on Few-Mode Long-Period Fiber Gratings
Deng Jing, Feng Yuanhua, Gao Shecheng, and Li zhaohui
A torsion sensor based on few-mode long-period fiber grating (LPG) with high sensitivity is proposed. The LPG is written by CO2-laser pulse with high frequency. Harmonic peaks are generated by the coupling between linear polarization (LP01 and LP11) modes of two cores. Torsion sensitivity can reach up to 0.528 nm·A torsion sensor based on few-mode long-period fiber grating (LPG) with high sensitivity is proposed. The LPG is written by CO2-laser pulse with high frequency. Harmonic peaks are generated by the coupling between linear polarization (LP01 and LP11) modes of two cores. Torsion sensitivity can reach up to 0.528 nm·rad-1·m-1, and the torsion sensitivity of the torsion sensor is one order higher than that of the common single-mode LPG. The torsion-induced LPG can be treated as a periodic helical modulation superimposed on the original grating. As a result, the effective grating period changes in proportion to the torsion rate to make the wavelength of resonant peak drift, which is the main reason for the generation of high torsion sensitivity. Due to the weak cross sensitivity of the new LPG to ambient refractive index and temperature, the new LPG can be used as a contact torsion sensor with high accuracy and has a wide range of application prospects in the fields relation to torsional measurement..
Laser & Optoelectronics Progress
- Publication Date: Jan. 01, 1900
- Vol. 54, Issue 10, 100602 (2017)
Multichannel Transmission System Based on All-Optical Wavelength Conversion for Dual Single Sideband Discrete Multitone Signal
Lu Jia, Chang Haiyue, Wang Yang, Zeng Xiangye, and Huang Xindi
The multichannel transmission of dual single sideband discrete multitone (Twin-SSB-DMT) signal based on all-optical wavelength conversion (AOWC) is investigated theoretically and simulated. The generation principle of the dual single sideband signal is studied theoretically, and the relationship between the converted sThe multichannel transmission of dual single sideband discrete multitone (Twin-SSB-DMT) signal based on all-optical wavelength conversion (AOWC) is investigated theoretically and simulated. The generation principle of the dual single sideband signal is studied theoretically, and the relationship between the converted signal and the original signal is analyzed. The dual single sideband signal, which is with the left single sideband modulated by discrete multitone-quadrature amplitude modulation (DMT-4QAM) and the right single sideband modulated by DMT-16QAM, is obtained when we set the radio-frequency signal in the push-pull modulator. High-quality converted signals of 1-8 channels are generated through the four-wave mixing of 20 Gbit·s-1 dual single-sideband signal in the semiconductor optical amplifier. The converted signal contains the original data, and the multicast transmission of high-order signal can be achieved. The simulation results show that the dual single sideband DMT signal improves the spectral efficiency and the utilization of wavelength bandwidth, reduces the cost, and improves the performance of the whole AOWC system. In addition, according to the constellation and bit error rate curves, 8-channel polarization-insensitive multicasting signals can be directly received without crosstalk, and the cost of signal to noise ratio is low, which is good for achieving the high-quality multicast system..
Laser & Optoelectronics Progress
- Publication Date: Jan. 01, 1900
- Vol. 54, Issue 10, 100603 (2017)
Wavelet Transform Based Peak Localization of Overlapped Fiber Bragg Grating Signal
Li Zhibin, Huang Qitao, Liu Chang, and Xiong Jie
Peak localization is a critical step in processing fiber Bragg grating (FBG) reflected signal. Aiming at the feature of FBG reflected signal, we propose a peak detecting algorithm applied to FBG reflected signal to solve the peak overlapping problem in peak localization. According to the ridge peak detecting algorithm Peak localization is a critical step in processing fiber Bragg grating (FBG) reflected signal. Aiming at the feature of FBG reflected signal, we propose a peak detecting algorithm applied to FBG reflected signal to solve the peak overlapping problem in peak localization. According to the ridge peak detecting algorithm based on continuous wavelet transform, the correspondence between wavelet coefficients and FBG reflected signals is analyzed, and the ridge peak detecting algorithm is improved to find the peak of overlapped FBG reflected signal. The experimental result shows that the improved wavelet ridge peak detecting algorithm can effectively solve the peak overlapping problem of FBG reflected signal. Through this algorithm, the error of peak detecting can be reduced, and the accuracy of peak localization can be improved..
Laser & Optoelectronics Progress
- Publication Date: Jan. 01, 1900
- Vol. 54, Issue 10, 100604 (2017)
Mixing Efficiency in Coherent Detection System
Tan Zhenkun, and Ke Xizheng
The coherent detection sensitivity can be directly reflected by mixing efficiency in free-space coherent optical communication system. Expressions of the variation in mixing efficiency with the radial error of optical axis, mismatching angle, axial defocusing and atmospheric turbulence intensity are derived respectivelThe coherent detection sensitivity can be directly reflected by mixing efficiency in free-space coherent optical communication system. Expressions of the variation in mixing efficiency with the radial error of optical axis, mismatching angle, axial defocusing and atmospheric turbulence intensity are derived respectively, and simulation analysis is carried out. Results show that mixing efficiency can reach the maximum value of 0.8145 when we choose the waist radius and relative aperture matched with wavelength. The optical axis radial error of signal light and local oscillator light has the greatest influence on the mixing efficiency and relative aperture, followed by the mismatching angle and axial defocusing. The above three factors are limited to 0-4 μm, 0-0.05 rad and 0-200 μm respectively. Mixing efficiency is larger than 0.55 when the 1550 nm light wave is chosen as the communication wavelength, the waist radius is 3.4λ and relative aperture is 0.21. The atmospheric turbulence effect can be effectively suppressed with a small aperture receiving antenna under the mid-strong turbulent condition..
Laser & Optoelectronics Progress
- Publication Date: Jan. 01, 1900
- Vol. 54, Issue 10, 100605 (2017)
Suppression of Kerr-Effect-Induced Bias for Resonator Fiber Optic Gyroscope
Lei Xing, Hu Qiang, Li Jun, and Wang Ke
Kerr effect is one of the key factors limiting the performance of the resonator fiber optic gyroscope (RFOG). Based on the Kerr effect and Sagnac effect, we establish a theoretical model of gyroscope Kerr effect bias error of RFOG, and analyze the influence of difference of coupling ratio of the output couplers in clocKerr effect is one of the key factors limiting the performance of the resonator fiber optic gyroscope (RFOG). Based on the Kerr effect and Sagnac effect, we establish a theoretical model of gyroscope Kerr effect bias error of RFOG, and analyze the influence of difference of coupling ratio of the output couplers in clockwise and counter-clockwise beam paths in fiber resonator and the difference of lengths of two resonant cavity arms on the performance of the gyroscope. In addition, we also present a scheme to suppress the Kerr effect bias error by coupling light intensity control and structure design of the RFOG. After 4 runs of individual experiments, it is shown that the proposed scheme can effectively suppress the Kerr effect. The gyroscope bias is reduced from 0.150 (°)/s to 0.017 (°)/s, and the bias stability is increased from 1300 (°)/h to 140 (°)/h. The gyroscope performance can be improved by nearly one order of magnitude..
Laser & Optoelectronics Progress
- Publication Date: Jan. 01, 1900
- Vol. 54, Issue 10, 100606 (2017)
Effects of Structural Parameters on Mode Field Distribution of Photonic Crystal Fiber
Xie Lianghua, Xu Dangpeng, Li Mingzhong, Zhang Xiaomin, Sun Xibo, Tian Xiaocheng, Zhang Rui, Zong Zhaoyu, Fan Mengqiu, Zhou Dandan, Zhu Na, Li Hongxun, and Xiang Xiangjun
Effects of structural parameters of photonic crystal fiber (PCF) on its eigenmode field distribution are analyzed with the full vector finite element method (FEM). The numerical calculation results show that light field will be confined in fiber core when the PCF structure is with multi-layer air hole and fiber core, lEffects of structural parameters of photonic crystal fiber (PCF) on its eigenmode field distribution are analyzed with the full vector finite element method (FEM). The numerical calculation results show that light field will be confined in fiber core when the PCF structure is with multi-layer air hole and fiber core, long distance between air holes and large filling ratio of air. High order mode appears when the number of fiber core layers, distance between air holes and filling ratio of air increase. In addition, the increasing of the number of fiber core layers and distance between air holes compensates the power leaking at fiber core arising from the decreasing of filling ratio of air. It is demonstrated that the single-mode transmission with large mode field is feasible when we decrease filling ratio of air and increase the number of fiber core layers and distance between air holes. The core radius and effective mode area can reach 40 μm and 3717 μm2 respectively while the power concentration of fiber core is 68.32% with four-layer air hole, two-layer fiber core, air filling ratio of 0.01 and distance between air holes of 20 μm..
Laser & Optoelectronics Progress
- Publication Date: Jan. 01, 1900
- Vol. 54, Issue 10, 100607 (2017)
Low-Loss Coupling Between Tapered Fibers and Anti-Resonant Hollow-Core Photonic Crystal Fibers
Zhang Naiqian, Qin Tianling, Wang Zefeng, Liu Wenbo, Cao Jianqiu, and Chen Zilun
Anti-resonant hollow-core photonic crystal fibers (HC-PCF) have important application in middle-infrared fiber gas lasers. The low-loss coupling between HC-PCF and solid-core fiber is a key technology to realize all-fiber structure fiber gas lasers. A scheme of inserting tapered solid-core fibers into hollow-core fiberAnti-resonant hollow-core photonic crystal fibers (HC-PCF) have important application in middle-infrared fiber gas lasers. The low-loss coupling between HC-PCF and solid-core fiber is a key technology to realize all-fiber structure fiber gas lasers. A scheme of inserting tapered solid-core fibers into hollow-core fibers is proposed and studied. Theoretical and experimental results show that the low-loss coupling between solid-core fiber and anti-resonant HC-PCF with large mode field diameter is realized when we use optical fiber taping technology to change the diameter of ordinary fiber mode field and make the mode field diameter of the tapered fiber approximately match that of the hollow-core fiber. For the ice-cream type anti-resonant HC-PCF with mode field diameter of about 35 μm, the simulation results indicate that when the waist diameters of tapered fibers are around 30-50 μm, the coupling efficiency is over 95% and the maximum coupling efficiency can reach to 98%. In the experiment, the coupling efficiency is 96.05% when the waist diameter of tapered fibers is 35 μm. This conclusion provides a feasible technical approach for the low-loss coupling between anti-resonant HC-PCF with large mode field diameter and solid-core-fiber and the realization of all-fiber structure gas lasers..
Laser & Optoelectronics Progress
- Publication Date: Jan. 01, 1900
- Vol. 54, Issue 10, 100608 (2017)
Insertion Loss Characteristics of Acousto-Optic Frequency Shifter in Optical Phase-Locked Loop and Its Optimization
Qu Zheng, Zhang Lei, Tong Shoufeng, Chang Shuai, Liu Yang, and Dong Yi
In order to apply the acousto-optic frequency shifter (AOFS) to the optical phase-locked loop for the fast and accurate tuning and to ensure the quality of the signal received by coherent receiver, we introduce the frequency shift principle and the dynamic operation mode of the AOFS in the phase-locked loop, study the In order to apply the acousto-optic frequency shifter (AOFS) to the optical phase-locked loop for the fast and accurate tuning and to ensure the quality of the signal received by coherent receiver, we introduce the frequency shift principle and the dynamic operation mode of the AOFS in the phase-locked loop, study the insertion loss characteristics of the AOFS systematically, and analyze the effects of power variation of driver and frequency variation in frequency shift process on insertion loss. We design and build a test system for the insertion loss measurement of 1550 nm AOFS based on the beat frequency method. The test results show the variation in the insertion loss under the influence of various modulation signals, and the global dynamic variation trend of insertion loss under multiple influencing factors is also analyzed and verified experimentally. The driving power is optimized according to the experimental results of the AOFS. The optimization results show that the AOFS insertion loss declines by 15 dB in the range of frequency shift when the driving power increases from 25 mW to 1 W, and the maximum relative insertion loss declines by 1 dB..
Laser & Optoelectronics Progress
- Publication Date: Jan. 01, 1900
- Vol. 54, Issue 10, 100609 (2017)
Analysis and Simulation of Detection Performance of Avalanche Photodiode
Fan Xinkun, Zhang Lei, Song Yansong, and Jiang Lun
In order to reasonably set the bias voltage of an avalanche photodiode (APD) detector and thus to achieve the adjustable multiplier factor at a constant temperature, we analyse the working principle of the APD detector and factors of influencing its detection sensitivity, and measure the detection sensitivity of the APIn order to reasonably set the bias voltage of an avalanche photodiode (APD) detector and thus to achieve the adjustable multiplier factor at a constant temperature, we analyse the working principle of the APD detector and factors of influencing its detection sensitivity, and measure the detection sensitivity of the APD detector in laboratory. The experimental results show that the APD detection sensitivity ranges from -47 dBm to -34 dBm when the communication rate changes from 10 Mb·s-1 to 2000 Mb·s-1. When the bias voltage changes from 55.0 V to 70.0 V, the detection sensitivities at communication rates of 10,100,1000 Mb·s-1 increase by 5.7,6.5,7.8 dB, respectively. The experimental results well validate the theoretical analysis, which provides technical support for improving the receptivity of space laser communication system..
Laser & Optoelectronics Progress
- Publication Date: Jan. 01, 1900
- Vol. 54, Issue 10, 100610 (2017)
Geometric Optics
Design and Implementation of Backlight Module of High Dynamic Range Video Display System Based on Geometrical Optics
Zhang Tao, Qiu Liang, Wu Hongying, and Lei Zhichun
The backlight module of high dynamic range video display system based on the geometrical optics is designed and accomplished. First, the important influence of luminance uniformity of backlight module on the high dynamic range video display system is determined. And the design parameters, such as the spacing and the liThe backlight module of high dynamic range video display system based on the geometrical optics is designed and accomplished. First, the important influence of luminance uniformity of backlight module on the high dynamic range video display system is determined. And the design parameters, such as the spacing and the light mixing distance of LED light sources of backlight module, are determined by Sparrow′s criterion. Then, the AutoCAD software is used to conduct 3D modeling. TracePro and LightTools are taken in the simulation experiment. The high dynamic range video display system is built by modifying the backlight module of the existing display screen. The results show that the designed and accomplished backlight module in this paper can meet the requirements of high dynamic range video display system. Peak brightness of liquid crystal display panel can reach 2500 cd·m-2 and uniformity of luminance is up to 95.85%..
Laser & Optoelectronics Progress
- Publication Date: Jan. 01, 1900
- Vol. 54, Issue 10, 100801 (2017)
Image Processing
Spatial-Spectral Feature Extraction of Hyperspectral Image Based on Deep Learning
Huang Hong, He Kai, Zheng Xinlei, and Shi Guangyao
On the basis of the characteristics of multi-band, nonlinear and spatial correlation of hyperspectral remote sensing data, a new feature extraction algorithm based on spatial-spectral deep learning (SSDL) is proposed. This algorithm uses a multiple layers deep learning model, which is the stacked automatic encoder to sOn the basis of the characteristics of multi-band, nonlinear and spatial correlation of hyperspectral remote sensing data, a new feature extraction algorithm based on spatial-spectral deep learning (SSDL) is proposed. This algorithm uses a multiple layers deep learning model, which is the stacked automatic encoder to study high spectral data layer by layer and explore the deep nonlinear characteristics of the image. Based on the spatial neighbor information of each feature pixel, the spatial-spectral combination of sample depth feature and spatial information is used to increase the compactness of homogeneous data and the separability of non-homogeneous data, and improve the performance of subsequent classification. The ground objects classification experiments are performed on Pavia University and Salinas Valley hyperspectral remote sensing datasets. When sample proportion is 1%, the ground objects overall classification accuracy reaches 91.05% and 94.16%. When sample proportion is 5%, the ground objects overall classification accuracy reaches 97.38% and 97.50%. The results show that the SSDL feature extraction algorithm fuses the deep nonlinear characteristics and spatial information of data. It can effectively extract the discriminant features, and obtain higher classification accuracy than other algorithms..
Laser & Optoelectronics Progress
- Publication Date: Jan. 01, 1900
- Vol. 54, Issue 10, 101001 (2017)
A Robust Compact Image Hash Algorithm Zhang Zhifeng, Pei Zhili
[in Chinese], and [in Chinese]
In order to overcome such defects as low robustness and low detection rate induced by the sensitivity of current hash image authentication algorithm to the rotation operation, the compact image hash algorithm based on an improved local binary pattern (LBP) operator and the dynamic update transform is proposed. The lineIn order to overcome such defects as low robustness and low detection rate induced by the sensitivity of current hash image authentication algorithm to the rotation operation, the compact image hash algorithm based on an improved local binary pattern (LBP) operator and the dynamic update transform is proposed. The linear interpolation technique is introduced to preprocess the input image and improve the scaling robustness of the hash sequence. The Ring division is used to transform the interpolation image into the secondary image. A H-LBP operator with strong descriptive ability was designed when the Heaviside function is embedded into traditional LBP operator. Considering the difference between the center pixel characteristics and the adjacent pixels, the anti-rotation robustness features are extracted. The compression sensing is introduced to reduce the dimensions of high-dimensional feature vector, and a compact transition hash array is output. A dynamic update transform mechanism is designed with the chaotic transform idea to encrypt the transition hash array, and the image hash sequence is obtained. Finally, the hash similarity between the input image and the detected image is calculated based on Hamming distance to achieve the authenticity of the image through the optimized decision threshold. The experimental results show that the proposed algorithm generates a smaller hash sequence and has better perceptual robustness to rotation, noise and other operations than the current hash algorithms..
Laser & Optoelectronics Progress
- Publication Date: Jan. 01, 1900
- Vol. 54, Issue 10, 101002 (2017)
Image Quality Assessment Based on Symmetry Phase Congruency
Zhang Fan, Zhang Ruoya, and Li Zhenzhen
The image quality assessment algorithm based on feature similarity (FSIM) has certain limitations to some extent when detecting image step edges. A new algorithm named symmetry feature similarity is put forward by combining the FSIM with the symmetry phase congruency (SPC), which is sensitive to step edges, and calculaThe image quality assessment algorithm based on feature similarity (FSIM) has certain limitations to some extent when detecting image step edges. A new algorithm named symmetry feature similarity is put forward by combining the FSIM with the symmetry phase congruency (SPC), which is sensitive to step edges, and calculating the gradient magnitude through the isotropic Sobel operator. The proposed algorithm makes use of the symbols responded to the phase adjacent pixels by SPC and the more accurate weighting coefficient of isotropic Sobel operator to detect and locate the image edge feature. The simulation experiments on various kinds of distorted images are carried out, and the results indicate that the SFSIM is more sensitive to sharper image edge features and Gaussian blurred images, on the basis of retaining the excellent performance of the original method..
Laser & Optoelectronics Progress
- Publication Date: Jan. 01, 1900
- Vol. 54, Issue 10, 101003 (2017)
Image Edge Detection and Shape Reconstruction in Corneal Topography
Xu Danyang, Gao Jianxun, Sui Chenghua1, and Zhou Minghua
In order to achieve the application of corneal topography instrument in clinical examination, the traditional Klyce three-dimensional reconstruction of the surface model is changed into the ray tracing method. 24 rings and 256 sub-pixel data per ring are obtained. The original assumed ellipsoid is estimated by the leasIn order to achieve the application of corneal topography instrument in clinical examination, the traditional Klyce three-dimensional reconstruction of the surface model is changed into the ray tracing method. 24 rings and 256 sub-pixel data per ring are obtained. The original assumed ellipsoid is estimated by the least squares method. The ellipsoid is corrected to obtain the most realistic corneal surface. First of all, the pixel level data information is obtained by the Canny algorithm. Then, the gray value of the data is smoothed to reduce the noise. And the gray gradient of the data is fitted 3 times to obtain the sub-pixel data. Finally, the clear images obtained by standard corneal topography are used for the three-dimensional reconstruction. By analyzing the curvature radii and diopter data obtained by both methods, the results show that the errors are less than 0.9%, and it proves that the proposed method is feasible..
Laser & Optoelectronics Progress
- Publication Date: Jan. 01, 1900
- Vol. 54, Issue 10, 101004 (2017)
An Adaptive Region Fusion Rule Multi-Focus Image Fusion Algorithm
Cheng Deqiang, Chen Gang, Gao Lingzhi, Li Hang, Huang Xiaoli, and Man Guangyi
Aiming at the problem that the discrete wavelet transform multi-focus image fusion algorithm ignores the low frequency component in fusion processing and leads to edge distortion and image blur. An adaptive region fusion rule of multi-focus image fusion algorithm is proposed. First of all, the source image is decomposeAiming at the problem that the discrete wavelet transform multi-focus image fusion algorithm ignores the low frequency component in fusion processing and leads to edge distortion and image blur. An adaptive region fusion rule of multi-focus image fusion algorithm is proposed. First of all, the source image is decomposed by wavelet, and the low frequency and high frequency coefficients are obtained. Then the threshold processing of low frequency coefficients of the approximate information are carried out with the improved spatial frequency. Then, the improved gradient and the sum-modified-Laplacian high frequency fusion rule are utilized on the representative information. Finally, the processed high frequency and low frequency coefficients are reconstructed by wavelet transform. Experimental results show that the proposed algorithm can preserve the image contour information and edge information subjectively, and the fusion result is better than the traditional fusion methods. The objective indicators are greatly improved objectively..
Laser & Optoelectronics Progress
- Publication Date: Jan. 01, 1900
- Vol. 54, Issue 10, 101005 (2017)
Imaging Systems
Active Control Experiment of the Segmented Primary Mirror
Yu Wenhao, Li Bin, Chen Mo, and Xian Hao
It is difficult to realize the active control of block segmented primary mirror for splicing technique. The model is established based on the active control system of segmented primary mirror. The single-input single-output systems are obtained after the diagonalization of transfer function matrix of a multi-input multIt is difficult to realize the active control of block segmented primary mirror for splicing technique. The model is established based on the active control system of segmented primary mirror. The single-input single-output systems are obtained after the diagonalization of transfer function matrix of a multi-input multi-output system using the static decoupling. And the simplified control system model is designed. On this basis, the controller design of the control system is completed. We set up an experimental system of segmented mirror in the laboratory with four hexagonal mirrors to implement the active control technology. Three actuators control the tip and tilt error of each sub-mirror. The results show that the correction time of unit tilt error is 2.6 s. According to the power spectral density analysis of the tip of sub-mirror, the correction bandwidth of dynamic tilt error reaches 0.34 Hz. The efficient fast correction of static splicing error and the real-time effective correction of dynamic error are realized..
Laser & Optoelectronics Progress
- Publication Date: Jan. 01, 1900
- Vol. 54, Issue 10, 101101 (2017)
Projective Decomposition Algorithms for X-Ray Dual-Energy Bone Densitometer Based on Photon Counting Detectors
Mo Jingqing, Xu Pin, and Sun Mingshan
Four dual-energy projective decomposition algorithms that may be applied to the X-ray bone densitometry, including surface fitting method, lookup table method, contour fitting method, and neural network method, are studied and compared. The photon counting detector has high energy resolution and low noise. The projectiFour dual-energy projective decomposition algorithms that may be applied to the X-ray bone densitometry, including surface fitting method, lookup table method, contour fitting method, and neural network method, are studied and compared. The photon counting detector has high energy resolution and low noise. The projection data acquired by the multi energy bin photon counting detector on a bench-top imaging setup helps to improve the decomposition precision. Aluminum (Al) and polymethyl methacrylate (PMMA) are selected as the base materials to represent bone and soft tissue respectively. Combinations with different base material thicknesses are used for calibration experiments to build lookup tables for high energy and low energy projections. The four projective decomposition algorithms mentioned above are used to establish the inverse lookup table, nine test points are selected in table and are decomposed by the four decomposition algorithms, and the decomposition deviation and running time of various algorithms are calculated and compared. The results show that Al thicknesses with a bias of 0.11%-3.68%, 0-2.86%, 0.07%-3.23% and 0.41%-4.18%, PMMA thicknesses with a bias of 0.11%-3.42%, 0.44%-5.33%, 0.02%-2.83% and 0.09%-4.89% are estimated by the surface fitting method, the lookup table method, the contour fitting method and the neural networks method, respectively. Compared to the lookup table method and the neural network method, the surface fitting method and the contour fitting method are faster by about an order of magnitude. The results suggest that the contour fitting method is superior in terms of decomposition accuracy and rate..
Laser & Optoelectronics Progress
- Publication Date: Jan. 01, 1900
- Vol. 54, Issue 10, 101102 (2017)
Visible Light Image Enhancement Based on Experimental Cabin Under Atmospheric Environment
Yang Jianqing, Luo Jijun, Xu Jun, Sun Qiyun, and Wang Ting
Visible light imaging of target scene under the condition of rain and fog plays an important part in the simulation of battlefield environment. It is of great significance to enhance visible image to improve the range and precision of the optical guided missile. In an experimental cabin under atmospheric environment, tVisible light imaging of target scene under the condition of rain and fog plays an important part in the simulation of battlefield environment. It is of great significance to enhance visible image to improve the range and precision of the optical guided missile. In an experimental cabin under atmospheric environment, the simulation of target mechanical structure named miniature landscape sand table is carried out under various rain and fog conditions to obtain visible images in sunny day, mist, fog, dense fog, light rain, moderate rain and heavy rain. The visible images are enhanced based on the improved dark channel method, and, the mean squared error (MSE) and peak signal to noise ratio (PNSR) of the rain and fog images and the enhanced images are calculated. The calculated results show that , with the increase of rain and fog level, MSEs of the rain and fog images and enhanced images gradually increas from 245.78 to 383.07, and from 46.84 to 222.01, respectively, and the PNSRs gradually decrease from 24.23 to 22.29, and from 31.42 to 24.66, respectively. The quality of the images decreases with the increase of rain and fog level, even after the images are enhanced. In addition, compared MSE and PNSR of the rain and fog images with those of the enhanced images, it shows that MSE decreases obviously and PNSR increases significantly. The quality of the images is improved significantly according to the two objective indexes of MSE and PNSR..
Laser & Optoelectronics Progress
- Publication Date: Jan. 01, 1900
- Vol. 54, Issue 10, 101103 (2017)
Instrumentation, Measurement and Metrology
Photothermal Radiometry Testing on Subsurface of Metal Materials
Wang Xinjue, Liu Hengbiao, and Hu Wenxiang
To investigate the ability of photothermal radiometry (PTR) testing on the subsurface of metal materials, the amplitude and phase of thermal wave generated from a double layer material which is excited by intensity modulated laser are analyzed theoretically. Besides, the PTR signals of stepped steel samples, aluminum/sTo investigate the ability of photothermal radiometry (PTR) testing on the subsurface of metal materials, the amplitude and phase of thermal wave generated from a double layer material which is excited by intensity modulated laser are analyzed theoretically. Besides, the PTR signals of stepped steel samples, aluminum/steel samples with blind hole array, and steel samples with blind hole filled tin are tested in experiments. For the aluminum samples with blind hole array with diameters of 2.5, 2.0, 1.5 mm and hole bottom thickness of 0.2, 0.4, 0.6 mm, the PTR phase distributions obtained by the experiment show that the diameter of the blind hole and the hole bottom thickness are distinguishable. For the steel samples with blind hole array, the PTR phase distribution before and after the blind hole filling with tin shows a certain difference. The experimental results show that the PTR detection of the focused spot can detect the stoma defect in aluminum or steel. The depth of the stoma defect should be less than or approximately equal to the thermal diffusion length of the surface material, and the cross-sectional area of the stoma defect should be approximately equal to or greater than the spot..
Laser & Optoelectronics Progress
- Publication Date: Jan. 01, 1900
- Vol. 54, Issue 10, 101201 (2017)
Study and Design of Ultraviolet Energy Meter with Low Power Consumption
Wang Jun, Han Li, Du Bojun, Yang Huiling, and He Xin
In order to solve the problems of large power consumption, high cost, low precision and complicated design in the traditional ultraviolet energy meter, a micro-power ultraviolet energy detection scheme based on current-integration with dual-compensation mechanism is proposed. The micro-power microcontroller is used to In order to solve the problems of large power consumption, high cost, low precision and complicated design in the traditional ultraviolet energy meter, a micro-power ultraviolet energy detection scheme based on current-integration with dual-compensation mechanism is proposed. The micro-power microcontroller is used to calculate the ultraviolet energy. The output current of the ultraviolet detector is converted into square wave pulse by the current integration module. The discharge compensation circuit and ambient light compensation circuit are adopted to correct the deviation of the current integration module and improve the detection accuracy. The main controller counts the number of pulses and calculates the energy. The system makes full use of low-power mode to optimize the display program, and the display program is driven by the main controller without driver chip, which further reduces the display power consumption. Experimental results show that the power consumption of this program is less than 165 μW, and the deviation of the ultraviolet energy value is less than 1%. The system with low circuit complexity and low cost of chip has the advantages of strong durability and high practical value..
Laser & Optoelectronics Progress
- Publication Date: Jan. 01, 1900
- Vol. 54, Issue 10, 101202 (2017)
Nonlinear Error Calibration Method for Capacitive Displacement Sensor Based on Laser Interferometry
Wang Dapeng, Jin Xing, Zhou Weijing, and Li Nanlei
In order to solve the problem of frequent calibration of nonlinear error for capacitive displacement sensors in micro-thrust measurement, an in-situ calibration method based on laser interferometry is studied. The calibration principle is that the optical path difference and capacitive displacement sensor plate spacingIn order to solve the problem of frequent calibration of nonlinear error for capacitive displacement sensors in micro-thrust measurement, an in-situ calibration method based on laser interferometry is studied. The calibration principle is that the optical path difference and capacitive displacement sensor plate spacing are changed simultaneously by adjustment and measurement of the positions of movable corner prism and object through the linear displacement, and the nonlinear error of sensor is calibrated by the linear fitting method based on the measuring results of laser interference. The interferometric optical path based on common optical elements is built and sensors with different measuring ranges are calibrated in micro-thrust measurement. Based on the analysis of characteristics of the interference intensity, the calculation method of interference fringe number is determined. The measuring accuracy of interference light path displacement is 66.5 nm. The practicability and accuracy of the calibration device are verified by experiment. Finally, the results of calibration, the nonlinear sensor output relative error and the main factors affecting the laser interference measurement accuracy are analyzed. The total error is 67.2 nm..
Laser & Optoelectronics Progress
- Publication Date: Jan. 01, 1900
- Vol. 54, Issue 10, 101203 (2017)
Lasers and Laser Optics
Surface Wettability of Laser-Induced Al2O3 Ceramic Tools
Yang Qibiao, Xiao Chenguang, Chen Zhongpei, Chen Lie, Lou Deyuan, Tao Qing, Zhen Zhong, Zhai Zhongsheng, Liu Dun, and Bennett Peter
The effects of pulse energy and spot overlap ratio on the wettability of ceramic tools processed by femtosecond lasers are investigated. The wettability of the alumina ceramic tools after laser treatment is investigated by measuring the contact angles. The experimental results show that the femtosecond laser can changeThe effects of pulse energy and spot overlap ratio on the wettability of ceramic tools processed by femtosecond lasers are investigated. The wettability of the alumina ceramic tools after laser treatment is investigated by measuring the contact angles. The experimental results show that the femtosecond laser can change the wettability of ceramic material surfaces. The superhydrophilic surfaces and the superhydrophilic-based cutting fluid surfaces can be prepared if suitable laser energy density and spot overlap ratio are chosen. The wetting speed of water based cutting fluid on the laser-processed surfaces is exponentially decaying with the contact angle..
Laser & Optoelectronics Progress
- Publication Date: Jan. 01, 1900
- Vol. 54, Issue 10, 101401 (2017)
Electrode Optimization of Oxide Aperture Confined Vertical-Cavity Surface-Emitting Lasers
Wu Xiangyu, and Cui Bifeng
There are many ways to limit the current flowing in the vertical-cavity surface-emitting laser (VCSEL), in which the preparation technology of oxide aperture (current injection aperture) confining method is simple. So the oxide aperture confining method becomes a universal choice. The simulation result shows that the mThere are many ways to limit the current flowing in the vertical-cavity surface-emitting laser (VCSEL), in which the preparation technology of oxide aperture (current injection aperture) confining method is simple. So the oxide aperture confining method becomes a universal choice. The simulation result shows that the maximum current density is at the edge of the oxide aperture for the oxide aperture confined VCSEL. The influence of the inner radius of the P-type electrode on the current density of the injection aperture is also simulated. The results show that when the inner radius of the P-type electrode increases, the current density at the edge of the device oxide aperture increases, the corresponding device working voltage increases, and the output optical power declines. The device surface spot area is calculated with optical field distribution and divergence angle distribution of the device structure comprehensively considered. The optimal inner radius of the P-type electrode is 8 μｍ..
Laser & Optoelectronics Progress
- Publication Date: Jan. 01, 1900
- Vol. 54, Issue 10, 101402 (2017)
Unstable Resonator Technique for Nd∶YAG Slab Gain Medium
Lei Jian, Liu Yang, Li Tianqi, Li Bao, Wang Zhe, and Tang Xiaojun
An unstable resonator can obtain high extraction efficiency of light as well as high beam quality under the condition of the large Fresnel number. We design a telescopic off-axis metastable-unstable hybrid resonator with conduction-cooled end-pumped structure which can be used as the Nd∶YAG slab gain medium, and its ouAn unstable resonator can obtain high extraction efficiency of light as well as high beam quality under the condition of the large Fresnel number. We design a telescopic off-axis metastable-unstable hybrid resonator with conduction-cooled end-pumped structure which can be used as the Nd∶YAG slab gain medium, and its output coupling mirror is a variable reflectivity mirror. The resonator in the width direction of the hybrid resonator (the x direction of the slab gain medium) is an unstable resonator, and the resonator in the thickness direction (the y direction of the slab gain medium) is a metastable resonator. Through the theoretical analysis, an output power of 4428.7 W of this metastable-unstable hybrid resonator structure and an optical-optical efficiency of 0.4429 can be obtained when the pump power is 10 kW..
Laser & Optoelectronics Progress
- Publication Date: Jan. 01, 1900
- Vol. 54, Issue 10, 101403 (2017)
Water-Assisted Laser Induced Plasma Backside Etching of Pyrex7740 Glass
Sun Shufeng, and Shao Yong
A method of water-assisted laser induced plasma backside etching of Pyrex7740 glass is proposed and a scaled-down cross-channel microfluidic chip is fabricated. The influences of laser energy density and laser processing times on the average etching depth, and the function of deionized water in the etching process are A method of water-assisted laser induced plasma backside etching of Pyrex7740 glass is proposed and a scaled-down cross-channel microfluidic chip is fabricated. The influences of laser energy density and laser processing times on the average etching depth, and the function of deionized water in the etching process are studied by means of theoretical analyses and processing experiments. The study results show that the average etching depth depends much on the laser energy density and the processing times. The deionized water is helpful for the realization of a continuous etching, and a chip with microgroove width of 77.8 μm, etching depth of 20.4 μm, a neat etching edge of no obvious damages is fabricated. However, in the absence of deionized water, the maximum etching depth is 2.8 μm under a laser energy density of 3.4 J/cm2..
Laser & Optoelectronics Progress
- Publication Date: Jan. 01, 1900
- Vol. 54, Issue 10, 101404 (2017)
Correlation of Temporal Profile and Spectrum for Small Broadband Frequency Modulation Pulse in High Power Laser Facility
Li Lei, Zhang Bo, Xia Yanwen, Peng Zhitao, Dong Jun, and Sun Zhihong
In allusion to the frequency modulation to amplitude modulation (FM-to-AM) effect in the transmission process of small broadband frequency modulation pulse, variation of pulse waveform and characteristics caused by loss of different orders in the spectrum is studied, combining theoretical simulation with experimental vIn allusion to the frequency modulation to amplitude modulation (FM-to-AM) effect in the transmission process of small broadband frequency modulation pulse, variation of pulse waveform and characteristics caused by loss of different orders in the spectrum is studied, combining theoretical simulation with experimental validation. The results show that the waveform modulation increases linearly with the loss of spectral component, and the outline of waveform modulation is associated with the positions of the missing spectral components in the spectrum. The results provide the basis of precompensation and inhibition of FM-to-AM effect, and make a certain significance for safe operation of laser facility and improvement of physical experiment results..
Laser & Optoelectronics Progress
- Publication Date: Jan. 01, 1900
- Vol. 54, Issue 10, 101405 (2017)
Laser Shock Forming of 2024-T351 Aluminum Alloy Sheets Supported by Rubber
Li Min, Ji Kankan, Liu Tao, Duan Shiwei, Tong Jinyu, Chen Bin, and Zhang Xingquan
Based on the finite element analysis software of ABAQUS, the laser shock forming process of 2024-T351 aluminum alloy sheets under the support of a polyurethane rubber is studied. The effects of thickness, diameter and hardness of rubber on the metal sheet forming is also analyzed. An experiment is carried out to verifyBased on the finite element analysis software of ABAQUS, the laser shock forming process of 2024-T351 aluminum alloy sheets under the support of a polyurethane rubber is studied. The effects of thickness, diameter and hardness of rubber on the metal sheet forming is also analyzed. An experiment is carried out to verify the simulated results. The study results show that the final shape of the deformed sheet is hemispherical. A great thickness of the rubber is conducive to the metal sheet forming when the thickness is in the range of 1.5-3 mm. The metal sheet forming result has no obvious correlation with the rubber diameter. A small hardness of the rubber is conducive to the metal sheet forming when the hardness is in the range of 40-70 HA. The simulated and experimental results have good consistency..
Laser & Optoelectronics Progress
- Publication Date: Jan. 01, 1900
- Vol. 54, Issue 10, 101406 (2017)
Testing and Analysis of Time Resolved Pulse Xenon Lamp Spectrum
Sun Zhengfei, Liang Hairong, Wang Li, Liu Jianjun, Zhou Shenlei, Li Haibing, and Zhu Jian
High power pulse xenon lamps are usually used as the pumping source for slab amplifiers in high power laser facilities. The spectrum of xenon lamps is strongly linked to the gain performance of slab amplifiers. A spectrum testing system in a dark room with the time resolution of 2 μs is built to test the xenon lamp speHigh power pulse xenon lamps are usually used as the pumping source for slab amplifiers in high power laser facilities. The spectrum of xenon lamps is strongly linked to the gain performance of slab amplifiers. A spectrum testing system in a dark room with the time resolution of 2 μs is built to test the xenon lamp spectra at different discharging time. The results show that the xenon lamp gives quite different spectra for rising and falling edges of the current waveform with the same current density. The rising edge spectrum has many obvious discrete spectra. If no pre-ionization is applied, the radiation spectrum energy at the rising edge is 48% lower than that at the falling edge when the current density is 0.866 kA·cm-2. If pre-ionization is applied, the difference reduces to 24%. The pre-ionization can effectively increase the radiated energy of the rising edge, and the pre-ionization is an effective way to increase the radiation efficiency of the xenon lamp. The original xenon lamp radiation spectrum model is modified to agree with the experimental spectral data well..
Laser & Optoelectronics Progress
- Publication Date: Jan. 01, 1900
- Vol. 54, Issue 10, 101407 (2017)
Superhydrophobic Surface of Aluminium Base Induced by Femtosecond Laser
Yang Qibiao, Deng Bo, Wang Yutao, Xiao Chenguang, Wang Xing, Chen Lie, Zheng Zhong, Lou Deyuan, Tao Qing, Zhai Zhongsheng, Bennett Peter, and Liu Dun
The surface contact angles of aluminum-based materials is regulated and controlled by using femtosecond laser pulses with different energies, and the transformation mechanism of wettability is analyzed and studied. The results show that the final stable wettability state of aluminum-based material surfaces after the feThe surface contact angles of aluminum-based materials is regulated and controlled by using femtosecond laser pulses with different energies, and the transformation mechanism of wettability is analyzed and studied. The results show that the final stable wettability state of aluminum-based material surfaces after the femtosecond laser processing and aging treatment is related to the laser energy and the aging time. With the increase of the laser energy, the surface contact angle is changed from 70° to above 150°. The morphology, roughness and chemical compositions of aluminum-based surfaces are studied under different pulse energy processing conditions. The results show that the wettability of a laser-processed sample changes from a hydrophilic state to a final super-hydrophobic state. The super-hydrophobic surfaces can be obtained in different pulse energy regions, but there are non-periodic or periodic structural differences in their surface microstructures, and the formation mechanisms of hydrophobic properties are different..
Laser & Optoelectronics Progress
- Publication Date: Jan. 01, 1900
- Vol. 54, Issue 10, 101408 (2017)
Directional Solidification Microstructure and Segregation of SRR99 Superalloys by Selective Laser Melting
Pan Aiqiong, Zhang Li, and Wang Zemin
The directional solidification experiment of SRR99 Ni-based superalloys is conducted by the selective laser melting (SLM) method, and the microstructure, the phase composition, the element segregation of samples are measured. The results show that a good metallurgical combination between the deposition layer and the asThe directional solidification experiment of SRR99 Ni-based superalloys is conducted by the selective laser melting (SLM) method, and the microstructure, the phase composition, the element segregation of samples are measured. The results show that a good metallurgical combination between the deposition layer and the as-cast substrate is formed, and the deposited samples are composed of the γ and γ′ phases. There is a strongest diffraction peak both in the deposition layer and the as-cast substrate when the diffraction angle is 50.78°, which indicates that the growth orientation of the substrate gets well extended in the SLM deposition structure. The primary dendrite spacing is only 1-2 μm and the secondary dendrite arm degenerates and even disappears. The segregation ratio of each alloy element is close to 1 and the elements are uniformly distributed at the dendrite arms and the interdendritic space..
Laser & Optoelectronics Progress
- Publication Date: Jan. 01, 1900
- Vol. 54, Issue 10, 101409 (2017)
Warp Deformation in Single-Track Laser Cladding Based on Temperature Characteristics
Gong Xinyong, Gao Shiyou, Xian Shiyu, and Yu Runxiang
The temperature field characteristic of single-layer single-track cladding with synchronous powder feeding is analyzed by using the verified finite element model and the ANSYS software. According to the heating-pulse zone demarcation points and the peak points of the temperature curve on the upper surface of base at anThe temperature field characteristic of single-layer single-track cladding with synchronous powder feeding is analyzed by using the verified finite element model and the ANSYS software. According to the heating-pulse zone demarcation points and the peak points of the temperature curve on the upper surface of base at any moment, the section body for the warp deformation analysis is obtained by using two geometric planes to intercept the single-track cladding model. By analyzing the stress/strain states of the upper surface of the cladding layer and the upper and lower surfaces of the base, it is found that the reverse and forward bending occur successively on the section body. The cladding part exhibits deformation toward the laser beam macroscopically. Finally, the reasons for the warp deformation in the single-track cladding process are summarized..
Laser & Optoelectronics Progress
- Publication Date: Jan. 01, 1900
- Vol. 54, Issue 10, 101410 (2017)
Simulation Analysis and Experimental Study of 316L Stainless Steel Weldments Processed by Laser Shock Peening
Lu Haifei, Lu Jinzhong, Zhang Wenquan, and Luo Kaiyu
A stress distribution model of "welding+laser shock peening (LSP)" is established by using the ABAQUS finite element analysis software, and the effect of LSP with different pulse energies on the stress distribution and strain in the welding zones of 316L stainless steels processed by the argon-arc welding is A stress distribution model of "welding+laser shock peening (LSP)" is established by using the ABAQUS finite element analysis software, and the effect of LSP with different pulse energies on the stress distribution and strain in the welding zones of 316L stainless steels processed by the argon-arc welding is studied. The study results show that the residual stress distribution simulated by this model is similar to the experimental result. LSP can induce a residual compressive stress layer in the welding zone to eliminate the residual tensile stress induced by the welding thermal influence. With the increase of laser pulse energy, the residual compressive stress and the depth of residual compressive stress layer increase, but the increase becomes smaller. The peak value of strain on the weldment surface increases with the increase of laser pulse energy..
Laser & Optoelectronics Progress
- Publication Date: Jan. 01, 1900
- Vol. 54, Issue 10, 101411 (2017)
Experimental Study on Laser Cladding of Ni-Based Alloys on Spheroidal Graphite Cast Iron Surface
Zhai Jianhua, Xu Huiyin, Liu Zhijie, Shen Cheng, and Wang Qianbao
Under different process parameters, the laser cladding of Ni-based alloys on the spheroidal graphite cast iron QT450-10 surface is conducted, the microstructure and the phase compositions of cladding layers are analyzed, and the tensile stress-strain curves of samples with and without laser cladding and the fracture moUnder different process parameters, the laser cladding of Ni-based alloys on the spheroidal graphite cast iron QT450-10 surface is conducted, the microstructure and the phase compositions of cladding layers are analyzed, and the tensile stress-strain curves of samples with and without laser cladding and the fracture morphologies of samples are studied. The results show that, when the laser power is 1.6 kW, the laser scanning speed is 400 mm·min-1 and the powder feeding speed is 3.2 r·min-1, better quality cladding layer can be achieved and a good metallurgical bonding is formed between the matrix and the cladding layer where no cracks and pores are observed. Under the temperature of 25 ℃ and when the cladding layer number is 1, the microhardness of cladding layers is 265 HV, about 1.5 times of that of the matrix. The fracture site of cladding samples is in the matrix. After the laser cladding of Ni-based alloys, the strength of the spheroidal graphite cast iron is enhanced..
Laser & Optoelectronics Progress
- Publication Date: Jan. 01, 1900
- Vol. 54, Issue 10, 101412 (2017)
Machine Vision
Solution of Duality in Pose Estimation of a Single Circle Using Rectangle Constrain
Chen Zhikun, Hu Lianjun, Wang Yi, and Wang Quan
In order to solve the false pose of a single circle feature in the monocular vision measurement, a method for eliminating the pose duality of a single circle based on rectangle constrain is proposed. When the camera is calibrated in advance, the images of the circle and rectangle of the target are acquired, and the plaIn order to solve the false pose of a single circle feature in the monocular vision measurement, a method for eliminating the pose duality of a single circle based on rectangle constrain is proposed. When the camera is calibrated in advance, the images of the circle and rectangle of the target are acquired, and the planes of circle and rectangle are required to be coplanar or parallel to each other. Firstly, the center position of the circle feature and the normal vector of the circle plane can be obtained by the mathematical derivation which has a false solution. Secondly, based on the constrain condition that the real normal vectors between the circle plane and the normal vector of the rectangle plane whose priory condition is unknown are parallel to each other, the false solution can be effectively eliminated. Finally, the real pose parameters of the object can be calculated by the related algorithm, so the real position of the object is acquired. The experimental results show that the absolute error of the object attitude measurement is less than 0.5°, which shows that the proposed method is simple and easy to implement and can eliminate the false pose effectively..
Laser & Optoelectronics Progress
- Publication Date: Jan. 01, 1900
- Vol. 54, Issue 10, 101501 (2017)
Object Tracking Based on Multi-Feature and Local Joint Sparse Representation
Li Jingxuan, and Zong Qun
Aimed at the problem of occlusion, deformation and illumination in the object tracking, an object tracking method based on multi-feature and local joint sparse representation is proposed within particle filter framework. The color model of the object is established by using HSV space. The texture apparent model of the Aimed at the problem of occlusion, deformation and illumination in the object tracking, an object tracking method based on multi-feature and local joint sparse representation is proposed within particle filter framework. The color model of the object is established by using HSV space. The texture apparent model of the object is established by using the enhanced center symmetric local binary patterns and represented by the local joint sparse coding. Integrating the color and texture features,the similarities of the object and candidate regions are computed. The object state is estimated by the maximum posterior probability. Whether the object model need to be updated is judged every two frames, which reduces the accumulative errors caused by frequent updates. The proposed method is compared with the other four methods by using visual tracker benchmark data set. Experimental results show that the overall accuracy and success rate of the proposed method is 83.5% and 79.6% respectively. In the case of occlusion, deformation and illumination, the proposed method can track the object accurately and steadily..
Laser & Optoelectronics Progress
- Publication Date: Jan. 01, 1900
- Vol. 54, Issue 10, 101502 (2017)
Materials
Effect of Phosphor Sedimentation on Photochromic Properties of Light Emitting Diodes
Zhuang Yunyi, Wang Yong, Li Zhanguo, Li Wenbo, Yang Lei, and Zou Jun
Aiming at the phenomenon of phosphor sedimentation during white light emitting diode (LED) package, the optical properties and the concentration ratios of color coordinates of a white LED after dispensing are studied under different standing time. The study results show that, when the standing time is between 0 and 30 Aiming at the phenomenon of phosphor sedimentation during white light emitting diode (LED) package, the optical properties and the concentration ratios of color coordinates of a white LED after dispensing are studied under different standing time. The study results show that, when the standing time is between 0 and 30 min, the color coordinate setting is concentrated whose center coordinates are in the range of 7 SDCM color tolerance; when the standing time is between 30 min and 40 min, the color coordinate setting is dispersive whose center coordinates are out of the range of color tolerance. The heat distribution of white LED lamps at the heat balance is simulated and the results show that the working temperature of light emitting diode lamps meets the requirements of industrial production..
Laser & Optoelectronics Progress
- Publication Date: Jan. 01, 1900
- Vol. 54, Issue 10, 101601 (2017)
Preparation and Properties of Eu2+, Dy3+ Co-Doped Alkaline Earth Silicate Fluorescent Powders
Wang Xiaoduan, Zhao Yajuan, Zhang Yong, Li Zhao, Chen Lijun, Chen Shuangli, and Xie Huidong
Eu2+ and Dy3+ co-doped alkaline earth silicate fluorescent powders are synthesized by the high temperature solid-phase method and the microwave combustion method. The properties of the fluorescent powders are analyzed and measured by scanning electron microscope, X-ray diffractometer and fluorescence analyser. The resuEu2+ and Dy3+ co-doped alkaline earth silicate fluorescent powders are synthesized by the high temperature solid-phase method and the microwave combustion method. The properties of the fluorescent powders are analyzed and measured by scanning electron microscope, X-ray diffractometer and fluorescence analyser. The results show that the Ba5Si8O21∶Eu2+, Dy3+ fluorescent powders synthesized by the high temperature solid-phase method have the best fluorescence property when they are sintered at 1150 ℃ and the Eu2+/Dy3+ ratio (the ratio of mole fraction) is 1∶3. Comparing the high temperature solid-phase method with the microwave combustion method, it is found that the microwave combustion method can reduce the synthesis time of Ba5Si8O21∶Eu2+, Dy3+ significantly, but the luminescent intensity of products is low. Comparing the properties of the synthesized Sr2MgSi2O7∶Eu2+, Dy3+ with those of Ba5Si8O21∶Eu2+, Dy3+, it is found that the type of alkaline earth metal ions has an effect on the emission wavelength of fluorescent powders. Ba5Si8O21∶Eu2+, Dy3+ fluorescent powders have good water resistance, and their fluorescence loss rate is only 2.3% after 24-h water immersion, which can be applied to fluorescent coatings..
Laser & Optoelectronics Progress
- Publication Date: Jan. 01, 1900
- Vol. 54, Issue 10, 101602 (2017)
Medical Optics and Biotechnology
Blue Light Hazard and Non-Visual Biological Effect of LED Backlight Displayer at Different Color Temperatures
Yang Chaopu, Fang Wenqing, Liu Mingbao, Li Chun, Zhang Meili, and Zhou Chunsheng
The spectral distributions of LED backlight displayer are measured at different color temperatures. Several function expressions are fitted according to the related initial data. The variations of illumination factor, blue light hazard factor and circadian factor with color are studied with the utilization of MATLAB. IThe spectral distributions of LED backlight displayer are measured at different color temperatures. Several function expressions are fitted according to the related initial data. The variations of illumination factor, blue light hazard factor and circadian factor with color are studied with the utilization of MATLAB. In the visible range, the blue-light-ratio of LED backlight displayer at different color temperatures is calculated. The result show that illumination factor decreases with the increase of the age and color temperature; blue light hazard factor and circadian factor increase with the increase of color temperature, and decrease with the increase of the age. When the color temperature is 1200 K, the ratio of blue-light-ratio of the displayer to blue-light-ratio of candle is 0.783, and the ratio is 10.294 when the color temperature is 6500 K. The influences of the blue light hazard and non-visual biological effect on young people are relatively large, and the young people should try to reduce color temperature of LED backlight displayer. This research provides theoretical reference for personalized design and color temperature adjustment of LED backlight displayer..
Laser & Optoelectronics Progress
- Publication Date: Jan. 01, 1900
- Vol. 54, Issue 10, 101701 (2017)
Modelling for Personalized Cornea Refractive Surgery and Analysis on Astigmatism Correction
Huang Yiqi, Li Zhuo, and Li Bin
On the basis of the typical structure and parameters of human eyes, we establish personalized -5 D myopic models with two types of astigmatism: corneal astigmatism and ocular residual astigmatism. The corneal ablation is simulated using three typical surgery schemes including spherical, optimized-Q, and wave-front guidOn the basis of the typical structure and parameters of human eyes, we establish personalized -5 D myopic models with two types of astigmatism: corneal astigmatism and ocular residual astigmatism. The corneal ablation is simulated using three typical surgery schemes including spherical, optimized-Q, and wave-front guided laser in situ keratomileusis (LASIK). Spot diagrams at the fovea on retina and wave-front aberration maps of the eyeball before and after surgery are compared. The results show that the spherical correction and optimized-Q surgery can restrain corneal astigmatism, but the rectification to ocular residual astigmatism is poor; spherical correction scheme can introduce substantial spherical aberration, which can be well confined by the optimized-Q surgery scheme, but neither of them is able to reduce other types of high order aberrations; the wave-front guided LASIK can correct any type of myopia, astigmatism, or irregular high order optical aberrations..
Laser & Optoelectronics Progress
- Publication Date: Jan. 01, 1900
- Vol. 54, Issue 10, 101702 (2017)
Optical Design and Fabrication
Design of Medium and Long Distance Automotive Lens for Target Recognition of Vehicles
Zhang Siyuan, Xie Fei, and Wang Jianhua
In order to improve the recognition accuracy of medium and long distance vehicle targets and meet the requirements of the forward preview distance of pilotless automobile, a type of medium and long distance automotive lens suitable for passenger cars is studied through theoretical calculation and optical design softwarIn order to improve the recognition accuracy of medium and long distance vehicle targets and meet the requirements of the forward preview distance of pilotless automobile, a type of medium and long distance automotive lens suitable for passenger cars is studied through theoretical calculation and optical design software ZEMAX-EE. To meet the requirements of the imaging range of the vehicle lens during actual use, the imaging range with different entrance pupil diameters is calculated by using the depth of field formula, when the aiming distance is infinity. Then the lens parameter design scheme which satisfies actual service conditions is determined, and it is easy to design and test. For the automotive lens, the focal length is 40 mm, the field of view is 8.6°, the entrance pupil diameter is 7 mm, the depth of field is 30 m-+∞, and the system total length is less than 38 mm. The simulation results show that the designed lens has good image quality and can meet the design requirements in actual use..
Laser & Optoelectronics Progress
- Publication Date: Jan. 01, 1900
- Vol. 54, Issue 10, 102201 (2017)
Dynamic Illumination Design Method Based on LED Array
Hua Hui, Mao Xianglong, Tan Jiahai, and Yu Weixing
A dynamic illumination design method based on LED array is proposed. First, the position of the LED array unit is selected and the target illumination distribution pattern is uniformly sampled. The illumination distribution matrix of each unit of the LED array is established. Then, the least square mathematical model oA dynamic illumination design method based on LED array is proposed. First, the position of the LED array unit is selected and the target illumination distribution pattern is uniformly sampled. The illumination distribution matrix of each unit of the LED array is established. Then, the least square mathematical model of non-negative constraint is constructed and solved, and the non-negative weight distribution of each element of LED array is calculated. After applying the weights to the LED array, the LED array can approximate a specified illumination pattern within the target region. Based on the LED array, a series of examples are given to form complicated multiple-rings pattern and spiral pattern within the circular and rectangular target regions respectively. The root mean square (RMS) fitting error between the simulated illumination pattern and the target illumination pattern is less than 20% for all the designs, and the minimum RMS fitting error is less than 10%..
Laser & Optoelectronics Progress
- Publication Date: Jan. 01, 1900
- Vol. 54, Issue 10, 102202 (2017)
Optical System Design and Tolerance Analysis of Photoelectric Self-Collimation Theodolite
Wang Guoming, Lao Dabao, and Zhou Weihu
The photoelectric self-collimation theodolite is a kind of precision measurement system that integrates dual functions of the photoelectric autocollimator and the theodolite. The optical path of the photoelectric self-collimation theodolite consists of two parts that include the visual inner-focusing telescope system aThe photoelectric self-collimation theodolite is a kind of precision measurement system that integrates dual functions of the photoelectric autocollimator and the theodolite. The optical path of the photoelectric self-collimation theodolite consists of two parts that include the visual inner-focusing telescope system and the photoelectric self-collimation system. Firstly, the design principles and methods of the common optical path optical system are proposed. The inner-focusing telescope system with good imaging ability and the self-collimation optical system with high resolution are optimally designed. Then, the tolerance analysis and design of the multi-glue prism that influences the image quality most are carried out. And the processing tolerance value which satisfies the imaging requirement and economy is given. At last, the precision of the designed optical system is tested. The experimental results show that the self-collimation accuracy of the designed optical system is 0.6″ within the field of view of ±20″, which can meet the design requirements..
Laser & Optoelectronics Progress
- Publication Date: Jan. 01, 1900
- Vol. 54, Issue 10, 102203 (2017)
Optics at Surfaces
Simulation Analysis on Influence of Metal Nanograting on Graphene Filtering
Sun Bin, Yang Youchang, Wan Meng, and Xie Feifeng
A terahertz (THz) filter based on graphene/metal hybrid nanogratings is studied with the finite element method. Nanocavity arrays can be formed by the hybrid gratings. A THz filter is prepared by using the magnetic Fabray-Perot resonance effect in the nanocavity. The wavelength choice performance of this filter is unafA terahertz (THz) filter based on graphene/metal hybrid nanogratings is studied with the finite element method. Nanocavity arrays can be formed by the hybrid gratings. A THz filter is prepared by using the magnetic Fabray-Perot resonance effect in the nanocavity. The wavelength choice performance of this filter is unaffected by the external environments and the filtering wavelength can also be dynamically controlled. In addition, the filtering performance of this filter can be enhanced via the increase of the graphene layer number..
Laser & Optoelectronics Progress
- Publication Date: Jan. 01, 1900
- Vol. 54, Issue 10, 102401 (2017)
Remote Sensing and Sensors
High Resolution Image Classification Method Combining with Minimum Noise Fraction Rotation and Convolution Neural Network
Chen Yang, Fan Rongshuang, Wang Jingxue, Wu Zenglin, and Sun Ruxing
Aiming at the problems of traditional shallow machine learning methods applied to high resolution image classification, we propose a high resolution image classification method combining with minimum noise fraction (MNF) rotation and convolution neural networks (CNN). MNF is used to analyze the initial unsupervised preAiming at the problems of traditional shallow machine learning methods applied to high resolution image classification, we propose a high resolution image classification method combining with minimum noise fraction (MNF) rotation and convolution neural networks (CNN). MNF is used to analyze the initial unsupervised pre-training CNN. Linear correction function is adopted as the activation function of the neural network to increase the training speed. In order to reduce the missing of image features in the process of the pool, the sampled image features are put into Softmax classifier under the principle of maximizing sampling probability. Experimental image of typical regions is selected and classified by using the proposed classification method, and the classification results are compared with those of support vector machines classification method and artificial neural network classification method. The results show that the classification accuracy of the proposed method is superior to the shallow machine learning classification methods, and can fully excavate the spatial information of high resolution remote sensing images..
Laser & Optoelectronics Progress
- Publication Date: Jan. 01, 1900
- Vol. 54, Issue 10, 102801 (2017)
Reviews
Research Status and Development of Indoor Positioning Based on Visible Light Communication
Zhang Xiaofeng, Wang Min, and Wang Jin
The visible light communication (VCL) based indoor positioning technology combines lighting with communication. Compared with the traditional indoor wireless positioning means, the VCL based indoor positioning technology shows many advantages such as green, energy saving and environmental protection, low cost, no electThe visible light communication (VCL) based indoor positioning technology combines lighting with communication. Compared with the traditional indoor wireless positioning means, the VCL based indoor positioning technology shows many advantages such as green, energy saving and environmental protection, low cost, no electromagnet interference, high precision and wide applications, and it has broad application prospects. We summarize the principles and characteristics of two types of VLC based indoor positioning technologies based on photoelectric detectors and image sensors. We focus on the major problems that exist in VLC based indoor positioning technology such as irrational layout of light source, inter-symbol interference and receiving device with low sensitivity and stability. In addition, some solutions are also proposed, such as proper encoding, orthogonal frequency division multiplexing, diversity reception and filtering techniques. Finally, the future development trend and application perspective of VLC based indoor positioning technology are discussed..
Laser & Optoelectronics Progress
- Publication Date: Jan. 01, 1900
- Vol. 54, Issue 10, 100001 (2017)
U.S. Theater and Strategic UVA-Borne Laser Weapon
Ren Guoguang, Yi Weiwei, Qi Yu, Huang Jijin, and Qu Changhong
Ballistic and cruise missile are the major threat in high technology war, the most efficient defense for ballistic missile is the boost phase interception. First of all, the failure reason and the lessons learned of US air borne laser project are summarized.Then the concept, superiority, research project and current stBallistic and cruise missile are the major threat in high technology war, the most efficient defense for ballistic missile is the boost phase interception. First of all, the failure reason and the lessons learned of US air borne laser project are summarized.Then the concept, superiority, research project and current status, as well as the problems and the challenges of anti-missile UAV-borne laser weapon are reviewed and analyzed. Finally, the principle, characteristics and recent progress and technical challenges of the diode pumped alkali laser and fiber combining laser used in the boost phase interception are discussed and analyzed..
Laser & Optoelectronics Progress
- Publication Date: Jan. 01, 1900
- Vol. 54, Issue 10, 100002 (2017)
Research Progresses on Characterization and Detection Technology of Subsurface Damages in Optical Materials
Wang Huadong, and Zhang Taihua
The systematic characterization and accurate detection of subsurface damage (SSD) are the key to controlling the surface damage in the processing of optical materials. The research progresses on the detection and evaluation methods of SSD in optical materials are reviewed by combining the SSD characterization methods aThe systematic characterization and accurate detection of subsurface damage (SSD) are the key to controlling the surface damage in the processing of optical materials. The research progresses on the detection and evaluation methods of SSD in optical materials are reviewed by combining the SSD characterization methods and the detection technologies. The structures and the characterization parameters of SSD induced by the ultra-precision machining are analyzed. Several typical destructive detection technologies and their technical features and application ranges are introduced aiming at the geometric characterization parameters of SSD. Several non-destructive detection technologies which meet the detection requirements of ultra-precision machining are introduced emphatically, and their technical advantages and development bottlenecks are also analyzed. The comparison for the SSD characterization and detection technologies between at home and abroad is performed, and the developing trend of SSD detection technology is presented..
Laser & Optoelectronics Progress
- Publication Date: Jan. 01, 1900
- Vol. 54, Issue 10, 100003 (2017)
Development and Key Technologies of Synthetic Aperture Ladar Imaging
Lü Yakun, and Wu Yanhong
Synthetic aperture ladar (SAL) breaks through the diffraction restrict of laser, which is able to afford the need of high precision and real time imaging for the remote targets and scenes. The development situation of SAL at home and abroad is analyzed in detail, through two aspects of theoretical status and experimentSynthetic aperture ladar (SAL) breaks through the diffraction restrict of laser, which is able to afford the need of high precision and real time imaging for the remote targets and scenes. The development situation of SAL at home and abroad is analyzed in detail, through two aspects of theoretical status and experimental progress. On this basis, the key technologies such as SAL laser source, emission signal waveform, laser transmission characteristics and target reflection characteristics, imaging algorithm and motion compensation are summarized and analyzed. It lays the foundation for further study and practical application of SAL..
Laser & Optoelectronics Progress
- Publication Date: Jan. 01, 1900
- Vol. 54, Issue 10, 100004 (2017)
Research Progress of the Photonic Integrated Chaotic Lasers
Wang Yongsheng, Wang Yuncai, and Guo Yanqiang
The chaos laser has received in-depth investigation in recent years owing to its important applications, such as secure communications, fast physical random bit generation, chaotic laser radar, chaotic time domain reflectometer, optical fiber sensing and ranging. The integrated chips have advantages over those setups cThe chaos laser has received in-depth investigation in recent years owing to its important applications, such as secure communications, fast physical random bit generation, chaotic laser radar, chaotic time domain reflectometer, optical fiber sensing and ranging. The integrated chips have advantages over those setups composed of discrete components for some unique virtues such as smaller size, lower cost, better stability and reproducibility via mass production. Combining with the advantages of the chaotic applications and integrated chips, the integration of chaotic semiconductor laser arises at the historic moment. The integration of chaotic semiconductor laser is divided into five categories to introduce the domestic and oversea research progress of the relevant institutions in the respect of integrated structure, size of the integrated area, features of integration and applications of integrated chaotic laser. Finally, we design a novel butterfly packaging integrated chaotic semiconductor laser with an external-cavity..
Laser & Optoelectronics Progress
- Publication Date: Jan. 01, 1900
- Vol. 54, Issue 10, 100005 (2017)
Scattering
A Modified Phong Model for Fresnel Reflection Phenomenon of Commonly Used Materials for Space Targets
Liu Chenghao, Li Zhi, and Xu Can
Based on the analysises of the measured bidirectional reflectance distribution function (BRDF) data and the limitations in Phong model, a modified model is proposed to describe the Fresnel reflection properties. On the basis of the classical Phong model, two parameters are added to adjust the strength and the decay ratBased on the analysises of the measured bidirectional reflectance distribution function (BRDF) data and the limitations in Phong model, a modified model is proposed to describe the Fresnel reflection properties. On the basis of the classical Phong model, two parameters are added to adjust the strength and the decay rate of Fresnel reflection in different materials, respectively. The genetic algorithm is used to fit the BRDF data from 4 kinds of commonly used materials for space targets, and the fitting errors of the modified model and the classical Phong model are compared and analyzed. The results show that the fitting precision obtained by the modified model is 90% higher than that obtained by the classical Phong model for the materials with an obvious Fresnel reflection phenomenon, which verifies the effectiveness of the modified model. For the materials with a weak Fresnel reflection phenomenon, the fitting errors obtained by the two models are equivalent, which represents the robustness of the modified model. The modified model can better describe the Fresnel reflection phenomenon while keeping the orginal excellent description ability of the Phong model..
Laser & Optoelectronics Progress
- Publication Date: Jan. 01, 1900
- Vol. 54, Issue 10, 102901 (2017)
Spectroscopy
Feature Selection Algorithm Application in Near-Infrared Spectroscopy Classification Based on Binary Search Combined with Random Forest Pruning
Liu Ming, Li Zhongren, Zhang Haitao, Yu Chunxia, Tang Xinghong, and Ding Xiangqian
In view of the problems of the random forest in the feature selection process in high-dimensional spaces, such as calculation complexity, large model memory overhead, and low classification accuracy, a feature selection algorithm named binary search random forest pruning (BSRFP) is proposed. This algorithm firstly obtaIn view of the problems of the random forest in the feature selection process in high-dimensional spaces, such as calculation complexity, large model memory overhead, and low classification accuracy, a feature selection algorithm named binary search random forest pruning (BSRFP) is proposed. This algorithm firstly obtains the feature importance scores according to the purity Gini index, and deletes features with low importance scores. The optimal feature subset and the classifier with the highest classification accuracy are then obtained with utilization of the pruning technique combining binary search with the diversity among base classifiers. To verify the effectiveness of this algorithm, a cigarette quality recognition model is established and compared with other methods. The results show that the binary search algorithm simplifies the feature search process, and the RFP algorithm reduces the size of random forest algorithm. The classification accuracy of the random forest pruning algorithm is 96.47%. The features selected by using BSRFP algorithm are more correlated, and the algorithm provides higher accuracy of cigarette quality recognition..
Laser & Optoelectronics Progress
- Publication Date: Jan. 01, 1900
- Vol. 54, Issue 10, 103001 (2017)
Thin Films
Influence of Ion-Assisted Deposition on Crystal Structures and Optical Characteristics of ZnS Films
Feng Yidong, Qin Yang, and Yu Tianyan
The physical and optical properties of ion-assisted deposited ZnS films with different ion beam densities are investigated. The study results show that the phenomenon of inhomogeneous growth of ZnS films happens during the ion-assisted deposition. The inhomogeneity and refractive index of ZnS films increase with the inThe physical and optical properties of ion-assisted deposited ZnS films with different ion beam densities are investigated. The study results show that the phenomenon of inhomogeneous growth of ZnS films happens during the ion-assisted deposition. The inhomogeneity and refractive index of ZnS films increase with the increase of ion beam density, and the crystallization degree of films also increases. The inhomogeneity of films causes more difficulties for the preparation and design of films, especially an uncertainty for the preparation of a multilayer film system. The results provide an important reference for the development and production of infrared optical ZnS films..
Laser & Optoelectronics Progress
- Publication Date: Jan. 01, 1900
- Vol. 54, Issue 10, 103101 (2017)
Fabrication and Opto-Electronic Properties of ZnO/Ag/ZnO Composite Films at Room Temperature
Guo Kai, Yu Tao, Song Binbin, Li Xinlian, and Zhao Shuli
ZnO/Ag/ZnO three-layer composite films are fabricated by means of radio frequency magnetron sputtering and electron beam evaporation. The influences of Ag film thicknesses and electron beam evaporation deposition rates on the opto-electronic properties of composite films are investigated. The experimental results show ZnO/Ag/ZnO three-layer composite films are fabricated by means of radio frequency magnetron sputtering and electron beam evaporation. The influences of Ag film thicknesses and electron beam evaporation deposition rates on the opto-electronic properties of composite films are investigated. The experimental results show that, when the thickness of Ag films is 8 nm and the deposition rate of electron beam evaporation is 0.5 nm·s-1, the properties of composite films are optimal. The square resistance is 6.01 Ω and the average transmissivity of light whose wavelength is at range of 400 nm and 800 nm is 91.39%. The ZnO/Ag/ZnO composite films have good opto-electronic properties after optimization..
Laser & Optoelectronics Progress
- Publication Date: Jan. 01, 1900
- Vol. 54, Issue 10, 103102 (2017)
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