Journals >Chinese Journal of Lasers
Contents
2013
Volume: 40 Issue 8
46 Article(s)
Export citation format
Research Article
Simulation Model of Laser Atmospheric Transmission Characteristics Using Arbitrary Thickness Random Phase Screen
Wang Rui, Wang Tingfeng, and Sun Tao
In order to analysis the Gaussian beam transmission characteristics, according to the numerical simulation method of random phase screen, the Rytov weak turbulence theory is used to analyze each statistical quantity. The numerical model of Gaussian beam propagation through an arbitrary thickness phase screen is establiIn order to analysis the Gaussian beam transmission characteristics, according to the numerical simulation method of random phase screen, the Rytov weak turbulence theory is used to analyze each statistical quantity. The numerical model of Gaussian beam propagation through an arbitrary thickness phase screen is established, based on the Kolmogorov spectrum, and the analytic expression which is easy to be treated is also given. Meantime, the scintillation index and Rytov variance are analyzed. The results indicate that the application range of arbitrary thickness phase screen model is wider than the thin phase screen, and the statistic describing is more accurate..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 8, 813001 (2013)
Biomedical Photonics and Laser Medicine
Full Range Optical Coherence Tomography without Additional Group Delay Based on Spatial Interferograms Modulation
Hong Wei, Ding Zhihua, and Yan Yangzhi
Full range optical coherence tomography (OCT) without additional group delay based on spatial carrier frequency is developed. A grating takes place of the mirror in the reference arm of the traditional OCT system and phase difference between adjacent A-scans without additional optical path difference is introduced by uFull range optical coherence tomography (OCT) without additional group delay based on spatial carrier frequency is developed. A grating takes place of the mirror in the reference arm of the traditional OCT system and phase difference between adjacent A-scans without additional optical path difference is introduced by using phage modulation. Spatial interferograms is obtained from the detected OCT signal by the transverse Fourier transform and filtering. For filtering signal, an inverse Fourier transform is done. A full range OCT image can be obtained after axial Fourier transform. The theory and the system based on the spatial carrier frequency are introduced. The investigation on the image quality under different modulation frequencies is experimentally conducted. The full range OCT images of mirror and finger are presented..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 8, 804001 (2013)
Holography and Information Processing
[in Chinese]
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 8, 809002 (2013)
Automatic Registration Algorithm for the Point Clouds Based on the Normal Vector
Tao Haiji, and Da Feipeng
To registration problem of scanned point clouds data without any additional information, a novel normal vector based automatic registration algorithm is proposed. The feature points are extracted according to the change of local normal vector, and the initial matching points are found through histogram feature proposedTo registration problem of scanned point clouds data without any additional information, a novel normal vector based automatic registration algorithm is proposed. The feature points are extracted according to the change of local normal vector, and the initial matching points are found through histogram feature proposed in this paper. The random sample consensus (RANSAC) is used to get the accurate matching points according to the distance restriction. The initial registration parameters are computed by the quaternion, and iterative closet point (ICP) algorithm is used to get accurate result. The experimental results show that this algorithm is effective..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 8, 809001 (2013)
Reconstructed Image Enhancement of Digital Holography in Contourlet Domain Based on Particle Swarm Optimization
Wu Yiquan, and Yin Jun
Aiming at the problem of low contrast, blurred edges and textures, and speckle noise of reconstructed image in digital holography, an adaptive enhancement method for reconstructed image of digital holography in contourlet domain based on uniform searching particle swarm optimization is proposed. Median filtering algoriAiming at the problem of low contrast, blurred edges and textures, and speckle noise of reconstructed image in digital holography, an adaptive enhancement method for reconstructed image of digital holography in contourlet domain based on uniform searching particle swarm optimization is proposed. Median filtering algorithm is used to suppress speckle noise of the reconstructed image. After the contourlet decomposition, edge enhancement is performed for the band-pass directional subbands by a nonlinear gain function. While the coefficients of low-pass subbands are adjusted by the gain function based on a gray-scale transform and the local mean. The gray-scale transform aims to expand the dark areas of digital holographic image. The undetermined parameters are found by uniform searching particle swarm optimization. The fitness function takes into account the contrast, definition and peak signal-to-noise ratio of image. A large number of experimental results show that, compared with three existing enhancement methods, the proposed method can more effectively improve the contrast and definition of reconstructed image in digital holography, highlight edges and textures, and suppress speckle noise. As a result, the measurement accuracy of digital holography can be improved..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 8, 809002 (2013)
Research on Large-Scale Face Recognition Using Opto-Electronic Hybrid Matched Filtering Correlator
Guo Guangming
According to the particularity of large scale face recognition, an opto-electronic hybrid matched filtering correlator and a new method for large scale face recognition are proposed. In order to achieve 1N identification and effectively improve the speed and accuracy of the identification, opto-electronic hybrid matcheAccording to the particularity of large scale face recognition, an opto-electronic hybrid matched filtering correlator and a new method for large scale face recognition are proposed. In order to achieve 1N identification and effectively improve the speed and accuracy of the identification, opto-electronic hybrid matched filtering correlator is used to complete related calculation which consumes the most time in image recognition. At the same time, computer simulation and experiment test are used to verify this method. The computer simulation results show that the correlator can output sharp correlation peak, and has a very good recognition ability. When testing in 200 persons, the recognition threshold value is 0.6, false match rate is 0%, and false non-match rate is 1%..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 8, 809003 (2013)
Analysis and Feature Extraction of Laser Micro-Doppler Signatures Based on Hilbert-Huang Transforms
Peng Mingjin, and Li Zhi
In the laser micro-Doppler signature analysis of vibrating targets, the joint time-frequency methods can provide useful information for target detection, classification and recognition. The analysis of the general nonlinear and non-stationary signal with traditional time-frequency analysis method can effectively extracIn the laser micro-Doppler signature analysis of vibrating targets, the joint time-frequency methods can provide useful information for target detection, classification and recognition. The analysis of the general nonlinear and non-stationary signal with traditional time-frequency analysis method can effectively extract signal characteristics. But there are great limitations in the strong background noise and weak modulation channel conditions. Hilbert-Huang transform (HHT) is employed as a new approach in micro-Doppler analysis. Simulation results in Matlab software show that it can achieve better performance than smoothed pseudo Wigner-Ville distribution (SPWVD) in different channel conditions..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 8, 809004 (2013)
Laser Manufacturing
[in Chinese]
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 8, 802005 (2013)
Micromachining of Metals and Thermal Barrier Coatings Using a 532 nm Nanosecond Fiber Laser
Lai Hongkun, and Qi Huan
Precision manufacturing of the shaped film cooling holes on turbine blades is a challenge, especially when the metal blades are coated with thermal barrier coatings (TBC). A 532 nm nanosecond pulsed ytterbium fiber laser is used to study the physical interactions between pulsed laser beam and metal or ceramic materialsPrecision manufacturing of the shaped film cooling holes on turbine blades is a challenge, especially when the metal blades are coated with thermal barrier coatings (TBC). A 532 nm nanosecond pulsed ytterbium fiber laser is used to study the physical interactions between pulsed laser beam and metal or ceramic materials. Using a semi-empirical model and finite element model, we study the interaction of laser and material, and predict laser ablation surface geometry. Results are compared between modelling and experimental data. Optimized machining parameters are recommended with the aim of maximum process efficiency and minimum thermal effects such as recast layer, edge protrusions and microcracks. By varying depth of focus, scanning mode, beam diameter and power density, the interaction between laser and stainless steel, copper, TBC and IN718 are investigated. Laser ablation energy density threshold values and the best material removal rate are obtained, and the result of simulation is verified..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 8, 803001 (2013)
Comparison of Melting Efficiency in High Power Fiber Laser and CO2 Laser Welding
Zou Jianglin, Wu Shikai, Xiao Rongshi, Zhang Xinyi, and Niu Jianqiang
Bead-on-plate welding is carried out with an IPG YLS-6000 fiber laser and a slab DC035 CO2 laser under the similar conditions. The melting efficiencies are calculated based on the measured weld cross-sectional areas with an Olympus microscope. The results show that the melting efficiency increases firstly and then decrBead-on-plate welding is carried out with an IPG YLS-6000 fiber laser and a slab DC035 CO2 laser under the similar conditions. The melting efficiencies are calculated based on the measured weld cross-sectional areas with an Olympus microscope. The results show that the melting efficiency increases firstly and then decreases with welding speed increasing in both cases. However, the welding speed corresponding to the maximum melting efficiency is far greater in fiber laser welding than that in CO2 laser welding. Further analysis demonstrates that the difference of the melting efficiency is relevant to the inherent difference of the energy coupling. Therefore, from the viewpoint of welding efficiency, fiber laser is more suitable for high-speed welding, while CO2 laser is more suitable for low-speed welding..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 8, 803002 (2013)
Influence of Graphite/Ni on Microstructure and Properties of Laser Clad Ni-Based Alloy Coatings
Ma Chao, and Wang Cunshan
Ni-based composite coatings with different graphite/Ni contents are prepared by laser cladding on the 40CrNi2Si2MoV steel. The microstructure and properties of the composite coatings are investigated by means of X-ray diffraction (XRD), scanning electron microscopy, energy dispersive X-ray (EDX) spectroscopy, Vickers hNi-based composite coatings with different graphite/Ni contents are prepared by laser cladding on the 40CrNi2Si2MoV steel. The microstructure and properties of the composite coatings are investigated by means of X-ray diffraction (XRD), scanning electron microscopy, energy dispersive X-ray (EDX) spectroscopy, Vickers hardness tester, and friction wear testing machine. The results show that the composite coatings mainly consist of γ-Ni, Ni3B, M23C6, and M7C3 phases. But with the graphite/Ni addition increasing, the contents of the eutectic increase. The graphite is observed as the graphite/Ni addition is beyond 10.0% (volume fraction). The changes in the microstructure improve the hardness and the wear resistance of the coatings while the anti-friction property presents a trend of first decreasing and then increasing, and the lowest anti-friction property is obtained as the graphite/Ni addition is 6.0%..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 8, 803003 (2013)
Ultrasonic effect on Laser Cladding BT20 Titanium Alloy Process
Wang Wei, Guo Pengfei, Zhang Jianzhong, Yang Guang, Bian Hongyou, Qin Lanyun, Wang Wei, Cui Baolei, Cai Gan, Wang Ting, and Cai Lei
Ultrasonic assisted laser cladding technology is developed on the basis of laser cladding technology, and the technology that ultrasonic is introduced to laser cladding can improve the quality of the cladding layer. The laser cladding experiment is done by adding ultrasound vibration with a frequency of 19.56 kHz on tiUltrasonic assisted laser cladding technology is developed on the basis of laser cladding technology, and the technology that ultrasonic is introduced to laser cladding can improve the quality of the cladding layer. The laser cladding experiment is done by adding ultrasound vibration with a frequency of 19.56 kHz on titanium alloy matrix of BT20. Based on the experiment the effects of ultrasound on the laser cladding process is studied. The results show that, under the condition of using 2.2 W ultrasonic vibration, the surface flatness of the cladding layer is good, the porosity rate of internal organization is dropped to 0.75%, the grain size is decreased by about 42%, the α-sheet length is decreased by 23.9%, but the stacking efficiency in the direction of deposition and growth is reduced by 36.7%..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 8, 803004 (2013)
Ignition and Combustion Characteristics of AP/HTPB Composite Propellant by Laser
Zhang Lingke, Zhao Wei, and Wu Lizhi
It is contributed to reveal the combustion consistent mechanism of ammonium perchorate and hydroxyl-terminated pdybutadiene (AP/HTPB) composite propellant by studying its characteristics of ignition and combustion based on experiment. The firing efficiency of base bleed projectile will increase by improving combustion It is contributed to reveal the combustion consistent mechanism of ammonium perchorate and hydroxyl-terminated pdybutadiene (AP/HTPB) composite propellant by studying its characteristics of ignition and combustion based on experiment. The firing efficiency of base bleed projectile will increase by improving combustion characteristic. Laser has the advantages of adjustable energy and high output stability, so it is the best energy source for energetic materials ignition and combustion test. The ignition delay time of AP/HTPB composite propellant samples is researched by using high power solid-state laser and high speed video system. The ignition delay time is dramaticlly shortened with laser intensity increasing and then tends to be gentle. The combustion speed is calculated as 3.41 mm/s based on combustion ordinal images and image processing technology. Numerical simulations of ignition and combustion of the test samples are conducted by building the one-dimensional laser ignition model for energetic materials. The calculated results of ignition delay time are in accordance with the test greatly, and the temperature variation with time and intensity is obtained..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 8, 803005 (2013)
Experimental Study on Improving High-Cycle Fatigue Performance of TC11 Titanium alloy by Laser Shock Peening
Nie Xiangfan, He Weifeng, Zang Shunlai, Wang Xuede, and Li Yuqin
The standard vibration fatigue specimens, made of TC11 titanium alloy, are treated by laser shock peening (LSP). The high-cycle vibration tests are conducted to verify the reinforcement effect, and the fracture analysis is utilized to analyze the fatigue mechanism of the treated specimens. The strengthening mechanism oThe standard vibration fatigue specimens, made of TC11 titanium alloy, are treated by laser shock peening (LSP). The high-cycle vibration tests are conducted to verify the reinforcement effect, and the fracture analysis is utilized to analyze the fatigue mechanism of the treated specimens. The strengthening mechanism of fatigue performance is explained by the experiments of microstructure, residual stress and microhardness. The tests results show that the fatigue limit is improved from 483 MPa to 593 MPa by LSP. Fatigue crack of specimens treated by LSP initiates in the subsurface of 0.2-mm depth with a greater flatness area and lots of second-cracks and tight fatigue bands. A layer with nanocrystals is generated on the surface by LSP, and the size of nanocrystal is about 40~80 nm. LSP introduce a great compressive residual stress in the material with a 1-mm thick plastic deformation layer. The residual stress in the surface can reach -591.5 MPa, while the surface hardness is increased by 19%. The combined actions of high structure refinement and high compressive residual stress are the main causes of the fatigue performance improvement, which block fatigue crack initiating and reduce crack growth rate..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 8, 803006 (2013)
Generation of Three-Dimensional Laser Cutting Path for Sheet Metal Part
Zhu Hu, Han Fuchen, and Lin Wenwen
A method for automatically generation of sheet metal three-dimensional (3D) laser cutting path based on the incision filled model is proposed considering the sheet metal forming process. Automatic selection of incision features is realized through automatic recognition of incision features by using the concave edges beA method for automatically generation of sheet metal three-dimensional (3D) laser cutting path based on the incision filled model is proposed considering the sheet metal forming process. Automatic selection of incision features is realized through automatic recognition of incision features by using the concave edges between the incision faces, and the laser beam radius compensation is done through the offset of the edge loop of incision by using vertex offset method. On the basis of the incision features filling and the remodeling of the model, the laser head posture is determined using two normal vectors of the two triangles that shares the edge on which the laser beam points are located, which ensures the laser head perpendicular to the surface of workpiece in the whole process of laser cutting. The case studies show that the above algorithm is feasible and the system is stable and reliable..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 8, 803007 (2013)
Characteristics of Laser Pulsed Welding at Intersected Points of Zircaloy-4 Alloy
Cai Chuang, Li Ruifeng, Tao Wang, Li Liqun, Zhao Huirong, Hou Xue, and Yan Xianghe
A study on intersected points of Zircaloy-4 alloy is carried out by using pulsed Nd:YAG laser. The effects of laser parameters on the intersected points are analyzed from the appearances, depth-to-width ratio and mechanical properties. The results show that the protrusion of the weld beads can not meet the demand becauA study on intersected points of Zircaloy-4 alloy is carried out by using pulsed Nd:YAG laser. The effects of laser parameters on the intersected points are analyzed from the appearances, depth-to-width ratio and mechanical properties. The results show that the protrusion of the weld beads can not meet the demand because the convex platform fails to be molten amply with the improper parameters. With the peak power increasing and the pulse width decreasing, or the number of shots increasing when the single pulse energy remains unchanged, the protrusion of the weld beads decreases, and the depth-to-width ratio of the weld beads increases. The maximum tensile loads of the intersected points are proportional to the depth-to-width ratio..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 8, 803008 (2013)
Stress Simulation of Aluminum Alloy Irradiated by Long Pulsed Laser and Continuous Wave Laser
Xiao Jing, He Hengxiang, and Xia Huijun
A three-dimensional finite element model is established to perform the thermo-elastic-plastic analysis on stress and deformation of 2A12 aluminum alloy irradiated by lasers with different parameters in ANSYS software. The results show that with an assistant continuous wave (CW) laser to preheat the material, the effectA three-dimensional finite element model is established to perform the thermo-elastic-plastic analysis on stress and deformation of 2A12 aluminum alloy irradiated by lasers with different parameters in ANSYS software. The results show that with an assistant continuous wave (CW) laser to preheat the material, the effect of long pulsed laser efficiently increases with the increase of preheat time, materials yield time shortens, plastic deformation and yield zone augrrent. Irradiated by long pulsed laser with duty cycle of 10%, the temperature rise and deformation accretion of 2A12 aluminum alloy between pulses are not significant because of its high thermal conductivity. Increasing the preheat time is a more effective method than the power density increasing of CW laser to increase the plastic damage of material irradiated by the same long pulsed laser when their power densities are at 104 W/cm2 level..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 8, 803009 (2013)
Laser Physics
Develop and Analysis of Nanosecond Pulse Width Nd:YAG Laser for Laser Peening
Qiao Hongchao, Zhao Jibin, and Lu Ying
For the laser peening technology which is a recently-developed surface treatment method designed to improve the fatigue life of mechanical parts, using a oscillation eight-stage amplified system structure and the modular design method, high-energy, short-pulse and high-frequency Nd:YAG solid-state lasers are developed.For the laser peening technology which is a recently-developed surface treatment method designed to improve the fatigue life of mechanical parts, using a oscillation eight-stage amplified system structure and the modular design method, high-energy, short-pulse and high-frequency Nd:YAG solid-state lasers are developed. Design scheme of the laser and the characteristics of laser beam transmission are presented and discussed. At ambient temperature which changes less than 2 ℃ and after 20 min of warm-up, the technical parameters such as the maximum single pulse energy of 25 J, energy instability less than 3%, pulse width which can be continuously adjustable between 16 ns and 20 ns, pulse width instability less than ±1 ns, beam divergence less than 2.5 mrad, and the maximum single frequency of 5 Hz are achieved. To further verify the performance of the lasers, a TC4 titanium alloy work-piece is tested with the Nd:YAG lasers. The tested results show that the compressive residual stress is greatly improved and the performance of the lasers is excellent..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 8, 802001 (2013)
Experimental Study on Passively Q-Switched Laser with Yb:GdCOB Crystal
Dai Qibiao, Yi Hongying, Tian Xueping, Han Wenjuan, and Liu Junhai
Passively Q-switched laser operation with Yb:GdCOB crystal is demonstrated in a plano-concave resonator, utilizing a Cr4+:YAG saturable absorber. When the absorbed pump power of the 2-mm thick X-cut crystal is 6.3 W, an average pulsed output power of 0.62 W, with polarization parallel to the Z principal axis, is generaPassively Q-switched laser operation with Yb:GdCOB crystal is demonstrated in a plano-concave resonator, utilizing a Cr4+:YAG saturable absorber. When the absorbed pump power of the 2-mm thick X-cut crystal is 6.3 W, an average pulsed output power of 0.62 W, with polarization parallel to the Z principal axis, is generated at a pulse repetition frequency of 3.6 kHz. The resulting pulse energy, duration, and peak power are 172 μJ, 20 ns, and 8.6 kW, respectively..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 8, 802002 (2013)
Propagation Characteristics of Simple Cylindrical Polarized Beam
Guo Fuyuan, Li Lianhuang, Zheng Hua, Zhang Zhen, and Lin Xiaoming
Based on the second order differential equation which describes the radial and azimuthal electric field components, the characteristics of eigen mode field of simple cylindrical polarized beam are analyzed. According to the formulae of coordinate transformation, the Rayleigh-Sommerfeld scalar diffraction integral formuBased on the second order differential equation which describes the radial and azimuthal electric field components, the characteristics of eigen mode field of simple cylindrical polarized beam are analyzed. According to the formulae of coordinate transformation, the Rayleigh-Sommerfeld scalar diffraction integral formula is converted into a calculation formula for the radial and azimuthal electric field components of far field diffraction of the simple cylindrical polarized beam. As the relationship between the spatial frequency spectrum and electric field distribution of the diffraction source is employed, a calculation formula for the spot radius and spatial frequency radius by the differential operator method is suggested. It can be used to calculate the beam propagation factor of the cylindrical polarized beam. Then, the practical applicability of the above formulae is clearly shown through the beam parameters calculation of the LG10 mode cylindrical polarized Laguerre-Gaussian beam..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 8, 802003 (2013)
Influence of Photon Absorption of Ground State Molecules in Resonator Cavity of HF-DF Dual-Band Chemical on Laser Output Performance
Sun Xu, Yuan Shengfu, Luo Wei, and Yan Baozhu
Influence of photon absorption of ground state molecules in resonator cavity on HF-DF dual-band chemical laser output performance is investigated through experiments. Variations of spectra and output powers of HF laser and DF laser operated with different positions of H2/D2 injection are measured and analyzed. The resuInfluence of photon absorption of ground state molecules in resonator cavity on HF-DF dual-band chemical laser output performance is investigated through experiments. Variations of spectra and output powers of HF laser and DF laser operated with different positions of H2/D2 injection are measured and analyzed. The results show that the spectral lines of 1P (the P-branch transition between vibrational states of ν=1→ν=0) are absorbed by the ground state molecules through the mechanism of single-photon resonance absorption. The spectral lines of 2P (the P-branch transition of ν=2→ν=1) are absorbed by the ground state molecules through the mechanism of double-photon resonance absorption one by one. Cascading transition effect of lasing band between vibration-rotational states exists in some extent. Output power of HF laser decreases by approximately 50%, and output power of DF laser decreases by approximately 90% when the amount of ground state molecules and the amount of excited state molecules are equivalent. Traditional fuel compositions are not applicable for developing combustor-driven HF-DF dual-band chemical lasers..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 8, 802004 (2013)
Sub-Nanosecond Yb-Doped Fiber Amplifier and Its Second Harmonic Generation Characteristics
Wang Ziwei, Du Songtao, He Jing, Wang Zhaokun, Zhou Jun, Wei Yunrong, Meng Junqing, and Li Xiaojun
A Q-switched Nd:YAG/Cr4+:YAG laser is used to seed a one-stage amplifier featuring backward pumped Yb-doped double-cladding fiber as the power amplifier. Average power of 5.5 W with repetition rate of 9 kHz is achieved, corresponding to pulse duration of 575 ps and peak power of 1 MW. Based on the fiber amplifier at 2.A Q-switched Nd:YAG/Cr4+:YAG laser is used to seed a one-stage amplifier featuring backward pumped Yb-doped double-cladding fiber as the power amplifier. Average power of 5.5 W with repetition rate of 9 kHz is achieved, corresponding to pulse duration of 575 ps and peak power of 1 MW. Based on the fiber amplifier at 2.7 W, 1.3 W green laser is obtained by single-pass frequency doubling using non-critical phase matching LBO crystal at 150.5 ℃, and its peak power reaches 250 kW, with conversion efficiency of 48%..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 8, 802005 (2013)
Influence of Nitric Oxide on the Singlet Delta Oxygen Yield by Discharge
Li Liucheng, Duo Liping, Tang Shukai, Jin Yuqi, Li Guofu, Wang Zengqiang, Wang Jian, Wang Yuanhu, and Yu Haijun
Singlet delta oxygen O2(a1Δ) molecules are generated by O2/He gaseous mixture dielectric barrier radio-frequency discharge. NO gas is added into main gas flow to improve the relative yield of O2(a1Δ). Influence of NO on the relative yield of O2(a1Δ) is examined by observing the O2(a1Δ) emission intensity as a function Singlet delta oxygen O2(a1Δ) molecules are generated by O2/He gaseous mixture dielectric barrier radio-frequency discharge. NO gas is added into main gas flow to improve the relative yield of O2(a1Δ). Influence of NO on the relative yield of O2(a1Δ) is examined by observing the O2(a1Δ) emission intensity as a function of NO flow rate. The experimental results show that the O2(a1Δ) relative yield reaches a saturation with the increase of NO flow rate and then slowly decreases. The optimal NO flow rate is about 3% of O2 flow rate under the conditions of the experiments. A new reaction mechanism including three-body oxygen atom recombination is proposed. According to the new mechanisms, a fitting function is given which agrees well with the experimental results. The rate constant of the new mechanism is obtained to be 1.8×10-30 cm6/s..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 8, 802006 (2013)
800 mJ High Beam Quality All-Solid-State 1319 nm Pulsed Laser
Li Nan, Pang Yu, Lu Yanhua, Zhang Lei, Xie Gang, Wang Weimin, and Xu Xiaoxiao
A high energy and high beam quality laser diode pumped all-solid-state laser is reported. Master oscillator and power amplifier construction is used. The 1338 nm and 1064 nm oscillations are suppressed by coating reflector and inserting 45° mirror to increase losses. A temperature-controlled Fabry-Porro etalon is A high energy and high beam quality laser diode pumped all-solid-state laser is reported. Master oscillator and power amplifier construction is used. The 1338 nm and 1064 nm oscillations are suppressed by coating reflector and inserting 45° mirror to increase losses. A temperature-controlled Fabry-Porro etalon is inserted in resonant cavity to realizing linewidth narrowing and wavelength selecting. In order to achieve high output energy, the laser is amplified twice in pre-amplifier and main amplifier. Drive source signal is delayed to make injected laser pulse of main amplifier and drive source pulse time-synchronization better. When pumping current of the main amplifier is 140 A, the laser output energy is 800 mJ, the beam quality foctor M2 is 1.49, and the linewidth is 1.05 GHz. The repetition frequency is 50 Hz with the pulse width of about 200 μs..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 8, 802007 (2013)
Preliminary Analysis of Laser Sustained Plasma Propulsion Mechanism
Zhang Xingqiang, and Lu Jianye
Laser sustained plasma (LSP) propulsion mechanism is the key to laser propulsion technology. On the basis of the average atom (ion) model (AAM) and the collision radiation model (CRM), the interactive process between laser and plasma is simulated by coupling method to obtain some characteristic parameters. The experimeLaser sustained plasma (LSP) propulsion mechanism is the key to laser propulsion technology. On the basis of the average atom (ion) model (AAM) and the collision radiation model (CRM), the interactive process between laser and plasma is simulated by coupling method to obtain some characteristic parameters. The experimental results of laser shooting carbon target prove the exactness of simulated results, and show that laser dipulse shooting carbon target can produce more impulse coupling coefficients by 50% at maximum than that by single pulse, which is favored to laser propulsion. This meaningful work will provide reference for further investigation on laser sustained plasma propulsion..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 8, 802008 (2013)
Materials and Thin Films
[in Chinese]
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 8, 803001 (2013)
[in Chinese]
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 8, 803005 (2013)
Interference Theory of the Defect Mode in One-Dimensional Doped Photonic Crystal
Liu Qineng
In order to explain the reason of the defect mode in one-dimensional (1D) doped cycle photonic crystal, a multiple-beam interference model of 1D doped photonic crystal is established. Interference theory of the defect mode in 1D doped photonic crystal is established by interference theory, and the mechanism of the defeIn order to explain the reason of the defect mode in one-dimensional (1D) doped cycle photonic crystal, a multiple-beam interference model of 1D doped photonic crystal is established. Interference theory of the defect mode in 1D doped photonic crystal is established by interference theory, and the mechanism of the defect mode of 1D doped photonic crystal is explained. The defect modes are studied by interference theory and characteristic matrix method, and their conclusion are the same..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 8, 806001 (2013)
Three-Dimensional Temperature Field of Material Irradiated by Continuous Wave Laser
Zhang Yingcong, Shen Hua, and Zhu Rihong
Based on the actual situation of continuous wave (CW) laser heating target material, the three-dimensional physical model of material irradiated by CW-laser is established. Combining with the actual boundary conditions, the analytical expression of the transient temperature field of the material is deduced based on theBased on the actual situation of continuous wave (CW) laser heating target material, the three-dimensional physical model of material irradiated by CW-laser is established. Combining with the actual boundary conditions, the analytical expression of the transient temperature field of the material is deduced based on the integral transform method. The temperature rising process of material irradiated by CW-laser is simulated numerically using Matlab software, the influences of the anisotropy of the material is analysed, and the influences of the laser parameters, irradiation time and the environmental changes on the temperature rise of the material are discussed. The results show that the anisotropy of the material will lead to an asymmetric temperature rise, the temperature rise increases with the increase of laser power and irradiating time, and the convective heat transfer coefficient between the material sides and the air plays an important role in the temperature distribution of the material..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 8, 806002 (2013)
Spectral Properties of Tm3+-Doped Silica Glasses and Laser Behaviors of Fibers by Sol-Gel Technology
Li Zhilan, Wang Shikai, Wang Xin, Guan Peiwen, Li Wentao, Wang Meng, Yu Chunlei, Zhang Lei, Li Kefeng, Chen Danping, and Hu Lili
Tm3+-doped silica glasses with molar fraction composition of 0.3Tm2O3-0.3xAl2O3-(100-0.3-0.3x)SiO2 (x=8, 10, 15, 20) denoted as ATS glasses are prepared by sol-gel method. The spectroscopic properties of the bulk glasses are investigated. The maximum emission cross section and measured fluorescence lifetime at 1811 nm Tm3+-doped silica glasses with molar fraction composition of 0.3Tm2O3-0.3xAl2O3-(100-0.3-0.3x)SiO2 (x=8, 10, 15, 20) denoted as ATS glasses are prepared by sol-gel method. The spectroscopic properties of the bulk glasses are investigated. The maximum emission cross section and measured fluorescence lifetime at 1811 nm are 6.39×10-21 cm2 and 645 μs, respectively. The lowest OH content is 10.5×10-6. The fiber preform was prepared by rod-in-tube method. The glass with composition 0.3Tm2O3-4.5Al2O3-95.2SiO2 is used as fiber core; the inner cladding is pure silica glass with an octagonal shape; and the outer cladding is ultraviolet curing layer. Laser properties of the fiber are investigated. The maximum laser output power reaches 1.23 W from a 66-cm-long fiber and the slope efficiency is 11.7%. The lasing threshold is 6.07 W and the lasing wavelength is centered at 1952 nm..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 8, 806003 (2013)
Characteristics of Dual-Wavelength Emission and Mode Competition in Two-Dimensional Random Medium
Fan Ting, and Li Na
The characteristics of dual-color emission and mode competition in two-dimensional random medium are studied. Based on the time-dependent theory, a model for dual-wavelength random laser is established. The Maxwell equations and rate equations are combined and solved by using the finite different time domain (FDTD) metThe characteristics of dual-color emission and mode competition in two-dimensional random medium are studied. Based on the time-dependent theory, a model for dual-wavelength random laser is established. The Maxwell equations and rate equations are combined and solved by using the finite different time domain (FDTD) method. Light emission spectrum is calculated by Fourier transform. The effects of dye concentration, surface filling-fraction and scatterer radius on random laser emission are discussed. Results show that the emission intensity of long wavelength increases while that of short wavelength decreases with the dye concentration raising . The surface filling-fraction increase the emission intensity and has the same effect on different wavelengths, while the effect of the scatterer radius on the emission spectrum is wavelength dependent..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 8, 806004 (2013)
Effect of Added Potassium Salt on Preparation of Potassium Niobate by Hydrothermal Processing
Cao Bo, Yu Jie, Yu Bin, Zhang Xinpeng, You Cheng, Chen Junwen, and Cao Huiqun
The potassium niobate (KNbO3) is prepared with niobium oxide (Nb2O5) and potassium hydroxide (KOH) as source material by hydrothermal method, which adds different kinds of potassium salt, for example, KCL, K2SO4, K2CO3, KBr. The influence of different potassiums on crystal texture, microstructure, output and fluorescenThe potassium niobate (KNbO3) is prepared with niobium oxide (Nb2O5) and potassium hydroxide (KOH) as source material by hydrothermal method, which adds different kinds of potassium salt, for example, KCL, K2SO4, K2CO3, KBr. The influence of different potassiums on crystal texture, microstructure, output and fluorescence of the complex KNbO3 is studied by X-ray diffraction (XRD), Raman spectrum, scanning electron microscope (SEM), infrared spectroscopy (FTIR) and fluorescence spectra (PL). Results show that the productivity is improved greatly by the adding of potassium salt. The kind of potassium salt is a critical factor for the structure and morphological profile of the KNbO3. When the added potassium salt is KCl or KBr, the well crystallized KNbO3 rods whose structures are rhombohedral and ortho rhombic form respectively are formed with the width of 0.5～1 μm and the length of 1～10 μm. Using K2CO3 or K2SO4 as the added potassium salt, the formed KNbO3 crystals whose structure are rhombohedral and ortho rhombic form respectively are irregular granular structures instead of rod-like structures. FTIR results indicate that the crystal show Nb＝O and Nb－O－Nb vibration peaks at 1383, 1087, 1050, 879, 614 cm-1. The fluorescence emissions of the KNbO3 samples are detected to appear the characteristic peaks at the wavelengths of 396, 450, 467,481, 491 nm..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 8, 806005 (2013)
Measurement and Metrology
Error Analysis on Measurement of Photoelectrical Encoder Corner Precision
Zhang Guilin, Jiang Tao, and Li Min
According to the detection accuracy of the high precision photoelectric encoder corner , a photoelectrical encoder corner precision measurement method based on dual-frequency laser interferometer is proposed. This device is driven by stepping motor. Through the reduction mechanism, the inspection encoder and the angle According to the detection accuracy of the high precision photoelectric encoder corner , a photoelectrical encoder corner precision measurement method based on dual-frequency laser interferometer is proposed. This device is driven by stepping motor. Through the reduction mechanism, the inspection encoder and the angle reference can be rotated. By using the Renishaw dual-frequency laser interferometer as the angle benchmark testing instruments and Renishaw RX10 rotors calibration module as large angle rotation reference, precision of 1.36″ is obtained. Traditional manual device and the proposed device in a 21 bit absolute encoder are used respectively for precision testing. The results show that the device is feasible, and that the test efficiency and precision are higher than those of the traditional detection device..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 8, 808001 (2013)
RANSAC-SVM Based Online Inspection Technique for Optics Damage in Intertial Confinement Fusion System
Feng Bo, Chen Fengdong, Liu Bingguo, Peng Zhitao, Liu Nan, Liu Guodong, and Sun Heyi
A high precision method, based on random sampling consensus (RANSAC) and least squares support vector machine (LSSVM) regression, is advanced to improve the inspection for inertial confinement fusion (ICF) optics damage. In present study, the measurement precision of damaged areas is improved significantly, via analyziA high precision method, based on random sampling consensus (RANSAC) and least squares support vector machine (LSSVM) regression, is advanced to improve the inspection for inertial confinement fusion (ICF) optics damage. In present study, the measurement precision of damaged areas is improved significantly, via analyzing the regression model of grey value and size. RANSAC is adopted for optimizing the training samples to avoid the effect of outliers. In addition, special experiment is proceeded to assess the effect of sample size on the measurement precision and the efficiency, and the appropriate interval of sample size is obtained as well. RANSAC-LSSVM can get optimal regression models which is adopted in different evaluative systems, by using different error evaluation functions. The results show that RANSAC-LSSVM reduces the mean relative error by 90% approximately, in measuring of damaged areas, compared with traditional pixel-level detection..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 8, 808002 (2013)
Impact of Rough Surface Scattering Characteristics to Measurement Accuracy of Laser Displacement Sensor Based on Position Sensitive Detector
Chen Hao, Zhu Jigui, and Xue Bin
The measurement of laser displacement sensor is based on the scattering effect of the surface, and the roughness characteristics of the target surface directly affects the light intensity of the scattering measurement spot. For the purpose of studying the impact of the roughened surface on the light intensity of the imThe measurement of laser displacement sensor is based on the scattering effect of the surface, and the roughness characteristics of the target surface directly affects the light intensity of the scattering measurement spot. For the purpose of studying the impact of the roughened surface on the light intensity of the imaging spot, the scattering geometry model of rough surface is built. By using Kirchhoff scalar scattering analytical theory and combining shadowing function statistical model, the functional relationship between the characteristic of the rough surface and the scattering luminous flux is calculated. According to the detection principle of the position sensitive detector (PSD) in the sensor, the light intensity value of imaging spot on the photosensitive surface will directly affect the measurement accuracy of the sensor. Through the analysis of the measurement data of different standard roughness surfaces which are got from the displacement sensor based on PSD, the experimental results show that different surface roughnesses will produce different measurement errors, and when the Rq value of surface roughness is larger, the light intensity of scattering spot becomes larger. But accompanied by significant enhancement of the shadowing coefficient, the light intensity is gradually weakened, and the magnitude of measuring error has the same trend of changes with that of light intensity. For the roughened surface with Rq=0.8 μm the measurement error is the minimum..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 8, 808003 (2013)
Dynamic Errors Analysis of Small Absolute Photoelectric Encoder
Yu Hai, Wan Qiuhua, Wang Shujie, Zhao Changhai, and Lu Xinran
Photoelectric encoder has static and dynamic characteristics. The analysis of photoelectric encoder′s errors is limited in static characteristics. In order to make the photoelectric encoder dynamic characteristics perfection, the dynamic errors of small absolute photoelectric encoder from bearing rocking, range-frequenPhotoelectric encoder has static and dynamic characteristics. The analysis of photoelectric encoder′s errors is limited in static characteristics. In order to make the photoelectric encoder dynamic characteristics perfection, the dynamic errors of small absolute photoelectric encoder from bearing rocking, range-frequency respond, data handling delay and so on are researched. By analysising the relationship between angle speed and dynamic errors, the regular pattern of dynamic errors and angle speed are obtained. Analysis results show that the dynamic error of an encoder which h code carves are composed by 1, h and constant products. By the changing of speed, the range of these component products also change. Thereby the characteristics of the encoder are affected. The research results can be applied to the analysising and controlling of photoelectric encoder′s dynamic characteristics, as well as providing theory for the improvement of photoelectric encoder′s dynamic characteristics..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 8, 808004 (2013)
Optical Communication
Large Side-Hole Microstructured Optical Fiber Grating with High Inscription Efficiency
Ren Xiaomin, Li Xiao, Wang Zhibin, and Wang Guanjun
Aiming at the problem of the high grating inscription scattering of previous microstructured optical fiber, inscription characteristics of a large side-hole microstructured optical fiber grating are analyzed by finite-difference time-domain method and the amalysis result is confirmed by finite element method. The largeAiming at the problem of the high grating inscription scattering of previous microstructured optical fiber, inscription characteristics of a large side-hole microstructured optical fiber grating are analyzed by finite-difference time-domain method and the amalysis result is confirmed by finite element method. The large hole can be filled with fluid of suitable refractive index, the fluid-filled hole acting as a converging lens and the inscribing Gauss beam can focus into the core region, which improves grating inscription efficiency. The simulation results show that the inscription efficiency of the modified structure is 290% of conventional array hole photonic crystal fiber grating and 210% of single model fiber grating, respectively. An ultrahigh inscription efficiency and a relative less grating inscription scattering can be achieved, while the influence of inscription angle deviation is also discussed..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 8, 805001 (2013)
Research and Fabrication of a Ultraviolet Curable Polymeric Arrayed Waveguide Grating with Nonlinear Cladding
Wang Lei, Li Ran, Niu Xiaoyan, Wang Fei, Sun Xiaoqiang, Chen Changming, and Zhang Daming
A compact 41×41 arrayed waveguide grating (AWG) device with double active layers is fabricated by using SU-8 minus negative core whose type is ultraviolet (UV) light-sensitive type and organic-inorganic hybrid material cladding. A rectangular waveguide structure is selected in the calculation of AWG and the singleA compact 41×41 arrayed waveguide grating (AWG) device with double active layers is fabricated by using SU-8 minus negative core whose type is ultraviolet (UV) light-sensitive type and organic-inorganic hybrid material cladding. A rectangular waveguide structure is selected in the calculation of AWG and the single mode can be achieved with cladding thickness of 5 μm and the core cross sectional area of 4 μm×4 μm. For the AWG device, the channel space is set as 0.8 nm with the central wavelength of 1550 nm. After testing, the transmission loss is 1.2 dB/cm, the diffraction loss of the central channel is 6.2 dB, the tested channel space is 0.793 nm and the central wavelength shift is -0.08 nm/℃..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 8, 805002 (2013)
Optical High-Power Millimeter-Wave Generated by Multiple-Sidebands
Han Yishi, Zheng Zhenyu, and Guo Fangwei
A method about multiple-sidebands beat is studied to produce a series of high-power millimeter-wave, and interleaver module is proposed. For the module without additional optical filter and complex circuit driver, periodical sideband signals generated by parameters setting are tunable. Theoretical analysis demonstratesA method about multiple-sidebands beat is studied to produce a series of high-power millimeter-wave, and interleaver module is proposed. For the module without additional optical filter and complex circuit driver, periodical sideband signals generated by parameters setting are tunable. Theoretical analysis demonstrates that multiple-sidebands beat with each other, the millimeter wave signal is formed by superposition ultimately, the signal energy is more concentrated, and the frequency is tunable. Simulation results indicate that multiple-sidebands modulation method can generate 12-tupling, 16-tupling, even 18-tupling millimeter waves, and output signals reflect high power characteristics obviously. In comparison with typical bi-sideband modulation method, the power of millimeter wave signal is improved by more than 20 dB. According to the results of the system simulation, the proposed radio-over-fiber (RoF) system has better performance on transmission and anti-dispersion, and it is more suitable for long-distance transmission..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 8, 805003 (2013)
Optical Design and Fabrication
Computer Controlled Ultra-Smooth Polishing High Order Rotary Symmetrical Aspheric Lens
Liu Jian, Wang Shaozhi, Zhang Linghua, and Wang Junlin
In order to realize full aperture ultra-smooth polishing on the high order rotary symmetrical aspheric surface, the polishing head controlling algorithm is studied. The basic theory of ultra-smooth polishing technology and the computer numerical control machine mechanism are introduced. And the optical surface generatiIn order to realize full aperture ultra-smooth polishing on the high order rotary symmetrical aspheric surface, the polishing head controlling algorithm is studied. The basic theory of ultra-smooth polishing technology and the computer numerical control machine mechanism are introduced. And the optical surface generating method is also descripted. Then, a kind of equal error recurrence algorithm is proposed which is used in solving dwell points and controlling polishing head path. And the path error is also analyzed. The polishing removal rate distribution of different positions is calculated and the dwell time mathematical solving model is established. Finally, an experiment for polishing an aspheric lens with a aperture of 150 mm and a asphericity of 116 μm is carried out on the self-research machine. The root-mean-square of surface roughness is reduced from 1.523±0.045 nm to 0.399±0.0238 nm. The result indicates that the algorithm described in this paper could improve the precision of asphere polishing path and the uniformity of the roughness distribution..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 8, 816001 (2013)
Remote Sensing and Sensors
Experimental Research on Small Scale Risley Prism Scanning Imaging Laser Radar System
Zhang Yong, Cao Xibin, Wu Long, Zhang Sicheng, and Zhao Yuan
Laser radar development tends to focus on array imaging laser radars. Due to the restriction of array detectors and laser power, it is hard to realize imaging with high resolution in distant range. Risley prism scanning imaging laser radars based on small scale array, possessing both the advantages of high resolution iLaser radar development tends to focus on array imaging laser radars. Due to the restriction of array detectors and laser power, it is hard to realize imaging with high resolution in distant range. Risley prism scanning imaging laser radars based on small scale array, possessing both the advantages of high resolution in array imaging laser radar and imaging in distance in scanning laser radar, have drawn much attention in laser radar researches. A small scale array Risley prism scanning imaging laser radar system is constructed with a high frequency solid laser transmitter and a double optical prism scanner for theoretical experiments. The system adopts a 5×5 array detector as the sensitive unit and designs a 25-channel parallel amplifier. The bandwidth of 200 MHz and 40 dB gain are achieved with the plastic circuit output signal jitter being less than 2 ns. The frequency of the 25-channel array timer achieves 200 MHz. These realize the small plane array block scanning laser radar principle experiment system. With the system, an indoor imaging experiment is presented. The results show that the ranging accuracy of the system reaches 0.8 m with a 3°×3° viewing angle and a 128 pixel×128 pixel image resolution. It analyzes the factors to influence the accuracy of block scanning imaging laser radar system according to the experimental results. The results show that the beams pointing accuracy, the bandwidth and timing accuracy of the scanner probes and processing circuit have the primary impacts on restriction of distant imaging quality..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 8, 814001 (2013)
Application of Mechanical Chopper in Atmospheric Lidar
Lin Xin, Yang Yong, Cheng Xuewu, Guan Sai, Wang Jihong, Li Faquan, Liu Linmei, Song Shalei, Chen Zhenwei, and Li Yajuan
High power pulse laser and large aperture telescope are usually used for getting signals from higher altitude in lidar observation, which brings the detector saturation caused by strong backscattering from low altitude. The mechanical chopper improves the lidar performance by cutting off the low altitude noise in opticHigh power pulse laser and large aperture telescope are usually used for getting signals from higher altitude in lidar observation, which brings the detector saturation caused by strong backscattering from low altitude. The mechanical chopper improves the lidar performance by cutting off the low altitude noise in optical method and passing the backscattering signals from higher. The working principle of the mechanical chopper is analyzed, and the chopper unit is built up. The testing data are agreed well with the theoretical results. The application of the chopper in lidar detection system can solve the problems of detector saturation and blinding caused by low altitude backscattering, so as to increase the detection range and the measuring accuracy..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 8, 814002 (2013)
Target Recognition of Coherent Ladar Range Image Using Feature Selection
Liu Zhengjun, Li Qi, and Wang Qi
Coherent ladar range image is closely relative to physical structure property of object′s surface, and reflects essential characteristics of objects, thus it has received considerable attention in object recognition fields. Generally, it is difficult to collect a mass of range images for ladar in real application. HoweCoherent ladar range image is closely relative to physical structure property of object′s surface, and reflects essential characteristics of objects, thus it has received considerable attention in object recognition fields. Generally, it is difficult to collect a mass of range images for ladar in real application. However, under small-sample case, when the number of features increases, the recognition rate will decrease, which is called Hughes effect. In this paper, the two methods of feature selection, i. e., relief and support vector machine recursive feature elimination (SVM-RFE) are applied to solve the problem. The experimental results demonstrate that the methods of Relief and SVM-RFE are able to relieve Hughes effect that is caused by three combined moments [affine moments (AMs) and Zernike moments (ZMs), ZMs and Hu moments (HMs), and AMs, HMs and ZMs]. Moreover, the recognition rate of SVM-RFE is slightly better than that of Relief..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 8, 814003 (2013)
Spectroscopy
Quantitative Analysis of Fenitrothion Based on Surface-Enhanced Raman Spectroscopy
Weng Shizhuang, Zheng Shouguo, Li Pan, Chen Sheng, Zeng Xinhua, Li Miao, and Zheng Xiaoju
Principal component analysis (PCA), partial least squares (PLS) regression and surface-enhanced Raman spectroscopy (SERS) are used in quantitative analysis of the concentration of fenitrothion solution. 600~1800 cm-1 SERS spectra of the fenitrothion solution are measured. The spectra around characteristic peaks are prePrincipal component analysis (PCA), partial least squares (PLS) regression and surface-enhanced Raman spectroscopy (SERS) are used in quantitative analysis of the concentration of fenitrothion solution. 600~1800 cm-1 SERS spectra of the fenitrothion solution are measured. The spectra around characteristic peaks are preprocessed by the absolute value of the first derivative, the multiplicative scatter correction (MSC) and the standard normal transformation respectively. Models are built by PCA and PLS regression. Grouping alternating method is used to validate the performance of models. It is found that the model built with the MSC preprocessed spectra performs better. The accuracy of analysis meets the detecting requirement of fenitrothion..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 8, 815001 (2013)
Oxygen ‘A’ Absorption Band Simulation of Infrared Distance Inversion Algorithm and Experimental Research
Wang Zhibin, Zong Pengfei, and Li Xiao
Realization of passive ranging based on infrared radiation and atmospheric attenuation characteristics is closely related to gas band selection. Oxygen A absorption band has a unique spectral structure. For rocket plume and high temperature radiation, the band is the best inversion channel of distance. Through the in-dRealization of passive ranging based on infrared radiation and atmospheric attenuation characteristics is closely related to gas band selection. Oxygen A absorption band has a unique spectral structure. For rocket plume and high temperature radiation, the band is the best inversion channel of distance. Through the in-depth research of line-by-line radiative transfer model (LBLTRM), Oxygen A band standard spectrum calculation software is designed. Making use of the out-of-band data, band average transmittance in different distances is obtained by polynomial fitting, and then the corresponding distance is received. Putting the ABB lamp as the light source, collecting the corresponding spectrum in different distances and making the fitting calculation, through the comparison of fitting results of the measured datas and theoretical calculation results, the error is within 0.5% and is in the permissible range..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 8, 815002 (2013)
Pre-Ablation Laser Parameters Effect on the Spectral Enhancement of Double Pulsed Laser Induced Breakdown Spectroscopy
Gao Xun, Shao Yan, Du Chuang, Zhao Zhenming, Zheng Quan, and Lin Jingquan
Effect of pre-ablation laser parameters on the spectral enhancement of 532 nm/1064 nm orthogonal pre-ablation dual-pulse laser induced breakdown spectroscopy (DP-LIBS) is analyzed by the spectral intensity variation of Cr I 520.8 nm and Fe I 522.7 nm for the alloy steel, and the experimental conditions are optimized. TEffect of pre-ablation laser parameters on the spectral enhancement of 532 nm/1064 nm orthogonal pre-ablation dual-pulse laser induced breakdown spectroscopy (DP-LIBS) is analyzed by the spectral intensity variation of Cr I 520.8 nm and Fe I 522.7 nm for the alloy steel, and the experimental conditions are optimized. The experimental results show that DP-LIBS has a maximum spectral enhancement at the conditions of the pre-ablation pulse energy of 70 mJ, the main ablative pulse energy of 100 mJ, the distance of focus point of the pre-ablation pulse to the sample surface of 1 mm and to the main ablation pulse light path of 1 mm respectively. The spectral enhancement of Cr I 520.8 nm is 12.5 at interpulse delay time 30 μs, then decreases rapidly. Finally, the spectra enhancement mechanism of orthogonal pre-ablation DP-LIBS is analyzed..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 8, 815003 (2013)
© Copyright 2018-2021 | Chinese Laser Press. All Rights Reserved 沪ICP备15018463号-20